Hypoplastic left heart syndrome: current considerations and expectations

Abstract

In the recent era, no congenital heart defect has undergone a more dramatic change in diagnostic approach, management, and outcomes than hypoplastic left heart syndrome (HLHS). During this time, survival to the age of 5 years (including Fontan) has ranged from 50% to 69%, but current expectations are that 70% of newborns born today with HLHS may reach adulthood. Although the 3-stage treatment approach to HLHS is now well founded, there is significant variation among centers. In this white paper, we present the current state of the art in our understanding and treatment of HLHS during the stages of care: 1) pre-Stage I: fetal and neonatal assessment and management; 2) Stage I: perioperative care, interstage monitoring, and management strategies; 3) Stage II: surgeries; 4) Stage III: Fontan surgery; and 5) long-term follow-up. Issues surrounding the genetics of HLHS, developmental outcomes, and quality of life are addressed in addition to the many other considerations for caring for this group of complex patients.

Figure 1. Fetal Echocardiograms

(A) Four-chamber view of a fetal echocardiogram at 20 weeks’ gestation demonstrates a dilated left ventricle with echo bright endocardium suggestive of endocardial fibroelastosis. The position of the atrial septum suggests abnormal left atrial to right atrial shunting in utero. (B) Four-chamber view of a fetal echocardiogram in the same fetus imaged at 33 weeks’ gestation demonstrates that the left ventricle has become hypoplastic. The echo bright endocardium is even more evident. LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle; Sp = spine.

Figure 2. Complication Risk Associated With Superior Venous Oximetry

Risk of complication according to post-operative superior venous oximetry saturation (SvO₂) assessed hourly during first 48 h. *Significant difference from risk at lower SvO₂ in time-series regression. CPR = cardiopulmonary resuscitation; ECMO = extracorporeal membrane oxygenator. Reprinted with permission from Tweddell et al. (80).

Figure 3. Hemodynamic Monitoring in the Immediate Post-Operative Period

Multichannel recording of the arterial saturation (SaO₂), mean arterial blood pressure (MAP) and superior vena cava saturation (SvO₂) during the first 4 h after the Norwood procedure. Two episodes of decreased SvO₂ were identified. Fall in SvO₂ was mirrored by changes in MAP. Fall in SvO₂ was initially mirrored by changes in SaO₂, but with a marked decline in SvO₂, the SaO₂ decreased as well. These changes indicate that acute changes in SvO₂ can occur and are not reliably identified by changes in SaO₂ or MAP. Reprinted with permission from Tweddell et al. (73).

Figure 4. Superior Venous Saturation During the First 48 h After Norwood Procedure

The SvO₂ was significantly higher during hours 1 to 10 in infants treated with phenoxybenzamine (0.25 mg · kg at commencement of cardiopulmonary bypass + selective use of continuous infusion 0.25 · mg · kg · day) than in those treated with milrinone (load 50 μg · kg · min prior to separation from bypass + continuous infusion 0.5 μg · kg · min after surgery). Reprinted with permission from Tweddell et al. (73).

Figure 5. Oxygen Saturation by Age at Surgery for Stage II Palliation

Patients undergoing early (<4 months) Stage II palliation initially had lower arterial saturation although they were not different than older patients at the time of hospital discharge. Reprinted with permission from Jaquiss et al. (193).

Figure 6. Fontan Surgical Techniques

The original atriopulmonary Fontan (A) has been replaced with the lateral tunnel (B) and extracardiac conduit (C) Fontan. Reprinted with permission from de Leval (488).

Figure 7. Computational Simulation as an Emerging Tool

Representative Fontan model showing angiography and computational simulation-derived measures of wall shear stress. The red areas indicate higher levels of shear (when compared with blue or green).