Hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) is associated with a systemic right ventricle and a remnant left ventricle. The disease represents a spectrum, with the left ventricular cavity appearing of various sizes but being insufficient to sustain a bi-ventricular physiology. The competency of the tricuspid valve is important to assess, as it will become the atrio-ventricular valve of the systemic ventricle. HLHS may also be associated with a globular shape of the right ventricle and various degree of fibro-endoelastosis (often appearing as brightness of the endocardium on echocardiography). One may classify based on the aortic and mitral valve anatomy/physiology. Categories include: mitral stenosis / aortic stenosis (MS/AS), mitral stenosis / aortic atresia (MS/AA), mitral atresia / aortic atresia (MA/AA) or mitral atresia / VSD / aortic stenosis. The entire pulmonary venous return is dependent on the size of the inter-atrial communication. As such, an intact or restrictive atrial septum is of particular concern and may be associated with fetal pulmonary vascular remodelling. As these patients are dependent on low pulmonary vascular resistance to complete the single ventricular palliation, a re-modeled pulmonary vascular bed is of great concern. More on HLHS here.

HLHS is a PGE-dependent condition. Indeed, systemic perfusion is dependent on patency of the ductus, until initial surgery to ensure adequate source of systemic blood flow. As such, this patient has a large PDA that is shunting bidirectional. Because of the decreased systemic perfusion, the intestine are at particular risk of necrotizing enterocolitis, although the data regarding feeding practices are controversial in the pre-operative setting.

This particular patient has signs of acceleration of flow at the level of the inter-atrial septum. Hence, there is restriction of flow which may lead to significant pulmonary edema. In the context of dropping pulmonary vascular resistance, as the pulmonary blood flow increases (via the ductus arteriosus maintained opened), the gradient via the inter-atrial communication may increase.

Evaluation of the function of the single ventricle in HLHS is challenging. One marker used is the dp-dt of the right ventricle from the CW-Doppler of the tricuspid regurgitant jet.

Created by Gabriel Altit - Neonatologist / Créé par Gabriel Altit (néonatalogiste) - © NeoCardioLab - 2020