An infant case of double-chambered left ventricle with extensive non-compaction revealed by intraoperative endoscopy.

Coexistence of double-chambered left ventricle (DCLV) and left ventricular non-compaction (LVNC) is exceptionally rare and may present diagnostic challenges. We report a case of an 8-month-old girl who developed severe heart failure due to the combination of these two conditions. Transthoracic echocardiography revealed left ventricular dilatation and hypokinesia, consistent with a dilated cardiomyopathy-like phenotype, together with a septum-like structure dividing the cavity and swirling flow, raising suspicion of DCLV, although hyper-trabeculation could not be fully assessed. Because of persistent heart failure, a left ventricular assist device (LVAD) was implanted as a bridge to transplantation. Intraoperative endoscopy during LVAD implantation revealed a shelf-like septal partition, extensive non-compacted myocardium, and multiple fibromuscular string-like structures. Histopathology of the resected wall demonstrated preserved three-layered myocardium with endocardial fibroelastosis, intratrabecular sinusoids, and subendocardial fibrosis, consistent with LVNC. To our knowledge, this is the first report of infantile-onset heart failure due to combined DCLV and LVNC confirmed by detailed perioperative imaging and histopathology. This case highlights the morphological overlap between DCLV and LVNC and underscores the value of intraoperative endoscopic and histological evaluation when conventional imaging fails to adequately characterize complex ventricular morphology.

Learning objective The diagnosis and differential diagnosis of double-chambered left ventricle and left ventricular non-compaction can sometimes be challenging, as their morphology and pathophysiology may overlap. To highlight the diagnostic limitations of conventional imaging in cases with severe cardiac dilation and dysfunction, and to demonstrate how intraoperative endoscopy and histopathology can offer critical insights into rare congenital cardiomyopathies.