Ultra‐Early Continuous ECG Monitoring for Silent Atrial Fibrillation Diagnosis in Cryptogenic Stroke: The CRIPTOFAST Randomized Controlled Trial

BACKGROUND: Cryptogenic strokes (CS) represent one third of admissions for stroke. Silent paroxysmal atrial fibrillation (PAF) is the underlying cause of a significant proportion of cases. The use of internal loop recorders (ILR) after CS has shown controversial results, remaining unclear in guidelines. Subtle ultrasound left atrium (LA) anomalies may help select patients more prone to suffer from silent PAF who can benefit from an ILR. METHODS: Randomized, controlled, parallel-arm, open-label trial of patients with CS. We evaluated the efficacy of early ILR for detection of silent PAF episodes compared to standard care. Clinical/ultrasound predictors of PAF were studied. The presence of subtle LA anomalies (any of: LA dilatation, maximum systolic global longitudinal strain < 21%, atrial contraction strain < 13%, atrial ejection fraction < 55%) was used in a pre-specified subgroup analysis. RESULTS: Fifty-nine CS patients were included (52.5% to ILR and 47.5% to standard care). There were no statistically significant differences among groups regarding baseline characteristics. Median follow-up was 377 days. The diagnosis of silent PAF was made in 43.3% in the ILR group compared to 7.1% in the control group (HR 7.47, 95% CI 1.68-31.19, p = 0.008). Most PAF events were detected in the 100 days following ILR implantation. In patients with normal LA, PAF was observed in 23% versus 7%, while in patients with abnormal LA, PAF was diagnosed in 58.8% versus 7.7%. CONCLUSIONS: An ILR implanted early after CS improves the detection of PAF compared to standard care. Individuals with abnormal LA features may benefit the most from ILR.