Background: Afib is often asymptomatic until a patient presents with an acute stroke. Current screening strategies for Afib fail to detect a large portion of patients, especially since most Afib is paroxysmal. Better screening strategies that increase diagnostic yield are needed.
Study design: Randomized controlled trial (part of the LOOP trial).
Setting: Four centers in Denmark.
Synopsis: Patients over the age of 70 years, with at least one stroke risk factor, were monitored over the course of 3 years using an implantable loop recorder to obtain complete heart rhythm histories and to monitor for the development of Afib. Researchers then applied different sampling strategies to simulate different Afib screening scenarios on this set of rhythm data. A single 10-second EKG yielded a sensitivity of 1.5% for Afib detection and a negative predictive value (NPV) of 66%, increasing to 2.3% and 71% for annual EKGs during 3 years. Twice-daily 30-second EKGs during 14 consecutive days yielded a sensitivity of 8.3%, while a single 24-h monitoring yielded a sensitivity of 11%, increasing to 13%, 15%, and 21% for a 48-hour, 72-hour, and 7-day monitoring, respectively. The highest performance was achieved with annual 30-day monitoring which had a sensitivity of 34%-55% and a NPV of 74%-84% over 1-3 years.
The authors acknowledged many limitations including: The algorithm used had a sensitivity of 95%, there is no valid cutoffs for time-in-Afib, and the simulations assumed 100% patient compliance.
Bottom line: Screening for atrial fibrillation improves by increasing the duration of, spacing between, and number of screenings.
Citation: Diederichsen SZ et al. Comprehensive evaluation of rhythm monitoring strategies in screening for atrial fibrillation: Insights from patients at risk long-term monitored with implantable loop recorder. Circulation. 2020 May 12;141(19):1510-22.
Dr. Mastbergen is a hospitalist and assistant professor of medicine at UK HealthCare, Lexington, Ky.