A 51 year old patient presented with an acute anterior myocardial infarction and had reperfusion therapy with thrombolysis. Electrocardiograms post-thrombolysis showed complete resolution of ST segment elevation with normal creatine kinase values and troponin T concentration of 0.02 μg/l. Because of post-infarct unstable angina the patient underwent cardiac catheterisation. This showed normal left ventricular function with a single left coronary ostium. The left main stem was normal. The left anterior descending artery (LAD) had two severe subtotal occlusions in the proximal and mid thirds (below left, black arrows). Arising from between these two stenoses was the right coronary artery (RCA) which was non-dominant and diseased with atheroma (white arrow). The left circumflex was normal and dominant. Percutaneous coronary intervention (PCI) was undertaken with stenting to the LAD artery. The final angiographic result was excellent with the RCA remaining patent and exiting the stented region of the LAD (below right).

An isolated single coronary ostium is a rare coronary anomaly occurring in 0.024–0.04% of the population. When a single coronary ostium arises from the left sinus of Valsalva, the anomalous RCA usually arises from the LAD artery. Other sites of origin are the circumflex artery, pulmonary trunk, aorta or extra cardiac arteries such as the internal mammary or subclavian arteries. PCI through a single coronary ostium is technically possible. These patients are at a higher risk of ischaemic complications as the single coronary ostium is the myocardium’s sole supply of blood.