Coronary-Circulation-A-Vital-Pathway.pptx

coronary artery disease, coronary circulation

1. Coronary Circulation: A Vital Pathway CORONARY CIRCULATION About one-third of all deaths in industrialized countries of the Western world result from coronary artery disease, and most older adults have at least some impairment of the coronary artery circulation. by Shama Khan

2. Anatomy of the Coronary Arteries Right Coronary Artery Supplies blood to the right atrium, right ventricle, and the posterior portion of the left ventricle. Left Coronary Artery supplies mainly the anterior and left lateral portions of the left ventricle,

3. Blood Supply to the Heart 1 Oxygenated Blood The aorta delivers oxygen-rich blood to the coronary arteries. 2 Heart Muscle Blood flows through the capillaries, delivering oxygen and nutrients to the heart muscle. 3 Deoxygenated Blood Deoxygenated blood returns to the heart through the coronary veins.

4. Blood Supply to the Heart 1 Most of the coronary venous blood flow from the left ventricular muscle returns to the right atrium of the heart by way of the coronary sinus , which is about 75% of the total coronary blood flow. 2 Most of the coronary venous blood from the right ventricular muscle returns through small anterior cardiac veins that flow directly into the right atrium, not by way of the coronary sinus. 3 A very small amount of coronary venous blood also flows back into the heart through very minute thebesian veins , which empty directly into all chambers of the heart.

5. 1 The normal coronary blood flow in the resting person averages 70 ml/min/100 g of heart weight, or about 225 ml/min, which is about 4% to 5% of the total cardiac output. 2 the work output of the heart under severe conditions may increase 6-fold to 9-fold. At the same time, the coronary blood flow increases 3-fold to 4-fold to supply the extra nutrients needed by the heart. 3 the efficiency of cardiac utilization of energy increases to make up for the relative deficiency of coronary blood supply. NORMAL CORONARY BLOOD FLOW AVERAGES 5% OF CARDIAC OUTPUT

6. INNERVATION 0F CORONARY BLOOD VESSELS Autonomic Nervous System Sympathetic nerves dilate coronary arteries, while parasympathetic nerves dilates them. Local Factors Metabolic byproducts, such as carbon dioxide and adenosine, dilate arteries to increase blood flow. Myocardial Oxygen Demand Increased heart rate, contractility, and wall tension enhance blood flow.

7. 1 2 Coronary arteries are end arteries. Blockage of coronary arteries Results in ischemi a and infarction of the cardiac muscle supplied by artery. 3 Significant alteration occurs in the coronary blood flow depending on the cardiac activities. Coronary blood flow can Be increased about 4 to 5 folds to meet the hearts more oxygen need during exercise. Thus, there is adequate coronary blood flow Reserve. SPECIAL FEATURES OF CORONARY CIRCULATION Heart receives its major supply during diastole as cardiac blood vessels compressed during systole. Blood flow decreases during systole. This Vaso compression maximally observed in subendocardial layer of myocardium.

8. MEASUREMENT OF CORONARY BLOOD FLOW Measured by direct method or indirect method Direct metho d: by placing an electromagnetic flow meter in the coronary artery. Indirect method : 1. fick principle 2. radionuclide methods F ick Principle : subject inhales a mixture of air and an inert gas till the gas is distributed in the tissues according to its partition coefficient. Then the arterial blood and venous samples are collected. The coronary blood flow is calculated as the ratio of the amount of the inert gas passing through the coronary arteries in unit time to the average arteriovenous gas concentration difference. Blood flow = amount of inert gas taken up per minute arteriovenous diffence of gas Radionuclide methods:

9. MEASUREMENT OF CORONARY BLOOD FLOW Radionuclide methods: Radionuclides such as thallium-201 (201Tl) are pumped into cardiac muscle cells by Na+, K+ ATPase and equilibrate with the intracellular K+ pool. The gamma camera is placed on the chest to monitor the thallium uptake by the heart.

10. Regulation of Coronary Circulation Neural regulation Sympathetic and parasympathetic stimulation Metabolic regulation Metabolic factors Adenosine mediates reactive hyperemia of ventricular muscle autoregulation Maintains coronary blood flow within the pressure range of 70-110 mmHg. Physical factors Blood flow depends on myocardial tension, the pressure build up in muscle during contraction

11. Factors Affecting Coronary Circulation Physical Activity Exercise increases oxygen demand, leading to increased coronary blood flow. Stress Stress hormones can cause vasoconstriction, potentially reducing blood flow. Diet A healthy diet low in saturated fats and cholesterol supports proper blood flow. Smoking Smoking damages blood vessels and increases the risk of coronary artery disease.

12. Coronary Artery Disease and Its Impact 1 Plaque Buildup 2 Reduced Blood Flow 3 Myocardial Ischemia Lack of oxygen to the heart muscle can cause pain, weakness, and even heart attack.

13. Coronary Artery Disease and Its Impact Angina pectoris: If hypoxia develops in the myocardium, nociceptive fibers trigger the sensation of referred pain, known as angina pectoris. When flow through a coronary artery is reduced to the point that the myocardium it supplies becomes hypoxic, angina pectoris develops. If the myocardial ischemia is severe and prolonged, irreversible changes occur in the muscle, and the result is myocardial infarction. Many individuals have angina only on exertion, and coronary blood flow is normal at rest. Others have more severe restriction of blood flow and have anginal pain at rest as well. Partially occluded coronary arteries can be constricted further by vasospasm, producing myocardial infarction. However, it is now clear that the most common cause of myocardial infarction is rupture of an atherosclerotic plaque, or hemorrhage into it, which triggers the formation of a coronary-occluding clot at the site of the plaque.

14. Coronary Artery Disease and Its Impact When myocardial cells die, they leak enzymes into the circulation, and measuring the rise in serum enzymes and isoenzymes produced by infarcted myocardial cells also plays an important role in the diagnosis of myocardial infarction. The enzymes most commonly measured are the MB isomer of creatine kinase (CK-MB), troponin T, and troponin I. Myocardial infarction is a very common cause of death in developed countries because of the widespread occurrence of atherosclerosis. In addition, there is a relation between atherosclerosis and circulating levels of lipoprotein(a) ( Lp [a]). Lp (a) has an outer coat consisting of apo(a). It interferes with fibrinolysis by down-regulating plasmin generation. It now appears that atherosclerosis has an important inflammatory component as well. The lesions of the disease contain inflammatory cells, and there is a positive correlation between increased levels of C-reactive protein and other inflammatory markers in the circulation with subsequent myocardial infarction.

15. Diagnostic Tests for Coronary Circulation Electrocardiogram (ECG) Measures electrical activity of the heart to detect abnormalities. Echocardiogram Uses sound waves to create images of the heart's structure and function. Coronary angiography Blood Tests Assess cholesterol levels, inflammation markers, and other factors related to heart health. Change in ezymes in plasma

16. Treatment and Interventions for Coronary Circulation 1 Lifestyle Changes Diet, exercise, and stress management play a crucial role. 2 Medications Aspirin, statins, and beta-blockers help manage symptoms and prevent complications. Streptokinase (lyse intracoronary clot 3 Interventional Procedures Angioplasty and stenting open blocked arteries. 4 Surgery Coronary artery bypass surgery redirects blood flow around blockages.