SGLT2 inhibitors in real-world patients with heart failure with preserved ejection fraction

Introduction

The diagnosis and management of heart failure with preserved ejection fraction (HFpEF) is challenging since ejection fraction is normal, clinical signs are often lacking and there are few therapeutic options. Two randomized clinical trials have tested SGLT2i for the treatment of HFpEF: DELIVER (pending results) and EMPEROR-PRESERVED; the findings of the latter trial show that empagliflozin, a sodium-glucose cotransporter inhibitor (SGLT2i) reduces the risk of cardiovascular death or hospitalization for HF in patients with HFpEF regardless the presence of diabetes. The results of this clinical trial have allowed European Medicine Agency (EMA) to extend the indication also to the patients with HFpEF, however the characteristics of the trial population don't often correspond to real-word HF population.

Aims

This study aims to investigate the eligibility of the EMPEROR-PRESERVED and DELIVER trial to a real-world heart failure population comparing the baseline characteristics of our patients to the recruited patients of clinical trials.

Material and methods

In this retrospective, observational study, 206 HF outpatients were enrolled from September 2018 to September 2019. The percentages of eligible patients according to EMPEROR PRESERVED and DELIVER inclusion criteria were analyzed, then we analyzed the difference between the characteristics of our HFpEF population and trials population.

Results

72 patients (35% of HF population) had heart failure with preserved ejection fraction. The EMPEROR-PRESERVED criteria and DELIVER trial were applied to these patients: 13 (18.1%) and 12 (16.7%) patients respectively fulfilled all enrolment criteria, whereas considering only EMA label criteria (EF >40% and eGFR >20 ml/min) 71 patients (98.6%) were eligible. The eligible patients according EMA criteria were significantly younger (67.3±14.3) than EMPEROR-PRESERVED population (72±9, p<0.001) and DELIVER population (72±10, p<0.001). The ejection fraction was significantly lower (50.2±5.8 vs 54±8.8; p<0.001) whereas eGFR was no significantly different (64.4±22.7 vs 60.6±19.8; p=0.17).

Conclusion

Only a small percentage of our heart failure with preserved ejection fraction population was eligible for SGLT2 inhibitors according trials criteria, whereas according to EMA label almost all patients are candidate to these drugs. Furthermore, these patients were younger than EMPEROR-PRESERVED and DELIVER population with lower EF. The difference of eligibility between trials and real population is related to inclusion criteria, in particular the trial patients had elevated NT-proBNP levels whereas in the real world this criterion isn't considered. There is a lack of data about real-world patients who are often different from trials population. National and international registries of HF population may resolve this issue.

Funding Acknowledgement

Type of funding sources: None.

P240 SHORT–TERM EFFECT OF SGLT2I ON ECHOCARDIOGRAPHIC PARAMETERS IN HFREF PATIENTS TREATED WITH ARNI

Background

Treatment with Sacubitril / Valsartan (ARNI) in patients with heart failure and reduced ejection fraction (HFrEF) promotes significant improvement of left ventricular remodeling along with positive outcomes in terms of hospitalization for heart failure, quality of life and mortality. In a previous study we demonstrated that ARNI significantly modifies myocardial longitudinal strain (GLS), one of the most reliable markers of myocardial contractility. It is still debated whether this effect remains unchanged regardless of the presence of diabetes and if it can be further increased by SGLT2 inhibitors, which in turn have been shown to reduce hospitalizations for heart failure and cardiovascular mortality.

Purpose

of this ongoing study is to measure, in HFrEF patients with or without T2DM, treated with ARNI and SGLT2i, short–term changes (6 months follow up) of the main echocardiographic parameters, including GLS Methods We enrolled 40 outpatients (32 male, age 65 + 10 years, EF 29,7 + 6,5%) on optimized medical treatment with class I medications, including ARNI at the maximum tolerated dose (starting dose 75 + 15mg, maximum titrated dose 190 + 10mg). Population was then divided into three groups: group 1 (20 pts) without T2DM; group 2 (11 pts) with T2DMI; group 3 (9 pts) with T2DM on SGLT2i treatment (4 with empaglifozin 10 mg, 5 with dapaglifozin 10 mg). No hemodynamic or metabolic complications related with therapy were observed, and no patients needed discontinuation or down–titration of therapy All patient underwent echocardiographic study at baseline and after six–month follow–up.

Conclusions

This ongoing study confirms that, in HFrEF patients, ARNI positively modifies left ventricular contraction and remodeling, and this effect is still verified regardless of the presence of T2DM. The association with SGLT2i, conversely, does not appear to provide further positive benefits on remodeling.

Predictors of one year all-cause death in acute heart failure patients enrolled in the nationwide BLITZ-HF study

Background

Outcomes of patients admitted for acute heart failure (AHF) are generally poor, then it is important to recognize outcome predictors in order to better identify and manage patients at higher risk.

Aims

To identify independent predictors of 1-year all-cause death in AHF patients enrolled by Italian cardiology sites participating to the BLITZ-HF study.

Methods

BLITZ-HF was a prospective nationwide study based on a web based recording system used during two enrollment periods (08/03/2017 – 04/09/2017 and 24/12/2017 – 09/04/2018). Overall, 7218 patients with acute and chronic HF were enrolled by 106 sites, 58 were lost to follow-up. Patients were followed for a median of 370 days [IQR 339–395]. Cox proportional hazards models were used to identify the independent predictors of all-cause death from hospital admission to 1-year follow-up. Demographic variables and baseline characteristics statistically significant at univariate analysis were included in the multivariable models. Different Cox proportional models were fitted: 1) adjusted for age and gender, 2) model 1 + clinical variables, 3) model 2 + laboratory and instrumental examinations, 4) model 3 + therapy.

Results

The present analysis refers to the 1470 patients admitted for AHF not lost to follow-up. Mean age was 73±12, with nearly 50% having more than 75 years of age. Female gender accounted for about one third of cases. More than half were de novo HF patients and 43% had an ischemic aetiology. Nearly 40% had a history of atrial fibrillation (AF) and chronic kidney disease (CKD) and one fifth had a history of COPD and peripheral obstructive artery disease. Furthermore, mean systolic blood pressure (SBP) on admission was 131±28 and, heart rate (HR) was 91±25. The majority of HF patients had reduced EF (HFrEF) (58%), followed by HF with preserved EF (HFpEF) (24%) and HF with mid range EF (HFmrEF) (18%).

One year all-cause mortality was 16.6%. Independent predictors of all-cause mortality are shown in the Table. In the final model adjusted for age, gender, clinical variables, laboratory and instrumental examinations and medical treatments, the following variables resulted as independent predictors of one-year all-cause mortality: age (HR 1.02), Confuse/obnubilate mental status (HR 2.07), creatinine >1.5 mg/dl (HR 1.54), BUN >43 mg/dl, (HR 2.74), aortic stenosis (HR 1.70), inotrope use (HR 1.43), IV furosemide >125 mg (HR 1.74), SBP (HR 0.99).

Conclusions

In our study several independent predictors of one-year all-cause mortality have been identified, confirming and reinforcing previous findings. Interestingly, our independent predictors derived from different domains (demographic, clinical, biohumoral, instrumental and treatment variables). These findings further underline the importance of a comprehensive assessment in the prognostic evaluation of AHF patients.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The study was funded by Heart Care Foundation with a partial unrestricted support from Abbott, Daiichi Sankyo, Medtronic, Servier, Vifor.

Clinical characteristics, management and outcomes in patients with new onset or worsening acute heart failure enrolled in the nationwide BLITZ-HF study

Background

Real world observational clinical data is important to better characterize heterogeneous groups of patients, such those with acute heart failure (AHF), in order to phenotype patients with different prognosis and to generate hypotheses regarding management in clinical practice or patient selection for planning randomised clinical trials.

Aims

To describe clinical characteristics, management and outcomes of acute heart failure (AHF) patients admitted for a first HF episode (de novo) or for worsening chronic HF (WHF) and enrolled by Italian cardiology sites participating to the nationwide BLITZ-HF study.

Methods

BLITZ-HF was a prospective nationwide study based on a web-based recording system used during two enrollment periods (08/03/2017 – 04/09/2017 and 24/12/2017 – 09/04/2018). Overall, 7218 patients with acute and chronic HF were enrolled by 106 sites.

Results

The present analysis refers to the 1470 out of 1494 patients admitted for AHF not lost to follow-up, of which 822 (56%) presented with de novo and 648 (44%) with WHF. Patients were followed for a median of 370 days [IQR 339–395]. Mean age was significantly higher in patients with WHF 74±12 (vs 72±12 in de novo, p<0.001), while no gender differences were observed (WHF 35% vs de novo 36%). Compared to de novo, patients with WHF had more frequently a history of treated hypertension (66% vs 61%, p=0.028), atrial fibrillation (52% vs 29%, p<0.0001), previous myocardial infarction and coronary revascularization (41% vs 19% and 38% vs 18% respectively, both p<0.0001), a previous device implantation (34% vs 6%, p<0.0001). Non cardiac comorbidities such as CKD and COPD resulted in a higher rate among patients with WHF (51% vs 28% and 26% vs 17%, both p<0.0001). We also found significant differences between the two groups in terms HF ejection fraction categories (HFrEF 64.5% vs 52.3%, HFmrEF 13.9% vs 21.4%, HFpEF 21.6% vs 26.3%, for WHF vs de novo, p<0.0001). On admission, patients with WHF presented with lower systolic blood pressure (124±27 vs 135±28, p<0.0001), lower hart rate (87±23 vs 95±26, p<0.0001), higher creatinine levels (1.5±0.7 vs 1.3±0.8, p<0.0001). Both inotropes and high dose of IV furosemide (>150 mg) were more frequently used among WHF patients (22.8% vs 9.7% and 35.7% vs 19.7%, p<0.0001).

Figure and table show Kaplan-Meyer curves for one year all-cause mortality and detailed in-hospital and one-year outcomes regarding mortality (total and CV) and hospitalizations (all, CV and HF) as well as the combined outcome of HF hospitalization and all-cause mortality. Patients with WHF had significantly worse outcomes compared to those with de novo HF.

