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Autonomic function in hypertrophic cardiomyopathy
D M Gilligan1, W L Chan, E Sbarouni
1Department of Medicine (Clinical Cardiology), Royal Postgraduate Medical School, Hammersmith Hospital, London.
Insights
Patients with hypertrophic cardiomyopathy show impaired cardiac autonomic function, specifically reduced parasympathetic activity. This dysfunction is linked to the severity of left ventricular hypertrophy but not syncope occurrence.
Area of Science:
- Cardiology
- Autonomic Nervous System Research
- Clinical Medicine
Background:
- Autonomic dysfunction predicts adverse events post-myocardial infarction.
- Hypertrophic cardiomyopathy (HCM) increases sudden death risk, especially with syncope.
Purpose of the Study:
- To investigate autonomic dysfunction in HCM patients.
- To determine if autonomic dysfunction correlates with syncope in HCM.
Main Methods:
- Assessed autonomic function in 30 HCM patients (15 with syncope, 15 without) and 28 controls.
- Measured parasympathetic activity via heart rate variation during deep breathing and Valsalva ratio.
- Evaluated sympathetic activity through blood pressure responses to handgrip and standing.
Main Results:
- HCM patients exhibited reduced heart rate variation with deep breathing and lower Valsalva ratios, indicating impaired parasympathetic activity.
- No significant differences in autonomic function were found between HCM patients with and without syncope.
- Impaired heart rate variability correlated with increased left ventricular hypertrophy severity (r = 0.39, p = 0.03).
Conclusions:
- HCM patients demonstrate selective impairment of cardiac parasympathetic activity.
- The afferent limb of cardiac autonomic reflexes appears impaired in HCM.
- The severity of this autonomic impairment is associated with the degree of left ventricular hypertrophy.
Background:
Autonomic dysfunction has been found to be a powerful predictor of arrhythmic events and sudden death after myocardial infarction. Hypertrophic cardiomyopathy carries a risk of sudden death and this risk is increased by the occurrence of syncope.
Objectives:
To determine if autonomic dysfunction occurs in patients with hypertrophic cardiomyopathy and if it is associated with the occurrence of syncope.
Patients And Methods:
Autonomic function was measured in 30 patients with hypertrophic cardiomyopathy, 15 with and 15 without a history of syncope, and in 28 healthy volunteers.
Results:
Tests of parasympathetic activity showed that the mean (SD) variation in heart rate during deep breathing was reduced in patients compared with controls, 17 (9) v 22 (9) beats/min, p = 0.03, the Valsalva ratio was also reduced in patients, 1.52 (0.33) v 1.70 (0.36), p = 0.05 but the immediate heart rate response to standing, the 30:15 ratio, was similar in both groups. Tests of sympathetic activity--namely the diastolic blood pressure response to sustained handgrip and the change in systolic blood pressure on standing--did not differ between patients and controls. There was no significant difference in autonomic function between patients with and without a history of syncope. A secondary predetermined analysis showed that the degree of impairment in variation of heart rate with breathing was correlated with the severity of left ventricular hypertrophy, r = 0.39, p = 0.03.
Conclusions:
Patients with hypertrophic cardiomyopathy have a selective impairment of variability of heart rate with deep breathing and the Valsalva manoeuvre indicating decreased cardiac parasympathetic activity. The data suggest that the afferent limb of these reflexes is impaired and that the severity of impairment is related to the degree of left ventricular hypertrophy.