Coronary artery fistulae (CAF) are unusual, mostly congenital abnormalities in which coronary blood bypasses the myocardial capillary network and is shunted into a great vessel, cardiac chamber, or other structure. We present a rare variant of a CAF arising from the right coronary artery (RCA) with termination in a large arteriovenous malformation (AVM) of the left anterior descending (LAD) artery that resulted in chronic severe myocardial ischemia. A 58-year-old black woman with a history of hypertension was referred for the evaluation of a severe, cramping, nonradiating, exertional chest pain after starting an exercise program. The only abnormal finding on physical examination was an elevated blood pressure of 148/98 mm Hg. Her resting electrocardiogram (ECG) showed anterolateral T-wave inversions and her peak exercise stress ECG showed inferior and anterolateral 3 mm ST depression. Myocardial perfusion study revealed a reversible 50% perfusion defect involving the apical, anterior, anteroseptal, and inferior segments of the left ventricle. Transient ischemic dilatation of the left ventricular cavity was also noted on stress imaging. Cardiac catheterization showed a left ventricular end-diastolic pressure of 25 mm Hg with an ejection fraction of 70% with no wall motion abnormalities. However, coronary angiography revealed an intramyocardial proximal LAD with a large, grape-like AVM with fistulous drainage from a dominant RCA. The patient had a single-vessel bypass surgery of her LAD AVM using the left internal mammary artery. The RCA fistula was not amenable to ligation. Her postoperative period was complicated by pulmonary embolism, which was adequately managed with anticoagulation. On subsequent follow-up visits, she had improved exercise tolerance with no anginal symptoms. A repeat myocardial perfusion scan performed a few months after the coronary bypass showed normal myocardial perfusion. The exertional chest pain in this patient was due to coronary steal from the large LAD AVM and its fistulous RCA connection, which resulted in severe ischemia of the myocardial segments perfused by the LAD distally. This severe ischemia was successfully resolved with a single-vessel coronary bypass surgery.
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