Feasibility of a noncontact catheter for endocardial mapping of human ventricular tachycardia

Non-Contact Intracardiac Potential Mapping Using Mesh-Based and Meshless Inverse Solvers

Atrial fibrillation (AF) is the most common cardiac dysrhythmia and percutaneous catheter ablation is widely used to treat it. Panoramic mapping with multi-electrode catheters has been used to identify ablation targets in persistent AF but is limited by poor contact and inadequate coverage of the left atrial cavity. In this paper, we investigate the accuracy with which atrial endocardial surface potentials can be reconstructed from electrograms recorded with non-contact catheters. An in-silico approach was employed in which “ground-truth” surface potentials from experimental contact mapping studies and computer models were compared with inverse potential maps constructed by sampling the corresponding intracardiac field using virtual basket catheters. We demonstrate that it is possible to 1) specify the mixed boundary conditions required for mesh-based formulations of the potential inverse problem fully, and 2) reconstruct accurate inverse potential maps from recordings made with appropriately designed catheters. Accuracy improved when catheter dimensions were increased but was relatively stable when the catheter occupied >30% of atrial cavity volume. Independent of this, the capacity of non-contact catheters to resolve the complex atrial potential fields seen in reentrant atrial arrhythmia depended on the spatial distribution of electrodes on the surface bounding the catheter. Finally, we have shown that reliable inverse potential mapping is possible in near real-time with meshless methods that use the Method of Fundamental Solutions.

Intracardiac Inverse Potential Mapping Using the Method of Fundamental Solutions

Introduction: Atrial fibrillation (AF) is the most prevalent cardiac dysrhythmia and percutaneous catheter ablation is widely used to treat it. Panoramic mapping with multi-electrode catheters can identify ablation targets in persistent AF, but is limited by poor contact and inadequate coverage. Objective: To investigate the accuracy of inverse mapping of endocardial surface potentials from electrograms sampled with noncontact basket catheters. Methods: Our group has developed a computationally efficient inverse 3D mapping technique using a meshless method that employs the Method of Fundamental Solutions (MFS). An in-silico test bed was used to compare ground-truth surface potentials with corresponding inverse maps reconstructed from noncontact potentials sampled with virtual catheters. Ground-truth surface potentials were derived from high-density clinical contact mapping data and computer models. Results: Solutions of the intracardiac potential inverse problem with the MFS are robust, fast and accurate. Endocardial surface potentials can be faithfully reconstructed from noncontact recordings in real-time if the geometry of cardiac surface and the location of electrodes relative to it are known. Larger catheters with appropriate electrode density are needed to resolve complex reentrant atrial rhythms. Conclusion: Real-time panoramic potential mapping is feasible with noncontact intracardiac catheters using the MFS. Significance: Accurate endocardial potential maps can be reconstructed in AF with appropriately designed noncontact multi-electrode catheters.

Treatment of brief episodes of highly symptomatic supraventricular and ventricular arrhythmias: a methodological review

INTRODUCTION

Patients with brief arrhythmias are a challenging group to treat effectively with catheter ablation. Current standard approaches for the localization and treatment of brief arrhythmias suffer from several limitations, including the lack of spatiotemporal stability and adequate resolution. Recently, novel methods became available that open new perspectives and can be implemented both on the atrial and ventricular level to approach the diagnosis and treatment of these arrhythmias.

AREAS COVERED

In this paper, we demonstrate in each section a novel mapping modality that has a potential to approach arrhythmias considered unmappable in the past. After describing the method, we focused on the most important features of each system that makes mapping of short arrhythmias feasible. At the end of each section, we gave a short overview about necessary developments to improve the utility of these systems in the near future.

EXPERT OPINION

Treating brief episodes of tachycardias remains a challenge and can cause significant frustration for electrophysiologists. Although the broadening of the indication is clearly visible, currently available sequential mapping techniques often fail to map short-lived arrhythmias. New beneficial technological features permit the mapping of these previously considered unmappable arrhythmias, and offer a new perspective in their management.

Maximizing the Effectiveness of Ablation for Arrhythmias in the Congenital Heart Patients

Arrhythmias are common in adults with congenital heart disease and account for a large proportion of hospitalizations. The complex anatomical heterogeneity, often in the presence of a delicate hemodynamic system, presents a significant electrophysiological challenge. This review outlines current clinical practice and advances in maximizing the effectiveness of ablation for arrhythmias in congenital heart patients.

