Right Ventricular Apical Hypoplasia With a Novel Morphologic Presentation

BACKGROUND: Right ventricular apical hypoplasia is a rare congenital anomaly characterized by the failure of the right ventricular (RV) apical portion to develop. CASE SUMMARY: A 9-year-old boy presented with chronic cyanosis and digital clubbing. Multimodal imaging revealed a severely hypoplastic, dysplastic RV with lobulated contours. Cardiac magnetic resonance demonstrated a unique compensatory phenomenon, where the left ventricular apex was elongated and projected rightward, creating "Christmas hat" morphology. DISCUSSION: This case demonstrates a ventricular configuration that has not been previously described: a RV apical hypoplasia characterized by an elongated apical portion of the left ventricle. This elongation likely occurs in compensation for the apical agenesis of the RV. Identifying this "Christmas hat" sign could be helpful in diagnosing this rare form of RV hypoplasia. TAKE-HOME MESSAGE: Hypoplastic RV with elongation of the apical portion of the left ventricle toward the lateral wall of the RV, associated with an aneurysm of the interventricular septum, is described.