Rationale and design of the RISC trial: a multicenter RCT to assess in hospital 24 hour observation with telemetry of syncope patients admitted to the cardiac emergency room and emergency department

Abstract Background Half of the population succumbs to syncope in their lifetime, entailing up to three percent of ED presentations and accumulating to over 11 thousand euros per patient in healthcare costs. Syncope has a broad differential diagnosis making management a multidisciplinary effort, causing a non-standardized approach across healthcare providers and disciplines. ESC guidelines on syncope recommend to apply the ESC diagnostic syncope algorithm to identify and discharge syncope patients with low and intermediate risk of severe underlying illness (~70 percent of patients). Although the safety regarding false low/intermediate risk diagnoses has been verified in the Synergy trial, the optimal time window when to discharge these patients is not defined in the guidelines. In current medical practice low and intermediate risk syncope patients are either immediately discharged or admitted for 24 hour in-hospital rhythm monitoring (43% of low risk patients). To our knowledge, there is not sufficient scientific basis for superiority of either. This results in unstandardized and possibly unnecessary admission of patients. The current study (RISC) aims to resolve this knowledge gap. Study Design The RISC trial is an investigator-initiated multicenter prospective randomized controlled trial, comparing immediate discharge to discharge after 24 hour in-hospital rhythm monitoring (telemetry). All patients with low and intermediate risk syncope, as defined by the guideline-based syncope algorithm, are included. A total of 640 patients are randomized to either immediate discharge or discharge after 24 hour in-hospital rhythm monitoring (1:1). A power analysis has been performed to ensure enough power to claim noninferiority of immediate discharge with respect to the (non-)fatal endpoints. For the comparison of (non-)fatal endpoints in both arms we will apply 24 hour ambulant rhythm monitoring in all patients. The ambulant rhythm monitoring is solely for the study purpose, it will not be available for clinicians at the time of monitoring and will therefore have no impact on treatment during the trial. Endpoints will entail arrhythmic disorders, syncope recurrence and (cardiovascular)death. Purpose The aim of this study is to prove non-inferiority of immediate discharge in low and intermediate risk syncope patients compared to admission with telemetry for 24 hours, resulting in lower healthcare costs. Conclusion The RISC trial is a multicenter randomized controlled trial that aims to gain scientific evidence for immediate discharge compared to discharge after 24 hour in-hospital rhythm monitoring in syncope patients with a calculated low or intermediate risk of severe underlying illness. Primary endpoints will entail arrhythmias, syncope and fatalities. This trial is registered at ClinicalTrials.gov with trial ID NCT06472375).RISC Trial Flowchart