Cardiomyopathies

 

• Definition

  • Abnormal structure or function of the myocardium.
  • Newer definitions require it to be unexplained by ischaemic, hypertensive, or valvular disease, with the term limited to myocardial diseases with known genetic, morphological, and/or functional characteristics.
  • It often leads to heart failure, and in rarer cases, sudden cardiac death.

• Dilated cardiomyopathy (DCM)

  Pathophysiology and epidemiology

  Commonest cardiomyopathy. Exact prevalence unclear but probably more than 1/500. Can present at any age.

  Features:

  • Dilated chambers.
  • Systolic dysfunction.
  • ↓Cardiac output.

  Causes:

  • Idiopathic
  • Familial, 2/3 of which are autosomal dominant.
  • Cardiovascular: ischaemia, HTN, valve disease. See 'Definition' above about why this isn't strictly speaking 'cardiomyopathy'.
  • Myocarditis: viral, Chagas disease.
  • Alcohol
  • Pregnancy: Peripartum cardiomyopathy.
  • Stress: Takotsubo cardiomyopathy.
  • Tachycardia: 'tachymyopathy', usually in chronic SVT such as atrial flutter or AF.
  • Multi-system disease: thyrotoxicosis, sarcoidosis, haemochromatosis.

  Signs and symptoms

  Symptoms:

  • Fatigue
  • SOB
  • Complications and associated cardiac diseases: LVF ± RVF, emboli, AF, VT.

  Signs:

  • ↑HR, ↓BP.
  • S3 heart sound, mitral/tricuspid regurgitation.
  • Hyperdynamic apex.
  • ↑JVP

  Investigations

  Bloods:

  • ↑BNP

  Imaging:

  • CXR: cardiomegaly, pulmonary oedema.
  • Echo: dilated LV, ↓ejection fraction, mitral/tricuspid regurgitation, LV mural thrombus.
  • ECG: ↑HR, ST or T changes, LBBB.

  Management

  As for heart failure (HF).

  Complications

  • Common cause of HF.
  • Sudden cardiac death due to ventricular arrhythmia (rare).
  • 5 yr mortality 50%.

• Hypertrophic cardiomyopathy (HCM)

  Pathophysiology and epidemiology

  • Most commonly due to a mutation in a sarcomere gene (e.g. β-myosin), leading to LVH, specifically asymmetric interventricular septal hypertrophy. This causes LV outflow tract obstruction and thus ↓cardiac output, as well as diastolic dysfunction from poor LV filling.
  • Autosomal dominant (50%) or spontaneous.
  • Commoner in males, prevalence 1/500.

  Signs and symptoms

  Ranges from asymptomatic to sudden cardiac death (SCD) as first presentation.

  Symptoms:

  • SOB. Commonest symptom.
  • Angina
  • Syncope. Higher risk of sudden cardiac death if present.
  • Palpitations

  Signs:

  • Auscultation: ejection systolic murmur, especially on standing. S4 heart sound.
  • Palpation: hyperdynamic (possibly double) apical beat. Jerky pulse.
  • Signs of complications: LVH, AF, WPW.

  Investigations

  ECG:

  • Deep and narrow ('dagger') Q-waves in lateral and inferior leads, LVH.
  • Normal in 25%.
  • AF is a common complication of HCM.

  Imaging:

  • CXR may show cardiomegaly.
  • Echo: LVH, especially septal.

  Screening:

  • Echo in 1st-degree relatives.
  • Some advocate ECG screening in all athletes.

  Management

  • Conservative: no treatment may be needed if asymptomatic and at low risk of SCD, but avoid intense exercise.
  • Medical: if symptomatic, consider β-blocker or verapamil. Amiodarone, catheter ablation, or cardioversion may be needed for arrhythmias such as AF.
  • Surgical: septal myomectomy if refractory to medical treatment. ICD if high risk of SCD.

  Complications

  Benign for most but risk of SCD in young and HF in the elderly.

  Also:

  • Infective endocarditis.
  • Stroke due to AF.

• Restrictive cardiomyopathy

  Pathophysiology

  Rigid walls → diastolic dysfunction and ↓cardiac output. Causes:

  • Idiopathic
  • Amyloidosis
  • Haemochromatosis
  • Systemic sclerosis.
  • Loffler's eosinophilic endocarditis.
  • Tropical endomyocardial fibrosis.

  Signs and symptoms

  • RVF symptoms.
  • ↑JVP with prominent x + y descents.
  • Kussmaul's sign: ↑JVP with inspiration.

  Management

  Treat cause, and usual management of HF.

• Takotsubo cardiomyopathy

  Aka stress cardiomyopathy, broken heart syndrome.

  Pathophysiology

  • Transient left ventricular systolic dysfunction (LVSD) characterised by left ventricular apical ballooning.
  • Classically caused by negative emotional stress, though can also be triggered by physical stress, emotionally positive events, or no cause identified.
  • Likely due to catecholamine-mediated myocardial toxicity and/or coronary vasospasm.

  Epidemiology

  90% of cases are in women, mean age 67.

  Symptoms

  • Chest pain (75%).
  • SOB (50%).
  • Syncope (10%).

  Diagnosis

  Requires all 3 of:

  • Transient LVSD, as shown on echo.
  • ↑Troponin or new ST elevation on ECG (usually in anterior leads).
  • Absence of other cause e.g. coronary artery disease (CAD), HCM, myocarditis, phaeochromocytoma. If CAD present, diagnosis of takotsubo requires that any wall motion abnormalities are not in the same coronary artery distribution.

  Management and prognosis

  • Conservative management sufficient for most, with full resolution in 1-4 weeks.
  • β-blockers and ACEi may be used, though little research on efficacy and appropriate duration.
  • Standard treatment of acute pulmonary oedema and cardiogenic shock if they develop, except for the minority of patients with left ventricular outflow obstruction, who need β-blockers and not inotropes.
  • 30-day mortality <5%.

• Peripartum cardiomyopathy

  Defintion and epidemiology

  • Idiopathic cardiomyopathy that usually develops in the last month of pregnancy (10%) or in first 4 months post-partum (80%).
  • Diagnosis requires absences of other causes of cardiomyopathy e.g. familial, idiopathic. Insofar as these are unmasked by pregnancy, they tend to present earlier, by the 2nd trimester.
  • Echo typically shows dilated LV and EF <45%.
  • Affects around 1/3000 deliveries.

  Management

  • Manage like any other acute HF, except for avoidance of ACEi/ARB and spironolactone during pregnancy, due to fetal toxicity.
  • No evidence that early delivery improves outcomes.

  Prognosis

  • A minority progress to end-stage HF within days. Long-term mortality estimates (up to 5 years) in developed countries range from 2% to 10%.
  • LV function will recover in 50%.
  • Some degree of recurrence is common in subsequent pregnancies, and hence further pregnancy should be avoided in those whose LVEF has not recovered.