A novel octaray multielectrode catheter for high‐resolution atrial mapping: Electrogram characterization and utility for mapping ablation gaps

Observable Atrial and Ventricular Fibrillation Episode Durations Are Conformant With a Power Law Based on System Size and Spatial Synchronization

BACKGROUND

Atrial fibrillation (AF) and ventricular fibrillation (VF) episodes exhibit varying durations, with some spontaneously ending quickly while others persist. A quantitative framework to explain episode durations remains elusive. We hypothesized that observable self-terminating AF and VF episode lengths, whereby durations are known, would conform with a power law based on the ratio of system size and correlation length ([Formula: see text].

METHODS

Using data from computer simulations (2-dimensional sheet and 3-dimensional left-atrial), human ischemic VF recordings (256-electrode sock, n=12 patients), and human AF recordings (64-electrode basket-catheter, n=9 patients; 16-electrode high definition-grid catheter, n=42 patients), conformance with a power law was assessed using the Akaike information criterion, Bayesian information criterion, coefficient of determination (R2, significance=P<0.05) and maximum likelihood estimation. We analyzed fibrillatory episode durations and [Formula: see text], computed by taking the ratio between system size ([Formula: see text], chamber/simulation size) and correlation length (xi, estimated from pairwise correlation coefficients over electrode/node distance).

RESULTS

In all computer models, the relationship between episode durations and [Formula: see text] was conformant with a power law (Aliev-Panfilov R2: 0.90, P<0.001; Courtemanche R2: 0.91, P<0.001; Luo-Rudy R2: 0.61, P<0.001). Observable clinical AF/VF durations were also conformant with a power law relationship (VF R2: 0.86, P<0.001; AF basket R2: 0.91, P<0.001; AF grid R2: 0.92, P<0.001). [Formula: see text] also differentiated between self-terminating and sustained episodes of AF and VF (P<0.001; all systems), as well as paroxysmal versus persistent AF (P<0.001). In comparison, other electrogram metrics showed no statistically significant differences (dominant frequency, Shannon Entropy, mean voltage, peak-peak voltage; P>0.05).

CONCLUSIONS

Observable fibrillation episode durations are conformant with a power law based on system size and correlation length.

Ripple map delineation of the reentrant circuit in a tricuspid annular atrial tachycardia mimicking focal activity

A 70-year-old man with hypertensive heart disease underwent catheter ablation of persistent atrial fibrillation. After completing the pulmonary vein isolation, atrial burst pacing induced an annular atrial tachycardia (AT). Overdrive pacing exhibited constant fusion, indicating a macroreentrant mechanism of the AT. However, the CARTO3 activation map created using the Octaray catheter (both Biosense Webster, Irvine, CA) exhibited a centrifugal spread with the earliest activation site at the 4 o'clock position of the tricuspid annulus. In contrast, the Ripple map revealed a clear reentrant circuit with its isthmus located at the 4-6 o'clock position of the tricuspid annulus. The local electrograms in these areas recorded systolic and diastolic potentials simultaneously, and the misannotation of the large far-field potentials caused this discrepant result. Handling low-amplitude complex fractionated electrograms remains a challenge in creating a precise activation mapping. The Ripple map, especially when combined with the Octaray catheter, was effective in dynamically visualizing all these electrograms and accurately delineating the reentrant circuit.

Validation of a machine learning algorithm to identify pulmonary vein isolation during ablation procedures for the treatment of atrial fibrillation: results of the PVISION study

AIMS

Pulmonary vein isolation (PVI) is the cornerstone of ablation for atrial fibrillation. Confirmation of PVI can be challenging due to the presence of far-field electrograms (EGMs) and sometimes requires additional pacing manoeuvres or mapping. This prospective multicentre study assessed the agreement between a previously trained automated algorithm designed to determine vein isolation status with expert opinion in a real-world clinical setting.