Three-dimensional dominant frequency mapping using autoregressive spectral analysis of atrial electrograms of patients in persistent atrial fibrillation

BACKGROUND

Areas with high frequency activity within the atrium are thought to be 'drivers' of the rhythm in patients with atrial fibrillation (AF) and ablation of these areas seems to be an effective therapy in eliminating DF gradient and restoring sinus rhythm. Clinical groups have applied the traditional FFT-based approach to generate the three-dimensional dominant frequency (3D DF) maps during electrophysiology (EP) procedures but literature is restricted on using alternative spectral estimation techniques that can have a better frequency resolution that FFT-based spectral estimation.

METHODS

Autoregressive (AR) model-based spectral estimation techniques, with emphasis on selection of appropriate sampling rate and AR model order, were implemented to generate high-density 3D DF maps of atrial electrograms (AEGs) in persistent atrial fibrillation (persAF). For each patient, 2048 simultaneous AEGs were recorded for 20.478 s-long segments in the left atrium (LA) and exported for analysis, together with their anatomical locations. After the DFs were identified using AR-based spectral estimation, they were colour coded to produce sequential 3D DF maps. These maps were systematically compared with maps found using the Fourier-based approach.

RESULTS

3D DF maps can be obtained using AR-based spectral estimation after AEGs downsampling (DS) and the resulting maps are very similar to those obtained using FFT-based spectral estimation (mean 90.23 %). There were no significant differences between AR techniques (p = 0.62). The processing time for AR-based approach was considerably shorter (from 5.44 to 5.05 s) when lower sampling frequencies and model order values were used. Higher levels of DS presented higher rates of DF agreement (sampling frequency of 37.5 Hz).

CONCLUSION

We have demonstrated the feasibility of using AR spectral estimation methods for producing 3D DF maps and characterised their differences to the maps produced using the FFT technique, offering an alternative approach for 3D DF computation in human persAF studies.

Catheter Ablation of Pediatric Focal Atrial Tachycardia: Ten-Year Experience Using Modern Mapping Systems

Experience of catheter ablation of pediatric focal atrial tachycardia (FAT) is still limited. There are data which were gathered prior to the introduction of modern 3D mapping and navigation systems into the clinical routine. Accordingly, procedures were associated with significant fluoroscopy and low success rates. The aim of this study was to present clinical and electrophysiological details of catheter ablation of pediatric FAT using modern mapping systems. Since March 2003, 17 consecutive patients <20 years underwent electrophysiological study (EPS) for FAT using the NavX(®) system (n = 7), the non-contact mapping system (n = 6) or the LocaLisa(®) system (n = 4), respectively. Radiofrequency was the primary energy source; cryoablation was performed in selected patients with a focus close to the AV node. In 16 patients, a total number of 19 atrial foci (right-sided n = 13, left-sided n = 6) could be targeted. In the remaining patient, FAT was not present/inducible during EPS. On an intention-to-treat basis, acute success was achieved in 14/16 patients (87.5 %) with a median number of 11 (1-31) energy applications. Ablation was unsuccessful in two patients due to an epicardial location of a right atrial focus (n = 1) and a focus close to the His bundle (n = 1), respectively. Median procedure time was 210 (84-332) min, and median fluoroscopy time was 13.1 (4.5-22.5) min. In pediatric patients with FAT, 3D mapping and catheter ablation provided improved clinical quality of care. Catheter ablation may be considered early in the course of treatment of this tachyarrhythmia in symptomatic patients.

On the efficiency and accuracy of the single equivalent moving dipole method to identify sites of cardiac electrical activation

