Flow acceleration and dynamic left ventricular outflow tract obstruction in neonatal warm shock: Echocardiographic phenotyping and management implications

Echocardiography is increasingly used to assess hemodynamics in critically ill neonates. We describe a novel echocardiographic phenotype associated with warm shock in preterm neonates with late-onset sepsis, ranging from left ventricular outflow tract (LVOT) acceleration to dynamic LVOT obstruction, with systolic anterior motion (SAM) of the mitral valve and secondary mitral regurgitation (MR). We retrospectively reviewed six consecutive preterm neonates with late-onset sepsis admitted between June 2024 and June 2025. All underwent neonatologist performed echocardiography (NPE) at the time of clinical deterioration. All neonates presented with signs of warm shock, including tachycardia and hyperdynamic circulation. NPE demonstrated aliasing across the LVOT on color Doppler and a dagger-shaped spectral Doppler profile, indicative of LVOT acceleration. In three cases dynamic LVOT obstruction with SAM and MR was demonstrated. Management included fluid boluses and vasopressors (norepinephrine); two cases required β-blockade (esmolol), resulting in resolution of obstruction and MR. This case series describes a previously unreported echocardiographic phenotype associated with warm shock in preterm neonates, characterized by a spectrum ranging from LVOT flow acceleration to dynamic LVOT obstruction with SAM and secondary MR. NPE enabled early identification and pathophysiological understanding, and tailored management. Prospective studies are needed to validate these findings.