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Effects of carvedilol on heart rate dynamics in patients with congestive heart failure
Mustafa Ridha1, Timo H Mäkikallio, Gustavo Lopera
1Cardiology (111-A), V.A. Medical Center, 1201 NW 16th Street, Miami, FL 33125, USA.
Insights
Carvedilol significantly improves heart rate (HR) dynamics, ejection fraction, and functional capacity in patients with congestive heart failure (CHF). This suggests carvedilol may normalize cardiovascular neural regulation in CHF patients.
Area of Science:
- Cardiology
- Pharmacology
- Biomedical Engineering
Background:
- Congestive heart failure (CHF) is linked to altered heart rate (HR) dynamics and increased mortality risk.
- Nonselective beta-blocker carvedilol possesses alpha-1 blocking properties.
Purpose of the Study:
- To evaluate the effects of carvedilol on heart rate (HR) dynamics in patients with congestive heart failure (CHF).
Main Methods:
- 15 CHF patients (NYHA class II-III, LVEF < 40%) received 12 weeks of carvedilol therapy.
- Evaluated traditional and nonlinear HR dynamics, left ventricular ejection fraction (LVEF), and 6-minute walk test performance.
Main Results:
- Carvedilol improved LVEF (0.27 to 0.38, P < 0.001) and reduced HR (86 to 70 bpm, P < 0.001).
- Significant improvements observed in 6-minute walk distance, time/frequency domain HR variability indices, and short-term fractal scaling exponent.
- The change in fractal scaling exponent correlated with LVEF improvement (r = 0.63, P < 0.01).
Conclusions:
- Carvedilol enhances HR variability indices and fractal scaling properties in CHF patients.
- Treatment with carvedilol also improves LVEF and functional capacity.
- Observed HR changes may indicate normalization of impaired cardiovascular neural regulation in CHF.
Background:
Patients with congestive heart failure (CHF) have alterations in the traditional and nonlinear indices of heart rate (HR) dynamics, which have been associated with an increased risk of mortality. This study was designed to test the effects of carvedilol, a nonselective beta-blocker with alpha-1 blocking properties, on HR dynamics in patients with CHF.
Methods:
We studied 15 patients with CHF secondary to ischemic or idiopathic cardiomyopathy who met the following inclusion criteria: NYHA functional class II-III, optimal conventional medical therapy, normal sinus rhythm, left ventricular ejection fraction (LVEF) of < 40%, and resting systolic blood pressure greater than 100 mmHg. The 6-minute corridor walk test, estimation of LVEF, and 24-hour Holter recording were performed at baseline and after 12 weeks of therapy with carvedilol. Traditional time and frequency domain measures and short-term fractal scaling exponent of HR dynamics were analyzed.
Results:
After 12 weeks of therapy with carvedilol, the mean LVEF improved significantly (from 0.27 +/- 0.08 to 0.38 +/- 0.08, P < 0.001). The average HR decreased significantly (from 86 +/- 11 to 70 +/- 8 beats/min, P < 0.001). The mean distance traveled in the 6-minute walk test increased significantly (from 177 +/- 44 to 273 +/- 55 m, P < 0.01). The frequency-domain indices (HF and LF), the time domain indices (rMSSD and PNN5 ), and the short-term fractal scaling exponent increased significantly. The scaling exponent increased particularly among the patients with the lowest initial values (< 1.0), and the change in the fractal scaling exponent correlated with the change in ejection fraction (r = 0.63, P < 0.01).
Conclusion:
Carvedilol improves time and frequency domain indices of HR variability and corrects the altered scaling properties of HR dynamics in patients with CHF. It also improves LVEF and functional capacity. These specific changes in HR behavior caused by carvedilol treatment may reflect the normalization of impaired cardiovascular neural regulation of patients with CHF.
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