Factors influencing heart rate variability power spectral analysis during controlled breathing in patients with chronic heart failure or hypertension and in healthy normotensive subjects.

A decreased LFP (low-frequency power) spectral component of HRV [HR (heart rate) variability] is a risk factor for sudden death in patients with CHF (chronic heart failure). In the present study, we evaluated factors (age, arterial pressures and HR) influencing LFP and HFP (high-frequency power) components in short-term recordings during controlled breathing in patients with CHF or hypertension, and healthy normotensive subjects. In patients with CHF, we also compared LFP values with known markers of sudden death [NYHA (New York Heart Association) class, HR and ejection fraction].

Heart rate and blood pressure variability in subjects with vasovagal syncope.

Autonomic nervous system control in subjects with vasovagal syncope is controversial. In the present study, we used short-term spectral analysis to evaluate autonomic control in subjects with recurrent vasovagal syncope. We assessed the ability of spectral indices of HR (heart rate) variability to predict tilt-test responses.

Influence of vitamin C on baroreflex sensitivity in chronic heart failure.

Chronic heart failure (CHF) reduces baroreflex sensitivity. Low baroreflex sensitivity, a risk factor for sudden death, could arise partly from CHF-dependent endothelial dysfunction. Vitamin C at high doses has a protective role against CHF-related endothelial damage.

Effects of long-term beta-blocker (metoprolol or carvedilol) therapy on QT variability in subjects with chronic heart failure secondary to ischemic cardiomyopathy.

Chronic heart failure (CHF) is a risk factor for sudden death. Temporal and spatial changes in repolarization are among the most studied mechanisms for inducing fatal ventricular arrhythmias. Beta blockers effectively reduce the risk of sudden death in CHF.

Effects of sildenafil citrate (viagra) on cardiac repolarization and on autonomic control in subjects with chronic heart failure.

Background: Cases of sudden death associated with sildenafil citrate use have been reported in men with coronary artery disease. The aim of this study was to investigate the drug's effect on cardiac repolarization and sinus autonomic and vascular control in men with mild chronic heart failure (CHF; New York Heart Association classification II). Changes in these variables could predispose patients to malignant ventricular arrhythmias.

QT-interval variability and autonomic control in hypertensive subjects with left ventricular hypertrophy.

Left ventricular hypertrophy is a risk factor for sudden death. Malignant ventricular arrhythmias originate from altered cardiac repolarization. Ample data have described spatial abnormalities in cardiac repolarization [QT interval (QT) dispersion] in subjects with hypertension; more data are needed on temporal changes.