Left-ventricular (LV) hypoplasia encompasses a range of LV sizes, varying from a mildly underdeveloped, but functionally adequate, chamber to the miniscule, barely perceptible LV cavity seen in hypoplastic left-heart syndrome. Associated malformations include obstructive lesions of LV inflow, outflow, and the aortic arch, often in combination. Repair of complex combinations and/or severe LV hypoplasia usually results in a single-ventricle anatomy with the right ventricle serving as the systemic ventricle. New therapeutic interventions, including fetal procedures, are expanding the spectrum of lesions and LV sizes that may be amenable to a biventricular repair. These surgical considerations place renewed emphasis on understanding the anatomical features associated with LV hypoplasia. This review details pathological features of the full spectrum of LV hypoplasia, particularly those with borderline severe hypoplasia. Primary defining lesions are described as well as additional lesions that may affect clinical symptoms, surgical repair, and long-term outcome.
Keywords: borderline hypoplasia; hypoplastic left-heart syndrome.