Infective Endocarditis—Characteristics and Prognosis According to the Affected Valves

Background: Infective endocarditis (IE) continues to be a disease with high mortality despite medical advances. Objective: The objective of this study was to investigate the characteristics and prognosis of IE according to the affected valves. Materials and methods: This study was retrospective and single-centered, and it included 270 patients with a diagnosis of IE, for the period 2005–2021, who received treatment at the University Hospital “St. Georgi” in Plovdiv, Bulgaria. Results: Single-valve IE (SIE) was found in 82.6% (n-223), multivalvular IE (MIE) in 16.66% (n = 45) and device IE (CDRIE) in 0.74% (n = 2) of patients. The most commonly affected valve was the aortic valve, in 44.8% (n = 121). The predominant multivalvular involvement was aortic–mitral valves (AV-MV) (13.7%, n = 37). The patients with tricuspid valve (TV) IE were significantly younger, at 39 (30) years, and were more frequently male (80.8%). Mortality was higher in MIE than in SIE (31.1% vs. 23.8%) and was the highest in multivalve aortic–tricuspid (AV-TV) IE (75%). Early surgery was performed most in AV-MV IE, in 29.7% (n = 11). The Charlson comorbidity index (CCI) was significantly higher in MV 4 (4) and AV 3 (3) vs. TV IE 1 (5) (p = 0.048 and p = 0.011, respectively). Septic shock occurred most frequently in AV-TV involvement (75%; p = 0.0001). The most common causative agents were of the Staphylococcus group. Staphylococcus aureus more often affected TV alone (46.2%, n = 124) vs. AV (9.9%, n = 14; p = 0.0001) and vs. MV (22.6%, n = 17; p = 0.022); Staphylococcus coagulase-negative (CNG) was the prevalent cause of MV IE (22.7%, n = 17) vs. AV-MV (2.7%, n = 1; p = 0.007). Streptococci were represented in a low percentage and only in left-sided IE, more frequently in AV-MV (18.9%, n = 7) vs. AV (6.6%, n = 8; p = 0.025). Conclusions: The aortic valve is the most frequently affected valve, as single-valve IE or as multivalve AV-MV, with the predominant causative agents being of the Staphylococcus group. AV-TV IE has the worst prognosis, with the most common complication of septic shock and the highest in-hospital mortality.