Mechanisms of Carvedilol Action in Human Congestive Heart Failure

Exploring Sex Differences of Beta-Blockers in the Treatment of Hypertension: A Systematic Review and Meta-Analysis

AIMS

In the prevention of cardiovascular morbidity and mortality, early recognition and adequate treatment of hypertension are of leading importance. However, the efficacy of antihypertensives may be depending on sex disparities. Our objective was to evaluate and quantify the sex-diverse effects of beta-blockers (BB) on hypertension and cardiac function. We focussed on comparing hypertensive female versus male individuals.

METHODS AND RESULTS

A systematic search was performed for studies on BBs from inception to May 2020. A total of 66 studies were included that contained baseline and follow up measurements on blood pressure (BP), heart rate (HR), and cardiac function. Data also had to be stratified for sex. Mean differences were calculated using a random-effects model. In females as compared to males, BB treatment decreased systolic BP 11.1 mmHg (95% CI, -14.5; -7.8) vs. 11.1 mmHg (95% CI, -14.0; -8.2), diastolic BP 8.0 mmHg (95% CI, -10.6; -5.3) vs. 8.0 mmHg (95% CI, -10.1; -6.0), and HR 10.8 beats per minute (bpm) (95% CI, -17.4; -4.2) vs. 9.8 bpm (95% CI, -11.1; -8.4)), respectively, in both sexes' absolute and relative changes comparably. Left ventricular ejection fraction increased only in males (3.7% (95% CI, 0.6; 6.9)). Changes in left ventricular mass and cardiac output (CO) were only reported in males and changed -20.6 g (95% CI, -56.3; 15.1) and -0.1 L (95% CI, -0.5; 0.2), respectively.

CONCLUSIONS

BBs comparably lowered BP and HR in both sexes. The lack of change in CO in males suggests that the reduction in BP is primarily due to a decrease in vascular resistance. Furthermore, females were underrepresented compared to males. We recommend that future research should include more females and sex-stratified data when researching the treatment effects of antihypertensives.

Model-based meta-analysis of changes in circulatory system physiology in patients with chronic heart failure

To characterize and compare various medicines for chronic heart failure (CHF), changes in circulatory physiological parameter during pharmacotherapy were investigated by a model-based meta-analysis (MBMA) of circulatory physiology. The clinical data from 61 studies mostly in patients with heart failure with reduced ejection fraction (HFrEF), reporting changes in heart rate, blood pressure, or ventricular volumes after treatment with carvedilol, metoprolol, bisoprolol, bucindolol, enalapril, aliskiren, or felodipine, were analyzed. Seven cardiac and vasculature function indices were estimated without invasive measurements using models based on appropriate assumptions, and their correlations with the mortality were assessed. Estimated myocardial oxygen consumption, a cardiac load index, correlated excellently with the mortality at 3, 6, and 12 months after treatment initiation, and it explained differences in mortality across the different medications. The analysis based on the present models were reasonably consistent with the hypothesis that the treatment of HFrEF with various medications is due to effectively reducing the cardiac load. Assessment of circulatory physiological parameters by using MBMA would be insightful for quantitative understanding of CHF treatment.

Atrial fibrillation is associated with decreased cardiac sympathetic response to isometric exercise in CHF in comparison to sinus rhythm

BACKGROUND

The presence of atrial fibrillation (AF) in congestive heart failure (CHF) is accompanied by increased mortality, although the exact mechanism is unclear. In previous studies, we have demonstrated cardiac baroreceptor abnormalities in association with AF and CHF. In this study, we sought to examine the effect of cardiac rhythm on the cardiac sympathetic response to exercise in CHF.

METHODS

In 13 CHF patients (six AF, seven SR, left ventricular ejection fraction 31 +/- 2%, age 61 +/- 1 years), we measured the hemodynamic and cardiac sympathetic response isometric handgrip (IHG) exercise.

RESULTS

At baseline the groups were well matched. Baseline hemodynamics and cardiac sympathetic activity did not significantly differ between the cohorts. In response to IHG exercise, both groups demonstrated significant hemodynamic responses. In conjunction, the sinus rhythm (SR) group demonstrated a significant increase in cardiac sympathetic response to exercise (P = 0.04) while in contrast the AF group did not (P = 0.6).

CONCLUSION

In this study, we demonstrate for the first time that the combination of AF and CHF is accompanied by a marked attenuation of the cardiac sympathetic response to acute hemodynamic stress. This implies AF is associated with a further impairment of baroreceptor response in CHF compared to SR. These findings present possible insights to the associated increased mortality and pathogenesis of AF with CHF.

Effects of carvedilol on oxidative stress and chronotropic response to exercise in patients with chronic heart failure

BACKGROUND

Our previous studies suggest that the increase in heart rate from rest to peak exercise is reduced in patients with chronic heart failure (CHF) and this is associated with increased oxidative stress, as determined by malondialdehyde (MDA) plasma levels.

AIM

To investigate the effects of carvedilol on the heart rate response to exercise and oxidative stress in patients with CHF.

