Objective The prevalence of heart failure (HF) among adult patients with congenital heart disease (ACHD) is rising. Right ventricle (RV) exercise reserve and its relationship to outcomes have not been characterised. We aim to evaluate the prognostic impact of impaired RV reserve in an ACHD population referred for cardiopulmonary exercise testing (CPET).

Methods This retrospective study evaluates patients with ACHD who underwent CPET (n=147) with first-pass radionuclide ventriculography at a single tertiary care centre. RV reserve was categorised as normal, mild to moderately or severely impaired. The primary composite clinical outcome included clinical right HF, arrhythmia, transplantation or death.

Results Patients were median age 41±13 years, 50% were female and median follow-up was 1.1 (IQR: 0.7–2.0) years. Exercise RV reserve was impaired in 103 patients (70%), of whom 32% were asymptomatic. Resting RV systolic function poorly predicted RV reserve, with 52% of patients with severe impairment having a qualitatively normal echocardiographic assessment. The severely impaired reserve group had lower peak oxygen consumption (VO₂)(17.2 vs 22.5 mL/kg/min, p<0.0001) compared with the normal reserve group, and was more likely to develop the composite outcome (48% vs 9%, log-rank p<0.001). Severely impaired RV reserve predicted event-free survival after adjusting for peak VO₂, age, sex, RV pathology, QRS duration, New York Heart Association class, resting RV ejection fraction and RV dilation by echocardiography or MRI (HR 3.7, 95% CI 1.1 to 13.0, p=0.039).

Conclusion Impaired RV reserve, occurred in asymptomatic patients, was not well predicted by resting systolic function assessment, and strongly predicted adverse cardiovascular outcomes.