WHAT IS THE ARTERIAL SUPPLY TO THE HEART?

The heart is supplied by the right and left coronary arteries (Fig. 2-29). The ostia of these vessels are located in the aortic sinuses (of Valsalva) superior to the right and left coronary cusps of the aortic semilunar valve.

FIGURE 2-29 A, Anterior view of the coronary arteries. B, Left anterior oblique arteriogram of right coronary artery. C, Right anterior oblique arteriogram of left coronary artery.

(Drake R, Vogl W and Mitchell A: Gray’s Anatomy for Students. Churchill Livingstone, 2004. Fig. 3-72.)

The right coronary artery travels in the atrioventricular (coronary) sulcus around the right margin of the heart and continues in the posterior interventricular sulcus as the posterior interventricular artery. The posterior interventricular artery issues septal branches that penetrate and supply the posterior one-third of the interventricular septum. Along its course it gives rise to the sinuatrial (sinoatrial) nodal artery, the right marginal artery, and the atrioventricular nodal artery.

The left coronary artery is a short vessel (average length of 2 cm) that promptly divides into the larger anterior interventricular artery (known clinically as the left anterior descending artery) and the circumflex artery. The anterior interventricular artery runs in the anterior interventricular sulcus giving rise to one or more diagonal branches. Diagonal arteries course obliquely across the anterior surface of the left ventricle toward its left border. Septal branches issue from the anterior interventricular artery and penetrate the interventricular septum. The anterior and posterior interventricular arteries anastomose in the vicinity of the apex. The circumflex artery travels in the coronary sulcus and wraps around the left border of the heart. At the left border it issues a marginal artery. Posteriorly, the circumflex artery normally anastomoses with the right coronary artery.

WHAT ARE SOME OF THE VARIATIONS IN THE CORONARY ARTERIES?

Variations in the coronary arteries are common. Some of these variations are:

WHAT IS THE FUNCTION OF THE AORTIC AND PULMONIC SINUSES?

The aortic and pulmonic sinuses are dilatations of the aorta and pulmonary trunk just superior to each of the semilunar cusps. When blood is ejected from each ventricle, its flow creates eddy currents between the open valve cusps and the sinuses. This prevents the valves from being slapped against the outflow arteries. This allows the cusps to close quickly during diastole. If the sinuses were absent, the cusps would be forced against the vascular wall during systole. This would ultimately delay their closing during ventricular relaxation.

WHAT IS THE VENOUS DRAINAGE OF THE HEART?

There are three systems of veins that drain the heart: (1) coronary sinus and its tributaries, (2) anterior cardiac veins, and (3) venae cordis minimae.

WHAT IS THE INNERVATION OF THE HEART?

The heart is innervated by the parasympathetic and sympathetic nervous systems, which form a cardiac plexus. Parasympathetic innervation is provided by the vagus nerves as follows:

Sympathetic innervation to the heart is provided as follows:

WHAT CORONARY ARTERY IS MOST FREQUENTLY NARROWED OR THROMBOSED?

The frequencies at which the coronary arteries are lesioned or thrombosed are:

WHAT BLOOD VESSELS CAN BE USED FOR CORONARY ARTERY BYPASS GRAFTS?

Several vessels (veins and arteries) may be used as coronary artery bypass grafts. Most commonly, the great saphenous vein is used as a graft. The small saphenous vein may be used if the great saphenous vein is unsuitable or unavailable (e.g., harvested for a previous bypass procedure).

The preferred vascular conduits, however, are the right and/or left internal thoracic arteries. Arteries are preferred because they are more likely to remain patent over a 10-year period than venous conduits. The left internal thoracic artery is typically used to bypass the anterior interventricular artery, whereas the right internal thoracic artery is used to bypass the right coronary artery. If the right internal thoracic artery is sufficiently long, it can be grafted to the posterior interventricular artery or branches of the left coronary artery. The radial and gastro-omental arteries can also be used as bypass grafts.

The great saphenous vein begins anterior to the medial malleolus of the tibia as a continuation of the medial marginal vein. It then ascends subcutaneously along the medial leg and thigh. At the height of its ascension, it passes through the fossa ovalis, an opening in the fascia lata, to terminate in the femoral vein. Harvesting the great saphenous vein requires ligation of its tributaries. To prevent injury to the valves in the saphenous graft, the inferior end of the vein graft is anastomosed to the proximal end of the coronary artery and the superior end of the vein is sutured to the distal end of the coronary artery. This maintains anterograde blood flow through the venous graft.

The small saphenous vein begins posterior to the lateral malleolus of the fibula as a continuation of the lateral marginal vein and ends in the popliteal vein.

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