METHODS AND RESULTS

Thirty stable NYHA classes II-III CHF patients received carvedilol therapy for 6 months, at a mean maintenance dose of 25 mg (range 6.25-50 mg/day). After treatment, the patients showed a significant improvement in their functional NYHA class (p=0.013), increased left ventricular ejection fraction (LVEF) (24+/-1.4% to 31+/-2.3%, p=0.003) and 6-min walk distance (499+/-18 to 534+/-18 m, p=0.03), without changes in the peak VO2. At baseline, norepinephrine (NE) plasma levels increased with exercise (510+/-51 to 2513+/-230 pg/mL, p<0.001), and these levels were not affected by carvedilol. Chronotropic responsiveness index (increase in heart rate divided by the increase in NE from rest to peak exercise) was not changed by carvedilol (0.049+/-0.001 to 0.042+/-0.001, p=0.6). MDA levels of CHF patients decreased after treatment with carvedilol (2.4+/-0.2 to 1.1+/-0.2 microM, p<0.001), without changes in antioxidant enzyme activities.

CONCLUSIONS

Carvedilol treatment in patients with CHF results in reduced oxidative stress without restoration of the chronotropic responsiveness index.

Relationship Between β-Blocker Treatment and the Severity of Central Sleep Apnea in Chronic Heart Failure

BACKGROUND

We sought to examine the relationship between use of beta-blockers and the severity of central sleep apnea (CSA) in patients with chronic heart failure.

METHODS

We performed polysomnography in 45 patients with chronic heart failure (New York Heart Association functional class II/III and left ventricular ejection fraction < 50%) and examined the relationship between use of beta-blockers and the severity of CSA. Central apnea index (CAI) was used as an indicator of CSA.

RESULTS

Patients receiving beta-blockers (ie, carvedilol; n = 27) had lower apnea-hypopnea index (AHI) and CAI than patients not receiving beta-blockers (n = 18) [mean +/- SD, 14 +/- 11 vs 33 +/- 17, p < 0.0001; and 1.9 +/- 3.2 vs 11 +/- 12, p = 0.0004, respectively]. AHI and CAI were negatively correlated with the dose of carvedilol (Spearman rho = - 0.61, p < 0.0001; and Spearman rho = - 0.57, p = 0.0002, respectively). Multiple regression analysis selected no use of beta-blockers as an independent factor of CAI (p = 0.0006). In five patients with CAI > 5 who underwent serial sleep studies, CAI decreased significantly after 6 months of treatment with carvedilol (9.5 +/- 4.9 to 1.3 +/- 2.4, p = 0.03).

CONCLUSIONS

In patients with chronic heart failure, CAI was lower according to the dose of beta-blockers, and no use of beta-blockers was independently associated with CAI. In addition, 6 months of treatment with carvedilol decreased CAI. These results suggest that beta-blocker therapy may dose-dependently suppress CSA in patients with chronic heart failure.

Long-term treatment with the beta-blocker carvedilol restores autonomic tone and responsiveness in patients with moderate heart failure

The authors performed two studies on the effects of carvedilol on autonomic tone and responsiveness in patients with heart failure. In study 1, the autonomic responses of 25 patients (age, 60 years+/-2; New York Heart Association [NYHA] class, 2.6+/-0.5; pVO2, 16.6 mL/Kg/min+/-1.1) treated with angiotensin-converting enzyme inhibitors, diuretics, and carvedilol (38.0 mg/d+/-2.5) were compared to those of 25 patients of similar age, therapy, NYHA class, and pVO2 in whom carvedilol was not yet administered. In study 2, autonomic tone and responsiveness were studied in 20 patients (age, 57 years+/-9; NYHA class, 2.5+/-0.2; pVO2, 15.6 mL/Kg/min+/-3.4), before and 6 months after additional carvedilol treatment (40.0 mg/d+/-12.5). Autonomic evaluation was performed with autoregressive power spectral analysis of RR variability during 10 minutes of supine rest (control), breathing 20 times per minute (vagal stimulus), and standing (sympathetic activation). The ratio between low-frequency (LF) and high-frequency (HF) components of the autospectra indicated the sympathovagal interaction. In study 1, spectral analysis in controls showed sympathetic hyperactivity which was blunted in patients receiving carvedilol (LF/HF ratio: 10.4+/-1.4 vs. 7.0+/-1.1; P<0.05) who responded to vagal and adrenergic stimuli (LF/HF, -35% with regular breathing and 72% standing). In study 2, left ventricular function, volumes, and exercise performance improved with carvedilol (EF, 31%; EDLV volume, -22%; pVO2, 11%; P<0.05). Sympathetic hyperactivity in control was reduced (LF/HF ratio, 4.9+/-0.8 from 7.9+/-1.3; P<0.05), whereas a response to vagal and adrenergic activation on breathing and standing reemerged (LF/HF ratio, -31% during regular breathing and 88% on standing). Therefore, combined autonomic and hemodynamic effects may determine the favorable effects of beta-blockers in heart failure.