P35 A RARE CASE OF VENTRICULAR ARRHYTHMIA STORM AND COMPLETE ATRIOVENTRICULAR BLOCK IN A PATIENT WITH BECKER MUSCULAR DYSTROPHY

A 68 year–old male presented to the Emergency Department of our Institute with palpitations for the last 20 minutes. The patient suffered from Becker’s muscular dystrophy (BMD) with hypotonic tetraparesis and dilated cardiomyopathy with moderate left ventricular dysfunction. The patient had also arterial hypertension and a previous ischemic stroke treated with thrombolysis and subsequently with warfarin. On the admission, the patient was alert, blood pressure was 90/60 mmHg and heart rate 180 bpm. An ECG (Fig. 1) showed regular, wide–complex tachycardia (QRS duration of 240 msec) with right branch block morphology with left axial deviation. A bolus of amiodarone 200 mg ev was administered without efficacy followed by a bolus of lidocaine 50 mg. The patient developed symptomatic hypotension, so external electrical cardioversion was performed with a single DC shock at 200J, effective in restoring sinus rhythm. Amiodarone and beta blocker therapy was started. On laboratory tests, the main values were normal, including the ultrasensitive troponin hs–cTnI. Echocardiography showed a mildly dilated left ventricle with diffuse hypokinesia conditioning severe reduction of systolic function (FE 35%) (Fig. 2). On subsequent telemetric ECG monitoring, no recurrences of sustained ventricular tachycardia (VT) were recorded, but it was observed an episode of complete atrioventricular (AV) block conditioning a symptomatic 9.5–second asystole, treated with atropine. Then the patient underwent CRT–D implantation in secondary prevention. The day after the procedure, an arrhythmic storm occurred and was effectively treated with multiple attempts of antitachycardia pacing and device shock. In the following days, the patient continued to present with episodes of VT despite antiarrhythmic drugs. Hence, an endo–epicardial ablation of the arrhythmic substrate was evaluated in Heart team. In view of an intubation and the high anesthesiological risk, it was indicated to continue the optimized medical therapy. Mexiletine 200 mg tid was added to metoprolol 100 mg bid and amiodarone 200 mg od. In the following days, no arrhythmic recurrences were recorded on continuous ECG monitoring. The patient was discharged from the hospital asymptomatic and with no sign of heart failure. At 2 years of follow–up, the patient remained asymptomatic, with no arrhythmic events recorded by the device and in the absence of any adverse effects caused by mexiletine.

Cardiac care of Non-COVID-19 patients during the SARS-CoV-2 pandemic: The pivotal role of CCTA

Funding Acknowledgements

Type of funding sources: None.

Aims

To describe the role of coronary CT angiography (CCTA) as the sole available non-invasive diagnostic test for symptomatic patients with suspected CAD in a hub center for cardiovascular emergencies in the presence of limited access to hospital facilities during the COVID-19 pandemic.

Methods and Results

From March 9th to April 30th, during the peak of the COVID-19 pandemic, a consecutive cohort of symptomatic patients with high clinical suspicion of CAD and clinical indication to CCTA were enrolled in a hub hospital in Milan, Italy. When obstructive coronary artery disease was detected (>70% diameter stenosis in a proximal coronary segment or >90% stenosis in any coronary segment) patients were referred to invasive coronary angiography (ICA). Clinical follow-up was assessed in patients in whom ICA was considered deferrable.

Overall, 58 consecutive patients were included. Ten (17.2%) symptomatic patients underwent ICA according to CCTA findings, while in 48 (82.8%) patients ICA was deferred. No clinical events were recorded after a mean follow-up of 49.7 ± 16.8 days. In nine out of ten patients referred to ICA, severe coronary artery disease was confirmed and treated accordingly. Changes in medical therapy were significantly more prevalent in patients with vs. those without CAD at CCTA.

