Persistent angina uncovers unusual communication between the left anterior descending and circumflex arteries.

A 55-year-old man had presented with progressive dyspnea and chest pain on exertion. The patient underwent a treadmill stress echocardiogram which reproduced his symptoms. However, no regional wall motion abnormalities were documented and the stress test was read as negative. He had achieved 10.0 METs on the Bruce protocol (double product 25 988) and had a resting ejection fraction of 62% that improved to 80% with stress. Despite medical optimization with β blockade and long acting nitrates, the patient continued to have significant symptomatology while engaged in activities of daily living. He was referred for coronary angiography because of ongoing angina. Angiography revealed that the left main coronary artery had a 70% stenosis and led to a diminutive left circumflex and ramus intermedius arteries. There was an arterial connection bridging from the ramus intermedius connecting to an anomalous left anterior descending artery (LAD) which filled both anterograde and retrograde (Figure 1). The ostium of the LAD could not be initially located despite extensive effort. To further characterize the coronary anatomy for planning revascularization, a contrast-enhanced CT coronary angiogram with 3-dimensional reconstruction was obtained (Movie I in the online-only Data Supplement). This confirmed the origin of the LAD from the right aortic sinus and ruled out an aortic intramural component or slit-like orifice. This artery coursed behind the right ventricular outflow tract and in the interventricular septum before reaching its perfusion territory (Figure 2). Coronary angiography was subsequently used to reconfirm full patency of the LAD before assessing the LM stenosis with intravascular ultrasound (Movie II in the online-only Data Supplement) and fractional flow reserve. Despite the presence of collateral flow from the anomalous LAD, the fractional