We have proposed an algorithm to guide radiofrequency catheter ablation procedures. This algorithm employs the single equivalent moving dipole (SEMD) to model cardiac electrical activity. The aim of this study is to investigate the optimal time instant during the cardiac cycle as well as the number of beats needed to accurately estimate the location of a pacing site. We have evaluated this algorithm by pacing the ventricular epicardial surface and inversely estimating the locations of pacing electrodes from the recorded body surface potentials. Two pacing electrode arrays were sutured on the right and left ventricular epicardial surfaces in swine. The hearts were paced by the electrodes sequentially at multiple rates (120-220 bpm), and body surface ECG signals from 64 leads were recorded for the SEMD estimation. We evaluated the combined error of the estimated interelectrode distance and SEMD direction at each time instant during the cardiac cycle, and found the error was minimum when the normalized root mean square (RMS n ) value of body surface ECG signals reached 15 % of its maximum value. The beat-to-beat variation of the SEMD locations was significantly reduced (p < 0.001) when estimated at 15 % RMS n compared to the earliest activation time (EAT). In addition, the 5-95 % interval of the estimated interelectrode distance error decreased exponentially as the number of beats used to estimate a median beat increased. When the number of beats was 4 or larger, the 5-95 % interval was smaller than 3.5 mm (the diameter of a commonly used catheter). In conclusion, the optimal time for the SEMD estimation is at 15 % of RMS n , and at that time instant a median beat estimated from 4 beats is associated with a beat-to-beat variability of the SEMD location that is appropriate for catheter ablation procedures.

Techniques for automated local activation time annotation and conduction velocity estimation in cardiac mapping

Measurements of cardiac conduction velocity provide valuable functional and structural insight into the initiation and perpetuation of cardiac arrhythmias, in both a clinical and laboratory context. The interpretation of activation wavefronts and their propagation can identify mechanistic properties of a broad range of electrophysiological pathologies. However, the sparsity, distribution and uncertainty of recorded data make accurate conduction velocity calculation difficult. A wide range of mathematical approaches have been proposed for addressing this challenge, often targeted towards specific data modalities, species or recording environments. Many of these algorithms require identification of activation times from electrogram recordings which themselves may have complex morphology or low signal-to-noise ratio. This paper surveys algorithms designed for identifying local activation times and computing conduction direction and speed. Their suitability for use in different recording contexts and applications is assessed.

Biopsy of a complicated right atrial mass using CARTO 3-dimensional electro-anatomic mapping

We report the successful biopsy of a right atrial fatty mass using CARTO 3-dimensional electro-anatomic mapping fused with cardiac MRI. Fluoroscopic guidance within the cardiac chambers lacks precision and therefore risks geographical miss of the intended target and cardiac perforation. CARTO mapping fused with cardiac MRI facilitated precise navigation of the bioptome thereby ensuring a successful biopsy of the intended tissue while minimizing the risks of inadvertent trauma to adjacent tissue.

Organizational index mapping to identify focal sources during persistent atrial fibrillation

INTRODUCTION

Localized rotors have been implicated in the mechanism of persistent atrial fibrillation (AF). Although regions of highest dominant frequency (DF) on spectral analysis of the left atrium (LA) have been said to identify rotors, other mechanisms such as wavefront collisions will sporadically also generate an inconsistent distribution of high DF. We hypothesized that if drivers of AF were present, their distinctive spectral characteristics would result more from their temporal stability than their high frequency.

METHODS AND RESULTS

Ten patients with persistent AF underwent LA noncontact mapping. Following subtraction of far-field ventricular components, noncontact electrograms at 256 sites underwent fast Fourier transform. Mean absolute difference in DF between 5 sequential 7-second segments of AF was defined as the DF variability (DFV) at each site. Mean ratio of the DF and its harmonics to the total power of the spectrum was defined as the organizational index (OI). Mean DFV was significantly lower in organized areas (OI > 1 SD above mean) than at all sites (0.34 ± 0.04 vs 0.46 ± 0.04 Hz; P < 0.001). When organized areas were ablated during wide-area circumferential ablation, AF organized in remote regions (LA appendage ΔOI ablated vs unablated: +0.21 [0.06-0.41] vs -0.04 [-0.14-0.05]; P = 0.005).

CONCLUSIONS

At sites of organized activation, the activation frequency was also significantly more stable over time. This observation is consistent with the existence of focal sources, and inconsistent with a purely random activation pattern. Ablation of such regions is technically feasible, and was associated with organization of AF in remote atrial regions.

Radiofrequency catheter ablation therapy in the young: current status

Since 1989, when radiofrequency ablation was introduced into clinical practice for pediatric patients with supraventricular tachycardias, radiofrequency catheter ablation techniques have evolved as the treatment of choice for many forms of tachycardia in young patients. This review discusses the current status of ablation therapy for the four most common forms of supraventricular tachycardias in children, including tachycardias based on accessory atrioventricular pathways, atrioventricular nodal reentrant tachycardia, atrial ectopic tachycardia and the permanent form of junctional reciprocating tachycardia. In addition, the report will focus on the current status and limitations of ablation therapy of ventricular tachycardias and atrial reentry tachycardias in patients after surgical correction of congenital heart defects.

