Transcript Document
Pathology of the Heart 4/22/09 Dr. Winokur The Heart as a Pump • Pump parts • • • • - Powersource Motor Pump with valves Control circuit - Cardiac equivalent Blood supply/oxygen Myocardium Cardiac valves Conducting system and neurohumoral control Pathologic consequences of pump failure • Blood vessels/Oxygen supply - Ischemic heart disease • Myocardium - Cardiomyopathy • Valves - Inadequate forward flow/Increased back pressure • Conducting system - Arrythmias • Neurohumoral system - Inadequate compensation for pathologic processes Failure of any of these components can result in inadequate oxygen delivery to peripheral tissues otherwise known as HEART FAILURE Case 1 • 65 yo man with past medical history significant for diabetes mellitus, hypertension, and hypercholesterolemia presents to the ED complaining of crushing substernal chest pain that radiates to the jaw. • Physical Exam • Tachycardia • Diaphoretic • EKG • Abnormal with Q-wave • Labs • Elevated troponin I and CK-MB DIAGNOSIS? • Myocardial infarct Ischemic heart disease • Mismatch between oxygen supply and demand • Typically results from atherosclerotic narrowing of the coronary arteries • Other causes include vasculitis, intramyocardial coronary arteries • Can result from unusual oxygen demand • Thyrotoxicosis • Tachycardia Presentation of ischemic heart disease • Chest pain with exertion - Angina pectoris • Myocardial infarct • Many MI s are the initial presentation • Sudden death • Cardiac failure-chronic disease Note that in women the presentation is frequently atypical ie decreased exercise tolerance rather than pain with exercise Epidemiology • Typically occurs in men in their older than 60 and in women about 10 years later • Risk factors • • • • Hyperlipidemia, especially LDL cholesterol High blood pressure Smoking Diabetes Coronary pathology of MI • Coronary arteries are partially to completely occluded by atherosclerosis • Significant changes of blood flow occur with >75% narrowing of the arteries • Plaques rupture resulting in thrombosis • Complete occlusion • Myocardial necrosis Pathology of myocardial infarction • Early changes occur in the 1st .5-1hr and are seen only at the ultrastructural level • Early intervention with thrombolytics or angioplasty can save myocardium • Over the ensuing half day irreversible necrosis occurs and can be identified by the light microscope • By 24 hours there is clear necrosis and neutrophils begin to invade the infarct • This is the first time the infarct is identifiable by gross examination. Serum enzymes in MI 24 hrs Troponin CK-MB 48 hrs 72 hrs • Over the ensuing week the infarct is overrun by neutrophils, then the dead tissue is removed by macrophages • The infarct is repaired by granulation tissue followed by fibrosis Complications of myocardial infarction • • • • • • • • Cardiac arrhythmias Cardiac failure/cardiogenic shock Extension of infarct Thromboembolism Ventricular rupture Papillary muscle rupture Ventricular aneurysm Post MI pericarditis Other presentations of ischemic heart disease • Sudden death • Frequently cause cannot be determined but there is a strong association with coronary atherosclerosis • Chronic ischemia with heart failure • Poor oxygenation results in myocardial atrophy and some myocyte loss resulting in poor cardiac performance • Revascularization can help in large vessel disease Myocarditis/Myocardial Inflammation • Can be caused by infections • Viral • Bacterial • Fungal • May be secondary to infections resulting in an autoimmune inflammation of the myocardium • Post viral • Post bacterial- Rheumatic heart disease • Autoimmune diseases-Lupus Motor failure/cardiomyopathy • The heart muscle can fail from primary or secondary causes • Primary dysfunction is related to genetic diseases • Secondary cardiomyopathies result from toxic, infectious and degenerative diseases Three types of cardiomyopathy • Cardiomyopathy is a primary disease of the heart muscle (excludes myocardial changes resulting from hypertension, valvular disease, ischemic disease and pericardial disease) • Dilated • The ventricular chamber is dilated and the myocardium is modestly thickened • Hypertrophic • The myocardium is markedly thickened especially the septum • Restrictive • The myocardium is can be of normal thickness but it is stiff and unable to relax in diastole Dilated cardiomyopathy • Causes include genetic, viral/autoimmune and toxic insults • Many cases are idiopathic and are thought to be secondary to previous viral infections • Alcohol is the most common toxic cause • Patients frequently present in heart failure with huge hearts and poor contractility • The prognosis of this condition is poor • 5 year survival is <50% • Patients die from heart failure and arrhythmias Hypertrophic cardiomyopathy • Primarily a genetic disease and may persist subclinically • Patients present with dyspnea, syncope or sometimes with sudden death • Echocardiography is the best