Heart rate variability and cardiac diseases

Heart rate variability (HRV) is a noninvasive methodology for evaluating the autonomic nervous system modulation of the sinoatrial node and to identify patients at risk of cardiac disorders. The contemporary therapeutic use for the HRV analysis is for risk stratification in patients with post-myocardial infarction or heart failure who are prone to have arrhythmic death and who would benefit from implantable cardioverter-defibrillators (ICDs). Although multiple HRV measurements have been developed to achieve a better risk stratification, the HRV measurements have been rarely tested to see whether they harbor a significant power to serve as a practical risk predictor. To date, the only reliable metric to predict the benefit from an ICD is a severely reduced ejection fraction; however, the predictive value of the ejection fraction is relatively low. Because of the high negative predictive value of the HRV, a combination with the ejection fraction may be helpful to identify candidates who are unlikely to benefit from ICD therapy. A more sophisticated risk approach that combines the HRV and other known clinical measures should be developed to provide accurate estimates of the risk to allow patients to make informed treatment decisions. Another requirement is to explore the novel HRV measurements for atrial fibrillation. The prevalence of atrial fibrillation rapidly increases among the aging population and is independently associated with a higher risk of ischemic strokes and excess mortality. The HRV measurements specific for atrial fibrillation may facilitate the risk stratification in such a high-risk population.