Conclusions

In our study we confirm the heterogeneity of AHF patients and the importance of identify and characterize different subgroups. Patients with WHF have a more severe clinical profile and worse in-hospital and one-year clinical outcomes.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The study was funded by Heart Care Foundation with a partial unrestricted support from Abbott, Daiichi Sankyo, Medtronic, Servier, Vifor.

BLITZ-HF study: a nationwide initiative to assess and improve guidelines recommendations adherence in cardiology centers managing patients with acute and chronic heart failure

Background

Physicians adherence to heart failure (HF) guidelines is generally sub-optimal with consequent negative prognostic implications. Strategies to improve adherence to guideline recommendations are strongly needed.

Aims

To assess and improve adherence of Italian cardiology sites to guidelines recommendations on performance indicators in patients with acute (AHF) and chronic heart failure (CHF).

Methods

BLITZ-HF was a prospective study based on a web based recording system used during two enrollment periods (phase 1 and 3), interspersed by face-to-face macro-regional benchmark analysis and educational meetings (phase 2). Both management (creatinine and echocardiographic evaluations or discharge follow-up planning) and treatment (according to ejection fraction categories, focusing on guidelines directed medical treatments - GDMTs) performance indicators were considered for patients in both settings.

Results

Overall, 7218 patients with acute and chronic HF were enrolled at 106 sites. During the enrollment phases, 3920 and 3298 patients were included respectively, 84% with CHF and 16% with AHF in phase 1, 74% with CHF and 26% with AHF in phase 3. In Figure 1 we report adherence to management and treatment indicators in the two enrollment phases. Among AHF patients improvement was obtained in two of seven indicators. A significant rise in echocardiographic evaluation was observed, while discharge schedule of a cardiology ambulatory evaluation within four weeks was overall poor (less than 50%) and did not improve in the 3 phase. Overall GDMTs prescription rate in HFrEF was good and we observed a nominal increase in betablockers prescription rate in Phase 3. Among CHF patients with HFpEF and HFmrEF we observed a performance increase in two of three indicators: creatinine end echocardiographic evaluations, while oral anticoagulation in atrial fibrillation remained stably high. Performance measures in CHF HFrEF patients improved in six of nine indicators although significantly only in two. Prescription rate of GDMTs was good already in phase 1 and a significant increase in ACE-I/ARB or ARNI prescription was reported, with a nominal increase in the use of one of these three drugs in combination with MRAs and a BB.

Conclusions

A structured multifaceted educational intervention can improve adherence to HF guidelines on several indicators in a context of an already elevated level of adherence to guideline recommendations. Extension of this approach to other non-cardiology health professional settings, in which patients with HF are generally managed, should be considered.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The study was funded by Heart Care Foundation with a partial unrestricted support from Abbott, Daiichi Sankyo, Medtronic, Servier, Vifor.

Impact of diabetes on COVID-19-related in-hospital mortality: a retrospective study from Northern Italy

PURPOSE

The purpose of this study was to evaluate the impact of pre-existing diabetes on in-hospital mortality in patients admitted for Coronavirus Disease 2019 (COVID-19).

METHODS

This is a single center, retrospective study conducted at Policlinico di Monza hospital, located in the Lombardy region, Northern Italy. We reviewed medical records of 373 consecutive adult patients who were hospitalized with COVID-19 between February 22 and May 15, 2020. Data were collected on diabetes status, comorbid conditions and laboratory findings. Multivariable logistic regression was performed to evaluate the effect of diabetes on in-hospital mortality after adjustment for potential confounding variables.

RESULTS

Mean age of the patients was 72 ± 14 years (range 17-98), 244 (65.4%) were male and 69 (18.5%) had diabetes. The most common comorbid conditions were hypertension (237 [64.8%]), cardiovascular disease (140 [37.7%]) and malignant neoplasms (50 [13.6%]). In-hospital death occurred in 142 (38.0%) patients. In the multivariable model older age (Relative Risk [RR] 1.06 [1.04-1. 09] per year), diabetes (RR 1.56 [1.05-2.02]), chronic obstructive pulmonary disease (RR 1.82 [1.13-2.35]), higher values of lactic dehydrogenase and C-reactive protein were independently associated with in-hospital mortality.

CONCLUSION

In this retrospective single-center study, diabetes was independently associated with a higher in-hospital mortality. More intensive surveillance of patients with this condition is to be warranted.

Systematic cutting of selected secondary mitral valve chordae, in association with a shallow myectomy, in obstructive hypertrophic cardiomyopathy:impact on mitral valve function and patient management

Introduction

Few centers worldwide have large experience with performing an extended septal myectomy in patients with obstructive hypertrophic cardiomyopathy (HCM). Therefore, many HCM patients eligible for surgical relief of left ventricular (LV) outflow gradient do not have access to treatment. In a previous study, cutting fibrotic anterior mitral leaflet secondary chordae, in association with only a shallow myectomy, proved highly effective in moving the mitral valve (MV) apparatus away from the LV outflow tract and relieving the outflow gradient in our HCM patients with mild hypertrophy (<19 mm), a surgical approach that simplifies the operation.

Purpose

To assess whether chordal cutting is equally effective in improving MV geometry and relieving LV outflow gradient and heart failure symptoms in HCM patients with more marked hypertrophy.

Methods

Surgical outcome and MV geometry and function were assessed in 226 consecutive HCM patients who underwent systematic cutting of fibrotic anterior mitral leaflet secondary chordae, in association with a shallow myectomy and independently of magnitude of septal thickness, at our center from January 2015 to December 2018.

Results

Of 226 study patients, 1 (0.4%) died perioperatively. None had iatrogenic septal defect. Postoperatively, LV outflow gradient at rest decreased from 70±36 to 10±2 mmHg (P<0.001). In the 77 patients in whom data on the outflow gradient provoked with physiologic maneuvers after surgery were available, the provocable gradient was 16±10 mmHg. NYHA functional class improved significantly (P<0.001), with the number of patients in class III-IV decreasing from 178 (79%) to 2 (0.9%). No patient had residual severe MV regurgitation and only 4 (1.7%) had moderate-to-severe regurgitation. Quality of the echocardiogram allowed assessment of MV geometry in 212 (94%) patients. In the 62 patients with mild hypertrophy, anterior leaflet-annulus ratio increased 27% postoperatively, from 0.43+0.06 to 0.55+0.06 and MV tenting area decreased 34% from 2.9+0.6 to 1.9+0.4 cm2 (P<0.001), indicating repositioning of MV coaptation away from the outflow tract (with increased outflow tract dimension). Similarly, in 150 patients with marked hypertrophy, anterior leaflet-annulus ratio increased 27% from 0.43+0.05 to 0.55+0.06 and tenting area decreased 28% from 2.9+0.6 to 2.1+0.4 cm2 (P<0.001).

Conclusions

Our results show that cutting fibrotic anterior mitral leaflet secondary chordae, by moving the MV apparatus away from the LV outflow tract and independently of the magnitude of septal hypertrophy, contributes to improve the results of septal myectomy and reduces the need for a deep septal excision (and associated risk of iatrogenic septal defect) in patients with obstructive HCM. Therefore, chordal cutting could make the myectomy operation more accessible to surgeons, increasing the availability of surgical treatment for HCM patients eligible for invasive abolition of LV outflow obstruction.

Funding Acknowledgement

Type of funding source: None

P320Heart failure with mid-range (HFmrEF) or recovered (HFrecEF) ejection fraction: differential determinants of transition

Background

Heart failure with mid-range ejection fraction (HFmrEF) has been identified as a multi-faceted phenotype that may encompass both patients with mild disease or those who from previous HFrEF recover EF (HFrecEF)

Purpose

To describe clinical characteristics and factors associated with phenotype transition at follow-up.

Methods

From 2009 to 2016, 1194 patients with baseline EF<50% and a second echocardiographic determination during clinically stability at a median of 6 months were enrolled in the IN-CHF Registry. Based on EF at enrollment, 335 (28%) had HFmrEF and 859 (72%) had HFrEF. We compared baseline clinical characteristics and predictors associated with follow-up reclassification to HFmrEF or full EF recovery

Results

When compared to HFrEF patients, those with HFmrEF had less often an ischemic etiology, advanced symptoms and a HF admission in the previous year. No other differences were found in clinical characteristics and drug therapy (Table).

At a median follow-up of 6 months, 30% of HFrEF patients improved EF by 14 (9) units: 21% showed partial EF recovery (transition to HFmrEF) and 9% had full EF recovery. Conversely among HFmrEF patients 22% improved EF, by 9 (5) units, to full recovery, and 18% deteriorated by 1.5 (5.5) units sloping to HFrEF.

By multivariable logistic regression analysis, variables associated with EF recovery at 6-month follow-up differed between baseline phenotypes. Within HFrEF, ischemic etiology (OR 0.46, 95% CI 0.33–0.64) and NYHA class III-IV symptoms (OR 0.57, 95% CI 0.38–0.68) were associated with a lower likelihood of EF recovery, while a history of HF<6 month correlated with a higher likelihood of EF recovery (OR 2.44, 95% CI 1.76–3.39). Within HFmrEF, while ischemic etiology (OR 0.66, 95% CI 0.19–0.68) was also associated with a lower likelihood of EF recovery, a history of atrial fibrillation at enrollment correlated with higher likelihood of EF recovery (OR 2.66, 95% CI 1.37–5.17) by 6 month-follow-up.

At a median follow-up of 36+28 months mortality was 4.6% vs 6.9% in HFrecEF vs non-recovered patients (log rank p=0.08).

Baseline characteristics HFrEF vs HFmrEF

Conclusions

HFmrEF patients showed a less severe clinical picture than HFrEF patients, but had EF recovery less often. EF improvement is negatively associated with ischemic etiology in both phenotypes, and positively associated with atrial fibrillation in HFmrEF and a short history of HF in HFrEF.

