Twenty-Four-Hour Spectral Analysis of Heart Rate Variability in Congestive Heart Failure Secondary to Coronary Artery Disease Giancarlo Casolo, MD, PhD, Enrico Balli, MD, Antonio Fazi, MD, Cesare Gori, MS, Angelo Freni, MS, and Gianfranco Gemini, MD

t is well known that heart rate (HR) fluctuates in time and that this variation is closely related to changesin the neural activity to the heart.‘>*Therefore, HR variability representsa noninvasiveparameter for studying the autonomic control to the heart. Recently, it has been shown that HR variability is a powerful independent prognostic factor in patients with coronary artery disease3and a low HR variability count has been found to be related to suddendeath.4Spectrum analysis of HR may provide further information, since HR variability possesses2 major components that have been shown to relate to different patterns of neural control to the heart5j6 Patients with congestive heart failure (CHF) have a complex abnormality of the autonomic control to the heart7 that also affects someHR characteristics8 Theseabnormalities may be determined either by a selectivereduction of the vagal outflow to the heart or by a more complex abnormality. This investigation was undertaken to evaluate the componentsof HR variability in normal personsand patients with CHF, and their 24-hour behavior.