BAU-P1-VASCULATURE OF THE HEART-2023.pdf

VASCULATURE OF THE HEART 1 • The entire body must be supplied with nutrients and oxygen via the circulatory system and the heart is no exception. • The coronary circulation refers to the vessels that supply and drain the heart. • Coronary arteries are named as such due to the way they encircle th...

VASCULATURE OF THE HEART 1 • The entire body must be supplied with nutrients and oxygen via the circulatory system and the heart is no exception. • The coronary circulation refers to the vessels that supply and drain the heart. • Coronary arteries are named as such due to the way they encircle the heart, much like a crown. 2 3 Naming -Coronary Arteries • There are two main coronary arteries which branch to supply the entire heart. • They are named the left and right coronary arteries, and arise from the left and right aortic sinuses within the aorta. 4 5 • The aortic sinuses are small openings found within the aorta behind the left and right flaps of the aortic valve. • When the heart is relaxed, the back-flow of blood fills these valve pockets, therefore allowing blood to enter the coronary arteries. 6 Naming -Coronary Arteries • The left coronary artery (LCA) initially branches to yield the left anterior descending (LAD), also called the anterior interventricular artery. • The LCA also gives off the left marginal artery (LMA) and the left circumflex artery (Cx). 7 Naming -Coronary Arteries • In ~20-25% of individuals, the left circumflex artery contributes to the posterior interventricular artery (PIv). • The right coronary artery (RCA) branches to form the right marginal artery (RMA) anteriorly. • In 80-85% of individuals, it also branches into the posterior interventricular artery (PIv) posteriorly. 8 Naming -Coronary Arteries 9 Naming -Cardiac Veins • Blood travels from the subendocardium into the thebesian veins, which are small tributaries running throughout the myocardium. • These in turn drain into larger veins that empty into the coronary sinus. 10 Naming -Cardiac Veins • The coronary sinus is the main vein of the heart, located on the posterior surface in the coronary sulcus, which runs between the left atrium and left ventricle. • The sinus drains into the right atrium. • Within the right atrium, the opening of the coronary sinus is located between the right atrioventricular orifice and the inferior vena cava orifice. 11 Naming -Cardiac Veins 12 Naming -Cardiac Veins There are five tributaries which drain into the coronary sinus: • The great cardiac vein is the main tributary. • It originates at the apex of the heart and follows the anterior interventricular groove into the coronary sulcus and around the left side of the heart to join the coronary sinus. 13 • The small cardiac vein is also located on the anterior surface of the heart. • This passes around the right side of the heart to join the coronary sinus. 14 • Another vein which drains the right side of the heart is the middle cardiac vein. • It is located on the posterior surface of the heart. 15 The final 2 cardiac veins are also on the posterior surface of the heart: • On the left posterior side is the left marginal vein. • In the center is the left posterior ventricular vein which runs along the posterior interventricular sulcus to join the coronary sinus. 16 Distribution of the Coronary Arteries • In general, the area of the heart which an artery passes over will be the area that it perfuses. • The RCA passes to the right of the pulmonary trunk and runs along the coronary sulcus before branching. 17 18 Distribution of the Coronary Arteries • The right marginal artery arises from the RCA and moves along the right and inferior border of the heart towards the apex. • The RCA continues to the posterior surface of the heart, still running along the coronary sulcus. • The posterior interventricular artery then arises from the RCA and follows the posterior interventricular groove towards the apex of the heart. 19 BRANCHES OF RCA • Large Branches • marginal • Post-interventricular • Small branches: • Right atrial • Infundibular • Nodal – in 60% cases • Terminal Anterior schematic diagram of heart shows course of dominant right coronary artery and its tributaries. AV = atrioventricular, PDA = posterior descending artery, RCA = right coronary artery, RV = right ventricular, SA = sinoatrial Distribution of the Coronary Arteries • The LCA passes between the left side of the pulmonary trunk and the left auricle. • The LCA divides into the anterior interventricular branch and the circumflex branch. 22 Distribution of the Coronary Arteries • The anterior interventricular branch (LAD) follows the anterior interventricular groove towards the apex of the heart where it continues on the posterior surface to anastomose with the posterior interventricular branch. • The circumflex branch follows the coronary sulcus to the left border and onto the posterior surface of the heart. • This gives rise to the left marginal branch which follows the left border of the heart. 