Abstract Body (Do not enter title and authors here): Background: Infective endocarditis (IE) remains a severe condition with high morbidity and mortality. Patients with congenital heart disease (CHD) are especially vulnerable due to structural defects and repeated interventions. Despite growing literature, data comparing IE outcomes in patients with and without CHD remain limited.

Research Question: Among patients with IE, how do clinical outcomes differ between those with and without CHD?

Methods: We systematically searched PubMed, Embase, and Cochrane for studies enrolling patients with IE that compared individuals with CHD to those without CHD. Outcomes of interest included one-year mortality, in-hospital mortality, and surgical intervention. Risk ratios (RRs) with 95% confidence intervals (CIs) were pooled using a random-effects model in R software, with heterogeneity assessed via I2 statistics. P-values < 0.05 were considered statistically significant.

Results: We included six observational cohort studies comprising a total of 188,199 patients, of whom 4,913 had CHD. Among patients with CHD, 1,599 (32%) were children. In adults, one-year mortality was significantly lower in CHD patients compared to non-CHD patients (RR 0.42; 95% CI 0.34–0.53; p < 0.01). In-hospital mortality was also lower in adults with CHD (RR 0.44; 95% CI 0.39–0.50; p < 0.01), but higher in children with CHD compared to non-CHD patients (RR 1.59; 95% CI 1.08–2.32; p = 0.02). Surgical intervention was more frequent in adults with CHD (RR 1.22; 95% CI 1.08–1.37; p < 0.01).

Conclusions: CHD is associated with lower mortality and higher surgical intervention rates in adults with IE, but higher in-hospital mortality in children. These findings emphasize the need for age-specific, CHD-informed strategies in managing infective endocarditis.