Positive correlations between quantitative coronary angiography and functional indexes of coronary stenosis are well known in angina pectoris. However, there is little data concerning correlations with acute myocardial infarction (AMI). The objective of this study was to evaluate the differences in correlation of functional severity and luminologic severity between patients with angina and acute myocardial infarction.

The study population consisted of 23 patients with AMI and 25 patients with angina pectoris. We performed intravascular ultrasound (IVUS) and intracoronary pressure measurement following diagnostic coronary angiography, and measured angiographic diameter stenosis (DST), minimal luminal diameter (MLD), minimal luminal area (MLA), and reference area stenosis (r-AST). Additionally, the fractional flow reserve (FFR) was defined by the ratio of the distal mean coronary pressure (Pd) to the aortic mean pressure (Pa).

The IVUS parameters and DST in patients with AMI showed more severe stenosis than seen in patients with angina; MLD (1.37±0.30 mm vs 1.73±0.63 mm, p<0.05), MLA (1.99±0.80 mm 2 vs 3.20±2.25 mm 2, p<0.05), r-AST (79±9% vs 64±24%, p<0.05), DST (78±14% vs 68±21%, p<0.05) respectively. FFR showed no significant difference between the patients with AMI and angina (0.733±0.14 vs 0.729±0.14, p>0.05). FFR was correlated less with r-AST in patients with myocardial infarction than angina ( - 0.55 vs - 0.84). The r-AST in patients with AMI, in order to be the best cut-off values that fit with a FFR<0.75, was higher than seen in patients with angina (83% vs 67%).

FFR in AMI was not significantly different from that seen in angina despite the presence of a significant difference of IVUS parameters between the two patient groups. The functional severity of stenosis in relation to its luminologic severity may be lessened following acute myocardial infarction.