Optimal Timing of Stage 2 for Hypoplastic Left Heart Syndrome

Study Questions:

What are the clinical factors associated with the timing of stage-2-palliation (S2P) and the optimal timing of S2P that both minimizes pre-S2P attrition and maximizes post-S2P survival?

Methods:

The investigators used the National Institutes of Health/National Heart, Lung, and Blood Institute Pediatric Heart Network Single Ventricle Reconstruction Trial public dataset for this analysis. Transplant-free survival (TFS) was modeled from: 1) Norwood procedure to S2P, and 2) S2P to 3 years, using parametric hazard analysis. Factors associated with death or heart transplantation were determined for each interval. To account for staged procedures, risk-adjusted, 3-year, post-Norwood TFS (the probability of TFS at 3 years given survival to S2P) was calculated using parametric conditional survival analysis. TFS from the Norwood to S2P was first predicted. TFS after S2P to 3 years was then predicted and adjusted for attrition before S2P by multiplying by the estimate of TFS to S2P. The optimal timing of S2P was determined by generating nomograms of risk-adjusted, 3-year, post-Norwood TFS versus the interval from the Norwood to S2P.

Results:

Of 547 included patients, 399 survived to S2P (73%). Of the survivors to S2P, 349 (87%) survived to 3-year follow-up. The median interval from the Norwood to S2P was 5.1 (interquartile range, 4.1-6.0) months. The risk-adjusted, 3-year TFS was 68 ± 7%. A Norwood-S2P interval of 3-6 months was associated with greatest 3-year TFS overall and in patients with few risk factors. In patients with multiple risk factors, TFS was severely compromised, regardless of the timing of S2P and most severely when S2P was performed early. No difference in the optimal timing of S2P existed when stratified by shunt type.

Conclusions:

The authors concluded that in infants with few risk factors, progressing to S2P at 3-6 months after the Norwood procedure was associated with maximal transplant-free survival.

Perspective:

This study reports that a shorter Norwood-S2P interval was associated with an increased risk for death or heart transplantation after S2P. Furthermore, in low- or average-risk patients, an interval of 3-6 months after the Norwood was associated with maximal calculated transplant-free survival at 3 years post-Norwood. However, in high-risk patients, 3-year transplant-free survival was substantially compromised, regardless of the timing of S2P or shunt type. It seems that flexibility and perspective are needed when managing individual infants with hypoplastic left heart syndrome given that the interval period may necessitate additional procedures and hospitalizations, which may affect the timing of S2P.


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