Can an Expanding Lattice Electrode Catheter Expand Our Success in Catheter Ablation?

Efficacy.Safety.These have been and continue to be the goals of every operator performing catheter ablation of symptomatic arrhythmias.Early attempts at catheter ablation of supraventricular tachycardias like Wolff-Parkinson-White Syndrome and atrioventricular nodal reentrant tachycardia used 7F to 8F catheters with 4 to 5 mm tip electrodes.1,2 The resulting lesions created with these tools were small and localized.The tremendous advantage of these early tools was that it was difficult to cause collateral injury to coronary arteries or adjacent extracardiac structures.The result was that the initial experience was extremely safe.Because the targets of ablation were discrete, ablating physicians learned how to identify the precise location of the arrhythmogenic substrate, and how to maneuver the ablating electrode of the catheter to a stable position directly at that location.The knowledge and understanding of the anatomy and physiology of a wide range of arrhythmias took a quantum leap forward in that setting.Interventional electrophysiology evolved into a highly technically skilled field.With subsequent efforts to ablate new more challenging arrhythmia substrates, particularly those causing atrial fibrillation and ventricular tachycardia, the basic ablation catheter designs were no longer adequate.A proliferation of innovative catheter ablation systems followed.A variety of energy sources for controlled destruction of arrhythmogenic tissue were tested, including modulated radiofrequency energy waveforms, 3 microwave energy, 4 laser energy, 5 and ultrasound energy.6 Radiofrequency energy was the preferred modality in light of its controllability, predictability, and relatively low cost.A challenge with radiofrequency catheter ablation, however, was that depth of heating was sometimes limited by biophysical constraints.Specifically, myocardial tissue is resistively heated by radiofrequency power flow through the resistive medium (the tissue), and heating is proportional to power density (or the square of current density).7 Higher power/current delivery would yield deeper heating, but the operator was limited by excess heating in areas of high current density, close to the catheter tip, and at the edges of the electrode.8 The excess heating would result in boiling at the electrode tip with char and thrombus formation when local temperatures reached 100°C.9 The question evolved how to increase current delivery and avoid excess heating at the electrodetissue interface.Two practical approaches were considered.The first attempt to increase delivered power without increasing power density was accomplished by increasing the size of the ablation electrode.Initially, ablation was attempted with 6F to 7F catheters with 2 mm tip electrodes.When the electrode tip size was increased to 8F and 4 or 5 mm tip length, ablation success increased.10 When electrodes were increased further to 8 to 10 mm tip length, much higher power is could be used, but there was not much incremental EDITORIAL Can an Expanding Lattice Electrode Catheter Expand Our Success in Catheter Ablation?