Cardiac Pathophysiology

Cardiac Pathophysiology

Pericarditis Often local manifestation of another disease May present as: Acute pericarditis Pericardial effusion Constrictive pericarditis

Acute Pericarditis Acute inflammation of the pericardium Cause often unknown, but commonly caused by infection, uremia, neoplasm, myocardial infarction, surgery or trauma. Membranes become inflamed and roughened, and exudate may develop

Symptoms: Sudden onset of severe chest pain that becomes worse with respiratory movements and with lying down. Generally felt in the anterior chest, but pain may radiate to the back. May be confused initially with acute myocardial infarction Also report dysphagia (difficulties swallowing), restlessness, irritability, anxiety, weakness and malaise

Signs Often present with low grade fever and sinus tachycardia Friction rub(sandpaper sound) may be heard at cardiac apex and left sternal border and is diagnostic for pericarditis (but may be intermittent) ECG changes reflect inflammatory process through PR segment depression and ST segment elevation.

Treatment Treat symptoms Look for underlying cause If pericardial effusion develops, aspirate excess fluid Acute pericarditis is usually self-limiting, but can progress to chronic constrictive pericarditis

Pericardial effusion Accumulation of fluid in the pericardial cavity May be transudate May be exudate May be blood Not clinically significant other than to indicate underlying disorder, unless: Pressure becomes sufficient to cause cardiac compression – cardiac tamponade

If development is slow, pericardium can stretch If develops quickly, even 50 -100 ml of fluid can cause problems When pressure in pericardium = diastolic pressure, get ↓ filling of right atrium, ↓ filling of ventricles, ↓ cardiac output → circulatory collapse. Outcome depends on how fast fluid accumulates.

Clinical manifestations Pulsus paradoxus – B.P. higher during expiration than inspiration by 10 mm Hg Distant or muffled heart sounds Dyspnea on exertion Dull chest pain Observable by x-ray or ultrasound

Treatment Pericardiocentesis Treat pain Surgery if cause is aneurysm or trauma

Constrictive (chronic) pericarditis Years ago, synonymous with T.B. Today, usually idiopathic, or associated with radiation exposures, rheumatoid arthritis, uremia, or coronary bypass graft

Fibrous scarring with occasional calcification of pericardium Causes parietal and visceral layers to adhere Pericardium becomes rigid, compressing the heart →↓ C.O. Stenosis of veins entering atria Always develops gradually Pathophysiology:

Symptoms and Signs Exercise intolerance Dsypnea on exertion Fatigue Anorexia

Clinical manifestations Weight loss Edema and ascites Distention of jugular vein (Kussmaul sign) Enlargement of the liver and/or spleen ECG shows inverted T wave and atrial fibrillation Can be seen on imaging

Treatment Drugs and diet Digitalis Diuretics Sodium restriction Surgery to remove restrictive pericardium

Cardiomyopathies Disorders of the heart muscle Most cases idiopathic Many due to ischemic heart disease and hypertension. Three categories: Dilated ( formerly, congestive) Hypertrophic Restrictive Heart loses effectiveness as a pump

Dilated cardiomyopathy AKA: congestive, ↓ C.O.; ↑ thrombi formation, slow blood flow ; ↓ contractility, and mitral valve incompetence, arrhythmias

Treatment: relieve symptoms of heart failure, decrease workload, and anticoagulants; transplants

Hypertrophic Cardiomyopathy Often inherited, C.O. is normal,↑ inflow resistance, and mitral valve incompetence, arrhythmais and sudden death.

Chest pain • Dizziness • Fainting, especially during exercise

major cause of death in young athletes who seem completely healthy but die during heavy exercise

The goal of treatment is to control symptoms and prevent complications

Restrictive cardiomyopathy Reduced diastolic compliance of the ventricle. C.O. is normal or↓;↑ formation of thrombi, dilation of left atrium, and mitral valve incompetence.

Disorders of the Endocardium:Valvular dysfunction Endocardial disorders damage heart valves Changes can lead to : Valvular Stenosis = too narrow Valvular Regurgitation = too leaky (or insufficiency or incompetence)

Valves that are most often affected are the mitral and aortic valves, but in I.V. drug users and in athletes that inject performance enhancing drugs, > 50 % involve only the tricuspid valve. Heart Murmur – sound caused by turbulent blood flow through damaged valves.

