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Epicardial Atrial Ablation with High Intensity Focused Ultrasound on the Beating Heart'

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Division of Cardiothoracic Surgery College of Physicians and Surgeons of Columbia University ... success rate in curing AF during concurrent surgery utilizing ... – PowerPoint PPT presentation

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Title: Epicardial Atrial Ablation with High Intensity Focused Ultrasound on the Beating Heart'


1
Epicardial Atrial Ablation with High Intensity
Focused Ultrasound on the Beating Heart.
Mathew Williams, Mauricio Garrido, Susan
Kourpanidis, Jennifer Casher, Alessandro Barbone,
Paul DiGiorgi, David DAlessandro, Michael
Argenziano, Yoshifumi Naka
Division of
Cardiothoracic Surgery

College of Physicians and Surgeons of Columbia
University
Background
Results
Imaging
The Cox-Maze III remains the most successful
curative treatment of Atrial Fibrillation
(AF). We and others have demonstrated a
70-80 success rate in curing AF during
concurrent surgery utilizing various energy
sources to isolate only the pulmonary veins in
lieu of the standard cut sew Maze
incisions. The ability to create lesions on the
beating heart will be paramount to the evolution
of the surgical treatment of atrial
fibrillation. High intensity focused
ultrasound (HIFU) is a method for creating
transmural epicardial lesions on the beating
heart. HIFU has several potential advantages
including rapid lesion creation and easy
adjustment of ablation depth. Additionally,
imaging (to assess lesion creation) is readily
facilitated by this mode.
42 (71) of the 59 lesions were transmural.
The average lesion depth was 2.5 1.7 mm. In
comparing non-transmural v. transmural specimens,
the total wall thickness (myocardium fat) was
thicker in non-transmural specimens (6.4 mm 3.9
mm v. 2.7 mm 2.1 mm, p lt 0.05). However, the
ablation depths were similar (2.8 mm 1.8 mm v.
2.3 mm 1.3 mm, pns), indicating HIFU ablates
at a depth based on its focal length
irrespective of epicardial fat, endocardial
blood or location.
A separate study was performed to determine if
lesions could be visualized after creation.
Lesions were created in vitro on the ventricle
of a pig. Representative results shown below.
Purpose
To determine if transmural lesions can be
created on the beating heart using HIFU. To
determine if HIFU lesions can be successfully
applied through epicardial fat. To determine
if HIFU lesions can be visualized with
ultrasound imaging.
Examples of the appearance of HIFU lesions
created in pig ventricle.
HIFU Physics
Methods
Spectrasonics F/1.5 23 mm diameter spherically
focused transducer was used to create
lesions. Water path standoff was used to adjust
lesion depth within myocardium. The acoustic
focus was located just anterior to
the endocardial surface to obtain the most
reliable transmurality. Shown below is a
laser image of a representative acoustic
field.
4 dogs with open chests. 59 spot lesions
created on both right and left atria. Ablation
created using HIFU at 7.3 MHz (nominal) with a
focus at 5 mm. Power varied between 10 and 100
Watts (into transducer) and ablation time from
0.5 - 4 seconds. Animals allowed to survive for
2 hours after ablation Tissue stained with
vital dye- triphenyl-tetrazolium chloride
(TTC). Tissue depth, fat depth and lesion depth
were characterized.
B-mode images obtained using an ATL HDI Ultramark
9 Imaging System and L10-5 Linear Probe
Conclusions
HIFU can create transmural lesions on the
beating heart in a short amount of
time. HIFU reliably ablates at a defined depth.
The ability to electronically alter this depth
is required and should result in reliably
transmural lesions. Early attempts at
visualizing lesions are promising.
For additional questions please contact Mathew
Williams, MD via email- mw365_at_columbia.edu
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