Peculiarities of the ST-segment elevation myocardial infarction morphogenesis after mechanical restoration of epicardial blood flow without ECG signs of reperfusion

Abstract

The aim of the study was to investigate the peculiarities of STEMI morphogenesis after mechanical restoration of epicardial blood flow without ECG signs of reperfusion. The autopsy data of 44 patients with STEMI who died at different times after PCI performed within the first 12 hours (27 cases), or 12–24 hours (17 cases), without ECG signs of reperfusion after the intervention, were analyzed. The comparison group consisted of 85 deceased without reperfusion therapy (RT). Histological examination of the myocardium was performed at following time: within 12 hours, at 13–24 hours, 2–4 days, 5–8 days, 9–15 and 16–22 days. The most common cause of death was acute left ventricular failure (ALVF) both in the group of blood flow restoration without ECG signs of reperfusion, and in the group without RT: 85 % and 79 %, respectively. In each of the two groups the number of deaths occurred in the first 12 hours exceeded one third, half of the patients died in the subsequent 12 hours, two thirds of the deaths occurred within further 2–3 days. The rates of risk factors: older age, anterior and recurrent myocardial infarction, three-vessel lesion of the coronary artery, and a large infarction area were similar in the two groups. From the first hours after PCI, the infarction zone was characterized by hemorrhagic imbibition, numerous injuries of the microcirculatory bed, by the signs of blood flow restoration in damaged vessels appeared from days 2–4, early manifestations of repair from days 5–7. In the MI group without PCI, the hemorrhagic demarcation started on days from 3–4, coagulation necrosis prevailed in the microvascular bed, signs of repair appeared at a later date. Multiple spasms and thromboses in the microvasculature may have been a response to a blood pressure drop that accompanies an acute decrease in the left ventricle contractile function caused by a large infarction area and/or unresolved complications arising during the interventions per se. This mechanism explains the rapid progression of left ventricular failure, the most common cause of death after the interventions with achieving the epicardial blood flow without ECG signs of reperfusion. The revealed microcirculation disorders reflect the absence of myocardial reperfusion, which is more prognostically significant than the restoration of epicardial blood flow.