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.