The Optimal Timing of Stage 2 Palliation for Hypoplastic Left Heart Syndrome

Abstract

Background In infants requiring three-stage single ventricle palliation for hypoplastic left heart syndrome, attrition after the Norwood procedure remains significant. The effect of the timing of stage-2-palliation (S2P), a physician-modifiable factor, on long term survival is not well understood. We hypothesized that an optimal interval between the Norwood and S2P that both minimizes pre-S2P attrition and maximizes post-S2P survival exists and is associated with individual patient characteristics. Methods The NIH/NHLBI Pediatric Heart Network Single Ventricle Reconstruction Trial public dataset was used. Transplant-free survival (TFS) was modeled from (1) Norwood to S2P and (2) S2P to three years, using parametric hazard analysis. Factors associated with death or heart transplantation were determined for each interval. To account for staged procedures, risk-adjusted, three-year, post-Norwood TFS (the probability of TFS at three 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 three 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, three-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 three-year follow-up. The median interval from the Norwood to S2P was 5.1 (IQR 4.1–6.0) months. The risk-adjusted, three-year, TFS was 68±7%. A Norwood-S2P interval of three to six months was associated with greatest three-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 In infants with few risk factors, progressing to S2P at three to six months after the Norwood procedure was associated with maximal TFS. Early S2P did not rescue patients with greater risk factor burdens. Instead, referral for heart transplantation may offer their best chance at long term survival. ClinicalTrials.gov number: NCT00115934.

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