Conclusion

We report a potential pivotal role for CCTA in the triage of non-COVID-19 patients with suspected  CAD during the SARS-CoV-2 pandemic. CCTA may be helpful for identifying patients who necessitate ICA, ensuring adequate resource utilization during the pandemic.

The impact of renal function on the incidence and prognosis of new-onset atrial fibrillation in acute myocardial infarction

Introduction

Atrial fibrillation (AF) is a frequent complication of acute myocardial infarction (AMI) and is associated with a worse prognosis. Patients with chronic kidney disease are more likely to develop AF. Whether the association between AF and renal function is also true in AMI has never been investigated.

Purpose

The aim of the study was to assess the incidence of new-onset AF according to renal function, estimated at hospital admission, and its relationship with short-term outcome and long-term all-cause mortality in a large real-world cohort of AMI patients.

Methods

We prospectively enrolled 2,445 AMI patients. New-onset AF was recorded during hospitalization. Glomerular filtration rate (eGFR) was estimated at admission and patients were grouped according to their renal function (group 1 [n=1,887]: eGFR>60; group 2 [n=492]: eGFR 60–30; group 3 [n=66]: eGFR<30 ml/min/1.73m2). The primary endpoint was AF incidence. In-hospital and long-term (median 5 years) all-cause mortality were the secondary endpoints.

Results

The AF incidence in the whole population was 10% and it was associated with a higher in-hospital (5% vs. 1%; P<0.0001) and long-term mortality (34% vs. 13%; P<0.0001). The AF incidence was 8%, 16%, 24% in groups 1, 2, 3, respectively (P<0.0001). In each group, in-hospital mortality was higher in AF patients (3.5% vs. 0.5%, 6.5% vs. 3.0%, 19% vs. 8%, respectively; P<0.0001). A similar trend was observed for long-term mortality (20% vs. 9%, 51% vs. 24%, 81% vs. 50%, respectively; P<0.0001). The higher risk for in-hospital and long-term mortality associated with AF in each group was confirmed also after adjustment for major confounders.

Conclusions

The study demonstrates that the incidence of new-onset AF during AMI, as well as its associated in-hospital and long-term mortality, increases in parallel with the severity of renal dysfunction assessed at hospital admission.

Funding Acknowledgement

Type of funding source: Private hospital(s). Main funding source(s): Centro Cardiologico Monzino, IRCCS, Milan, Italy

Circulatory response to fluid overload removal by extracorporeal ultrafiltration in refractory congestive heart failure

OBJECTIVES

The goal of this study was to investigate the hemodynamic and circulatory adjustments to extracorporeal ultrafiltration (UF) in refractory congestive heart failure (rCHF).

BACKGROUND

In rCHF, UF allows clinical improvement and restores diuretic efficacy. However, in the course of a UF session, patients are exposed to rapid variations of body fluid composition so that, as fluid is withdrawn from the intravascular compartment, hypotension or even shock could occur.

METHODS

In 24 patients with rCHF undergoing UF, we measured, after every liter of plasma water removed, hemodynamics, blood gas analysis (in both systemic and pulmonary arteries), plasma volume changes (PV) and plasma refilling rate (PRR). The PV and PRR were calculated by considering hematocrit and ultrafiltrate volume.

RESULTS

In all patients, UF was performed safely, without side effects or hemodynamic instability (ultrafiltrate = 4,880 +/- 896 ml). Mean right atrial, pulmonary artery and wedge pressures progressively reduced during the procedure. Cardiac output increased at the end of the procedure and, to a greater extent, 24 h later, in relation to the increase of stroke volume. Heart rate and systemic vascular resistance did not increase, and other peripheral biochemical parameters did not worsen during UF. Intravascular volume remained stable throughout the entire duration of the procedure, indicating that a proportional volume of fluid was refilled from the congested parenchyma.

CONCLUSIONS

In patients with rCHF, subtraction of plasma water by UF is associated with hemodynamic improvement. Fluid refilling from the overhydrated interstitium is the major compensatory mechanism for intravascular fluid removal, and hypotension does not occur when plasma refilling rate is adequate to prevent hypovolemia.