Long-term monitoring of sleep apnea at home in heart failure patients: preliminary results from the HHH study

Sleep apnea is very common in patients with chronic heart failure (CHF) and has important implications in terms of morbidity, mortality and clinical management. Home respiratory telemonitoring might constitute a potential low-cost, widely-applicable alternative to traditional polysomnography in the evaluation and long-term monitoring of breathing disorders in these patients. In this paper we briefly describe the technological infrastructure and present preliminary results of the European Community multicountry trial HHH (Home or Hospital in Heart Failure), which is currently testing a novel system for home telemonitoring of cardiorespiratory signals in CHF patients. The recording and transmitting devices are suitable to be self-managed by the patient. We give a detailed report on the prevalence of nocturnal respiratory disorders at the beginning of the one-year follow-up and on their persistency over the following recordings (one per month). These preliminary findings clearly indicate that intermittent home telemonitoring of respiratory signals based on patient's self-management is feasible in CHF patients and the compliance is high. Reported statistics unambiguously confirm the high prevalence of nocturnal breathing disorders in these patients and clearly show that this phenomenon tends to persist over time.

Prognostic implications of autonomic nervous system analysis in chronic heart failure: role of heart rate variability and baroreflex sensitivity

Increased sympathetic activity and plasma levels of norepinephrine (NE), parasympathetic withdrawal and impaired baroreflex gain have been reported in chronic heart failure (CHF). It is still debated whether, and if so, to what extent, the marked sympathetic activity influences the survival. Very little data is available on the prognostic implications of baroreflex sensitivity (BRS) and heart rate variability (HRV). Both BRS and HRV have been shown to be markedly reduced in CHF and significantly associated with the degree of ventricular dysfunction and with a further progression of the severity of the disease. Only small studies involving a limited number of patients have correlated these indices to an increased risk of death in CHF. We studied 119 consecutive sinus rhythm patients with mild to severe CHF. It was found that time and frequency parameters of HRV were not different between deceased and surviving patients, while BRS at univariate analysis was significantly associated with mortality; however, this prognostic information was not confirmed in a multivariate model. Although further analyses are necessary, our data and those of the literature do not confirm in CHF the important role which has been attributed to HRV and BRS in post-myocardial infarction risk stratification. In this paper some methodological limitations concerning the measure of these indices in CHF and possible different interpretative keys of the results are discussed to explain the discrepancies.

Orthopnea and inspiratory effort in chronic heart failure patients

STUDY OBJECTIVE

Orthopnea is a typical feature of patients with chronic heart failure (CHF), the factors contributing to it are not completely understood. We investigated changes in dyspnea and other respiratory variables, induced by altering posture (from sitting to supine) in 11 CHF patients (NYHA classes II-IV) and 10 control subjects.

METHODS AND RESULTS

We measured dyspnea (Borg scale) the diaphragm pressure time product per minute (PTPdi/m, index of metabolic consumption), and mechanical properties of the lung (lung compliance (C,L) and resistances (R,L). CHF patients also underwent a trial of non-invasive mechanical ventilation (NIMV) in the supine position in order to ascertain whether unloading the inspiratory muscles could somehow relieve dyspnea. While sitting the PTPdi/min was significantly higher in CHF patients than in controls (181 +/- 54 cm H2O x s/min vs. 96 +/- 32; P<0.05). Assuming a supine position caused no major changes in controls, whereas CHF patients showed a significant worsening in dyspnea, a rise in PTPdi/min (243 +/- 97 p<0.01) and R,L (4.7 +/- 1.2 cm H2O/L x s sitting vs. 7.9 +/- 2.5 supine; P<0.01) and a decrease in C,L (0.08 +/- 0.02 L/cm H2O sitting vs. 0.07 +/- 0.01 supine; P<0.05). Applying NIMV to supine CHF patients significantly reduced the PTPdi/min to 81 +/- 42 (P<0.001). Changes in dyspnea, produced by varying position or applying NIMV, were significantly correlated with PTPdi/min (r=0.80, P<0.005 and r=0.58, P<0.01, respectively).

CONCLUSIONS

CHF patients had a higher PTPdi/min than controls when sitting, and assuming a supine position induced severe dyspnea, a large rise in R,L, and a reduction in C,L so that PTPdi/min increased further. Orthopnea was strongly correlated with the increased diaphragmatic effort.

Left atrial function: bridge to central and hormonal determinants of exercise capacity in patients with chronic heart failure

The stroke volume response to exercise is a critical determinant in meeting peripheral metabolic demands in patients with chronic hear failure. The Left atrium, by its position, is important in coupling right and left ventricles, to left preload reserve and to modulate sympathetic activity. We performed this study to investigate the relationship between exercise capacity and diastolic and systolic left atrium function in patients with chronic heart failure.

METHODS

We considered 128 consecutive patients with severe chronic heart failure (EF < 35%) due to ischemic or idiopathic dilated cardiomyopathy. Cardiac output, right atrial pressure, pulmonary artery pressures and mean pulmonary wedge pressure (A, X, V, Y wedge pressures) were determined during right cardiac catheterization. By Echocardiography evaluation, we measured atrial pressures and volume during early and late left atrial systolic filling and we calculated left atrial chamber stiffness by this equation P = A*eKV1. (P = left atrial pressure; A = elastic constant (mmHg*ml); e = the base of the natural logarithm; V1 = left atrial volume (ml); K = left atrial chamber stiffness constant (ml-1) = ln (V/X)/(maximal--minimal left atrial volumes)). All patients performed cardiopulmonary exercise test with modified Noughton protocol. Plasma norepinephrine and Atrial natriuretic factor levels were determined.

RESULTS

Maximal and minimal left atrial volumes were inversely related to oxygen consumption (r = -.44, p < .001; r = -.61, p < .001). At rest, no differences were found in plasma norepinephrine concentrations (309 +/- 152 pg/ml vs 309 +/- 394 pg/ml; p = ns) and systemic vascular resistance (1706 +/- 435 vs 1771 +/- 524 dynes/cm sec-5; p = ns) in patients with large or normal left atrial volumes. During exercise the chronotropic response increased less in patients with large atrial volumes (56 +/- 13 vs 45 +/- 14; p = .001). The left atrial chamber stiffness constant was inversely related to peak oxygen consumption and exercise time. Patients with different chamber stiffness showed statistical difference in peak VO2 (16 +/- 4 vs 11 +/- 3 ml/kg/min; p = .0001). Left atrial ejection fraction was directly related to peak oxygen consumption (r = 0.55), but the most strongly correlation was with atrial filling fraction (r = .67).

CONCLUSIONS

This study demonstrates a strong relationship between left atrial function and exercise capacity in patients with chronic heart failure.

Echo-Doppler mitral flow monitoring: an operative tool to evaluate day-to-day tolerance to and effectiveness of beta-adrenergic blocking agent therapy in patients with chronic heart failure

OBJECTIVES

The goals of this study were: 1) to assess the predictive value of baseline mitral flow pattern (MFP) and its changes after loading manipulations as regards tolerance to and effectiveness of beta-adrenergic blocking agent treatment in patients with chronic heart failure (CHF); and 2) to analyze the prognostic implications of chronic MFP modifications after beta-blocker treatment.

BACKGROUND

In patients with CHF, carvedilol therapy induces clinical and hemodynamic improvements. Individual management, clinical effectiveness and prognostic implications, however, remain unclear. The MFP changes induced by loading manipulations provide independent prognostic information.

METHODS

Echo-Doppler was performed at baseline and after loading manipulations in 116 consecutive patients with CHF (left ventricular ejection fraction: 25 +/- 7%); 54 patients with a baseline restrictive MFP were given nitroprusside infusion; 62 patients with a baseline nonrestrictive MFP performed passive leg lifting. According to changes in MFP, we identified four groups: 17 with irreversible restrictive MFP (Irr-rMFP), 37 with reversible restrictive MFP (Rev-rMFP), 12 with unstable nonrestrictive MFP (Un-nrMFP) and 50 with stable nonrestrictive MFP (Sta-nrMFP). Carvedilol therapy (44 +/- 27 mg) was administered blind to results of loading maneuvers. After six months, MFP was reassessed and patients reclassified according to chronic MFP changes. During follow-up, tolerance to and effectiveness of treatment and major cardiac events (death, readmission and urgent transplantation) were considered.

RESULTS

Changes of MFP after loading manipulations were more accurate than baseline MFP in predicting both tolerance to (p < 0.01) and effectiveness of (p < 0.05) carvedilol. After 26 +/- 14 months of follow-up, cardiac events had occurred in 23/102 patients (23%). The event rate in patients with chronic Irr-rMFP or Un-nrMFP was markedly higher than it was in those with Rev-rMFP or Sta-nrMFP.

CONCLUSIONS

In our patients, tolerance to and effectiveness of carvedilol was predicted better by echo-Doppler MFP changes after loading manipulations than by baseline MFP. Chronic changes of MFP after therapy are strong predictors of major cardiac events.

Chronic infusion of dobutamine and nitroprusside in patients with end-stage heart failure awaiting heart transplantation: safety and clinical outcome

BACKGROUND

in patients with severe heart failure additional therapeutic support with intravenous inotropic or vasodilator drugs is frequently employed in an attempt to obtain hemodynamic and clinical control. No data comparing the use and efficacy of chronic intravenous inotropic and vasodilator therapy in patients with advanced heart failure are available.

AIMS

we evaluated, in a group of patients with advanced heart failure undergoing chronic infusion with dobutamine or nitroprusside, in addition to optimized oral therapy, (1) the safety of chronic infusion, (2) the efficacy of both drugs in managing unloading therapy and (3) clinical outcome of the two therapeutic strategies.

METHODS

one hundred and thirteen patients receiving optimized oral therapy, in functional class III/IV with symptoms and signs of refractory heart failure and requiring additional pharmacological support with either intravenous dobutamine or nitroprusside were evaluated. Clinical and therapeutic management and clinical outcome of the two groups were considered.

