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

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.

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.

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.

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.