• Clinical science

Cardiomyopathy

Summary

Cardiomyopathies are diseases of the muscle tissue of the heart. There are four major morphological types: dilated, hypertrophic, restrictive, and arrhythmogenic right ventricular cardiomyopathy.

In dilated cardiomyopathy, the most common type, ventricular output decreases eventually leading to failure of the left and right heart. The dilation can be seen on echocardiography, the most important diagnostic tool for all cardiomyopathies. Treatment is mostly similar to that of heart failure from other causes.

Hypertrophic cardiomyopathy can occur with or without left ventricular outflow obstruction. It is often asymptomatic, although arrhythmias and even sudden cardiac death can occur. The obstructive type is also notable for signs of reduced blood flow (dyspnea, vertigo, syncope). It is also diagnosed on echocardiography as manifests with an increased ventricular wall thickness, systolic anterior movement of the mitral valve, and an increased outflow tract pressure gradient. It is important that patients avoid strenuous exercise. Symptomatic patients should be treated with beta blockers.

Restrictive cardiomyopathy is caused by the proliferation of connective tissue with subsequent atrial enlargement (but normal ventricles). Like dilated myopathy, restrictive cardiomyopathy produces left and right heart failure. Ejection fraction is usually normal, but diastolic filling is reduced on echocardiography. There are different drugs that can be administered, based on individual factors.

Arrhythmogenic right ventricular cardiomyopathy affects primarily the right ventricle and is characterized by cellular breakdown and subsequent ventricular dilation. Symptoms are very variable although the hallmark finding is arrhythmia. There is no general best treatment as it depends entirely on individual factors such as the extent of the disease. All patients should avoid strenuous exercise.

Overview of major types of cardiomyopathy

Dilated cardiomyopathy

Hypertrophic cardiomyopathy

Restrictive cardiomyopathy Arrhythmogenic right ventricular cardiomyopathy

Pathophysiology

  • ↓ Ventricular contractility due to dilation → ↓ left ventricular ejection fraction (LVEF)
  • Hypertrophy of the left ventriclediastolic filling and systolic output → myocardial and peripheral perfusion
  • Left ventricular outflow obstruction in obstructive type
Distinctive clinical features

Echocardiography

  • Cardiac dilation → ↑ cavity size and ↓ wall thickness
  • LVEF
  • Wall movement abnormalities
  • Normal diastolic function
  • Thickened left ventricular wall
  • Outflow tract obstruction
  • Reduced diastolic filling but (nearly) normal EF
  • Dilated atria, nondilated ventricles
Other characteristics
  • Most common cardiomyopathy
  • Most common cause of sudden heart failure in athletes and teenagers
  • Most commonly in young adults

References:[1]

Dilated cardiomyopathy

Epidemiology

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

Etiology

Mnemonic for etiology of dilated cardiomyopathy: ABCCCD: A = Alcohol use, B = Beriberi, C = Cocaine, C = Coxsackie B virus, C = Chagas, D = Doxorubicin/Daunorubicin

Pathophysiology

Clinical features

Diagnostics

Pathology

Treatment

Complications

References:[2][3][4][5][6]

Hypertrophic cardiomyopathy

Epidemiology

Etiology

Pathophysiology

  • Obstructive and nonobstructive types: hypertrophy of the left (possibly also the right) ventricle resulting in:
    • Reduced diastolic compliance and filling of the ventricle → reduced diastolic filling volume → reduced systolic output volume
    • Impaired cardiac contractility with reduced systolic output → reduced peripheral and myocardial perfusion (myocardial ischemia)
  • Obstructive type (HOCM) also involves

Clinical features

  • Frequently asymptomatic (especially the nonobstructive type)
  • Obstructive type
  • Obstructive and nonobstructive type
    • Cardiac arrhythmias and palpitations
    • Sudden cardiac death (particularly during or after intense physical activity)

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

Diagnostics

Auscultation findings

  • Systolic ejection murmur (crescendo-decrescendo)
    • Increases with valsalva maneuver and standing
    • Decreases with hand grip, squatting, or passive leg elevation
  • Extended area of Erb point, left sternal border (laterally displaced due to myocardial hypertrophy)
  • S4 gallop due to thickened, non-compliant ventricle
  • Possible murmur from mitral regurgitation

ECG

Echocardiography

Pathology

Concentric hypertrophy: increased left ventricular wall thickness and decreased left ventricular size (sarcomeres are added in parallel).

Treatment

  • All patients should avoid strenuous exercise.
  • Asymptomatic patients usually do not require further treatment.
  • Symptomatic patients

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

References:[2][2][7][8][9][3][10][11][12][13][14][15]

Restrictive cardiomyopathy

Epidemiology

  • Very rare

Pathophysiology

Proliferation of connective tissue↓ elasticity of myocardium↓ ventricular compliance; diastolic filling → atrial congestion → atrial enlargement and severe diastolic dysfunction

Etiology

Mnemonic for etiology of restrictive cardiomyopathy: Puppy LEASH: P = Postradiation fibrosis, L = Löffler endocarditis, E = Endocardial fibroelastosis, A = Amyloidosis, S = Sarcoidosis, H = Hemochromatosis

Clinical findings

Diagnostics

Treatment

References:[1][3][16][17]

Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Epidemiology

  • Especially young adults

Etiology

Pathophysiology

Right ventricular myocardial cell death (due to myocyte apoptosis, inflammation and fatty/fibrotic tissue replacement) → thinning of the ventricular wall → dilation of the right ventricleventricular arrhythmia and dysfunction

Clinical findings

Very variable, many patients remain asymptomatic

Diagnostics

Treatment

Unclassified cardiomyopathies

Takotsubo cardiomyopathy

Arrhythmia-induced cardiomyopathy

References:[18][19][20][21][22][23][24][25][26]