RESULTS

dobutamine was administered for 12 h/day for 20+/-23 days at a dosage of 7+/-3 microg/kg/min to 43 patients. The mean dose of nitroprusside was 0.76+/-0.99 microg/kg/min. The mean duration of use of this drug, administered as a 12-h/day infusion was 22+/-38 days. Nitroprusside infusion allowed greater doses of short-term ACE-inhibitors to be used compared to pre-infusion (ACE-inhibitor dose: 55+/-30 mg/day vs. 127+/-30 mg/day P<0.0001) and during dobutamine infusion (ACE-inhibitor dose: 85+/-47 mg/day vs. 127+/-30 mg/day P<0.002). Nitroprusside unlike dobutamine significantly improved the NYHA functional class. Of the 113 patients, 109 (97%) had a cardiac event during a mean follow-up of 337+/-264 days. Forty-four patients required hospitalization for worsening congestive heart failure, 45/113 (39%) patients died during the follow-up and 27/113 (24%) patients had a heart transplant in status one. Hospitalization, because of worsening heart failure was less frequent in the nitroprusside than in the dobutamine subgroup [29/51 (57%) vs. 19/22 (86%) P<0.02]. The overall mortality was 28% (20/70) in the nitroprusside group and 58% (25/43) in the dobutamine group (odds ratio 0.33 CI 0.16 to 0.73 P<0.006). In the group treated with nitroprusside, heart transplantation in status one was performed in 16/33 patients (48%), while in the dobutamine group this was done in 11/14 patients (78%) (odds ratio 0.25 CI 0.06-1.02 P<0.06). There was a significant reduction in the combined end-point of mortality/heart transplantation in status one in patients treated with nitroprusside compared to those treated with dobutamine (36/70 (51%) vs. 36/43 (84%) - (odds ratio 0.34 CI 0.14-0.80 P<0.01). The incidence of adverse events in the patients treated with nitroprusside was similar to that in those treated with dobutamine (20% vs. 17% P=ns).

CONCLUSIONS

for patients awaiting heart transplantation chronic intermittent nitroprusside infusions are more effective and safer than dobutamine in relieving symptoms, facilitating unloading therapy management and improving survival. Whether chronic intermittent infusion of nitroprusside could represent a feasible medical strategy in out-patients with severe heart failure remains to be investigated.

[The neurovegetative system in heart failure and heart transplantation]

Increased sympathetic activity and plasma levels of norepinephrine, parasympathetic withdrawal and impaired baroreflex gain have been reported in patients with chronic heart failure (CHF). Since excessive neurohormonal activation is implicated in the progression of heart failure, it is crucial to measure and quantify it in clinical practice. Some techniques that may be suitable for this purpose such as catecholamine plasma level assessment or direct recording of the neural efferent activity to the peripheral muscles, require expertise and are very unattractive in terms of cost-effectiveness. On the contrary, the measures that test the reflex or tonic responses of the sinus node activity have been extensively used in both experimental and clinical studies. However, consensus regarding their true relevance in the clinical scenario has not yet been reached. Heart rate variability is one of the easiest techniques available for physicians but the identification of the RR intervals in CHF is often very difficult owing to the presence of rhythm disorders or of sino-atrial or atrioventricular blocks and the analytical softwares included in the commercially available Holter systems are not reliable enough. Similarly, for all methods currently employed in clinical practice, the assessment of baroreflex sensitivity in CHF has some limitations or is not applicable for all patients. In this article, the main clinical methods used to assess the autonomic nervous system in CHF are reviewed focusing on the clinical applicability of the obtained parameters. It is underlined that, using these techniques, many investigators have obtained important results in the pathophysiological comprehension of the disease, but to date their use in the clinical setting is very modest. Indeed, before the measurement of the autonomic nervous system can be applied to clinical practice and used to guide therapy, more precise insights into the link between the autonomic indexes and sympathetic or parasympathetic activity and between them and mortality are needed. Moreover, no standardization has been established for the various commercial systems and the development of their software has not been guided by any research committee. For many other techniques there are no commercially available devices and the software has been developed in the physiological laboratories as prototypes. These limitations will be overcome if the researchers succeed in convincing the companies about the importance and the clinical applicability of the evaluation of the autonomic nervous system. With regard to cardiac transplantation, as the donor heart is completely denervated, it constitutes an important physiological model for the study of autonomic activity. The more interesting research field has been the assessment of a possible post-transplant reinnervation both at the experimental and clinical levels. It has been shown that in animal models reinnervation occurs within the first year of heart transplantation. Several authors have demonstrated a time-dependent restoration of myocardial norepinephrine content as well as an increase in the heart rate and myocardial contractility in response to neural sympathetic stimulation. Parasympathetic efferent reinnervation has also been demonstrated in a canine transplanted model within 12 months of surgery. Despite evidence in favor of both sympathetic and parasympathetic reinnervation in animals, the problem of whether such reinnervation also occurs in humans is still debated, especially as far as parasympathetic reinnervation is concerned. The presence, in humans, of sympathetic reinnervation has been documented by different methods. However, there are significant differences regarding the degree of regeneration and the frequency of occurrence. It has also been assumed that the regeneration of sympathetic fibers takes place slowly over time. In contrast, regrowth of parasympathetic nerve fibers in patients after heart transplantation has not been unequivocally confirmed. Although various investigators have used the same method, their results differ and are indeed often contradictory. Recently it has been suggested that the type of surgery may have a major influence on neural and particularly parasympathetic regeneration. If the patients undergo heart transplantation by bicaval techniques the nerves are resected and they are more prone to regenerate towards the donor heart. This is not true if the traditional technique is employed.

Baroreflex sensitivity and heart rate variability in the identification of patients at risk for life-threatening arrhythmias: implications for clinical trials

BACKGROUND

The need for accurate risk stratification is heightened by the expanding indications for the implantable cardioverter defibrillator. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) focused interest on patients with both depressed left ventricular ejection fraction (LVEF) and the presence of nonsustained ventricular tachycardia (NSVT). Meanwhile, the prospective study Autonomic Tone and Reflexes After Myocardial Infarctio (ATRAMI) demonstrated that markers of reduced vagal activity, such as depressed baroreflex sensitivity (BRS) an heart rate variability (HRV), are strong predictors of cardiac mortality after myocardial infarction.

METHODS AND RESULTS

We analyzed 1071 ATRAMI patients after myocardial infarction who had data on LVEF, 24-hour ECG recording, and BRS. During follow-up (21 +/- 8 months), 43 patients experienced cardiac death, 5 patients had episodes of sustained VT, and 30 patients experienced sudden death and/or sustained VT. NSVT, depressed BRS, or HRV were all significantly and independently associated with increased mortality. The combination of all 3 risk factor increased the risk of death by 22x. Among patients with LVEF<35%, despite the absence of NSVT, depressed BRS predicted higher mortality (18% versus 4.6%, P = 0.01). This is a clinically important finding because this grou constitutes 25% of all patients with depressed LVEF. For both cardiac and arrhythmic mortality, the sensitivity of lo BRS was higher than that of NSVT and HRV CONCLUSIONS: BRS and HRV contribute importantly and additionally to risk stratification. Particularly when LVEF is depressed, the analysis of BRS identifies a large number of patients at high risk for cardiac and arrhythmic mortalit who might benefit from implantable cardioverter defibrillator therapy without disproportionately increasing the number of false-positives.

Periodic breathing in heart failure patients: testing the hypothesis of instability of the chemoreflex loop

In this study, we applied time- and frequency-domain signal processing techniques to the analysis of respiratory and arterial O(2) saturation (Sa(O(2))) oscillations during nonapneic periodic breathing (PB) in 37 supine awake chronic heart failure patients. O(2) was administered to eight of them at 3 l/min. Instantaneous tidal volume and instantaneous minute ventilation (IMV) signals were obtained from the lung volume signal. The main objectives were to verify 1) whether the timing relationship between IMV and Sa(O(2)) was consistent with modeling predictions derived from the instability hypothesis of PB and 2) whether O(2) administration, by decreasing loop gain and increasing O(2) stores, would have increased system stability reducing or abolishing the ventilatory oscillation. PB was centered around 0.021 Hz, whereas respiratory rate was centered around 0.33 Hz and was almost stable between hyperventilation and hypopnea. The average phase shift between IMV and Sa(O(2)) at the PB frequency was 205 degrees (95% confidence interval 198-212 degrees). In 12 of 37 patients in whom we measured the pure circulatory delay, the predicted lung-to-ear delay was 28.8 +/- 5.2 s and the corresponding observed delay was 30.9 +/- 8.8 s (P = 0.13). In seven of eight patients, O(2) administration abolished PB (in the eighth patient, Sa(O(2)) did not increase). These results show a remarkable consistency between theoretical expectations derived from the instability hypothesis and experimental observations and clearly indicate that a condition of loss of stability in the chemical feedback control of ventilation might play a determinant role in the genesis of PB in awake chronic heart failure patients.

Nonselective beta-adrenergic blocking agent, carvedilol, improves arterial baroflex gain and heart rate variability in patients with stable chronic heart failure

OBJECTIVES

The purpose of this study was to investigate in a case-controlled study whether carvedilol increased baroreflex sensitivity and heart rate variability (HRV).

BACKGROUND

In chronic heart failure (CHF), beta-adrenergic blockade improves symptoms and ventricular function and may favorably affect prognosis. Although beta-blockade therapy is supposed to decrease myocardial adrenergic activity, data on restoration of autonomic balance to the heart and, particularly, on vagal reflexes are limited.

METHODS

Nineteen consecutive patients with moderate, stable CHF (age 54 +/- 7 years, New York Heart Association [NYHA] class II to III, left ventricular ejection fraction [LVEF] 24 +/- 6%), treated with optimized conventional medical therapy, received carvedilol treatment. Controls with CHF were selected from our database on the basis of the following matching criteria: age +/- 3 years, same NYHA class, LVEF +/- 3%, pulmonary wedge pressure +/- 3 mm Hg, peak volume of oxygen +/- 3 ml/kg/min, same therapy. All patients underwent analysis of baroreflex sensitivity (phenylephrine method) and of HRV (24-h Holter recording) at baseline and after six months.

