Disclosures:
Dr Romero has received grant support from Biosense Webster (BWI-IIS-535) for an investigator-initiated study (The PLEA Trial; https://www.clinicaltrials.gov; Unique identifier: NCT04216667). Dr. Romero is a paid consultant for Biosense Webster, Sanofi-Aventis and AtriCure.
Funding: None
Catheter ablation (CA) is the mainstay therapy for the maintenance of sinus rhythm in patients with paroxysmal and persistent atrial fibrillation (AF). Pulmonary vein isolation (PVI) has remained the most frequently used treatment strategy for this entity. Radiofrequency ablation (RFA), which has been in use for over 3 decades, is the most frequent energy source implemented for CA followed by cryoablation and laser, with alternative energy sources (including focused ultrasound, and microwave energy) used mainly in investigational studies with limited clinical applicability. The understanding of RF biophysics enables electrophysiologists to titrate tissue current delivery to control lesion surface area and depth. Nonetheless, in the case of PVI, RFA is associated with several potential complications or significant adverse events, including pulmonary vein stenosis, incomplete circumferential ablation, and thermal damage to adjacent structures (e.g., right phrenic nerve, esophagus), which limits lesion efficacy to maintain patient safety.
Although cryoablation was introduced as a faster and potentially safer alternative to achieve a complete PVI, it was also associated with a significant risk of phrenic nerve and esophageal injury and offers no real advantages in terms of arrhythmia recurrence (1). Use of direct current (DC) delivered through diagnostic catheters to elicit cellular destruction dates to the early days of CA. Nonetheless, the large amount of energy necessary to produce tissue destruction (up to 300 J - by what was considered to be “fulguration”) was painful and the delivery of large monophasic unipolar defibrillation waveforms from small surface area diagnostic electrodes resulted in hazardous effects (2-4). These included the formation of gas vapor globe and arcing at the tip of the electrode, which produced barotrauma related complications including myocardial perforation and tamponade and formation of non-homogeneous lesions, which were proarrhythmic (5,6). The mechanism of lesion formation during DC ablation was later determined to be irreversible electroporation (IRE) (7,8). Subsequent studies used lower energy to achieve successful ablation with a reduced risk of adverse events (9-11). Nevertheless, before these improvements could be adopted, RFA became available and quickly achieved widespread acceptance given the ability to provide a controlled amount of energy, a greater effectiveness and a lower incidence of life-threatening complications compared to DC ablation.
Recently, ablation using electric fields generated by short pulses of high energy, known as pulsed field ablation (PFA), has shown promise by specifically targeting myocardium without generating heat or damaging adjacent tissue.