Although the time for
contrast material to fill the epicardial artery in the setting of
acute coronary syndromes has been studied extensively, the time for
contrast material to fill the myocardium has not been evaluated. We compared differences in myocardial
contrast material transit among patients with
unstable angina pectoris/non-ST-elevation acute
myocardial infarction (UAP/NSTEAMI) with patients with ST-elevation acute
myocardial infarction (STEAMI). The time it took for
contrast material to first appear and to arrive at peak intensity in the myocardium was compared in 224 patients with STEAMI enrolled in the LIMIT-AMI study versus 430 patients with UAP/NSTEAMI enrolled in the TACTICS-TIMI 18 trial. In patients with STEAMI, there was a delay in both the time for
contrast material to first enter the myocardium (5,619 +/- 1,789 vs 4,663 +/- 1,626 ms, p <0.0001) and the time from entrance to peak blush intensity (2,387 +/- 1,359 vs 1,959 +/- 1,244 ms, p = 0.003) compared with patients with UAP/NSTEAMI. STEAMI remained significantly associated with impaired entrance of
contrast material into the myocardium (p <0.0001) in a multivariate model controlling for known correlates of impaired epicardial flow (presence of
thrombus, percent diameter
stenosis, left anterior descending artery location, and
contrast material inflow in the epicardial artery [corrected TIMI frame count]). The time for
contrast material to enter the myocardium is impaired to a greater degree in STEAMI compared with UAP/NSTEAMI, even after adjusting for other variables known to delay flow in the epicardial artery. These data provide insight into potential mechanistic differences between these 2 clinical syndromes.