Increased ventricular premature contraction frequency during rem sleep in patients with coronary artery disease and obstructive sleep apnea.

Background: Patients with obstructive sleep apnea are reported to have a peak of sudden cardiac death at night, in contrast to patients without apnea whose peak is in the morning. We hypothesized that ventricular premature contraction (VPC) frequency would correlate with measures of apnea and sympathetic activity.

Methods: Electrocardiograms from a sleep study of 125 patients with coronary artery disease were evaluated.

Circadian and ultradian rhythms in cardiac autonomic modulation.

Unlabelled: Heart rate variability (HRV) patterns reflect the changing sympathetic and parasympathetic modulation of the autonomic nervous system. While overall and circadian heart rate (HR) and HRV are well characterized by traditional measures, ultradian cycles of HR and HRV are not. We have developed a method for capturing these rhythms during sleep and have now applied it to 24-hour recordings.

Circadian and ultradian rhythms in heart rate variability.

Aim: Heart rate variability (HRV) patterns reflect the changing effect of sympathetic and parasympathetic modulation of the autonomic nervous system. While overall and circadian heart rate (HR) and HRV are well characterized by traditional measures, there is currently no method to measure ultradian cycles of HR and HRV.

Materials And Methods: HR/HRV for each 2-min interval was calculated using normal-to-normal interbeat intervals from overnight polysomnographic ECGs in 113 subjects, aged 58+/-10 years (65 male, 48 female).