Comparison of enoxaparin and unfractionated heparin on thrombin generation in acute coronary syndromes without ST-segment elevation

Recent clinical trials have demonstrated a better ability of low-molecular-weight heparin, compared to unfractionated heparin, in reducing ischemic cardiac events in patients with acute coronary syndromes without ST-segment elevation. No data are available concerning the in-vivo comparison of enoxaparin and unfractionated heparin on thrombin generation in patients with unstable angina or non-Q-wave myocardial infarction. We measured the plasma levels of prothrombin fragment 1+2 (a marker of prothrombin activation) and thrombin/antithrombin complex (a marker of thrombin generation) in 45 patients with non ST-elevation acute coronary syndromes who were randomized to receive enoxaparin, 3000 IU anti-Xa as an i. v. bolus, followed by 70 IU anti-Xa/Kg every 8 h for 3 days (23 pts. Group 1) or a bolus of 100 IU/kg of unfractionated heparin followed by infusion for 3 days titrated to maintain the aPTT between 70 and 90 s (22 pts, Group 2). Plasma levels of prothrombin fragment 1+2 reduced significantly at 3rd h of treatment in both groups (-42% in Group 1 and -45% in Group 2), reached the lowest plasma concentration at the 24th h and exhibited a slight increase at the 72nd h; no differences were observed between the two groups at any time points. Plasma thrombin/antithrombin complex levels had a similar behaviour: reduced markedly in both groups at the 3rd h (-52% in Group 1 and -46% in Group 2), remained lower during the first two days and slightly rose at 72nd h. No differences between the two groups in plasma levels of this marker were apparent during drug infusion. In Group 1 the aPTT did not show significant changes: in Group 2 the mean value of aPTT doubled the basal value at any time point of determination. Both enoxaparin and unfractionated heparin produced a marked and similar reduction of thrombin generation. Other unknown mechanisms might explain the different clinical effects of the two heparins.

Cardiac and renal dysfunction in chronic heart failure: relation to neurohumoral activation and prognosis

BACKGROUND

In chronic heart failure (CHF), cardiac dysfunction is considered the major determinant of neurohumoral activation but the role of renal impairment has not been defined. We investigated the relationship between both cardiac and renal dysfunction and neurohumoral activation, and their possible influence on prognosis.

METHODS

Hemodynamics, renal function, plasma neurohormones, and long-term follow-up were evaluated in 148 CHF patients, grouped according to systolic volume index (SVI) and serum creatinine (CRE) values: SVI > 28 mL/m2 and CRE < 1.5 mg/dL (group I, n = 55), SVI < 28 mL/m2 and CRE < 1.5 mg/dL (group II, n = 37), SVI > 28 mL/m2 and CRE > 1.5 mg/dL (group III, n = 25), SVI < 28 mL/m2 and CRE > 1.5 mg/dL (group IV, n = 31).

RESULTS

Neurohormones progressively increased from Group I through IV and correlated with both cardiac and renal function. The hemodynamic pattern was similar in patients with normal or abnormal renal function, whereas neurohormones were only moderately increased in the former group and markedly increased in the latter group. Long-term survival progressively decreased from Group I through IV and was significantly poorer in patients with renal dysfunction.

CONCLUSIONS

Our study confirms that, in CHF, neurohumoral activation is strictly related to long-term survival and that many factors contribute to its development and progression; among these, cardiac and renal dysfunction seem to play a major role.

The noradrenaline plasma concentration and its gradient across the lung

BACKGROUND

We investigated the lung contribution to circulating noradrenaline (NA) homeostasis. Evaluation of the transpulmonary NA gradient, related to the NA amount entering the lungs, is potentially important, mainly regarding clinical conditions, such as congestive heart failure (CHF), that are associated with excessive circulating NA.

