Localization of Accessory Pathways in Pediatric Patients with Wolff-Parkinson-White Syndrome using 3D-rendered Electromechanical Wave Imaging

Abstract

Background:

Prediction of accessory pathway (AP) locations in patients with Wolff-Parkinson-White syndrome is currently based on analysis of 12-lead ECG. In the pediatric population, specific algorithms have been developed to aid in localization, but these can be unreliable. Electromechanical Wave Imaging (EWI) is a non-invasive imaging modality relying on a high frame rate ultrasound sequence capable of visualizing cardiac electromechanical activation.

Objective:

This study seeks to demonstrate the feasibility of EWI for localization of APs prior to catheter ablation in a pediatric population.

Methods:

Pediatric patients with ventricular pre-excitation presenting for catheter ablation were imaged with EWI immediately prior to the start of the procedure. Two clinical pediatric electrophysiologists predicted the location of the AP based on ECG. Both EWI and ECG predictions were blinded to the results of catheter ablation. EWI and ECG localizations were subsequently compared to the site of successful ablation.

Results:

Fifteen patients were imaged with EWI. One patient was excluded for poor echocardiographic windows and the inability to image the entire ventricular myocardium. EWI correctly predicted the location of the AP in all 14 patients. ECG analysis correctly predicted 11/14 (78.6%) of the AP locations.

Conclusion:

EWI was shown capable of consistently localizing accessory pathways. EWI predicted the site of successful ablation more frequently than analysis of 12-lead ECG. EWI isochrones also provide anatomical visualization of ventricular pre-excitation. These findings suggest that EWI can predict AP locations, and EWI may have potential to better inform clinical electrophysiologists prior to catheter ablation procedures.

Condensed Abstract:

Electromechanical Wave Imaging (EWI) is a non-invasive imaging modality relying on a high frame rate ultrasound sequence to visualize cardiac electromechanical activation. This study used EWI to localize accessory pathways (APs) prior to catheter ablation in pediatric patients. Fifteen patients were imaged. One patient was excluded for poor echocardiographic windows and the inability to image the entire ventricular myocardium. EWI and standard 12-lead-ECG readers were blinded to the results of catheter ablation. EWI successfully predicted 14/14 AP locations, while ECG predicted 11/14. These findings suggest EWI can locate APs in pediatric patients and provide useful information to clinical electrophysiologists prior to catheter ablation procedures.

Introduction:

Accessory pathways (AP) in Wolff-Parkinson-White (WPW) syndrome are commonly treated with catheter ablation.(1–3) Localization of the AP prior to catheter ablation is important for preprocedure planning. The current standard for locating the AP is the clinician’s interpretation of 12-lead ECG. However, this method is limited and localization may differ among clinicians. Many algorithms have been proposed with varying degrees of success. Specific algorithms have been developed in the pediatric population, but there is still significant room for improvement.(49) Moreover, the reported algorithms have been less accurate than those used in adult patients, and frequently the accuracy of these algorithms in clinical practice is lower than in the originating author’s hands.(9–11)

Non-invasive, more precise, and less time-consuming localization of APs could be of clinical benefit to operating electrophysiologists. Previously, there have been multiple non-invasive methods proposed for localization of APs, such as from Botvinivk et al.(12) Modern electrical mapping approaches such as electrocardiographic imaging (ECGI) have emerged in specialized clinical settings.(13) However, ECGI is an expensive technique that requires patient specific models of cardiac geometry derived by CT or MRI scan, potentially exposing patients to ionizing radiation or anesthesia. More recently, echocardiography strain-based methods have been explored as potential tools for the non-invasive identification of APs.(14,15)

Electromechanical Wave Imaging (EWI) is a non-invasive and non-ionizing ultrasound-based modality that maps the electromechanical activation in all cardiac chambers at a very high frame rate.(16,17) Moreover, EWI has been shown capable of accurately determining the origin of activation during ventricular pacing from different endocardial and epicardial sites in paced canine hearts in vivo.(18)

In this study, EWI is used for the first time in a pediatric population. Our aim was to investigate the feasibility of using this transthoracic ultrasound technique for the localization of accessory pathways in pediatric patients with WPW.

