Posterior Descending Artery as a Continuity from the Left Anterior Descending Artery

The patient was a 44-year-old woman who was admitted to the hospital due to chest pain at rest. Two days later, the patient underwent a coronary angiogram. The angiogram revealed a left anterior descending artery (LAD) following a normal course along the anterior interventricular groove and terminating as a posterior descending artery (PDA) into the posterior interventricular septum (Figure 1). The right coronary artery was a small artery, and the circumflex artery followed a normal course. There were no atherosclerotic lesions in any of the above-mentioned arteries. The posterior descending artery normally arises from the right coronary artery (RCA) in approximately 85% of people; however, in 10–15% of people, it arises from the left circumflex artery.¹ There are few reported cases of the RCA arising from the LAD without an identifiable right coronary ostium.² Another case reported the PDA arising from an aberrant branch of the LAD³ without the intraseptal course described in the case here. To our knowledge, this is the first case of a LAD continuing to the PDA along the posterior interventricular groove, supplying both the anterior and posterior interventricular septum with blood. The clinical importance of this variation is that if the LAD occluded, a severe infarction of the septum and inferior wall would be expected to develop. Such a risk is something an invasive cardiologist must be aware of whenever performing an angiogram on patients who have suffered a large infarction involving both the inferior and anteroseptal walls.

1. Trivellato M, Angelini P, Leachman RD. Variations in coronary artery anatomy: Normal versus abnormal. Cardiovasc Dis 1980;7:357–370. 2. Hughes M.M. Anomalous origin of the right coronary artery from the left anterior descending coronary artery. Cathet. Cardiovasc Diagn 1997;42:308–309. 3. John LC. Anomalous origin of the posterior descending artery from the left anterior descending coronary artery: Cardiac surgeons beware. Heart 2002;87:161.