MATERIALS AND METHODS

15 moderate (group 1) and 15 severe (group 2) CHF patients, and 10 normal individuals had determination of NA transpulmonary gradient in the baseline and during rise (exercise, in normals and group 1) or fall (withdrawal from plasma by ultrafiltration, in group 2) of plasma NA.

RESULTS

NA gradient (pg mL(-1)) at rest was 30 +/- 3 in normals, 21 +/- 6 in group 1 and 5 +/- 8 in group 2. Increase of NA concentration in the mixed venous blood with exercise was paralleled by depression of the transpulmonary gradient. Pulmonary arteriovenous difference disappeared when NA entering the lungs averaged 1300 pg mL(-1). In group 2, ultrafiltration lowered NA in the mixed venous blood from 1225 +/- 213 to 718 +/- 182, which caused transpulmonary gradient to increase from 5 +/- 8 to 22 +/- 9.

CONCLUSIONS

Transpulmonary gradient of NA diminishes when NA entering the lungs increases, and 1300 pg mL(-1) in the pulmonary artery is, both in patients and normal subjects, the level at which gradient disappears; which likely reflects cessation of NA uptake or achievement of a balance between lung uptake and production. This may have physiological and pathological implications.

[Intra- and extravascular volumes in congestive heart failure and their redistribution following extracorporeal ultrafiltration]

In advanced congestive heart failure with fluid retention, extracorporeal ultrafiltration (UF) causes persistent relief of edema or anasarca through hemodynamic and humoral changes that interrupt refractoriness to diuretics. The intra and extravascular fluid partition in congestive heart failure, as well as changes occurring in the two compartments following fluid withdrawal with UF, are unknown. In 8 congestive heart failure patients with severe fluid retention undergoing UF, we measured total (TBV), intrathoracic (ITBV) and pulmonary blood volumes (PBV), and extravascular lung water (EVLW). The intra and extravascular volumes were evaluated by a fiberoptic thermal dye dilution monitoring system, before, at the end of UF (3697 +/- 699 ml) and 24 hours later. Baseline data were compared with those of 10 subjects without heart failure undergoing coronary bypass surgery. In congestive heart failure patients, as compared with controls, TBV was normal, the intrathoracic blood content (ITBV, PBV and PBV/TBV ratio) was increased and EVLW was normal. UF did not induce significant changes in TBV and in EVLW, and reduced ITBV, PBV and PBV/TBV ratio, suggesting that a shift of fluid from the intra to the extrathoracic intravascular compartment occurred. Because both TBV and EVLW were not affected by the procedure, the largest proportion of fluid removed by UF derived from the systemic extravascular space. Both pulmonary wedge and right atrial pressures significantly decreased after UF, and cardiac output increased. In conclusion, congestive heart failure is associated with normal TBV and EVLW content and with intravascular intrathoracic hypervolemia and extrathoracic hypovolemia. UF induces hemodynamic improvement through a selective fluid removal from the extravascular systemic space without changes in both TBV and EVLW.

[Platelet activation in the early phases of acute myocardial infarction]