Methods:

Patient Recruitment and Study Design:

Patients presenting to the Columbia University Medical Center pediatric cardiac electrophysiology laboratory for treatment of ventricular pre-excitation by catheter ablation were approached for recruitment in this study. The Columbia University Institutional Review Board approved all methods and procedures prior to the onset of the study. After consent, background data were obtained through patient histories and review of the medical record. All patients recruited were known to have previously recorded, evident ventricular pre-excitation on resting ECG, and previously acquired transthoracic echocardiography demonstrated normal cardiac anatomy and function. Two pediatric electrophysiologists predicted the location of the AP based on the previously recorded ECG using their clinical experience and both the Boersma et al. and Arruda et al. algorithms.(5,6)

All patients underwent EWI with a trained sonographer using standard transthoracic echocardiography immediately prior to the catheter ablation procedure. Full view of the ventricular myocardium was required for EWI processing; when the anatomy was not completely visible during the initial scan, the patient was excluded from the analysis. Obtaining an EWI scan required approximately 15 minutes in the pre-operative area on the day of the procedure. The processing of each EWI scan required approximately 90 minutes, including generation of both 2D and 3D-rendered isochrones (approximately 70 minutes for 2D only). After the start of the study, the protocol was amended to include an additional EWI scan immediately after the catheter ablation procedure. After generation of the EWI isochrones, a location was assigned based on a standardized segmented template of the ventricles. This template was created prior to the enrollment of patients and was specifically designed for this study based on similar templates in the literature with the addition of RV segments.(19) This template includes 19 different segments (the basal segmentation is similar to standard ECG algorithms with 10 segments at the level of the AV rings in this study, compared to eight segments in the Boersma et al. algorithm and 10 in the Arruda et al. algorithm) as shown in Figure 1e.(5,6)

Figure 1: Study processing pipeline - example on a patient with a left posterolateral pathway.

a) 2D apical views of the heart are acquired at a high frame rate of 2000 frames/second with a diverging ultrasound transmit sequence; b) Axial displacements and strains are estimated on the radiofrequency data and the myocardium is manually segmented on the first B-mode image; c) The zero-crossing (ZC) locations corresponding to the activation times (t act) for each point are selected on the incremental strain curves to generate the 2D isochrones; d) The four multi-2D electromechanical activation maps are then co-registered and an interpolation is performed around the circumference to generate the 3D-rendered isochrones, displaying the earliest activation after QRS onset in red and latest in blue; e) A 19-segment template of the ventricles is used to predict the pathway location based on EWI results (10 segments around the atrioventricular rings include: anteroseptal, posteroseptal, left posterior, left posterolateral, left lateral, left anterolateral, left anterior, right anterior, right lateral, and right posterior). On the right-hand side, the three corresponding cross-section slices of the 3D-rendered isochrone are displayed, with the earliest activated region visible posterolaterally at the valve level. TV: Tricuspid Valve and MV: Mitral Valve; f) The Boersma et al. algorithm is performed on the 12lead ECG to determine the AP location(6); g) Both EWI and ECG location predictions are validated against the intracardiac map and site of successful ablation.

Both EWI and the clinical electrophysiologists reading the ECGs were blinded to pre-procedure planning and the outcome of the electrophysiology study and ablation. The predicted AP locations based on the isochrones and on ECG were then compared to the site of successful ablation or the earliest site of activation if no ablation was attempted (Figure 1e-g). When computing the localization accuracy, predictions for both EWI and clinician interpretation of ECG were considered correct if they were in the same segment, or an adjacent segment, to the actual location of the AP.

Electromechanical Wave Imaging:

EWI is based on a high frame rate echocardiography sequence that transmits a single diverging wave at 2000 frames per second (fps), while simultaneously recording a Lead II ECG in synchrony with the ultrasound acquisition.(20) The full methods pipeline is detailed in Figure 1a-d. Four transthoracic apical two-dimensional views were acquired (Figure 1a) with a 2.5 MHz phased array transducer (P4–2 ATL/Philips, Andover, MA, USA) connected to a Vantage Research scanner system (Verasonics Inc., Kirkland, WA, USA). A 90° and 14-cm deep field of view was used to image the ventricles. However, for adolescents older than 16 years old it was necessary to perform the scans with a larger 20-cm depth, standardly used in adults, in order to cover the entire region of interest.

