Predictors of death after receiving a modified Blalock-Taussig shunt in cyanotic heart children: A competing risk analysis

OBJECTIVE: To determine risk factors affecting time-to-death ≤90 and >90 days in children who underwent a modified Blalock-Taussig shunt (MBTS).

METHODS: Data from a retrospective cohort study were obtained from children aged 0-3 years who experienced MBTS between 2005 and 2016. Time-to-death (prior to Glenn/repair), time-to-alive up until December 2017 without repair, and time-to-progression to Glenn/repair following MBTS were presented using competing risks survival analysis. Demographic, surgical and anesthesia-related factors were recorded. Time-to-death ≤90 days and >90 days was analyzed using multivariate time-dependent Cox regression models to identify independent predictors and presented by adjusted hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS: Of 380 children, 119 died, 122 survived and 139 progressed to Glenn/repair. Time-to-death probability (95% CI) within 90 days was 0.18 (0.14-0.22). Predictors of time-to-death ≤90 days (n = 63) were low weight (<3 kg) (HR 7.6, 95% CI:2.8-20.4), preoperative ventilator support (HR 2.7, 95% CI:1.3-5.6), postoperative shunt thrombosis (HR 5.0, 95% CI:2.4-10.4), bleeding (HR 4.5, 95% CI:2.1-9.4) and renal failure (HR 4.1, 95% CI:1.5-10.9). Predictors of time-to-death >90 days (n = 56) were children diagnosed with pulmonary atresia with ventricular septal defect and single ventricle (compared to tetralogy of fallot) (HR 3.2, 95% CI:1.2-7.7 and HR 3.1, 95% CI:1.3-7.6, respectively), shunt size/weight ratio >1.1 vs <0.65 (HR 6.8, 95% CI:1.4-32.6) and longer duration of mechanical ventilator (HR 1.002, 95% CI:1.001-1.004). Shunt size/weight ratio ≥1.0 (vs <1.0) and ≥0.65 (vs <0.65) were predictors for overall time-to-death in neonates and toddlers, respectively (HR 13.1, 95% CI:2.8-61.4 and HR 7.8, 95% CI:1.7-34.8, respectively).

CONCLUSIONS: Perioperative factors were associated with time-to-death ≤90 days, whereas particular cardiac defect, larger shunt size/weight ratio, and longer mechanical ventilation were associated with time-to-death >90 days after receiving MBTS. Larger shunt size/weight ratio should be reevaluated within 90 days to minimize the risk of shunt over flow.