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Southwestern Illinois EMS System Introduction to Cardiac Anatomy and Physiology

Introduction Cardiovascular disorder Heart disease Diseases, conditions that involve heart, blood vessels Heart disease Conditions affecting heart

Introduction Coronary heart disease Coronary artery disease Coronary arteries, resulting complications Angina pectoris, acute MI Coronary artery disease Affects arteries that supply heart muscle with blood

Risk Factors & Prevention Strategies Nonmodifiable (fixed) risk factors Modifiable risk factors High blood pressure Elevated serum cholesterol levels Tobacco use Diabetes Traits, lifestyle habits that may increase chance of developing disease Nonmodifiable (fixed) risk factors Heredity Race Gender Advancing age Modifiable risk factors High blood pressure Major risk factor for heart disease, stroke, end-stage renal disease Risk of cardiovascular disease doubles for every 10-point increase in diastolic BP, every 20-point increase in systolic BP Elevated serum cholesterol levels LDL move cholesterol from liver through blood, bad cholesterol If not removed from blood, builds up in arteries, narrows arterial walls, athersclerosis HDL Move cholesterol from body tissues, organs through blood, back to liver, broken down, recycled Exercise, physical activity increases HDL concentration Tobacco use Heart attack increased 6 x in women, 3 x in men, 20 cigarettes/day Diabetes Type 2 diabetics, 2-4 x increased risk of coronary heart disease, 4 x increase in death from coronary heart disease

Risk Factors & Prevention Strategies Modifiable risk factors Physical inactivity Obesity, body fat distribution Metabolic syndrome Physical inactivity 150+ minutes moderate physical activity/60 minutes vigorous physical activity/week reduces risk of coronary heart disease by 30% Obesity and body fat distribution Waist circumference 40+ inches in men, 35+ inches in women, increased cardiovascular risk Metabolic syndrome Group of disorders including high blood pressure, elevated insulin levels, excess body weight, 1+ abnormal cholesterol levels

Risk Factors & Prevention Strategies Contributing risk factors Stress Inflammatory markers Psychosocial factors Alcohol intake Stress Persistent levels of epinephrine, increased blood pressure Inflammatory markers C-reactive protein released into bloodstream when active inflammation present Atherosclerosisis, inflammatory disease Fibrinogen necessary for normal blood clotting High blood levels increase blood thickness, platelets clumping Psychosocial factors Depression, risk of heart disease Lower socioeconomic groups  Alcohol intake 3+ drinks/day, increased death risk Light/moderate, protective effect Increases HDL levels, protect against coronary heart disease through anti-inflammatory mechanism, reduce fibrinogen, hinder platelet clumping

Cardiovascular Anatomy & Physiology

Anatomy Review Blood vessels Arteries Arterioles Capillaries Venules Veins Arteries Carry blood from heart to arterioles Under high pressure Arterioles Smallest branches of arteries  Connect arteries, capillaries Capillaries Smallest, most numerous Connect arterioles, venules Function as exchange vessels Venules Smallest branches of veins Connect capillaries, veins Veins Carry deoxygenated blood to heart Walls of veins thinner than arteries Valves in larger veins of extremities, neck allow blood flow in one direction to heart

Anatomy Review Heart anatomy Location Mediastinum Behind sternum, above diaphragm Base Apex Mediastinum Space between lungs in middle of chest Sits behind sternum, just above diaphragm 2/3 lies to left of midline of sternum 1/3 lies to right of sternum Base Upper portion Approximately level of 2nd rib Apex Lower portion Formed by tip of left ventricle Just above diaphragm between 5th & 6th ribs in midclavicular line Tilted slightly toward left in chest Anterior surface composed mostly of right ventricle Inferior surface formed by right, left ventricles

Anatomy Review Heart Location Heart lies in middle of thoracic cavity behind sternum, between lungs

Anatomy Review Heart anatomy Heart chambers Upper chambers Right, left atria Lower chambers Right, left ventricles Right, left atria  Right atrium receives blood low in oxygen From superior & inferior vena cava, coronary sinus Coronary sinus, largest vein, drains heart Left atrium receives oxygenated blood from lungs From right, left pulmonary veins When atria contract, blood pumped through valve into ventricles Right, left ventricles Walls thicker than atria Right ventricle pumps blood to lungs Left ventricle pumps blood to body Apical impulse/point of maximal impulse, felt at apex

