Cardiomyopathy, Heart Failure, Shock & Pericardial Disease — USMLE Step 2 CK Notes

Cardiomyopathies

• Dilated (commonest, ~90%): systolic dysfunction with eccentric hypertrophy and four-chamber dilatation → low ejection fraction, S3, functional mitral regurgitation, balloon-shaped heart. Causes: idiopathic, alcohol, myocarditis (Coxsackie B, Chagas), peripartum, cocaine, doxorubicin, haemochromatosis, thiamine deficiency, truncated titin mutations (the commonest genetic cause). Treat as heart failure with reduced EF.
• Hypertrophic: autosomal dominant mutations in sarcomere proteins (beta-myosin heavy chain, myosin-binding protein C) → concentric, often asymmetric septal hypertrophy with myofibre disarray and diastolic dysfunction. Systolic anterior motion of the mitral valve gives outflow obstruction: a systolic murmur that gets louder with Valsalva/standing and softer with squatting/handgrip. A leading cause of sudden death in young athletes; treat with beta-blockers, avoid dehydration/diuretics/nitrates, ICD if high risk.
• Restrictive: a stiff, non-compliant ventricle with normal size and preserved EF → diastolic failure with prominent right-sided congestion. Causes: amyloidosis (low-voltage ECG with a thick wall — a classic mismatch), sarcoidosis, haemochromatosis, radiation fibrosis, endomyocardial fibrosis, and Loffler endocarditis.
• Loffler endocarditis: hypereosinophilic infiltration causing endomyocardial fibrosis with mural thrombi — a restrictive picture with eosinophilia.
• Stress (Takotsubo) cardiomyopathy: catecholamine surge after intense emotional or physical stress → transient apical ballooning ("broken heart syndrome") that mimics an MI with ST changes and modest troponin rise but normal coronary arteries; usually recovers in weeks with supportive care.

Heart failure — findings & pharmacology

• Left heart failure: pulmonary congestion → orthopnoea, paroxysmal nocturnal dyspnoea, exertional dyspnoea, bibasal crackles, pulmonary oedema and heart failure cells (haemosiderin-laden macrophages) in the alveoli.
• Right heart failure: systemic congestion → raised JVP, peripheral (pitting) oedema, congestive hepatomegaly ("nutmeg liver"), ascites and hepatojugular reflux. The commonest cause of right heart failure is left heart failure; isolated right failure from lung disease is cor pulmonale.
• HFrEF vs HFpEF: reduced EF (systolic, dilated ventricle, S3) versus preserved EF (diastolic, stiff hypertrophied ventricle, S4).
• High-output failure: the heart cannot meet an abnormally high demand despite normal contractility — severe anaemia, thyrotoxicosis, beriberi (thiamine deficiency), arteriovenous fistula, Paget disease, pregnancy.
• Pharmacology: mortality benefit in HFrEF from the four pillars — ACE inhibitor/ARB or ARNI (sacubitril-valsartan), beta-blocker, mineralocorticoid antagonist and SGLT2 inhibitor. Loop diuretics relieve congestion (symptoms, not mortality); digoxin reduces admissions; hydralazine plus nitrate helps particularly in Black patients or when ACE inhibitors are not tolerated.

Shock — haemodynamic profiles

• Hypovolaemic (haemorrhage, dehydration): CVP low, PCWP low, cardiac output low, SVR high, SvO2 low; cool, clammy skin. Treat the cause and give fluid/blood.
• Cardiogenic (MI, arrhythmia, decompensated failure): CVP high, PCWP high, cardiac output low, SVR high, SvO2 low; cool and congested. Treat with inotropes/revascularisation, careful fluids.
• Obstructive (tamponade, massive pulmonary embolism, tension pneumothorax): CVP high, cardiac output low, SVR high, SvO2 low — PCWP depends on the cause (high in tamponade, low/normal in PE). Relieve the obstruction.
• Distributive (sepsis, anaphylaxis, neurogenic): CVP low, PCWP low, cardiac output HIGH, SVR LOW, SvO2 HIGH (oxygen is not extracted); warm, flushed skin early. Treat with fluids and vasopressors (adrenaline for anaphylaxis).
• The quickest discriminator: SVR is low only in distributive shock, and SvO2 is high only in distributive shock.

