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Keywords:

  • catheter ablation;
  • atrial fibrillation;
  • C-arm CT;
  • CARTO;
  • EnSite;
  • image integration;
  • registration

Accuracy of Catheter Guidance Technology in the EP Lab

  1. Top of page
  2. Accuracy of Catheter Guidance Technology in the EP Lab
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion and Conclusions
  7. References

Background

With increasing complexity in electrophysiology (EP) procedures, the use of electroanatomic mapping systems (EAMS) as a supplement to fluoroscopy has become common practice. This is the first study that evaluates spatial and point localization accuracy for 2 current EAMS, CARTO3® (Biosense Webster, Diamond Bar, CA, USA) and EnSite Velocity® (St. Jude Medical Inc., St. Paul, MN, USA), and for a novel overlay guidance (OG) software (Siemens AG, Forchheim, Germany) in a phantom experiment.

Methods and Results

A C-arm CT scan was performed on an acrylic phantom containing holes and location markers. Spatial accuracy was assessed for each system using distance measurements involving known markers inside the phantom and properly placed catheters. Anatomical maps of the phantom were acquired by each EAMS, whereas the 3D-based OG software superimposed an overlay image of the phantom, segmented from the C-arm CT data set, onto biplane fluoroscopy. Registration processes and landmark measurements quantitatively assessed the spatial accuracy of each technology with respect to the ground truth phantom. Point localization performance was 0.49 ± 0.25 mm in OG, 0.46 ± 0.17 mm in CARTO3® and 0.79 ± 0.83 mm in EnSite®. The registration offset between virtual visualization and reality was 1.10 ± 0.52 mm in OG, 1.62 ± 0.77 mm in CARTO3® and 2.02 ± 1.21 mm in EnSite®. The offset to phantom C-arm CT landmark measurements was 0.30 ± 0.26 mm in OG, 0.24 ± 0.21 mm in CARTO3® and 1.32 ± 0.98 mm in EnSite®.

Conclusions

Each of the evaluated EP guidance systems showed a high level of accuracy; the observed offsets between the virtual 3D visualization and the real phantom were below a clinically relevant threshold of 3 mm.


Introduction

  1. Top of page
  2. Accuracy of Catheter Guidance Technology in the EP Lab
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion and Conclusions
  7. References

Fluoroscopy is the basic imaging modality in the electrophysiology (EP) catheterization laboratory. For complex EP interventions, in particular atrial fibrillation ablation procedures, electroanatomic mapping systems (EAMS) and preprocedural 3D imaging (from cardiac CT, MRI, or C-arm CT) are commonly employed to supplement fluoroscopic imaging.[1-5] In EAMS, the anatomic maps generated from acquired 3D point data may be fused with a prior 3D data set to better facilitate anatomy visualization. The physician views the anatomic map and any fluoroscopy images on separate displays, with each providing live monitoring of catheter positions and independent flexible views of patient anatomy. Alternatively, fluoroscopic 3D-based overlay guidance (OG) involves a 3D-based overlay image (OI) rendered from a (segmented) patient-specific 3D volume that is merged with live fluoroscopy. Catheter tip localization and tracking are integrated into the 3D-based OG system, e.g., facilitating 3D ablation point documentation with respect to the 3D volume representation of the left atrium.

All techniques in the current study feature 3D point localization that can be used for catheter tip tagging and radiofrequency catheter ablation (RFCA) documentation. EAMS utilize the same system both to generate the anatomic maps and to mark the individual catheter positions. The 3D-based OG software relies on simultaneous biplane fluoroscopy to detect a point (e.g., a catheter tip) in two 2D views set at different projection angles. From this, a 3D point can be triangulated in 3D space, which then becomes part of the 3D scene and the registered 3D-based OI. This is a novel feature unique to the (prototype) biplane 3D-based OG software used in this study; fluoroscopic overlay guidance has only been available for monoplane systems up to now.

Prior reports have evaluated the use and outcome of nonfluoroscopic and fluoroscopic imaging technologies in a clinical setting.[6-9] The current study is the first to quantify and compare the accuracy of current EAMS, CARTO3® (Biosense Webster, Diamond Bar, CA, USA) and EnSite Velocity® (St. Jude Medical Inc., St. Paul, MN, USA), and a novel (prototype) fluoroscopic 3D-based OG software (Siemens AG, Forchheim, Germany). A phantom model experiment was performed to assess the accuracy of catheter localization, registration fidelity, and spatial measurements for each EP guidance technology. To this end, measurements taken in a 3D voxel data set acquired with a C-arm CT scan were compared to results obtained with each guidance system as further explained below.

