Decreased heart rate variability (HRV) is associated with a worse prognosis in a variety of diseases and disorders. We evaluated the determinants of short-period HRV in a random sample of 149 middle-aged men and 137 women from the general population. Spectral analysis was used to compute low-frequency (LF), high-frequency (HF) and total-frequency power. HRV showed a strong inverse association with age and heart rate in both sexes with a more pronounced effect of heart rate on HRV in women. Age and heart rate-adjusted LF was significantly higher in men and HF higher in women. Significant negative correlations of BMI, triglycerides, insulin and positive correlations of HDL cholesterol with LF and total power occurred only in men. In multivariate analyses, heart rate and age persisted as prominent independent predictors of HRV. In addition, BMI was strongly negatively associated with LF in men but not in women. We conclude that the more pronounced vagal influence in cardiac regulation in middle-aged women and the gender-different influence of heart rate and metabolic factors on HRV may help to explain the lower susceptibility of women for cardiac arrhythmias.

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The natural history and the pathogenesis of CCM and myocarditis (MC) are unclear, and whether there is a relationship between the pathogenesis of these two diseases has not been resolved. Therefore, we compared the suppressor cell function in patients with CCM and MC and in clinically healthy controls. Materials and Methods ProbandsThe CCM group included 10 patients, eight males and two females, ages 26-66 years, with a clinical diagnosis of congestive heart failure without detectable etiology, a decreased ejection fraction, an increased end-diastolic volume in most cases, and a morphologic analysis of an endomyocardial biopsy compatible with CCM (table 1). According to the terminology of Olsen,7 the morphologic criteria characteristic of congestive cardiomyopathies are attenuated muscle fibers, interstitial fibrosis and morphologic signs of muscle hypertrophy and dilatation.The MC group included 13 patients, nine males and four females, ages 34-64 years, with a clinical diagnosis of congestive heart failure due to MC with and without immediate time relation to a common cold infection, a decreased ejection fraction, and morphologic evidence of MC on endomyocardial biopsy or an accompanying change in viral titer on follow-up (table 2).The control group included 98 healthy personsmostly blood donors -28 males and 70 females, ages 17-62 years.Hypertension, lung diseases, heart valve abnormalities and coronary artery disease were excluded in each of the evaluated cases by clinical measures, including electrocardiography and echocardiography. In patients with CCM and MC, these diseases were excluded by invasive measurements of right-and leftheart pressures, ventriculography and coronary angiography.Endomyocardial biopsies were performed from the septal part of the right ventricle with the bioptome described by Richardson.8

AMI patients had strongly diminished HRV compared to the general population. The relatively lower LF power indicates an alteration of the sympathico-vagal balance, and the significantly stronger correlation of heart rate with HRV may be indicative for a more pronounced effect of sympathetic activation on autonomic modulation in the case of myocardial infarction. Finally, a value below the 2.5th percentile of the population LF power distribution may identify subjects at risk and warrant further testing.