Abstract 1748: Clinical and Coronary Angiographic Correlates of Myocardial Perfusion Grade Following Late Mechanical Reperfusion of Occluded Infarct-related Arteries Post-Myocardial Infarction - a Total Occlusion Study of Canada-2 Substudy
Background Myocardial Perfusion Grade (MPG) reflects microvascular flow and is an independent prognostic factor following early reperfusion for MI. Clinical and angiographic correlates of MPG after late reperfusion for a persistently occluded IRA are not known.
Methods TOSCA-2 is an ancillary study of the Occluded Artery Trial, a randomized study of PCI compared to medical therapy alone in asymptomatic high risk patients with occluded IRA 3 to 28 days after MI. The present report focuses on correlates of MPG in 157 TOSCA-2 patients who had evaluable blush post-PCI. MPG was assessed in a core lab using the TIMI system (0- no blush, 1-stain, 2- slow entry/exit, 3-normal).
Results (Table⇓) MPG 0/1 was seen in 21% and MPG 2/3 in 79%. On univariate analysis, MPG 0/1 was associated with thrombolytic therapy during the acute phase of MI, higher heart rate, lower systolic BP, higher CK and CKMB, LAD IRA and lower collateral grade. There was no association between MPG and age, gender, diabetes, prior angina or MI, time from index MI to randomization, Killip Class, or number of diseased vessels. On logistic regression, independent correlates of MPG 0/1 were thrombolytic therapy (OR 6.378, CI 1.314 −30.968; p = 0.022), heart rate (OR for 10 unit change 2.612, 95%CI 1.192–5.720; p = 0.017) and SBP (OR for 10 unit change 0.566, CI 0.346 – 0.923; p = 0.025). Collateral grade was not significantly correlated (OR 0.172, CI 0.024 −1.243; p = 0.081).
Conclusion A high proportion of patients with persistent total IRA occlusion post MI achieved good microvascular flow following late PCI. Poor microvascular flow, however, was associated with use of thrombolytic therapy during the acute MI. This suggests that microvascular obstruction, occurring within the infarct core or resulting from distal embolization, may contribute to the inability to achieve sustained IRA patency following thrombolytic therapy. Underestimation of collaterals by angiography may obscure the relation between collateral flow and MPG.