Novel acute collateral flow index in patients with total coronary artery occlusion during ST-elevation myocardial infarction

Background: The effect of collaterals to occluded coronary arteries during ST-elevation myocardial infarction (STEMI) is unclear. The conventional CVP-based formula to calculate collateral flow index during STEMI yields values higher than in elective patients, which prompted derivation of a modified formula, pertinent in STEMI when left ventricular mean diastolic pressure (LVMDP) is the extravascular pressure limiting collateral flow. We aimed to evaluate this new LVMDP-based acute collateral flow index (ACFI). Methods and Results: The pressure distal to coronary artery occlusion (Pd) was measured during intervention in 111 consecutive STEMI patients, 67 (61%) of whom underwent primary intervention, followed for 58 months. ACFI (0.18±0.17, median 0.15) correlated with both Pd and collateral grade (P<0.0001). Higher creatine kinase levels and white cell counts were measured in the lowest ACFI tertile compared with the highest tertile group (P<0.012). ACFI correlated slightly with early regional but not with global left ventricular ejection fraction or with long-term coronary events and mortality. Conclusions: The ACFI is appropriate for evaluating collateral function during STEMI. Collateral flow during STEMI may marginally limit myocardial damage but had no effect on left ventricular contraction or long-term mortality, most likely because of the low flow provided by emerging collaterals and the high proportion of patients undergoing intervention before the beneficial effect of collaterals could be realized.