Introduction: Long-term post-hospitalization cardiac monitoring has detected occult paroxysmal atrial fibrillation and atrial flutter (PAF) in a substantial minority of cryptogenic ischemic stroke (CIS) patients. Herein, we aim to better define the frequency and clinical significance of PAF detection using the Reveal LINQ insertable cardiac monitor in a population of CIS patients treated at a comprehensive stroke center. Methods: A retrospective consecutive series of CIS patients (n=95; mean age 65.9 years; 56.8% female) with no prior history of PAF had a LINQ placed during the index hospitalization, or soon thereafter, following a negative stroke evaluation. The study cardiac electrophysiologist confirmed the presence of PAF, and other potentially relevant cardiac arrhythmias, and the characteristics of the episodes and any changes in management were recorded. Results: PAF was detected in 22/95 patients (23.2%; atrial fibrillation (AF) 13; atrial flutter (A-flutter) 6; both 3). Median time to first episode was 26 days (range less than 1 day to 398 days). Median longest episode duration for AF was 2.4 hours (range 6 minutes to greater than 99 hours) and for A-flutter was 49 seconds (range 5 to 174 seconds). Antiplatelet therapy was switched to anticoagulation in 20/21 (95.2%) patients with known follow-up, including all newly diagnosed AF patients. Additional potentially relevant arrhythmias included sinus bradycardia (5/95; 5.3%), sinus pauses (5/95; 5.3%) and bigeminy (7/95; 7.4%). Conclusions: LINQ insertion during, or soon after, in-hospital stroke evaluation detected PAF in a substantial proportion of CIS patients with a higher frequency and earlier detection than previous studies. Most episodes were deemed clinically relevant, resulting in anticoagulation initiation in almost all patients. Long-term invasive cardiac monitoring following CIS may have important implications in terms of secondary stroke prevention and the detection of other potentially relevant arrhythmias.