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Is there increased sympathetic activity in patients with hypertrophic cardiomyopathy?
1Department of Cardiological Sciences, St. George's Hospital Medical School, London, England, United Kingdom.
Insights
Patients with hypertrophic cardiomyopathy show decreased sympathetic nervous system activity, contrary to previous assumptions. This study found reduced sympathetic tone during daily life in these patients, impacting autonomic balance.
Area of Science:
- Cardiology
- Autonomic Nervous System Research
- Medical Physiology
Background:
- Hypertrophic cardiomyopathy (HCM) is often presumed to involve increased sympathetic nervous system activity.
- However, empirical evidence supporting this assumption in HCM patients is limited.
Purpose of the Study:
- To investigate autonomic nervous system (ANS) activity in patients diagnosed with hypertrophic cardiomyopathy.
- To evaluate sympathetic and parasympathetic modulation in HCM using heart rate variability (HRV) analysis.
Main Methods:
- Assessed heart rate variability (HRV) via 24-hour Holter monitoring in 31 HCM patients and 31 controls.
- Utilized spectral analysis (fast Fourier transformation) to calculate total, low-frequency (LF), and high-frequency (HF) HRV components.
- Analyzed HRV in a drug-free state, correlating findings with cardiac dimensions.
Main Results:
- HCM patients exhibited significantly lower normalized low-frequency (LF) HRV components, indicating reduced sympathetic activity (p=0.018).
- Normalized high-frequency (HF) HRV components were significantly increased in HCM patients (p=0.030), suggesting altered autonomic balance.
- The LF/HF ratio was significantly lower in HCM patients (p=0.013), further supporting decreased sympathetic tone.
Conclusions:
- Findings suggest a significant autonomic alteration in HCM patients, characterized by decreased sympathetic tone during normal daily activities.
- Autonomic dysfunction in HCM may be linked to cardiac structural changes, specifically left ventricular end-systolic and left atrial dimensions.
Objectives:
This study aimed to assess autonomic nervous system activity in patients with hypertrophic cardiomyopathy.
Background:
Patients with hypertrophic cardiomyopathy are traditionally thought to have increased sympathetic activity. However, convincing evidence is lacking.
Methods:
Heart rate variability was assessed from 24-h ambulatory electrocardiographic (Holter) recordings in 31 patients with hypertrophic cardiomyopathy and 31 age- and gender-matched normal control subjects in a drug-free state. Spectral heart rate variability was calculated as total (0.01 to 1.00 Hz), low (0.04 to 0.15 Hz) and high (0.15 to 0.40 Hz) frequency components using fast Fourier transformation analysis.
Results:
There was a nonsignificant decrease in the total frequency component of heart rate variability in patients with hypertrophic cardiomyopathy compared with that of normal subjects (mean +/- SD 7.24 +/- 0.88 versus 7.59 +/- 0.57 ln[ms2], p = 0.072). Although there was no significant difference in the high frequency component (5.31 +/- 1.14 versus 5.40 +/- 0.91 ln[ms2], p = 0.730), the low frequency component was significantly lower in patients than in normal subjects (6.25 +/- 1.00 versus 6.72 +/- 0.61 ln[ms2], p = 0.026). After normalization (i.e., division by the total frequency component values), the low frequency component was significantly decreased (38 +/- 8% versus 43 +/- 8%, p = 0.018) and the high frequency component significantly increased (16 +/- 6% versus 12 +/- 6%, p = 0.030) in patients with hypertrophic cardiomyopathy. The low/high frequency component ratio was significantly lower in these patients (0.94 +/- 0.64 versus 1.33 +/- 0.55, p = 0.013). In patients with hypertrophic cardiomyopathy, heart rate variability was significantly related to left ventricular end-systolic dimension and left atrial dimension but not to maximal left ventricular wall thickness. No significant difference in heart rate variability was found between 14 victims of sudden cardiac death and 10 age- and gender-matched low risk patients.
Conclusions:
Our observations suggest that during normal daily activities, patients with hypertrophic cardiomyopathy experience a significant autonomic alteration with decreased sympathetic tone.