Both types of valve disorders: Cause increased cardiac work, and increased volumes and pressures in the chambers. This leads to chamber dilation and hypertrophy. Chamber dilation and myocardial hypertrophy are compensatory mechanisms to increase the pumping capability of the heart. Eventually, the heart fails from overwork

Aortic Stenosis Three common causes: Rheumatic heart disease -Streptococcus infection – damage by bacteria and auto-immune response Congenital malformation Degeneration resulting from calcification

Blood flow obstructed from LV into aorta during systole Causes increased work of LV → LV dilation & hypertrophy as compensation → prolonged contractions as compensation Finally heart overwhelmed → increased pressures in LA, then lungs, then right heart Aortic Stenosis

Clinical manifestations Develops gradually Decreased stroke volume Reduced systolic blood pressure Narrowed pulse pressure Heart rate often slow and pulse faint Crescendo-decrescendo heart murmur Angina, dizziness, syncope, fatigue Can lead to dysrhythmias, myocardial infarction, and left heart failure

Mitral Stenosis Most common of all valve disorders Usually the result of rheumatic fever or bacterial endocarditis During healing the orifice narrows, the valves become fibrous and fused, and chordae tendineae become shortened Get decreased flow from LA to LV during filling Results in hypertrophy of LA

By causing LA to become pump: Get increased pulmonary vascular pressures; pressures increase through LA into lung →pulmonary congestion →lung tissue changes to accommodate increased pressures →increased pressure in pulmonary artery →increased pressure in right heart →right heart failure

Clinical Manifestations Atrial enlargement can be seen on x-ray Rumbling decrescendo diastolic murmur, and accentuated first heart sound Dyspnea Tachycardia and risk of atrial fibrillation Other signs and symptoms are of pulmonary congestion and right heart failure

Aortic Regurgitation Caused by acute or chronic lesion of rheumatic fever, bacterial endocarditits, syphilis, hypertension, connective tissue disorder (e.g.Marfan syndrome) or atherosclerosis

Reflux of blood from aorta to LV during ventricular relaxation. Causes LV to pump more blood w/ each contraction → LV hypertrophy LV takes on “globular shape” →increased pressures in LA, lung, right heart

Clinical manifestations Widened pulse pressure Prominent carotid pulsations and throbbing peripheral pulses Palpitations Fatigue Dyspnea Angina High-pitched or blowing heart sound during diastole

Mitral Regurgitation Causes: mitral valve prolapse, rheumatic heart disease, infective endocarditis, connective tissue disorders, and cardiomyopathy Permits backflow of blood from the LV into the LA during ventricular systole Loud pansystolic murmur that radiates into the back and axilla

See the animated

Causes blood to flow simultaneously to aorta and back to LA. Both LV and LA pump harder to move same blood twice →LV hypertrophy and dilation as compensation Compensation works awhile, then see ↓C.O. → heart failure Also →LA hypertrophy → increased pressures through lungs → ↑ pressures in right heart →right heart failure Can see edema, shock

Clinical Manifestations Weakness and fatigue Dyspnea Palpitations

Mitral Valve Prolapse Cusps of valve billow upward into the LA during ventricular systole Mitral regurgitation can occur Most common valve disorder in U.S. Studies suggest an autosomal dominant inheritance pattern Many cases completely asymptomatic Regurgitant murmur or midsystolic click

Clinical manifestations Palpitations Tachycardia Light-headedness, syncope, fatigue, weakness Chest tightness, hyperventilation Anxiety, depression, panic attacks Atypical chest pain

Management Echocardiography for diagnosis Related to degree of regurgitation Antibiotics before invasive procedures Beta blockers to relieve syncope, severe chest pain, or palpitations Avoid hypovolemia Surgical repair

General Treatment for Valve disorders Antibiotics for Strep Anti-inflammatories for autoimmune disorder Analgesics for pain Restrict physical activity Valve replacement surgery

Heart failure Definition – When heart as a pump is insufficient to meet the metabolic requirements of tissues. Acute heart failure 65% survival rate Chronic heart failure Most common cause is ischemic heart disease

Right heart failure • Systemic symptoms • Edema, ascites • Enlarged liver, spleen • Swollen feet, ankles • Nausea • Swollen internal jugular veins

Cardiac Pathophysiology