Tamponade, pulsus paradoxus & syncope

• Cardiac tamponade: pericardial fluid under pressure prevents filling — Beck triad (hypotension, raised JVP, muffled sounds), absent y descent, electrical alternans and low voltage. Treat with urgent pericardiocentesis.
• Pulsus paradoxus: an inspiratory fall in systolic pressure >10 mmHg — the septum shifts left as the right heart fills, limiting left ventricular filling. Seen in tamponade, constrictive pericarditis, severe asthma and COPD.
• Syncope: transient global cerebral hypoperfusion. Vasovagal (prodrome, triggers, quick recovery) is commonest; cardiac syncope is sudden and exertional (aortic stenosis, HCM, arrhythmia, long QT) and carries the worst prognosis; orthostatic follows standing (volume depletion, drugs, autonomic failure).

Endocarditis

• Acute: Staphylococcus aureus on a normal valve — rapid, high fever, large destructive vegetations; the usual organism in intravenous drug use (tricuspid valve).
• Subacute: viridans streptococci after dental procedures on an abnormal valve — insidious, small vegetations. Streptococcus gallolyticus (bovis) should prompt colonoscopy (colon cancer); Staph epidermidis affects prosthetic valves; culture-negative causes include the HACEK organisms and Coxiella.
• Signs: new murmur, fever, Janeway lesions (painless, palms/soles, septic emboli), Osler nodes (painful, finger pads, immune complexes), splinter haemorrhages and Roth spots. Diagnose with blood cultures and echocardiography (Duke criteria).
• Non-bacterial thrombotic (marantic) endocarditis: sterile fibrin vegetations on both valve surfaces in malignancy (especially adenocarcinoma) or a hypercoagulable state; Libman-Sacks endocarditis is the sterile verrucous form seen in SLE.

Rheumatic fever & syphilitic heart disease

• Acute rheumatic fever: immune cross-reactivity (molecular mimicry) after group A streptococcal pharyngitis. JONES criteria — Joints (migratory polyarthritis), O carditis, Nodules (subcutaneous), Erythema marginatum, Sydenham chorea. Histology shows Aschoff bodies with Anitschkow cells. Chronic disease scars the mitral valve (stenosis) most often.
• Syphilitic heart disease: tertiary syphilis causes endarteritis of the vasa vasorum of the ascending aorta → medial weakening, "tree-bark" wrinkled intima, thoracic aneurysm and aortic regurgitation from root dilatation.

Pericarditis & myocarditis

• Acute pericarditis: sharp pleuritic chest pain relieved by sitting forward, a friction rub, and diffuse concave ST elevation with PR depression. Mostly viral; treat with NSAIDs plus colchicine.
• Constrictive pericarditis: a thickened, calcified pericardium restricts filling — raised JVP with a prominent (steep) y descent, pericardial knock and Kussmaul sign (JVP rises on inspiration). Causes: post-viral, post-surgical, radiation, tuberculosis. Treat with pericardiectomy.
• Myocarditis: most often Coxsackie B (also Chagas, diphtheria, drugs, autoimmune) — young patient with viral prodrome, chest pain, arrhythmia, raised troponin and possible progression to dilated cardiomyopathy or sudden death. Supportive care; avoid exercise.

Vessels, tumours & venous disease

• Hereditary haemorrhagic telangiectasia (Osler-Weber-Rendu): autosomal dominant — telangiectasias of skin and mucosa, recurrent epistaxis, GI bleeding and arteriovenous malformations (pulmonary AVMs risk paradoxical emboli and brain abscess).
• Arteriovenous malformation/fistula: a direct artery-to-vein connection with a continuous bruit/thrill; a large fistula lowers systemic resistance and can cause high-output cardiac failure.
• Cardiac myxoma: the commonest primary adult cardiac tumour — usually in the left atrium, pedunculated, causing positional dyspnoea/syncope, a "tumour plop" and embolisation. Resect surgically.
• Rhabdomyoma: the commonest primary paediatric cardiac tumour, strongly associated with tuberous sclerosis; often regresses spontaneously. Note that metastases (breast, lung, melanoma) are far more common than primary cardiac tumours overall.
• Deep vein thrombosis: Virchow triad — stasis, endothelial injury and hypercoagulability (surgery, immobility, malignancy, oestrogen, thrombophilia). Unilateral calf swelling and tenderness; diagnose with compression ultrasound and D-dimer; treat with anticoagulation. The major complication is pulmonary embolism.

High-yield revision notes; verify against a primary source before clinical use.