Materials and Methods

  1. Top of page
  2. Accuracy of Catheter Guidance Technology in the EP Lab
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion and Conclusions
  7. References

Phantom experiments were carried out in the clinical EP catheterization laboratories of the Stanford University Medical Center. Application specialists of each system manufacturer attended the associated experiments to ensure appropriate experimental phantom setup and to minimize user bias during system operation.

Phantom Model

The phantom itself served as ground-truth reference to ensure exact and reproducible catheter placement during the experiments. The phantom is an acrylic glass cube with 80 mm sides, 10 mm thick walls, and an open top. Ninety-two cylindrical holes at defined positions were precisely drilled into the phantom surface to enable exact catheter tip placement. Ten embedded radiopaque spheres (2.3 mm diameter) served as fluoroscopic landmarks. A C-arm CT scan of the phantom cube was performed on an Artis zee angiography system (Siemens AG, Forchheim, Germany). A C-arm CT is a 3D data set tomographically reconstructed from 2D images obtained by rotating the C-arm around the patient over about 200°.[10] The spacing between selected spheres of the reconstructed cube was measured using the InSpace visualization environment (Siemens AG). We found that our analysis of the 3D data agreed with caliper measurements within a precision range of 0.1 mm (Fig. 1).

image

Figure 1. Distance measurement between phantom holes (magnified) using InSpace (Siemens AG, Forchheim, Germany) after zooming in MPR slice.

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Study Overview

The EAMS CARTO3® and EnSite Velocity® as well as the new 3D-based OG software feature 3D point localization. Clinically, this can be used for catheter tip tagging and RFCA documentation. As a first parameter, point localization performance was evaluated for each of the systems by repeatedly localizing objects at known positions.

Besides 3D catheter localization, the evaluated systems support the integration of a preprocedurally acquired 3D data set as an anatomical context for real-time imaging during the intervention. The nonfluoroscopic systems, CARTO3® and EnSite®, register the preprocedural data set to an associated surface representation acquired by the mapping systems themselves. The new 3D-based OG software registers a 3D-based OI with real-time fluoroscopy. To facilitate this registration, 2 views acquired simultaneously from different angles are required, as can be obtained in a biplane C-arm angiography system.[6] After registration, distance measurements were performed based on landmark positions tracked with each of the 3 navigation systems. These measurements were then compared to the corresponding distances derived from the C-arm CT voxel data set for a quantitative comparison.

3D-Based Fluoroscopy Guidance

The 3D-based OG software merges the OI with real-time fluoroscopy and displays the result on a single monitor (Fig. 2). To compute a 3D-based OI, it is beneficial to segment the objects of interest, e.g., the left atrium (LA) and pulmonary veins (PV) from a prior 3D voxel data set using dedicated software such as InSpace EP (Siemens AG, Forchheim, Germany). If the 3D data set used for computing an overlay image was acquired by the C-arm system itself before (or during) the procedure, the overlay images are autoregistered to the C-arm system's X-ray projections. If the patient moves, or if the 3D volume used for segmentation came from a prior CT or MRI scan, then a spatial registration process is necessary. For registration on a biplane system, the user manually aligns the OI to fluoroscopy in both imaging planes, using some combination of landmark and surface registration techniques. This is further described below. After registration, the 3D-based OI is kept in sync with detector position and C-arm orientation. The 3D-based OI is automatically updated if there are any changes in projection geometry, e.g., due to varied source-image-distance (SID), C-arm view directions, or table shift. Linking the 3D-based OI to the system's projection geometry maintains registration between the OI and the biplane X-ray images as long as there is no patient movement. Objects opacified under fluoroscopy, e.g., catheter tips or, in this study, landmark spheres, can be localized in 3D by triangulation. To this end, the object is manually selected in both imaging planes first. This defines 2 rays between their X-ray shadows and the associated X-ray source positions. The intersection of these 2 rays is the 3D object's position. Once the 3D position has been determined, an associated graphical representation can be added to the 3D data set and to the registered OI, respectively.

image

Figure 2. Monitor screenshot of the OG system. A 3D-based OI of the left atrium is merged with real-time biplane fluoroscopy taken under RAO –35° (a) and LAO 56° (b), respectively. A transverse view of the LA data set is shown in (c). The segmented LA (d) can be manipulated to view LA anatomy from different orientations. The segmented LA surface is multicolored to convey information about associated anatomical configurations and positions in the biplane OI more clearly: the left superior PVs are shaded in green, the left inferior PVs are blue, the right superior PVs are yellow and the right inferior PVs are purple.

