Coronary Flow Reserve During Coronary Angioplasty in Patients With Recent Myocardial Infarction: Relation to Stenosis and Myocardial Viability

Objectives. In the present study, we examined post-stenotic coronary flow before and after percutaneous transluminal coronary angioplasty (PTCA) in patients with and without recent myocardial infarction (MI) and related it to stenosis severity and residual viability. Background. Post-stenotic coronary blood flow velocity reserve (CFVR) has been used with success to estimate functional stenosis severity in patients with stable angina. However, in patients with recent MI, the impaired coronary vasodilator response of the reperfused myocardium may substantially alter the flow dynamics of the infarct-related artery. Methods. Distal coronary flow velocities were recorded before and after PTC in 36 patients at day 13 ± 7 (mean ± SD) after acute MI and in 38 patients without MI. The CFVR was assessed by the ratio of distal hyperemic to baseline average peak velocity, using 0.014-in. Doppler guide wire. Stenosis severity was analyzed by quantitative coronary angiography, and infarct size was assessed scintigraphically. Results. For similar angiographic stenosis severity, pre- and post-PTC values of CFVR were significantly lower in patients with than without MI: 1.22 ± 0.26 versus 1.50 ± 0.45 before PTC (p < 0.05) and 1.72 ± 0.43 versus 2.21 ± 0.74 after PTCA, respectively (p < 0.01). Although CFVR increased significantly (p < 0.0001) after angiographically successful PTC in both study groups, abnormal CFVR (≤2.0) was still observed in 80% of patients with MI and in 44% of those without MI (MI vs. no MI, p = 0.001). Patients with an extensive infarction (relative infarct size ≥50%) and those with small infarction (relative infarct size <50%) had comparable levels of post-PTC CFVR (1.6 ± 0.3 vs. 1.8 ± 0.5, p = NS). Among variety of factors, angiographic stenosis severity was the most important determinant of CFVR in both study groups. Conclusions. In patients with recent MI, CFVR was significantly lower than in those without MI, both before and after PTCA. Besides the presence of this postreperfusion-related impairment of the coronary vasodilating response, CFVR was mainly influenced by stenosis severity and not by residual viability.