Dilated cardiomyopathy

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Dilated cardiomyopathy (DCM) is defined as left ventricular chamber dilation with decreased systolic function (FEVG <40%) in the absence of coronary artery disease or conditions which impose a chronic pressure overload. There may also be right ventricular dysfunction. Causes are related to intrinsic myocardial damage.

Pathology

The ventricles are dilated~~, thin-walled~~ and poorly contractile with normal or reduced wall thickness. The atria may also have a similar appearance and function.

Aetiology

Although a variety of aetiologies can result in a dilated cardiomyopathy which are listed as below. Some are classified as separate entities. (See WHO 1995 classification of cardiomyopathies)

ischaemic (coronary artery disease) - ischaemic cardiomyopathy
infectious (myocarditis: virus, bacteria)
infiltrative disease (sarcoid, amyloid)
metabolic (uraemia, hypocalcemia, hypophosphataemia, thyrotoxicosis)
toxic (alcohol, cocaine)
chemotherapy (doxorubicin)
others (peripartum, muscular dystrophies)
autoimmune cross-reactivity (e.g. late-onset cardiomyopathy in Chagas disease)
idiopathic: idiopathic dilated cardiomyopathy
familial: familial dilated cardiomyopathy ⁷

Associations

intra-cardiac thrombus

Radiographic features

Plain radiograph

Chest radiographs commonly show an enlarged left ventricle and atria with pulmonary oedema. Associated pleural effusions may also be seen.

Ultrasound: echocardiography

The degree of left ventricular dilatation is highly variable and depends on the stage of disease and severity of left ventricular dysfunction.

~~acute phase~~global chamber dilation with increased sphericity
- elevation in left ventricular mass and volumes
  - may be inferred by a measured elevation in LV end-diastolic internal diameter
    - the ~~ventricle~~LVIDd upper limit of normal is ~~just mildly dilated or~~5.9 cm in males and 5.3 cm in females
  - wall thickness may ~~even~~ be normal ~~in size because compensatory dilatation has not yet developed.~~
  - ~~those with additional volume overload (mitral~~(between 0.6 cm and 1.2 cm) or ~~aortic regurgitation) tend to have larger ventricles.~~reduced
- ~~chronic phase: with progressive dilatation~~the ratio between the ~~ventricle assumes a more spherical shape~~
~~The left ventricular wall is rather thin. However, as~~long and short axes of the left ventricle ~~is enlarged, the total~~ may decrease to 1 in severe cases

perturbation of systolic function

left ventricular ~~mass~~ejection fraction will decrease, although stroke volume may be ~~increased.~~initially preserved

diastolic dysfunction

with progressively higher E/e' ratio (correlates with left atrial pressure) as filling pressures elevate

Cardiac MRI

In idiopathic dilated cardiomyopathy, the left heart is markedly dilated and thinned, and mid wall enhancement, especially in the septum, is present in more than 50% of patients ⁴.

Late-enhancement MR images may demonstrate areas of fibrosis within the myocardium, characteristically in the mid- or subepicardial myocardium, allowing differentiation from ischaemic cardiomyopathy⁶.

Differential diagnosis

On plain radiographs consider:

