Autonomic correlates of late infarct artery patency after first myocardial infarction

Abstract

Occlusion of the infarct-related artery has recently been associated with an increased risk of sudden death, particularly in patients with poor left ventricular function. Depressed heart rate variability (HRV) also identifies postinfarction patients at an increased risk of sudden death. The correlation between infarct artery patency, left ventricular function, and HRV was therefore examined in 186 survivors of a first myocardial infarction. Predischarge coronary angiography and Holter monitoring were carried out in 186 patients with a first acute myocardial infarction. Coronary angiography was performed because of abnormal predischarge exercise test findings. Mean age (56 ± 9 years) and the proportions of type and site of infarction did not differ between patients with occluded or patent arteries or between patients who did or did not undergo coronary angiography. The mean left ventricular ejection fraction (EF) was 55 ± 15% in patients with patent and 49 ± 14% in those with occluded infarct arteries ( p < 0.001), and the EF was <40% in 17% and 28% of the respective groups ( p < 0.05). HRV was <20 U in 7 (18%) of the 39 patients with an EF <40% but in only 7 (5%) of the 147 patients with an EF >40% ( p < 0.02). Among patients with an EF < 40%, there was no difference in the mean EF between patients with patent and those with occluded infarct arteries, but HRV was < 20 U in 6 (22%) of the 27 patients with an occluded artery but in only 1 (8%) of the 12 patients with a patent infarct artery: moreover, mean HRV was 25 ± 17 U and 37 ± 15 U, respectively ( p < 0.05). In patients with an EF ≥ 40%, HRV < 20 U was found in 6% of those with patent and in 4% of those with occluded infarct-related arteries. In conclusion, the status of the infarct-related artery appears to influence the severity of autonomic dysfunction in patients with left ventricular dysfunction after a first myocardial infarction. This subgroup of patients may benefit from prophylactic revascularization or pharmacologic autonomic manipulation.