METHODS AND RESULTS

Consecutive patients scheduled for PVI were recruited at four centres. The ECGenius electrophysiology (EP) recording system (CathVision ApS, Copenhagen, Denmark) was connected in parallel with the existing system in the laboratory. Electrograms from a circular mapping catheter were annotated during sinus rhythm at baseline pre-ablation, time of isolation, and post-ablation. The ground truth for isolation status was based on operator opinion. The algorithm was applied to the collected PV signals off-line and compared with expert opinion. The primary endpoint was a sensitivity and specificity exceeding 80%. Overall, 498 EGMs (248 at baseline and 250 at PVI) with 5473 individual PV beats from 89 patients (32 females, 62 ± 12 years) were analysed. The algorithm performance reached an area under the curve (AUC) of 92% and met the primary study endpoint with a sensitivity and specificity of 86 and 87%, respectively (P = 0.005; P = 0.004). The algorithm had an accuracy rate of 87% in classifying the time of isolation.

CONCLUSION

This study validated an automated algorithm using machine learning to assess the isolation status of pulmonary veins in patients undergoing PVI with different ablation modalities. The algorithm reached an AUC of 92%, with both sensitivity and specificity exceeding the primary study endpoints.

Enhanced identification of ventricular tachycardia isthmus within a scar using Ripple map and Octaray catheter

•Low-amplitude complex EGMs are often observed in the VT isthmus. •Misannotation of local EGMs can lead to incorrect depiction of VT circuits. •Ripple map with Octaray catheter can enhance VT isthmus identification.

Where is the gap after a 90 W/4 s very-high-power short-duration ablation of atrial fibrillation?: Association with the left atrial-pulmonary vein voltage and wall thickness

Background

Although pulmonary vein isolation (PVI) for atrial fibrillation (AF) utilizing radiofrequency (RF) applications with a very high-power and short-duration (vHPSD) has shortened the procedure time, the determinants of pulmonary vein (PV) gaps in the first-pass PVI and acute PV reconnections are unclear.

Methods

An extensive encircling PVI was performed with the QDOT MICRO catheter with a vHPSD (90 W-4 s) in 30 patients with AF (19 men, 64 ± 10 years). The association of the PV gap sites (first-pass PVI failure, acute PV reconnections [spontaneous reconnections or dormant conduction provoked by adenosine triphosphate] or both) with the left atrial (LA) wall thickness and LA bipolar voltage on the PVI line and ablation-related parameters were assessed.

Results

PV gaps were observed in 29 (6%) of 480 segments (16 segments per patient) in 17 patients (56%). The PV gaps were associated with the LA wall thickness, bipolar voltage, and the number of RF points (LA wall thickness, 2.5 ± 0.5 vs. 1.9 ± 0.4 mm, p < .001; bipolar voltage, 2.59 ± 1.62 vs. 1.34 ± 1.14 mV, p < .001; RF points, 6 ± 2 vs. 4 ± 2, p = .008) but were not with the other ablation-related parameters. Receiver operating characteristic curves yielded that an LA wall thickness ≥2.3 mm and bipolar voltage ≥2.40 mV were determinants of PV gaps with an area under the curve of 0.82 and 0.73, respectively.

Conclusions

The LA voltage and wall thickness on the PV-encircling ablation line were highly associated with PV gaps using the 90 W/4 s-vHPSD ablation.

Electrophysiological evidence of right atrial epicardial connections in a case with recurrent common atrial flutter

The majority of the cavotricuspid isthmus (CTI) region consists of discretely arranged muscle bundles separated by connective tissue. Heterogeneity in the anatomic arrangement of the muscle bundles results in differences in the endocardial and epicardial activation patterns. We present a case of recurrent atrial flutter (AFL) despite the presence of a complete endocardial CTI block. We found epicardial-endocardial breakthrough (EEB) sites on the right atrial high septum. In addition, the epicardial excitation confirmed by endocardial activation mapping was detected as far-field potentials. Radiofrequency ablation was performed at the EEB site. No AFL has recurred for 12 months after the present procedure.

