Cardiac Pathology Overview

Overview

Lecture wraps up cardiac pathology topics: valvular diseases, congenital shunts, cardiomyopathy and myocarditis, pericardial diseases, cardiac tumors, and heart failure. Emphasis on mechanisms: pressure vs volume overload, compensatory hypertrophy, and progression to decompensation.

Core Hemodynamics and Rules

• Ventricular overload types: pressure overload (stenosis, hypertension) and volume overload (regurgitation, shunts).
• Compensation: hypertrophy first; later decompensation with chamber dilation, congestion, and failure.
• Left-sided problems usually precede and cause right-sided failure; the reverse is not automatic.
• Major etiologies across topics: rheumatic heart disease and infective endocarditis.

Valve Diseases: Mitral Stenosis (MS)

• Main causes: chronic rheumatic disease; less commonly endocarditis.
• Pathophysiology: LA pressure elevated → LA dilation, stasis → atrial fibrillation, thrombus, systemic emboli; pulmonary congestion → pulmonary hypertension → RV hypertrophy/failure.
• LV filling reduced; LV typically underloaded early.
• Complications: AF, mural thrombi in dilated LA, pulmonary hypertension, right-sided failure.

Valve Diseases: Mitral Regurgitation (MR)

• Causes: rheumatic disease, infective endocarditis; myxomatous degeneration (mitral valve prolapse); annular dilation; papillary muscle dysfunction/rupture.
• MVP: myxomatous (myxoid) degeneration → floppy leaflets prolapse into LA during systole.
• Annular dilation (LV dilation) prevents leaflet coaptation, causing MR.
• Hemodynamics: systolic backflow to LA → LA and LV volume overload → dilation and eccentric hypertrophy; progressive pulmonary congestion; AF risk.

Valve Diseases: Aortic Stenosis (AS)

• Causes: calcific degeneration of tricuspid valve (elderly); congenital bicuspid valve (earlier); rheumatic disease (less common).
• Pathophysiology: LV pressure overload → concentric hypertrophy → increased O2 demand and myocardial ischemia (demand ischemia ± coexisting CAD).
• Findings: reduced cardiac output; angina, syncope on exertion, heart failure; possible coexistent coronary atherosclerosis at older age.

Valve Diseases: Aortic Regurgitation (AR)

• Causes: annular/root dilation (e.g., aortic root disease, cystic medial degeneration, Marfan); rheumatic disease; endocarditis.
• Pathophysiology: diastolic backflow from aorta to LV → LV volume overload, massive dilation and eccentric hypertrophy; secondary LA and pulmonary congestion; right-sided failure later.
• Notable: very large “globular” heart in chronic AR due to marked LV dilation.

Right-Sided Valvular Notes

• Pulmonic and tricuspid disease: similar mechanisms; less common as primary lesions.
• Carcinoid heart disease: serotonin-induced right-sided valvular fibrosis and stenosis; left side spared due to serotonin inactivation in lungs.

Congenital Heart Disease and Shunts

• Etiology: mostly sporadic mutations; chromosomal anomalies (e.g., Down syndrome); maternal factors (rubella, diabetes, teratogens, radiation); folate deficiency risk.
• Shunt directions:
  • Left-to-right (acyanotic initially): ASD, VSD, PDA; cause pulmonary overcirculation and hypertension.
  • Pulmonary hypertension progression: reversible early; prolonged leads to vascular remodeling and irreversible (Eisenmenger), with shunt reversal to right-to-left and cyanosis.
• Ventricular septal defect (VSD):
  • Small defects may be asymptomatic, close spontaneously or present later with murmur.
  • Large defects: L→R shunt → RV volume overload → pulmonary HTN → Eisenmenger with cyanosis, clubbing, secondary polycythemia.
  • Murmurs at septal site and pulmonic area; confirm by echocardiography; close surgically or percutaneously when indicated.
• Tetralogy of Fallot (outline): pulmonic stenosis, VSD, overriding aorta, RV hypertrophy; R→L shunt with cyanosis.
• Paradoxical emboli: with R→L shunts, venous thrombi can embolize systemically.

Myocarditis

• Causes:
  • Immune: acute rheumatic fever (Aschoff bodies, Anitschkow cells).
  • Infectious: viral (Coxsackie most noted), diphtheritic toxin, parasitic (e.g., Trypanosoma—Chagas).
  • Toxic: radiation, drugs (e.g., doxorubicin).
• Clinical spectrum: often subclinical; can cause chest discomfort, arrhythmias, heart failure; rare fulminant cases.
• Diagnosis: exclude ischemia; MRI supportive; endomyocardial biopsy in selected cases.

