Introduction
Typical atrial flutter (AFL) is a common atrial arrhythmia that can result in significant morbidity and mortality when left untreated1, 2. Catheter ablation is a highly effective, first-line treatment for typical AFL that results in a low recurrence rate and reduction of stroke risk3, 4. Whereas ablation of the flutter circuit is indicated in patients with documented AFL, it may also be a reasonable consideration in those without a documented AFL history, but high risk of unrecognized AFL or development of AFL in future5. This may allow for attenuation of stroke risk in a group that may eventually present with thromboembolic complications as the first indication of AFL. A simple diagnostic maneuver to determine the existence of a potential AFL circuit, and therefore a risk of occult or future AFL, would be very useful. This could support the decision on whether to empirically ablate a flutter circuit at time of ablation for other rhythms, such as atrial fibrillation. We investigated right atrial collision time (RACT) during coronary sinus pacing as a surrogate marker of a potential right atrial flutter circuit, and thereby a candidate marker of occult or future AFL which may inform anticoagulation and ablation decisions.