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Cardiomyopathy

Basics

  • Myocardial diseases causing structural and functional heart abnormalities without coronary artery disease, congenital defects, valvular disease, or hypertension sufficient to explain dysfunction.
  • Cause 5-10% of heart failure cases.

Classification

  • Primary (mainly cardiac):
  • Genetic: Hypertrophic cardiomyopathy (HCM), Arrhythmogenic RV cardiomyopathy/dysplasia (ARVC/D), LV noncompaction (LVNC), glycogen storage diseases, conduction defects, mitochondrial myopathies, ion channel disorders (LQTS, Brugada, CPVT).
  • Mixed: Dilated cardiomyopathy (DCM), restrictive cardiomyopathy (RCM).
  • Acquired: myocarditis, stress cardiomyopathy, peripartum, tachycardia-induced, infants of diabetic mothers.
  • Secondary: ischemic, valvular, hypertensive, congenital heart disease.

Epidemiology

  • DCM incidence: 5-8 per 100,000 annually; prevalence ~1:2500; most common heart transplant indication.
  • HCM prevalence: ~1:500 adults; 50% familial.

Etiology and Pathophysiology

  • HCM: LV hypertrophy (>15 mm), nondilated, disproportionate to hemodynamic stress.
  • ARVC/D: RV progressive myocyte loss with fatty/fibrofatty replacement, possible myocarditis association.
  • LVNC: Congenital "spongy" LV myocardium.
  • LQTS: Ion channelopathy with prolonged ventricular repolarization.
  • DCM: Ventricular dilation, systolic dysfunction, often genetic, infectious, toxic causes.
  • RCM: Normal/reduced ventricular volume with restrictive filling and biatrial enlargement.
  • Myocarditis: Inflammation from toxins, drugs, infections.
  • PPCM: DCM variant with LV systolic dysfunction and heart failure of unknown etiology.
  • Stress cardiomyopathy: Acute reversible LV dysfunction after psychological stress.
  • Endocrine, nutritional, autoimmune, infectious, infiltrative, storage, neuromuscular, toxic, and idiopathic causes also contribute.

Risk Factors

  • Same as etiology (genetic predisposition, toxins, infections, systemic diseases).

Diagnosis

History

  • Dyspnea, orthopnea, PND, chest pain, edema, abdominal bloating/pain.

Physical Exam

  • Tachypnea, Cheyne-Stokes respiration, low pulse pressure, cool extremities, JVD, bibasilar rales, tachycardia, displaced PMI, S3 gallop, systolic murmur, hepatosplenomegaly, ascites, peripheral edema.

Differential Diagnosis

  • Severe pulmonary disease, primary pulmonary hypertension, recurrent PE, constrictive pericarditis, advanced malignancy, anemia.

Diagnostic Tests

  • ECG: LV hypertrophy, conduction delay, atrial fibrillation, old infarcts.
  • Chest X-ray: cardiomegaly, increased upper lobe vasculature, pleural effusions.
  • Echocardiogram:
  • DCM: four-chamber enlargement, global hypokinesis, mural thrombi.
  • HCM: severe LV hypertrophy, systolic anterior motion of mitral valve, mitral regurgitation, dynamic obstruction.
  • RCM: low voltage ECG, pseudoinfarction pattern.
  • Cardiac MRI: characterizes myocarditis, infiltrative diseases; patchy delayed enhancement in HCM.
  • Stress myocardial perfusion imaging: rule out ischemia.
  • Cardiac catheterization: exclude ischemic heart disease.
  • Genetic testing and counseling.

Treatment

Medications

  • Treat heart failure per guidelines.
  • Avoid preload reduction (diuretics) and digoxin in obstructive HCM as they may worsen obstruction.
  • Negative ionotropes/chronotropes: Ξ²-blockers, calcium channel blockers.
  • ICD for prevention of VT/VF/sudden cardiac death; especially with family history of SCD.
  • Anticoagulation and rate control for atrial fibrillation.
  • Immunosuppression for myocarditis-related DCM.
  • Tafamidis for transthyretin amyloid-related RCM.

Referral

  • Heart failure team management.
  • Early transplant evaluation if refractory.

Ongoing Care

  • Dietary salt and fluid restriction, low-fat diet.
  • Regular follow-up for symptoms and management adherence.

Prognosis

  • NYHA Class IV: 20-40% mortality within 1 year without transplant.
  • With transplant: 1-year survival up to 94%.

Complications

  • Progressive heart failure, syncope, renal failure, arrhythmias, sudden cardiac death.

Clinical Pearls

  • Cardiomyopathy is often the end stage of diverse cardiac diseases.
  • Familial HCM involves sarcomeric protein mutations, autosomal dominant.
  • Core heart failure therapy includes ACE inhibitors, Ξ²-blockers, diuretics, digoxin, device therapy.

References

  1. Seward JB, Casaclang-Verzosa G. Infiltrative cardiovascular diseases: cardiomyopathies that look alike. J Am Coll Cardiol. 2010;55(17):1769-1779.
  2. Elliott PM, Anastasakis A, Borger MA, et al; ESC Task Force on HCM. 2014 ESC guidelines for diagnosis and management of hypertrophic cardiomyopathy. Eur Heart J. 2014;35(39):2733-2779.
  3. Japp AG, Gulati A, Cook SA, et al. The diagnosis and evaluation of dilated cardiomyopathy. J Am Coll Cardiol. 2016;67(25):2996-3010.