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Experimental Setup

A C-arm CT scan of the cube phantom was performed on an Artis zee (biplane) system, the locations of the landmark spheres were marked in the MPR slices, and the segmented phantom was projected as an OI onto biplane fluoroscopy views . The 3D positions of the C-arm CT landmark spheres were taken as ground truth for an experiment during which we triangulated these spheres from their associated biplane X-ray shadows.

Point Localization Performance

With the C-arm at 0°/+90° (A-plane PA, B-plane left-lateral), a series of 20 biplane fluoroscopy images of the phantom was acquired. Using the 3D-based OG software, the landmark spheres’ X-ray projections provided the input to triangulate associated 3D points for each set of biplane frames (n = 200 3D points). The variation of triangulated point coordinates around their mean was taken as a measure for point localization performance.

Registration Accuracy

The 3D-based OG software facilitates surface-based as well as landmark-based registration. Surface-based registration involves visually aligning the contours of the OI with the associated contours of the corresponding structure as seen under fluoroscopy. Landmark-based registration involves aligning fiducial points in the reference 3D data set with their fluoroscopic counterparts. Both options are depicted in Fig. 3.[6, 7, 11]

image

Figure 3. Screenshot of 3D-based OG software depicting landmark-based and surface-based registration, respectively. Red arrows in the AP (+0°) (a) view and left lateral (+90°) (b) views indicate how landmarks, highlighted in the 3D data set, are shifted to their associated X-ray shadows. For surface-based registration, the contours of the 3D OI are aligned with their biplane X-ray counterparts by moving the 3D volume appropriately. Yellow arrows in (c) and (d) indicate the corresponding landmark sphere locations in a sagittal MPR view and in the segmented mesh of the reconstructed phantom, respectively.

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To evaluate registration accuracy, the phantom was repositioned at n = 20 locations on the patient table. While 1 surface-based registration was carried out with the phantom at each position, 4 landmark-based registrations (using a set of 1, 2, 3, or 4 landmark spheres) were performed. In each case, registration accuracy was quantified by measuring the Euclidean distance between spheres triangulated from biplane fluoroscopy and their corresponding reference positions in the 3D C-arm CT volume. Spheres used for landmark registration were excluded from accuracy measurements. Since there were 10 spheres, we got n = 200 measurements for surface registration, and n = 180, n = 160, n = 140, n = 120 landmark registration measurements for each experiment when using 1, 2, 3, and 4 used landmark spheres, respectively.

CARTO3®

The CARTO3® system combines electromagnetic navigation with current-based catheter localization. A locator sensor, contained in the distal end of a specialized catheter, interacts with 3 electromagnetic fields, generated by a 3-coil location pad mounted underneath the patient table, providing real-time 3D electromagnetic navigation. Electric fields between 6 surface electrode patches on the patient's front and back provide additional information for catheter electrode localization via current ratio calculations.[5]

Experimental Setup

The phantom was positioned on the patient table within the accuracy zone of the CARTO3® location pad. A skin contact simulator was connected to the patient interface unit to simulate surface ECG, and back and chest patches were installed. A NaviStar DS catheter (Biosense Webster, Diamond Bar, CA, USA) was tracked by CARTO3® and used to generate a surface map. This surface map is equivalent to an anatomic map of the interior surface of the LA (Fig. 4a), (n = 149 collected surface points).

image

Figure 4. (a) CARTO3®-surface acquisition and segmented C-arm CT data set of phantom. (b) Landmark registration based on 40 corresponding fiducial points.

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Point Localization Performance

The NaviStar DS catheter was repeatedly placed and tagged at selected phantom holes to assess accuracy of point localization (n = 42) by means of reproducibility. The xyz-coordinate of each marked point was stored. To assess localization performance, we compared all position estimates obtained at the same cavity by analyzing how individual positions measurements scattered around their mean.

Registration Accuracy

For landmark-based registration, a set of fiducial points was first placed on the anatomic map-equivalent surface model. Corresponding landmarks were then identified in the segmented C-arm CT phantom model. Landmark-based registration was performed using n = 40 manually chosen landmark pairs (Fig. 4b). This landmark registration experiment was performed 5 times (n = 200 total registration landmark measurements). A surface-based registration process was also investigated. The CARTO® landmark match statistics were used to analyze registration accuracy.

