Lec4. Coronary Arteries & Venous Drainage PDF

Dr Melad Naim Kelada Associate professor Anatomy and Embryology department Faculty of Medicine, Alexandria University Faculty of Medicine, Beirut Arab Universiy 1  The Right Coronary Artery (RCA) the right coronary a...

Dr Melad Naim Kelada Associate professor Anatomy and Embryology department Faculty of Medicine, Alexandria University Faculty of Medicine, Beirut Arab Universiy 1  The Right Coronary Artery (RCA) the right coronary artery arises from the (right coronary) aortic sinus. It passes between the pulmonary trunk and the right auricle. the RCA descends in coronary sulcus to the acute margin of the heart, curving around it into the posterior part of the sulcus, passing towards the crux of the heart. 2 As the right coronary approaches the crux, it gives the posterior interventricular artery , which occupies the posterior interventricular sulcus, 3 4 ❖ Branches: 1. the right conus artery. It ramifies anteriorly on the lowest part of the pulmonary trunk and upper part of the right ventricle. 2. Atrial branches. multiple small arteries to the right atrium. 3.The artery of the sinoatrial node (SAN artery) It arises from the right coronary artery in about 65% and from the circumflex branch of the left coronary in 35% of people. 5 ▪ SAN artery passes backwards till reaching the superior vena cava where it either curves posterior or anterior or forms an arterial loop around that vessel, from which small rami branch off to supply the right atrium. ▪ A large branch of these vessels passes into the sinuatrial node and traverses it. ▪ The SAN artery supply the atria and the SAN 6 4. Anterior ventricular branches usually two or three, ramify towards the cardiac apex supplying the RT ventricle. 5. The right marginal artery is greater in caliber than the other anterior ventricular arteries and long enough to reach the apex. Supplying the RV and apex of heart. 7  6. Posterior ventricular branches commonly two, arise from the posterior segment of the right coronary artery between the right border and crux and supply the diaphragmatic aspect of the right ventricle. 8  7. Posterior interventricular artery or posterior descending artery (PDA) is singular in about 70% of hearts, otherwise being accompanied by parallel branches on both sides of the sulcus. It supply both ventricles. The posterior interventricular artery gives numerous septal branches which are short vessels, supply the posterior third of the interventricular septum and do not usually reach the apical parts of the septum. This septal branches anastomose with the septal branches of the AIV. The PDA anastomose with the anterior interventricular artery 9 10 8. AV nodal artery Arise from RCA in 80 %of people. Usually it is the first septal branch of the PDA and pass to the AVN. This artery may arise from the circumflex of LCA in 20% of subjects. 11 Areas supplied by the right coronary 1. The right atrium. 2. Most of right ventricle. 3. Part of the left ventricle (the diaphragmatic surface). 4. Part of the IV septum, usually the posterior third. 5. The SA node (in approximately 60% of people). 6. The AV node (in approximately 80% of people) 12  Left coronary artery The left coronary artery is usually larger in caliber than the right, and supplies a greater volume of myocardium, including almost all the left ventricle and atrium. The left main coronary trunk arises from the left aortic sinus. 13 ❑It lies between the pulmonary trunk and the left auricle , emerging to reach the atrioventricular sulcus, in which it turns to the left. ❑Here it usually divides into two main branches: the anterior interventricular artery and the circumflex artery. 14  Anterior interventricular artery The anterior interventricular or left anterior descending branch (LAD) is commonly described as a continuation of the left coronary artery. It descends obliquely forwards and to the left in the interventricular sulcus. accompanied by the great cardiac vein and its tributaries. 15  The artery reaches the apex of the heart and commonly turn around the apex into the posterior (inferior) interventricular sulcus. It passes along the sulcus for a few centimeters to meet the PDA. 16 ❖Branches of the anterior interventricular artery: 1. Anterior left ventricular branches: these are large vessels from 2 to 9 in number reaching the rounded left border of the heart. (Diagonal) 17  2. A small left conus artery leaves the anterior interventricular artery near its beginning, and anastomose with the conus branch of the right coronary 3. The anterior septal branches leave the anterior interventricular artery almost perpendicularly. passing backwards and downwards in the substance of the septum, of which they usually supply about the anterior two thirds. 4. Small posterior septal rami supply the posterior third of the septum for a variable distance from the apex. 18 19  Circumflex artery The circumflex artery (Cx), usually comparable with the anterior interventricular artery in caliber. curves to the left border of the heart in the coronary sulcus, continuing round into the posterior part of the sulcus to terminate a little to the left of the crux. 20 ❖Branches of the circumflex artery: 1. the left (obtuse) marginal artery: a large branch, arises ramifies over the rounded ‘obtuse' margin, supplying much of that region of the left ventricle; it usually reaches the apex of the heart. 2. Smaller anterior and posterior ventricular branches of the circumflex artery also supply the left ventricle. 