Power spectral analysis of heart rate variability as a predictive test in choosing the most effective length for tilt-training.

Background: In patients with refractory neurally mediated syncope, tilt training--standing motionless against a wall for increased periods of time per day over one month--can often eliminate recurrent episodes and reduce presyncopal symptoms. We designed dual retrospective and prospective studies to assess cardiovascular autonomic function in subjects with recurrent syncope and identify the most effective length of tilt training between one and three months.

Methods And Results: In the retrospective study, before tilt training, and in the prospective study, before and after training, all subjects underwent a recording for short-term spectral analysis of heart rate and systolic blood pressure variability.

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.