EnSite Velocity®

Three pairs of surface electrodes placed on the patient's body apply a time-varying voltage gradient for catheter electrode localization. A reference electrode serves as the origin of the EnSite coordinate system. The catheter electrodes sense the instantaneous electrical field strength, and the distance from each surface electrode is calculated with respect to the reference electrode. This calculation is complicated by the body's nonlinear impedance (due to varying tissue types). The nonlinear impedance can be compensated by field scaling and image fusion. Field scaling calibrates the nonlinear electric field based on the interpatch distances and catheter movements. Image fusion registers EnSite Velocity®'s anatomic model, generated during a mapping step to a segmented volume from a previously acquired 3D data set. Previous work has shown that good anatomical accuracy can be obtained when field scaling is performed followed by fusion with a prior 3D data set.[8]

Experimental Setup

The phantom was placed in a saline-filled container (volume = 96 liters) and positioned on the patient table of the angiography device. A C-arm CT was performed prior to the EAMS geometry acquisition. The reference electrode and EnSite®-patches were placed inside the container in contact with saline and positioned to simulate the patch locations in a clinical setup. Accurate electrical conduction was verified by the EnSite Velocity® system. The phantom geometry was collected using a 6 F quadropolar diagnostic catheter (Bard, Lowell, MA, USA) during a mapping step. Field scaling was activated. The resulting anatomic map was then registered with the segmented C-arm CT volume reconstruction of the phantom (Fig. 5a).

image

Figure 5. (a) Fusion of EnSite geometry acquisition (map) with surface model obtained by segmenting the C-arm CT data set. (b) Tagging catheter tip positions with the catheter positioned at various holes of the test phantom.

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Point localization performance

The catheter was repeatedly placed and tagged (n = 42) at selected phantom positions. The variation of the tagged catheter points around their means at each test position was measured using the EnSite Velocity® measurement tool.

Registration Accuracy

To quantify the accuracy of the registration process, the tracked diagnostic catheter was positioned at each cylindrical phantom hole (n = 92) and marked by the EnSite® system (Fig. 5b). Then the distance between the marked catheter tip and the phantom cavity in which the catheter was placed was measured and documented. Since the EnSite® environment does not support 3D measurements or read-out of 3D coordinates, all distances in the EnSite® experiment were taken as 2D surface distances using the EnSite® measurement tool. After the experiment, the “proximity to EnSite surface,” as displayed on the EnSite® workplace screen, was documented for n = 40 randomly chosen catheter positions around the phantom model. This value is the distance between the catheter tip and the closest point in the previously acquired EnSite® geometry. In these experiments, the “proximity to EnSite surface” parameter was used to ensure that constant conditions of electrical conduction were maintained throughout the experiment.

Spatial Accuracy Comparison

Distance measurements between points were performed to compare spatial accuracy among the 3D-based OG software, CARTO3®, and EnSite®. For the 3D-based OG software, distances were measured between reconstructed phantom spheres. In case of CARTO3® and EnSite®, distances were obtained between marked holes on the acquired phantom surface geometry. The measured distances were then evaluated against reference distance measurements (n = 49) obtained from the (ground truth) C-arm CT voxel data set of the phantom.

Statistical Methods

Mean values were calculated as arithmetic averages, and they are represented as mean ± standard deviation. The Shapiro–Wilk test was used to test for normal distribution; paired t-tests were applied for dependent data. The Euclidean distance was used to evaluate the length between two 3D coordinates as the square root of the sum of the squares of x, y and z coordinate differences. A Bravais–Pearson coefficient was determined for the 2-tailed correlation of the ratio-scaled landmark distance measurements.

Results

  1. Top of page
  2. Accuracy of Catheter Guidance Technology in the EP Lab
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion and Conclusions
  7. References

Point Localization Performance

The point localization performance was 0.49 mm ± 0.25 mm in 3D-based OG, 0.46 mm ± 0.17 mm in CARTO3®, and 0.79 mm ± 0.83 mm in EnSite®. The “proximity to EnSite surface” parameter was calculated as 0.11 mm ± 0.98 mm, range –1.5 mm to 2.5 mm, demonstrating constant conditions of electrical conduction during the EnSite experiment. There was no statistically significant difference of catheter localization performance between the 3D-based OG software and CARTO3® (P = 0.670). The difference between the 3D-based OG software- and EnSite®- as well as the difference between CARTO3®- and EnSite®- catheter localization performance was highly significant (P<0.01).

