Impact of valve location and type on mortality in left-sided infective endocarditis

Introduction and Objectives The location and nature of the valve involved in Infective Endocarditis (IE) can lead to different intracardiac complications, which may influence the clinical course and prognosis of the disease. Our objective was to compare clinical characteristics, complications, and mortality between mitral (MV) and aortic valve (AV) endocarditis based on valve type (native or prosthetic). Materials and Methods Single-center retrospective registry. We performed multivariable logistic regression models adjusted for age and sex, with statistical significance set at p<0.05. Results A total of 234 patients were analyzed, 192 of whom had isolated left-sided valve involvement (77 MV, 115 AV), admitted between 2016 and 2024. Median age was similar (MV: 67 years [IQR 68], AV: 69 years [IQR 54]), although AV endocarditis was more frequent in patients under 60 (32.5% vs. 20%, p=0.05). No significant differences in baseline comorbidities were found. The most frequent complications were chordae rupture in MV cases (16.9%) and cardiac abscess in AV cases (27.8%). MV endocarditis was more common on native valves (75.3%, p=0.001), whereas AV endocarditis affected native (48.7%) and prosthetic (51.3%) valves similarly. Mechanical prostheses were more frequent in the mitral position, and bioprosthetic (including TAVI) in the aortic position (p<0.001). No statistically significant differences were observed in surgical intervention rates (MV 40%, AV 52%, p=0.1), cardiovascular mortality (MV 37.6% vs. AV 30.4%, p=0.5), or all-cause mortality (46.7% vs. 36.5%, p=0.15). In the analysis by valve type, cardiovascular mortality was lower in AV endocarditis on native valves (20%) compared to prosthetic valves (early 45%, late 39%, p=0.042), a difference not seen in MV cases (p=0.52). In adjusted multivariable models, prosthesis type and its interaction with valve location did not significantly impact mortality; age remained the only independent predictor (OR ≈ 1.06 per year, p<0.001). Conclusions Although clinical characteristics differ between mitral and aortic endocarditis, overall mortality is similar. Aortic endocarditis on native valves is associated with lower mortality compared to prosthetic valves, a difference not observed in mitral cases. However, prosthesis type does not independently modify mortality risk.