Can thrombolytic therapy provide beneficial effects additional to epicardial coronary artery recanalization? A study based on coronary pressure measurement.

Abstract

Collaterals provide significant blood supply to the myocardium at risk and the presence of a preserved and adequate collateral network may limit microvascular damage during the occlusion of an epicardial coronary artery. The aim of this study was to evaluate whether thrombolytic therapy (TT) may produce beneficial effects at the level of microvascular circulation in addition to epicardial coronary artery recanalization by using quantitative intracoronary pressure measurement techniques in patients with recent acute myocardial infarction (AMI). Thirty-six patients who presented with AMI and had preinfarction angina pectoris, more than 60% stenosis and thrombolysis in myocardial infarction (TIMI) grade II flow in the infarct-related artery and who underwent a stent implantation procedure within 10 days of AMI were included in this study. Seventeen of 36 patients had received TT (group 1) and 19 had not received TT due to presence of contraindications or late admission (group 2). Quantitative coronary angiography, TIMI frame count (TFC) assessment and intracoronary pressure measurements were performed before and after stent implantation for all patients. Myocardial fractional flow reserve (FFRmyo) was calculated as the ratio of mean distal coronary pressure to mean aortic pressure. During total occlusion with balloon inflation, distal pressure was recorded as coronary wedge pressure (CWP). Collateral flow index (CFI) was determined by the ratio of simultaneously measured CWP to mean aortic pressure. There were no differences between the two groups with respect to mean per cent stenosis and mean FFRmyo both before and after stent implantation. The mean CWP (25.1 +/- 8.6 mmHg compared with 17.2 +/- 6.2 mmHg, P < 0.01) and CFI (0.24 +/- 0.10 compared with 0.16 +/- 0.11, P < 0.01) were significantly higher and mean post-stent corrected TFC (18.8 +/- 3.7 compared with 22.4 +/- 3.1, P < 0.01) was significantly faster in the group of patients who had received TT compared to those who had not. We concluded that destruction degree of collateral circulation and distal microvasculature is lower in patients who had received TT, compared to patients who could not be treated with TT. Besides protective effect on collateral vessels, TT provides even more reperfusion and less destruction of the microvasculature.