Impact of beta-blocker treatment on the prognostic value of currently used risk predictors in congestive heart failure

OBJECTIVES

This prospective study tested the impact of beta-blocker treatment on currently used risk predictors in congestive heart failure (CHF).

BACKGROUND

Given the survival benefit obtained by beta-blockade, risk stratification by factors established in the "pre-beta-blocker era" may be questioned.

METHODS

The study included 408 patients who had CHF with left ventricular ejection fraction (LVEF) <45%, all treated with an angiotensin-converting enzyme inhibitor or angiotensin type 1 receptor antagonist, who were classified into those receiving a beta-blocker (n = 165) and those who were not (n = 243). In all patients, LVEF, peak oxygen consumption (peakVO(2)), plasma norepinephrine (NE) and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were determined.

RESULTS

Although the New York Heart Association functional class (2.2 +/- 0.7 vs. 2.3 +/- 0.7), peakVO(2) (14.4 +/- 5.2 ml/min per kg vs. 14.4 +/- 5.5 ml/min per kg) and NT-proBNP (337 +/- 360 pmol/l vs. 434 +/- 538 pmol/l) were similar in the groups with and without beta-blocker treatment, the group with beta-blocker treatment had a lower heart rate (68 +/- 30 beats/min vs. 76 +/- 30 beats/min), lower NE (1.7 +/- 1.2 nmol/l vs. 2.5 +/- 2.2 nmol/l) and higher LVEF (24 +/- 10% vs. 21 +/- 9%; all p < 0.05). Within one year, 34% of patients without beta-blocker treatment, but only 16% of those with beta-blocker treatment (p < 0.001), reached the combined end point, defined as hospital admission due to worsening CHF and/or cardiac death. A beneficial effect of beta-blocker treatment was most obvious in the advanced stages of CHF, because the end-point rates were markedly lower (all p < 0.05) in the group with beta-blocker treatment versus the group without it, as characterized by peakVO(2) <10 ml/min per kg (26% vs. 64%), LVEF < or = 20% (25% vs. 45%), NE >2.24 nmol/l (18% vs. 40%) and NT-proBNP >364 pmol/l (27% vs. 45%), although patients with beta-blocker treatment received only 37 +/- 21% of the maximal recommended beta-blocker dosages.

CONCLUSIONS

The prognostic value of variables used for risk stratification of patients with CHF is markedly influenced by beta-blocker treatment. Therefore, in the beta-blocker era, a re-evaluation of the selection criteria for heart transplantation is warranted.

Central hypercapnic chemoreflex modulation of renal sympathetic nerve activity in experimental heart failure

Activation of the sympathetic nervous system plays an important role in the pathophysiology and progression of congestive heart failure (CHF). The precise mechanisms responsible for sympathetic activation in CHF are not yet clearly established. An altered central hypercapnic chemoreflex modulation of sympathetic nerve activity (SNA) might be an explanation. Therefore, the response of postganglionic renal SNA to elevation of CO2 concentration in the inspiratory air to 2, 4, and 6% was determined in anesthetized, artificially ventilated rats after denervation of peripheral baro- and chemoreceptors 2 weeks (group A; n=8) or 6 weeks (group B; n=11) after induction of an aorto-caval shunt, or 4 weeks after aortic banding (group C; n=7). In all CHF models, left ventricular enddiastolic pressure was increased (A 8 +/- 1, B 8 +/- 1, C 10 +/- 2 mmHg) as compared to sham operated controls (A 3 +/- 1, B 4 +/- 1, C 5 +/- 1 mmHg). Indicative of left ventricular hypertrophy and pulmonary congestion, wet weight of heart (A + 60%, B + 93%, C + 49%) and lungs (A + 15%, B + 36%, C + 12%) were also enhanced as compared to controls. Elevation of inspiratory CO2 concentration to 2,4, and 6% increased renal SNA by approximately 10, 20, and 30% from resting activity in all groups. The maximum SNA responses at 6% CO2 in the groups with CHF (A + 390 +/- 95, B + 425 +/- 133, C + 368 +/- 158 microVs) did not differ from those in the respective controls (A + 510 +/- 130, B + 570 +/- 180, C + 275 +/- 25 microVs). It is concluded that under these experimental conditions the central hypercapnic chemoreflex sensitivity is not altered in either of the employed models of CHF and therefore may not play a major role for the well-known elevation of SNA in CHF.

