Chaisinanunkul, Napasri

Introduction: Long-term cardiac monitoring studies have unveiled low-burden, occult atrial fibrillation (AF) in some patients with otherwise cryptogenic stroke (CS). But occult AF is also found in some normal individuals and patients with stroke of known cause (KS). Clinical management would be aided by estimates of how often occult AF in a patient with CS is causal versus incidental. Methods: Through systematic search, we identified all case-control and cohort studies applying identical long-term monitoring techniques to both CS and KS patients. We performed a random-effects meta-analyses across these studies to determine the best estimate of the differential frequency of occult AF in CS and KS among all patients, and across age subgroups. We then applied Bayes’ theorem (method of Alsheikh-Ali et al, Stroke 2009) to determine the probability that occult AF is causal or incidental. Results: The systematic search identified 3 case-control and cohort studies enrolling 575 patients (337 CS, 238 KS). Methods of long-term monitoring were implantable loop recorder in 191 (33.2%), extended mobile external cardiac monitor in 277 (48.2%), and patch/event/Holter monitoring in 107 (18.6%). In formal meta-analysis, the summary odds ratio for occult AF in CS vs KS in all patients was 1.72 (95%CI 0.91-3.25) (Figure). With application of Bayes theorem, the corresponding probabilities indicated that, when present, occult AF in CS patients is causal in 44.4% and incidental in 55.6%. Only one study reported age-specific subgroup data: these suggested occult AF in CS patients was causal in 93% of patients <65y vs 5.6% of patients ≥65y, but estimates had limited precision. Conclusions: In patients with cryptogenic stroke, when occult AF is found, it is likely causal in about 44% of patients, who may benefit from anticoagulation, and likely incidental in about 56% of patients, who may not benefit from anticoagulation. Figure