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Heart rate decline after exercise in patients with hypertrophic cardiomyopathy
T Matsushita1, Y Tanaka, O Horinouchi
1Second Department of Internal Medicine, Kagoshima University Faculty of Medicine, Kagoshima, Japan. tmatushita@cvmed.stanford.edu
Insights
Heart rate recovery in hypertrophic cardiomyopathy is linked to nocturnal parasympathetic activity, not disease severity. This finding offers new insights into autonomic function in hypertrophic cardiomyopathy patients.
Area of Science:
- Cardiology
- Autonomic Nervous System Research
- Exercise Physiology
Background:
- Hypertrophic cardiomyopathy (HCM) is a complex cardiac condition.
- Understanding autonomic dysfunction in HCM is crucial for patient management.
- Heart rate recovery (HRR) post-exercise is a marker of autonomic function.
Purpose of the Study:
- To investigate the relationship between heart rate decline after exercise and autonomic modulation in hypertrophic cardiomyopathy.
- To determine if HRR reflects disease severity or hemodynamic status in HCM patients.
Main Methods:
- Submaximal exercise testing, echocardiography, and 24-hour Holter monitoring were conducted.
- Time constant of heart rate decline and spectral analysis of heart rate variability were calculated.
- Correlations between HRR parameters and clinical/hemodynamic measures were assessed.
Main Results:
- The time constant of heart rate decline did not correlate with standard measures of HCM severity or left ventricular function.
- A significant correlation was observed between the time constant and the high-frequency component of heart rate variability during nighttime.
- Nocturnal heart rate variability differed between patients with short versus long time constants, suggesting altered parasympathetic modulation.
Conclusions:
- Heart rate recovery after exercise in hypertrophic cardiomyopathy is primarily associated with nocturnal parasympathetic modulation.
- HRR in HCM does not appear to be a direct reflection of the degree of hypertrophy or hemodynamic impairment.
- These findings highlight the role of autonomic nervous system regulation in the post-exercise cardiovascular response in HCM.
Abstract:
To evaluate the heart rate recovery, submaximal exercise, echocardiographic examination, and Holter monitoring were performed on 30 patients with hypertrophic cardiomyopathy and 11 controls. The time constant of heart rate decline after exercise was calculated. Spectral analysis was performed on Holter recordings. The time constant did not correlate with heart rate, left ventricular end-diastolic pressure, ejection fraction, or wall thickness. There was no correlation between the time constant and any mean spectral indices over 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 with long time constant, but did not significantly differ from that in controls. In conclusion, the heart rate decline after exercise does not primarily reflect the severity of hypertrophy or hemodynamic impairment but is associated with nocturnal parasympathetic modulation in patients with hypertrophic cardiomyopathy.