Differential effects of acidosis, high potassium concentrations, and metabolic inhibition on noradrenaline release and its presynaptic muscarinic regulation

It was the aim of the present study to characterize the effect of single components of ischaemia, such as inhibition of aerobic and anaerobic energy production by combined anoxic and glucose-free perfusion (metabolic inhibition), high extracellular potassium concentrations (hyperkalaemia), and acidosis, on (1). the stimulated release of noradrenaline from the in situ perfused guinea-pig heart and (2). its presynaptic modulation by the muscarinic agonist carbachol. The release of endogenous noradrenaline from efferent cardiac sympathetic nerve endings was induced by electrical stimulation of the left stellate ganglion (1 min, 5 V, 12 Hz) and quantified in the coronary venous effluent by high-performance liquid chromatography. Under control conditions, two consecutive electrical stimulations (S1, S2) elicited a similar noradrenaline overflow (S2/S1: 0.98 plus minus 0.05). After 10 min of global myocardial ischaemia overflow of endogenous noradrenaline was significantly reduced (S2/S1: 0.18 plus minus 0.03; P< 0.05). When studied separately, metabolic inhibition, hyperkalaemia (16 mM), and acidosis (pH 6.0) each markedly attenuated stimulated noradrenaline overflow (S2/S1: 0.65 plus minus 0.05, 0.43 plus minus 0.14, and 0.37 plus minus 0.09, respectively; P< 0.05). The muscarinic agonist carbachol (10 microM) inhibited stimulated noradrenaline release under normoxic conditions (S2/S1: 0.41 plus minus 0.07; P< 0.05). However, after 10 min of global myocardial ischaemia the inhibitory effect of carbachol on noradrenaline overflow was completely lost. Single components of ischaemia had a differential effect on presynaptic muscarinic modulation. Whereas hyperkalaemia (8-16 mM) did not affect muscarinic inhibition of noradrenaline release, carbachol lost its inhibitory effect during acidosis and metabolic inhibition. In conclusion, hyperkalaemia, metabolic inhibition, and severe acidosis each contribute to reduced overflow of noradrenaline after 10 min of myocardial ischaemia. However, presynaptic muscarinic inhibition of noradrenaline release was not affected by hyperkalaemia, but was sensitive to metabolic inhibition and low degrees of acidosis.

Health related quality of life in patients with congestive heart failure: comparison with other chronic diseases and relation to functional variables

OBJECTIVE

To assess health related quality of life of patients with congestive heart failure; to compare their quality of life with the previously characterised general population and in those with other chronic diseases; and to correlate the different aspects of quality of life with relevant somatic variables.

SETTING

University hospital.

PATIENTS AND DESIGN

A German version of the generic quality of life measure (SF-36) containing eight dimensions was administered to 205 patients with congestive heart failure and systolic dysfunction. Cardiopulmonary evaluation included assessment of New York Heart Association (NYHA) functional class, left ventricular ejection fraction, peak oxygen uptake, and the distance covered during a standardised six minute walk test.

RESULTS

Quality of life significantly decreased with NYHA functional class (linear trend: p < 0.0001). In NYHA class III, the scores of five of the eight quality of life domains were reduced to around one third of those in the general population. The pattern of reduction was different in patients with chronic hepatitis C and major depression, and similar in patients on chronic haemodialysis. Multiple regression analysis showed that only the NYHA functional class was consistently and closely associated with all quality of life scales. The six minute walk test and peak oxygen uptake added to the explanation of the variance in only one of the eight quality of life domains (physical functioning). Left ventricular ejection fraction, duration of disease, and age showed no clear association with quality of life.

CONCLUSIONS

In congestive heart failure, quality of life decreases as NYHA functional class worsens. Though NYHA functional class was the most dominant predictor among the somatic variables studied, the major determinants of reduced quality of life remain unknown.

Do cytokines enable risk stratification to be improved in NYHA functional class III patients? Comparison with other potential predictors of prognosis

AIMS

Elevated plasma levels of proinflammatory cytokines have been reported in patients with congestive heart failure. The purpose of this study was to assess whether cytokines improve risk stratification in a homogeneous group of NYHA class III patients with a left ventricular ejection fraction <40%.

METHODS AND RESULTS

Plasma concentrations of big endothelin, tumour necrosis factor alpha, interleukins -1, -6, -10 and -12, sCD14 and GM-CSF were measured by ELISA in 91 NYHA III patients [mean (SD) age: 55 (10) years, 69% male, 34% coronary artery disease, 66% dilated cardiomyopathy] with a left ventricular ejection fraction and a peak oxygen uptake (peak VO2) of 19 (9)% and 12.1 (3.6) ml x min(-1) x kg(-1), respectively. During follow-up [22 (13) months], 31 patients (34%) died due to cardiovascular causes. In non-survivors, interleukin-6 was twice as high as in survivors [12.8 (16.9) pg x ml(-1)vs 5.6(5.3) pg x ml(-1), P<0.003], whereas plasma concentrations of the other cytokines showed no significant differences. Concerning long-term survival (> or =1 year), multivariate Cox regression analysis revealed an independent prognostic power for interleukin-6, which was further improved by combining with left ventricular ejection fraction and peak VO2, while for short-term survival (up to 6 months) interleukin-6 did not allow risk stratification.

CONCLUSION

In NYHA class III patients, plasma concentrations of interleukin-6 are predictive of long-term survival. However, its value may be limited for clinical decision-making for cardiac transplantation (short-term survival).