Manual segmentation of the myocardium was performed on the first B-mode frame for each view and tracked automatically throughout the rest of the cardiac cycle (Figure 1b).(21) Motion estimation was performed axially on the radiofrequency (RF) data with 1D cross-correlation tracking.(22) The incremental axial strains were then derived with a least-squares estimator and overlaid onto the B-mode images.(23) The ventricular activation times were defined as the zero-crossing of the strain curves, i.e. the timing of the first sign change in inter-frame electromechanical axial strain after the QRS onset.(24) The zero-crossing locations were picked for approximately one hundred randomly selected points in the segmented myocardial region of interest (Figure 1c), and the activation times were then interpolated throughout the entire mask to achieve a homogeneous pattern. All 2D isochrones display the electromechanical activation in milliseconds, with the earliest activated region in red and the latest in blue. The four resulting multi-2D electromechanical activation maps were later co-registered around the left ventricle longitudinal axis of symmetry. In each longitudinal slice, a linear interpolation was performed around the circumference to subsequently generate the 3D-rendered isochrones (Figure 1d).(25)

Electrophysiology Study and Ablation Procedures:

All catheter ablation procedures were performed under general anesthesia using standard techniques, equipment, and electroanatomic mapping (EnSite, St. Jude Medical, Inc., St. Paul, MN, USA). All patients had a surface ECG recorded followed by vascular access. After vascular access was obtained, catheters were placed near the His Bundle, right atrial appendage, right ventricular apex, and coronary sinus. Pacing protocols were performed with rapid atrial pacing from the high right atrium, atrial and ventricular extrastimulus testing at baseline and on isoproterenol. For left-sided APs, access was obtained via trans-septal puncture. Ablation was performed with radiofrequency or cryoablation technique. AP location was determined by the site of successful ablation.

Statistical analysis:

Data were reported as a frequency (%), median (Interquartile Range), or mean ± standard deviation as appropriate. Comparisons of EWI and ECG predictions to electrophysiology study and ablation results are shown on correlation maps. Heat maps of the correlation tables were generated using GraphPad Prism (version 7.03 for Windows, GraphPad Software, La Jolla California USA). EWI and ECG localization performances were also quantified with general accuracy and segment-specific positive predictive value and sensitivity analysis.

Results:

Between March 2017 and May 2018, 15 pediatric patients with ventricular pre-excitation on 12-lead ECG were consented for the study. All presented for ablation of ventricular pre-excitation at the Columbia University Medical Center pediatric electrophysiology laboratory. All 15 patients underwent transthoracic imaging with a trained sonographer. One patient was excluded for the inability to image the entire ventricular myocardium due to a poor acoustic window. The mean age of the cohort was 13.8 ± 2.8 years and 50% were male. Baseline characteristics of the patients are shown in Table 1. Six patients also underwent EWI scans after their catheter ablation procedures.

Table 1.

Patient Characteristics

	N = 14
Male	7 (50.0%)
Age (mean)	13.8 ± 2.8 years
On Antiarrhythmic Medication during EWI	0 (0.0%)
Height (mean)	158.5 ± 16.8 cm
Weight (mean)	60.8 ± 24.0 kg
Body Surface Area (mean)	1.63 ± 0.4 m2
Baseline Intervals
PR (mean)	97.4 ± 19.0 ms
QRS (mean)	115.6 ± 19.4 ms
AH (mean)	63.1 ± 14.5 ms
HV (mean)	11.8 ± 8.9 ms

Accessory Pathways:

Catheter mapping and ablation demonstrated a single AP in all 14 included patients. Specific locations based on our template (as seen in Figure 1e) included 3 left lateral, 2 left posterolateral, 5 posteroseptal, 1 anteroseptal, 1 right posterolateral, 1 right anterior, and 1 fasciculoventricular pathway with the earliest ventricular activation in the mid-septal RV. The identified fasciculoventricular pathway was not ablated. Of the 13 patients for whom ablation was attempted, all 13 APs (100%) were successfully ablated. The patient with the anteroseptal pathway was initially not ablated secondary to mechanical disruption of the pathway preventing accurate intracardiac mapping. He subsequently returned to the laboratory and was successfully ablated on the second attempt. Ablation was performed with radiofrequency current in 12 patients and with cryoablation technique in 1 patient. Trans-septal puncture was performed on six patients. Median fluoroscopy time was 0.3 (0.1–3.5) minutes and dose of radiation was 13.2 (7.0–70.0) µGym² and one patient underwent ablation without fluoroscopy. The means and ranges of PR, QRS, AH, and HV intervals as determined by baseline measurements in the electrophysiology laboratory are also described in Table 1.

