Very High Power Very Short Duration Ablation for Atrial
Fibrillation: with great power comes great responsibility
Short Title: Very high power short duration ablation
Key words: HPSD ablation, 90 watts ablation, QDot, QMode
Dhiraj Gupta1 MD
Peter Calvert1 MBChB
1 Liverpool Centre for Cardiovascular Science,
University of Liverpool and Liverpool Heart & Chest Hospital Liverpool,
UK
Correspondence:
Professor Dhiraj Gupta
Professor of Cardiac Electrophysiology / Consultant Cardiologist &
Electrophysiologist
Department of Cardiology,
Liverpool Heart and Chest Hospital,
Liverpool, L14 3PE, U.K.
Tel: +44(0)1516001616
Email: dhiraj.gupta@lhch.nhs.uk
Word count: 1562
Funding: None
Conflicts of Interest: DG has received research funding from Biosense
Webster, Boston Scientific and Medtronic.
For all the advances in electrophysiology, the need to create a focal
ablation lesion using radiofrequency (RF) energy has remained remarkably
constant. However, the recipe for the perfect RF lesion continues to
elude us even after almost 40 years of research and clinical experience.
As we continue our search for the holy grail of transmurality and
durability with assured safety, there has been renewed interest in
temperature controlled (TC) ablation. Accurate tip temperature feedback
from catheters such as the QDot MicroTM catheter
(Biosense Webster Inc, Irwindale, CA) have allowed for the first time
the use of very high power, very short duration (vHPvSD) ablation that
utilises 90W RF power for just 4 seconds of ablation per lesion,
delivered in the TC mode. Ex-vivo experiments have demonstrated that
vHPvSD ablation produces larger, shallower, and more homogeneous lesions
as compared to standard power-controlled ablation (sRF); characteristics
that should be ideal for the thin-walled left atrial tissue. vHPvSD also
produces more transmural and contiguous linear lesions with fewer steam
pops compared to sRF ablation, which would be particularly useful for
ventricular tissue. If these extremely encouraging results could be
replicated in the clinical arena, our search for perfect RF lesion
creation may be finally over. Are these high hopes being realised?
The clinical feasibility of the vHPvSD approach was first demonstrated
in the QDOT-FAST trial, in which 52 patients underwent successful
pulmonary vein isolation (PVI) with impressively short mean procedural
and ablation times of 105 min and 8 min respectively. However, new
asymptomatic cerebral lesions (ACLs) were identified in 6 (14%)
patients who underwent MRI scanning, with 4 of these occurring despite
uninterrupted anticoagulation. While no patients suffered clinically
significant neurological effects, and all but one of these ACLs resolved
on repeat MRI performed at 1 month, it did throw a spotlight on an issue
that needed redressal before this technology could supplant the other
well-established RF ablation techniques.
In this edition of the Journal of Cardiovascular Electrophysiology,
Mueller and colleagues present a single-centre experience of safety
outcomes in 34 patients undergoing vHPvSD AF ablation. The principal
findings of this study are: 1) modest acute efficacy, as seen by
disappointing first pass isolation (FPI) rates of 18% of patients and
54% of PV pairs; 2) a concerning safety signal in the form of coagulum
on the catheter tip in 10 (18%) patients and ACLs on post-procedure MRI
in 26% patients. The same group had described a similarly high rate of
catheter tip coagulum (11%) and ACLs (24%) in a previous cohort of
patients after which several software amendments to the RF generator
(nGEN) were made. However, it appears that the underlying issue
persists. Whilst Mueller and colleagues deserve credit for sharing their
findings, these will cause consternation amongst the electrophysiology
community. After all, with vHPvSD we were hoping for an improvement in
both procedural efficacy and safety, but the data from Mueller et
al. suggest the polar opposite. This editorial piece will attempt to
put these new findings in context with other published work in this
area, and also with our own observations gleaned from using vHPvSD for
the past 18 months.