Risk stratification in middle-aged patients with congestive heart failure: prospective comparison of the Heart Failure Survival Score (HFSS) and a simplified two-variable model

AIMS

The performance of a US-American scoring system (Heart Failure Survival Score, HFSS) was prospectively evaluated in a sample of ambulatory patients with congestive heart failure (CHF). Additionally, it was investigated whether the HFSS might be simplified by assessment of the distance ambulated during a 6-min walk test (6'WT) instead of determination of peak oxygen uptake (peak VO(2)).

METHODS AND RESULTS

In 208 middle-aged CHF patients (age 54+/-10 years, 82% male, NYHA class 2.3+/-0.7; follow-up 28+/-14 months) the seven variables of the HFSS: CHF aetiology; heart rate; mean arterial pressure; serum sodium concentration; intraventricular conduction time; left ventricular ejection fraction (LVEF); and peak VO(2), were determined. Additionally, a 6'WT was performed. The HFSS allowed discrimination between patients at low, medium and high risk, with mortality rates of 16, 39 and 50%, respectively. However, the prognostic power of the HFSS was not superior to a two-variable model consisting only of LVEF and peak VO(2). The areas under the receiver operating curves (AUC) for prediction of 1-year survival were even higher for the two-variable model (0.84 vs. 0.74, P<0.05). Replacing peak VO(2) with 6'WT resulted in a similar AUC (0.83).

CONCLUSION

The HFSS continued to predict survival when applied to this patient sample. However, the HFSS was inferior to a two-variable model containing only LVEF and either peak VO(2) or 6'WT. As the 6'WT requires no sophisticated equipment, a simplified two-variable model containing only LVEF and 6'WT may be more widely applicable, and is therefore recommended.

d,l-sotalol enhances baroreflex sensitivity in conscious rats surviving acute myocardial infarction

The aim of the present study was to characterize the influence of D,L-sotalol on arterial baroreflex sensitivity (BRS) which is generally considered as an estimate of vagal activity and has prognostic value in patients after myocardial infarction (MI). Conscious rats were studied 3 days after left anterior descending coronary artery ligation (n= 5) or sham-operation (SH, n= 6). BRS was determined by linear regression analysis of the RR-interval (interval between heart beats) and mean arterial pressure changes evoked by i.v. bolus injections of methoxamine (inducing reflex bradycardia, RB) and nitroprusside (inducing reflex tachycardia, RT). In MI-rats heart rate and mean arterial pressure were not significantly different from values in SH-rats, left ventricular end-diastolic pressure was increased and contractility was depressed. The BRS (RB: MI: 0.48 +/- 0.04(*), SH: 0.79 +/- 0.08; RT: MI: 0.41 +/- 0.05(*), SH: 0.86 +/- 0.08 ms mmHg(-1)) ((*)P< 0.05 vs SH) was markedly reduced. d, l -Sotalol (1.5 mg kg(-1)i.v.) reduced heart rate (MI: -11 +/- 3 %(*), SH: -11 +/- 3 %(*)) and mean arterial pressure only moderately [MI: -6 +/- 4 %(n.s.), SH: -7 +/- 2 %(*)], while BRS depression in MI-rats was completely neutralized [RB: MI: 1.08 +/- 0.14(*), SH: 1.19 +/- 0.11(*); RT: MI: 0.84 +/- 0.08(*), SH: 0.88 +/- 0.12 (n.s.) ms mmHg(-1)] ((*)P< 0.05 vs pretreatment). The BRS is reduced in rats early after MI, indicating a depressed reflex vagal activity. Treatment with D,L-sotalol at a dose with little effect on heart rate and mean arterial pressure markedly enhances and, thus, restores BRS in MI-rats. These data suggest that D,L-sotalol has both peripheral and central effects leading to an increase of reflex vagal control of heart rate in rats.

Recalibration of the point-of-care test for CARDIAC T Quantitative with Elecsys Troponin T 3rd generation

The rapid troponin T assay CARDIAC T Quantitative was recalibrated using Elecsys Troponin T 3rd Generation as a new reference method. This paper presents the method comparisons at six centres using the new reference method. Method comparison between CARDIAC T Quantitative versus Elecsys Troponin T 3rd Generation were performed using 319 samples from patients with acute coronary syndromes. The quality of the CARDIAC T Quantitative was controlled by a daily single determination of CARDIAC Control Troponin T, and for the Elecsys Troponin T 3rd Generation, the Elecsys controls were included in each run. The results for the control materials for the CARDIAC T Quantitative were between 93% and 107% of the target values. The CV ranged from 7% to 16%. From the regression analysis, according to Bablok and Passing (y=1.07x) and the Bland and Altman plot, the bias between CARDIAC T Quantitative and Elecsys Troponin T 3rd Generation is from +6% to +7%. The correlation coefficient is 0.93, and a 3x3 comparison of the clinical efficiency yielded 92% clinical concordance between CARDIAC T Quantitative and Elecsys Troponin T 3rd Generation. In conclusion, CARDIAC T Quantitative was in good agreement with the reference and calibration method Elecsys Troponin T 3rd Generation.

