Cardiovascular System PDF

1 Cardiovascular System AWAD MOHAMMED ALQAHTANI BSc of Anesthesia Technology King Khalid University, Muhayil Asir  2 The Circulatory System The circulatory system consists of the heart, blood vessels and...

1 Cardiovascular System AWAD MOHAMMED ALQAHTANI BSc of Anesthesia Technology King Khalid University, Muhayil Asir  2 The Circulatory System The circulatory system consists of the heart, blood vessels and blood. It’s function is to provide oxygen and nutrients to the tissue and to carry away the products of metabolism.  3 The Heart The heart can functionally divide into right and left pumps, Each pumps consisting of an atrium and ventricle. The right ventricle receives systemic venous (deoxygenated) blood, whereas the left ventricle receives pulmonary venous (oxygenated) blood.  4 Anatomy of the Heart  5 Valves of The Heart Pulmonic Aortic Mitral Tricuspid  6 Anatomy of the Heart Heart wall Endocardium Myocardium Epicardium Splits into another outside layer – the pericardium  7 Anatomy of the Heart  8 Anatomy of the Heart  9 The Pericardium Fixates the heart to the thoracic cavity Relatively inflexible tissue Pericardial sac holds 30-50mL of serous fluid between the pericardium and epicardium, prevents friction during contraction…  10 The Vascular System  11 The Vascular System The vascular system is composed of the systemic and pulmonary circulation. Both systems consist of arteries, capillaries and veins. Arterial system: away from the heart Venous system: capillary beds to heart Anatomical differences of arteries and veins  12 The Right Circulation of Heart Right atrium receives (deoxygenated) blood from superior and inferior vena cava. Tricuspid valve is one way value between RT. atrium and ventricle. Right ventricle pumps (deoxygenated) blood to pulmonary circulation through pulmonary artery.  13 The Left Circulation of Heart Left atrium receives (oxygenated) blood from pulmonary veins. Bicuspid (mitral) valve is one way value between LT. atrium and ventricle. Left ventricle pumps (oxygenated) blood to systemic circulation through Aorta artery.  14 Circulation through Heart Pulmonary Systemic Right side of the heart Left side of heart Blood from the body, low O2 high CO2, Oxygen rich blood - lungs- left atrium- right atriumright ventriclelungs left vent. - aorta via pulmonary trunk. Blood transported via systemic Unloading of CO2 pick up O2to left arteries to body tissues, gas and side of the heart. nutrient exchange across capillary walls Arteries carry De-Oxygenated blood Blood is then returned to the right side Veins carry oxygen rich blood of the heart through superior and inferior venae cavae.  15 Circulation through Heart Although equal volumes of blood are flowing in the pulmonary and systemic circuits, the two ventricles have uneven workloads. Pulmonary Circuit: right, short low pressure circulation. Systemic Circuit: left, long pathway, five times as much resistance to blood flow, high pressure 16  17 Coronary Circulation The functional supply of the heart, is the shortest circulation in the body. The arterial supply of coronary circulation is provided by the right and left coronary arteries arising from the base of the aorta, and encircle the heart in the atrioventricular groove.  18 Coronary Arteries The coronary arteries provide an intermittent, pulsating blood flow to the myocardium. Actively deliver blood when the heart is relaxed, ineffective when the ventricles are contracting because: – compressed by contracting myocardium – entrances to the coronary arteries is blocked by the open Aortic valve.  19 Cardiac Physiology  20 Cardiac Physiology Electrical components Electrophysiology The Cardiac Cycle Mechanical Events of the Cardiac Cycle  21 Cardiac Action Potentials At rest, the myocardial cell membrane is nominally permeable to K+, but is relatively impermeable to Na+. Intracellular Na+ concentration is kept low, whereas Intracellular K+ concentration is kept high. A membrane-bound Na+_K+ adenosine triphosphate ( ATPase ) concentrate K+ intracellularly in exchange for Na+ out of the cell. Movement of K+ out of the cell and down it’s concentration gradients results in a net of loss of positive charge inside the cell. The normal ventricular cell resting membrane potential is -80 to - 90mV, when the cell membrane potential become less negative and reach a threshold value, action potential ( depolarization ) develops. The action potential transiently raises the membrane potential of the myocardial cell to +20mV.  22 PotentialAction Early repolarisation Notch Plateau Upstroke Late rapid depolarisation Repolarisation Resting potential Intracellular Extracellular Ref: Woods et al (2005) Cardiac Nursing 5th ed Lippincott, Wilkins & Williams: Philadelphia p 23  23 Normal Values of Electrolytes Serum electrolytes :- Na+ : 135 – 145 mEq/L. K+ : 3.5 – 5.0 mEq/L. Cl- : 96 – 109 mEq/L Ca+ : 8.5 – 10.5 mg/dl  24 Electrical Conduction System Electrical cells : Generate and conduct impulses rapidly. SA and AV nodes. Bundle of His. Right and left bundle branches. Purkinje fibers. 