Inverse relationship between electrode size and lesion size during radiofrequency ablation with active electrode...

Area of Science:

• Cardiovascular Interventions
• Medical Device Technology
• Electrophysiology

Background:

• Larger radiofrequency ablation electrodes (7F, > or =4 mm) are used clinically but reduce electrogram resolution and cause variable tissue contact.
• Active cooling with saline irrigation may allow for the use of smaller ablation electrodes.

Purpose of the Study:

• To investigate the effect of irrigated electrode length on tissue temperature and lesion size during radiofrequency ablation.

Main Methods:

• 11 anesthetized dogs underwent radiofrequency ablation using a 7F catheter with 2-mm or 5-mm irrigated tip electrodes.
• Electrodes were positioned perpendicular or parallel to thigh muscle, with saline irrigation (20 mL/min) at 50 V for 30 seconds.
• Tissue temperature at 3.5 and 7 mm depths and lesion dimensions were measured.

Main Results:

• The 2-mm electrode, despite lower power output, produced higher tissue temperatures and larger lesion depths and diameters compared to the 5-mm electrode in perpendicular orientation.
• In parallel orientation, the 2-mm electrode also yielded higher temperatures and deeper lesions, with similar diameters to the 5-mm electrode.
• Lesion size showed less dependency on orientation with the smaller electrode.

Conclusions:

• Smaller irrigated electrodes transmit a greater fraction of radiofrequency power to tissue.
• This leads to increased tissue temperature and larger lesions.
• The use of smaller electrodes reduces the variability of lesion size based on electrode orientation.