Distinctive patterns of dominant frequency trajectory behavior in drug-refractory persistent atrial fibrillation: preliminary characterization of spatiotemporal instability

INTRODUCTION

The role of substrates in the maintenance of persistent atrial fibrillation (persAF) remains poorly understood. The use of dominant frequency (DF) mapping to guide catheter ablation has been proposed as a potential strategy, but the characteristics of high DF sites have not been extensively studied. This study aimed to assess the DF spatiotemporal stability using high density noncontact mapping (NCM) in persAF.

METHODS AND RESULTS

Eight persAF patients were studied using NCM during AF. Ventricular far-field cancellation was performed followed by the calculation of DF using Fast Fourier Transform. Analysis of DF stability and spatiotemporal behavior were investigated including characteristics of the highest DF areas (HDFAs). A total of 16,384 virtual electrograms (VEGMs) and 232 sequential high density 3-dimensional DF maps were analyzed. The percentage of DF stable points decreased rapidly over time. Repetition or reappearance of DF values were noted in some instances, occurring within 10 seconds in most cases. Tracking the HDFAs' center of gravity revealed 3 types of propagation behavior, namely (i) local, (ii) cyclical, and (iii) chaotic activity, with the former 2 patterns accounting for most of the observed events.

CONCLUSIONS

DF of individual VEGMs was temporally unstable, although reappearance of DF values occurred at times. Hence, targeting sites of 'peak DF' from a single time frame is unlikely to be a reliable ablation strategy. There appears to be a predominance of local and cyclical activity of HDFAs hinting a potentially nonrandom temporally periodic behavior that provides further mechanistic insights into the maintenance of persAF.

Noncontact mapping to guide ablation of right ventricular outflow tract arrhythmias

BACKGROUND

There is limited data on outcomes after noncontact mapping (NCM)-guided right ventricular outflow tract (RVOT) ventricular arrhythmia (VA) ablation.

OBJECTIVES

To assess outcomes of NCM-guided RVOT VA ablation in a large cohort with extended follow-up, to determine optimal ablation site, and to analyze limitations of conventional mapping techniques.

METHODS

In consecutive patients undergoing RVOT VA ablation, 2 sites of early activation--earliest activation (EA) and breakout (BO) sites--were identified on NCM maps. Pace mapping and activation mapping were performed at both sites. The area of depolarized myocardium during the first 10 ms of spontaneous VA and pacing was measured. The initial site of ablation was randomized to either EA or BO sites, with crossover to the alternate site if ablation was not successful.

RESULTS

In 136 patients, prematurity of local activation and pace maps were similar at EA and BO sites. More myocardium was depolarized 10 ms after pacing than during spontaneous VA (12.9 ± 7.8 cm(2) vs 5.3 ± 3.9 cm(2); P < .01). Clinical success was more likely achieved when initial ablation was directed toward the EA site (P < .05). A wider EA-BO separation was associated with acute procedural failure (P < .01). With a follow-up of 36.2 ± 17.5 months, the success rate after a single procedure without antiarrhythmic agents was 86.8%.

CONCLUSIONS

NCM-guided RVOT VA ablation is highly effective, and clinical success is best achieved by ablating the EA site. Broad regions of early activation are associated with worsened clinical outcomes. Spatial resolution of activation and pace mapping is limited by rapid electrical propagation in the RVOT.

Use of ventricular synchronized triggered atrial pacing to facilitate hemodynamic support during mapping and catheter ablation of ventricular vachycardia

Use of VSTAP to Facilitate Hemodynamic Support. The ablation of hemodynamically unstable ventricular tachycardia (VT) is challenging and frequently requires alternative mapping techniques or the use of percutaneous mechanical support devices. Loss of atrioventricular synchrony contributes to hemodynamic compromise during VT. In order to facilitate successful mapping and ablation of unstable VT, we employed ventricular synchronized triggered atrial pacing (VSTAP) at 50% of the RR interval. In this case, triggered atrial pacing permitted activation mapping and, subsequently, successful ablation of the patient's unstable VT. Thus, VSTAP is a readily available and noninvasive technique that may provide adequate hemodynamic support during catheter ablation of unstable VT.