Respiratory muscle dysfunction in congestive heart failure: clinical correlation and prognostic significance

BACKGROUND

In congestive heart failure (CHF), the prognostic significance of impaired respiratory muscle strength has not been established.

METHODS AND RESULTS

Maximal inspiratory pressure (Pi(max)) was prospectively determined in 244 consecutive patients (207 men) with CHF (ischemic, n=75; idiopathic dilated cardiomyopathy, n=169; age, 54+/-11 years; left ventricular ejection fraction [LVEF], 22+/-10%). Pi(max) was lower in the 244 patients with CHF than in 25 control subjects (7.6+/-3.3 versus 10.5+/-3.7 kPa; P=0.001). The 57 patients (23%) who died during follow-up (23+/-16 months; range, 1 to 48 months) had an even more reduced Pi(max) (6.3+/-3.2 versus 8.1+/-3.2 kPa in survivors; P=0.001). Kaplan-Meier survival curves differentiated between patients subdivided according to quartiles for Pi(max) (P=0.014). Pi(max) was a strong risk predictor in both univariate (P=0.001) and multivariate Cox proportional hazard analyses (P=0.03); multivariate analyses also included NYHA functional class, LVEF, peak oxygen consumption (peak VO(2)), and norepinephrine plasma concentration. The areas under the receiver-operating characteristic curves for prediction of 1-year survival were comparable for Pi(max) and peak VO(2) (area under the curve [AUC], 0.68 versus 0.73; P=0.28), and they improved with the triple combination of Pi(max), peak VO(2), and LVEF (AUC, 0.82; P=0.004 compared with AUC of Pi(max)).

CONCLUSIONS

In patients with CHF, inspiratory muscle strength is reduced and emerges as a novel, independent predictor of prognosis. Because testing for Pi(max) is simple in clinical practice, it might serve as an additional factor to improve risk stratification and patient selection for cardiac transplantation.

Echocardiographic quantification of left ventricular asynergy in coronary artery disease with Fourier phase imaging

BACKGROUND

Visual evaluation of wall motion is subjective and may be difficult in patients with impaired left ventricular function. Current algorithms used to analyze wall motion usually neglect motion asynchrony that may be profoundly altered in coronary artery disease. This study was to investigate whether the extent of left ventricular asynergy can be used to quantify the severity of regional myocardial dysfunction by the use of Fourier phase imaging.

METHODS

Echocardiographic cine loops of 21 patients with ischemic cardiomyopathy (EF < or = 40%) were mathematically transformed using a first-harmonic Fourier algorithm displaying the sequence of wall motion as phase angles in parametric images and regional phase histograms. Segmental fractional area shortening (FAC) and qualitative assessment of regional wall motion based on visual inspection served as reference method.

RESULTS

There was an inverse linear relationship between FAC and phase angles (r = -0.75, p < 0.01). Normal endocardial motion yielded low phase angles (mean 16 +/- 15 degrees SD). With an increase in wall motion abnormalities, phase angles were progressively delayed by 56 +/- 38 degrees in hypokinetic, by 88 +/- 38 degrees in akinetic, and by 143 +/- 33 degrees (p < 0.001) in dyskinetic segments.

CONCLUSIONS

These results demonstrate that left ventricular asynchrony is an indicator of regional myocardial dysfunction in coronary artery disease. Echocardiographic Fourier phase imaging can be used to quantify wall motion displaying contraction sequence in a simple and objective format.

Prognostic value of Doppler echocardiographic mitral inflow patterns: implications for risk stratification in patients with chronic congestive heart failure

OBJECTIVES

This prospective study tested whether transmitral flow patterns add incremental value to peak oxygen consumption (VO2) in determining the prognosis of patients with chronic congestive heart failure (CHF) and systolic dysfunction.

BACKGROUND

Peak VO2 is an objective marker of functional capacity and is routinely used as a criterion to identify heart transplant candidates. Diastolic dysfunction limits functional capacity, but its prognostic importance relative to that of peak VO2 is unknown.

METHODS

Peak VO2 and mitral inflow velocities were prospectively measured in 311 consecutive patients (mean age 54 years, 84% male) with impaired left ventricular function (ejection fraction <40%; 88 patients with ischemic and 223 with dilated cardiomyopathy) who were evaluated for heart transplant candidacy.

RESULTS

During a mean follow-up period of 512 +/- 314 days, 65 patients died and 43 patients underwent heart transplantation. Diastolic filling patterns, peak VO2 and left ventricular end-diastolic diameters were independent predictors of cardiac mortality. In patients with peak VO2 < or = 14 ml/min per kg body weight, the outcome was markedly poorer in the presence of restrictive filling patterns as compared with their absence (two-year survival rate 52% vs. 80%). Similarly, despite peak VO2 levels >14 ml/min per kg, the outcome was less favorable in the presence of restrictive filling patterns (two-year survival rate 80% vs. 94%). A risk-stratification model based on the identified independent noninvasive predictors separated groups into those with high (93%), intermediate (65%) and low (39%) two-year survival rates.