Cardiomyopathies

• Definition: primary myocardial disorders not explained by ischemia, hypertension, valvular, or congenital disease; often genetic mutations.
• Types:
  • Dilated cardiomyopathy (most common): ventricular dilation, systolic dysfunction (reduced contractility), secondary volume overload; causes include genetic, post-myocarditis, toxins (alcohol, chemo), peripartum.
  • Hypertrophic cardiomyopathy: marked myocardial hypertrophy with impaired relaxation (diastolic dysfunction); often genetic; outflow tract obstruction may occur; ischemia due to high demand.
  • Restrictive cardiomyopathy: impaired ventricular filling due to stiff myocardium; causes include amyloidosis (primary AL or secondary AA), sarcoidosis (granulomas with fibrosis), scleroderma (excess collagen).

Pericardial Diseases

• Types:
  • Fibrinous pericarditis: rough “bread and butter” surface; causes include rheumatic fever, uremia, transmural MI; outcomes: resolution or organization/adhesions.
  • Purulent (suppurative) pericarditis: bacterial seeding; often via contiguous spread; poor resolution, organization common.
  • Tuberculous pericarditis: granulomatous; frequent fibrosis, calcification; high risk of constriction.
  • Hemorrhagic pericarditis: blood in pericardial sac due to trauma, surgery, tumor invasion, aortic dissection, or acute MI rupture; risk of tamponade.
  • Constrictive pericarditis: dense fibrous/calcific thickening constricting heart; severe diastolic filling impairment; small external cardiac silhouette; differentiate from restrictive cardiomyopathy (constrictive is extracardiac constraint).
  • Adhesive mediastinopericarditis: fibrous adhesions to surrounding structures; impairs both systolic and diastolic function, increases workload.

Cardiac Tumors

• Primary:
  • Myxoma (most common): usually left atrium; gelatinous mass with myxoid stroma; may obstruct valve or embolize; surgically resectable.
  • Rhabdomyoma/rhabdomyosarcoma referenced as naming analogs; malignancies rare.
• Secondary (metastases):
  • Direct or lymphatic spread from lung/breast carcinomas; hematogenous metastases (e.g., melanoma); pericardial involvement common.

Heart Failure: Concepts and Clinical Features

• Definition: cardiac output inadequate for tissue needs; acute or chronic; left-, right-, or biventricular.
• Left-sided heart failure:
  • Common causes: chronic ischemic heart disease, systemic hypertension, valvular (AS, AR, MR), cardiomyopathy.
  • Pulmonary congestion/edema: dyspnea, orthopnea, paroxysmal nocturnal dyspnea; basal crackles.
  • Low output: fatigue, renal hypoperfusion → RAAS activation → salt/water retention (worsens congestion).
• Right-sided heart failure:
  • Commonly secondary to left failure (pulmonary hypertension); primary causes include lung disease (cor pulmonale), pulmonic/tricuspid valve disease.
  • Systemic venous congestion: elevated JVP, hepatomegaly/congestive hepatopathy, peripheral edema, ascites; renal and GI congestion (nocturia, anorexia, nausea).
• Compensatory mechanisms: hypertrophy, neurohormonal activation (RAAS, sympathetic), initially helpful then harmful with fluid retention and increased afterload.

Valvular Lesions: Structured Summary

Congenital Shunts: Structured Summary

Restrictive/Constrictive Differentiation

• Restrictive cardiomyopathy: myocardial stiffness (amyloid, sarcoid, scleroderma); normal pericardium; diastolic dysfunction.
• Constrictive pericarditis: pericardial fibrosis/calcification; external constraint; prominent diastolic limitation; small heart size; pericardiectomy is definitive.

Key Terms & Definitions

• Pressure overload: increased resistance to ejection (stenosis, HTN) → concentric hypertrophy.
• Volume overload: increased filling volume (regurgitation, shunts) → eccentric hypertrophy/dilation.
• Myxomatous degeneration: myxoid changes in valve tissue causing leaflet floppiness (MVP).
• Eisenmenger syndrome: irreversible pulmonary vascular disease with reversal of L→R shunt to R→L and cyanosis.
• Carcinoid heart disease: serotonin-mediated right-sided valvular fibrosis/stenosis.
• Fibrinous pericarditis: “bread and butter” appearance from fibrin deposition.
• Cardiac tamponade: hemodynamic compromise from rapid pericardial fluid/blood accumulation.

Action Items / Next Steps

• Correlate valvular lesion with overload type and expected chamber remodeling.
• For shunts, assess size and pulmonary pressures; intervene before irreversible pulmonary vascular disease.
• In suspected myocarditis, exclude ischemia; consider MRI and selective biopsy.
• Distinguish restrictive cardiomyopathy from constrictive pericarditis clinically and by imaging; manage accordingly.
• In heart failure, identify precipitating lesion (valve, cardiomyopathy, ischemia) and target congestion and neurohormonal activation.