Elevations in troponin T and I are associated with abnormal tissue level perfusion: a TACTICS-TIMI 18 substudy. Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Strategy-Thrombolysis in Myocardial Infarction.

BACKGROUND: Cardiac troponin T (cTnT) and I elevations are associated with a higher risk of adverse events, a higher incidence of multivessel disease, complex lesions, and visible thrombus in the setting of non-ST elevation (NSTE) acute coronary syndromes (ACS). Other pathophysiological mechanisms underlying troponin elevation remain unclear. METHODS AND RESULTS: We evaluated the relationship between troponin elevation and tissue level perfusion using the TIMI myocardial perfusion grade (TMPG) in 310 patients with NSTE-ACS in the Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Strategy-Thrombolysis in Myocardial Infarction (TACTICS-TIMI) 18 trial. TMPG 0/1 ("closed" microvasculature) was observed more frequently in cTnT-positive patients both before (58.1% versus 42.1%; P=0.007) and after percutaneous coronary intervention (55.4% versus 35.6%; P=0.004). cTnT levels were higher among patients with TMPG 0/1 versus patients with TMPG 2/3 (0.50 versus 0.31 ng/mL; P=0.006). cTnT-positive patients were more likely to have thrombus (42.5% versus 29.3%), tighter stenoses (72.0% versus 64.8%), and higher rates of TIMI flow grade 0/1 (15.6% versus 7.0%; all P<0.05). TMPG 0/1 remained independently associated with cTnT elevation (odds ratio, 1.81; P=0.02), even after adjusting for epicardial TIMI flow grade, presence of thrombus, and prior myocardial infarction. TMPG 0/1 flow both before and after intervention was associated with increased risk of death or myocardial infarction at 6 months. CONCLUSIONS: Similar to what has been observed in the setting of ST-elevation myocardial infarction, abnormal tissue level perfusion is also associated with adverse outcomes in the NSTE-ACS setting. Independent of the presence of thrombus and abnormal flow in the epicardial artery, impaired tissue level perfusion is associated with a 1.8-fold increased risk of cTnT elevation.

Time for contrast material to traverse the epicardial artery and the myocardium in ST-segment elevation acute myocardial infarction versus unstable angina pectoris/non-ST-elevation acute myocardial infarction.

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.