Perspective:

The following are 10 points to remember from this review article on occult paroxysmal atrial fibrillation (AF) in cryptogenic stroke:

1. In studies that have used predominantly automatic event recorders or implantable loop recorders, approximately 6% of patients who presented with a stroke or transient ischemic attack were found to have previously undiagnosed AF.

2. In studies restricted to patients with cryptogenic stroke, the incidence of AF discovered by prolonged monitoring was 14-27%.

3. Patients with AF more often have severe neurological deficits compared to patients without AF.

4. Among cryptogenic strokes limited to the anterior circulation, the incidence of AF has been as high as 68%.

5. An embolic infarct pattern, age >65 years, and coronary artery disease are associated with a higher probability of finding AF by monitoring.

6. The clinical significance of brief episodes of AF discovered by interrogation of a dual-chamber pacemaker or implantable cardioverter-defibrillator (ICD) is not established.

7. In one clinical trial (MOST), atrial high-rate episodes lasting ≥5 minutes predicted a higher risk of death and nonfatal stroke.

8. In another trial (TRENDS), an AF burden >5.5 hours on any of the preceding 30 days of monitoring was associated with a 2.4%/year incidence of thromboembolism, twice the risk in patients without AF.

9. In another trial (ASSERT), an atrial high-rate episode lasting >6 minutes detected by a pacemaker or ICD was associated with a 2.5-fold increase in the risk of stroke/systemic embolism.

10. As of yet, there are no data available to guide recommendations regarding the optimal therapy of patients discovered to have very brief episodes of AF by prolonged rhythm monitoring.