Cardiomyopathies (CMO)

1. DILATED CMO

• Dilation and impaired contraction of the LV and often RV
• Characterised by enlarged ventricles, preserved wall thickness and systolic dysfunction

Etiology

• MC in men
• Alcohol
• 25% of cases are inherited – AD
  • Mutations affect proteins in the myocyte cytoskeleton – e.g. dystrophin, lamin A + C
  • X-linked inherited skeletal muscular dystrophies are associated with CMO – e.g. Becker, Duchenne
• Autoimmune reaction to viral Myocarditis

Pathophysiology

• After damage to the myocardium, some of the myocardial cells undergo necrosis
  • Results in chronic fibrosis
  • The remaining myocardial tissue then dilates and hypertrophies to compensate
• Dilation of valve rings – leads to mitral or tricuspid regurgitation
• Atrial fibrillation can occur as a result of atrial dilatation
• Thrombus formation can occur in the large dilated chambers

Clinical features

• Patients can present with HF
• Arrhythmia, thromboembolism, sudden death
• Chest pain

Diagnosis

• CXR – enlarged heart. Signs of HF
• Echo/cardiac MRI – to establish diagnosis

Treatment

• Prophylactic anticoagulation – warfarin
• Control the resulting HF
  • BB and ARBs – to reduce risk of sudden arrhythmic death in HF pts
• ICD implantation
• Heart transplant in young pts

2. HYPERTROPHIC CMO – MC

• AD disorder – causes diastolic dysfunction, with/without outflow obstruction
• Hypertrophy of the LV – causes LV outflow obstruction, MV problems, myocardial ischemia

Epidemiology

• MC in men and black people
• MCC of sudden cardiac death in young people
• Presents between 20-40 years

Etiology

• AD
• Troponin T mutations

Pathophysiology

• Genetic defects in genes that code for cardiac proteins – e.g. β-myosin
• Results in a disorganised cardiac matrix and LVH
  • Hypertrophy is MC in the anterior ventricular septum

Clinical features

• Most cases are asymptomatic
• Dyspnoea, chest pain
• Syncope – especially on exercise
  • Common in athletes
• Palpitations
• Sudden death – due to syncope, arrhythmia or outflow tract obstruction

Signs

• Forceful apex beat
• Late ejection systolic murmur
• Prominent JVP
• Abnormal BP response to exercise – in normal pts SBP rises 25mmHg
  • In HCM it rises less than this

Diagnosis

• ECG – nonspecific, atrial fib (AF)
• Echo – standard diagnosis test
  • Asymmetrical septal hypertrophy
  • Non-dilated LV cavity
  • Normal systolic function

Treatment

• Control arrhythmias
• Antigcoag for AF
• Reduce outflow tract obstruction and improve diastolic function
  • BB, verapmil – they reduce cardiac contractility and dilate the hypertrophied LV, so reduce outflow tract obstruction and improve diastolic function
• Myectomy – to reduce outflow tract obstruction
• ICD

3. RESTRICTIVE CMO

• Due to reduced compliance of the ventricular walls during diastolic filling – ventricles are stiff
• Bi-atrial enlargement
• Causes high atrial pressures with pulmonary congestion and eventually HF

Epidemiology

• MC in elderly

Etiology

• Usually no underlying cause is identified
• Amyloidosis
• Sacoidosis
• Lofflers endocarditis

Clinical features

• Symptoms of HF – dyspnoea, fatigue, pulmonary oedema
• Features of RV failure
  • ↑JVP, hepatomegaly, oedema, ascites
• 75% patients develop AF

Diagnosis

• CXR – pulmonary venous congestion
• Echo – symmetrical myocardial thickening, impaired ventricular filling
• MRI – myocardial fibrosis in amyloidosis/sarcoidosis
• Endomyocardial biopsy

Treatment

• Treat underlying cause
• Don’t give diuretics – they ↓preload (stiff ventricles rely on preload for filling)
• Don’t give digoxin – amyloidosis pts often have extreme digoxin sensitivity
• Heart transplant