Electrocardiographic body surface potential mapping in the Wolff-Parkinson-White syndrome. Noninvasive determination of the ventricular insertion sites of accessory atrioventricular connections

Estimation of the accessory pathway location of the manifest Wolf-Parkinson-White syndrome using synthesized right-sided chest leads

PURPOSE

The classification using QRS morphology of V1 lead is a useful simple predictor of accessory pathway location (type A, R or Rs pattern; type B, rS pattern; type C, QS or Qr pattern), but often leads to misdiagnosis of accessory pathway location, especially in types B and C. The synthesized 18-lead electrocardiography (ECG) derived from standard 12-lead ECG can provide virtual waveforms of right-sided chest leads. This study aimed to evaluate the usefulness of the right-sided chest lead ECG for prediction of accessory pathway location.

METHODS

This retrospective study included 44 patients in whom successful ablation of manifest Wolff-Parkinson-White (WPW) syndrome was performed. Synthesized ECG waveforms were automatically generated, and ECG data obtained before the procedure.

RESULTS

There were 26, 4, and 14 patients with left, right, and septal accessory pathways, respectively. All left accessory pathway cases have type A in V1 and syn-V4R leads. Of the 4 right accessory pathway cases, 2 have type B in V1 and syn-V4R leads. Other 2 of 4 cases have type C. In V1 lead, 5 of 14 septal accessory pathway cases have type C, 7 of 14 cases have type B, and 2 of 14cases have type A. In syn-V4R lead, all 14 septal accessory pathway cases have type C. The QRS morphology of V1 and syn-V4 leads could predict the site of accessory pathway with overall accuracy of 79% and 95%, respectively.

CONCLUSIONS

QRS morphology of syn-V4R lead may be useful for predicting accessory pathway location of manifest WPW syndrome.

Temporal Sparse Promoting Three Dimensional Imaging of Cardiac Activation

A new Cardiac Electrical Sparse Imaging (CESI) technique is proposed to image cardiac activation throughout the three-dimensional myocardium from body surface electrocardiogram (ECG) with the aid of individualized heart-torso geometry. The sparse property of cardiac electrical activity in the time domain is utilized in the temporal sparse promoting inverse solution, one formulated to achieve higher spatial-temporal resolution, stronger robustness and thus enhanced capability in imaging cardiac electrical activity. Computer simulations were carried out to evaluate the performance of this imaging method under various circumstances. A total of 12 single site pacing and 7 dual sites pacing simulations with artificial and the hospital recorded sensor noise were used to evaluate the accuracy and stability of the proposed method. Simulations with modeling error on heart-torso geometry and electrode-torso registration were also performed to evaluate the robustness of the technique. In addition to the computer simulations, the CESI algorithm was further evaluated using experimental data in an animal model where the noninvasively imaged activation sequences were compared with those measured with simultaneous intracardiac mapping. All of the CESI results were compared with conventional weighted minimum norm solutions. The present results show that CESI can image with better accuracy, stability and stronger robustness in both simulated and experimental circumstances. In sum, we have proposed a novel method for cardiac activation imaging, and our results suggest that the CESI has enhanced performance, and offers the potential to image the cardiac activation and to assist in the clinical management of ventricular arrhythmias.

Noninvasive diagnostic mapping of supraventricular arrhythmias (Wolf-Parkinson-White syndrome and atrial arrhythmias)

The 12-lead electrocardiogram has limited value in precisely identifying the origin of focal or critical component of reentrant arrhythmias during supraventricular arrhythmias, as well as precisely locating accessory atrioventricular conduction pathways. Because of these limitations, efforts have been made to reconstruct epicardial activation sequences from body surface measurements obtained noninvasively. The last decade has registered significant progress in obtaining clinically useful data from the attempts to noninvasively map the epicardial electrical activity. This article summarizes the recent advances made in this area, specifically addressing the clinical outcomes of such efforts relating to atrial arrhythmias and Wolf-Parkinson-White syndrome.

How many ECG leads do we need?

The number of leads needed in clinical electrocardiography depends on the clinical problem to be solved. The standard 12-lead ECG is so well established that alternative lead systems must prove their advantage through well-conducted clinical studies to achieve clinical acceptance. Certain additional leads seem to add valuable information in specific patient groups. The use of a large number of leads (eg, in body surface potential mapping) may add clinically relevant information, but it is cumbersome and its clinical advantage is yet to be proven. Reduced lead sets emulate the 12-lead ECG reasonably well and are especially advantageous in emergency situations.

