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BACKGROUND Baroreflex-mediated parasympathetic stimulation has variable effects on heart rate variability (HRV). We postulated that a quadratic function would describe the relationship between HRV and parasympathetic effect better than a linear function. METHODS AND RESULTS Twenty-nine normal volunteers (15 women; mean age 39+/-12 years) were studied(More)
The authors describe the clinical characteristics and response to therapy of seven patients with hyperthyroidism, dilated cardiomyopathy, and low-output cardiac failure. All patients (4 women and 3 men, age 47 +/- 4 years, mean +/- standard error of the mean) were admitted with the primary diagnosis of congestive heart failure. The cause of hyperthyroidism(More)
INTRODUCTION Low heart rate variability (HRV) has been shown to have important prognostic significance in multiple settings. Although this is believed to reflect reduced parasympathetic tone, the physiology of reduced parasympathetic tone has not been elucidated. METHODS AND RESULTS To evaluate whether parasympathetic withdrawal and partial(More)
BACKGROUND Signal-averaged ECG (SAECG) reproducibility is reported to have a component that is independent of residual noise. Methods and Results-In group 1, multiple paired SAECGs were obtained to noise levels of 0.3+/-0.1 and 0.5+/-0.2 microV. For the 0.5- and 0. 3-microV noise recordings, QRS duration (QRSd) was 101.2+/-11.3 and 104.6+/-9.6 ms,(More)
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