Myocardial infarction and thrombolysis are proven to be associated with platelet activation. However, the time relationship of platelet activation with the onset of symptoms and with thrombolysis, and the response to aspirin are not well defined. In this study we measured platelet activity in the early phase of myocardial infarction treated with either streptokinase or recombinant tissue-type plasminogen activator (rt-PA) and evaluated whether and to what extent it may be counteracted by aspirin. Fourty-one patients (mean age 57 +/- 6 years) received thrombolytic therapy after coronary occlusion: 1.5 million units of streptokinase (Group 1; 21 patients) or 100 mg of rt-PA (Group 2; 20 patients). Ten randomly selected patients in either group were given 500 mg aspirin i.v. prior to infusion of the thrombolytic compound and, then, 325 mg/die of aspirin orally. Beta-thromboglobulin (BTG), a marker of platelet activity, was determined at admission, after thrombolysis and in the subsequent 48 hours. At admission, BTG plasma levels averaged 125 +/- 31 IU/ml in Group 1 and 134 +/- 35 IU/ml in Group 2 (NS). Thrombolysis produced a similar increase in platelet activity in both groups, and maximal values were reached at the third hour (196 +/- 43 IU/ml in Group 1 and 192 +/- 39 in Group 2, p < 0.001 vs baseline and NS between groups). Levels of BTG were higher in streptokinase-treated group starting from 24 hours (p < 0.05). Differences in BTG levels between aspirin-treated and aspirin-untreated patients became significant at 48 hours after thrombolysis in both groups. An inverse correlation was found between time elapsed from onset of symptoms and BTG value on admission (r = -0.86, p < 0.001); in patients admitted within 2 hours after the beginning of symptoms, and having the higher BTG levels, thrombolysis did not induce a significant increase in platelet activity; this, on the contrary, was observed in patients admitted later. Platelet activation is greater early after myocardial infarction and is differently influenced by thrombolytic treatment, depending on the delay of the patient's admission. Streptokinase and rt-PA induce a similar increase in platelet activity which is more persistent after streptokinase; cycloxygenase inhibition with aspirin seems to influence platelet activity only starting from the second day.

Thrombin activation and late restenosis after percutaneous transluminal coronary angioplasty

BACKGROUND

Mechanisms of restenosis after percutaneous transluminal coronary angioplasty (PTCA) have not been defined yet. Experimental studies have shown that thrombin, by stimulating platelet growth factor secretion and smooth muscle cell proliferation, can play a major role.

METHODS AND RESULTS

In 34 patients with single-vessel coronary disease undergoing PTCA, thrombin activity was evaluated through serial fibrinopeptide A (FPA) plasma determinations. Samples were performed before PTCA, immediately after and 24 hours, 72 hours, and 6 months later. Patients were grouped according to the development (group 1, n = 13) or nondevelopment (group 2, n = 21 ) of restenosis at a 6-month angiographic control. No difference in the two groups was found concerning baseline FPA values. In patients in group 1, soon after PTCA higher FPA levels (27.3 +/- 13.7 ng/ml) than those in group 2 (9.2 +/- 5.6 ng/ml; p < 0.05 vs pre-PTCA, and p < 0.01 between the two groups) were observed. No differences in FPA levels were detected at the other steps between the two groups.

CONCLUSION

Our data suggest that thrombin plays a role in the process of restenosis after PTCA; acute FPA response to the procedure seems to have a predictive value.

[The influence of ACE inhibitors on urinary electrolyte secretion and the response to transitory hypovolemia in chronic heart failure]

Renin-angiotensin system promotes sodium and chloride retention, participates in the defense response to hypovolemia and, in congestive heart failure, contributes to edema formation and progression of the disease. We investigated whether ACE-inhibitors interfere with the action of the renin-angiotensin system on the nephron, and therefore with water and urinary electrolytes excretion. The interaction among renin-angiotensin system, diuretic treatment and urinary electrolytes was evaluated both during chronic treatment and in response to acute renin-angiotensin system activation as that observed after extracorporeal ultrafiltration-induced transient hypovolemia. Plasma renin activity and aldosterone, body fluid balance and urinary sodium, chloride and potassium concentrations were evaluated in 30 patients with congestive heart failure in NYHA II-III functional class, grouped according to whether long-term therapy did not include (Group I, n = 15) or included (Group II, n = 18) ACE-inhibitors. All parameters were evaluated at baseline and after a single session of extracorporeal ultrafiltration. At baseline, urinary output and urinary sodium and chloride concentrations were similar in the two groups, while urinary potassium concentration was lower in patients assuming ACE-inhibitors (Group II). Plasma renin activity was higher and aldosterone was lower in Group II than in Group I. After removal of similar amounts of plasma water by extracorporeal ultrafiltration, body weight decreased in both groups but the decrease was maintained in the following days only in Group II patients. A transient reduction (48 hours) of both plasma volume and urinary output was observed after ultrafiltration in both groups. Despite plasma renin activity and aldosterone increase, urinary electrolytes response to ultrafiltration was different in the two groups: sodium and chloride were reduced, and potassium did not change in Group 1 while, in Group II, sodium and chloride did not change and potassium excretion was significantly increased. In conclusion, chronic treatment with ACE-inhibitors does not enhance the excretion of sodium in congestive heart failure but just mitigates potassium loss. The role of these drugs becomes particularly relevant during acute renin-angiotensin system activation due to hypovolemia; in this setting ACE-inhibitors counteract sodium and chloride retention resulting in a potential hazard due to interference with the defence mechanisms toward hypovolemia, and an amplification of extracorporeal ultrafiltration efficacy by preventing edema recovery after its mechanical removal.