25  26 Electrical Conduction System  27 Mechanical function of the heart  28 The Cardiac Cycle Two components Diastole Filling of the chamber Systole Contraction of the chamber and ejection of blood  29 Cardiac Output The amount of blood ejected from the ventricle in one minute Elements of cardiac output Stroke volume CO = SV x HR Amount of blood ejected from the ventricle in one contraction Heart rate The number of cardiac cycles in one minute  30 Determination of Stroke Volume Preload Amount of blood delivered to the chamber. Depends upon venous return to the heart. Also dependent upon the amount of blood delivered to the ventricle by the atrium. Contractility The efficiency and strength of contraction Frank Starling’s Law Afterload Resistance to forward blood flow by the vessel walls  31 Major Factors affecting Cardiac Stroke Volume 1. Preload. 2. Afterload. 3. Contractility. 4. Wall motion abnormalities. 5. Valvular dysfunction.  32 Autonomic Nervous System Sympathetic Nervous System Extensively innervates the SA node and ventricular cells Increase in heart rate Increase in conduction and contractility in the ventricles Parasympathetic Nervous System Innervates the SA and AV nodes Decreases heart rate Decreases conduction times through the AV node  33 Arterial Blood Pressure MAP ( Mean Arterial Pressure ) is proportionate to the product of SVR ( Systemic Vascular Resistance ) × CO ( Cardiac Output ). MAP may be estimated by the following formula: 𝑃𝑢𝑙𝑠𝑒 𝑝𝑟𝑠𝑠𝑢𝑟𝑒 MAP = Diastolic pressure + or 3 2 ×𝑑𝑖𝑎𝑠𝑡𝑜𝑙𝑖𝑐 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 +𝑆𝑦𝑠𝑡𝑜𝑙𝑖𝑐 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 MAP = 3  34 Control of Arterial Blood Pressure A. Immediate Control : Minute to minute control of blood pressure is primarily the function of autonomic nervous system. Change in blood pressure are sensed both centrally (in hypothalamus and brain stem), and peripherally by (Baroreceptor) Peripheral Baroreceptor are located at bifurcation of the common carotid arteries and aortic arch.  35 Control of Arterial Blood Pressure B. Intermediate Control : Sustained decrease in arterial pressure, together with enhanced sympathetic outflow , activate the renin-angiotensin aldosterone system, increase secretion of arginine vasopressin (AVP). Both angiotensin II and AVP are potent arteriolar vasoconstrictors.  36 Control of Arterial Blood Pressure C. Long-term Control : The effect of slower renal mechanism become apparent within hours of sustained changes in arterial pressure. The kidney's alter total body sodium and water balance to restore blood pressure to normal. Hypotension results in sodium and water retention. Hypertension increase in sodium excretion.  37 Effects of anesthetic agents  38 Effects of anesthetic agents Most volatile anesthetic agents are coronary vasodilation. Reduction of myocardial metabolic requirements. Volatile agents exert beneficial effects in experimental myocardial ischemia and infraction.  39 Pathophysiology When it all goes wrong  40 Pathophysiology – Pericardial, Myocardial and Endocardial Disease Pericarditis – inflammation of the pericardium Effusion – excess fluid/blood/pus in the pericardial sac Tamponade – significant compression of the heart due to pericardial effusion Myocarditis – inflammation of the myocardium Cardiomyopathies – dilatation, hypertrophy or non- compliance of the myocardium Infective Endocarditis – infective organisms invade the endothelial lining of the heart involving the valves, causing vegetation  41 Pathophysiology - Valvular Heart Disease Stenotic – unable to open fully  restricting forward blood flow  afterload and cause hypertrophy (enlarged muscle) Regurgitant, incompetent or insufficient – Unable to close fully  permit backward blood flow –  volume load and cause dilation of chambers Rheumatic Heart Disease – extensive inflammatory changes scarring of the valves Infective Endocarditis – Endovascular infection vegetation on a heart valve  42 Questions are welcome  43 THANK YOU  44 Reference Clinical Anesthesiology 6th edition 2018 the Author ; G.Morgan. Maged Mikhail and Michael Murray, chapter 20, pages : 343 – 374.