• Clinical science

Cardiomyopathy

Abstract

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

  • 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
  • LVEF
  • Wall movement abnormalities
  • 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

ABCCCD: Alcohol use, Beriberi, Cocaine, Coxsackie B virus, Chagas, Doxorubicin/Daunorubicin

Pathophysiology

Clinical features

Diagnostics

Pathology

  • Macroscopy
  • Histology (idiopathic DCM)
    • Microscopic evaluation is mostly used to exclude other causes of cardiomyopathy
    • Interstitial fibrosis without interstitial inflammation
    • In particular, myocardial interstitial fibrosis is more extensive in the subendocardium because of its higher metabolic demand than the subepicardial layer.
    • Variation in the caliber of cardiomyocytes: cells may appear elongated and wavy with hypertrophy
    • Nuclear atypia

Treatment

Complications

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

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)

HCOM 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's point, left sternal border (laterally displaced due to myocardial hypertrophy)
  • S4 gallop due to thickened, non-compliant ventricle
  • Possible murmur from mitral regurgitation
  • Rapidly rising double arterial pulse in the carotid arteries

ECG

Echocardiography

  • Confirmatory test
  • Asymmetrically thickened left ventricular wall ≥ 15 mm
    • Septum thickness to inferoposterior wall thickness ratio > 1.3
  • Systolic anterior motion: protrusion of the anterior mitral valve cusp towards the septum
  • LVOT pressure gradient via doppler echocardiography
    • Provocation tests (see below) are obligatory if no obstruction is discernible at rest.

Exercise testing

  • Used for risk assessment and evaluation of LVOT
  • Treadmill or bicycle exercise test
  • Clinical observation for development of symptoms (e.g., dyspnea, palpitations)
  • Blood pressure monitoring , ECG , and echocardiography

Additional diagnostic procedures

  • Cardiac MRI
    • For evaluating ventricular morphology if echocardiographic results are ambiguous
    • For detecting areas of fibrosis and necrosis
  • Cardiac catherization including levocardiography
  • Possibly genetic testing and/or pedigree analysis

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][6][7][8][3][9][10][11][12][13][14]

Restrictive cardiomyopathy

Epidemiology

  • Very rare

Pathophysiology:

Etiology

Clinical findings

Diagnostics

Treatment

References:[1][3][15][16]

Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Epidemiology

  • Especially young adults

Etiology

Pathophysiology

Clinical findings

Very variable, many patients remain asymptomatic

Diagnostics

Treatment

Unclassified cardiomyopathies

Takotsubo cardiomyopathy

Left ventricular noncompaction

  • Definition: rare, inherited cardiomyopathy which is associated with structural abnormalities of the left ventricular myocardium (prominent trabeculations and deep intertrabecular recesses)
  • Clinical findings
  • Diagnostics: echocardiography and/or cardiac MRI: LV wall thickening, prominent trabecular meshwork, detection of abnormal flow (within the deep intertrabecular recesses)
  • Treatment: no causal treatment available
    • Avoid intense physical exertion
    • Symptomatic treatment of complications (e.g., heart failure)
    • Prevention of thromboembolisms
    • ICD
    • Heart transplant
    • Family and genetic counseling

Arrhythmia-induced cardiomyopathy

References:[17][18][19][20][21][22][23][24][25]