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5.3.1 Genetic forms of dilated cardiomyopathy

Advances in genetic research have shown that inherited forms play a much greater role than previously thought. A familial etiology is suspected in 30% or more cases. We now have a long list of “dilated cardiomyopathy genes” that may cause malfunction of proteins which control myocardial integrity and function (i.e. cytoskeletal and sarcomeric proteins). Mutations of these genes may result in contractile dysfunction or a predisposition for cardiomyopathy. Genetic forms of dilated cardiomyopathy may be sporadic or familial. Echocardiography plays an important role in family screening and should be performed when the patient’s relatives have a history of:

  • dilated cardiomyopathy
  • sudden cardiac death
  • unexplained sudden death in persons < 50 years of age.
  • unexplained conduction disease
Some genes responsible for dilated cardiomyopathy are also involved in hypertrophic cardiomyopathy.

5.3.1.1 Isolated left ventricular non-compaction

Isolated left ventricular non-compaction is a genetic form of cardiomyopathy caused by aborted myocardial morphogenesis. It is typically accompanied by very prominent trabeculations and a “spongy” appearance of the myocardium. Specific portions of the ventricle may be affected more strongly than others. Most commonly, hypertrabeculation is seen at the apex and the postero-lateral or inferior wall.

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Isolated Non compaction syndrome with reduced left ventricular function and spongy appearance of the myocardium (Especially distal postero-lateral)
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More subtle form of isolated non-compaction in which the prominent trabeculation is limited to the postero-lateral wall (magnified view)
Also use the coronary sinus view and atypical views to visualize the trabeculated myocardium.
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Atypical view transecting the left ventricle at its base. These views are best suited to demonstrate the spongy appearance of the myocardium

A non-compaction syndrome may be assumed when the patient has more than three trabeculae in the apical aspect of the papillary muscles. However, this and all other definitions proposed for this condition are not very practical. Actually it still is the visual impression of a strongly trabeculated and spongy myocardium that should cause the clinician to suspect a non-compaction syndrome.

The non-compaction to compact cardiac tissue ratio (NC/C ratio) was suggested as a means of establishing the diagnosis and determining the degree of involvement. A ratio higher than 2:1 is “diagnostic”. Its true clinical relevance, however, is unclear.

Patients with non-compaction syndrome frequently have reduced left ventricular function, although this is by no means applicable for all patients. A follow-up echocardiography should also be performed in patients with suspected non-compaction and normal left ventricular function because they are subject to a high risk of developing overt cardiomyopathy. The disease may be manifested at any age. In general, patients with left ventricular non-compaction have a rather poor prognosis and need to be monitored at close intervals.

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Non-compaction in a patient with normal ejection fraction. Longitudinal strain analysis shows reduced contractility in the basal anterior, septal, and inferior regions.
More than one half of cases are of familial origin, although a large number of relatives may be asymptomatic. Thus, echocardiographic screening of family members is strongly advised.

It may be difficult to distinguish between non-compaction syndrome and other forms of cardiomyopathy in which the trabeculae just appear very prominent. Especially remodeled hypertrophic left ventricles (i.e. hypertensive heart disease) may look very similar.

Contrast echocardiography helps to visualize areas on non-compaction.

Strain imaging (speckle tracking echocardiography) is useful in patients with normal ejection fraction and isolated non-compaction syndrome. It may be used to distinguish these patients from persons with normal hearts and prominent trabeculae. In contrast to patients with isolated non-compaction, these patients have a normal longitudinal strain pattern.

Left ventricular non-compaction may also be associated with congenital abnormalities such as ventricular septal defects, pulmonary stenosis, or atrial septal defects, as well as neuromuscular disorders.
Genetics of left ventricular non-compaction
Alpha-dystrobrevin ( DTNA)protein involved in the dystrophin-associated complex
Cypher/ ZASPencodes for a part of the Z-line in cardiac and skeletal muscle, participating in the assembly and targeting of cytoskeletal proteins
TAZgene with unknown function causing X-linked dilated cardiomyopathy, which suggests that the pathophysiology of left ventricular non-compaction is similar to that of dilated cardiomyopathy with cytoskeletal protein mutation