Spatiotemporal characterization of paced cardiac activation with body surface potential mapping and self-organizing maps

In this study self-organizing maps (SOM) were utilized for spatiotemporal analysis and classification of body surface potential mapping (BSPM) data. Altogether 86 cardiac depolarization (QRS) sequences paced by a catheter in 18 patients were included. Spatial BSPM distributions at every 5 ms over the QRS complex were first presented to an untrained SOM. The learning process of the SOM units organized the maps in such a way that similar BSPMs are represented in particular areas of the SOM network. Thereafter, time trajectories and distance maps were created on the trained SOM from sequential maps in a selected paced QRS. The trajectories and distance maps can be applied as such for the localization of abnormal ventricular activation, as well as quantitative input for statistical classification. The results indicate that the method has potential for locating endocardial sites of abnormal ventricular activation, despite the patient material being too limited to provide a reliable statistical evaluation of the source localization accuracy.

Dobutamine stress surface mapping of myocardial ischemia in Kawasaki disease

BACKGROUND

To detect and localize myocardial ischemia, a method that does not require physical exertion is sometimes needed in children with Kawasaki disease.

METHODS

Dobutamine stress body surface mapping was performed in 115 children with a history of Kawasaki disease (58 without coronary artery lesions, 40 who had coronary lesions without myocardial ischemia and 17 with myocardial ischemia). The maximum infusion rate of dobutamine was 30 microg/kg per min. Myocardial ischemia was diagnosed by the presence of an area of hypoperfusion on scintigraphy at rest and/or an increase in hypoperfusion during a dobutamine stress test compared with resting scintigraphy. We studied the number of leads that showed significant ST depression on the isopotential map (nST), the number of the row containing the lead with the smallest negative value on the isointegral map (I(min)), and the localization of myocardial ischemia on the isointegral map. Based on findings in patients without coronary artery lesions, we defined the criteria for detecting myocardial ischemia as nST > or = 1 and I(min) < or = 4.

RESULTS

The sensitivity of detecting myocardial ischemia was 94.1% using nST and 41.7% using I(min), while the specificity of these methods was 98.9 and 96.9%, respectively. The localization of myocardial ischemia on stress body surface mapping was 100% concordant with that determined by stress myocardial scintigraphy.

CONCLUSIONS

Dobutamine stress body surface mapping for the detection of myocardial ischemia is a non-invasive, more convenient and repeatable test compared with exercise myocardial scintigraphy and it is a more objective test compared with exercise echocardiography. Dobutamine stress body surface mapping is useful for the identification and localization of silent myocardial ischemia in pediatric patients with Kawasaki disease, especially those who cannot perform tests involving physical exercise.

A noninvasive imaging modality for cardiac arrhythmias

BACKGROUND

The last decade witnessed an explosion of information regarding the genetic, molecular, and mechanistic basis of heart disease. Translating this information into clinical practice requires the development of novel functional imaging modalities for diagnosis, localization, and guided intervention. A noninvasive modality for imaging cardiac arrhythmias is not yet available. Present electrocardiographic methods cannot precisely localize a ventricular tachycardia (VT) or its key reentrant circuit components. Recently, we developed a noninvasive electrocardiographic imaging modality (ECGI) that can reconstruct epicardial electrophysiological information from body surface potentials. Here, we extend its application to image reentrant arrhythmias.

METHODS AND RESULTS

Epicardial potentials were recorded during VT with a 490 electrode sock during an open chest procedure in 2 dogs with 4-day-old myocardial infarctions. Body surface potentials were generated from these epicardial potentials in a human torso model. Realistic geometry errors and measurement noise were added to the torso data, which were then used to noninvasively reconstruct epicardial isochrones, electrograms, and potentials with excellent accuracy. ECGI reconstructed the reentry pathway and its key components, including (1) the central common pathway, (2) the VT exit site, (3) lines of block, and (4) regions of slow and fast conduction. This allowed for detailed characterization of the reentrant circuit morphology.

CONCLUSIONS

ECGI can noninvasively image arrhythmic activation on the epicardium during VT to identify and localize key components of the arrhythmogenic pathway that can be effective targets for antiarrhythmic intervention.

Bioelectromagnetic localization of a pacing catheter in the heart

The accuracy of localizing source currents within the human heart by non-invasive magneto- and electrocardiographic methods was investigated in 10 patients. A non-magnetic stimulation catheter inside the heart served as a reference current source. Biplane fluoroscopic imaging with lead ball markers was used to record the catheter position. Simultaneous multichannel magnetocardiographic (MCG) and body surface potential mapping (BSPM) recordings were performed during catheter pacing. Equivalent current dipole localizations were computed from MCG and BSPM data, employing standard and patient-specific boundary element torso models. Using individual models with the lungs included, the average MCG localization error was 7+/-3 mm, whereas the average BSPM localization error was 25+/-4 mm. In the simplified case of a single homogeneous standard torso model, an average error of 9+/-3 mm was obtained from MCG recordings. The MCG localization accuracies obtained in this study imply that the capability of multichannel MCG to locate dipolar sources is sufficient for clinical purposes, even without constructing individual torso models from x-ray or from magnetic resonance images.

