Heart rate variability: prognostic implications.

HRV offers information about sympathetic and parasympathetic autonomic function and thus can serve as a measure of risk stratification for serious cardiac arrhythmias and sudden cardiac death. HRV appears to be altered in patients with acute myocardial infarction or diabetic neuropathy and is affected by other physiologic and pathophysiologic processes. Use of HRV measurements requires continued investigation to determine optimal methods and tools by which HRV indices and its variables are analyzed. Long-term studies are required to help correct for differences in values pertaining to age and disease process. Also, studies are needed to determine how patient management strategies will be affected by knowledge gained through HRV analysis and to determine which patient populations should be monitored for HRV analysis and to identify those at risk for sudden cardiac death.