Characteristics and outcomes of patients with possible versus definite infective endocarditis: A nationwide cohort study from the NIDUS Database

BACKGROUND: Distinguishing possible from definite infective endocarditis (IE) is challenging and may affect clinical decisions. A better understanding of how possible and definite IE differ, according to the ESC Duke criteria, may clarify the clinical relevance of this distinction. PURPOSE: To compare clinical characteristics and outcomes in patients with possible and definite IE. METHODS: We included all patients with a first episode of possible or definite left-sided IE from the NatIonal Danish endocarditis stUdieS (NIDUS) registry (2016-2021), classified according to the 2015 ESC modified Duke criteria. We assessed baseline characteristics and management, as well as six-month rates of IE-related outcomes and all-cause mortality. RESULTS: Among 3,017 patients, 587 (19.5%) had possible IE and 2,430 (80.5%) definite IE. Patients with possible IE were older and more often had left-sided prosthetic valves (35.4% vs. 25.8%) and culture-negative IE (30.0% vs. 2.2%), but less often vegetations >10 mm (13.6% vs. 32.8%) (all p < 0.001). Complications and cardiac surgery (10.9% vs. 24.6%) were less frequent in the possible IE group. Antibiotic treatment was shorter in possible IE (median days 37 vs. 40; p = 0.01). Six-month all-cause mortality was similar: 27.4% [95% CI: 23.8-31.1] vs. 28.1% [95% CI: 26.3-29.9], as were IE-related outcomes. CONCLUSION: Patients with possible IE more often had left-sided prosthetic valves and culture-negative IE, but less often vegetations >10 mm, complications or cardiac surgery, and received shorter antibiotic treatment. Clinical outcomes were similar. These findings highlight diagnostic challenges and the need for tailored diagnostic and treatment strategies.