21 ❖inconstant branches of the circumflex artery/ 1. The artery to the sinuatrial node (SAN) is a branch of the circumflex artery in about 35% of hearts. This artery passes over the left atrium, supplying it and then encircling the termination of the superior vena cava, as in the case of a nodal artery from the right coronary artery. Similarly, also, it sends a large branch into the sinuatrial node, but is largely an atrial vessel in distribution 22 2. The artery to the atrioventricular node the terminal branch in 20%, arises near the crux, in which case the circumflex usually supplies the posterior interventricular artery, an example of so-called ‘left dominance'. 23 Areas supplied by left coronary 1. The left atrium. 2. Most of the left ventricle. 3. Part of the right ventricle. 4. Most of the IVS (usually its anterior two thirds) 5. The SA node (in approximately 40% of people). 6. AV node in 20% of people 24 Coronary artery dominance Dominance of the coronary arterial system is defined by which artery gives rise to the posterior interventricular (IV) (PDA). Dominance of the right coronary artery occur in 67% ; the right coronary artery gives rise to the large posterior interventricular branch. 25 26 Variations of the Coronary Arteries Variations in the branching patterns and distribution of the coronary arteries are common. In the most common right dominant pattern, present in approximately 67% of people. the RCA and LCA share about equally in the blood supply of the heart. In approximately 15% of hearts, the LCA is dominant in that the posterior IV branch is a branch of the circumflex artery. There is codominance in approximately 18% of people, in which branches of both the right and left coronary arteries reach the crux of the heart and give rise to branches that course in or near the posterior IV groove. A few people have only one coronary artery. In other people, the circumflex branch arises from the right aortic sinus. Approximately 4% of people have an accessory coronary artery. 27 Coronary Collateral Circulation. The branches of the coronary arteries are generally considered to be functional end arteries (arteries that lacking efficient anastomoses from other large branches to maintain viability of the tissue should occlusion occur). However, anastomoses do exist between branches of the coronary arteries and between these arteries and extracardiac vessels such as thoracic vessels. Anastomoses exist between the terminations of the right and the left coronary arteries in the coronary sulcus and between the IV branches around the apex in approximately 10% of apparently normal hearts. 28  Cardiac veins ❖ The heart is drained by: The heart is drained mainly by veins that empty into the coronary sinus and partly by small veins that empty directly into the right atrium. A. Coronary sinus and its tributaries. the coronary sinus, the main vein of the heart, is a wide venous channel that runs from left to right in the posterior part of the coronary sulcus. 29  2 or 3 cm long, in between the left atrium and ventricle. It opens into the right atrium between the opening of the inferior vena cava and the tricuspid valve; the opening is guarded by a valve to prevent the regurgitation of the blood during atrial contraction. 30  The tributaries of the coronary sinus are: 1. Great cardiac vein. 2. Middle cardiac vein. 3. Small cardiac vein. 4. Posterior vein of the left ventricle. 5. Oblique vein of the left atrium. 31  The tributaries of the coronary sinus are: 1. Great cardiac vein. It begins at the cardiac apex, ascends in the anterior interventricular groove to the coronary sulcus passing to the left and posteriorly to enter the coronary sinus at its origin. It receives tributaries from the left atrium and both ventricles, including the large left marginal vein that ascends along the left border(obtuse border) of the heart. It drains most of the areas supplied by the LCA. 2. Middle cardiac vein. It begins at the cardiac apex, and runs back in the posterior interventricular groove to end in the coronary sinus near its end. 3. Small cardiac vein accompanies the right marginal branch of the RCA. The middle and small cardiac veins drain most of the areas commonly supplied by the RCA. 32 4. Posterior vein of the left ventricle. It is found on the diaphragmatic surface of the left ventricle a little to the left of the middle cardiac vein. It usually opens into the center of the coronary sinus, but sometimes opens into the great cardiac vein. 5. Oblique vein of the left atrium. It descends obliquely on the back of the left atrium to join the coronary sinus near its end. 33  The coronary sinus and its tributaries return blood to the right atrium from the entire heart (including its septa) except for the anterior region of the right ventricle and small, variable parts of both atria and the left ventricle. 34 B. Anterior cardiac veins: Usually two or three, sometimes even five; they cross the right part of the coronary sulcus, passing deep or superficial to the right coronary artery. They end in the right atrium. The anterior cardiac veins drain an anterior region of the right ventricle. C. Small cardiac veins (Thebesius' veins) ( venea cordis minimi): very small veins and their numbers and size are highly variable. They open directly into all cardiac chambers. They are numerous in relation to the right atrium and right ventricle, but they are rare in the left atrium and left ventricle. 35 36 Related additional readings Atherosclerosis Coronary heart disease Referred cardiac pain 37 References Anatomy: Moore KL, Dalley AF, Anne MR. Clinically Oriented Anatomy. Lippincott, Williams & Wilkins, 7th ed. 2014. Embryology: Sadler TW. Langman’s Medical Embryology. Wolters Kluwer, 13th ed. 2015. 38