CONCLUSIONS

Transmitral flow patterns add incremental value to peak VO2 in determining the prognosis of patients with CHF and impaired systolic function.

The neuronal norepinephrine transporter in experimental heart failure: evidence for a posttranscriptional downregulation

An impairment of norepinephrine (NE) re-uptake by the neuronal NE transporter (NET) has been shown to contribute to the increased cardiac net-release of NE in congestive heart failure (CHF). The present study investigated which mechanisms are involved in the impairment of NET. Rats with supracoronary aortic banding characterized by myocardial hypertrophy, elevated left ventricular end diastolic pressures and severe pulmonary congestion were used as an experimental model for CHF. Compared to sham-operated controls, aortic-banded rats had enhanced plasma NE concentrations and decreased cardiac NE stores. In isolated perfused hearts of aortic-banded rats, functional impairment of NET was indicated by a 37% reduction in [(3)H]-NE-uptake. In addition, pharmacological blockade of NET with desipramine led to a markedly attenuated increase in the overflow of endogenous NE from hearts of aortic-banded rats. Determination of cardiac NET protein and of NET mRNA in the left stellate ganglion by [(3)H]-desipramine binding and competitive RT-PCR, respectively, revealed a 41% reduction of binding sites but no difference in gene expression. The density of sympathetic nerve fibers within the heart was unchanged, as shown by glyoxylic acid-induced histofluorescence. In conclusion, as impairment of intracardiac NE re-uptake by a reduction of NET binding sites is neither mediated by a decreased NET gene expression nor by a loss of noradrenergic nerve terminals, a posttranscriptional downregulation of NET per neuron is suggested in CHF.

Inefficient ventilation and reduced respiratory muscle capacity in congestive heart failure

The extent and time-course of changes in lung volumes, ventilatory efficiency at rest and during exercise, and respiratory muscle function and their influence on exercise limitation in congestive heart failure (CHF) are unclear. It is unknown whether respiratory muscle function may predict changes in exercise limitation or may be impaired in patients with poor outcome. 145 male patients (54 +/- 1 years) suffering from CHF (NYHA class I-III, mean 2.3 +/- 0.1), with a LVEF of 23 +/- 1%, and a mean peak O2 uptake (VO2peak) 15.0 +/- 0.5 mL X min(-1) X kg(-1), were studied. They were grouped in Weber functional classes A to D according to their VO2peak. Significant increases in ventilatory equivalents for O2 and CO2 (VE/VCO2peak) and in dead space ventilation at rest and during exercise were found with increasing exercise limitation. Moreover, there was a correlation of static and dynamic lung volumes (inspiratory vital capacity, IVC, r = 0.43, P < 0.01), as well as of maximal inspiratory pressure (MIP; r = 0.46, P < 0.01) with VO2peak. Patients who died (n = 26) or were heart transplanted (n = 20) during a follow-up (mean 800 +/- 10 days) had a reduced MIP (6.4 +/- 0.4 kPa) as compared with survivors (n = 82; 9.3 +/- 0.7 kPa, P < 0.01). In a subgroup of 33 patients re-evaluated after six months, individual changes in IVC and VE/CO2peak, but not in MIP, correlated to changes in VO2peak (r = 0.69 and r = 0.72 respectively; P < 0.01). In CHF, exercise limitation is associated with reversible lung restriction and inefficient ventilation at rest and during exercise. Patients with severe CHF have a significant reduction in MIP, a finding that is associated with poor outcome.

HEp2 ANA EIA: a new fully automated assay for the screening of antinuclear antibodies

BACKGROUND

Screening for antinuclear antibodies is performed for various systemic autoimmune diseases with various different techniques. A more recent approach to ANA screening is the use of enzyme immunoassays.

OBJECTIVES

To introduce the new COBAS CORE HEp2 ANA EIA, the first fully automated enzyme immunoassay for the detection of ANA in serum and plasma of patients with suspected systemic autoimmune disease.

METHODS

A method comparison between the new HEp2 ANA EIA and immunofluorescence assays on HEp2 cells was performed in two groups--977 patients with systemic autoimmune disorders and 952 healthy subjects with no autoimmune disease-related diagnosis.

RESULTS

The clinical sensitivity in the patient group was 79.8% for HEp2 ANA EIA and 89.5% for IFA, and the clinical specificity in the control group was 91.7% for HEp2 ANA EIA and 93.9% for IFA. The analysis of 830 routine samples showed an overall good concordance of 85% between both assays. Further examination of the discrepant results showed 8% discrepant negative results for the HEp2 ANA EIA assay compared to 21% for IFA. Discrepant positive results were found in 37.9% and 33% of samples for the HEp2 ANA EIA and the IFA, respectively.

CONCLUSION

The HEp2 ANA EIA is the first fully automated assay for the detection of ANA in serum and plasma. The assay shows improved sensitivity in ANA determination and a similar performance, compared to the standard method of IFA.

