Spontaneous Dissection of Bilateral Internal Mammary Arterial Grafts

Arterial graft dissection is a rare complication of cardiac catheterization. Spontaneous dissection has not been previously described. We report a case of a 49-year-old male with quadruple bypass grafts who presented with acute myocardial infarction due to spontaneous dissection of both internal mammary artery grafts. Case Report. A 49-year-old white male with 1-year status post-quadruple coronary artery bypass grafting, hypertension and hyperlipidemia presented to the Emergency Department with severe angina at rest. He was a current smoker but denied any drug use. His medications included aspirin, atorvastatin, metoprolol, isosorbide dinitrate, ramipril and omeprazole. He appeared to be in moderate distress with a blood pressure of 70/33 mmHg and a normal heart rate of 88 beats/minute. Cardiovascular examination was significant for an S4 gallop and mild bilateral basilar crackles, but no peripheral edema. Electrocardiogram showed sinus rhythm with acute injury pattern in anterior and inferior leads. Chest x-rays showed mildly increased cardiac silhouette without infiltration. The patient underwent an emergent coronary angiography, which showed triple-vessel disease, a patent saphenous vein graft to an obtuse marginal branch and a patent radial artery graft to the posterior left ventricular branch of the right coronary artery. Angiography of the left internal mammary artery (LIMA) graft showed a total occlusion with staining noted in its mid portion (Figure 1A). After intra-arterial nitroglycerin, anterograde flow down the LIMA was restored but a long spiral dissection was observed (Figure 1B). Angiography of the right subclavian artery revealed a total occlusion of the right internal mammary artery graft proximally with a long dissection flap noted from its origin as well (Figure 1C). Cardiovascular surgical consultation was obtained, but medical treatment was opted because of poor distal run-offs. The patient’s hospital course was uneventful and he was discharged in stable condition several days later. Discussion. Spontaneous coronary artery dissection is rare.1 It has been reported in women in the post partum period2 and in patients with Marfan’s syndrome. Internal mammary artery dissection generally occurs as a complication of interventional manipulation.3 In our patient, the dissection (particularly of the right internal mammary artery) was observed prior to catheter engagement. To the best of our knowledge, the spontaneous dissection of an internal mammary arterial graft causing acute myocardial infarction has not been previously reported.

1. Virmani R, Forman MB, Robinowitz, McAllister HA Jr. Coronary artery dissections. Cardiol Clin 1984;2:633–646. 2. Koul AK, Hollander G, Moskovits N, et al. Coronary artery dissection during pregnancy and the post partum period: Two case reports and review of the literature. Cathet Cardiovasc Intervent 2001;52:88–94. 3. Pepine CJ. Diagnostic and Therapeutic Cardiac Catheterization, Third Edition. 1998: pp. 580.