Does the shunt type determine mid-term outcome after Norwood operation?

OBJECTIVES: With improved short-term outcomes the right ventricular to pulmonary artery shunt (Sano) has become the preferred pulmonary blood source in the Norwood procedure in many centres. However, most studies analysed consecutive cohorts, with a first modified Blalock-Taussig shunt (BT) followed by the Sano cohort. Besides, neither comprehensive preoperative risk analysis nor outcome beyond 1 year of age was investigated.

METHODS: This study reviews 109 neonates undergoing the Norwood procedure in the same interval between October 2002 and December 2009. The Sano (38) or BT shunt (71) was assigned according to the surgeon's preference. Two neonates subsequently underwent successful biventricular repair and were excluded. The Aristotle comprehensive score (ACS) was used to evaluate preoperative risk, with high-risk patients (n = 39) classified as having an ACS ≥ 20, and low-risk patients (n = 68) given an ACS <20.

RESULTS: Mean Aristotle score at the Norwood operation was 18.8 ± 0.4 and 18.9 ± 0.3 (P = 0.9) in Sano and BT, respectively. Mean follow-up interval was 4.1 ± 2.1 years (range: 1.7-8.9 years). Actuarial survival was similar, stabilizing from the 8th postoperative month onwards at 78.6 ± 4.9% (95% CI: 67.0-86.5%) for Sano and 78.4 ± 6.8% (95% CI: 61.4-88.6%) for BT; P = 0.95. Midterm actuarial survival was higher in low-risk patients, 88.2 ± 3.9% (95% CI: 77.8-93.9%) than in high-risk patients: 61.5 ± 7.8% (95% CI: 44.5-74.7%, P = 0.0003). No survival benefit was detected in low- or high-risk cases for either shunt type. Risk factors for midterm mortality were cardiorespiratory failure requiring ventilation (13/34, P = 0.004), and ACS ≥ 20 (15/39, P = 0.001), but not shunt type (8/37, P = 0.95). Increased number of shunt-related interventions before the Glenn procedure were noted with Sano (32.4 versus 6.5%, P = 0.002).

CONCLUSIONS: Preoperative risk factors, regardless of shunt type, influence midterm survival after the Norwood procedure with an excellent outcome in low-risk patients, while high-risk cases still incur a significant mortality. Sano shunt interventions occurred with increased numbers. Although, Sano shunt may be the only feasible option in some instances, given the possible negative effects of ventriculotomy on right ventricle function, the widespread use of Sano shunt should be reconsidered.