Over the last few decades, several infective endocarditis (IE) registries have contributed with important knowledge on the epidemiological aspects of the disease, revealing increased incidence and changes in microbiological etiology.1, 2, 3, 4, 5, 6, 7, 8, 9, 10 The incidence of IE is estimated at 3.0-10.5 per 100.000 person years annually.11, 12, 13, 14, 15 Mortality remains high and almost unchanged over the last few decades.16,17 Multinational IE registries, such as the International Collaboration on Endocarditis (ICE)3,4 and the European Society of Cardiology (ESC) EUROpean ENDOcarditis (EURO-ENDO),1 have set the international standard of reporting epidemiological aspects of the disease for many years, but both registries are limited by selection bias.18 In previous IE cohorts, patients were predominantly included at tertiary centers, and data completeness varied substantially among the participating countries because of the limited possibility of follow-up of IE patients after hospital discharge.

Selection bias is evident in the significant disparity observed in the reporting of key measures, such as surgery. Several studies report the occurrence of surgical intervention in 40-50% of IE patients,2,19, 20, 21 yet studies from national observational studies have demonstrated significantly lower rates approximating 20%.12,22 The primary explanation is related to patient selection and reporting.18 To date, no registries to our knowledge have managed to conduct a nationwide consecutive study. Much of our current knowledge on IE is based on selected cohorts lacking key measurements such as the diagnostic criteria of IE, echocardiographic data, vegetation size and location, complications caused by IE, microbiological data, surgical treatment, antibiotic therapy, and Positron Emission Tomography/ computer tomography (PET/CT) imaging, thus limiting population-based studies in the characterization and assessment of potential risk factors for the disease.11,12,14,15,23, 24, 25

To address these limitations in the IE literature and to offer detailed individual data, our objective is to establish a comprehensive, national, and contemporary IE registry. This registry validates the diagnosis of IE based on the ESC 2015 diagnostic criteria and minimize the loss of patient follow-up in the administrative registries. We will include all available data on patient characteristics, management, and clinical outcomes including mortality, infection relapse, morbidity, activities of daily living after discharge, imaging, surgery, microbiological etiology, and antibiotic regimens during admission. The hypothesis is that the NIDUS study will prospectively provide robust and contemporary information on patient characteristics, treatment, disease courses and short and long-term outcomes of IE in a nationwide consecutive complete cohort of IE patients.

Here, we describe the design and potential use of the NIDUS registry.