Introduction
Radiofrequency (RF) ablation is a well-adopted rhythm control strategy in the management of atrial fibrillation (AF). Since the pioneering work of Haïssaguerre et al,1, 2 pulmonary vein (PV) isolation has been a standard strategy for catheter ablation of AF. RF remains the most common energy source for point-by-point ablation for wide antral PV isolation despite the availability of alternative energy sources like cryothermy,3 laser energy4 and microwave. The success of PV isolation depends on achieving durable, transmural and contiguous lesions. However, despite the advent of irrigated and contact-force (CF) sensing catheters, PV reconnection occurs in 22% of PVs acutely and 15% of PVs three months after PV isolation.5, 6 The overall 1-year success rate for paroxysmal AF ablation is estimated at 59-89%.7 PV reconnection with recurrence of atrial arrhythmia is predominantly due to inability to achieve lesion transmurality or contiguity.8-10
The goal of successful catheter ablation is to cause irreversible tissue injury to the target cardiac tissue while avoiding unnecessary damage to surrounding tissue and collateral structures including the esophagus, coronary arteries, and the phrenic nerve. This requires a strategy to maximize the resistive heating phase and minimizing conductive heating to achieve immediate full thickness heating and minimize collateral damage. Lesion size can be increased by modulating power, CF and duration of ablation. Unfortunately, RF lesion formation is not always predictable in the clinical setting due to the variability in efficiency of energy coupling from the catheter electrode to cardiac tissue.11 Evolution of irrigated-tip catheters and CF sensing catheters have mitigated this variability and enabled delivery of higher power without excessive endocardial heating.5, 6, 12-14 Development of CF sensing represents a significant milestone in optimizing efficiency and safety of RF ablation. CF catheters have demonstrated better long term outcomes compared to non-CF catheters as seen in both SMART AF and TOCCASTAR when CF applied appropriately.8, 15-18 CF stability has been shown to be an important predictor of reduced arrhythmia recurrence.8, 17-19 There has been further evolution in catheter irrigation technology to provide uniform cooling with less fluid delivery (SMART SF).20
Many centers currently perform PV isolation and creation of additional extra-PV lesion sets using irrigated catheters to deliver power of 20-40 W for durations of 20–40 seconds at each site with a CF range of 10 to 20 g.21 The resultant long procedure times and significant rates of PV reconnection have sparked an interest in the use of high power short duration (HPSD) ablation. The definition of high power short duration ablation is arbitrary and ranges from 40 W to 90 W with variable durations generally less than 15 seconds per lesion.21-23 The biophysical ablation characteristics of HPSD ablation have been studied to determine the efficacy and safety profile of this novel technique.