Role of collateral circulation in the acute phase of ST-segment-elevation myocardial infarction treated with primary coronary intervention.

AIMS: The role of collateral flow in the first hours of infarction remains unclear. Our aim was to determine whether the presence of coronary collateral flow, as evidenced by angiography, has a beneficial effect on infarct size and left ventricular function in acute myocardial infarction (MI) treated by means of early percutaneous coronary intervention (PCI).
METHODS: Between 1994 and 2001, 1059 patients with acute MI treated with primary PCI, TIMI (Thrombolysis in Myocardial Infarction) 0 or 1 flow at first contrast injection and technically adequate angiograms for collateral flow detection were analysed.
RESULTS: Comparison of collateral flow grades 0, 1, and 2/3 showed that increased collateral flow was associated with a lower incidence of Killip class >/= 2 at presentation (12% vs. 10% vs. 3%, p for trend 0.02), less need for intra-aortic balloon pumping after PCI (17% vs. 13% vs. 5%, p for trend 0.005), better myocardial blush grade (MBG) in infarcts related with the left anterior descending coronary artery (LAD) (MBG3: 14% vs. 18% vs. 34%, p for trend 0.01), and smaller enzymatic infarct size (cumulative lactate dehydrogenase release 36 h after symptom onset [LDHQ(36)]) (1932+/-1531 U/l vs. 1870+/-1458 U/l vs. 1217+/-762 U/l, p for trend 0.041). These beneficial effects were particularly evident in LAD-related infarcts.
CONCLUSION: The presence of angiographically detectable collaterals has a protective effect on enzymatic infarct size and pre- and postintervention haemodynamic conditions in patients with acute MI treated by primary PCI, in particular when Rentrop grade 2/3 is present and the LAD is involved in the infarct.