Intramuscular Penicillin Prophylaxis and Valve Progression in Adults with Mild Rheumatic Heart Disease: a Propensity Score-Matched Cohort Study

BACKGROUND:Evidence supporting intramuscular penicillin prophylaxis in rheumatic heart disease (RHD) is largely derived from paediatric populations, and its role in adults with mild disease remains unclear. We aimed to evaluate its impact on valve progression in adults with early-stage RHD. METHODS:This retrospective cohort study included 312 adults with World Heart Federation (WHF) Stage A or B RHD. Patients were stratified according to receipt of intramuscular penicillin prophylaxis. The primary outcome was a composite of valve progression or new valve disease. Baseline imbalances were assessed using standardised mean differences (SMD), and propensity score matching (1:1) was applied. Outcomes were compared using relative risks (RR), and time-to-event analysis was performed using Kaplan-Meier estimates. RESULTS:Over a follow-up period of 8-12 years (median 10.1 years), event rates were low. Valve progression occurred in 2.0% of patients without prophylaxis and in 1.7% of patients with prophylaxis (RR 0.84; 95% CI 0.16-4.54; p = 1.000). New valve disease developed in 2.0% and 2.6% of patients, respectively (RR 1.27; 95% CI 0.29-5.56; p = 0.714). The composite outcome occurred in 4.1% of the no-prophylaxis group and 4.3% of the prophylaxis group (RR 1.06; 95% CI 0.35-3.15; p = 1.000). After propensity score matching (n = 116 per group), baseline characteristics were well balanced across all covariates, and prophylaxis was not associated with the composite outcome (OR 0.70; 95% CI 0.22-2.28; p = 0.555). CONCLUSION:In adults with mild RHD, intramuscular penicillin prophylaxis was not associated with reduced valve progression or new valve disease. Careful clinical and echocardiographic follow-up may be a reasonable strategy in selected patients.