Electromechanical Wave Imaging and ECG predictions:

EWI predicted 14/14 (100%) of the AP locations by correctly localizing the areas of earliest ventricular activation using the segments described in the methods above. Examples of EWI isochrones are shown in the following figures: left lateral AP before and after ablation in Figure 2, right posterolateral AP before and after ablation in Figure 3, a posteroseptal AP before ablation in Figure 4, and a fasciculoventricular AP in Figure 5.

Figure 2: EWI isochrones of a 7-year-old female with a left lateral pathway (i) before and (ii) after successful radiofrequency ablation.

Baseline intervals in the electrophysiology laboratory showed PR: 75 ms QRS: 93 ms AH: 61 ms HV: 1 ms. For all isochrones red indicates earliest activation and blue indicates latest. (i) a) Four 2D EWI isochrones of the ventricles prior to catheter ablation showing earliest area of activation in the lateral LV. 2 cm scale bars shown for spatial resolution and single lead ECG obtained with EWI acquisition are included; (i) b) Anterior view of the 3D-rendered EWI isochrone prior to catheter ablation and color bar for activation timings; (i) c) LAO cross-section of the previous 3D-rendered EWI isochrone at the valve level (TV: Tricuspid Valve, MV: Mitral Valve); (i) d) Electroanatomic map in LAO view showing superior vena cava (SVC), right atrium (RA), coronary sinus (CS), His site (yellow dot), and the site of successful ablation in the lateral LV (red dot); (i) e) 12-lead ECG prior to catheter ablation. (ii) a) Four 2D EWI isochrones of the ventricles after catheter ablation showing earliest area of activation in the septum; (ii) b) Anterior view of the 3D-rendered EWI isochrone after catheter ablation showing normal sinus activation of the ventricles and color bar for activation timings; (ii) c) LAO cross-section of the 3Drendered EWI isochrone at the valve level after catheter ablation; (ii) d) 12-lead ECG obtained after successful catheter ablation.

Figure 3: EWI isochrones of a 12-year-old female with a right lateral AP (i) before and (ii) after successful radiofrequency ablation.

Baseline intervals in the electrophysiology laboratory showed PR: 101 ms QRS: 116 ms AH: 85 ms HV: 10 ms. In all isochrones, red indicates earliest activation and blue indicates latest. (i) a) Anterior view of the 3D-rendered EWI isochrone prior to catheter ablation showing earliest activation in the lateral RV. 2 cm scale bars shown for spatial resolution and single lead ECG obtained with EWI acquisition are included; (i) b) Posterior view of the 3D-rendered EWI isochrone prior to catheter ablation; (i) c) LAO cross-section of the previous 3D-rendered EWI isochrones at the valve level (TV: Tricuspid Valve, MV: Mitral Valve) and color bar for activation timings; (i) d) 12-lead ECG prior to catheter ablation (i) e) Electroanatomic map in LAO view showing superior vena cava (SVC), right atrium (RA), inferior vena cava (IVC), coronary sinus (CS), His cloud (yellow dots), and the site of successful ablation in the posterolateral RA (red dot). (ii) a) Anterior view of the 3D-rendered EWI isochrone after catheter ablation showing normal sinus activation of the ventricles; (ii) b) Posterior view of the 3D-rendered EWI isochrone after catheter ablation showing normal sinus activation of the ventricles; (ii) c) LAO cross-section of the 3D-rendered EWI isochrone at the valve level after catheter ablation and color bar for activation timings.

Figure 4: EWI isochrones of a 16-year-old male with a right posteroseptal AP before radiofrequency ablation.

Baseline intervals in the electrophysiology laboratory showed PR: 93 ms QRS: 143 ms AH: 60 ms HV: 8 ms. For all isochrones red indicates earliest activation and blue indicates latest. (a) Anterior view of the 3D-rendered EWI isochrone prior to catheter ablation showing earliest activation in the right posteroseptal area. The 1-lead ECG obtained with EWI acquisition is included, as well as 2 cm scale bars for spatial resolution; (b) LAO cross-section of the previous 3D-rendered EWI isochrones at the valve level (TV: Tricuspid Valve, MV: Mitral Valve) and color bar for activation timings; (c) Electroanatomic map in LAO view showing superior vena cava (SVC), right atrium (RA), inferior vena cava (IVC), Coronary Sinus (CS), His cloud (yellow dots), and the site of successful ablation in the posteroseptal RA (red dot); (d) 12-lead ECG prior to catheter ablation.

Figure 5: EWI isochrones of a 17-year-old female with a fasciculoventricular AP prior to catheter ablation.

