Background: Although the Thrombolysis in Myocardial Infarction flow grade system is a widely used index of coronary blood flow, it has important limitations. We recently described a new continuous measure of blood flow in native coronary arteries, the Thrombolysis in Myocardial Infarction frame count (TFC), and sought to extend this method to coronary artery bypass grafts.
Methods: We retrospectively analyzed cinefilms of patients' status after coronary artery bypass grafting, excluding patients with recent myocardial infarction and grafts with stenoses in the graft or native vessel. We counted the cineframes required for dye to travel from the ostium of the graft to the graft anastomotic site (TFCg) and to a standardized distal coronary landmark (TFC).
Results: For all vein grafts combined, TFCg was 19.2+/-5.7 frames (mean+/-SD, n = 93) and the TFC was 33.9+/-8.0 frames (n = 67). The upper limits for "normal" flow, calculated from the 95% confidence intervals, were 31 frames for TFCg and 50 frames for TFC.
Conclusions: The Thrombolysis in Myocardial Infarction frame counting method has now been extended to normal saphenous vein grafts, and normal reference values are provided.