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Image Integration in Atrial Fibrillation Ablation Procedures
generated using a pre-procedural MRI or CT scan. The catheter is then
Figure 1: Computed Tomography/Left Atrium Overlay
localized using magnetic localization technology. The CartoMerge system
Showing the Ablation Catheter at the So-called ‘Ridge’
has been associated with an increased efficacy of ablation and a reduction
Between the Left Superior Pulmonary Vein and Appendage
in procedure time.
11
CartoMerge was first examined for clinical efficacy and safety in nine dog
models.
12
The authors concluded that the study supported the clinical use of
the image integration system in catheter ablation procedures either in the
atria or in the ventricles. In addition, the CT image registration process
presented a significant advantage over the less detailed reconstructed 3D
maps and was suggested to be helpful for the ablation of AF.
The first human clinical study was performed in six patients with drug-
refractory AF.
13
A position error of 3mm was reported in this study using a
combined registration strategy, where the pre-acquired MRI and CT images
were registered to the 3D mapping space. Both landmark registration and
surface registration were implemented in the study. The registration error after
each landmark registration resulted in 60% pulmonary vein misalignment.
Surface registration resulted in a significant improvement in pulmonary vein
Figure 2: Computed Tomography Image of a Patient’s Cardiac
alignment and reduced the distance between 3D MRI/CT reconstruction and Anatomy Combined with Live Fluoroscopy Data
realtime mapping. The study demonstrated that image integration in ablation
improves the success of ablation procedures and the combination of two
registration techniques increases the accuracy of the image fusion.
A recent study compared the clinical outcomes of AF using the previous
model (CartoXP) and the new CartoMerge system.
14
In the study,
81 patients were randomly assigned to ablation with either the CartoXP or
the CartoMerge system. The isolation of pulmonary veins was achieved in
95 and 92% of patients in the CartoMerge and CartoXP groups,
respectively. In addition, AF was cured in 79 and 74% of cases treated with
the CartoMerge and CartoXP, respectively. CartoMerge also reduced
procedure time and hence X-ray exposure. However, CartoMerge did not
appear to have any effect on the outcome of the ablation procedure,
although this may have been due to all of the procedures being carried out
by experienced operators.
The integration of the two images allows the precise position of the catheter to be shown in relation to detailed
3D anatomy of the heart generated using rotational angiography.
Computed Tomography–Fluoroscopy Guidance Systems
CT–fluoroscopy guidance systems have now been introduced that provide an
automatically segregated image combining pre-procedural CT images with undergo catheter ablation with or without the CT–fluoroscopy guidance
realtime fluoroscopy mapping. The use of these systems during an ablation system. In the CT–fluoroscopy arm there were shorter procedure times and
procedure may offer advantages over the electroanatomical CartoMerge a trend toward a higher success rate for AF ablation. However, this software
system. For example, through registration of detailed CT of the left atrium could not record ablation points on the CT scan, so the CartoMerge system
with the realtime fluoroscopy image, tissue delineation is included in the of recording the delivered ablation lesions was used. Work is ongoing to
fluoroscopic view and the course and position of the ablation catheter are develop a way of marking lesion locations on the fluoroscopy guidance
depicted. This may result in improvements in the manipulation of the system. Further larger-scale studies are required to assess the impact of
catheter, which leads to shorter procedure times. Unlike the tracking catheter this system on the outcome of AF ablation procedures.
used in the electro-physiological catheter, the coronary sinus was used as a
landmark, allowing registration to be performed automatically and more EP Navigator (Philips Healthcare)
quickly. In addition, the availability of realtime background fluoroscopy The EP Navigator is a recently introduced imaging tool to aid the
allows as many validations of the registration process as required, and treatment of complex cardiac rhythm disorders. The EP Navigator enables
also allows for patient movement during the procedure. Using this software, electrophysiologists to segment pre-interventional 3D CT images of a
registration can also be achieved in different views by automatically adjusting patient’s cardiac anatomy and overlay and register these 3D images with
the CT image to the fluoroscopy orientation. live X-ray fluoroscopy catheter position information (see Figure 1). The
resulting single image supports catheter/device navigation during
A CT–fluoroscopic guidance system was evaluated in a controlled study specified procedures. This helps physicians to navigate through the heart
including 50 patients with symptomatic AF.
15
Patients were randomized to during complex procedures. The EP Navigator instantly indicates the
US CARDIOLOGY 51
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