Percentage of left ventricular myocardial blood flow distribution and revascularization completeness in FASTTRACK CABG

Background: Complete coronary revascularization has significant clinical outcome implications; however, there is no objective, quantitative, or universal definition. Aim: To provide a quantitative personalized assessment of myocardium at risk before and after coronary artery bypass grafting (CABG) surgery. Methods: Percent left ventricular myocardial blood flow distribution (LV%MYO) was derived from coronary CT angiography (CCTA) and used to quantify the myocardium at risk of ischemia in the 16 SYNTAX coronary segments of the 114 patients in the multicenter, prospective FASTTRACK CABG trial. Given each point of the fixed SYNTAX myocardial weighting factor represents 16.7 ​% (1/6) of myocardial blood flow, the myocardial weighting factor of each coronary segment was calculated as 6 ​× ​LV%MYO. The patency of bypass grafts was assessed on 30-day follow-up CCTA, and the residual LV%MYO was obtained by subtracting the LV%MYO in segments anastomosed with non-stenotic grafts from the pre-CABG global LV%MYO. Results: LV%MYO were analyzable in 106 patients (mean age 65.6 (8.9) years, 87 ​% male); 53 had ≥1 total occlusion. The fixed myocardial weighting factor for most SYNTAX coronary segments differs significantly from the weighting factor derived from LV%MYO. The pre-CABG global LV%MYO, and the residual LV%MYO in 96 patients with post-CABG CCTA were 70.1 (18.8)% and 14.0 (15.3)%, respectively. Complete revascularization (residual LV%MYO ≤10 ​%) was achieved in 42 patients (43.8 ​%). The operator's discretion not to graft was the main reason that 106 coronary segments were not revascularized, with graft occlusion accounting for 22.6 ​%. Conclusion: CCTA-derived LV%MYO allows an objective and individualized quantification of the myocardium at risk, facilitating prospective prediction and retrospective assessment of the completeness of revascularization in CABG patients.