Anatomy Review Heart anatomy Septum Pulmonary circulation Systemic circulation Blood carried from heart to body through arteries, arterioles, capillaries Blood returned to heart through venules, veins Septum Interatrial septum separates right, left atria Interventricular septum separates right, left ventricles  Separates heart into functional pumps Right atrium, ventricle Left atrium, ventricle Pulmonary circulation Right side of heart. low-pressure system, pumps unoxygenated blood through lungs to left side Systemic circulation  Left side, high-pressure pump, receives oxygenated blood, pumps to rest of body

Anatomy Review Heart anatomy Heart layers Endocardium Myocardium Epicardium Pericardium Endocardium Innermost, thin smooth layer of epithelium, connective tissue Lines heart’s inner chambers, valves, chordae tendineae, papillary muscles Continuous with innermost layer of arteries, veins, capillaries, creates continuous, closed circulatory system  Myocardium Middle, thick, muscular layer Cardiac muscle fibers, pumping action Epicardium is the outermost layer Contains blood capillaries, lymph capillaries, nerve fibers, fat Main coronary arteries lie on epicardial surface Feed this area first Enters myocardium, supplies inner layers with oxygenated blood Continuous with inner lining of pericardium at apex  Pericardium Protects from trauma, infection Fibrous parietal pericardium Outer layer Anchors heart to sternum, diaphragm Helps prevent excessive movement in chest Serous pericardium Inner layer Parietal layer lines inside of fibrous pericardium Visceral layer adheres to outside of heart, forms the outer layer of heart muscle

Anatomy Review Heart anatomy Heart valves AV valves Separate atria from ventricles Tricuspid valve, between right atrium, right ventricle Mitral/bicuspid valve lies between left atrium, left ventricle Open when forward pressure forces blood forward Close when backward pressure pushes blood backward Tricuspid valve, between right atrium, right ventricle 3 separate cusps/flaps Mitral/bicuspid valve lies between left atrium, left ventricle 2 cusps

Anatomy Review Heart anatomy Atrial kick Blood flows continuously into atria 70% flows directly through, into ventricles before atria contract When atria contract, additional 30% added to filling of ventricles When ventricles contract (systole), pressure rises Tricuspid, mitral valves close when pressure within ventricles exceeds that of atria

Anatomy Review Heart anatomy Semilunar (SL) valves Pulmonic, aortic valves Prevent backflow of blood from aorta, pulmonary arteries into ventricles Close as ventricular contraction ends, pressure in pulmonary artery, aorta exceeds that of ventricles Chordae tendinae, connective tissue, attached to AV valves underside & papillary muscles Prevent backflow of blood from aorta, pulmonary arteries into ventricles When right ventricle contracts blood flows through pulmonic valve into right, left pulmonary arteries When left ventricle contracts blood flows through aortic valve into aorta Chordae tendinae, connective tissue, attached to AV valves underside & papillary muscles Papillary muscles relax, contract with ventricles Adjust tension on chordae tendinae, preventing bulging too far into atria

Anatomy Review Blood flow through heart Enters right atrium via superior, inferior venae cavae, coronary sinus Right atrium through tricuspid valve into right ventricle Right ventricle expels blood through pulmonic valve into pulmonary trunk Flows through pulmonary arteries to lungs Enters right atrium via superior, inferior venae cavae, coronary sinus Low in oxygen, high in carbon dioxide Right atrium through tricuspid valve into right ventricle When ventricle contracts, tricuspid valve closes Right ventricle expels blood through pulmonic valve into pulmonary trunk Divides into right, left pulmonary artery, each carries blood to one lung

Anatomy Review Blood flow through heart Low in O2, passes through pulmonary capillaries From left atrium through mitral valve into left ventricle Distributed throughout body through aorta, its branches Low in O2, passes through pulmonary capillaries Direct contact with alveolar-capillary membrane, oxygen & carbon dioxide exchanged, then to pulmonary veins Carbon dioxide exhaled as left atrium receives oxygenated blood from lungs From left atrium through mitral valve into left ventricle Left ventricle contracts, mitral valve closes Leaves through aortic valve into aorta

Anatomy Review Blood flow through heart Tissues of head, neck, upper extremities via superior vena cava Lower body via inferior vena cava Superior, inferior vena cava carry contents into right atrium Superior, inferior vena cava carry contents into right atrium Blood flows from the right atrium through the tricuspid valve into the right ventricle

Anatomy Review Cardiac cycle Repetitive pumping process, events associated with blood flow through heart Systole Diastole Systole Chamber contracts blood, being ejected Atria, ventricles have systolic phase Diastole Relaxation period, chambers allowed to fill Atria, ventricles have diastolic phase Myocardium receives fresh oxygenated blood from coronary arteries during ventricular diastole