Registration Accuracy

Registration accuracy quantifies the concordance of phantom visualization and catheter localization, with respect to the ground truth phantom (Fig. 6). Clinically, this parameter indicates the conformity of, for example, the acquired virtual LA/PV-geometry with the real LA/PV-anatomy.

image

Figure 6. 3D accuracy after registration process of 3D-based OG software, CARTO3® and EnSite®.

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Figure 6 shows the offsets between the virtual phantom visualization and the ground-truth C-arm CT data set as determined using the registration processes for each system.

As expected, the 3D-based OG system achieved best registration results when the voxel data set was autoregistered (1.04 mm ± 0.33 mm). When registering under 3D-based OG after moving the phantom, the difference between the surface-based approach (1.27 mm ± 0.57 mm) and landmark-based approach using 1 landmark (1.79 mm ± 0.54 mm) was statistically significant (P<0.01). The offset between the overlay registration based on 1 landmark was significantly different than registration based on 2 (1.34 mm ± 0.50 mm), 3 (1.15 mm ± 0.58 mm) or 4 landmarks (1.10 mm ± 0.52 mm) (P<0.01). There was no significant difference between registration based on 3 or 4 landmarks. Also, there was no significant difference between surface and landmark registration, if more than 2 landmarks were included in the registration process. There was no significant difference in CARTO3® landmark registration accuracy between the 5 landmark registration groups.

Spatial Accuracy Comparison

The spatial accuracy comparison shows how well distance measurements made in each of the evaluated systems agree with known ground truth distances. It indicates, for example, the reliability of PV diameter measurements in acquired left atrial geometry during atrial fibrillation ablation procedures.

The Bland–Altman plots in Figure 7 show comparisons of distance measurements in the 3D-based OG software, CARTO3®, and EnSite® with the reference distance measurements in the ground truth C-arm CT data set. The mean absolute offset of distance measurement was 0.30 mm ± 0.26 mm in 3D-based OG, 0.24 mm ± 0.21 mm in CARTO3® and 1.32 mm ± 0.98 mm in EnSite®. Average measured C-arm CT distances were at 13.6 mm ± 10 mm, range 4.8 mm–40.4 mm. The correlation coefficient was 0.99 for the 3D-based OG software, 1.0 for CARTO3® and 0.98 for EnSite®.

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Figure 7. (a) Bland–Altman plot comparing the spatial distance measurements between 3D-based OG and phantom C-Arm CT. (b) Bland–Altman plot comparing the spatial distance measurements between CARTO3® and phantom C-arm CT. (c) Bland–Altman plot comparing the spatial distance measurements between EnSite® and phantom C-Arm CT.

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Limitations

The phantom model itself and the C-arm CT volume reconstruction of the phantom were both considered to provide a ground truth reference. Because there are small errors in C-arm CT acquisition and the reconstruction process, there are marginal differences between the real phantom and its 3D reconstruction. These small errors affect the precision range of the experimental offset measurements.

The CARTO3® system requires the use of a NaviStar DS catheter, which was not used for the 3D-based OG or EnSite® experiments; however, the application specialists of CARTO® and EnSite® assured that system accuracy would not be influenced by the type of catheter employed.

Discussion and Conclusions

  1. Top of page
  2. Accuracy of Catheter Guidance Technology in the EP Lab
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion and Conclusions
  7. References

We report the first study that compares 3D localization and registration accuracy between a new (prototype) fluoroscopic overlay software and current nonfluoroscopic EP guidance technology. Whereas previous studies investigated the accuracy of single fluoroscopic[3] and nonfluoroscopic systems[11, 12] in a clinical setting, we opted for a phantom study involving ground truth for a better quantitative comparison. Below, we take a closer look at our results obtained for each approach.

The 3D-based OG system achieved the highest level of 3D accuracy when a C-arm CT volume was acquired directly prior to the experiment. This is expected: The C-arm CT data set is autoregistered to the X-ray images because it was reconstructed from projection images acquired by the same system in the same geometry. However, the registration error (1.04 mm ± 0.33 mm) in this case was not negligible (Fig. 6). We attribute this distortion to a (slight) residual iso-center offset between the A-plane C-arm and B-plane C-arm, meaning that the center of rotation for the A-plane and B-plane are not in the exact same spot in 3D space.

We also found that landmark-based and surface-based registration approaches achieved a similar level of overlay integration accuracy if at least 3 fiducial points were involved.

