Detection of subclinical atrial fibrillation after cryptogenic stroke using implantable cardiac monitors

Background: Implantable cardiac monitor (ICM) revealed subclinical atrial fibrillation (SCAF) in up to 30% of cryptogenic stroke (CS) patients in randomized trials. However, real world data are limited. Objectives: We investigated SCAF occurrence, treatments, clinical outcomes and predictors of SCAF in a multicenter real-world population subjected to ICM after CS. Methods: From September 2016 to November 2019, 20 Italian centers collected data of consecutive patients receiving ICM after CS and followed with remote and outpatient follow-up according to clinical practice. All device-detected AF events were confirmed by the cardiologist to diagnose SCAF. Results: ICM was implanted in 334 CS patients (mean age±SD 67.4±11.5 years, 129 (38.6%) females, 242 (76.1%) with CHA2DS2-VASC score≥4). During a follow-up of 23.6 (IQR 14.6-31.5) months, SCAF was diagnosed in 92 (27.5%) patients. First episode was asymptomatic in 81 (88.1%). SCAF daily burden ≥5 minutes was 22.0%, 24.1% and 31.5% at 6, 12, and 24 months after ICM implantation. Median time to first day with AF was 60 (IQR 18-140) days. Female gender, age>69 years, PR interval>160 ms and cortical-subcortical infarct type at enrolment were independently associated with an increased risk of SCAF. Conclusions: In a real-world population, ICM detected SCAF in more than a quarter of CS patients. This experience confirms the relevance of implanting CS patients, for maximizing the possibilities to detect AF, following failure of Holter monitoring, according to guidelines. However, there is need to demonstrate that shift to oral anticoagulation following SCAF detection is associated with reduced risk of recurrent stroke.