Low Energy Bipolar Radiofrequency Ablation Combined With a Needle Electrode Connected in a Parallel Electrical Circuit to Create an Isolated Intramyocardial Lesion.

BACKGROUND: An ideal ablation method to create lesions inside the thick myocardium has not been well established. This experimental study was performed to assess whether low energy bipolar (BIP) radiofrequency (RF) ablation combined with a needle electrode can create an isolated intramyocardial lesion with minimum risk of steam-pop. METHODS: A coronary perfused porcine myocardial segment was placed in an experimental setting, and two irrigation catheters were placed on the opposite endocardial and epicardial surfaces. An originally made plastic needle (equipped with a 3-mm electrode tip and a temperature sensor) was inserted into the middle myocardial region, approximately in line with and centered between the two ablation catheters. Cable-ends of the epicardial catheter and the plastic needle electrode were together plugged into the cutaneous electrode connector, whereas the cable-end of the endocardial catheter was plugged into the catheter connector of the generator. 10 W for either 60 or 90 s (18 applications each) was delivered simultaneously between the distal tips of the two ablation catheters and between the needle electrode and the endocardial ablation catheter. RESULTS: All 36 applications were successfully accomplished without steam-pop, and created an isolated intramyocardial lesion. Vertical/horizontal lesion diameters and maximum intramyocardial temperature were 7.3 ± 0.8/6.3 ± 0.7 mm and 87.9°C ± 6.2°C in the 60-second, and 9.1 ± 1.0/8.0 ± 1.1 mm and 95.6°C ± 4.7°C in the 90-second applications. No visual lesion was created on the myocardial surface. CONCLUSIONS: Although the present study is a first step in this ablation method, BIP ablation combined with a needle electrode may have the potential to create an isolated intramural lesion with minimum risk of steam-pop under local temperature monitoring.