Image-based electrode array tracking for epicardial electrophysiological mapping in minimally invasive arrhythmia surgery

PURPOSE

Electrophysiological mapping is effective in realizing a precise minimally invasive arrhythmia surgery. Recently, an epicardial electrophysiological mapping system for minimally invasive arrhythmia surgery was reported. The system requires a small electrode array, a tracking system and a global mapping algorithm. The optical tracking system employed in the research requires line of sight and complicated configuration. This paper proposes a new tracking method for locating an electrode array.

METHODS

We developed a small electrode array and optical markers. Center points of respective optical markers and the electrode array are tracked via an endoscopic stream and calculated in image space. The orientation of the electrode array is calculated using the dot product between the vector joining two center points of two upper optical markers and the vector joining two end points of the longest edge of the electrode array.

RESULTS

Mean tracking errors of position and orientation of the electrode array were 0.51 mm and 0.64°, respectively. And the processing time was constant at 46 ms per frame. Our method could successfully track the electrode array on the epicardium during in vivo experiment and a global epicardial electrophysiological map was reconstructed from separately measured epicardial electrograms by the small electrode array.

CONCLUSIONS

An image-based tracking method for locating an electrode array was proposed. Tracking accuracy, processing time and applicability to surgical environment of our method proved to be acceptable. Consequently, our method enables the electrode array tracking system to be simplified with no separate tracking system.

Cell delivery and tracking in post-myocardial infarction cardiac stem cell therapy: an introduction for clinical researchers

Stem cell-based therapy for patients with post-infarct heart failure is a relatively new and revolutionary concept in cardiology. Despite the encouraging results from pre-clinical studies, outcomes from most clinical trials remain moderately positive while the clinical benefits are largely attributed to transplanted cell-associated paracrine effects in stimulating angiogenesis and protecting endogenous cardiomyocytes. This scenario indicates that there may be a considerably protracted iterative process of conceptual and procedural refinement before true clinical benefits can be fully materialized. At present, many pressing questions regarding cell therapy remain unanswered. In addition to the primary interest in determining the ideal type of stem cells with best cardiogenic potential in vitro and in vivo, there are growing concerns on the impact of the host cardiac milieu on the transplanted cells, including their survival, migration, engraftment, and trans-differentiation as well as contribution to left ventricular function. Effective cell delivery and tracking methods are central to the unraveling of these questions. To date, cell-delivery modalities are yet to be optimized and strategies for safe and effective assessment of cells transplanted in the recipients are to be established. In this review, we discuss cell delivery and tracking modalities that are adopted in the current pre-clinical and clinical studies. We further discussed emerging technologies that are poised to impact the success of cell therapy.

Transmural characteristics of atrial fibrillation in canine models of structural and electrical atrial remodeling assessed by simultaneous epicardial and endocardial mapping

BACKGROUND

Epicardial mapping has shown that atrial substrate may play a role in the characteristics of the resulting atrial fibrillation (AF). However, it is not known whether these differences also occur in 3 dimensions.

OBJECTIVE

This study sought to examine the 3-dimensional characteristics of AF by simultaneously analyzing AF on the epicardial and endocardial surfaces.

METHODS

Dogs were divided into 5 groups: congestive heart failure (CHF), rapid atrial pacing (RAP), mitral regurgitation (MR), control, and methylcholine. A noncontact mapping catheter (Ensite 3000 [Endocardial Solutions, Inc., St. Paul, Minnesota]) was placed in the left atrium (LA), and electrode plaques (240 unipoles) were placed over the epicardial surface. Several AF episodes of at least 30 s were recorded, and isopotential videos of activation and isochronal maps were constructed. In addition, each pair of matched electrograms were cross-correlated (XC) and analyzed with a fast Fourier transform (FFT).

RESULTS

The RAP model was the only one with an AF mechanism of multiple wavelets in every dog on both surfaces. In addition, when individual signals were compared, the RAP model had the least amount of similarities between the recording surfaces, whereas the CHF model had the most as it had a higher percentage of signals with XC coefficients >0.8 and a higher percentage of signals with similar dominant frequencies (30 +/- 35% vs. 12 +/- 13% and 66 +/- 30% vs. 26 +/- 10%, P < .05).

