Precardioversion Heart Rhythm Monitoring Using Smartphone Photoplethysmography

Importance: Scheduled cardioversion is a common and resource-intensive procedure in rhythm treatment of atrial fibrillation and atrial flutter. Cancellations of cardioversion procedures are common due to spontaneous conversion to sinus rhythm. Objective: To study the efficacy and feasibility of precardioversion rhythm monitoring using smartphone photoplethysmography compared to standard of care in scheduled cardioversion of atrial fibrillation. Design, Setting, and Participants: This randomized, single-blinded study took place at a tertiary hospital in Sweden. Adult patients (≥18 years) with persistent atrial fibrillation or flutter scheduled for cardioversion were included. Exclusion criteria were having a cardiac implantable electronic device or inability to consent or comply with study procedures. The study took place from September 2022 to February 2025. Interventions: Precardioversion ambulatory heart rhythm monitoring using smartphone photoplethysmography and reminders to support adherence to anticoagulation in the intervention group compared to standard of care (no intervention). Heart rhythm recordings were automatically transferred following recording and overread daily. A single-lead electrocardiogram recording was made simultaneous to each photoplethysmography recording for validation purposes. In case of spontaneous conversion to sinus rhythm in the intervention group, participants were contacted and cardioversion was canceled. In the control group, no further action was taken in case of rhythm conversion. Main Outcome and Measures: The primary efficacy outcome was proportion of same-day cancellations of scheduled atrial fibrillation or flutter cardioversions. Results: In total, 206 patients were randomized, with 105 participants assigned to intervention and 101 assigned to control (standard care). Three participants were excluded after randomization due to having a cardiac implantable device, leaving 104 and 99 participants for final analysis in the intervention and control group, respectively. The median (IQR) age was 69.7 (61.6-75.6) years and 149 (72.3%) were male. The participants performed 5226 heart rhythm recordings precardioversion, and the median (IQR) number of daily recordings per participant precardioversion was 2.1 (2.0-2.3). There were 4.8% (5/104) same-day cancellations of scheduled cardioversions in the intervention group compared to 23.2% (23/99) in the control group (P < .001). For same-day cancellations due to spontaneous sinus rhythm conversion, the corresponding results were 1.0% (1/104) vs 18.2% (18/99) (P < .001). Conclusions and Relevance: The results of this study suggest that precardioversion monitoring using smartphone photoplethysmography represents a highly scalable digital intervention that significantly reduced same-day cancellations. Trial Registration: ClinicalTrials.gov Identifier: NCT04300270.