Anatomy Review Cardiac cycle Depends on cardiac muscle ability to contract, condition of heart’s conduction system Pressure with each chamber rises in systole, falls in diastole Conduction system provides timing of events between atrial, ventricular systole

Anatomy Review Coronary arteries Right, left Main arteries Left anterior descending (LAD), left circumflex (LCX), right coronary artery (RCA) Lie on outer surface of heart Right, left 1st branches off proximal aorta Openings just beyond cusps of aortic SL valve When contract, flow to heart tissues reduced, vesicles compressed Fill when ventricles relaxed Lie on outer surface of heart Penetrate heart’s muscle, supply endocardium, myocardium with blood

Anatomy Review Coronary Arteries 3 major coronary arteries are left anterior descending (LAD; also called anterior intraventricular artery), left circumflex (LCX), right coronary artery (RCA)

Anatomy Review Coronary veins Travel alongside arteries Coronary sinus, largest vein, drains heart Lies in groove that separates atria from ventricles Drains into right atrium

Anatomy Review Heart rate Affected by sympathetic, parasympathetic ANS Chronotropic effect Inotropic effect Dromotropic effect Affected by sympathetic, parasympathetic of ANS Sympathetic division prepares body to function under stress, “fight-or-flight” Parasympathetic division conserves, restores body resources, “feed-and-breed” Chronotropic effect Change in heart rate Positive effect, increase Negative effect, decrease Inotropic effect Change in myocardial contractility Dromotropic effect Speed of conduction through AV junction Positive effect, increase in velocity Negative effect, decrease in velocity

Anatomy Review Heart rate Baroreceptors Specialized nerve tissue (sensors) Found in internal carotid arteries, aortic arch Detect changes in blood pressure When stimulated cause sympathetic/parasympathetic response  Will “reset” to new “normal” after few days of exposure to specific pressure Sympathetic, adrenergic response Parasympathetic, cholinergic response

Anatomy Review Heart rate Chemoreceptors In internal carotid arteries, aortic arch, medulla detect changes in concentration of hydrogen ions (pH), O2, carbon dioxide in blood

Anatomy Review Heart rate Parasympathetic stimulation Parasympathetic fibers supply sinoatrial node, atrial muscle, & AV junction of heart by vagus nerves Slows sinoatrial node discharge rate Slows conduction through AV node Decreases atrial contraction rate Can cause small decrease in ventricular contraction force Acetylcholine (neurotransmitter) released when parasympathetic nerves stimulated Binds to parasympathetic receptors

Anatomy Review Heart rate Sympathetic stimulation Sympathetic nerves supply specific areas of heart’s electrical system, atrial muscle, ventricular myocardium When stimulated, norepinephrine released Increases in heart rate shorten all phases of cardiac cycle When stimulated, norepinephrine released Increases contraction force Increases heart rate Increases blood pressure

Anatomy Review Heart rate Increases in heart rate shorten all phases of cardiac cycle Electrolyte, hormone levels, medications, stress, anxiety, fear, body temperature can influence heart rate Heart rate increases when body temperature increases, decreases when body temperature decreases If ventricles do not have time to fill Amount of blood sent to coronary arteries reduced Amount of blood pumped out of ventricles decreases Signs of myocardial ischemia may be seen

Heart as Pump Venous return Most important factor determining amount of blood pumped out by heart is amount of blood flowing into right heart

Heart as Pump Cardiac output Amount of blood pumped into the aorta each minute by heart Defined as stroke volume x heart rate Stroke volume determined by Preload Afterload Preload Force exerted on walls of ventricles at end of diastole More blood returning to right atrium increases preload Less blood decreases preload Afterload Pressure/resistance against which ventricles must pump to eject blood Influences Arterial BP Ability of arteries to become stretched Arterial resistance Lower resistance, more easily blood ejects Increased afterload increases heart’s workload Increased blood thickness High BP

Heart as Pump Cardiac output Frank–Starling’s law Greater the volume of blood in heart during diastole (preload), the more forceful cardiac contraction & more blood ventricle will pump (stroke volume) Important that heart adjust its pumping capacity in response to changes in venous return During exercise, heart muscle fibers stretch in response to increased volume (preload) before contracting Stretching of muscle fibers allows heart to eject additional volume with increased force increasing stroke volume & cardiac output

Heart as Pump Cardiac output Frank–Starling’s law Factors that increase cardiac output include increased body metabolism, exercise, age & size of body Factors that may decrease cardiac output include shock, hypovolemia, heart failure Heart failure may result from any condition that impairs preload, afterload, cardiac contractility, or heart rate As heart begins to fail, body’s compensatory mechanisms attempt to improve cardiac output by manipulating 1+ of these factors

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