Assessment of coronary artery bypass graft disease using cardiovascular magnetic resonance determination of flow reserve.

Abstract

The purpose of this study was to assess the value of cardiovascular magnetic resonance (CMR)-determined graft flow and flow reserve in differentiating significant from non-significant vein graft disease. In patients after coronary artery bypass grafting (CABG), non-invasive testing may be helpful in the detection of recurrent graft disease. Randomly selected patients (n = 21) scheduled for X-ray angiography because of recurrent chest complaints after CABG were included for evaluation of vein grafts (n = 40) by CMR. Three-dimensional contrast-enhanced CMR angiography was performed and followed by flow measurements at rest and during hyperemia in patent grafts only. Flow reserve was calculated when resting flow exceeded 20 ml/min. Analysis was based on four categories defined by X-ray angiography: occluded grafts (n = 3), grafts with stenosis >50% (n = 19), grafts with stenosis <50% with diseased graft run-off (n = 8), and grafts with stenosis <50% and normal run-off (n = 10). The CMR angiography demonstrated occlusion of three grafts. In nine of the 37 patent grafts, basal blood flow was <20 ml/min, all demonstrating significant stenosis at X-ray angiography. In grafts with resting flow >20 ml/min (n = 28), flow reserve significantly differed between grafts without stenosis and grafts with significant stenosis or with diseased run-off (2.5 +/- 0.7 vs. 1.8 +/- 0.9, p = 0.04). An algorithm combining basal volume flow <20 ml/min and graft flow reserve <2 had a sensitivity and specificity of 78% and 80% respectively for detecting grafts with significant stenosis or diseased run-off. This feasibility study showed that quantification of flow and flow reserve by CMR may serve as a non-invasive adjunct to differentiate between vein grafts without stenosis and grafts with significant stenosis or diseased run-off.