The volume-outcome relation for pulmonary endarterectomy in chronic thrombo-embolic pulmonary hypertension

BACKGROUND: We conducted a volume-outcome (V-O) meta-analysis of PEA procedures for chronic thromboembolic pulmonary hypertension (CTEPH), to objectively determine the minimum required annual case load that can define a high-volume centre. METHODS: Three electronic databases were systematically queried until May 1st, 2024. Centres were divided in volume tertiles (Ts). The primary outcomes were early mortality and long-term survival. Restricted cubic splines were used to demonstrate the V-O relation, and the elbow-method was applied to define high-volume centres. Long-term survival was assessed using Cox-frailty models. RESULTS: Fifty-one centres (52 consecutive cohorts) were included and divided in tertiles (T1: <6 cases/year, T2: 6-15 cases/year, T3: >15 cases/year), comprising a total of 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 non-linear volume-outcome relation was observed (p=0.0437) with a statistically determined minimally required volume of 33 cases/year (95% confidence interval [CI] 29-35 cases), and a modelled volume of 40 cases/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 effect of volume 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 PEA. An annual procedural volume of >33-40 cases/year may define a high-volume centre, although higher volumes still lead to progressively lower mortality rates.