BACKGROUND: We conducted a volume-outcome meta-analysis of pulmonary endarterectomy procedures for chronic thromboembolic pulmonary hypertension to objectively determine the minimum required annual case load that can define a high-volume centre. METHODS: Three electronic databases were systematically queried up to 1 May 2024. Centres were divided in volume tertiles. The primary outcomes were early mortality and long-term survival. Restricted cubic splines were used to demonstrate the volume-outcome relationship and the elbow-method was applied to define high-volume centres. Long-term survival was assessed using Cox frailty models. RESULTS: We included 51 centres (52 consecutive cohorts) and divided them into tertiles (T1: <
6 cases per year
T2: 6-15 cases per year, T3: >
15 cases per year), comprising a total 11 345 patients (mean age 52.3 years). Overall early mortality was 6.0% (T1: 11.6%
T2: 7.2%
T3: 5.2%
p<
0.001), for which a significant nonlinear volume-outcome relationship was observed (p=0.0437) with a statistically determined minimal required volume of 33 cases per year (95% CI 29-35 cases), and a modelled volume of 40 cases per year corresponding to a 5.0% mortality rate. Nevertheless, early mortality still progressively declined in higher volume centres (from 6.7% to 5.4% to 2.9% in centres performing 16-50, 51-100 and >
100 procedures annually). In addition, a significant volume effect was observed for long-term survival (adjusted hazard ratio per tertile 0.75, 95% CI 0.63-0.89
p=0.001). CONCLUSION: There is a significant association between procedural volume and early mortality in pulmonary endarterectomy. An annual procedural volume of >
33-40 cases per year may be used to define a high‑volume centre, although higher volumes still lead to progressively lower mortality rates.