diagnostic modality but may be detected on ECG and physical exam • Pathology- marked hypertrophy of the left ventricle with septal thickening • Septal hypertrophy causes outflow tract obstruction • These patients can frequently be successfully managed Restrictive cardiomyopathy • Fibrosis or infiltration of the myocardium causes marked stiffness and poor relaxation • Causes include fibrosis, amyloid deposition, sarcoidosis, hemochromatosis, storage diseases • Cardiac filling is impaired and patients present with diastolic heart failure • Poor prognosis unless the underlying cause can be treated Cardiac hypertrophy • There are two patterns of hypertrophy • Concentric hypertrophy • Caused by pressure overload ie hypertension, valvular stenosis • Results in marked wall thickening with a smaller chamber • Good contractility but poor relaxation • Eccentric hypertrophy • Caused by volume overload ie valve regurgitation or septal defects • Results in wall thickening with dilation of the chamber • Good contractility and acceptable relaxation Cell length New sarcomeres added lengthwise Cor Pulmonale • Right sided hypertrophy secondary to pulmonary hypertension followed by dilatation and right heart failure • Acute - 2° to pulmonary thromboembolism • Chronic - Secondary to primary pulmonary hypertension or chronic obstructive pulmonary disease (COPD) Valvular disease • All of the four valves are subject to disease • Left sided valves are more commonly affected and produce more problems • Diseases include degenerative, infectious and autoimmune Infectious endocarditis • Damage to the valve surface provides a site for bacterial adherence • Chronic valve disease • Prosthetic valves • Bacteria in the blood stream adhere to the surface and proliferate • Bacteria can be derived from oral cavity, other bacterial infections or the GI tract during procedures • Bacteria can be injected by IV drug abusers and result in right sided endocarditis • Infection can be indolent growth of bacterial colonies or highly destructive infection with valve destruction and incompetence • Strep viridans typically results in an indolent infection • Staph aureus is highly destructive • Prosthetic valves are frequently infected by coagulase negative Staph species • Aggressive and indolent bacteria can embolize and produce peripheral abcesses including the CNS Non bacterial thrombotic endocarditis (NBTE) • Small vegetations usually occuring at the valve closure lines • Associated with other diseases especially adenocarcinomas and cachexia • Usually asymptomatic and discovered incidentally • Can undergo bacterial colonization leading to infectious endocarditis Rheumatic fever • An acute, immunologically mediated, multisystem inflammatory disease that follows an untreated episode of group A streptococcal pharyngitis after an interval of a few weeks • Relatively rare in developed countries • Peak incidence is 5-15 yo. • Inflammatory infiltrates may occur in a wide range of sites including the heart Acute Rheumatic Carditis • Inflammatory changes in all three layers of the heart • Pericardium – fibrinous pericarditis; effusions • Myocardium – heart failure • Endocardium – valvular damage Rheumatic endocarditis • Repeated episodes of damage eventually damage the valve and associated apparatus • Results in valve stenosis with or without regurgitation • Mitral and aortic valves are most affected • 99% of mitral stenosis is secondary to rhd • Virtually the only cause of simultaneous mitral and aortic stenosis • Can be the substrate for infectious endocarditis Calcific aortic stenosis • Most common cause of aortic stenosis • Irregular calcium deposits behind valve cusps • Congenitally bicuspid valves • Normal valves as an age-related degenerative change Mitral valve prolapse • Most frequent valvular lesion (7%) • Young women • Stretching of posterior mitral valve leaflet • Systolic murmur with midsystolic click • Can result in mitral insufficiency • Predisposes to infective endocarditis Arrythmias • Normal cardiac automaticity requires coordination of the SA node, AV node and the intervening myocardium • Disruption of any players can result in arrythmias • Common causes of arrythmias include infarcts, alter chamber geometry (dilation and hypertrophy), viral infections affecting the pacemakers Congenital Heart Disease • Left to Right Shunts • ASD • VSD • PDA • Right to Left Shunts • Tetralogy of Fallot • Transposition of the Great Arteries • Obstruction • Coarctation of the aorta Right to Left Shunts •Cyanosis at or near birth Pericardial Diseases • Pericarditis – inflammation of pericardium • Primary – viruses • Secondary • Acute MI, cardiac surgery, uremia, acute rheumatic fever • Pericardial Effusions • Serous – heart failure • Serosanguinous – trauma, malignancy • Chylous • Hemopericardium • Cardiac tamponade Pericarditis Cardiac Tumors • Metastatic neoplasms • Lung and breast • Primary neoplasms • Myxomas • Cardiac rhabdomyomas Myxoma