ICM-detected AF not tied to recurrent ischemic stroke in already fairly anticoagulated population

The findings published in the Journal of the American Heart Association suggested a similar risk of recurrent stroke in cryptogenic stroke survivors who went on to get an ICM whether or not any AF ever turned up on monitoring.

"Ischemic stroke recurred in a similar 4.0% of Japanese patients without atrial fibrillation detected and 5.8% of those who did have AF detected during nearly two years of monitoring after their index stroke (OR 1.47), the researchers reported.

Likewise, the stroke risk was not higher immediately after AF detection or within 90 days in a landmark analysis. An AF burden at or above the median of 0.1% (a low threshold) also did not appear to impact stroke recurrence rates, according to the CRYPTON-ICM registry.

Atrial fibrillation is reported to be a strong risk factor for stroke. However, there is a lack of information on the risk of stroke recurrence in patients with cryptogenic stroke with AF detected after stroke by an insertable cardiac monitor. Therefore, Kenichi Todo, Osaka University Graduate School of Medicine, Osaka, Japan, and colleagues sought to evaluate the risk of ischemic stroke recurrence in patients with cryptogenic stroke with and without ICM‐detected AF.

For this purpose, the research team retrospectively reviewed patients with cryptogenic stroke who underwent ICM implantation at eight stroke centres in Japan. Cox regression models were developed using time‐dependent analysis and landmark analysis. The target sample size was set at 300 patients based on the estimate of the annualized incidence of ischemic stroke recurrence to be 3% in patients without AF detection and 9% in patients with AF detection.

Based on the study, the following inferences were made:

· Of the 370 patients, 121 had atrial fibrillation, and 110 received anticoagulation therapy after AF detection.

· The incidence of ischemic stroke recurrence was 4.0% in 249 patients without AF detection and 5.8% in 121 patients with AF detection.

· In a landmark analysis, the risk of ischemic stroke recurrence was not higher in patients with AF detected ≤90 days than in those without (hazard ratio, 1.47).

· In a time‐dependent analysis, the risk of ischemic stroke recurrence did not increase after AF detection (hazard ratio, 1.77).

Despite the known high risk of stroke in patients with overt atrial fibrillation, the study showed that the risk of recurrent stroke in cryptogenic stroke with AF patients detected by ICM was not higher than that in patients with cryptogenic stroke without AF, possibly because of a relatively small burden of AF and appropriate initiation of anticoagulation therapy after AF detection with >90% anticoagulation rate.

"We confirmed that it is reasonable to switch from antiplatelet therapy to anticoagulation therapy after AF detection by ICM instead of empirically initiating anticoagulation therapy before AF detection in cryptogenic stroke," the researchers concluded.

Reference:

Todo K, et al "Atrial fibrillation detection and ischemic stroke recurrence in cryptogenic stroke: a retrospective, multicenter, observational study" J Am Heart Assoc 2024; DOI: 10.1161/JAHA.123.031508.