In addition, the spatial distance measurements, carried out as part of the spatial accuracy comparison, showed higher accuracies than the registration processes. This is due to errors introduced by the segmentation step and (small) alignment issues during the registration process.

The 3D-based OG system has sufficient accuracy to reconstruct structures such as diagnostic or ablation catheters in 3D space based on a set of associated points in biplane fluoroscopy images. Models of more complex devices that cannot be visualized in EAMS, such as cryo-balloon ablation catheters, can be computed and visualized in 3D-based OG as well (Fig. 8).

image

Figure 8. Biplane fluoroscopic 3D-based OG software view (–24°/59°) of a cryo atrial fibrillation ablation procedure. The sections (a) and (b) show the biplane fluoroscopic view on the 3D overlay of the left atrium. A 28 mm cryo-balloon (Arctic Front Achieve, Medtronic, MN, USA) is placed at the right inferior pulmonary vein and reconstructed by the 3D-based OG software. The 3D reconstruction is displayed in an LAO view in section (d) of the 3D-based OG screen. Section (c) shows the MR-angiography of the left atrium including the reconstructed balloon.

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This study suggests that the fluoroscopic 3D-based OG software is reliable enough to aid in complex ablation procedures. In addition, 3D-based OG can bring accurate and substantial information to standard fluoroscopy without the added cost of specialized catheters or location pads. However, this technology is limited in that it requires the use of ionizing radiation, whereas EAM systems have the potential to substantially decrease exposure to radiation.[13]

Although all 3 systems demonstrated a high level of intrinsic accuracy as investigated by repeated catheter placement at selected phantom positions (point localization performance), CARTO3® showed a somewhat higher accuracy than EnSite®, which can be ascribed to the magnetic field localization technology of CARTO3®. One advantage of using magnetic fields for catheter localization is that the fields are unaffected by the presence of the human body and not differently interacting with thoracic tissues, so the localization accuracy of CARTO3® does not depend on the different tissue types or cardiac anatomy. Also note that our findings regarding CARTO3®'s localization performance and 3D accuracy match the results presented by Gepstein et al.,[5] During our experimental setup for evaluation of the EnSite® system, we went to great lengths to provide conditions that may not always be achievable in clinical practice such as a very homogeneous impedance field, and a fixed reference electrode. Under clinical conditions, the reference electrode may shift with respect to the left atrium, especially when ablating in the coronary sinus during persistent atrial fibrillation.[14] As EnSite®'s catheter localization is based on electrical field measurements, the system can be influenced by impedance changes and differences in tissue types. Unaccounted impedance changes inside the body due to an increase of saline and volume shifts when using an irrigated ablation catheter may also impact the localization accuracy of the EnSite® system. Also different patterns of respiration my influence the accuracy of EnSite®, especially when localized catheters are placed distally in a PV, the pulmonary artery or the aorta. In a clinical scenario we expect that EnSite®'s accuracy may be regionally influenced by electrical conductance of tissue, circulation and impedance changes.

The Bland–Altman plots (Fig. 7) demonstrate a very low bias of average length measurements performed in the EP guidance systems and the C-arm CT data set. However, the variance of length measurements in EnSite® was higher than in the 3D-based OG software or CARTO3®, as indicated by the confidence intervals.

In a clinical scenario, EP guidance technology has to compensate for respiration and gross patient movements as well. EnSite®'s use of a reference electrode inserted distally into the coronary sinus vein has the advantage that it can capture respiratory movements there, although it will also be affected by heartbeat. If the 3D position of mapped points can be tracked over time as enabled by the CARTO3® system, it is possible to estimate both cardiac and breathing motion using multiband filters, since these motion patterns occur at different frequencies.[15] Once heartbeat and breathing motion are known, they can be used for motion compensation to stabilize catheters relative to an available 3D map. The new 3D-based OG system also offers algorithms to take motion into account. One method is to track the circumferential mapping catheter when placed at the site of ablation and to shift fluoro overlay images accordingly.[16, 17] The clinical performance of this method relies on frequent use of fluoroscopy and has yet to be evaluated in further studies.

In conclusion, each of the evaluated EP imaging systems showed a high level of accuracy, and the observed offsets between the virtual 3D visualization and the real phantom were below a clinically relevant threshold. It remains the clinician's decision to select the most appropriate navigation system for the case at hand.

References

  1. Top of page
  2. Accuracy of Catheter Guidance Technology in the EP Lab
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion and Conclusions
  7. References
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