Third coronary artery in monkey heart.

Investigations were carried out on 55 monkey (Cercopithecus aethiops, Macaca fascicularis) hearts by stereomicroscopic dissection and measurements. Latex-injected specimens and corrosion casts showed that, as in humans, the hearts were usually (in 98.2% of the cases) supplied by two coronary arteries (CAs)--the left (LCA) and the right coronary artery (RCA), and occasionally (in 1.8% of the cases) also by a third one (TCA). Furthermore, the orifice of the TCA was situated in the right aortic sinus at the same level as the RCA and 0.2 mm in front of it. The LCA and the RCA originated from the corresponding aortic sinuses and the external diameter of the LCA was greater [average: 1.65+/-0.39 (SD) mm] than that of the RCA [average 0.94+/-0.15 (SD) mm] and the TCA (0.8 mm). The LCA orifice was more often above (76.3%) than below the free edge of the left aortic valve leaflet. The longitudinal axis of the aortic root and of the initial part of the LCA formed an angle of 45-120 degrees (average: 52 degrees). The orifice of the RCA was usually above (82.3%) the free edge of the right aortic valve leaflet, and less frequently below it (17.7%). The longitudinal axis of the aortic root and of the initial part of the RCA formed an angle of 70-150 degrees (average: 103 degrees). The resemblance of monkey CAs to their human counterparts make them a suitable model for experimental studies on coronary circulation.