Heart rate variability enhances the prognostic value of established parameters in patients with congestive heart failure.

This prospective study evaluated whether heart rate variability (HRV) assessed from Holter ECG has prognostic value in addition to established parameters in patients with congestive heart failure (CHF). The study included 222 patients with CHF due to dilated or ischemic cardiomyopathy (left ventricular ejection fraction LVEF 21+/-1%; mean+/-SEM). During a mean follow-up of 15+/-1 months, 38 (17%) patients died and 45 (20%) were hospitalized due to worsening of CHF. The HRV parameter SDNN (standard deviation of all intervals between normal beats) was significantly lower in non-surviving or hospitalized than in event-free patients (118+/-6 vs 142+/-5 ms), as were LVEF (18+/-1 vs 23+/-1%), and peak oxygen uptake during exercise (peak VO(2)) (12.8+/-0.5 vs 15.6+/-0.5 ml/min/kg). While each of these parameters was a risk predictor in univariate analysis, multivariate analysis revealed that HRV provides both independent and additional prognostic information with respect to the risk 'cardiac mortality or deterioration of CHF'. It is concluded that the determination of HRV enhances the prognostic power given by the most widely used parameters LVEF and peak VO(2) in the prediction of mortality or deterioration of CHF and thus enables to improve risk stratification.

Basal and pulsatile secretion of human luteinizing hormone--new methods for the analysis of endocrine secretion processes.

Serum concentrations of hormones show typical time-dependent patterns. The diurnal course of the serum concentrations of the luteinizing hormone (LH) was assessed in 35 healthy females monitoring individual concentrations every ten minutes for 24 hours during the follicular phase of their menstrual cycle. Based on these in vivo data, a mathematical procedure was developed for calculation of the momentary hormone secretion rate of an endocrine gland from the time course of the hormone serum concentrations. By means of this procedure, we were able to define the complete 24 hours secretion pattern of LH, including the fact, that basal and pulsatile secretion could be separated from each other in an objective manner. It is possible to calculate the total amount of LH which is secreted per LH-pulse and the basal LH-secretion rate. Two methods were developed to define the time of the onset of an LH-pulse with a preselected probability. Describing the hormonal secretion pattern with a mathematical model provides the basis for therapeutic application of these methods to program implantable hormone-pumps for the therapy of glandular insufficiency.

Heart rate variability in time and frequency domains: effects of gallopamil, nifedipine, and metoprolol compared with placebo.

OBJECTIVE: To assess the effects of three different antianginal drugs on heart rate, blood pressure, and heart rate variability. DESIGN: Randomised, single blind, placebo controlled, cross over study. SETTING: University hospital. PARTICIPANTS: Nine healthy male volunteers. INTERVENTIONS: Oral administration of either 50 mg gallopamil, 20 mg nifedipine, 100 mg metoprolol, or placebo according to a random crossover plan. MAIN OUTCOME MEASURES: Time intervals between consecutive R waves in electrocardiograms measured with an accuracy of 5 ms from digital Holter recordings. Blood pressure monitored continuously by finger plethysmography. RESULTS: Metoprolol lowered heart rate from 62(6) to 51(5) beats/min (p = 0.003) after 78(23) minutes. Nifedipine provoked reflex tachycardia from 56(5) to 94(18) beats/min (p < 0.001) at 10(3) minutes after treatment followed by an exponential decline in heart rate to baseline values with a time constant of 34(7) min in seven subjects but 83 minutes in one volunteer. One subject showed no exponential decline in heart rate. Nifedipine significantly lowered the supine mean arterial pressure from 86(6) to 67(6) mm Hg (p = 0.004) after 11(2) minutes, indicating an acute reduction in arterial resistance. Gallopamil did not significantly change mean heart rate or blood pressure. In the sitting position three hours after administration gallopamil and metoprolol significantly lowered power spectral density in the low frequency band (0.03 Hz to 0.15 Hz) compared with placebo (p < 0.05). Nifedipine did not produce such an effect. CONCLUSIONS: Gallopamil and metoprolol both inhibit cardiac sympathetic activation compared with placebo, whereas nifedipine causes reflex sympathetic activation.