Is the 6-minute walk test a reliable substitute for peak oxygen uptake in patients with dilated cardiomyopathy?

AIMS

The 6-min walk test may serve as a more simple clinical tool to assess functional capacity in congestive heart failure than determination of peak oxygen uptake by cardiopulmonary exercise testing. The purpose of the study was to prospectively examine whether the distance ambulated during a 6-min walk test (i) correlates with peak oxygen uptake, (ii) allows peak oxygen uptake to be predicted, and (iii) provides prognostic information similar to peak oxygen uptake in patients with dilated cardiomyopathy and left ventricular ejection fraction < or = 35%.

METHODS AND RESULTS

In 113 patients (age: 54+/-12 years, NYHA: 2.2+/-0.8) with dilated cardiomyopathy (left ventricular ejection fraction 19+/-7%) a 6-min walk test and cardiopulmonary exercise testing were performed. The 6-min walk test and peak oxygen uptake were closely correlated at the initial visit (r=0.68, n=113), as well as after 263+/-114 (r=0.71, n=28) and 381+/-170 days (r=0.74, n=14). During serial exercise testing the 6-min walk test allowed peak oxygen uptake to be reliably predicted (r=0.76 between calculated and real peak oxygen uptake). After 528+/-234 days, 42 patients were hospitalized due to worsening heart failure and/or died from cardiovascular causes. Compared to clinically stable patients, these 42 patients walked a shorter distance (423+/-104 vs 501+/-95 m, P<0.001) and had a lower peak oxygen uptake (12.7+/-4.0 vs 17.4 + 5.6 ml x min(-1) x kg(-1), P<0.001). By univariate analysis the 6-min walk test outperformed other prognostic parameters such as left ventricular ejection fraction, cardiac index and plasma norepinephrine concentration and conferred a prognostic power similar to peak oxygen uptake. This predictive value could be further improved in a multivariate model, by combining the 6-min walk test with independent variables, such as left ventricular ejection fraction or cardiac index.

CONCLUSION

The 6-min walk test correlated with peak oxygen uptake when tested serially over the course of the disease. Although both tests define two distinct domains of functional capacity, the 6-min walk test provides prognostic information very similar to peak oxygen uptake in congestive heart failure patients with dilated cardiomyopathy.

The bradycardic agent zatebradine enhances baroreflex sensitivity and heart rate variability in rats early after myocardial infarction

OBJECTIVE

The bradycardic agent zatebradine (UL-FS 49) reduces heart rate without negative inotropic or proarrhythmic effects. The aim was to experimentally characterize the influence of zatebradine on arterial baroreflex sensitivity (BRS) and heart rate variability (HRV) which are generally considered as estimates of vagal activity and have prognostic value in patients after myocardial infarction (MI).

METHODS

Conscious rats were studied 3 days after left coronary artery ligation or sham-operation (SH). BRS was determined by linear regression analysis of RR-interval and mean arterial pressure changes evoked by intravenous (i.v.) injections of methoxamine and nitroprusside. HRV at rest was calculated from high-resolution electrocardiogram-recordings.

RESULTS

In MI-rats heart rate was similar to SH-rats, mean arterial pressure was lower and both BRS and HRV were markedly reduced. Zatebradine (0.5 mg/kg i.v.) reduced heart rate in MI-rats from 400 +/- 15 to 350 +/- 19 and in SH-rats from 390 +/- 19 to 324 +/- 6 beats/min without changing mean arterial pressure. Both BRS and HRV were restored in MI- and further increased in SH-rats by the drug. Effects of 0.05, 0.5 and 5 mg/kg zatebradine revealed a dose-dependency of heart rate reduction. The lowest dose enhanced reflex bradycardia despite little effect on heart rate and lack of effect on both reflex tachycardia and HRV.

CONCLUSIONS

Both BRS and HRV are reduced in rats early after MI, indicating a depressed reflex and tonic vagal activity. Treatment with zatebradine enhances both BRS and HRV. These data suggest that the drug has both peripheral and central effects, leading to an increase of vagal control of heart rate.

[The 6 minute walking test: a cost-effective alternative to spiro-ergometry in patients with chronic heart failure?]