CONCLUSION

Although the RAP model had similar AF mechanisms in 3 dimensions, this did not correlate to transmural similarities. Focal mechanisms of AF may have a more uniform wavefront of activation, whereas models with mechanisms of multiple wavelets may have more 3-dimensional properties.

Catheter ablation of ventricular tachycardia guided by noncontact mapping

Catheter ablation of untolerated and unstable ventricular tachycardia may not be performed using a conventional activation mapping tecnique. The noncontact mapping system enables reconstruction of the spreading of activation wave through a virtually generated ventricular chamber, even from a single tachycardia beat, and was introduced as a tool to guide mapping and ablation of untolerated or unsustained ventricular arrhythmias. The reduced accuracy in the setting of enlarged ventricles is recognized as the main limitation of this tecnique. While noncontract mapping appears to be especially suitable in guiding the ablation of unsustained idiopathic ventricular arrhythmias, it can also be successfully used as a guide to perform ablation of untolerated re-entry-related ventricular tachycardias during sinus rhythm.

Mechanisms that initiate ventricular tachycardia in the infarcted human heart

Background

Precise mechanisms that initiate ventricular tachycardia (VT) in the intact infarcted human heart have not been defined.

Objective

The purpose of this study was to investigate the mechanisms that underlie human postinfarct VT initiation.

Methods

Noncontact mapping of the left ventricle was performed in 9 patients (age 67.1 ± 7.8 years, ejection fraction 34.4% ± 5%) with previous myocardial infarction and sustained monomorphic VT.

Results

Circuits in which ≥30% of the diastolic pathway (DP) could be defined were identified in 12 VTs (cycle length 357 ± 60 ms). Eighteen VT episodes were initiated with pacing, and one occurred spontaneously. Ten complete and two partial circuits were mapped (89% ± 25% of the DP). In all complete circuits, pacing led to the development of unidirectional conduction block at the location of the subsequent VT exit site and the formation of functional block creating a border(s) for subsequent DP. Wavefront velocity in the DP region slowed from 1.22 ± 0.2 m/s during sinus rhythm to 0.59 ± 0.14 m/s during VT (P <.005). In 11 initiation episodes, lines of functional block and areas of slow conduction developed progressively over one to six reentrant cycles before a stable DP was established and sustained monomorphic VT ensued. The formation of unidirectional or functional lines of block was not identified during identical pacing protocols that failed to initiate VT (n = 14).

Conclusion

Initiation of sustained monomorphic VT requires the development of unidirectional block and formation of lines of functional block creating borders for a DP in areas of slow conduction. A transitional stage often exists during the initiation process before a stable VT circuit is established.

Catheter ablation of ventricular tachycardia. From indication to three-dimensional mapping technology

The majority of ventricular tachycardias (VTs) occurs in patients with structural heart disease, predominantly coronary heart disease. Implantable cardioverter defibrillators (ICDs) are first-line therapy in patients with VT and structural heart disease. In patients who receive an ICD after a spontaneous sustained VT, recurrent VT episodes or an electrical storm are major problems. In addition, in patients with an ICD implanted for primary prevention of sudden cardiac death, 20% will experience at least one VT episode within 3-5 years after ICD implantation. Catheter ablation has a high acute success rate in eliminating clinical VT. However, several factors make catheter ablation of VT more difficult than ablation of supraventricular tachyarrhythmias. (1) The infarct region is often large. (2) The induced VT can be unstable or hemodynamically only poorly tolerated and therefore "unmappable". (3) Though most commonly located in the subendocardium, the critical VT zone can occasionally be epicardial or intramural in location. (4) In many cases, several reentrant circuits may coexist making ablation of a single form of VT a palliative procedure which does not obviate the risk of sudden death. Thus, catheter ablation of sustained VT in the setting of structural heart disease can only be considered an adjunctive therapy which, in general, will require ICD therapy. Numerous "modern" mapping technologies have been developed, which have increased success rates of catheter ablation of VT in patients with and without structural heart disease. The aim of the present article is to review current three-dimensional mapping systems in comparison to conventional mapping and to describe a reasonable, tailored approach for the individual patient with VT.