Baseline intervals in the electrophysiology laboratory showed PR: 121 ms QRS: 93 ms AH: 70 ms HV: 15 ms. For all isochrones red indicates earliest activation and blue indicates latest. (a) Anterior view of the 3D-rendered EWI isochrone prior to catheter ablation. No definitive area of earliest activation can be identified. 2 cm scale bars for spatial resolution and 1-lead ECG obtained with EWI acquisition are included; (b) Coronal slice of the previous 3D-rendered isochrone. Earliest activation is seen in the mid septal RV. Color bar for activation timings is included. The small gap seen in the LV apex results from a small sector of myocardium that was unable to be imaged in the 2D 3-chamber view, and therefore could not be used during the 3D interpolation as described in the methods; (c) Cross section of the 3D-rendered isochrone at the level of the mid ventricles. The black dashed line displayed on the coronal slice (b) corresponds to the exact level of the cross section; (d) 12-lead ECG acquired prior to catheter ablation.

ECG analysis correctly predicted 11/14 (78.6%) of the AP locations using both the Boersma et al. and Arruda et al. algorithms respectively (predictions in immediately adjacent segments were considered correct). It should be noted that most algorithmic analyses, including these, do not include segments distal to the atrioventricular rings, and therefore are not applicable for prediction of the fasciculoventricular pathway.(5,6)

Correlation heat maps of AP location prediction with EWI vs ECG are shown in Figure 6. More quantitatively, positive predictive value and sensitivity analysis is provided in Table 2 for each ventricular segment and quantifies the AP localization performances of EWI versus both Boersma and Arruda ECG algorithms.

Figure 6: Correlation heat maps comparing EWI and ECG pathway localizations to intracardiac study results.

Correlation heat maps illustrating the accuracy of EWI and clinician interpretation of ECG for localization of the imaged APs (includes 10 AV ring segments as well as location of fasciculoventricular). (a) Table showing confirmed AP locations from catheter mapping (columns) compared with EWI isochrone AP location predictions (rows). (b) Table showing intracardiac localization of APs (columns) compared with Boersma et al. AP location predictions (rows). (c) Table showing intracardiac localization of APs (columns) compared with Arruda et al. AP location predictions (rows). Green represents perfect predictions, while yellow illustrates predictions in adjacent segments, and red displays wrong predictions. The numbers written in the cells correspond to the number of predicted AP for each ventricular segment. EWI correctly predicted 100% of the AP locations. When considering adjacent segments as correct prediction, the Boersma et al. and Arruda et al. algorithms correctly predicted 78.6% of the AP locations, while when being conservative (excluding yellow cells), only 50% and respectively 57.1% of the predictions were correct.

Table 2.

EWI vs ECG performance for AP localization

AP localization methods	Global accuracy	Ventricular segments
		ANT SEPT		POST SEPT		Fasciculo-ventricular		Left LAT		Left POST LAT		Right LAT		Right ANT
		PPV	S	PPV	S	PPV	S	PPV	S	PPV	S	PPV	S	PPV	S
EWI	100%	1	1	1	1	1	1	1	1	1	1	1	1	1	1
Boersma	50% 78.6%*	0.25	1	1	0.4	0	0	0.75	1	0	0	0.33	1	0	0
Arruda	57.1% 78.6%*	0.33	1	0.75	0.6	0	0	0.67	0.67	0	0	0.5	1	1	1

PPV stands for Positive Predictive Value, while S stands for Sensitivity

^*When prediction in immediately adjacent segment is considered correct

Complications:

There were no complications during EWI scans and no major complications during catheter ablations.

Discussion:

In this cohort, EWI was capable of both localizing and visualizing the earliest ventricular activation in 14/14 included patients prior to the catheter ablation procedures. The patients were selected because they were presenting for catheter ablation. EWI localization was more accurate than ECG analysis with two different algorithms in our cohort.

The safety and efficacy of WPW ablation is well documented, but approximately 6% of ablations are still unsuccessful. This is variable by pathway location, from a 98% success rate for left free wall pathways to 88–89% for septal pathways.(3) Complications from catheter ablation of APs are rare but can still occur. In addition, the risks of WPW ablation can vary by location, such as AV block in septal pathways, complications from trans-septal puncture in left-sided ablation, and differences in fluoroscopy and anesthesia times based on pathway location. Some less common pathways, such as the fasciculoventricular AP, do not require catheter ablation at all. Having knowledge of the location of the pathway is crucial for both planning of catheter ablation and patient counseling prior to the procedure. Adding EWI to the standard 12-lead ECG has the potential to increase the accuracy of AP localization prior to catheter ablation procedures.