The Influence of Different Multipolar Mapping Catheter Types on Procedural Outcomes in Patients Undergoing Pulmonary Vein Isolation for Atrial Fibrillation

(1) Background: During pulmonary vein isolation (PVI) for atrial fibrillation (AF), multipolar mapping catheters (MMC) are often used. We aimed to compare the procedural outcomes of two MMCs, specifically a circular-shaped and a five-spline-shaped MMC. (2) Methods: We enrolled 70 consecutive patients in our prospective, observational trial undergoing PVI procedures for paroxysmal AF. The initial 35 patients underwent PVI procedures with circular-shaped MMC guidance (Lasso Group), and the procedures for the latter 35 cases were performed using five-spline-shaped MMC (PentaRay Group). (3) Results: No significant differences were identified between the two groups in total procedure time (80.2 ± 17.7 min vs. 75.7 ± 14.8 min, p = 0.13), time from femoral vein puncture to the initiation of the mapping (31.2 ± 7 min vs. 28.9 ± 6.8, p = 0.80), mapping time (8 (6; 13) min vs. 9 (6.5; 10.5) min, p = 0.73), duration between the first and last ablation (32 (30; 36) min vs. 33 (26; 40) min, p = 0.52), validation time (3 (2; 4) min vs. 3 (1; 5) min, p = 0.46), first pass success rates (89% vs. 91%, p = 0.71), left atrial dwelling time (46 (37; 53) min vs. 45 (36.5; 53) min, p = 0.56), fluoroscopy data (time: 150 ± 71 s vs. 143 ± 56 s, p = 0.14; dose: 6.7 ± 4 mGy vs. 7.4 ± 4.4 mGy, p = 0.90), total ablation time (1187 (1063; 1534) s vs. 1150.5 (1053; 1393.5) s, p = 0.49), the number of ablations (78 (73; 93) vs. 83 (71.3; 92.8), p = 0.60), and total ablation energy (52,300 (47,265; 66,804) J vs. 49,666 (46,395; 56,502) J, p = 0.35). (4) Conclusions: This study finds comparable procedural outcomes bet-ween circular-shaped and five-spline-shaped MMCs for PVI in paroxysmal AF, supporting their interchangeability in clinical practice for anatomical mapping.

Overcoming Uncertainties in Electrogram-Based Atrial Fibrillation Mapping: A Review

In clinical rhythmology, intracardiac bipolar electrograms (EGMs) play a critical role in investigating the triggers and substrates inducing and perpetuating atrial fibrillation (AF). However, the interpretation of bipolar EGMs is ambiguous due to several aspects of electrodes, mapping algorithms and wave propagation dynamics, so it requires several variables to describe the effects of these uncertainties on EGM analysis. In this narrative review, we critically evaluate the potential impact of such uncertainties on the design of cardiac mapping tools on AF-related substrate characterization. Literature suggest uncertainties are due to several variables, including the wave propagation vector, the wave's incidence angle, inter-electrode spacing, electrode size and shape, and tissue contact. The preprocessing of the EGM signals and mapping density will impact the electro-anatomical representation and the features extracted from the local electrical activities. The superposition of multiple waves further complicates EGM interpretation. The inclusion of these uncertainties is a nontrivial problem but their consideration will yield a better interpretation of the intra-atrial dynamics in local activation patterns. From a translational perspective, this review provides a concise but complete overview of the critical variables for developing more precise cardiac mapping tools.

Open-window mapping for ablation of Wolff-Parkinson-White syndrome related hemodynamically unstable tachycardia

During catheter ablation (CA) of tachycardia, conventional point-by-point mapping may be hindered due to hemodynamic instability. We performed open-window mapping (CARTO, Biosense Webster, USA) in a patient who developed hemodynamic instability during orthodromic atrioventricular reciprocating tachycardia (AVRT) and unwarranted induction of AVRT during attempts to map accessory pathway (AP) with ventricular pacing. With over 11,000 points acquired rapidly, the system accurately identified AP at the mitral valve (MV) annulus where the application of single radiofrequency (RF) lesion promptly eliminated AP's conduction. Our case illustrates the utility of open-window mapping for the ablation of AVRT.

High-density mapping for ablation of atypical atrial flutters - procedural characteristics related to outcome

BACKGROUND

High-density (HD) mapping is increasingly used to characterize arrhythmic substrate for ablation of atypical atrial flutters (AAFl). However, results on clinical outcomes and factors that are associated with arrhythmia recurrence are scarce.

