Left Ventricular Noncompaction Cardiomyopathy and Long QT Syndrome, a Common Cause? A Case Report

Objectives: Long QT syndrome (LQTS) is an inherited arrhythmia due to mutations especially in genes of cardiac ion channels. Left ventricular non-compaction cardiomyopathy (LVNC) is a heart muscle disease which can be diagnosed by echocardiography and cardiac magnetic resonance imaging (MRI). Both diseases have a highly variable clinical presentation and complex genetic background.

Case report: A 12-year-old boy, who came for regular echocardiographic control because of a small hemodynamically not relevant ventricular muscle defect, got an MRI and a genetic analysis. The reason for this examination was a syncope of his mother (46 years) during exercise and the subsequent diagnosis of an non-compaction cardiomyopathy and detection of a published LQTS-mutation in the KCNH2-gene encoding a cardiac potassium channel. The MRI and genetic diagnostics of her son confirmed a non-compaction cardiomyopathy of the left ventricle and the same mutation respectively. The ECG at rest shows a normal QTc-interval, during exercise-testing there is a prolongation from 415 to 435ms. Comparing the form of the ECG with the healthy brother it reveals a prolonged increase of the T-wave also present in his mother's ECG. A brother (52 years) of the mother had an unclear incident with an resuscitation which resulted in a coma. We treat the boy with β-blocker and because he was very active in sports we recommended a moderate form of sport which is not competitive.

Conclusion: To our knowledge this is the third publication about the combination of LQTS and LVNC. There might be a combined genetic background for these diseases as the cardiac sodium channel for example seems to be a serious candidate gene for LVNC. Further genetic research is necessary to find out if the KCNH2-gene is not only responsible for the LQTS but also for the LVNC like for example a mutation in the SCN5A gene occurs in patients with Brugada syndrome and dilated cardiomyopathy. Therefore, a combined LVNC/LQTS diagnostic and risk stratification including ECG with exercise testing, echocardiography, MRI and genetic analysis should be considered.

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