Smartphone Heart Rhythm App Reduces Unnecessary Cardioversion Procedures

Atrial fibrillation, an irregular and often rapid heart rhythm, is the most common arrhythmia in adults. Elective electrical cardioversion is frequently canceled on the day of treatment when patients revert to normal rhythm unnoticed. These late changes leave allocated staff and facility resources unused and disrupt patient care. To help address this challenge, researchers have now introduced a smartphone-based home rhythm monitoring strategy to identify spontaneous conversion before admission.

The approach uses CORAI, a photoplethysmography application that analyzes fingertip pulse waves captured by a smartphone camera to assess cardiac rhythm. Developed at Karolinska Institutet, it was evaluated with Danderyd Hospital in Stockholm, Sweden. The system guides patients to perform brief recordings at home in the days leading up to planned cardioversion, enabling early identification of normal rhythm.

In a randomized clinical trial conducted from 2022 to 2025 at Danderyd Hospital, 206 patients scheduled for cardioversion were assigned to CORAI monitoring or standard care. Participants in the intervention group recorded heart rhythm twice daily for one to two weeks before the procedure. If a recording indicated normal rhythm, clinicians contacted the patient, confirmed the finding by electrocardiogram, and canceled cardioversion in advance.

The monitored group had 4.8% same-day cancellations compared with 23.2% in controls. For cancellations specifically due to spontaneous return to normal rhythm, rates were 1.0% with monitoring and 18.2% without, corresponding to a 94.7% relative risk reduction. In the control group, many patients had recordings showing normal rhythm before cardioversion, yet only three contacted their health care provider, underscoring the value of objective home data. Among participants, 99% owned a smartphone despite a median age of 70 years. Findings were published in JAMA Cardiology on June 3, 2026.

“We are pleased to see that the method could help avoid unnecessary health care visits, and that so many patients were able to record their heart rhythm independently from home using a smartphone,” said Jonatan Fernstad, a physician, engineer and researcher in cardiology at Karolinska Institutet who has developed the technology.

“Among the patients who participated in the study, 99% owned a smartphone even though the median age was 70 years. This means that smartphone-based heart rhythm diagnostics has the potential to improve access to heart rhythm assessment more generally,” said Johan Engdahl, professor of cardiology at Karolinska Institutet and senior consultant at the Department of Cardiology, Danderyd Hospital.

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