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Identification of patients with hypertrophic cardiomyopathy at high risk for sudden death
A C Chang1, D McAreavey, L Fananapazir
1National Institutes of Health, Bethesda, Maryland, USA.
Insights
Hypertrophic cardiomyopathy patients face sudden death risk. Exercise thallium scintigraphy and electrophysiologic studies help identify high-risk individuals, unlike Holter monitoring or signal-averaged ECGs.
Area of Science:
- Cardiology
- Genetics
- Electrophysiology
Background:
- Hypertrophic cardiomyopathy (HCM) increases sudden cardiac death risk.
- Accurate risk stratification is crucial for managing HCM patients.
- Understanding mechanisms of sudden death and syncope in HCM is evolving.
Purpose of the Study:
- To evaluate the utility of various noninvasive and invasive tests for risk stratification in hypertrophic cardiomyopathy.
- To identify predictors of sudden death and syncope in HCM patients.
- To explore the role of genetic defects in HCM risk assessment.
Main Methods:
- Review of recent studies on risk stratification in HCM.
- Analysis of signal-averaged electrocardiography, cardiac autonomic function, and QT dispersion.
- Evaluation of exercise thallium scintigraphy, Holter monitoring, and electrophysiologic studies.
- Consideration of natural history of genetic defects in HCM.
Main Results:
- Noninvasive tests like signal-averaged ECG and QT dispersion are not useful for risk stratification in HCM.
- Myocardial ischemia on exercise thallium scintigraphy identifies young HCM patients at high risk for cardiac arrest and syncope.
- Nonsustained ventricular tachycardia on Holter monitoring without syncope has a benign prognosis.
- Induced ventricular tachycardia during electrophysiologic study predicts sudden death in adult HCM patients.
Conclusions:
- Exercise thallium scintigraphy and electrophysiologic studies are valuable tools for risk stratification in specific HCM patient groups.
- Certain noninvasive tests lack predictive value for sudden death in HCM.
- Genetic defect characterization will be increasingly important for risk evaluation in hypertrophic cardiomyopathy.
Abstract:
Patients with hypertrophic cardiomyopathy are at increased risk for sudden death. Recent studies have improved our ability to risk-stratify such patients and have elucidated several potential mechanisms of sudden death and syncope. Certain noninvasive tests, such as signal-averaged electrocardiography and measurements of cardiac autonomic function and QT/QT dispersion, are often abnormal in hypertrophic cardiomyopathy, but are not useful for risk stratification. Myocardial ischemia determined by exercise thallium scintigraphy, however, identifies young patients with hypertrophic cardiomyopathy who are at high risk for cardiac arrest and syncope. Nonsustained ventricular tachycardia on ambulatory Holter monitoring in the absence of symptoms of impaired consciousness is associated with a benign prognosis and is not predictive of sudden death. Conversely, ventricular tachycardia induced at electrophysiologic study identifies adult patients with hypertrophic cardiomyopathy who subsequently experience sudden death. Finally, characterization of the natural history of the genetic defects will increasingly become an integral part of risk evaluation in hypertrophic cardiomyopathy.