METHODS

Single-center, prospective, observational cohort study that enrolled patients with catheter ablation for AAFl using a HD mapping system and a grid-shaped mapping catheter. Procedural characteristics, rates of atrial flutter recurrence, and factors that were associated with atrial flutter recurrence were evaluated.

RESULTS

Sixty-one patients with a total of 94 AAFl were included in the cohort. HD mapping was used to successfully identify the flutter circuit of 80/94 AAFl. The circuit was not identified for 14/94 AAFl in 11 patients. Critical isthmuses were identified and ablated in 29 patients (48%). Acute procedural success was achieved in 52 patients (85%), and 37 patients (61%) remained free from atrial flutter recurrence during a follow up of 1.3 [1.0-2.1] years. Atrial flutter recurrence was univariably associated with presence of a non-identified flutter circuit (HR:2.6 95% CI [1.1-6.3], p = .04) and critical isthmus-targeted ablation (HR:0.4 [0.15-0.90], p = .03). In multivariable regression analyses, critical isthmus ablation remained significant (HR:0.4 [0.16-0.97], p = .04), whereas presence of a non-identified flutter did not (HR:2.4 [0.96-5.8], p = .06).

CONCLUSION

HD mapping was successfully used to identify the majority of AAFl circuits. Ablation resulted in freedom from atrial flutter recurrence in 61% of the cohort. Successful identification of all flutter circuits and critical isthmuses appears to be beneficial for long-term outcomes.

High density mapping of atrial tachycardia in patients post cardiac surgery

Mapping and ablation of atrial tachycardia (AT) in patients who have had prior cardiac surgery can be a challenge for clinical electrophysiologists. High density mapping (HDM) technology has been widely used in these patients because it provides a better characterization of the substrate and the mechanisms with an unprecedented high resolution. In this review, we summarize how the latest HDM technologies can reveal the mechanism of AT in different types of patients post-cardiac surgery and guide a specifically tailored ablation strategy.

Utility of open-window mapping for catheter ablation of an accessory pathway in patients with Wolff-Parkinson-White syndrome

BACKGROUND

Open-window mapping (OWM) is a novel automated mapping method for catheter ablation of an accessory pathway (AP), in which the local signal is annotated with window-of-interest parameters to analyze both atrial and ventricular signals. This study aimed to determine the utility of OWM in visualizing the location and width of APs in patients with Wolff-Parkinson-White syndrome.

METHODS

This two-center study enrolled 30 patients (20 males; mean age: 56 years, interquartile range [IQR]: 22-69 years) who underwent high-density OWM with the extended early-meets-late (EEML) algorithm using a 20-electrode, 5-spline catheter (PENTARAY, Biosense Webster). The lower threshold of the EEML was set to adjust the EEML gap to match the propagation mapping, and broad APs were defined as an EEML gap > 1 cm.

RESULTS

The median mapping points, mapping time, and lower threshold of the EEML were 2482 (IQR: 1755-4000) points, 23 (IQR: 15-30) min, and 23 (IQR: 18-25), respectively. All 30 APs (24 in the mitral annulus and 6 in the tricuspid annulus) were successfully eliminated. Of these APs, 21 (70%) were eliminated by the first radio frequency (RF) application. OWM revealed broad APs in 11 patients (37%), in four of whom (36%) the first RF application achieved a loss of AP conduction (vs. 90% of patients without broad APs; p = .004).

CONCLUSION

OWM facilitates the visualization of the location and width of APs, which may be particularly useful for predicting whether multiple RF applications are required for broad APs.

Atrial substrate characterization based on bipolar voltage electrograms acquired with multipolar, focal and mini-electrode catheters

BACKGROUND

Bipolar voltage (BV) electrograms for left atrial (LA) substrate characterization depend on catheter design and electrode configuration.

AIMS

The aim of the study was to investigate the relationship between the BV amplitude (BVA) using four catheters with different electrode design and to identify their specific LA cutoffs for scar and healthy tissue.