large pericardial effusion

-<p><strong>Dilated cardiomyopathy (DCM)</strong> is defined as <a href="/articles/left-ventricle">left ventricular</a> chamber dilation with decreased systolic function (FEVG <40%). There may also be <a href="/articles/right-ventricle">right ventricular</a> dysfunction. Causes are related to intrinsic myocardial damage.</p><h4>Pathology</h4><p>The ventricles are dilated, thin-walled and poorly contractile. The atria may also have a similar appearance and function.</p><h5>Aetiology</h5><p>Although a variety of aetiologies can result in a dilated cardiomyopathy which are listed as below. Some are classified as separate entities. (See <a href="/articles/cardiomyopathy-whoisfc-1995-classification">WHO 1995 classification of cardiomyopathies</a>) </p><ul>
+<p><strong>Dilated cardiomyopathy (DCM)</strong> is defined as <a href="/articles/left-ventricle">left ventricular</a> chamber dilation with decreased systolic function (FEVG <40%) in the absence of coronary artery disease or conditions which impose a chronic pressure overload. There may also be <a href="/articles/right-ventricle">right ventricular</a> dysfunction. Causes are related to intrinsic myocardial damage.</p><h4>Pathology</h4><p>The ventricles are dilated and poorly contractile with normal or reduced wall thickness. The atria may also have a similar appearance and function.</p><h5>Aetiology</h5><p>Although a variety of aetiologies can result in a dilated cardiomyopathy which are listed as below. Some are classified as separate entities. (See <a href="/articles/cardiomyopathy-whoisfc-1995-classification">WHO 1995 classification of cardiomyopathies</a>) </p><ul>
~~-<li>acute phase<ul>~~
~~-<li>the ventricle is just mildly dilated or may even be normal in size because compensatory dilatation has not yet developed.</li>~~
~~-<li>those with additional volume overload (mitral or aortic regurgitation) tend to have larger ventricles.</li>~~
+<li>global chamber dilation with increased sphericity<ul>
+<li>elevation in left ventricular mass and volumes<ul>
+<li>may be inferred by a measured elevation in LV end-diastolic internal diameter<ul><li>the LVIDd upper limit of normal is 5.9 cm in males and 5.3 cm in females </li></ul>
+</li>
+<li>wall thickness may be normal (between 0.6 cm and 1.2 cm) or reduced</li>
+</ul>
+</li>
+<li>the ratio between the long and short axes of the left ventricle may decrease to 1 in severe cases<ul>
+<li>a normal LV has a LAX/SAX ratio around 1.5</li>
+<li>consequent mitral annular dilation and failure of coaptation leading to <a title="Mitral regurgitation" href="/articles/mitral-valve-regurgitation">mitral regurgitation</a> is common</li>
~~-<li>chronic phase: with progressive dilatation the ventricle assumes a more spherical shape</li>~~
-</ul><p>The left ventricular wall is rather thin. However, as the left ventricle is enlarged, the total left ventricular mass may be increased.</p><h5>Cardiac MRI</h5><p>In idiopathic dilated cardiomyopathy, the left heart is markedly dilated and thinned, and mid wall enhancement, especially in the septum, is present in more than 50% of patients <sup>4</sup>.</p><p>Late-enhancement MR images may demonstrate areas of fibrosis within the myocardium, characteristically in the mid- or subepicardial myocardium, allowing differentiation from ischaemic cardiomyopathy<sup> 6</sup>.</p><h4>Differential diagnosis</h4><p>On plain radiographs consider:</p><ul><li>large <a href="/articles/pericardial-effusions">pericardial effusion</a>
+</ul>
+</li>
+<li>perturbation of systolic function<ul><li>
+<a title="Left ventricular ejection fraction (echocardiography)" href="/articles/left-ventricular-ejection-fraction-echocardiography">left ventricular ejection fraction</a> will decrease, although stroke volume may be initially preserved</li></ul>
+</li>
+<li>
+<a title="Diastolic dysfunction (point of care ultrasound)" href="/articles/diastolic-dysfunction-point-of-care-ultrasound">diastolic dysfunction</a><ul><li>with progressively higher E/e' ratio (correlates with left atrial pressure) as filling pressures elevate</li></ul>
+</li>
+</ul><h5>Cardiac MRI</h5><p>In idiopathic dilated cardiomyopathy, the left heart is markedly dilated and thinned, and mid wall enhancement, especially in the septum, is present in more than 50% of patients <sup>4</sup>.</p><p>Late-enhancement MR images may demonstrate areas of fibrosis within the myocardium, characteristically in the mid- or subepicardial myocardium, allowing differentiation from ischaemic cardiomyopathy<sup> 6</sup>.</p><h4>Differential diagnosis</h4><p>On plain radiographs consider:</p><ul><li>large <a href="/articles/pericardial-effusions">pericardial effusion</a>

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echocardiography

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