What are the differences in outcomes between right-sided active infective endocarditis with and without left-sided infection?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: in patients with isolated right-sided infective endocarditis (RSE) is the outcome of surgical management the same as in patients with or without left-sided involvement? Altogether, 419 papers were found using the reported search, six of which represented the best evidence to answer the clinical question. Two studies point towards better outcomes with isolated RSE. In one paper, mortality was significantly lower in isolated RSE patients (P = 0.0093) for the duration of the follow-up time (median 488 patient-years). Two studies reported early mortality (<30 days) for RSE patients at 3.6 and 3.8%, respectively. Combined right- and left-sided endocarditis (RLSE) patients were found to have a poorer pre-operative clinical presentation than isolated RSE patients with a greater requirement for inotropic support (P < 0.006) and the likelihood of an emergency operation (P < 0.001). They had a poorer intra-operative course with a higher incidence of cardiac abscess formation (P < 0.001). One study suggested that there is no significant difference in in-hospital and long-term mortality between intravenous drug abuse (IVDA) patients and non-IVDA patients. Left-heart involvement in the IVDA group was 61.5%. This was in-line with the published literature, demonstrating a rise in RLSE in IVDA compared with non-IVDA patients. Three articles looking at isolated left-sided endocarditis (LSE) gave mortality rates in the surgical group to be 27.1, 27.8 and 38%, respectively. In one study, the LSE mortality was not different for native vs. prosthetic valve infection (OR 0.65, 95% CI 0.23-1.87). After propensity matching and adjusting for hazards, the complication rate in the LSE group was higher and this translated to a higher mortality rate. We conclude from the literature that outcomes are more favourable with lower early and late mortality for isolated RSE patients over pure LSE or combined RLSE.