RESULTS

Beta-blockade therapy was associated with a significant improvement in symptoms (NYHA class 2.1 +/- 0.4 vs. 1.8 +/- 0.5, p < 0.01), systolic and diastolic function (LVEF 23 +/- 7 vs. 28 +/- 9%, p < 0.01; pulmonary wedge pressure 17 +/- 8 vs. 14 +/- 7 mm Hg, p < 0.05) and mitral regurgitation area (7.0 +/- 5.1 vs. 3.6 +/- 3.0 cm2, p < 0.01). No significant differences were observed in either clinical or hemodynamic indexes in control patients. Phenylephrine method increased significantly after carvedilol (from 3.7 +/- 3.4 to 7.1 +/- 4.9 ms/mm Hg, p < 0.01) as well as RR interval (from 791 +/- 113 to 894 +/- 110 ms, p < 0.001), 24-h standard deviation of normal RR interval and root mean square of successive differences (from 56 +/- 17 to 80 +/- 28 ms and from 12 +/- 7 to 18 +/- 9 ms, all p < 0.05), while all parameters remained unmodified in controls. During a mean follow-up of 19 +/- 8 months a reduced number of cardiac events (death plus heart transplantation, 58% vs. 31%) occurred in those patients receiving beta-blockade.

CONCLUSIONS

Besides the well-known effects on ventricular function, treatment with carvedilol in CHF restores both autonomic balance and the ability to increase reflex vagal activity. This protective mechanism may contribute to the beneficial effect of beta-blockade treatment on prognosis in CHF.

Comparison between invasive and non-invasive measurements of baroreflex sensitivity; implications for studies on risk stratification after a myocardial infarction

AIMS

The ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) study has proved the independent prognostic value of baroreflex sensitivity. A limitation of the traditional method of estimating baroreflex sensitivity by phenylephrine, is the need to monitor intra-arterial blood pressure. Our objective was to establish whether this invasive method of monitoring could be superseded by non-invasive methods, such as the Finapres device.

METHODS AND RESULTS

Patients with three repeated invasive and non-invasive baroreflex sensitivity measurements were selected from the ATRAMI database (n = 454). The mean of these measurements was taken as the baroreflex sensitivity estimate. The repeatability of both methods (standard deviation of the three measurements) decreased with increasing baroreflex sensitivity. There was no constant bias between invasive and non-invasive measurements (0. 22+/-2.2 ms. mmHg(-1), P = 0.42). The linear correlation was very high (r = 0.91, P < 0.01). The normalized 95% limits of agreement were -0.5 and 0.52. On survival analysis, invasive and non-invasive baroreflex sensitivity gave similar prognostic information (likelihood ratio: 155.6 (P = 0.007) and 155.0 (P = 0.006); risk ratio: 0.79 and 0.81, respectively). According to the ATRAMI cut-off points, 85% of patients were classified concordantly by the two methods. None of the patients at high (low) risk with the invasive method were classified as low (high) risk class by the non-invasive method.

CONCLUSION

Despite wide limits of agreement, invasive and non-invasive baroreflex sensitivity measurements are highly correlated and provide equivalent prognostic information.

Invasive and non-invasive determinants of pulmonary hypertension in patients with chronic heart failure

BACKGROUND

In patients with chronic heart failure, pulmonary hypertension is an important predictive marker of adverse outcome. Its invasive and non-invasive determinants have not been evaluated.

OBJECTIVE

This study was performed to evaluate hemodynamic determinants of pulmonary hypertension in chronic heart failure and to compare the predictive value of Doppler indices with that of invasively measured hemodynamic indices.

METHODS

Right heart catheterization and transthoracic echo-Doppler were simultaneously performed in 259 consecutive patients with chronic heart failure (ejection fraction 24% +/- 7%) who were in sinus rhythm and receiving optimized medical therapy. Systolic pulmonary artery pressure (sPAP), cardiac index, transpulmonary gradient pressure, and pulmonary wedge pressure (PWP) were measured invasively. Left atrial and ventricular systolic and diastolic volumes, the ratio of maximal early to late diastolic filling velocities (E/A ratio), deceleration time (DT) and atrial filling fraction (AFF) of transmitral flow, systolic fraction of forward pulmonary venous flow (SFpvf), and mitral regurgitation were quantified by echo-Doppler.

RESULTS

Patients with pulmonary hypertension had greater left atrial systolic and diastolic dysfunction, more left ventricular diastolic abnormalities, and greater hemodynamic impairment. The correlations between systolic left ventricular indices, mitral regurgitation, and sPAP were generally poor. Among invasive and non-invasive measurements, PWP (r = 0.89, p < 0.0001) and SFpvf (r = -0.68, p < 0.0001) showed the strongest correlation with sPAP. When we compared all patients with those without mitral regurgitation, the correlations between E/A ratio (r = 0.56 vs r = 0. 74, p < 0.002), SFpvf (r = -0.68 vs r = -0.84, p < 0.03), and systolic pulmonary artery pressure were significantly stronger. Multivariate analysis revealed that PWP was the strongest invasive independent predictor of systolic pulmonary artery pressure in patients with (R(2) = 0.87, p < 0.0001) and without (R(2) = 0.90, p < 0.0001) mitral regurgitation. A PWP > or= 18 mm Hg (odds ratio [95% CL], 142 (41-570) was strongly associated with systolic pulmonary hypertension. Among non-invasive variables DT, SFpvf, and AFF were identified as independent predictors of sPAP in patients with (R(2) = 0.56, p < 0.0001) and without (R(2) = 0.78, p < 0.0001) mitral regurgitation. A DT < 130 (odds ratio [95% CL], 3.5 (1.3-8.5), SFfvp < 40% (odds ratio [95% CL], 333 (41-1,007), and AFF < 30% (odds ratio [95% CL], 2 (1.3-7) most strongly predicted systolic pulmonary hypertension.

CONCLUSIONS

The results of this study indicate that in patients with chronic heart failure, venous pulmonary congestion is an important determinant of systolic pulmonary artery hypertension. Hemodynamic and Doppler determinants showed similar predictive power in identifying systolic pulmonary artery hypertension.

Beta-blockade therapy in chronic heart failure: diastolic function and mitral regurgitation improvement by carvedilol

BACKGROUND

In patients with chronic heart failure, the use of carvedilol therapy induces clinical and hemodynamic improvement. However, although the benefits of this beta-blocker have been established in patients with chronic heart failure, the mechanisms underlying them and the changes in left ventricular systolic function, diastolic function, and mitral regurgitation during long-term therapy remain unclear.

OBJECTIVE

To identify the clinical and functional effects of carvedilol, focusing on diastolic function and mitral regurgitation variations.

METHODS

Forty-five consecutive patients with chronic heart failure (ejection fraction 24% +/- 7%), 17 with dilated ischemic and 28 with nonischemic cardiomyopathy, were treated with carvedilol (mean dose 44 +/- 30 mg) and matched for clinical (New York Heart Association functional class and heart failure duration) and hemodynamic (cardiac index and pulmonary wedge pressure) characteristics to a control group. Clinical and echocardiographic variables were measured in the 2 groups at baseline and after 6 months and the results compared.

RESULTS

After 6 months of treatment with carvedilol, left ventricular ejection fraction had increased from 24% +/- 7% to 29% +/- 9% (P <.0001); this change was caused by a reduction in end-systolic volume index (106 +/- 41 vs 93 +/- 37 mL/m(2); P <. 0001). Deceleration time of early diastolic filling increased (134 +/- 74 vs 196 +/- 63 ms; P <.0001). Seventeen of the 27 patients with demonstrated improvement of left ventricular diastolic filling moved from having a restrictive filling pattern to having a normal or pseudonormal left ventricular filling pattern. In the control group, no significant changes in deceleration time of early diastolic filling were found (139 +/- 74 vs 132 +/- 45 ms; P = not significant). The effective regurgitant orifice area decreased significantly in the carvedilol group but not in the control group. These changes were associated with a significant reduction of the mitral regurgitant stroke volume in the carvedilol group (50 +/- 25 vs 16 +/- 13 mL; P <.0001) but not in the control group (57 +/- 29 vs 47 +/- 24 mL; P = not significant). These changes of mitral regurgitation were closely associated with significant improvement of forward aortic stroke volume (r = -.57, P <.0001). These findings were not observed in patients in the control group.

CONCLUSIONS

The results of this study show that long-term carvedilol therapy in patients with chronic heart failure was able to prevent or partially reverse progressive left ventricular dilatation. The effects on left ventricular remodeling were associated with a concomitant recovery of diastolic reserve and a decrease of mitral regurgitation, which have been demonstrated to be powerful prognostic predictors in such patients. Overall these findings provide important insights into the pathophysiologic mechanisms by which carvedilol improves the clinical course of patients with chronic heart failure.

Cardiorespiratory interactions during periodic breathing in awake chronic heart failure patients

We applied spectral techniques to the analysis of cardiorespiratory signals [instantaneous lung volume (ILV), instantaneous tidal volume (ITV), arterial O(2) saturation (Sa(O(2))) at the ear, heart rate (HR), systolic (SAP), and diastolic (DAP) arterial pressure] during nonapneic periodic breathing (PB) in 29 awake chronic heart failure (CHF) patients and estimated the timing relationships between respiratory and slow cardiovascular (<0.04 Hz) oscillations. Our aim was 1) to elucidate major mechanisms involved in cardiorespiratory interactions during PB and 2) to test the hypothesis of a central vasomotor origin of PB. All cardiovascular signals were characterized by a dominant (>/=84% of total power) oscillation at the frequency of PB (mean +/- SE: 0.022 +/- 0.0008 Hz), highly coherent (>/=0.89), and delayed with respect to ITV (ITV-HR, 2.4 +/- 0.72 s; ITV-SAP, 6.7 +/- 0.65 s; ITV-DAP, 3.2 +/- 0.61 s; P < 0.01). Sa(O(2)) was highly coherent with (coherence function = 0.96 +/- 0. 009) and almost opposite in phase to ITV. These findings demonstrate the existence of a generalized cardiorespiratory rhythm led by the ventilatory oscillation and suggest that 1) the cyclic increase in inspiratory drive and cardiopulmonary reflexes and 2) mechanical effects of PB-induced changes in intrathoracic pressure are the more likely sources of the HR and blood pressure oscillations, respectively. The timing relationship between ITV and blood pressure signals excludes the possibility that PB represents the effect of a central vasomotor rhythm.

