Parasympathetic failure and risk of subsequent coronary events in unstable angina and non-ST-segment elevation myocardial infarction

Abstract

Aim Previous animal studies suggested that vagal tone contributes to tonic dilatation of coronary arteries. We hypothesized that low parasympathetic activity might be among the causes of coronary instability in the setting of acute coronary syndrome without ST-segment elevation. Methods and results We studied 172 consecutive patients. Vagal and sympathetic activities were assessed by time domain measures of heart rate variability. PNN50 n=9) than during follow-up (n=23). Extremely low values of parasympathetic activity (pNN50 PConclusions These data show that in acute coronary syndrome without ST-segment elevation, a significant number of patients developing subsequent coronary events have a loss of vagal tone. Simple electrocardiographic variables, as pNN50 <3%, may be of great clinical value in identifying patients at high risk of subsequent coronary events even after apparent clinical stabilization.