diseases of the heart课件

Diseases of the Heart Major Determinants of Disease Most heart disease is the result of atherosclerotic obstruction of the coronary arteries Congestive heart failure is mechanical failure of the heart to eject blood delivered to it Metabolic or autoimmune disease may cause heart muscle or valve damage High blood pressure accelerates atherosclerosis & most other cardiac disease Cardiac valves are one-way gates for blood flow & are susceptible to obstruction & regurgitation Cardiac valves are susceptible to infection Abnormal embryonic development of the heart produces significant cardiac anatomic malformations Abnormal heartbeat patterns (arrhythmias) can cause cardiac dysfunction or death & can complicate any heart condition Arrhythmias Mechanically inefficient CO decreases Potentially fatal Caused by myocardial ischemia MI electrolyte imbalance stress caffeine drugs, especially stimulants congenital defects in the electrical network Normal rhythm is 70 beats/min bradycardia is 100 beats/min Premature atrial contractions extra atrial beats common in healthy people not harmful due to stress lack of sleep caffeine some drugs Atrial flutter rapid, regular atrial rhythm 300 beats/min Atrial fibrillation rapid, irregular atrial rhythm AV node filters out alot decreased CO Each year heart disease accounts for about 1/3 of deaths in the US, most of which are associated with coronary artery atherosclerosis. If cerebrovascular disease, vascular complications of diabetes, & other vascular diseases are included, the figure is over 40%. After age 40 the lifetime risk for developing symptomatic coronary artery disease is 50% in men & 40% in women. Heart Block Atrial signal is delayed & cannot cross into the ventricle Common cause is anatomic abnormalities Can also be caused by digitalis 1st degree delay of signal but no missed ventricular beats 2nd degree delay long enough to cause missed ventricular beats 3rd degree total block of atrial signal decreased CO Premature ventricular contractions occur in healthy people chest palpitations & anxiety Ventricular tachycardia spontaneous, regular beating at 120 beats/min decreased CO Ventricular fibrillation extremely rapid & irregular negligible CO Congestive Heart Failure CHF Heart unable to eject volume of blood delivered to it Endpoint for coronary atherosclerosis HTN valve disease cardiomyopathy congenital cardiac malformation Affects about 1% of Americans die within 5 years Most common cause is cardiac muscle damage usually due to CAD Less commonly due to valve defects Heart tries to compensate for either of these by increasing HR & force of contraction & through cardiac muscle hypertrophy In L ventricular failure, low CO causes systemic hypoperfusion & pulmonary venous congestion In R ventricular failure, low CO causes systemic venous congestion The most common cause of R heart failure is L heart failure The low CO of L heart failure reduces renal blood flow which stimulates the renin -angiotensin-aldosterone system R & L ventricles can fail independently but usually fail together 2 components to uncompensated failure forward failure low ventricular output backward failure venous congestion L Heart Failure L ventricle dilates Forward component decreased blood flow to organs Backward component blood backs up into L atrium & lungs pulmonary edema dyspnea R Heart Failure R ventricle dilates Forward component decreased blood flow to lungs Backward component systemic venous congestion congestion of liver, spleen edema in feet & legs ascites Usually not by itself but found in combination with pulmonary HTN known as cor pulmonale Etiology L heart failure damaged cardiac muscle HTN valve disease cardiomyopathy R heart failure L heart failure pulmonary HTN lung disease valve disease congenital heart disease involving L to R shunt Coronary Artery Disease CAD Almost all from atherosclerotic narrowing or complete obstruction Depending on the degree & character of the obstruction angina pectoris MI sudden cardiac death chronic ischemic heart disease with CHF Epidemiology Begins in the crib Risk factors age high LDL low HDL HTN smoking fatty diet sedentary lifestyle diabetes familial history Average patient overweight diet high in saturated fat big belly little exercise high cholesterol has diabetes or HTN Causes of Coronary Ischemia Partial obstruction usually stable plaques coronary vasospasm Complete obstruction usually an unstable plaque Angina Pectoris Distinctive sensation caused by myocardial ischemia Described as smothering pressing aching heaviness May radiate to jaw shoulder arms upper abdomen May have dyspnea & sweating Stable angina rises & falls smoothly over a few minutes rest & medication helps usually precipitated by exertion or emotion Unstable angina caused by platelets aggregating on a plaque may herald an impending MI new onset, intensification, nocturnal, prolonged need intervention Unremitting angina does not fluctuate no relief due to MI Myocardial Infarction MI Area of necrosis caused by ischemia Most common cause of death in industrialized nations Most initiated by plaque disruption & accompanying thrombosis Size of infarct determined by vessel involved Age of infarct determined by gross & microscopic findings coagulative necrosis early development of granulation tissue mature scar Nearly of all infarcts involve anterior descending About 1/3 involve the R coronary artery The rest involve the circumflex artery Deepest muscle is last supplied & 1st to die subendocardial infarct In 3-6 hours, can enlarge to involve the full thickness of the ventricular wall transmural infarct Anatomic complications Infarct papillary muscles Release of substances from necrotic muscle that attracts platelets & WBCs to form mural thrombus Chronic Myocardial Ischemia Elderly Usually have CHF Ventricles dilated, thin-walled, & flabby May lead to heart failure Sudden Cardiac Death Death within 1 hour of onset of symptoms About of all cardiac deaths Most common cause of instantaneous death in industrialized society Most due to electrical malfunction asystole ventricular fibrillation Hypertensive Heart Disease L ventricular hypertrophy Stiff myocardium susceptible to infarction reduced compliance & stroke volume increases diffusion distance Predisposed to atherosclerosis End result is often CHF, MI, or arrhythmias Valvular Heart Disease Causes Inflammation & infection Syphilitic aortitis Myxomatous degeneration of the mitral valve Ruptured mitral valve chordae tendineae Massive L ventricular dilation Rheumatic Heart Disease Calcific Aortic Stenosis Age-related degenerative changes Fibrosis, calcification, deformity Have systolic murmur L ventricular hypertrophy angina syncope Mitral Valve Prolapse Most common valve disease “floppy” valve Cause unknown Late systolic murmur & mid-systolic click Most patients asymptomatic Noninfective Thrombotic Endocarditis Vegetations of platelets & fibrinous material No microbes in lesions but susceptible to microbial colonization Linked to cachexia DVT hypercoagulable blood malignancies May embolize Infective Endocarditis Almost always caused by bacterial infection L-sided valves most commonly affected Vegetations containing microbes May embolize Greatest hazard is erosion & perforation of the valve Usually affects previously disease valves Staphylococcus more dangerous than Streptococcus or Enterococcus Myocarditis Usually due to virus coxsackie A or B Most resolve without therapy but a few cases proceed to CHF Cardiomyopathies Primary Intrinsic disease of cardiac muscle Cause usually unknown Secondary Associated with ischemic heart disease HTN infections valvular disease congenital abnormalities Dilated Cardiomyopathy Hypertrophy, dilation, & low ejection fraction Cause usually unknown Heart is flabby & weak All chambers dilated Hypertrophic Cardiomyopathy About the cases are genetic Sudden death in children