[Mechanisms facilitating oxygen delivery during exercise in patients with chronic heart failure]

The aim of the study was to estimate the relative importance of the Bohr effect and redistribution of blood from the non-exercising tissues on the arterial-venous oxygen content differences across the exercising extremities and the central circulation in patients with chronic heart failure; the relationship among femoral vein, systemic and pulmonary artery oxygen partial pressure and hemoglobin saturation was determined. It has been reported that the maximal reduction in femoral vein pO2 precedes peak oxygen consumption and lactic acidosis threshold in patients with chronic heart failure and normal subjects during exercise. The increase in oxygen consumption at work rates above lactic acidosis threshold, therefore, must be accounted for by increase in blood flow in the exercising muscles and right-ward shift on the oxyhemoglobin dissociation curve. Since the total cardiac output increase is blunted in patients with chronic heart failure, diversion of blood flow from non-exercising to exercising tissues may account for some of the increase in muscle blood flow. Ten patients with chronic heart failure performed a progressively increasing leg cycle ergometer exercise test up to maximal effort while measuring ventilation and gas concentration for computation of oxygen uptake and carbon dioxide production, breath-by-breath. Blood samples were obtained, simultaneously, from systemic and pulmonary arteries and femoral vein at rest and every minute during exercise to peak oxygen consumption. At comparable levels of exercise, femoral vein pO2, hemoglobin saturation and oxygen content were lower than in the pulmonary artery. PCO2 and lactate concentration increased steeply in femoral vein and pulmonary artery blood above lactic acidosis threshold (due to lactic acid build-up and buffering), but more steeply in femoral vein blood. These increases allowed femoral vein oxyhemoglobin to dissociate without a further decrease in femoral vein pO2 (Bohr effect). The lowest femoral vein pO2 (16.6 +/- 3.9 mmHg) was measured at 66 +/- 22% of peak VO2 and before the lowest oxyhemoglobin saturation was reached. Artero-venous oxygen content difference was higher in the femoral vein than in the pulmonary artery; this difference became progressively smaller as oxygen consumption increased. "Ideal" oxygen consumption for a given cardiac output (oxygen consumption expected if all body tissues had maximized oxygen extraction) was always higher than the measured oxygen consumption; however the difference between the two was lost at peak exercise. This difference positively correlated with peak oxygen consumption and cardiac output increments at submaximal but not at maximal exercise. In conclusion, femoral vein pO2 reached its lowest value at a level of exercise at or below the lactic acidosis threshold. Further extraction of oxygen above the lactic acidosis threshold was accounted for by a right shift of the oxyhemoglobin dissociation curve. The positive correlation between increments of cardiac output vs "ideal" and measured oxygen consumption suggests a redistribution of blood flow from non-exercising to exercising regions of the body. Furthermore the positive correlation between exercise capacity and the difference between "ideal" and measured oxygen consumption suggests that patients with the poorer function have the greater capability to optimize blood flow redistribution during exercise.

