CORONARY ARTERIES Limited Flow Reserve in Non-Obstructed Bypass Grafts Supplying Infarcted Myocardium: Implications for Cardiovascular Magnetic Resonance Imaging Protocols

We evaluated flow reserve in non-obstructed bypass grafts supplying infarcted and non-infarcted myocardium. Bypass grafts were examined by phase-contrast flow measurements and myocardial viability was assessed with late enhancement technique. Flow reserve was higher in bypasses supplying normal myocardium compared to those supplying infarcted myocardium (2.9 vs. 1.5, p <.0001). This difference remained significant after adjusting for co-variables. Bypass grafts supplying infarcted myocardium were more likely to have lower flow reserve than those supplying normal myocardium (flow reserve ≤ 2, 84 % vs 18%, p =.0003). Flow reserve is reduced in non-stenosed bypasses supplying infarcted myocardium, likely due to altered microcirculation. Thus, cardiovascular magnetic resonance based bypass assessment must include myocardial viability testing