Influence of infarct-related artery patency on the indexes of parasympathetic activity and prevalence of late potentials in survivors of acute myocardial infarction

Department of Electrocardiography and Electrophysiology, Instituto Nacional de Cardiologia Ignacio Chavez, Mexico City, DF.

OBJECTIVES. The purpose of this study was to determine whether infarct-related coronary artery patency influences myocardial electrical stability as measured by the prevalence of late potentials or heart rate variability. BACKGROUND. Several studies have suggested that loss of vagal activity is associated with an increased incidence of arrhythmic death after myocardial infarction. METHODS. A short-duration, high resolution electrocardiogram (ECG) was performed before hospital discharge in 175 patients with a first myocardial infarction. Seventy-three patients received thrombolytic therapy. All patients underwent coronary angiography. Coronary occlusion was defined as minimal or no anterograde flow. Eighty-eight patients (50.3%) had an occluded infarct-related artery. Sixty-two healthy subjects served as control subjects to determine the normal range of heart rate variability. RESULTS. Comparison between the control group and patients without patency of the infarct-related artery in the time domain and spectral analyses revealed in the latter patients a reduced heart rate variability (p < 0.0001) and a lower power spectrum density in both the 0.05- to 0.15-Hz band (p < 0.0001) and the 0.15- to 0.35-Hz band (p < 0.0001). The heart rate variability in patients with late potentials was lower than in those with a normal signal-averaged ECG. Those patients with spontaneous or thrombolysis-induced reperfusion have less occurrence of late potentials and higher parasympathetic activity than do patients with a closed artery. CONCLUSIONS. This study suggests that the patency of the infarct-related artery determines both the absence of late potentials and the preservation of vagal tone and may explain the reduction in mortality induced by thrombolytic therapy in myocardial infarction.

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