Coronary Steal by LIMA Bypass Graft Side-Branches: Physiologic Functional Evaluation and Coil Embolisation

Abstract

Thoracic side branches of the left internal mammary artery (LIMA) has been reported to cause a coronary steal phenomena if not ligated at the time of surgery. The haemodynamic significance of the unligated side branches remains controversial. We present a case of coronary steal phenomena with an objective evidence of ischaemia that resolved after coil embolisation. A 61-year-old male underwent CABG in 1999 for unstable angina. The LAD received a LIMA graft, vein grafts to the diagonal, obtuse marginal and right coronary artery. His presenting symptom prior to CABG was shortness of breath. He remained symptom free until a year ago where he presented with progressive shortness of breath on minimal exertion despite medical therapy. He underwent a diagnostic coronary angiogram, which revealed severe narrowing in the left main stem, ostial circumflex and proximal LAD as well as occluded right coronary artery. All his grafts were patent. The LIMA was also patent but two unligated thoracic branches were noted. The possibility of coronary steal phenomena was entertained and the patient was brought back to the catheterisation laboratory for fractional flow reserve (FFR) study with a view of coiling the unligated side branches if the FFR was positive. After maximal hyperaemia using intravenous adenosine infusion at 140 mcg/kg/min, maximal FFR was calculated at 0.74 in the distal LAD. Both LIMA branches were occluded with balloons and FFR increased to 0.94. Therefore both branches were coiled and repeat FFR was 0.94 after coil embolisation. Six months later, the patient is off his anti-anginal therapy and is symptom free.