METHODS AND RESULTS

Consecutive high-resolution electroanatomic mapping was performed using a multipolar-minielectrode Orion catheter (Orion-map), a duo-decapolar circular mapping catheter (Lasso-map), and an irrigated focal ablation catheter with minielectrodes (Mifi-map). Virtual remapping using the Mifi-map was performed with a 4.5 mm tip-size electrode configuration (Nav-map). BVAs were compared in voxels of 3 × 3 × 3 mm3. The equivalent BVA cutoff for every catheter was calculated for established reference cutoff values of 0.1, 0.2, 0.5, 1.0, and 1.5 mV. We analyzed 25 patients (72% men, age 68 ± 15 years). For scar tissue, a 0.5 mV cutoff using the Nav corresponds to a lower cutoff of 0.35 mV for the Orion and of 0.48 mV for the Lasso. Accordingly, a 0.2 mV cutoff corresponds to a cutoff of 0.09 mV for the Orion and of 0.14 mV for the Lasso. For healthy tissue cutoff at 1.5 mV, a larger BVA cutoff for the small electrodes of the Orion and the Lasso was determined of 1.68 and 2.21 mV, respectively.

CONCLUSION

When measuring LA BVA, significant differences were seen between focal, multielectrode, and minielectrode catheters. Adapted cutoffs for scar and healthy tissue are required for different catheters.

[New mapping tools for catheter ablation of atrial fibrillation]

The pulmonary veins have been recognized as the primary source of atrial triggers, and their isolation has become the cornerstone for ablation of atrial fibrillation. However, long-term success rates after pulmonary vein isolation (PVI) are limited. Several promising new mapping techniques are described in this article, aiming to better understand the mechanisms underlying the induction and maintenance of atrial fibrillation and to develop more effective ablation strategies.

Initial Clinical Experience With a Novel 8-Spline High-Resolution Mapping Catheter

BACKGROUND

The Octaray (Biosense Webster) is a novel, multispline mapping catheter with 48 closely spaced microelectrodes enabling high-resolution electroanatomical mapping.

OBJECTIVES

This study sought to report the initial clinical mapping experience with this novel catheter in a variety of cardiac arrhythmias and to compare the mapping performance with the 5-spline Pentaray.

METHODS

Fifty consecutive procedures among 46 patients were retrospectively analyzed regarding safety, efficacy, and acute procedural success defined as termination or noninducibility of clinical tachycardia, conduction block across an ablation line, or pulmonary vein isolation. In addition, another 10 patients with sustained atrial tachycardia mapped with the 5-spline catheter (2-5-2 spacing) or the novel 8-spline catheter (2-2-2-2-2 spacing) were analyzed.

RESULTS

Left atrial and ventricular mapping by either transseptal (n = 41) or retroaortic (n = 2) access was feasible without any complications related to the multispline design of the novel catheter. The acute procedural success rate was 94%. In sustained atrial tachycardia compared with the 5-spline catheter, the novel 8-spline catheter recorded more electrograms per map (3,628 ± 714 vs 11,350 ± 1,203; P < 0.001) in a shorter mapping time (13 ± 2 vs 9 ± 1 minutes; P = 0.08) resulting in a higher point density (18 ± 4 vs 59 ± 10 electrograms/cm²; P < 0.01) and point acquisition rate (308 ± 69 vs 1,332 ± 208 electrograms/min.; P < 0.01).

CONCLUSIONS

In this initial experience, mapping with the novel catheter was safe and efficient with a high electroanatomical resolution. In sustained atrial tachycardia the novel 8-spline catheter demonstrated a marked increase in point density and mapping speed compared with those of the 5-spline catheter. These initial results should be validated in a larger multicenter cohort with longer follow-up.

Procedural Feasibility and Long-Term Efficacy of Catheter Ablation of Atypical Atrial Flutters in a Wide Spectrum of Heart Diseases: An Updated Clinical Overview