Prediction of accessory pathway locations in Wolff-Parkinson-White syndrome with body surface potential Laplacian maps . A simulation study

An electrocardiographic computer simulation was conducted to study the feasibility of predicting accessory pathway locations in Wolff-Parkinson-White (WPW) syndrome with body surface potential Laplacian maps. Three-dimensional, realistically-shaped heart and torso models were used. Ten accessory pathways (APs) around the atrioventricular ring corresponding to Gallagher et al. were set in the heart model, and body surface Lapacian and potential maps of WPW syndrome with single or multiple APs were simulated and compared to each other. In simulations with a single AP in the anterior walls, the maximum-minimum pairs in Laplacian maps appeared to be similar to those in potential maps with respect to their locations and orientations, but the maximum-minimum pairs in Laplacian maps were sharper and more localized than in potential maps. In simulations with a posterior AP or multiple APs, the maximum-minimum pairs in the Laplacian maps showed features correlative to the AP locations, but no such features were found in potential maps. These results suggest the possibility of using Laplacian maps, as a non-invasive method for predicting accessory pathways locations in WPW syndrome.

Spatial resolution of body surface potential maps and magnetic field maps: a simulation study applied to the identification of ventricular pre-excitation sites

The spatial resolution of body surface potential maps (BSPMs) and magnetic field maps (MFMs) is investigated by means of an anatomically accurate computer model of the human ventricular myocardium. BSPMs and MFMs are calculated for the simulated activation sequences initiated at 35 pre-excitation sites located along the atrioventricular (AV) ring of the epicardium. Changes in the BSPMs and MFMs corresponding to different pre-excitation sites are quantified in terms of the correlation coefficient r. The spatial resolution (selectivity) for a given pre-excitation site is defined as the half-distance between those neighbouring locations at which morphological features of maps, in terms of r, become distinct (r < 0.95). It is found that, at 28 ms after the onset of pre-excitation and with no noise added, this distance +/- SD, for all sites along the AV ring for the 117-lead BSPMs, is 0.83 +/- 0.32 cm, and for the 64-lead and 128-lead MFMs it is 1.54 +/- 0.84 cm and 1.15 +/- 0.43 cm, respectively. The findings suggest that, when features of non-invasively recorded electrocardiographic and magnetocardiographic map patterns are used for identifying accessory pathways in patients suffering from WPW syndrome, BSPMs are likely to provide more detailed information for guiding the ablative treatment than MFMs. For some sites MFMs provide more information. Both modalities may provide additional assistance to the cardiologist in locating the site of the accessory pathway.

[Present state and future of magnetocardiographic localization]

The magnetic fields caused by the human heart's electrical excitation can be recorded without contact over the body surface to obtain the "magnetocardiogram" (MCG). As compared to the conventional electrocardiogram (ECG), the magnetic fields are influenced far less by the conductive properties of the body tissues, so that the MCG permits a more direct and accurate analysis of cardiac electrical excitation. Most important, the MCG allows an exact localization of the underlying electrical activity, based on the recorded magnetic field distribution. For localization, the MCG does not rely on pattern recognition algorithms such as the ECG, instead, a computational 3-D localization is performed using simplified source and volume conductor models. The spatial accuracy of this method, in combination with magnetic resonance imaging for anatomical assignment of the localization results, has been determined to be 10 to 15 mm for sources close to the body surface and 15 to 20 mm for sources in the posterior parts of the heart.Clinically, the magnetocardiogram can be applied for the non-invasive localization of accessory pathways in Wolff-Parkinson-White syndrome, and of ventricular ectopies (PVC and VT). Especially in combination with a subsequent interventional treatment by catheter ablation, the method may improve the clinical management of these conditions.While the registration techniques are standardized in a way that permits routine clinical application, the data evaluation has to be optimized and simplified before this method can be completely handed over for physicians to use.

Body surface mapping criteria for diagnosis of left ventricular hypertrophy associated with complete right bundle branch block

The standard electrocardiographic (ECG) criteria for left ventricular hypertrophy are unreliable in patients with complete right bundle branch block. This study was undertaken to formulate criteria for diagnosing these patients by using body surface mapping. The echocardiographic left ventricular mass was calculated by the Penn method from M-mode measurements. Of 56 patients, 27 were defined as having left ventricular hypertrophy with a left ventricular mass of 215 g or more. Isopotential and isointegral maps of the QRS complex were observed. The QRS isointegral maps were separated into two parts at the end of the downstroke of the initial R wave of vector spatial magnitude. The body surface mapping criteria with the highest sensitivity were EPmax (maximum of early part of the QRS) 45 microV.s or greater (sensitivity 93%, specificity 90%), EPmax/d (EPmax averaged by EP duration) 0.8 mV or greater (sensitivity 93%, specificity 97%), and Max (initial maximum) 2.2 mV or greater (sensitivity 89%, specificity 90%). These results suggest that body surface mapping is a useful technique in diagnosing patients with left ventricular hypertrophy and right bundle branch block.

