Background and objectives: Slower blood flow in the setting of acute myocardial infarction (MI) has been related to adverse outcomes, but the relationship of coronary blood flow after percutaneous transluminal coronary angioplasty (PTCA) in the setting of acute coronary syndromes to adverse outcomes and restenosis has not been well described. We sought to evaluate the correlates of pre- and post-PTCA coronary blood flow to shed light on potential modifiable determinants.
Methods: The RESTORE trial (Randomized Efficacy Study of Tirofiban for Outcomes and REstenosis) was a randomized, double-blind, placebo-controlled trial of tirofiban in patients undergoing balloon angioplasty or directional atherectomy within 72 hours of occurrence of either unstable angina pectoris or acute MI. Coronary blood flow was assessed with the corrected TIMI frame count (CTFC), and clinical outcomes were assessed at 30 days.
Results: In addition to tighter and longer minimum lumen diameters (MLDs), the multivariate correlates of slower flow before PTCA also included the presence of thrombus, collaterals, left coronary artery lesion location, acute MI, and >8F catheter size. As well as the above variables, type C and D dissection grades were related to slower post-PTCA CTFC. Death, or the composite of death/MI/coronary artery bypass graft at 30 days, was more frequent among patients with slower post-PTCA CTFCs and those with post-PTCA thrombus. In a multivariate model correcting for reference segment diameter and MLD, the post-PTCA CTFC was an independent predictor of late lumen loss and the follow-up MLD at 6 months. As a single index that integrates functional and anatomical aspects of the post-PTCA results, the ratio of CTFC/MLD was associated with death/MI by 30 days.
Conclusions: In addition to MLD, variables such as the presence of thrombus, left coronary artery lesion location, and dissection grade also are associated with slower coronary blood flow after PTCA. In turn, post-PTCA CTFCs were an independent predictor of late lumen loss and follow-up MLDs. Furthermore, patients who die or who sustain other adverse cardiac events have slower coronary blood flow and greater thrombus burden after PTCA.