Association between hemodynamic impairment and Cheyne-Stokes respiration and periodic breathing in chronic stable congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

Irregular breathing occurs frequently in patients with congestive heart failure (CHF) both during daytime and nighttime. Many factors are involved in the genesis of these breathing abnormalities, but the role of the hemodynamic impairment remains controversial. This study investigated the relation between worsening ventricular function and the frequency of respiratory disorders in patients with mild to severe CHF. One hundred fifty patients with CHF (mean age 53 +/- 8 years, left ventricular (LV) ejection fraction 26 +/- 7, in New York Heart Association [NYHA] classes II to IV, and who underwent stable therapy for > or =2 weeks) were studied. Analysis of instantaneous lung volume signal and arterial oxygen saturation during awake daytime revealed a normal respiratory pattern in 63 patients, whereas 87 had a persistent alteration of breathing, with a typical Cheyne-Stokes respiration (CSR) in 42 and periodic breathing (PB [oscillation of tidal volumes without apnea]) in 45 patients. Patients with PB and CSR showed a more pronounced hemodynamic impairment with a significantly reduced cardiac index, an increased pulmonary arterial wedge pressure, and a longer lung-to-ear circulation time (LECT) compared with patients with normal respiratory patterns. In a logistic regression model that included all of the variables significantly associated with breathing disorders, cardiac index and LECT emerged as the major determinants of CSR. In those patients with LECT > or =30 seconds (upper quartile) and cardiac index < or =1.9 L/min/m2 (lower quartiles), the incidence of CSR was significantly higher (69%) than in patients with lower LECT and higher cardiac index (14%, p <0.001). In conclusion, abnormalities of breathing activity during daytime are significantly associated with a prolonged circulation time and a more severe impairment of systolic and diastolic LV indexes.

Arterial baroreflex modulation of heart rate in patients early after heart transplantation: lack of parasympathetic reinnervation

BACKGROUND

Orthotopic heart transplantation results in cardiac denervation. The presence of cardiac parasympathetic reinnervation in humans has been widely debated based on the application of differing indirect measures of autonomic control. However no attempt has been made to analyse the reflex heart rate response to baroreceptor stimulation whose occurrence is generally considered a reliable marker of the ability to activate cardiac vagal reflexes. This study tested the hypothesis that the presence of donor heart RR interval lengthening following phenylephrine induced blood pressure increase would be an index of parasympathetic reinnervation.

METHODS

Baroreflex sensitivity (BRS) was assessed in 30 patients (mean age 51+/-12 years) 1-24 months after heart transplantation carried out by the standard Lower-Shumway technique. In 6 patients the recipient atrium rate response (P-P interval) to baroreceptor stimulation by phenylephrine was also simultaneously determined by transesophageal recording.

RESULTS

None of the 30 patients showed prolongation of RR intervals in the donor heart. The average BRS value was -0.28+/-0.54 ms/mmHg (range -1.3-0.7 ms/mm Hg). In the 6 patients in whom BRS was obtained at both the recipient atrium (P-P) and donor heart (R-R) the changes were 7.6+/-5.7 ms/mm Hg and -0.38+/-0.58 ms/mm Hg respectively (p = 0.02), thus confirming that the absent RR interval lengthening in the donor heart is the consequence of efferent vagal fiber interruption.

CONCLUSIONS

The absence of any RR interval prolongation following phenylephrine induced baroreceptor stimulation demonstrates that vagal efferent reinnervation of the donor heart does not occur up to 24 months in patients operated via the standard Lower-Shumway procedure. It is also suggested that analysis of baroreceptor reflexes is a more specific method in the examination of cardiac parasympathetic reinnervation.

The development of hyperventilation in patients with chronic heart failure and Cheyne-Strokes respiration: a possible role of chronic hypoxia

AIM

To analyze the relationship between daytime respiratory and cardiac function in patients with compensated chronic heart failure (CHF) with and without periodic breathing (PB) or Cheyne-Stokes respiration (CSR).

PATIENTS

We studied 132 patients (female, 13%; mean age, 53+/-8 years; body mass index, 25.9+/-3.5 kg/m2; left ventricular ejection fraction <40%; 23% in New York Heart Association class I, 43% in class II, and 34% in class III-IV).

METHODS

Measurement of pulmonary function and blood gases, hemodynamic evaluation, analysis of breathing profile, echocardiography, recording of ECG, beat-to-beat arterial oxygen saturation, and respiration during spontaneous breathing.

RESULTS

Fifty-eight percent of patients showed PB or CSR. Patients with PB or CSR have greater cardiac function impairment. Mean values of lung volumes and PaO2 were similar in the three groups of patients considered. In contrast, patients with PB or CSR had an increased minute ventilation and reduced PaCO2 values. Interestingly, patients with PB or CSR had lower values of arterial content of O2 and systemic oxygen transport (SOT) than patients with a normal breathing pattern (SOT, 394+/-9.8, 347+/-9.6, 438+/-11 mL of O2/min/m2, respectively; analysis of variance p<0.001). Weak correlations were found among lung volumes, blood gases, and cardiac function parameters: ie, vital capacity was correlated inversely with pulmonary capillary wedge pressure (PCWP) (-0.25; p<0.05); PaCO2 with PCWP (r=0.26; p<0.05), lung-to-ear circulation time (LECT) (r=-0.4; p<0.05), SOT (r=-0.33; p<0.0001), and cardiac index (CI) (r=0.27; p=0.003). Multiple regression analyses showed that arterial PCO2 was significantly correlated with SOT, LECT, and CI (r=0.51; r2=0.26; p<0.000001); the correlation became stronger considering only CSR patients (r=0.64; r2=0.4; p<0.001).

CONCLUSIONS

Our study shows that patients with daytime breathing disorders have chronic hypocapnia. A reduced SOT may be one of the stimuli determining increased minute ventilation in these patients.

Baroreflex sensitivity and heart-rate variability in prediction of total cardiac mortality after myocardial infarction. ATRAMI (Autonomic Tone and Reflexes After Myocardial Infarction) Investigators

BACKGROUND

Experimental evidence suggests that autonomic markers such as heart-rate variability and baroreflex sensitivity (BRS) may contribute to postinfarction risk stratification. There are clinical data to support this concept for heart-rate variability. The main objective of the ATRAMI study was to provide prospective data on the additional and independent prognostic value for cardiac mortality of heart-rate variability and BRS in patients after myocardial infarction in whom left-ventricular ejection fraction (LVEF) and ventricular arrhythmias were known.

METHODS

This multicentre international prospective study enrolled 1284 patients with a recent (<28 days) myocardial infarction. 24 h Holter recording was done to quantify heart-rate variability (measured as standard deviation of normal to normal RR intervals [SDNN]) and ventricular arrhythmias. BRS was calculated from measurement of the rate-pressure response to intravenous phenylephrine.

FINDINGS

During 21 (SD 8) months of follow-up, the primary endpoint, cardiac mortality, included 44 cardiac deaths and five non-fatal cardiac arrests. Low values of either heart-rate variability (SDNN <70 ms) or BRS (<3.0 ms per mm Hg) carried a significant multivariate risk of cardiac mortality (3.2 [95% CI 1.42-7.36] and 2.8 [1.24-6.16], respectively). The association of low SDNN and BRS further increased risk; the 2-year mortality was 17% when both were below the cut-offs and 2% (p<0.0001) when both were well preserved (SDNN >105 ms, BRS >6.1 ms per mm Hg). The association of low SDNN or BRS with LVEF below 35% carried a relative risk of 6.7 (3.1-14.6) or 8.7 (4.3-17.6), respectively, compared with patients with LVEF above 35% and less compromised SDNN (> or = 70 ms) and BRS (> or = 3 ms per mm Hg).

INTERPRETATION

ATRAMI provides clinical evidence that after myocardial infarction the analysis of vagal reflexes has significant prognostic value independently of LVEF and of ventricular arrhythmias and that it significantly adds to the prognostic value of heart-rate variability.

Assessing baroreflex sensitivity in post-myocardial infarction patients: comparison of spectral and phenylephrine techniques

OBJECTIVES

This study sought to compare, in post-myocardial infarction patients, baroreflex sensitivity (BRS) measured by the phenylephrine method (Phe-BRS) with that estimated by the Robbe (Robbe-BRS) and Pagani (alpha-low frequency [LF] and alpha-high frequency [HF]) spectral techniques.

BACKGROUND

BRS assessed by Phe-BRS has been shown to be of prognostic value in patients with a previous myocardial infarction, but the need for drug injection limits the use of this technique. Several noninvasive methods based on spectral analysis of systolic arterial pressure and heart period have been proposed, but their agreement with Phe-BRS has never been investigated in post-myocardial infarction patients.

METHODS

The linear association and the agreement between each spectral measurement and Phe-BRS were assessed by correlation analysis and by computing the relative bias and the limits of agreement in 51 post-myocardial infarction patients.

RESULTS

The correlation with Phe-BRS was r = 0.63 for Robbe-BRS, r = 0.62 for alpha-LF and r = 0.59 for alpha-HF. The relative bias was significant for alpha-LF (2.6 ms/mm Hg, p < 0.001) and alpha-HF (2.5 ms/mm Hg, p = 0.01) and not significant (-0.6 ms/mm Hg, p = 0.3) for Robbe-BRS. The normalized limits of agreement ranged from -98% to 95% for Robbe-BRS, from -67% to 126% for alpha-LF and from -108% to 143% for alpha-HF. When patients were classified according to left ventricular ejection fraction (LVEF, cutoff value 40%), the relative bias was higher in patients with a depressed LVEF, although statistical significance was high only for Robbe-BRS and was borderline for alpha-LF. The limits of agreement were similar in both groups of patients (p > 0.3).

CONCLUSIONS

Despite a substantial linear association, the agreement between spectral measurements and Phe-BRS in post-myocardial infarction patients is weak because the difference can be as large as the BRS value being estimated. Phe-BRS is the measurement most associated with hemodynamic impairment. Because several factors within each method contribute to the overall difference, neither method can be defined as being better than the other in estimating baroreflex gain, nor can one be used as an alternative to the other. Ad hoc studies are needed to assess which method provides the most useful physiologic or pathophysiologic information or the most accurate prediction of prognosis.