In contrast to the often debated NYHA classification, the determination of peak oxygen uptake (peak VO2) by cardiopulmonary exercise testing allows an objective assessment of the exercise capacity of patients with congestive heart failure (CHF). However, cardiopulmonary exercise testing is a time consuming and costly diagnostic tool, which requires sophisticated equipment and specially trained personel. Exercise capacity can also be determined by the 6 minute walk test. This test simply measures the distance covered by strong walking on a hallway level within 6 minutes. The 6 minute walk test is a submaximal exercise test, which is associated with much smaller increments in heart rate, blood pressure and plasma catecholamines than cardiopulmonary exercise testing. It is characterized by a very small intraindividual variance. Furthermore, it can be easily performed and, due to low logistic and personal requirements, it is very cost effective. The results of the 6 minute walk test--as well as of cardiopulmonary exercise testing--are influenced by extracardial exercise-limiting disorders, such as pulmonary diseases. Independent from the etiology of CHF, the results of the 6 minute walk test are closely related to peak VO2. In serial exercise testing the distance covered within 6 minutes allow to predict the individual peak VO2. Like peak VO2 the 6 minute walk test has been shown to be a predictor of morbidity and mortality in CHF, with its predictive value being independent from left ventricular ejection fraction and other potential prognostic parameters. In CHF patients a walking distance < 300 m is associated with a one-year-mortality of up to 50%, whereas the one-year-mortality in patients reaching a walking distance > 450 m amounts to only a few percent. In addition, the hospitalization rate of patients reaching a walking distance of < 300 m is several fold higher than in those with a walking distance > or = 450 m. Like cardiopulmonary exercise testing, the 6 minute walk test allows to control the efficiency of specific treatments and to monitor the natural course of the disease. The 6 minute walk test is, thus, a cost effective alternative to cardiopulmonary exercise testing in CHF patients. However, neither the 6 minute walk test alone nor the results of cardiopulmonary exercise testing alone are sufficient for selecting patients, e.g., for cardiac transplantation, as each individual case requires a synopsis of all relevant facts and parameters.

Desensitization of the pulmonary adenylyl cyclase system: a cause of airway hyperresponsiveness in congestive heart failure?

OBJECTIVES

This study was designed to investigate whether the adrenergic signal transduction in the lung and the responsiveness of airway smooth muscle to adrenergic stimulation are modulated in congestive heart failure.

BACKGROUND

Wheezing and airway hyperresponsiveness are often present in heart failure. In the failing heart, chronic adrenergic stimulation down-regulates beta-adrenergic receptors and adenylyl cyclase. We hypothesized that airway dysfunction in heart failure could be due to a similar modulation of pulmonary adrenergic signal transduction.

METHODS

Heart failure was induced in rats by aortic banding, resulting in increases in plasma norepinephrine, lung wet weight indicating congestion and left ventricular end diastolic pressure after four weeks. Beta-receptor densities in pulmonary plasma membranes were measured by radioligand binding using [125I]iodocyanopindolol. The G protein levels were determined by Western blot. Adenylyl cyclase activities in lung membranes were quantified as [32P]cAMP (cyclic adenosine-5'-monophosphate) synthesis rate. To functionally assess airway smooth muscle relaxation, carbachol-precontracted isolated tracheal strips were used.

RESULTS

Beta-receptor density was significantly decreased in heart failure from 771 +/- 89 to 539 +/- 44 fmol/mg protein without changes in receptor affinities. The beta1-/beta2-subtype ratio, however, remained constant. The G(i and alpha) and G(s alpha) protein expression was unchanged. Adenylyl cyclase activity stimulated directly with forskolin was decreased by 28%. Relaxation of tracheal strips in response to isoproterenol and forskolin, but not to papaverin, was diminished by 30%.

CONCLUSIONS

In heart failure, the down-regulation of pulmonary beta-receptors and concomitant decrease in adenylyl cyclase activity result in a significant attenuation of cAMP-mediated airway relaxation. These mechanisms may play a pivotal role in the pathogenesis of"cardiac asthma."

[Differential diagnosis in anorexia nervosa: glycogenosis II (the Pompe type)]

HISTORY AND ADMISSION FINDINGS

A 29-year-old woman had since early childhood been smaller and thinner than her contemporaries. Her weight was now 36.5 kg, height 158 cm. Anorexia nervosa being suspected she was to be admitted to a psychosomatic clinic. A few days before the date she developed respiratory failure which required mechanical ventilation for a month. Physical examination revealed markedly reduced musculature.

INVESTIGATIONS

Muscle biopsy and fibroblast culture indicated acid maltase deficiency (glycogen storage disease Type II [Pompe's disease]). Lung functions were markedly reduced, blood gas analysis revealing global respiratory insufficiency.

TREATMENT AND COURSE

Intermittent patient-controlled ventilation (at night by intermittent positive pressure ventilation) clearly improved both her general condition and blood gases.

CONCLUSIONS

Acid maltase deficiency should be included as a possible cause of the differential diagnosis of anorexia nervosa. This diagnosis should strictly follow the criteria listed in ICD-10 (International Classification of Diseases), but also after exclusion of other causes.

Angiotensin inhibition and atrial natriuretic peptide release after acute volume expansion in rats with aortocaval shunt

OBJECTIVE

In heart failure atrial natriuretic peptide (ANP) release in response to volume expansion is impaired while the renin-angiotensin system is activated. This study was designed to test the hypothesis that ANP release in heart failure is dependent on an activated angiotensin system.

