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A 72-year-old woman came to our emergency department because of several prolonged episodes of resting angina, caused by emotional stress. Relevant aspects of her medical history were hypertension and hyperlipidemia. A resting 12-lead electrocardiogram showed only minimal T-wave changes in leads I, aVL, and V4 through V6. Although angiography (Fig. 1) showed no substantial coronary atherosclerosis, it revealed an anomalous origin of the left main coronary artery (LMCA) from the right sinus of Valsalva, just above the right coronary artery ostium. The LMCA followed a prepulmonic anterior course, then bifurcated into a large, dominant circumflex coronary artery (Cx) and a small left anterior descending coronary artery (LAD). The ramus intermedius (RI) rose early from the LMCA, gave rise to some conal branches and a major septal branch, and passed intraseptally between the aorta and the outflow tract of the right ventricle, where it narrowed during each systole. The RI crossed under the middle LAD and emerged epicardially to reach the free lateral wall. A 16-slice computed tomographic coronary angiogram (Light-Speed Plus, General Electric Medical Systems; Milwaukee, Wis), performed with an electrocardiogram-gated standard protocol, confirmed the angiographic data (Fig. 2).
Coronary revascularization was deemed unnecessary due to the benign course of the LMCA, LAD, and Cx, and to the intramuscular course of the RI. However, in light of the potential (albeit very rare) ischemic effects of the latter, β-blocker therapy was initiated. The patient's blood pressure stabilized at normal values and her episodes of chest pain decreased in both intensity and frequency. An exercise stress test revealed no ischemia; a stress thallium scan showed a small defect in the distribution territory of the anomalous RI.
Interarterial courses of the LMCA have been associated with exertional angina, syncope, and sudden death.1–3 Our patient's RI abnormality can be considered a muscular bridge. Usually a mild condition, a muscular bridge at most causes ischemia, as with our patient.3 The defect on scintigraphy is likely a true positive result, because angiography showed a muscular-bridge effect of the RI.
A crossing of 2 secondary branches of an obtuse marginal branch has previously been described.3 A case similar to ours—in which the RI also ran intraseptally but a Cx ran alone, retroaortically—is the only reported case, except for ours, in which 2 major anomalous components of the LMCA crossed.4
To the best of our knowledge, ours is the 1st report of an anomalous RI coursing alone in the crista supraventricularis and intraseptally before emerging epicardially to reach the left ventricular free wall, in association with a prepulmonic course for both the LAD and the Cx. In our case, computed tomographic angiography complemented the coronary angiography, confirming the course of the aberrant coronary arteries and their relationship to the other cardiac structures.
We wish to acknowledge Dr. P. Angelini of the Texas Heart Institute for his revision of our paper, and Dr. P. Musso from the Cardiac and Nuclear Medicine Unit, Ospedale Civile di Ivrea, Turin, Italy, who performed the cardiac scintigraphic evaluation.
Address for reprints: Vito Paolillo, MD, Via San Secondo 94, 10128 Turin, Italy E-mail: ti.orebil@olliloap-v