An updated systematic review of the impact of volume of surgery and specialization in Norwood procedure.

BACKGROUND

Volume-outcome relationship proposed to exist for high-risk, low-volume procedures, such as the Norwood procedure. A systematic review published in 2014 examined impacts of hospital and surgeon volume, specialization, regionalization and teaching status on the patient-related outcomes of the Norwood procedure. The aim of this systematic review was to update the 2014 work by synthesizing current evidence alongside the original review.

METHODS

We searched PubMed, Embase (Elsevier), and the Cochrane Library for peer-reviewed comparative studies published from 1 March 2013 to 30 December 2024 (date of last search) to update the original review covering database inception to March 2013. Citation chasing of relevant reports was performed on 20 March 2025. Mortality-related outcomes were defined as primary and all others as secondary. In studies on the volume-outcome relationship with categorical volume definitions, effect estimates were compared between the highest and lowest categories, as defined in each study. Risk of bias and certainty of evidence were assessed using ROBINS-E and GRADE, respectively. Data were presented in tables and synthesized narratively.

RESULTS

Eight additional studies reported in 13 publications were identified, resulting in a total of 18 studies (24 reports). Of these, 15 studies (20 reports), comprising 47 analyses, were included in the final synthesis. The reports were published between 2002 and 2025 and predominantly relied on routinely collected data from North America. Irrespective of statistical significance, 14 of 15 short-term and 4 of 5 long-term hospital-volume analyses, and 3 of 5 short-term and 3 of 3 long-term surgeon-volume analyses of mortality-related outcomes favored higher volume. Among 17 secondary outcome analyses, 14 favored higher hospital or surgeon volume. Evidence on hospital teaching status was limited to two older studies, which reported lower mortality in teaching hospitals. Overall, the certainty of evidence was rated as very low, reflecting heterogeneity in exposure definitions, reliance on routinely collected data, and limited use of analytical approaches that support causal interpretation.

CONCLUSIONS

Although most analyses favored higher hospital or surgeon volume and teaching hospital status, the very low certainty of evidence limits its ability to inform clinical practice or policy, underscoring the need for stronger methodological approaches in future research.

REGISTRATION: PROSPERO CRD42022385160.