Oxygen transport to muscle during exercise in chronic congestive heart failure secondary to idiopathic dilated cardiomyopathy

In chronic heart failure, oxygen delivery during exercise is impaired mainly because of failure of cardiac output to increase normally. Compensatory mechanisms are hemoglobin concentration increase, right-ward shift in the oxyhemoglobin dissociation curve, and blood flow redistribution from the nonexercising organs to the exercising muscles.

Contribution of PO2, P50, and Hb to changes in arteriovenous O2 content during exercise in heart failure

Arteriovenous O2 content (a-vCO2) differences increase during exercise in normal subjects through several mechanisms including PO2, O2 pressure at which hemoglobin (Hb) is half saturated with O2 (P50), and Hb concentration changes. The present study was undertaken to evaluate how much these biochemical changes are relevant to a-vCO2 difference through exercise in patients with heart failure. Twenty-seven patients with congestive heart failure [10 patients in functional class A (peak exercise O2 uptake >20 ml x kg-1 x min-1), 9 in class B (20-15 ml x kg-1 x min-1), and 8 in class C (15-10 ml x kg-1 x min-1)] underwent a cardiopulmonary exercise test with once-per-minute simultaneous blood sampling from the pulmonary and systemic arteries for determination of Hb, PO2, PCO2, pH, O2 content (CO2), Hb saturation and lactic acid (pulmonary artery only), and calculation of P50. Analysis of data was done at six exercise stages: the first at rest, the last at peak exercise, and the second to the fifth at one-, two-, three-, and four-fifths of O2 consumption increase. a-vCO2 difference at peak exercise was 14.3 +/- 2.1, 16.9 +/- 2.4, and 14.7 +/- 2.1 (SD) ml/dl in class A, B, and C patients, respectively. The contribution of Hb, P50, and PO2 changes to the increments of a-vCO2 difference during exercise was 21, 17, and 63%, respectively; the only interclass difference observed was for P50, which plays a greater role in a-vCO2 difference in class A. Hb changes act mainly at the arterial site, whereas P50 and PO2 act at the venous site. Hb increase was constant through the test, venous P50 increase was greater above anaerobic threshold, and venous PO2 reduction was most remarkable at the onset of exercise; in class C patients, no venous PO2 change was recorded in the second half of exercise. Thus a-vCO2 difference increase during exercise is notable in patients with heart failure but unrelated to the severity of the syndrome. Hb, P50, and, to the greatest degree, PO2 changes participate in the increment of a-vCO2 difference. In class C patients, the lack of PO2 reduction in the second half of exercise suggests the achievement of a "whole body critical venous PO2."

Evaluation of the dead space/tidal volume ratio in patients with chronic congestive heart failure

Dead space/tidal volume ratio (VD/VT) evaluation is currently performed in patients with respiratory and cardiac disorders, and includes measurement of arterial CO2 partial pressure (PaCO2). PaCO2 is generally derived from either PETCO2 (end-expiratory CO2 pressure) or PJCO2 (calculated as PJCO2 = 5.5 + 0.9 PETCO2 - 2.1 VT). The applicability of these methods may be questionable in chronic heart failure due to its frequent association with lung dysfunction. In 63 patients with congestive heart failure, the authors compared PaCO2 versus PETCO2 and PJCO2 and VD/VT measured with PaCO2 versus VD/VT estimated with PETCO2 (estimation 1) or PJCO2 (estimation 2). Comparisons were made at rest, at submaximal exercise, and at peak exercise. Considering all 326 measurements, there was a strong correlation, but not an identity, between PaCO2 and PETCO2 (PaCO2 = 7.25 + 0.80 PETCO2, r = .84, P < .0001) and between PaCO2 and PJCO2 (PaCO2 = 6.18 + 0.84 PJCO2, r = .85, P < .0001). Results were comparable concerning PaCO2 versus PJCO2. Measured VD/VTs also strongly correlated with estimated VD/VTs (VD/VT measured = -0.03 + 1.11 VD/VT [estimation 1], r = .90, P < .0001, and VD/VT measured = 0.03 + 0.92 VD/VT [estimation 2], r = .90, P < .0001). However, only at rest and, solely for estimation 1, at submaximal exercise were the slopes and y intercepts of measured versus estimated VD/VT not different from 1 and 0, respectively; in this regard, lung dysfunction was more influential than the severity of cardiac failure. Although PaCO2 strongly correlates with PETCO2 and PJCO2, these measurements may not be reliable for a noninvasive calculation of VD/VT in chronic congestive heart failure.