23 BRANCHES: • Large Branches: • • Anterior interventricular Branch to the diaphragmatic surface of the left ventricle • Small Branches: ― Left atrial ― Pulmonary ― Terminal Dominant left coronary artery anatomy. Left anterior oblique schematic diagram of dominant left coronary artery anatomy, including left anterior descending artery and left circumflex artery tributaries, is shown. AVGA = atrioventricular groove artery, PDA = posterior descending artery. 26 COLLATERAL CIRCULATION • Cardiac anatomosis: The two coronary arteries anastomose in the myocardium. • Extra cardiac anastomosis: The coronary arteries anastomose with the • Vasa vasorum of the aorta, • Vasa vasorum of pulmonary arteries, • Internal thoracic arteries • The bronchial arteries • Phrenic arteries. • These channels open up in the emergencies when the coronary arteries are blocked. CORONARY ARTERY DOMINANCE • The artery that gives the posterior interventricular artery determines the coronary dominance. • If the posterior interventricular artery is supplied by the right coronary artery (RCA), then the coronary circulation can be classified as "right-dominant". • If the posterior interventricular artery is supplied by the circumflex artery (CX), a branch of the left artery, then the coronary circulation can be classified as "left-dominant". • If the posterior interventricular artery is supplied by both the right coronary artery (RCA) and the circumflex artery, then the coronary circulation can be classified as "codominant". FUNCTIONAL DIVISION • Large coronary arteries (epicardial cortonary arteries) - lies on epicardial surface, • conduct blood with little resistance. • Small coronary arteries – descends into myocardium, are of two types: • subepicardial vessels and • subendocardial vessels. • Small coronary arteries are the principle resistance vessels of the heart, change in their diameter regulate the coronary blood flow Clinical Relevance: Coronary Artery Disease • Coronary artery disease or coronary heart disease (CHD) is a leading cause of death worldwide. • It describes a reduction in blood flow to the myocardium and has several causes and consequences. • CHD can result in reduced blood flow to the heart as a result of narrowing or blockage of the coronary arteries. • This may be due to atherosclerosis, thrombosis, high blood pressure, diabetes or smoking. • All these factors lead to a reduced flow of blood to the heart through physical obstruction or changes in the vessel wall. 30 31 Clinical Relevance: Coronary Artery Disease • Angina pectoris is one consequence of CHD. • Angina pectoris describes the transient pain a person may feel on exercise as a result of lack of oxygen supplied to the heart. • This pain is felt across the chest but is quickly resolved upon rest. • Exercise is a trigger for angina as the coronary arteries fill during the diastolic period of the cardiac cycle. • On exercising, the diastolic period is shortened meaning that there is less time for blood flow to overcome a blockage in one of the coronary vessels in order to supply the heart. 32 • Angina pectoris is one consequence of CHD. • Angina pectoris describes the transient pain a person may feel on exercise as a result of lack of oxygen supplied to the heart. • This pain is felt across the chest but is quickly resolved upon rest. • Exercise is a trigger for angina as the coronary arteries fill during the diastolic period of the cardiac cycle. • On exercising, the diastolic period is shortened meaning that there is less time for blood flow to overcome a blockage in one of the coronary vessels in order to supply the heart. 33 • If left untreated, angina can soon progress to more severe consequences, such as a myocardial infarction. • The sudden occlusion of an artery results in infarction and necrosis of the myocardium. • This means a section of the heart is unable to beat (which part of the heart depends on which artery has become occluded). • The ECG leads on which an MI change appears can be used to locate the artery that had been occluded as shown in the table. 34 ECG Findings in CHD 35 Diagnosis and Treatment of Coronary Artery Disease • A blockage in a coronary artery can be rapidly identified by performing a coronary angiogram. • The imaging modality involves the insertion of a catheter into the aorta via the femoral artery. • A contrast dye is injected into the coronary arteries and x-ray based imaging is then used to visualise the coronary arteries and any blockage that may be present. 36 • Immediate treatment of a blockage can be performed by way of a coronary angioplasty, which involves the inflation of a balloon within the affected artery. • The balloon pushes aside the atherosclerotic plaque and restores the blood flow to the myocardium. • The artery may then be supported by the addition of an intravascular stent to maintain its volume. 37 38 39 40 Tabular Overview of the Vasculature of the Heart 41