Two different coronary blood flow velocity patterns in thrombolysis in myocardial infarction flow grade 2 in acute myocardial infarction: insight into mechanisms of microvascular dysfunction.

OBJECTIVES We sought to determine which of the two main potential mechanisms underlying Thrombolysis In Myocardial Infarction flow grade 2 (TIMI-2 flow) operate in an individual patient who has had an acute myocardial infarction (AMI). BACKGROUND Systolic flow reversal (SFR) is a specific finding of capillary damage, the no-reflow phenomenon. The coronary blood flow velocity (CBFV) pattern of thromboemboli, however, remains unknown. METHODS Data on 105 patients with AMI (57 with anterior and 48 with nonanterior cases) who underwent a coronary intervention were analyzed. The CBFV was recorded by a Doppler guide wire, and tissue perfusion was assessed with myocardial contrast echocardiography (MCE). RESULTS Study patients were classified into three groups according to TIMI grade and the presence or absence of SFR: 1) TIMI-3 flow (n = 80); 2) TIMI-2 flow with SFR (SFR[+], n = 14); and 3) TIMI-2 flow without SFR (SFR[-], n = 11). Diastolic CBFV was the lowest in SFR(-) (TIMI-3 vs. SFR[+] vs. SFR[-]: 34 vs. 31 vs. 9 cm/s), and the systolic to diastolic CBFV ratio was also the highest in SFR(-) (0.43 vs. -0.18 vs. 0.66). The no-reflow phenomenon documented by MCE was found in all patients in the SFR(+) group, but in only one patient (10%) in the SFR(-) group. Intracoronary thrombus was more frequently found in SFR(-) than in SFR(+) (91% vs. 14%, p < 0.05). CONCLUSIONS At least two different CBFV patterns are noted in patients with reperfused AMI who have TIMI-2 flow. Capillary damage is mostly responsible for SFR(+), and SFR(-) is seen in thromboemboli possibly due to increased coronary arterial resistance.