Objective: To report an unusual case of atrial flutter with 1:1 atrioventricular (AV) conduction with unclear precipitating factors.

Case Report: A 67-year-old Thai male patient presented with diarrhea and palpitation. The electrocardiogram showed a rapid regular wide QRS complex tachycardia (WCT). The tachycardia was spontaneously slow down during saline infusion. The atrial flutter with 2:1 AV conduction was demonstrated. The diagnosis of regular WCT was atrial flutter with 1:1 AV conduction. The precipitating cause could not be identified. The catheter ablation was successfully performed under EnSite Precision Cardiac Mapping System. The atrial flutter was suddenly terminated during catheter ablation along cavotricuspid isthmus. The patient remained sinus rhythm after eight months.

Conclusion: The present case was an unusual case of atrial flutter with 1:1 AV conduction with unclear precipitating factors. Although some possible causes were demonstrated, clear precipitating causes in the present patient should be investigated in the future.

Keywords: Atrial flutter with 1:1 AV conduction, Catheter ablation, Regular wide QRS complex tachycardia, Supraventricular tachycardia, Ventricular tachycardia

DOI: doi.org/10.35755/jmedassocthai.2021.04.11868

Received 17 August 2020 | Revised 19 October 2020 | Accepted 20 October 2020