Heart rate decline after exercise in patients with hypertrophic cardiomyopathy

To evaluate the heart rate recovery, submaximal exercise, echocardiographic examination, and Holter monitoring were performed on 30 patients with hype rtrophic cardiomyopathy and 11 controls. The time constant of heart rate de cline after exercise was calculated. Spectral analysis was performed on Hol ter recordings. The time constant slid not correlate with heart rate, left ventricular end-diastolic pressure, ejection fraction, or wall thickness. T here was no correlation between the rime constant and any mean spectral ind ices ar;er 24 hours in patients. However, the time constant correlated with high frequency component in the night. Nocturnal high frequency component in patients with short time constant was significantly less than in those w ith long time constant, but did not significantly differ from that in contr ols. In conclusion the heart rate decline after exercise does not primarily reflect the severity of hypertrophy or hemodynamic impairment but is assoc iated with nocturnal parasympathetic modulation in patients with hypertroph ic cardiomyopathy.