METHODS

We studied the ANP and renin-angiotensin systems in a rat model of shunt-induced high-output heart failure, in which we rapidly increased circulating fluid volume with a 5 ml, hyperoncotic infusion, and evaluated the effects of acute inhibition of the angiotensin converting enzyme as well as of the blockade of the angiotensin II type 1 receptors on the ANP release and on renal excretory function.

RESULTS

ANP and angiotensin II plasma concentrations prior to volume expansion were elevated (p < 0.05) in rats with aortocaval shunt compared to controls. The diuretic response to acute volume expansion (18.5 +/- 1.5 vs. 48.2 +/- 2.4 microliters/min, p < 0.001) was markedly blunted. ANP release was attenuated in rats with aortocaval shunt, as was the increase of its second messenger cGMP in plasma and urine. The blunted increase in ANP plasma levels was not due to depleted cardiac stores as cardiac ANP content, as well as ANP synthesis, were increased (p < 0.05). Acute inhibition of the angiotensin converting enzyme as well as blockade of the angiotensin II type 1 receptors restored ANP release in response to volume expansion (p < 0.01). Moreover, acute inhibition of the renin-angiotensin system completely normalized the diuretic response.

CONCLUSIONS

Our data suggest that the ANP system is impaired in rats with aortocaval shunt. The activation of the angiotensin system contributes to the impairment of the ANP system. Acute inhibition of the angiotensin II system significantly improved the ability of the ANP system to respond to acute volume expansion. Our findings indicate a hitherto fore unappreciated interaction between both systems and suggest additional mechanisms for the beneficial effects of angiotensin converting enzyme inhibition or angiotensin II type 1 receptor antagonists in heart failure.

Influence of Bretschneider's cardioplegia on norepinephrine release from isolated perfused guinea-pig hearts

It was the aim of the present study to investigate the influence of Bretschneider's cardioplegia on norepinephrine (NE) release [determined by high pressure liquid chromatography (HPLC) and electrochemical detection] in isolated perfused guinea-pig hearts. The following resulted were noted. (1) Calcium-dependent exocytotic NE release evoked by electrical field stimulation (12 Hz, 1 min) was completely suppressed after only 3 min of normothermic (37.5 degrees C) Bretschneider's cardioplegia. (2) Stop-flow ischemia is associated with a substantial calcium-independent, non-exocytotic NE release, which is regarded as a sodium-dependent carrier-mediated process. Accordingly, it is inhibited by blockers of the sodium/proton-exchanger (e.g. amiloride) and the neuronal uptake1-carrier (e.g. desipramine). Compared with stop-flow ischemia alone, cardioplegia with 3 min of Bretschneider's histidine-tryptophan-ketoglutarate (HTK)-solution preceding stop-flow enhanced NE release at all stop-flow durations (10-90 min) investigated (e.g. after 30 min of normothermic Bretschneider's cardioplegia: 1070+/-41 pmol/g, n = 45, v stop-flow alone: 764+/-48 pmol/g, n = 27, P<0.05). The NE concentrations determined in the cardiac effluent upon reperfusion followed a typical first order kinetic indicating that the transmitter release had already occurred during stop-flow. Hypothermia reduced NE release in a temperature-dependent manner down to intramyocardial temperatures of 2 7.5 degrees C. NE release evoked by Bretschneider's cardioplegia still exceeded that induced by stop-flow ischemia alone by up to 60%. The NE release evoked by Bretschneider's cardioplegia and stop-flow ischemia was calcium-independent. However, it was significantly reduced by desipramine and amiloride, but both agents had a more pronounced inhibitory effect on NE release evoked by stop-flow ischemia alone. (3) This difference may be due to an intrinsic effect of Bretschneider's HTK-solution, as continuous administration of normothermic Bretschneider's HTK-solution induced a substantial NE release which was neither calcium-dependent nor inhibited by blockade of either uptake1 or sodium/proton-exchange. It is concluded that Bretschneider's cardioplegia is not neuroprotective, as it even augments the stop-flow ischemia-induced nonexocytotic NE release.

Effect of moxonidine on blood pressure and sympathetic tone in conscious spontaneously hypertensive rats

The effects of moxonidine on blood pressure, heart rate and sympathetic tone were studied in conscious spontaneously hypertensive rats. Intravenous moxonidine (80 nmol) transiently increased blood pressure without affecting heart rate or splanchnic nerve activity. Moxonidine (20-80 nmol) given into the fourth cerebral ventricle dose-dependently lowered mean arterial pressure, heart rate and sympathetic outflow (maximally by 60 +/- 3 mm Hg, 148 +/- 10 beats min(-1) and 15 +/- 3 microV). Moxonidine was more effective by this route than after the injection into the lateral ventricle. Clonidine (20-80 nmol) produced an initial pressor response after both intracerebroventricular routes of administration. A decrease in blood pressure was observed only when clonidine was given into the fourth ventricle. Clonidine decreased heart rate and splanchnic nerve activity similarly like moxonidine when the substances were given into the fourth ventricle. The data imply that the hypotensive effect of moxonidine is related to central sympathoinhibition. The main site of this action appears to be in the brainstem region.