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Background Valvular heart disease (VHD) is a major cause of cardiovascular morbidity and mortality worldwide. The impact of environmental stress on the prognosis of patients with VHD is unknown. This study aims to explore the impact of ambient air pollution exposure on the clinical outcomes of patients with VHD.Methods Data were derived from the China-VHD registry, a national multicentre prospective cohort study. Monthly ambient particulate matter with a diameter <2.5 μm (PM 2.5) exposure was derived from the ChinaHighAirPollutants (CHAP) dataset at 1×1 km resolution. Using residential address, clinical data from patients diagnosed with VHD between April and June 2018 were linked to ambient PM2.5 exposure concentrations. Patients were followed up until they lost or experienced the primary outcome (defined as all-cause mortality or heart failure hospitalisation) for 2 years. Time-varying Cox proportional hazards regression models were applied to evaluate the association between monthly ambient PM2.5 exposure and outcomes.Results A total of 12 258 VHD patients were included. Mean age at enrolment was 61.2±13.7 years, and 54.7% were male. Mean baseline ambient PM 2.5 exposure was 43.50±12.25 µg/m3. After 2 years of follow-up, 1577 patients (12.9%) experienced the primary outcome. The estimated HR for all-cause mortality or heart failure hospitalisation was 1.24 (95% CI 1.07 to 1.43) for individuals in the highest tertile of monthly ambient PM2.5 exposure compared with those in the lowest tertile. Each IQR (21.80 µg/m³) increase in monthly ambient PM2.5 exposure was associated with a 1.11-fold higher risk of the primary outcome (95% CI 1.04 to 1.18). This association was consistent across subgroups.Conclusions Exposure to air pollution was associated with adverse outcomes in patients with VHD. These findings highlight the potential role of a key environmental factor in the progression and prognosis of VHD.Trial registration number NCT03484806.