Arterial baroreflex modulation of heart rate in chronic heart failure: clinical and hemodynamic correlates and prognostic implications

BACKGROUND

In chronic heart failure (CHF), arterial baroreflex regulation of cardiac function is impaired, leading to a reduction in the tonic restraining influence on the sympathetic nervous system. Because baroreflex sensitivity (BRS), as assessed by the phenylephrine technique, significantly contributes to postinfarction risk stratification, the aim of the present study was to evaluate whether in CHF patients a depressed BRS is associated with a worse clinical hemodynamic status and unfavorable outcome.

METHODS AND RESULTS

BRS was assessed in 282 CHF patients in sinus rhythm receiving stable medical therapy (age, 52+/-9 years; New York Heart Association [NYHA] class, 2.4+/-0.6; left ventricular ejection fraction [LVEF], 23+/-6%). The BRS of the entire population averaged 3.9+/-4.0 ms/mm Hg (mean+/-SD) and was significantly related to LVEF and hemodynamic parameters (LVEF, P<.005; cardiac index and pulmonary wedge pressure, P<.001 by regression analysis). Patients in NYHA classes III or IV and those with severe mitral regurgitation had markedly depressed vagal reflexes. The association of BRS with survival was described after its categorization in three groups: below the lowest quartile (<1.3 ms/mm Hg), between the lowest quartile and the median (1.3 to 3 ms/mm Hg), and above the median (>3 ms/mm Hg). During a mean follow-up of 15+/-12 months, 78 primary events (cardiac death, nonfatal cardiac arrest, and status 1 priority transplantation) occurred (27.6%). BRS was significantly related to outcome (log rank, 9.1; P<.01), with a relative risk of 2.7 (95% confidence interval, 1.6 to 4.7) for patients with the major derangement in BRS (<1.3 ms/mm Hg). At multivariate analysis, BRS was an independent predictor of death after adjustment for noninvasive known risk factors but not when hemodynamic indexes were also considered. In CHF patients with severe mitral regurgitation, however, BRS remained a strong prognostic marker independent of hemodynamic function.

CONCLUSIONS

In moderate to severe CHF, a depressed sensitivity of vagal reflexes parallels the deterioration of clinical and hemodynamic status and is significantly associated with poor survival. Particularly in patients with severe mitral regurgitation the baroreceptor modulation of heart rate provides prognostic information of incremental value to hemodynamic parameters.

Depressed arterial baroreflex sensitivity and not reduced heart rate variability identifies patients with chronic heart failure and nonsustained ventricular tachycardia: the effect of high ventricular filling pressure

In chronic heart failure (CHF) the contributing role of increased sympathetic activity and hemodynamic dysfunction in the genesis of ventricular arrhythmias has not been well established. To assess the relation between severe ventricular arrhythmias, hemodynamic impairment, and autonomic nervous system derangement, 142 patients with CHF in sinus rhythm underwent 24-hour electrocardiographic recording, right-sided heart catheterization, and evaluation of sympathovagal balance by heart rate variability (HRV) and baroreflex sensitivity (BRS). Patients were grouped according to the absence (without nonsustained ventricular tachycardia [NSVT]; n = 87) or presence (with NSVT; n = 55) of NSVT. Patients with NSVT had higher pulmonary artery and capillary pressures and more pronounced signs of sympathetic activation and parasympathetic withdrawal compared with those without NSVT. However, logistic regression analysis revealed that depressed BRS but not reduced HRV was significantly associated with the presence of NSVT, at both univariate analysis and after adjustment for clinical and hemodynamic variables. Moreover, it was found that when depressed BRS was associated with high pulmonary capillary pressure, the odds ratio for having NSVT rose markedly from 3.8 to 6.5. In conclusion, this study indicates that in stable CHF the assessment of arterial baroreflex function, but not HRV analysis, allows identification of patients at high risk of NSVT. It is suggested that the effect of depressed BRS is strengthened by the simultaneous presence of increased myocardial wall stress. These data support the hypothesis of a contributory role of autonomic nervous system dysfunction as expressed by the inability to activate effective vagal reflexes and an indirect index of ventricular stretch in the genesis of life-threatening arrhythmias.

Abnormal awake respiratory patterns are common in chronic heart failure and may prevent evaluation of autonomic tone by measures of heart rate variability

BACKGROUND

Reduced heart rate variability, particularly in the Very-low-frequency (VLF) spectral band, has been found to be a marker for poor prognosis in patients after myocardial infarction, but the origin of the VLF oscillations is unclear. In this study, we demonstrate that the power of cardiovascular oscillations in the VLF band in awake patients with mild to severe chronic heart failure is greatly increased by the common occurrence of unrecognized irregularity of breathing, which may confound the use of heart rate variability measures as indexes of autonomic tone or prognosis.

METHODS AND RESULTS

Among 110 consecutive patients referred for consideration of transplantation, 90 were in sinus rhythm, of whom 10 were excluded as unstable. The remaining 80 patients underwent recordings of ECG, beat-to-beat arterial oxygen saturation (SaO2), and respiration during both spontaneous and controlled breathing. During spontaneous awake breathing, 64% showed periodic breathing or Cheyne-Stokes respiration (CSR), which was associated with dominant power in the VLF band of all signals. This VLF power accounted for 55%, 77%, and 87% of heart rate variability, respectively, in patients with normal breathing, periodic breathing, and CSR. It was reduced by 48% and 62%, respectively, during controlled breathing in patients with periodic breathing or CSR. Controlled ventilation also improved oxygen saturation and markedly reduced its variability.

CONCLUSIONS

Breathing disorders are surprisingly common in awake patients with poor left ventricular function and produce large VLF oscillations in heart rate variability. If measures of heart rate variability are used for prognostic purposes during both short-term and long-term recordings, the confounding effects of variable respiratory patterns should be excluded. Respiratory rehabilitation might help control potentially hazardous surges in sympathetic tone.

Rapid fall in sympathetic nerve hyperactivity in patients with heart failure after cardiac transplantation

BACKGROUND

Severe heart failure is associated with an intense sympathetic nerve hyperactivity. After cardiac transplantation, neurochemical studies have indicated a normalization of sympathetic outflow. Intraneural recordings have, however, yielded varying results; both a normalization and a remaining hyperactivity have been obtained in cardiac transplant recipients, the latter being attributed to cyclosporine treatment.

METHODS AND RESULTS

To circumvent the methodologic variation associated with different patient groups in cross-sectional studies, a longitudinal study design was employed in this study. Intraneural recordings of muscle sympathetic nerve activity in 21 heart failure patients were performed before, and repeatedly during the first year after, heart transplantation. Before surgery, muscle sympathetic nerve activity was augmented in all patients (78 +/- 4 bursts/min, 90 +/- 2 bursts/100 heartbeats). Both muscle sympathetic nerve activity burst frequency (burst/minute) and burst incidence (bursts/100 heartbeats) decreased rapidly following surgery. One month after surgery, burst frequency was reduced by 35% (51 +/- 5 bursts/min P < .05), whereas burst incidence decreased by 32% (61 +/- 5 bursts/100 heartbeats, P < .05). This decrease remained unchanged up to 1 year after surgery. The fall in posttransplant muscle sympathetic nerve activity was similar in transplant recipients who developed hypertension during the course of the study (n = 12) and those who remained normotensive (n = 9).

CONCLUSIONS

The sympathoexcitation recorded in patients with heart failure was rapidly and substantially reduced after cardiac transplantation despite cyclosporine treatment, most likely reflecting improved central and peripheral hemodynamics.

Alterations of breathing in chronic heart failure: clinical relevance of arterial oxygen saturation instability

1. In patients with chronic heart failure (CHF) alterations of breathing such as Cheyne-Stokes respiration (CSR) or periodic breathing, (PB) have been frequently described during both day- and night-time. These respiratory rhythm disorders are associated with marked oscillations of arterial oxygen saturation (SaO2) which may expose the patients to prolonged hypoxia. 2. In 40 stable CHF patients and 8 controls during awake day-time, we studied the relationship between alterations of breathing and SaO2, to verify the effect of voluntary control of respiration or oxygen therapy on the instability of SaO2 (analyzed as standard deviation (SD) of the mean value). Simultaneous recordings of ECG, lung volumes and SaO2 were made during 10 min. resting and 4 min. controlled breathing In a subgroup of 5 CHF the effect of oxygen therapy was compared to that of controlled breathing. 3. It was found that 62% of CHF had CSR or PB. Mean SaO2 and SD of SaO2 were significantly different in CHF as compared to controls (respectively 92.4 +/- 2.5 vs 95.4 +/- 0.5%, p < 0.002 and (1.27 +/- 0.9 vs 0.28 +/- 0.13%, p < 0.01), but among CHF pts those with CSR and PB had a lower SaO2 and a more pronounced instability of SaO2. Controlled breathing eliminated apneas and reduced or abolished the variation of tidal volume. In both control and CHF it resulted in an increase of mean SaO2 while a significant reduction of SaO2 instability was observed only in CHF, particularly if CSR or PB were present. Voluntary control of respiration was similar to oxygen therapy in increasing SaO2, but more effective on SaO2 SD. 4. It is concluded that in stable CHF, resting SaO2 is reduced and showed a marked instability particularly when periodic alterations of breathing were present. Continuous beat-to-beat recording of SaO2 may detect patients who have PB or CSR. Training to produce more regular breathing, regardless of the amount of ventilation, may represent a useful intervention.

An oscillation of the respiratory control system accounts for most of the heart period variability of chronic heart failure patients

A periodic breathing (PB) pattern is often observed in chronic heart failure (CHF) patients (pts). In order to clarify the role of this abnormal respiratory activity upon heart period variability we investigated, in a group of 20 stable CHF pts (NYHA class II to III, median EF 24%) showing a PB pattern, 1) whether observed data were consistent with the instability hypothesis of PB and 2) the relationship between oscillations of heart period and the contemporary fluctuations of ventilatory and chemoreceptor activity. Univariate and bivariate spectral analysis were performed on short-term resting recordings of instantaneous lung volume (ILV), instantaneous minute ventilation (IMV), heart period (HP) and arterial O2 saturation at the ear (SpO2). A very low frequency (VLF) oscillation around 0.02 Hz, associated with PB, was observed in all signals and contributed to 75% (23 divided by .99) (median (range)) of the HP variability. The coherence between ILV and HP was 0.77 (0.3 divided by 0.95) and between SpO2 and HP 0.8 (0.4 divided by 0.98. A high coherence was also found between IMV and SpO2: 0.9 (0.6 divided by 0.98). The median phase lag between IMB and SpO2 was -211 degrees (-240 divided by -156), between ILV and HP -205 degrees (-260 divided by -180) and between SpO2 and HP 0 degree (-26 divided by 30). The estimated lung-to-ear circulation time was 24.5 s (12.5 divided by 36.5). This study definitely confirms that during PB a common rhythm is shared between the respiratory and cardiovascular regulatory system Taking into account the error introduced by the measuring process, our results, are consistent with the hypothesis that periodic breathing of CHF pts originates from an instability of the feedback control system of ventilation. Hence most of the HP variability of these pts simply reflects abnormal pattern of respiratory activity.