Atypical atrial flutters (AAFL) are difficult-to-manage atrial arrhythmias, yet potentially amenable to effective radiofrequency catheter ablation (CA). However, data on CA feasibility are only sparingly reported in the literature in different clinical settings, such as AAFL related to surgical correction of congenital heart disease. The aim of this review was to provide an overview of the clinical settings in which AAFL may occur to help the cardiac electrophysiologist in the prediction of the tachycardia circuit location before CA. Moreover, the role and proper implementation of cutting-edge technologies in this setting were investigated as well as which procedural and clinical factors are associated with long-term failure to maintain sinus rhythm (SR) to find out which patients may, or may not, benefit from this procedure. Not only different surgical and non-surgical scenarios are associated with peculiar anatomical location of AAFL, but we also found that CA of AAFL is generally feasible. The success rate may be as low as 50% in surgically corrected congenital heart disease (CHD) patients but up to about 90% on average after pulmonary vein isolation (PVI) or in patients without structural heart disease. Over the years, the progressive implementation of three-dimensional mapping systems and high-density mapping tools has also proved helpful for ablation of these macro-reentrant circuits. However, the long-term maintenance of SR may still be suboptimal due to the progressive electroanatomic atrial remodeling occurring after cardiac surgery or other interventional procedures, thus limiting the likelihood of successful ablation in specific clinical settings.

Atrial fibrillation driver identification through regional mutual information networks: a modeling perspective

Purpose

Effective identification of electrical drivers within remodeled tissue is a key for improving ablation treatment for atrial fibrillation. We have developed a mutual information, graph-based approach to identify and propose fault tolerance metric of local efficiency as a distinguishing feature of rotational activation and remodeled atrial tissue.

Methods

Voltage data were extracted from atrial tissue simulations (2D Karma, 3D physiological, and the Multiscale Cardiac Simulation Framework (MSCSF)) using multi-spline open and parallel regional mapping catheter geometries. Graphs were generated based on varied mutual information thresholds between electrode pairs and the local efficiency for each graph was calculated.

Results

High-resolution mapping catheter geometries can distinguish between rotational and irregular activation patterns using the derivative of local efficiency as a function of increasing mutual information threshold. The derivative is decreased for rotational activation patterns comparing to irregular activations in both a simplified 2D model (0.0017 ± 1 × 10⁻⁴ vs. 0.0032 ± 1 × 10⁻⁴, p < 0.01) and a more realistic 3D model (0.00092 ± 5 × 10⁻⁵ vs. 0.0014 ± 4 × 10⁻⁵, p < 0.01). Average local efficiency derivative can also distinguish between degrees of remodeling. Simulations using the MSCSF model, with 10 vs. 90% remodeling, display distinct derivatives in the grid design parallel spline catheter configuration (0.0015 ± 5 × 10⁻⁵ vs. 0.0019 ± 6 × 10⁻⁵, p < 0.01) and the flower shaped open spline configuration (0.0011 ± 5 × 10⁻⁵ vs. 0.0016 ± 4 × 10⁻⁵, p < 0.01).

Conclusion

A decreased derivative of local efficiency characterizes rotational activation and varies with atrial remodeling. This suggests a distinct communication pattern in cardiac rotational activation detectable via high-resolution regional mapping and could enable identification of electrical drivers for targeted ablation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10840-021-01101-z.

Critical appraisal of technologies to assess electrical activity during atrial fibrillation: a position paper from the European Heart Rhythm Association and European Society of Cardiology Working Group on eCardiology in collaboration with the Heart Rhythm Society, Asia Pacific Heart Rhythm Society, Latin American Heart Rhythm Society and Computing in Cardiology

We aim to provide a critical appraisal of basic concepts underlying signal recording and processing technologies applied for (i) atrial fibrillation (AF) mapping to unravel AF mechanisms and/or identifying target sites for AF therapy and (ii) AF detection, to optimize usage of technologies, stimulate research aimed at closing knowledge gaps, and developing ideal AF recording and processing technologies. Recording and processing techniques for assessment of electrical activity during AF essential for diagnosis and guiding ablative therapy including body surface electrocardiograms (ECG) and endo- or epicardial electrograms (EGM) are evaluated. Discussion of (i) differences in uni-, bi-, and multi-polar (omnipolar/Laplacian) recording modes, (ii) impact of recording technologies on EGM morphology, (iii) global or local mapping using various types of EGM involving signal processing techniques including isochronal-, voltage- fractionation-, dipole density-, and rotor mapping, enabling derivation of parameters like atrial rate, entropy, conduction velocity/direction, (iv) value of epicardial and optical mapping, (v) AF detection by cardiac implantable electronic devices containing various detection algorithms applicable to stored EGMs, (vi) contribution of machine learning (ML) to further improvement of signals processing technologies. Recording and processing of EGM (or ECG) are the cornerstones of (body surface) mapping of AF. Currently available AF recording and processing technologies are mainly restricted to specific applications or have technological limitations. Improvements in AF mapping by obtaining highest fidelity source signals (e.g. catheter-electrode combinations) for signal processing (e.g. filtering, digitization, and noise elimination) is of utmost importance. Novel acquisition instruments (multi-polar catheters combined with improved physical modelling and ML techniques) will enable enhanced and automated interpretation of EGM recordings in the near future.

