Demonstration of our underlying composite method to detect atrial fibrillation/atrial tachycardia recurrence by utilizing matching onset and offset for heart rate delta change (spike score) and subsequent arrhythmia recurrence as detected by implantable loop recorder. A normalized spike score ≥ 0.75 for both onset and offset of tachycardia is more likely to represent an episode of atrial arrhythmia recurrence due to a sudden increase in heart rate rather than exercise induced tachycardia with a gradual increase in heart rate. LoTO in CASA LSPAF, long-term outcomes in long-standing persistent atrial fibrillation RCT (ClinicalTrials.gov Identifier: NCT04280042). ILR, implantable loop recorder.