Abstract: Para-Hissian atrial tachycardia (PHAT) is rare,being also a diagnostic and therapeutic challenge in the electrophysiology laboratory. The anatomical proximity to the His-Purkinje system makes ablation of PHAT limited by the risk of atrioventricular block. However, the use of retroaortic access with the ablation catheter positioned on the non-coronary cusp, which is anatomically contiguous to the para-Hissian region, is a possible strategy for mapping and ablation of suchtachycardias.
Objectives: To describe the outcome and safety of this strategy in the treatment of patients with PHAT.
Methods: Eight patients (mean age: 36±10 years) were referred for ablation due to paroxysmal supraventricular tachycardia, and all of them were diagnosed with focal atrial tachycardia confirmed by the classical electrophysiological maneuvers. The P wave in the electrocardiogram demonstrated V1 (-/+), D1 and AVL+, and an early transition in the horizontal plane. The earliest atrial activation was found during mapping the right atrium, in a region where the Hiss potential was observed(close to the Koch triangle apex), precociously relative to the P wave (ECG: 28±12 ms). Mapping of the non-coronary cusp through retroaortic access revealed precocity (3±2 ms) relative to the catheter positioned close to the His bundle, but without evidence of a Hiss potential in this region in all patients. Application of radio frequency (RF) on the non-coronary cusp (4-mm catheter; power: 30 W; temperature: 55 °C), interrupted tachycardia for 5±3 s, and increase in the PR interval or junctional rhythm was not observed during RF application (duration: 60 s). Electrophysiological tests did not re-induced tachycardia. Complication did not occur in any patient. In the follow up for 14±3 months, one patient presented tachycardia recurrence, and the others remained asymptomatic.
Conclusions: Ablation of para-Hissian atrial tachycardia through the non-coronary cusp is an effective and safe strategy, can be an option for electrophysiologistsfor the treatment of this complex arrhythmia.