Bipolar ablation for outflow tract ventricular arrhythmias: When the going gets tough, two catheters may be better than one

摘要

Radiofrequency catheter ablation (RFCA) is an effective treatment strategy for patients with symptomatic ventricular arrhythmias (VAs). Conventional RFCA involves unipolar ablation in which the radio-frequency energy current is delivered between the catheter tip and a dispersive skin electrode. Ablation lesion size with unipolar ablation depends on multiple factors such as power, temperature, impedance, duration of energy delivery, and catheter-tissue contact force but is generally limited to 5-6 mm in depth. However, the substrate for VAs may occasionally be intramural, residing deep within the myocardium, and in some cases, unipolar ablation - even sequential unipolar ablation from both sides of the intramural substrate - may be inadequate to eliminate the VA substrate. Several adjunctive methods of creating deeper lesions have been used in clinical practice, such as the use of half-normal saline as a catheter irrigant, simultaneous unipolar RFCA, bipolar RFCA, coronary venous ethanol ablation, radiofrequency needle ablation, electroporation, and noninvasive radiotherapy. With bipolar ablation, a second ablation catheter functioning as a return electrode in the circuit can be positioned opposite to the other active ablation catheter and simultaneous heating and concentrated thermal injury with radiofrequency (RF) delivery between the catheter tips can then lead to deeper, more transmural lesions.