Great Vessels of the Heart
The great vessels of the heart are the large arteries and veins that connect directly with the organ, conventionally comprising the superior vena cava, the inferior vena cava, the pulmonary arteries, the pulmonary veins, and the root of the aorta[^c1]. They form the immediate conduits of both circulatory circuits: the venae cavae deliver deoxygenated blood from the body to the right atrium, the pulmonary arteries carry it from the right ventricle to the lungs, the pulmonary veins return oxygenated blood to the left atrium, and the aorta distributes oxygenated blood from the left ventricle to the arterial system[^c2]. Because they are defined by their direct attachment to the heart rather than by size alone, the great vessels are treated as a set distinct from the smaller coronary vessels that supply the heart muscle itself.
The grouping reflects the two circuits these vessels serve. The pulmonary circuit sends blood between the heart and lungs, while the systemic circuit serves the rest of the body. The usual rule that arteries carry oxygen-rich blood and veins oxygen-poor blood has two exceptions among the great vessels: the pulmonary arteries carry oxygen-poor blood and the pulmonary veins carry oxygen-rich blood[^c3]. Each member shares a common three-layer vessel wall — an inner intima, a middle media that is thicker in arteries than in veins, and an outer adventitia[^c7] — though the proportions of the layers differ between the elastic arteries and the great veins.
The great vessels are also defined by their development. They arise from the pharyngeal arch arteries and the early venous channels of the embryo, and in the fetus they are reconfigured by three shunts so that the lungs, which are not used before birth, are bypassed[^c4]. The transition to postnatal circulation at birth — closure of the foramen ovale, the ductus arteriosus, and the ductus venosus — converts this parallel arrangement into the serial circulation of the adult. Many congenital anomalies of the great vessels are, in essence, disturbances of this programme of development.
Functionally, the two circuits operate at very different pressures. The systemic arterial pressure is pulsatile, typically about 120 mmHg systolic and 80 mmHg diastolic[^c5], whereas the pulmonary arterial pressure normally measures about 25 mmHg systolic and 8 mmHg diastolic, for a mean of 15 mmHg[^c6]. The elasticity of the aorta and pulmonary trunk smooths this pulsatile ejection through the Windkessel effect, and the wall structure of each great vessel is matched to the pressure it must withstand. Clinically, the great vessels are the sites of aortic aneurysm and dissection, pulmonary hypertension, coarctation, congenital malformations such as transposition of the great arteries and tetralogy of Fallot, and venous obstruction syndromes, and they are visualised principally by echocardiography and by CT and MR angiography. Survivors of congenital great-vessel disease are now managed under dedicated adult congenital heart disease guidelines that grade each lesion by anatomical complexity and physiological stage[^c8], with the most recent revision published in December 2025.