Propagation Vectors Facilitate Differentiation Between Conduction Block, Slow Conduction, and Wavefront Collision

[Figure: see text].

A novel multielectrode catheter for high-density ventricular mapping: electrogram characterization and utility for scar mapping

AIMS

Multielectrode mapping catheters can be advantageous for identifying surviving myocardial bundles in scar. This study aimed to evaluate the utility of a new multielectrode catheter with increased number of small and closely spaced electrodes for mapping ventricles with healed infarction.

METHODS AND RESULTS

In 12 swine (four healthy and eight with infarction), the left ventricle was mapped with investigational (OctarayTM) and standard (PentarayTM) multielectrode mapping catheters. The investigational catheter has more electrodes (48 vs. 20), each with a smaller surface area (0.9 vs. 2.0 mm2) and spacing is fixed at 2 mm (vs. 2-6-2 mm). Electrogram (EGM) characteristics, mapping efficiency and scar description were compared between the catheters and late gadolinium enhancement (LGE). Electrogram acquisition rate was faster with the investigational catheter (814 ± 126 vs. 148 ± 58 EGM/min, P = 0.02) resulting in higher density maps (38 ± 10.3 vs. 10.1 ± 10.4 EGM/cm2, P = 0.02). Bipolar voltage amplitude was similar between the catheters in normal and infarcted myocardium (P = 0.265 and P = 0.44) and the infarct surface area was similar between the catheters (P = 0.12) and corresponded to subendocardial LGE. The investigational catheter identified a higher proportion of near-field local abnormal ventricular activities within the low-voltage area (53 ± 16% vs. 34 ± 16%, P = 0.03) that were considered far-field EGMs by the standard catheter. The investigational catheter was also advantageous for mapping haemodymically non-tolerated ventricular tachycardias due to its higher acquisition rate (P < 0.001).

CONCLUSION

A novel multielectrode mapping catheter with higher number of small, and closely spaced electrodes increases the mapping speed, EGM density and the ability to recognize low amplitude near-field EGMs in ventricles with healed infarction.

Approach to recurrence of atrial fibrillation after catheter ablation

Atrial fibrillation (AF) is the most commonly observed sustained rhythm disorder during adult ages. Since it has been shown that the ectopic beat initiating AF is usually caused by pulmonary veins, AF ablation has become the mainstay of therapy worldwide. Cryoballoon and radiofrequency ablation are the most commonly used methods in today's technologies. However, despite technological advances, the success of a single procedure in AF ablation is still limited and multiple procedures may be required for the majority of patients. In cases in which a redo ablation is required, pulmonary vein isolation is still the main target, but non-pulmonary vein targets should also be considered in AF episodes that continue despite multiple ablations. Many issues are still unclear as to which energy to choose in the first procedure, and what ablation strategy will be utilized when a redo ablation is required. The studies on this subject are very limited but, it still seems feasible and a rational approach to utilize a customized treatment strategy in each specific patient subgroup.

Updates in Ventricular Tachycardia Ablation

Sudden cardiac death (SCD) due to recurrent ventricular tachycardia is an important clinical sequela in patients with structural heart disease. As a result, ventricular tachycardia (VT) has emerged as a major clinical and public health problem. The mechanism of VT is predominantly mediated by re-entry in the presence of arrhythmogenic substrate (scar), though focal mechanisms are also important. Catheter ablation for VT, when compared to standard medical therapy, has been shown to improve VT-free survival and burden of device therapies. Approaches to VT ablation are dependent on the underlying disease process, broadly classified into idiopathic (no structural heart disease) or structural heart disease (ischemic or non-ischemic heart disease). This update aims to review recent advances made for the treatment of VT ablation, with respect to current clinical trials, peri-procedure risk assessments, pre-procedural cardiac imaging, electro-anatomic mapping and advances in catheter and non-catheter based ablation techniques.

