The artery of Mouchet: blood supply of the septomarginal trabecula in 50 human hearts

SUMMARY The septomarginal trabecula is a muscular structure which transmits the right branch of the atrioventricular bundle. It is usually supplied by a branch from the second anterior septal artery. Anastomoses between the right and left coronary arteries may happen on the septomarginal trabecula. They are of great significance in order to prevent ischemia during a myocardial infarction. Surgeries such as Konno's and Ross' procedures implies in knowledge of these vessels anatomy. The coronary arteries of 50 human hearts were injected with latex and subsequentely dissected with the purpose of identifying the arterial branch that supplied the septomarginal trabecula. The trabecular branch arose from the second anterior septal artery in 38% of cases, and the branch arose from the first anterior septal artery in 26%. One of the hearts had its septomarginal trabecula supplied by the conus arteriosus arteryliterature. Anastomoses between the right and left coronary arteries were found inside the septomarginal trabecula. The right branch of the atrioventricular bundle is subject to a great number of clinical conditions and is often manipulated during surgery, thus, the study of the septal branches of the coronary arteries and the trabecular branch is essential.

Specialized impulse conduction pathway in the alligator heart

Mammals and birds have a specialized cardiac atrioventricular conduction system enabling rapid activation of both ventricles. This system may have evolved together with high heart rates to support their endothermic state (warm-bloodedness) and is seemingly lacking in ectothermic vertebrates from which first mammals then birds independently evolved. Here, we studied the conduction system in crocodiles (Alligator mississippiensis), the only ectothermic vertebrates with a full ventricular septum. We identified homologues of mammalian conduction system markers (Tbx3-Tbx5, Scn5a, Gja5, Nppa-Nppb) and show the presence of a functional atrioventricular bundle. The ventricular Purkinje network, however, was absent and slow ventricular conduction relied on trabecular myocardium, as it does in other ectothermic vertebrates. We propose the evolution of the atrioventricular bundle followed full ventricular septum formation prior to the development of high heart rates and endothermy. In contrast, the evolution of the ventricular Purkinje network is strongly associated with high heart rates and endothermy.