Lung-heart interaction as a substrate for the improvement in exercise capacity after body fluid volume depletion in moderate congestive heart failure

We investigated exercise capacity after fluid depletion in patients with moderate congestive heart failure (CHF). Twenty-one patients underwent ultrafiltration (mean volume +/- SEM: 1,770 +/- 135 ml). Echocardiography, tests of pulmonary function, and a cardiopulmonary exercise test with hemodynamic and esophageal pressure monitoring were performed before ultrafiltration and 3 months later. Tests without invasive measurements were repeated 4 and 30 days after ultrafiltration. Twenty-one control patients followed the same protocol but did not have ultrafiltration. Patients who underwent ultrafiltration and increased their oxygen consumption at peak exercise (peak VO2) by > 10% at the 3-month evaluation (group A1, n = 9) were separated from those who did not (group A2, n = 8); 3 patients did not complete the follow-up. Four days after the procedure, peak VO2 had risen from 17.3 +/- 0.8 to 19.3 +/- 0.9 ml/min/kg in group A1, and from 11.9 +/- 0.7 to 14.1 +/- 0.7 ml/min/kg in group A2 (p < 0.01). Plasma norepinephrine and pulmonary function were consistent with a greater severity of the syndrome in group A2. At 3 months in group A1, the relations of filling pressure to cardiac index of the right and left ventricles were shifted upward; the esophageal pressure swing (differences between end-expiratory and end-inspiratory pressure) for a given tidal volume was lower; the peak exercise dynamic lung compliance had increased from 0.10 +/- 0.05 to 0.14 +/- 0.03 L/mm Hg (p < 0.01). None of these changes were detected in group A2 and control patients.(ABSTRACT TRUNCATED AT 250 WORDS)

[Moderate cardiac failure: oxygen consumption during exercise predicts ultrafiltration results]

Extracorporeal ultrafiltration (UF) can improve the clinical condition, as assessed by cardiopulmonary exercise evaluation, of patients with moderate heart failure (HF); the pre-UF level of physical performance above which UF does not induce clinical benefits, is not defined. For this purpose, we studied 29 patients with stable HF in functional class II-III (NYHA), who underwent UF (veno-venous bypass, removal of 1,830 +/- 550 ml of plasma water), regardless their baseline oxygen consumption at peak exercise (VO2p) and at anaerobic threshold (VO2AT). All patients experienced cardiopulmonary exercise tests (cycloergometer, increasing workloads of 25 W every 3 min) before (pre-UF), and 4 days and 3 months following UF. According to VO2 changes following UF 2 groups of patients were identified: in Group I (9 patients) no differences in VO2p and VO2AT were observed, while in Group II (18 patients) VO2p rose by 2.7 ml/min/kg (p < 0.001) at 4 days and 4.5 ml/min/kg (p = 0.04) at 3 months, and VO2AT rose by 1.2 ml/min/kg (p < 0.001) at 4 days and 2.8 ml/min/kg (p = 0.03) at 3 months. In unresponsive patients baseline values of VO2p > or = 18 ml/min/kg and VO2AT +/- 13 ml/min/kg were detected. Pre-UF VO2p inversely correlated with the shift of VO2p (delta VO2p) both at 4 days (r = -0.62, p < 0.001) and at 3 months (r = -0.53, p = 0.005), and pre-UF VO2AT inversely correlated with delta VO2AT at 4 days (r = -0.71, p < 0.001) and at 3 months (r = -0.63, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)