Post-transseptal puncture re-entrant atrial tachycardia mimicking typical flutter.

This case report discusses the management of a 75-year-old man who developed an unusual type of atypical atrial flutter following a previous pulmonary vein isolation for paroxysmal atrial fibrillation. Despite a second attempt to re-isolate the pulmonary veins and performing cavotricuspid isthmus ablation (which was suspected to be part of the arrythmia circuit), the flutter continued and was converted to sinus rhythm through electrical cardioversion. A few weeks later, the patient's atrial tachycardia relapsed. Initial ablation attempts at the coronary sinus ostium were unsuccessful due to incomplete assessment of the circuit, leading to another transseptal approach. Activation mapping identified a macroreentrant circuit around the site of the first transseptal puncture, which was successfully ablated. This report highlights the risk of macroreentrant atrial tachycardias developing at transseptal puncture sites and the difficulty of diagnosing 'pseudotypical' flutters, which may appear to originate from the cavotricuspid isthmus but are in fact passively activated. The report emphasises that electrophysiologists should be aware of these factors in similar cases, especially with the growing number of left atrial procedures requiring transseptal access.