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Detection of Undiagnosed AF Using Insertable Cardiac Monitors
Study Questions:
What is the incidence of atrial fibrillation (AF) in patients at high risk for, but without previously known AF, using an insertable cardiac monitor?
Methods:
The REVEAL AF investigators conducted a prospective, single-arm, multicenter study from November 2012 to January 2017. Visits took place at 57 centers in the United States and Europe. Patients with a CHADS2 score of ≥3 (or 2 with at least one additional risk factor) were enrolled. Approximately 90% had nonspecific symptoms potentially compatible with AF, such as fatigue, dyspnea, and/or palpitations. Patients underwent monitoring with an insertable cardiac monitor for 18-30 months. The primary endpoint was adjudicated AF lasting ≥6 minutes and was assessed at 18 months. Other analyses included detection rates at points from 30 days to 30 months and among CHADS2 score subgroups. Median time from insertion to detection and the percentage of patients subsequently prescribed oral anticoagulation therapy was also determined. A Cox proportional hazards model was used to identify predictors of AF, while log-rank tests were used to compare AF incidence among CHADS2 score subgroups and subgroups defined by presence of baseline symptoms, such as palpitations.
Results:
A total of 446 patients were enrolled; 233 (52.2%) were male, and the mean (standard deviation [SD]) age was 71.5 (9.9) years. A total of 385 patients (86.3%) received an insertable cardiac monitor, met the primary analysis cohort definition, and were observed for a mean (SD) period of 22.5 (7.7) months. The detection rate of AF lasting ≥6 minutes at 18 months was 29.3%. Detection rates at 30 days and 6, 12, 24, and 30 months were 6.2%, 20.4%, 27.1%, 33.6%, and 40.0%, respectively. At 18 months, AF incidence was similar among patients with CHADS2 scores of 2 (24.7%; 95% CI, 17.3-31.4), 3 (32.7%; 95% CI, 23.8-40.7), and ≥4 (31.7%; 95% CI, 22.0-40.3) (p = 0.23). Median (interquartile) time from device insertion to first AF episode detection was 123 (41-330) days. Of patients meeting the primary endpoint, 13 (10.2%) had ≥1 episode lasting ≥24 hours, and oral anticoagulation therapy was prescribed for 72 patients (56.3%).
Conclusions:
The authors concluded that incidence of previously undiagnosed AF may be substantial in patients with risk factors for AF and stroke.
Perspective:
This study reports a substantial incidence of previously undiagnosed AF (~30%) at 18 months of follow-up in patients at high risk of both AF and stroke. By 30 months, the detection rate had increased to 40%. With a median time to AF detection of 123 days, it appears that most patients would not have been identified with shorter duration monitoring typical of external devices. Previous long-term monitoring studies have suggested that patients with short episodes of subclinical AF have a lower risk of stroke compared with traditional clinical AF, which raises important questions about the risk-benefit ratio of anticoagulation in this setting. Importantly, only 13 patients (10.2%) in the REVEAL AF trial had AF that lasted >24 hours, a duration associated with a substantial increase in the risk of stroke. Additional studies to assess whether insertable cardiac monitor-based screening for AF may actually reduce stroke and be cost-effective for stroke prevention in specific patient populations are indicated.
Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, Defibrillators, Implantable, Dyspnea, ESC Congress, ESC2017, Risk Assessment, Risk Factors, Secondary Prevention, Stroke, Vascular Diseases
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