In this cohort, EWI was capable of localizing APs in a variety of locations to an approximately 1–2 cm area of myocardium in each case (see scale bars on Figure 2–5). EWI succeeded with a high number of anatomic segments surrounding the atrioventricular rings, which was consistent with or greater than 12-lead ECG algorithms (10 segments at the level of the atrioventricular rings for EWI in this study, as seen in Figure 1e, compared to 8 for the Boersma et al. algorithm and 10 for the Arruda et al. algorithm).(4–6,8) In addition, EWI was able to correctly identify the earliest area of ventricular pre-excitation from a fasciculoventricular pathway. The latter was localized distal to the AV ring in the mid ventricular septum, and no current AP localization algorithm would predict this location. An advantage of EWI is its ability to locate pre-excitation in ventricular myocardium below the level of the atrioventricular rings. EWI has also been shown capable of localizing premature ventricular contractions in a single patient and accurately illustrating the propagation of atrial activation in normal sinus rhythm. (18)

The exact spatial resolution is dependent on both the quality of imaging and the location of the pathway, and is illustrated on a case by case basis with scale bars in each figure. When using 2D echocardiography, the location of the myocardial points imaged can affect the specificity of the EWI results. For example, as seen in the methods (Figure 1d), there are eight image samples around the left ventricle but only four in the right ventricle. This inherently means that the spatial resolution of EWI will be higher for left sided accessory pathways. Nevertheless, EWI was capable of localizing all pathways regardless of location, assuming good quality echocardiography.

The degree of pre-excitation did not affect the accuracy of EWI in this cohort. While most patients were substantially pre-excited (as described in Table 1), the presence of less obvious pre-excitation did not affect the resulting localization. For example, one patient with a left posterolateral pathway (Baseline Intervals: PR: 118 ms QRS: 103 ms AH: 46 HV: 28) was successfully imaged and localized with EWI, suggesting the usefulness of EWI in patients with minimal pre-excitation.

Limitations of EWI:

EWI is primarily limited by its reliance on high quality ultrasound imaging. The myocardium is required to be fully visible in the views before EWI processing can be applied. The one excluded patient in which EWI could not be performed was a female adolescent, where breast tissue resulted in a difficult acoustic window and the entire ventricular myocardium could not be imaged. Even with high quality echocardiography, certain anatomical areas are more difficult to image in multiple views. For example, the right ventricle has half the image sampling as the left ventricle, as seen in the methods (Figure 1d). Since EWI relies on having the area of interest within view, this might limit the spatial resolution or localization altogether. This under sampling phenomenon of 2D echocardiography could potentially be overcome by using EWI with true 3D ultrasound, which would allow for imaging of all myocardium within the field of view. This has currently been shown feasible in open-chest canine studies and healthy volunteers.(26) EWI is dependent on the presence of anterograde ventricular pre-excitation in order to detect the location of the AP. As demonstrated in this study, even minimal pre-excitation is sufficient, but this technique is obviously not applicable in patients with concealed APs.

Limitations of Study Design:

This is a study in a small cohort of 15 WPW patients imaged with EWI. This study demonstrates the technique and suggests its potential uses, but the limited sample size prevents analysis on clinical measures, and this study does not comment on the effect of EWI on clinical outcomes. The blinding of the treating electrophysiologist to the EWI results prevents analysis of EWIs effect on the procedures. Given the limited number of patients, certain pathway locations were not included. In addition, this is a single center study of pediatric patients. This was a select population deemed suitable and selected for catheter ablation, and therefore these results may not be generalizable to all patients with ventricular pre-excitation. Given the small sample size, further study is needed to both validate EWI and determine its effect in clinical practice.

Conclusion:

Electromechanical Wave Imaging was shown to be capable of consistently localizing accessory pathways in variable locations more frequently than the 12-lead ECG in a pediatric patient population. A higher correlation was obtained between the electroanatomic mapping results and EWI predictions than against ECG predictions. EWI isochrones can also provide more detailed anatomical visualization. These findings indicate that this modality has potential to better inform a treating electrophysiologist for pre-procedure planning.

Abbreviations:

AP

Accessory Pathway

EWI

Electromechanical Wave Imaging

WPW

Wolff-Parkinson-White