Dilated cardiomyopathy

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Dilated cardiomyopathy (congestive cardiomyopathy, DCM), is a myocardial disease resulting in dilatation of the chambers of the heart with poor contractile function resulting in inability to pump blood efficiently. DCM is a type of cardiomyopathy which is a group of diseases that primarily affect the myocardium Different cardiomyopathies have different causes, and affect the heart in different ways. In DCM a portion of the myocardium is dilated, often without any obvious cause. Left and/or right ventricular systolic pump function of the heart is impaired, leading to progressive cardiac enlargement and hypertrophy, due to remodeling.[1] Echocardiography is a key diagnostic tool in diagnosing and following up patients with dilated cardiomyopathy.

Contents

Aetiology

  • Idiopathic - genetically heterogenous group with mutations involving a variety of genes coding for cardiac muscle proteins. Can be familial.
  • Toxic
    • Excessive alcohol intake
    • Anthracyclines (Daunorubicin and Doxorubicin)
    • cocaine
  • Pregnancy
  • Infections
    • Viral - myocarditis resulting from Ebstein-Barr virus, Cytomegalovirus,coxsackie B virus, adenovirus, parvovirus.[2]
    • Parasitic - Chaga's disease
  • Muscular dystrophies -Duchenne's, Becker's, Myotonic dystrophy etc.
  • Endocrine - Thyrotoxicosis, Diabetes
  • Autoimmune disorders[3]
  • Thiamine deficiency
  • Chronic tachycardia related cardiomyopathy
  • Ischemic cardiomyopathy

Clinical Presentation/Diagnosis

Patients with DCM demonstrate independently of the etiology signs of heart failure including dyspnea, orthopnea, impaired exercise capacity and peripheral edema. Also conduction disturbances and arrhythmic events can be observed like left bundle branch block (LBBB) and supraventricular or ventricular arrhythmias which manifestation can be sudden cardiac death.

The diagnosis and monitoring generally consists of ECG, chest X-Ray, Laboratory examinations, and invasive methods including angiography and/or endomyocardial biopsy, MRI and echocardiography. Findings in the ECG can be conduction disturbances (e.g. LBBB), supraventricular arrhythmias (e.g. atrial fibrillation) or ventricular arrhythmias (e.g. non-sustained ventricular tachycardia). The chest X-Ray is important for diagnosis and monitoring of lung congestion. Angiography is because of the high incidence of ischemic heart disease as one of the top-ranking reasons for DCM an important examination to exclude relevant stenosis of coronary vessels. Additional to the angiography an endomyocardial biopsy can be performed to exclude other secondary causes for DCM like myocarditis or storage diseases.

Echocardiography

Echocardiography enables to evaluate many aspects of this disease and is therefore the diagnostic tool of choice. Echocardiography offers several methods to assess the cardiac function and morphology. Most commonly an enlarged left ventricle (> 30 mm/m² anterior-posterior diameter or volumes > 90 ml/m²) can be observed, often associated with a dilated left atrium (>40 mm anterior-posterior diameter or volumes >32 ml/m²). Also the right heart might be affected in advanced cases.

The dysfunction affects systole (impaired contractility, ejection fraction [<40 %] and impaired cardiac output), as well as diastole (diastolic dysfunction, increased filling pressures), affecting most of the time the whole myocardium, although also regional abnormalities can be observed. Furthermore, dilatation and development from the usual ovoid to a spherical geometry of the left ventricle lead oftentimes to mitral regurgitation, which may contribute to the impairment of the pumping capacity.

The presence of mechanical left ventricular dyssynchrony seems to be an important factor for the treatment and prognosis of DCM. Tissue Doppler imaging (TDI) is a tool to assess this aspect. The intra left ventricular dyssynchrony is defined as an electromechanical delay (EMD) difference of ≥40 ms in 2 opposed left ventricular wall regions (septal vs. lateral, anterior vs. inferior). There are new approaches for the assessment of dyssynchrony including promising visual methods like septal flash and apical rocking (also called apical transverse motion).

Some studies show a favorable effect of cardiac resynchronization therapy in patients with mechanical left ventricular dyssynchrony. However, there is no consensus yet regarding the evidentiary measurements to be carried out. Until now, there are no randomized controlled trials which demonstrated additional benefits for performing these measurements in comparison to the existing guidelines for CRT implantation.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) is able to detect scars and myocardial fibrosis in approximately 30 % of all patients with DCM and an amount of myocardial fibrosis > 2 g by late contrast agent accumulation (late gadolinium enhancement, LGE). It is important to mention that the real amount of myocardial fibrosis will be underestimated with this method since yet only focal myocardial fibrosis can be detected due to the limits of spatial resolution. If only patients with DCM due to inflammatory processes in the past demonstrate myocardial fibrosis remains unclear yet. In DCM fibrosis patterns are highly variable, on the one hand comparable with lesions caused by myocarditis and on the other hand there are patterns with central intramural lesions (“central line sign” or “midwall sign”). The detection of myocardial fibrosis in DCM on MRI predicts a worsened outcome of these patients regarding the combined end-point of death, transplantation or hospital admission due to heart failure. A detailed analysis demonstrated an association between prognosis and amount of LGE in combination with impaired left ventricular ejection fraction. In patients with minimal myocardial fibrosis and preserved left ventricular ejection fraction the negative prognostic value of LGE remained limited.

Treatment/Prognosis

The first step for the treatment of DCM is in the case of a secondary etiology the treatment of the underlying disease or leave out the cardiotoxic substances. Otherwise the therapy for DCM is comparable with the treatment for congestive heart failure that consists of:

  • Drug therapy
  • ICD
  • CRT
  • LVAD
  • Heart transplantation

The prognosis depends on the clinical symptoms and the heart function. Patients with dyspnea NYHA ≥ III, LV-EF ≤ 25% and low peak oxygen consumption have a poor prognosis.

References

  1. Harrison's Principles of Internal Medicine, 16th edition. Kasper, Braunwald, Fauci, Hauser, Longo, Jameson. ISBN 0-07-139140-1
  2. Martino TA, Liu P, Sole MJ. Viral infection and the pathogenesis of dilated cardiomyopathy. Circ Res. 1994;74:182-8. PMID 8293557
  3. San Martin MA, Garcia A, Rodriguez FJ, Terol I. Dilated cardiomyopathy and autoimmunity: an overview of current knowledge and perspectives. Rev Esp Cardiol. 2002;55:514-24. PMID 12015932
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