Insertable Cardiac Monitors Uncover Subclinical Atrial Fibrillation in a Third of Patients With Cryptogenic Stroke

About a quarter of ischemic strokes are cryptogenic, presenting diagnostic and management challenges. Subclinical atrial fibrillation (SCAF) is thought to play a role in such cases, but it can evade detection by ECG or Holter monitoring. Now, a new large study shows that extended monitoring using insertable cardiac monitors (ICMs) can diagnose AF in patients with cryptogenic stroke, potentially improving their care.

The study was conducted in Italy over an 8-year period and published in the European Journal of Neurology. The researchers monitored 789 patients with cryptogenic stroke who received ICMs at 20 facilities, using both remote and outpatient follow-up. At baseline, the population had a mean age of 69.3 ± 11.7 years, 40.3% were female, and 79.0% had a CHA₂DS₂‑VASc score of 4 or higher.

A SCAF diagnosis was made with device-detected episodes lasting at least 5 minutes confirmed by a cardiologist. Patients were monitored for an average of 27.3 months after their index stroke. SCAF was diagnosed in 29% of patients, with a cumulative detection rate of 37% at 48 months. In 86% of cases, the episodes were asymptomatic. About 30% of those diagnosed experienced one or more days with a 24-hour SCAF burden. After diagnosis, anticoagulants were prescribed to 95.9% of patients who were not already taking them at baseline.

Independent predictors of SCAF included being female, a CHA₂DS₂‑VASc score of 5 or higher, anterior circulation stroke, location of infarct in cortical region, and age greater than 71 years.

The authors noted limitations in their study, including the absence of standardized protocols for diagnosing cryptogenic stroke and missing data on patients excluded from ICM implantation.

However, they said the findings may have important implications for patient care. Without interventions such as continuous cardiac monitoring after cryptogenic stroke, “AF may remain undetected for a long time, delaying initiation of anticoagulant or other therapies and increasing the risk of stroke recurrence,” they concluded.