• Clinical science

Cardiomyopathy

Summary

Cardiomyopathies are diseases of the muscle tissue of the heart. There are three major types: dilated, hypertrophic, and restrictive cardiomyopathy.

Dilated cardiomyopathy (DCM) is the most common type of cardiomyopathy. Although most cases are idiopathic, a number of conditions (e.g., coronary artery disease, wet beriberi), infections (e.g., Coxsackie B virus, Chagas disease), and substances (e.g., heavy drinking, cocaine) have been identified as causes. In DCM, the decreased ventricular contractility of the dilated left ventricle (LV) leads to failure of the left and eventually right heart with decreased ventricular output. Isolated dilation and subsequent decrease in contractility of right ventricle (RV) is rare. Dilation can be seen on echocardiography, the most important diagnostic tool for all cardiomyopathies. Therapy involves management of congestive heart failure and treatment of the underlying condition.

Hypertrophic cardiomyopathy (HCM) is the second most common cardiomyopathy. There are two types of HCM: The nonobstructive type is characterized by a thickening of the LV wall and is often asymptomatic, although arrhythmias and even sudden cardiac death can occur. The obstructive type (HOCM) is characterized by a thickening of the interventricular septum and systolic anterior movements of the mitral valve, causing LV outflow obstruction. HOCM manifests with signs of reduced blood flow (dyspnea, dizziness, syncope). Both types are diagnosed with echocardiography. Even if most individuals are asymptomatic, it is important that they avoid strenuous exercise. Symptomatic patients should be treated with beta-blockers.

Restrictive cardiomyopathy (RCM) is caused by the proliferation of connective tissue, with subsequent atrial enlargement (but normal ventricles). Like DCM, RCM causes left and right heart failure. The ejection fraction is usually normal, but diastolic filling is reduced on echocardiography. While a number of drugs offer symptomatic relief, the overall prognosis remains poor.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) primarily affects the right ventricle and is characterized by fibrofatty replacement of myocardium, which causes myocardial thinning and subsequent ventricular dilation. Although the hallmark finding is arrhythmia, symptoms are highly variable. Because management depends greatly on individual factors, such as the extent of the disease, there is no single best course of treatment. All patients should avoid strenuous exercise.

Overview of major types of cardiomyopathy

Dilated cardiomyopathy

Hypertrophic cardiomyopathy

Restrictive cardiomyopathy

Pathophysiology

Distinctive clinical features
Echocardiography LV cavity size
  • Significantly increased
  • Decreased
  • Decreased
EF
  • Significantly decreased
  • Significantly decreased
  • Normal or increased
Wall thickness
  • Normal or decreased
  • Significantly increased
  • Usually increased
Additional findings
  • Left ventricular (and atrial) dilation
  • Wall movement abnormalities
  • Normal diastolic function
  • Outflow tract obstruction (SAM, interventricular septum hypertrophy)
  • Reduced diastolic filling but (nearly) normal EF
  • Dilated atria, nondilated ventricles
Other characteristics
  • Most common cardiomyopathy
  • Second most common cardiomyopathy
  • Most common cause of sudden heart failure in athletes and teenagers

References:[1]

Dilated cardiomyopathy

Epidemiology

  • Most common cardiomyopathy
  • Incidence: 6/100,000 per year
  • Sex: > (approx. 3:1)

Etiology

To remember some high-yield secondary causes of dilated cardiomyopathy, think ABCCCDD: A = Alcohol use, B = Beriberi, C = Cocaine, C = Coxsackie B virus, C = Chagas, D = Doxorubicin/Daunorubicin

Pathophysiology

Clinical features

Diagnostics

Approach

  • Diagnostic approach to DCM aims to:
    1. Investigate the underlying cause with confirming either the secondary cause or idiopathic disease
    2. Assess cardiac function
    3. Assess structural remodeling
  • Specific investigations are guided by suspected underlying cause or complications

Investigations [3]

Pathology

Treatment

Complications

References:[4][5][6][7][8]

Hypertrophic cardiomyopathy

Epidemiology [9]

  • Second most common cardiomyopathy
    • Obstructive type/hypertrophic obstructive cardiomyopathy (HOCM): ∼ 70% of cases
    • Nonobstructive type: ∼ 30% of cases
  • Alongside myocarditis, HCM is one of the most frequent causes of sudden cardiac death in young patients, especially young athletes.

Etiology [9][10]

Pathophysiology [11]

Clinical features [13]

HOCM is an important cause of sudden cardiac death in young patients!

Diagnostics [13][14][15]

Pathology

Treatment [14][18][15]

Positive inotropic and afterload-reducing or preload-reducing drugs (e.g., digitalis, glyceryl trinitrate, calcium channel blockers of the dihydropyridine class, ACEIs) are contraindicated in patients with obstructive hypertrophic cardiomyopathy!

References:[4][4][19][20][13][5][14][18][15][21][10][22]

Restrictive cardiomyopathy

Epidemiology

  • Least common cardiomyopathy
  • Prevalence: 1:500 [4]

Etiology

Etiology of restrictive cardiomyopathy: Puppy LEASH: P = Postradiation/Postsurgery fibrosis, L = Löffler endocarditis, E = Endocardial fibroelastosis, A = Amyloidosis, S = Sarcoidosis, H = Hemochromatosis

Pathophysiology

Clinical features

Diagnostics

Treatment

References:[1][5][28][29]

Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Epidemiology

  • Most common in young adults (mean age at diagnosis: ∼ 30 years) [30]
  • Prevalence: 1:1000–2000 [31]

Etiology

Pathophysiology

Clinical features

Diagnostics [31][30][33]

Approach

ARVC is diagnosed based on the AHA criteria which include five groups of features:

  1. Dysfunction and structural abnormalities of RV (can be revealed by echocardiography, MRI, or RV angiography)
  2. Histological characteristics (require myocardial biopsy)
  3. Abnormal repolarization (diagnosed with ECG)
  4. Depolarization/conduction abnormalities (diagnosed with ECG)
  5. Arrhythmias (diagnosed with ECG)
  6. Family history (confirmation of ARVC in a relative either by criteria, pathological examination in surgery or autopsy, or by genetic testing)

Findings

Management [33]

Unclassified cardiomyopathies

Takotsubo cardiomyopathy

Left ventricular noncompaction

Arrhythmia-induced cardiomyopathy

References:[34][35][36][37][38][39][40][41][42]