Real-time lesion assessment using a novel combined ultrasound and radiofrequency ablation catheter.
BACKGROUND
Assessment of lesion size and transmurality is currently via indirect measures. Real-time image assessment may allow ablation parameters to be titrated to achieve transmurality and reduce recurrences due to incomplete lesions.


OBJECTIVE
The purpose of this study was to visualize lesion formation in real time using a novel combined ultrasound and externally irrigated ablation catheter.


METHODS
In an in vivo open-chest sheep model, 144 lesions were delivered in 11 sheep to both the atria and the ventricles, while lesion development was monitored in real time. Energy was delivered for a minimum of 15 seconds and a maximum of 60 seconds, with a range of powers, to achieve different lesion depths. Twenty-two lesions were also delivered endocardially. The ultrasound appearance was assessed and compared with the pathological appearance by four independent blinded observers.


RESULTS
For the ventricular lesions (n = 126), the mean power delivered was 6.1 ± 2.0 W, with a mean impedance of 394.7 ± 152.4 Ω and with an impedance drop of 136.4 ± 100.1 Ω. Lesion depths varied from 0 to 10 mm, with a median depth of 3.5 mm. At tissue depths up to 5 mm, changes in ultrasound contrast correlated well (r = 0.79, R(2) = 0.62) with tissue necrosis. The depth of ultrasound contrast correlated poorly with the depth of the zone of hemorrhage (r = 0.33, R(2) = 0.11), and impedance change correlated poorly with lesion depth (r = 0.29, R(2) = 0.08).


CONCLUSIONS
Real-time lesion assessment using high-frequency ultrasound integrated into an ablation catheter is feasible and allows differentiation between true necrosis and hemorrhage. This may lead to safer and more efficient power delivery, allowing more effective lesion formation.
Cardiovascular Division, Kings College London BHF Centre, London, United Kingdom. matthew.wright@kcl.ac.uk
Matthew
M
Wright
Erik
E
Harks
Szabolcs
S
Deladi
Freek
F
Suijver
Maya
M
Barley
Anneke
A
van Dusschoten
Steven
S
Fokkenrood
Fei
F
Zuo
Frédéric
F
Sacher
Mélèze
M
Hocini
Michel
M
Haïssaguerre
Pierre
P
Jaïs
D000818:Animals; D001281:Atrial Fibrillation / Q000000981:diagnostic imaging / Q000601:surgery*; D017115:Catheter Ablation / Q000295:instrumentation* / Q000379:methods; D057785:Catheters; D004195:Disease Models, Animal; D004867:Equipment Design; D004869:Equipment Safety; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000601:surgery; D009206:Myocardium / Q000473:pathology*; D009336:Necrosis / Q000473:pathology; D012756:Sheep; D018084:Ultrasonography, Interventional / Q000379:methods; D014693:Ventricular Fibrillation / Q000000981:diagnostic imaging / Q000601:surgery*