Clinical Case 03—Coronary subclavian steal syndrome: an unusual cause of acute myocardial infarction

A 69-year-old male presented with typical angina while showering. He had history of CABG in 2008 (left internal mammary arterial [LIMA] to the first marginal and intermediate arteries and RIMA to the LAD artery), with preserved biventricular systolic function. On physical examination, an upper-arm systolic blood pressure differential >20mmHg and a decreased pulse amplitude on the left side was found. ECG revealed sinus tachycardia with RBBB, ST-segment depression and inverted T-waves in the lateral and inferior leads. Troponin and BNP levels were elevated. Echocardiogram showed reduced left ventricular ejection fraction (22%) and de novo akinesia of the inferior and posterior walls. The diagnosis of non-ST-segment elevation myocardial infarction was assumed. Coronary angiography revealed patent bypass grafts without disease and a 90% stenosis of the left subclavian artery (LSA) proximal to the ostia of the LIMA, with retrograde flow ‘stealing’ the myocardial blood supply. Ultrasound scan detected systolic reversal of flow in the left vertebral artery, suggesting subclavian-vertebral steal phenomenon. CT-angiography revealed a 14-mm stenosis with a useful lumen of 2 mm in the LSA. A percutaneous balloon angioplasty with stenting of the LSA was performed by the Vascular team, restoring the normal blood supply. Coronary subclavian steal syndrome can manifest as myocardial infarction or heart failure, due to functional LIMA graft failure by inadequate blood supply to the myocardium. Anamnesis and physical examination are fundamental in order not to miss the diagnosis. Subclavian angiography is the gold standard to confirm the diagnosis and can be performed during coronary angiography. Revascularization of the LSA is the definitive treatment. Figure 1Coronary angiography revealed chronic occluded native coronary vessels with patency and no significant disease of the bypass grafts, and high grade (90%) left subclavian artery (LSA) stenosis proximal to the ostia of the LIMA, conditioning the blood flow to the left upper limb and ‘stealing’ the myocardial blood supply because of retrograde flow in the LIMA graft.