Concomitant factors of decompensation in chronic heart failure

The concomitant factors implicated in 328 nonfatal decompensations of 304 patients with congestive heart failure were: arrhythmias in 24%, infections in 23%, poor compliance in 15%, angina in 14%, iatrogenic factors in 10%, and other causes in 5% of cases. New York Heart Association class and right atrial pressure significantly related to the occurrence of decompensation. Poor compliance and angina were unpredictable, infection was related to pulmonary wedge pressure, iatrogenic factors were predicted by the more advanced functional classes, whereas arrhythmias were more frequent in patients with renal failure.

Estimation of arterial blood pressure variability by spectral analysis: comparison between Finapres and invasive measurements

In order to assess the accuracy of spectral analysis of beat-by-beat arterial blood pressure fluctuations recorded by the finger technique we analysed simultaneous ipsilateral resting sequences (180 s) of systolic blood pressure (SP) and diastolic blood pressure (DP) obtained by brachial artery cannulation and by the Finapres device in 26 post-myocardial infarction (post-MI) and 24 chronic heart failure (CHF) patients. We estimated: (i) the total variability and the power in the bands 0.01-0.04 Hz (band 1), 0.04-0.07 Hz (band I), 0.07-0.15 Hz (band III) and 0.15-0.45 Hz (band IV); and (ii) the group-average transfer function between the invasive and non-invasive channel. The total variability of intra-arterial SP was greatly enhanced by the Finapres device in both populations (p < 0.01) mainly due to the increase of power in bands I and II (mean percentage errors 157 and 111% in post-MI and 368 and 245% in CHF patients respectively). The power in band IV was significantly reduced in post-MI (p < 0.001) but not in CHF patients. The total DP variability increased in post-MI patients (p < 0.001) due to the increase in bands I and II (mean percentage errors 62 and 43% respectively). No significant difference was found in bands III and IV of the same group and in the overall variability of CHF. Linear system analysis showed that intra-arterial SP oscillations in both groups are amplified by the Finapres device in bands I and II, with a higher gain in CHF patients, whereas they are attenuated in band IV. Band III acts as a transition band. DP oscillations recorded non-invasively are slightly amplified in bands I and II of post-MI patients only and are attenuated in band IV of both groups. A substantial fraction (approximately 30%) of the non-invasive SP variability in band I cannot be explained as a pure linear transformation (amplification) of the invasive signal. A phase delay in the range 7 degrees-10 degrees relates the non-invasive signal to the invasive one in the region 0.025-0.17 Hz and approaches zero elsewhere. Several mechanisms were examined as potential causes of the invasive-non-invasive differences. We argue that these differences are mainly due to the complex rhythmic behaviour of peripheral resistance vessels.

Linear and nonlinear dynamics of heart rate variability after acute myocardial infarction with normal and reduced left ventricular ejection fraction

We analyzed heart rate variability (HRV) in 2 groups of patients after acute myocardial infarction with normal and reduced ejection fraction (EF) by considering both the power of the 2 major harmonic components at low and high frequency and 2 indexes of nonlinear dynamics, namely the 1/f slope and the correlation dimension D2. HRV of patients with a reduced EF was characterized by a diminished RR variance as well as a different distribution of the residual power in all frequency ranges, with lower values of the low-frequency component expressed in both absolute and normalized units, and of the low- to high-frequency ratio. In these patients we also observed a steeper slope of the negative regression line between power and frequency in the very low frequency range. The presence of a smaller fractal dimension was suggested by a lower D2. Thus, in patients after acute myocardial infarction with a reduced EF, the reduction in HRV is associated with a different distribution of the residual power in the entire frequency range, which suggests a diminished responsiveness of sinus node to neural modulatory inputs.

Patency of infarct-related artery. Effect of restoration of anterograde flow on vagal reflexes. ATRAMI (Automatic Tone and Reflexes After Myocardial Infarction) Investigators

BACKGROUND

In post-myocardial infarction (MI) patients, the restoration of anterograde flow in the infarct-related artery (IRA) significantly improves survival. Limitation of infarct size and increased electrical stability of the myocardium are likely operating mechanisms for this beneficial effect. We tested the hypothesis that patency of the IRA may enhance vagal reflexes, a factor known to affect electrical stability of the infarcted myocardium.

METHODS AND RESULTS

Analysis of angiographic data was performed in 359 of 1284 post-MI patients enrolled in a multicenter prospective study within 8 weeks after the index MI. All the patients underwent baroreflex sensitivity (BRS) assessment by the phenylephrine method. The BRS of the entire population averaged 8.2+/-5.5 ms/mm Hg and was significantly related to age but not to ejection fraction (EF). One-, two-, and three-vessel disease was present in 138, 96, and 99 patients, respectively, while no coronary stenosis was observed in 26. IRA patency was documented in 234 patients (65%), while in the remaining 125 (35%), the artery remained occluded. Patients with occluded IRAs had more extensive coronary disease (2 to 3 vessels, 71% versus 46%, P<.01) and more depressed left ventricular (LV) function (LVEF, 48+/-13% versus 53+/-12%, P<.001). Patency of the IRA was associated with higher BRS values (BRS, 8.9+/-5.8 versus 7.1+/-4.7 ms/mm Hg, P<.005) and with a lower incidence (9% versus 18% P<.02) of markedly depressed BRS (<3 ms/mm Hg), a condition suggested by preliminary studies to be associated with an increased risk of post-MI mortality. The association between IRA patency and BRS was more evident in anterior than in inferior MI. Multivariate regression analysis showed that age of the patient and patency of the IRA were the major independent determinants of BRS, while LVEF was weakly related to BRS and only when analyzed as a categorized variable.

CONCLUSIONS

The presence of an open IRA is associated with higher baroreflex sensitivity, and this effect is largely independent of limitation of infarct size by IRA patency. These data offer new insights into the mechanisms by which coronary artery patency may affect cardiac electrical stability and survival.

Baroreflex sensitivity

Baroreflex sensitivity (BRS) has rapidly gained considerable attention as a result of multiple experimental and clinical reports on its prognostic value after a myocardial infarction. This article reviews the several aspects related to the use and significance of BRS. The methodology of baroreflex testing in man is described. The complex pathophysiology underlying BRS and the hypotheses proposed to explain its frequent reduction after a myocardial infarction are discussed. The section on experimental data also provides a rationale to understand the relation between increased vagal activity and reduced propensity for ventricular fibrillation. The article focuses largely on the clinical studies relating BRS and risk of cardiac mortality and also discusses the several attempts to modify this marker of reflex vagal activation.

Interleukin 12 administration induces T helper type 1 cells and accelerates autoimmune diabetes in NOD mice

T cells play a major role in the development of insulin-dependent diabetes mellitus (IDDM) in nonobese diabetic (NOD) mice. Administration of interleukin 12 (IL-12), a key cytokine which guides the development of T helper type 1 (Th1) CD4+ T cells, induces rapid onset of IDDM in NOD, but not in BALB/c mice. Histologically, IL-12 administration induces massive infiltration of lymphoid cells, mostly T cells, in the pancreatic islets of NOD mice. CD4+ pancreas-infiltrating T cells, after activation by insolubilized anti T cell receptor antibody, secrete high levels of interferon gamma and low levels of IL-4. Therefore, IL-12 administration accelerates IDDM development in genetically susceptible NOD mice, and this correlates with increased Th1 cytokine production by islet-infiltrating cells. These results hold implications for the pathogenesis, and possibly for the therapy of IDDM and of other Th1 cell-mediated autoimmune diseases.

Physiology and pathophysiology of heart rate and blood pressure variability in humans: is power spectral analysis largely an index of baroreflex gain?

1. It is often assumed that the power in the low- (around 0.10 Hz) and high-frequency (around 0.25 Hz) bands obtained by power spectral analysis of cardiovascular variables reflects sympathetic and vagal tone [corrected] respectively. An alternative model attributes the low-frequency band to a resonance in the control system that is produced by the inefficiently slow time constant of the reflex response to beat-to-beat changes in blood pressure effected by the sympathetic (with or without the parasympathetic) arm(s) of the baroreflex (De Boer model). 2. We have applied the De Boer model of circulatory variability to patients with varying baroreflex sensitivity to patients with varying baroreflex sensitivity and one normal subject, and have shown that the main differences in spectral power (for both low and high frequency) between and within subjects are caused by changes in the arterial baroreflex gain, particularly for vagal control of heart rate (R-R interval) and left ventricular stroke output. We have computed the power spectrum at rest and during neck suction (to stimulate carotid baroreceptors). We stimulated the baroreceptors at two frequencies (0.1 and 0.2 Hz), which were both distinct from the controlled respiration rate (0.25 Hz), in both normal subjects and heart failure patients with either sensitive or poor baroreflex control. 3. The data broadly confirm the De Boer model. The low-frequency (0.1 Hz) peak in either R-R or blood pressure variability) was spontaneously generated only if the baroreflex control of the autonomic outflow was relatively intact.(ABSTRACT TRUNCATED AT 250 WORDS)

A 12-transistor PFM demodulator for analog neural networks communication

Pulse frequency modulation (PFM) provides robust long-distance communication and event-driven access to the communication channel. A PFM demodulator small and simple enough to equip every cell of a large analog neural network is analyzed. The circuit can demodulate PFM signals with pulse rates as low as 1 kHz using the switched-capacitor technique. Measurement results from integrated demodulators are presented.