Transplant-Free Survival and Interventions at 6 Years in the SVR Trial

Abstract

Background: In the SVR trial (Single Ventricle Reconstruction), 1-year transplant-free survival was better for the Norwood procedure with right ventricle-to-pulmonary artery shunt (RVPAS) compared with a modified Blalock-Taussig shunt in patients with hypoplastic left heart and related syndromes. At 6 years, we compared transplant-free survival and other outcomes between the groups.

Methods: Medical history was collected annually using medical record review, telephone interviews, and the death index. The cohort included 549 patients randomized and treated in the SVR trial.

Results: Transplant-free survival for the RVPAS versus modified Blalock-Taussig shunt groups did not differ at 6 years (64% versus 59%, P=0.25) or with all available follow-up of 7.1±1.6 years (log-rank P=0.13). The RVPAS versus modified Blalock-Taussig shunt treatment effect had nonproportional hazards (P=0.009); the hazard ratio (HR) for death or transplant favored the RVPAS before stage II surgery (HR, 0.66; 95% confidence interval, 0.48-0.92). The effect of shunt type on death or transplant was not statistically significant between stage II to Fontan surgery (HR, 1.36; 95% confidence interval, 0.86-2.17; P=0.17) or after the Fontan procedure (HR, 0.76; 95% confidence interval, 0.33-1.74; P=0.52). By 6 years, patients with RVPAS had a higher incidence of catheter interventions (0.38 versus 0.23/patient-year, P<0.001), primarily because of more interventions between the stage II and Fontan procedures (HR, 1.72; 95% confidence interval, 1.00-3.03). Complications did not differ by shunt type; by 6 years, 1 in 5 patients had had a thrombotic event, and 1 in 6 had had seizures.

Conclusions: By 6 years, the hazards of death or transplant and catheter interventions were not different between the RVPAS versus modified Blalock-Taussig shunt groups. Children assigned to the RVPAS group had 5% higher transplant-free survival, but the difference did not reach statistical significance, and they required more catheter interventions. Both treatment groups have accrued important complications.

Clinical trial registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT00115934.

Keywords: Norwood procedure; cardiac surgery; congenital heart defect; congenital heart disease; single ventricle.

Conflict of interest statement

DISCLOSURES

No relevant conflicts to disclose.

© 2018 American Heart Association, Inc.

Figures

Figure 1

Comparison of the assigned shunt types in their freedom from the composite end point of death or cardiac transplantation (ie, transplantation-free survival). RVPAS indicates right ventricle–to–pulmonary artery shunt; and MBTS, modified Blalock-Taussig shunt.

Figure 2

Comparison of the assigned shunt types in their freedom from any catheter interventions. RVPAS indicates right ventricle–to–pulmonary artery shunt; and MBTS, modified Blalock-Taussig shunt.

Figure 3

Kaplan-Meier estimates of the proportion of patients with stroke (Panel A), 6-year incidence for RVPAS vs. MBTS, 10% vs. 7%; Thrombotic events (Panel B), 6-year incidence RVPAS vs. MBTS, 19% vs. 21%; Seizures (Panel C), 6-year incidence for RVPAS vs. MBTS, 18% vs. 15%; and PLE = protein losing enteropathy (Panel D), 6-year incidence for RVPAS vs. MBTS, 7% vs. 3%. RVPAS indicates right ventricle–to–pulmonary artery shunt; and MBTS, modified Blalock-Taussig shunt.