Spatial-Temporal Signals and Clinical Indices in Electrocardiographic Imaging (II): Electrogram Clustering and T-wave Alternans

During the last years, attention and controversy have been present for the first commercially available equipment being used in Electrocardiographic Imaging (ECGI), a new cardiac diagnostic tool which opens up a new field of diagnostic possibilities. Previous knowledge and criteria of cardiologists using intracardiac Electrograms (EGM) should be revisited from the newly available spatial-temporal potentials, and digital signal processing should be readapted to this new data structure. Aiming to contribute to the usefulness of ECGI recordings in the current knowledge and methods of cardiac electrophysiology, we previously presented two results: First, spatial consistency can be observed even for very basic cardiac signal processing stages (such as baseline wander and low-pass filtering); second, useful bipolar EGMs can be obtained by a digital processing operator searching for the maximum amplitude and including a time delay. In addition, this work aims to demonstrate the functionality of ECGI for cardiac electrophysiology from a twofold view, namely, through the analysis of the EGM waveforms, and by studying the ventricular repolarization properties. The former is scrutinized in terms of the clustering properties of the unipolar an bipolar EGM waveforms, in control and myocardial infarction subjects, and the latter is analyzed using the properties of T-wave alternans (TWA) in control and in Long-QT syndrome (LQTS) example subjects. Clustered regions of the EGMs were spatially consistent and congruent with the presence of infarcted tissue in unipolar EGMs, and bipolar EGMs with adequate signal processing operators hold this consistency and yielded a larger, yet moderate, number of spatial-temporal regions. TWA was not present in control compared with an LQTS subject in terms of the estimated alternans amplitude from the unipolar EGMs, however, higher spatial-temporal variation was present in LQTS torso and epicardium measurements, which was consistent through three different methods of alternans estimation. We conclude that spatial-temporal analysis of EGMs in ECGI will pave the way towards enhanced usefulness in the clinical practice, so that atomic signal processing approach should be conveniently revisited to be able to deal with the great amount of information that ECGI conveys for the clinician.

How, When, and Why: High-Density Mapping of Atrial Fibrillation

High-density (HD) mapping presents opportunities to enhance delineation of atrial fibrillation (AF) substrate, improve efficiency of the mapping procedure without sacrificing safety, and afford new mechanistic insights regarding AF. Innovations in hardware, software algorithms, and development of novel multielectrode catheters have allowed HD mapping to be feasible and reliable. Patients to particularly benefit from this technology are those with paroxysmal AF in setting of preexisting atrial scar, persistent AF, and AF in the setting of complex congenital heart disease. The future will bring refinements in automated HD mapping including evolution of noncontact methodologies and artificial intelligence to supplant current techniques.

A Catheter-Deployable Soft Robotic Inflatable Basket for Enhanced Conformability to the Left Atrium of the Heart

This paper presents the design, fabrication, and test results for a novel basket catheter that utilizes soft robotic technology, which can conform to complex patient anatomy. Two designs of basket-shaped balloons in three sizes are fabricated based on a CO₂ laser cutting method from thin (<50 µm) thermoplastic polyurethane. The balloons are deployed in four soft-material 3D printed left atria, whose geometries are based on volume rendered segmentation of cardiac computed tomography (CT) scans. The coverage and conformability to the realistic patient anatomies is tracked with the small patches of pH paper that indicate, via a color change, contact with a basic solution that lined the 3D printed atriums. The conformability of these inflatable basket catheters is demonstrated as high as (85%) for the optimized design. To visualize the balloon's performance, microCT images of balloons deployed in 3D printed models are shown. These images show the ability of the balloons to adapt to complex patient anatomy and do not exhibit any spline bunching or other deleterious mechanical behavior. This platform has the potential to be coupled with electrical sensors for simultaneous multisensor mapping of atrial fibrillation and other cardiac arrhythmias.