Determination of Angiographic (TIMI Grade) Blood Flow by Intracoronary Doppler Flow Velocity During Acute Myocardial Infarction

Abstract

Background This study compared angiographically graded coronary blood flow with intracoronary Doppler flow velocity in patients during percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction. Different TIMI angiographic flow grades (flow grades based on results of the Thrombolysis In Myocardial Infarction trial) have been associated with different clinical results after reperfusion for acute myocardial infarction. However, intracoronary blood flow velocity has not been compared with the angiographic method of determining flow grade in patients. Methods and Results Coronary flow velocity (measured by use of a Doppler guidewire) during primary or rescue PTCA in 41 acute myocardial infarction patients was compared with TIMI grade and cineframes-to-opacification count. Before PTCA, 34 patients had TIMI grade 0 or 1, 5 had TIMI grade 2, and 2 had TIMI grade 3 flow in the infarct artery. Flow velocity was similar among patients with TIMI grades 0, 1, or 2 but was lower than in those with TIMI grade 3 flow (9.4±5.4 versus 16.0±5.4 cm/s for TIMI grades ≤2 versus TIMI grade 3, respectively; P <.05). After PTCA, 1 patient had TIMI grade 1, 5 had TIMI 2, and 35 had TIMI 3 flow. Poststenotic flow velocity increased from 6.6±6.1 to 20.0±11.1 cm/s ( P <.01). TIMI grade 3 flow increased to 21.8±10.9 cm/s ( P <.05 versus before PTCA). Although post-PTCA flow velocity correlated with angiographic cineframes-to-opacification count ( r =.45; P <.02) for TIMI grade 3, there was a large overlap with TIMI grades ≤2 that had low flow velocity (<20 cm/s). Nine of 11 clinical events (unstable angina and coronary artery bypass graft surgery) occurred in patients with low coronary flow velocity. Conclusions Determination of flow velocity after reperfusion may enhance patient characterization and provide the physiological rationale for clinical variations after reperfusion therapy.