Related Experiment Videos
Heart rate variability and ventricular arrhythmia in clinically stable patients with hypertrophic cardiomyopathy
S Uemura1, Y Tomoda, S Fujimoto
1First Department of Internal Medicine, Nara Medical University, Japan.
Insights
Autonomic dysfunction, specifically reduced parasympathetic and increased sympathetic activity, is present in hypertrophic cardiomyopathy (HCM) patients with ventricular arrhythmias. This suggests a need for treatment in HCM patients with nonsustained ventricular tachycardia, even if asymptomatic.
Area of Science:
- Cardiology
- Autonomic Neuroscience
Background:
- Hypertrophic cardiomyopathy (HCM) is a genetic heart condition.
- Autonomic nervous system (ANS) dysfunction may contribute to ventricular arrhythmias in HCM.
- Assessing ANS activity is crucial for understanding arrhythmia risk in HCM patients.
Purpose of the Study:
- To investigate autonomic nervous dysfunction in clinically stable HCM patients.
- To determine the relationship between autonomic nervous activity and ventricular arrhythmias in HCM.
- To compare ANS activity in HCM patients with and without nonsustained ventricular tachycardia (NSVT).
Main Methods:
- Studied 21 HCM patients and 10 healthy controls using 24-h ECG monitoring.
- Measured heart rate variability (HRV) using spectral methods (FFT).
- Assessed parasympathetic (HF) and sympathetic (L/H ratio) activity during day and night.
Main Results:
- No significant HRV differences between HCM patients without NSVT and controls.
- HCM patients with NSVT showed significantly reduced daytime and nighttime HF (parasympathetic activity).
- HCM patients with NSVT exhibited a significantly higher nighttime L/H ratio (sympathetic activity).
Conclusions:
- Clinically stable HCM patients with NSVT demonstrate significant autonomic dysfunction.
- Reduced parasympathetic and increased sympathetic activity are linked to ventricular arrhythmias in HCM.
- HCM patients with NSVT require treatment regardless of clinical manifestations to manage arrhythmia risk.
Abstract:
To investigate whether autonomic nervous dysfunction exists and to determine the relationship between autonomic nervous activity and ventricular arrhythmias in clinically stable patients with hypertrophic cardiomyopathy (HCM), we studied heart rate variability (HRV) in 21 patients with HCM and 10 age-matched healthy control subjects. Patients were divided into 2 groups: HCM I (14 patients without nonsustained ventricular tachycardia, defined as 3 or more consecutive ventricular premature beats) and HCM II (7 patients with nonsustained ventricular tachycardia). HRV was measured on 24-h ECG monitorings using both nonspectral and spectral methods (fast Fourier transform, FFT). We assessed autonomic nervous activity based on high-frequency (HF; 0.15-0.40 Hz, an index of parasympathetic nervous activity) and the low- to high-frequency power ratio (L/H ratio; an index of sympathetic nervous activity) during daytime and night-time separately. There were no significant differences in any index of HRV between the HCM I and control groups. HF in the HCM II group was significantly lower than that of both the HCM I and control groups during the day and at night, whereas the L/H ratio at night-time was significantly higher in the HCM II group than in the HCM I and control groups. These data demonstrate that, in clinically stable HCM patients without nonsustained ventricular tachycardia, autonomic nervous activity was not different to that of healthy control subjects, whereas in HCM patients with nonsustained ventricular tachycardia, parasympathetic nervous activity was reduced throughout the 24-h period, and sympathetic nervous activity at night was increased compared with healthy control subjects. Thus, HCM patients with nonsustained ventricular tachycardia have to be treated even if they do not exhibit significant clinical manifestation.