Electro-anatomic mapping systems in arrhythmias

Electroanatomic mapping systems have permitted and facilitated difficult interventional ablation procedures for more than a decade. Initially, their use has been in arrhythmias in which the ablation target is difficult to identify, such as ventricular tachycardias in structural heart disease, atypical atrial flutters, or arrhythmias in patients with complex congenital heart defects. In the recent years, electroanatomic mapping systems have also been used to guide catheter-based isolation of the pulmonary veins, an important component of the modern management of atrial fibrillation (AF). Electroanatomic mapping systems integrate three important functionalities, namely (i) non-fluoroscopic localization of electrophysiological catheters in three-dimensional (3D) space; (ii) analysis and 3D display of activation sequences computed from local or calculated electrograms, and 3D display of electrogram voltage ('scar tissue'); and (iii) integration of this 'electroanatomic' information with non-invasive images of the heart (mainly computed tomography or magnetic resonance images). Although better understanding and ablation of complex arrhythmias mostly relies on the 3D integration of catheter localization and electrogram-based information to illustrate re-entrant circuits or areas of focal initiation of arrhythmias, the use of electroanatomic mapping systems in AF is currently based on integration of anatomic images of the left atrium and non-fluoroscopic visualization of the ablation catheter. Their use in the treatment of AF is mainly driven by safety considerations such as shorter fluoroscopy and procedure times, or visualization of cardiac (pulmonary veins) and extra-cardiac (oesophagus) structures that need to be protected during the procedure. In the future, the use of magnetic resonance images, and potentially of high-quality 3D ultrasound images, could provide anatomic information without ionizing radiation and may be helpful to visualize left atrial scar tissue.

Integration of the data from electroanatomical mapping system and CT imaging modality

Heart mapping systems allow approximate reconstruction of the heart chamber geometry which is used as a base for the representation of the spatial distribution of electrophysiological parameters. Main limitation lies in the difficulty of the reconstruction of the geometry of more complicated areas of the heart. Here, we propose a new method of representation of the spatial distribution of the electrophysiological parameters-an integration of the data points collected by a classical mapping system with the geometry reconstructed from a computed tomography (CT) image. CARTO maps of activation and bipolar viability of seven patients undergoing atrial fibrillation ablation were integrated with the geometry of the left atria reconstructed from the CT image. In all cases, integration was successful with the registration error measured as the distance between objects equal to 2.52 +/- 0.25 mm. Bipolar viability and activation maps were reconstructed on the CT geometry. Our method allowed us to create maps of electrophysiological parameters of anatomically complex structures without the need for their detailed mapping.

Electroanatomic mapping in the catheter ablation of premature atrial contractions with a non-pulmonary vein origin

Symptomatic premature atrial contractions (PACs) may be a target for catheter ablation. However, mapping of PACs with an atrial origin may not be easy because of erratic incidence and different sites of origin. Although the technique and efficacy of electroanatomic mapping has been established in stable arrhythmias, electroanatomic mapping of PACs in intermittent arrhythmias has not yet been reported. This article describes a manoeuvre for mapping PACs using an electroanatomic mapping system. Our experience has demonstrated that electroanatomic mapping using an auto-freeze map is feasible during PACs and may be an option for catheter ablation of PACs.

[Electroanatomical mapping systems in catheter ablation of cardiac arrhythmias]

Due to the recent technical development of the past years, most cardiac electrophysiological laboratories are equipped with computer-based electroanatomical mapping systems that precisely describe both the temporal and spatial characteristics of cardiac activation. This development has also been driven by the need for increased accuracy in arrhythmia localization as required for catheter ablation. Computer-based electroanatomical mapping systems are able to reconstruct cardiac anatomy and provide a straightforward representation of chamber activation. These systems capture and display details of intracardiac physiology and mark the site of interventions. Nowadays, several mapping technologies are available in the electrophysiological labs: CARTO XP, EnSite NavX and Array, Real-time Position Management. In this paper we aim to briefly present the principal technological and practical characteristics of these mapping systems regarding eligibility, ability and limitations. The development of computer-based mapping technologies is also discussed in detail, since future systems will be able to display any parametric process including vectors, strains, contraction patterns etc., a wide variety of physiologic parameters beyond activation times and voltage. Using electroanatomical mapping systems, the specific recording of both anatomy and physiology has contributed substantially to the expansion of ablation to atypical atrial flutters, ventricular tachycardia, congenital heart-disease-related arrhythmias and atrial fibrillation. While the technology is already facilitating, the obvious down-side to this technological explosion is cost. Subsequent studies will be needed, however, to show that this translates into improved outcomes and cost savings.