Introduction: Anatomy of the coronary circulation has been of interest to physicians ever since it emerged that mammalian hearts have their own blood supply. Frequent presence of two right coronary artery roots & separate origin of conal branch of right coronary artery or Third Coronary Artery (TCA) is not generally well appreciated, even though it has been evident to anatomists and cardiac surgeons for centuries. Detail knowledge of coronary anatomy & anomalies is necessary to prevent misinterpretation & disastrous complications during increasing coronary intervention & cardiac surgery. The present study describes the angiographic anatomy and prevalence of third coronary artery (TCA) in northern Indian population.

Materials and Methods: 2470 consecutive coronary angiogram of northern Indian population were evaluated to study the anatomy and prevalence of TCA. Patients with congenital heart diseases were excluded. The incidence, position, course of the third coronary artery will be discussed in the present study.

Results: Of the total coronary angiograms evaluated, the mean age was 51.3 (30-76) years. TCA was present in 840 cases (34%). In 74 cases (3%) we found 2 TCA. In most of the cases TCA bifurcated & supply the pulmonary infundibulum & anterior wall of the left ventricle. In 126 cases (5.1%) TCA also reached inferior border of heart supplying the apex.

Conclusions: The frequent presence of TCA in northern Indian population is noted. The area of perfusion of TCA was extensive then usual. Well-developed collateral circulation through TCA may allow diagnostic and therapeutic interventions in patients with coronary artery disease.

Keywords: Coronary Circulation; Third Coronary Artery; Conal Artery; Coronary Angiography; Pulmonary Infundibulum.