Body surface potential mapping of a patient with Wolff-Parkinson-White syndrome with two accessory pathways and two atrial pacemaker complexes

As part of an ongoing research protocol, a patient with Wolff-Parkinson-White syndrome underwent body surface potential mapping and electrophysiologic studies before radiofrequency ablation therapy. Careful analysis of the body surface potential mapping data made it possible to distinguish four different map sequences representing four different cardiac complexes. Analysis of these maps is consistent with two accessory pathways, with the additional pathology of two distinct atrial pacemaker sites. A right anterosuperior pathway was found to conduct continuously. The second pathway is consistent with a right inferior pathway conducting intermittently. The analysis demonstrates the type of information that can be extracted from body surface potential maps, even in the presence of complex pathologies.

Evaluation of the non-invasive localization accuracy of cardiac arrhythmias attainable by multichannel magnetocardiography (MCG)

The accuracy of multichannel magnetocardiography (MCG) for the non-invasive localization of cardiac arrhythmias was investigated. A non-magnetic catheter was used in phantom studies and for cardiac pacing of 6 patients. In a clinical setting, 32 patients with WPW-syndrome, 37 patients with premature ventricular complexes and 12 patients with ventricular tachycardia were studied and the MCG results compared to reference methods, including invasive electrophysiological mapping. Phantom and pacing studies demonstrated the spatial localization accuracy to be better than 15 mm for a dipole-to-dewar distance below 15 cm. In all patients with structural cardiac disease, the ectopic focus was localized at the margin of the damaged area, serving as a proof of MCG localization. Invasive mapping confirmed the MCG result whenever performed (42 patients). In 11 patients (9 WPW, 2 VT) the MCG localization result was verified by successful HF catheter ablation as a gold standard. MCG permits the non-invasive localization of cardiac arrhythmias with high spatial accuracy. MCG guided HF catheter ablation constitutes a new concept of non-invasive localization and minimally invasive causal therapy.

Regular wide QRS complex tachycardia during atrial fibrillation in a patient with preexcitation syndrome: a case report

We report an unusual case of a relatively regular wide QRS complex tachycardia alternating with periods of an irregular narrow QRS complex tachycardia during atrial fibrillation in a patient with Wolff-Parkinson-White syndrome. Both tachycardias resulted from atrial fibrillation, the wide QRS complex tachycardia being due to 2:1 AV conduction of a type I atrial fibrillation across a posteroseptal accessory AV connection.

Clinical applications of body surface potential mapping

Accumulated evidence suggests that the electrocardiographic information provided by the standard 12-lead electrocardiogram can be improved by use of multilead electrocardiograms. The clinical utility of body surface potential mapping is related to the selective regional information provided by the increased number of leads. That clinical utility includes such things as improved localization of accessory pathways in preexcitation syndromes, improved localization of pacing sites within the ventricles, localization of late potentials, and improved recognition of acute myocardial ischemia. Recording equipment and interpretation schemes are available to make possible more widespread application of potential mapping.

Electrocardiographic inverse solution for ectopic origin of excitation in two-dimensional propagation model

Inverse calculations were examined that sought the origin of a cardiac ectopic excitation sequence. Cardiac anatomy and its geometric relationships to sites on the body surface were adapted from human cross-sectional images to form a two-dimensional model, which included ventricular muscle and a primitive conduction system. The surrounding volume conductor was modelled in a simplified way as unbounded, homogeneous and isotropic. In a series of tests, one ectopic origin was designated the 'true' origin. The ECG for this true origin was compared to ECGs for 197 ectopic 'trial' origins, and differences between the wave forms for true versus trial origins were determined. Core issues were the magnitudes of changes in ECG wave forms as a function of the site of origin, whether these changes were sufficient to imply uniqueness, and what spatial resolution might be expected, in the presence of realistic noise levels. For a noise level of 10 microV RMS, the origin of excitation was localised to a single region of the muscle using one wave form from the body surface, with a resolution of 10 mm. The resolution was not improved significantly with a second electrode on the body surface, but was substantially improved with an endocardial electrode.

Diagnosis and localization of accessory pathways

The WPW syndrome is a curable disease. The evolution of nonpharmacological methods of accessory pathway ablation has had a significant impact on management strategies in patients with arrhythmias mediated by accessory pathways. Despite an incidence of preexcitation in the general population of 0.1% to 0.3%, curative therapy is underutilized. This review has highlighted the traditional and newer methods of diagnosing and localizing accessory pathways. The number of patients benefiting from definitive therapy will parallel increased physician awareness of these methods.