Nonlinear Heart Rate Variability:.

The article discusses nonlinear heart rate variability (HRV). The study analyzed 740 24-hour ambulatory ECG tapes from Cardiac Arrhythmia Suppression Trial (CAST), recorded before patients began their assigned antiarrhythmic therapy or placebo. Entry criteria for CAST included an acute myocardial infarction (MI) within 2 years, the presence of left ventricular dysfunction, and six or more ventricular premature complexes (VPCs) per hour. Researchers conclude that decreased longer-term, primarily diurnal, HRV and increased short- to intermediate-term "randomness" of heart rate contribute independently to risk, and adding nonlinear measures to prognostic models that include linear measures improves the predictive value of HRV, particularly in non-coronary artery bypass graft , nondiabetic patients.