Palliation Outcomes of Neonates Born With Single-Ventricle Anomalies Associated With Aortic Arch Obstruction

Surgical palliation of univentricular heart disease in children with Down's syndrome: A systematic review

Objectives

No standard protocol is available for the management of children with Down's syndrome (DS) and a functional single ventricle. This review attempts to determine the outcomes of the single ventricular surgical palliation pathway in high-risk children with DS.

Methods

Several databases were searched using the following MeSH terms: ‘Congenital heart disease’, ‘Atrioventricular septal defect’, ‘Balanced AVSD’, ‘Unbalanced AVSD’, ‘Down's syndrome’, ‘Univentricular repair’, ‘bidirectional Glenn procedure’, and ‘Fontan procedure’. A structured algorithm was used for the selection of studies for an in-depth analysis.

Results

There was no universal agreement on the best surgical approach for unbalanced atrioventricular septal defect in DS. The majority of paediatric cardiac surgeons did not recommend the complete Fontan procedure; conversely, the use of a Glenn shunt (superior cavopulmonary connection) was preferred.

Conclusions

Careful assessment of the suitability for Fontan surgery, including the absence of elevated pulmonary vascular resistance, pulmonary arterial anatomy, and function of the dominant ventricle, is mandatory. A staged surgical procedure ending with complete Fontan repair provides acceptable medium-term results.

Metabolic Response of the Immature Right Ventricle to Acute Pressure Overloading

BACKGROUND

Surgical palliation or repair of complex congenital heart disease in early infancy can produce right ventricular (RV) pressure overload, often leading to acute hemodynamic decompensation. The mechanisms causing this acute RV dysfunction remain unclear. We tested the hypothesis that the immature right ventricle lacks the ability to modify substrate metabolism in order to meet increased energy demands induced by acute pressure overloading.

METHODS AND RESULTS

Twenty-two infant male mixed breed Yorkshire piglets were randomized to a sham operation (Control) or pulmonary artery banding yielding >2-fold elevation over baseline RV systolic pressure. We used carbon 13 (¹³C)-labeled substrates and proton nuclear magnetic resonance to assess RV energy metabolism. [Phosphocreatine]/[ATP] was significantly lower after pulmonary artery banding. [Phosphocreatine]/[ATP] inversely correlated with energy demand indexed by maximal sustained RV systolic pressure/left ventricular systolic pressure. Fractional contributions of fatty acids to citric acid cycle were significantly lower in the pulmonary artery banding group than in the Control group (medium-chain fatty acids; 14.5±1.6 versus 8.2±1.0%, long-chain fatty acids; 9.3±1.5 versus 5.1±1.1%). ¹³C-flux analysis showed that flux via pyruvate decarboxylation did not increase during RV pressure overloading.

CONCLUSIONS

Acute RV pressure overload yielded a decrease in [phosphocreatine]/[ATP] ratio, implying that ATP production did not balance the increasing ATP requirement. Relative fatty acids oxidation decreased without a reciprocal increase in pyruvate decarboxylation. The data imply that RV inability to adjust substrate oxidation contributes to energy imbalance, and potentially to contractile failure. The data suggest that interventions directed at increasing RV pyruvate decarboxylation flux could ameliorate contractile dysfunction associated with acute pressure overloading.

Heart failure after the Norwood procedure: An analysis of the Single Ventricle Reconstruction Trial

BACKGROUND

Heart failure results in significant morbidity and mortality in young children with hypoplastic left heart syndrome (HLHS) after the Norwood procedure.

METHODS

We studied subjects enrolled in the prospective Single Ventricle Reconstruction (SVR) Trial who survived to hospital discharge after a Norwood operation and were followed up to age 6 years. The primary outcome was heart failure, defined as heart transplant listing after Norwood hospitalization, death attributable to heart failure, or symptomatic heart failure (New York Heart Association [NYHA] Class IV). Multivariate modeling was undertaken using Cox regression methodology to determine variables associated with heart failure.

RESULTS

Of the 461 subjects discharged home following a Norwood procedure, 66 (14.3%) met the criteria for heart failure. Among these, 15 died from heart failure, 39 were listed for transplant (22 had a transplant, 12 died after listing, and 5 were alive and not yet transplanted), and 12 had NYHA Class IV heart failure but were never listed. The median age at heart failure identification was 1.28 (interquartile range 0.30 to 4.69) years. Factors associated with early heart failure included post-Norwood lower fractional area change, need for extracorporeal membrane oxygenation, non-Hispanic ethnicity, Norwood perfusion type, and total support time (p < 0.05).

CONCLUSIONS

By 6 years of age, heart failure developed in nearly 15% of children after the Norwood procedure. Although transplant listing was common, many patients died from heart failure before receiving a transplant or without being listed. Shunt type did not impact the risk of developing heart failure.

Current Readings on Surgery for the Neonate With Hypoplastic Aortic Arch

Aortic arch hypoplasia is commonly present in neonates born with ductal-dependent coarctation of the aorta. The ideal surgical repair of neonates with proximal arch hypoplasia continues to be debated. Controversy exists about the fate of the hypoplastic proximal aortic arch following surgical repair and whether that will eventually grow to normal size upon relief of the distal obstruction or will persist as a residual lesion that can affect the long-term outlook of those patients. There is new evidence that residual proximal arch hypoplasia and the shape of the reconstructed arch both have an important impact on vascular remodeling and on the subsequent development of hypertension. Those concerns about late outcomes despite what was originally deemed a successful repair in infancy, coupled with improved cardiopulmonary bypass and cerebral perfusion techniques that allow surgeons to address proximal arch hypoplasia with low morbidity, have rekindled the debate on how to address proximal arch hypoplasia, with the aim to offer a neonatal surgery that would last for a lifetime and provide both optimal early recovery and late freedom from hypertension and related complications.