Larger Saphenous Vein Grafts In Relation To Native Artery Are Associated With Reduced Timi Grade 3 Flow But Improved Myocardial Perfusion At 1 Year: A Prevent Iv Analysis

SVG patency is lower with smaller recipient vessel size (<2mm). However, the relationship between the presence of an over-sized or under-sized SVG relative to the native artery (NA) diameter at follow-up has not been fully explored. It was hypothesized that the presence of a larger SVG to NA diameter at 1 year follow-up would be associated with inferior antegrade flow in SVG and NA. Methods : Data were drawn from the PREVENT IV trial, a phase III, multicenter, randomized, double-blind, placebo-controlled trial in which autologous SVGs were treated ex vivo with edifoligide for patients undergoing CABG with repeat angiography within 18 months post CABG and films were evaluated by a core laboratory for SVG diameter, TIMI flow grade (TFG), TIMI frame counts (TFCs) and TIMI myocardial perfusion grade (TMPG). Results: The average ratio of SVG to NA diameter was 1.71±0.45 (n=1,945 in 1,203 patients). As the ratio of the SVG to NA diameter increased, the occurrence of optimal TFG 3 in the SVG was lower (Figure A ) and TFCs were higher (p=0.0001). The frequency of TFG 3 in the NA artery was also lower as the degree of mismatch between SVG and NA diameter increased (p=0.028). Conversely, as the SVG to NA mean diameter ratio increased, the occurrence of TMPG 3 was higher (Figure B ). Conclusion: Larger SVGs in relation to NA at 1 year follow-up were associated with slower flow but improved myocardial perfusion. Greater SVG diameter may be reflective of a larger SVG volume and may explain in part the longer time to fill the SVG; likewise the larger volume of the SVG may explain the apparent improved perfusion of the myocardium. Slower dye transit in large SVGs does not necessarily imply poor perfusion.