TRPM4 Mutation in Patients With Ventricular Noncompaction and Cardiac Conduction Disease
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Left ventricular noncompaction (LVNC) is characterized by abnormally prominent trabeculations and deep intertrabecular recesses in the left ventricle.1 LVNC can range from asymptomatic to end-stage heart failure and lethal arrhythmias, which lead to sudden cardiac death. Mutations associated with sarcomere proteins, ion channels, and developmental transcription factors have been identified in patients with LVNC.1
The proband was diagnosed with incomplete right bundle branch block at 5 years old. At 16 years old, he was diagnosed with complete right bundle branch block and frequent premature ventricular contraction. At 25 years old, he was diagnosed with complete atrioventricular block and left ventricular dysfunction, and a permanent pacemaker was implanted. His echocardiogram exhibited prominent trabeculations and deep intertrabecular recesses in the apical to midventricular lateral wall. The noncompacted zone/compacted zone ratio was 2.3 (Figure A). Subsequently, symptoms of left ventricular dysfunction became progressively more severe despite medication and cardiac resynchronization therapy, and he eventually died of heart failure. The autopsy findings showed dilated ventricular lumen, whitish and filamentous prominent trabeculations in the ventricle, and thin compacted myocardium (Figure B). Microscopic findings showed displacement of the atrioventricular node by a fatty tissue (Figure C) and loss of the Purkinje fibers. Thickened endocardium and subendocardial fibrosis were seen, and fibrosis of trabeculae and interventricular septum were more prominent than previously reported cases.2 Mild anastomosing broad trabeculae and staghorn-like endocardial lined spaces were seen (Figure D). A fibrous band was not apparent. These findings were consistent with LVNC …