Pulmonary vein isolation using the Rhythmia mapping system: Verification of intracardiac signals using the Orion mini-basket catheter

A Review of Recent Advancements in Sensor-Integrated Medical Tools

A medical tool is a general instrument intended for use in the prevention, diagnosis, and treatment of diseases in humans or other animals. Nowadays, sensors are widely employed in medical tools to analyze or quantify disease-related parameters for the diagnosis and monitoring of patients' diseases. Recent explosive advancements in sensor technologies have extended the integration and application of sensors in medical tools by providing more versatile in vivo sensing capabilities. These unique sensing capabilities, especially for medical tools for surgery or medical treatment, are getting more attention owing to the rapid growth of minimally invasive surgery. In this review, recent advancements in sensor-integrated medical tools are presented, and their necessity, use, and examples are comprehensively introduced. Specifically, medical tools often utilized for medical surgery or treatment, for example, medical needles, catheters, robotic surgery, sutures, endoscopes, and tubes, are covered, and in-depth discussions about the working mechanism used for each sensor-integrated medical tool are provided.

One-year outcomes of wide antral cryoballoon ablation guided by high-density mapping vs. conventional cryoballoon ablation for atrial fibrillation: a propensity score-matched study

Background

Pulmonary vein isolation with wide antral ablation leads to better clinical outcomes for the treatment of atrial fibrillation, but the isolation lesion is invisible in conventional cryoballoon ablation. In this study, we aim to investigate the efficacy of the wide pulmonary vein isolation technique that includes the intervenous carina region, guided by high-density mapping, compared with pulmonary vein isolation alone without the mapping system.

Methods

We conducted a propensity score-matched comparison of 74 patients who underwent a wide cryoballoon ablation guided by high-density mapping (mapping group) and 74 controls who underwent conventional cryoballoon ablation in the same period (no-mapping group). The primary outcome was a clinical recurrence of documented atrial arrhythmias for >30 s during the 1-year follow-up.

Results

Of 74 patients in the mapping group, residual local potential in the pulmonary vein antrum was found in 30 (40.5%) patients, and additional cryothermal applications were performed to achieve a wide pulmonary vein isolation. Compared with the no-mapping group, the use of the mapping system in the mapping group was associated with a longer fluoroscopic time (26.97 ± 8.07 min vs. 23.76 ± 8.36 min, P = 0.023) and greater fluoroscopic exposure [339 (IQR181-586) mGy vs. 224 (IQR133-409) mGy, P = 0.012]. However, no significant differences between the two groups were found in terms of procedural duration and left atrial dwell time (104.10 ± 18.76 min vs. 102.45 ± 21.01 min, P = 0.619; 83.52 ± 17.01 min vs. 79.59 ± 17.96 min, P = 0.177). The rate of 12-month freedom from clinical atrial arrhythmia recurrence was 85.1% in the mapping group and 70.3% in the no-mapping group (log-rank P = 0.029).

Conclusion

Voltage and pulmonary vein potential mapping after cryoballoon pulmonary vein isolation can identify residual potential in the pulmonary vein antrum, and additional cryoablation guided by mapping leads to improved freedom from atrial arrhythmias compared with conventional pulmonary vein isolation without the mapping system.

Clinical Trial Registration Number

ChiCTR2200064383.

High density mapping of complex atrial tachycardia in patients after cardiac surgery

To provide an overview of the current application of high-density mapping (HDM) in the mechanism of complex atrial tachycardias (ATs). Complex ATs are frequently scar-related, after history of previous cardiac surgery and large scars. These scar-related ATs are difficult to manage medically and frequently recur after electrical cardioversion. HDM technologies have enabled rigorous elucidation of AT mechanisms in patients post cardiac surgery. This article showed the application of HDM technology in complex ATs from the mechanisms of complex ATs, the development of HDM technology, and the identification of scars or critical isthmus from HDM. HDM-guided approach is highly effective for identifying the ATs mechanism and critical isthmus.

Determination of online thin film buckling configuration by parametric optimization for flexible sensor application

A mini basket type mapping catheter consists of thin film flexible sensors and is applied in the medical field to measure the electrocardiography (ECG) signals in order to localize and quantize the physiological condition/status of heart. The flexible nature of the thin film changes the configuration with respect to the contact boundary conditions when it contacts a target surface. Therefore, to accurately localize the flexible sensor, the thin film flexible sensor's configuration must be determined accurately in an on-line fashion. As a study of localizing the thin film flexible sensor, this study proposes an on-line thin film buckling configuration determination method using parametric optimization and interpolation technique. With the specific modulus of elasticity and dimensions of the thin film flexible sensor of the mapping catheter prototype, the buckling configuration with two point boundary condition under axial load can be calculated in desktop environment. The proposed calculation method is validated by mapping catheter sensor prototype test. The calculation/test results showed that the maximum overall length L, x[Formula: see text], and y[Formula: see text] value error between the calculation and experiment are approximately 0.16 mm, - 0.12 mm. - 0.10 mm in 50 ms calculation time. The calculation result of the proposed method is also compared with that of the numerical simulation by FEM, which has approximately 0.44 mm y[Formula: see text] value error compared with that of the experiment.

Atrial conduction velocity mapping: clinical tools, algorithms and approaches for understanding the arrhythmogenic substrate

Characterizing patient-specific atrial conduction properties is important for understanding arrhythmia drivers, for predicting potential arrhythmia pathways, and for personalising treatment approaches. One metric that characterizes the health of the myocardial substrate is atrial conduction velocity, which describes the speed and direction of propagation of the electrical wavefront through the myocardium. Atrial conduction velocity mapping algorithms are under continuous development in research laboratories and in industry. In this review article, we give a broad overview of different categories of currently published methods for calculating CV, and give insight into their different advantages and disadvantages overall. We classify techniques into local, global, and inverse methods, and discuss these techniques with respect to their faithfulness to the biophysics, incorporation of uncertainty quantification, and their ability to take account of the atrial manifold.

Patterns and Characteristics of SKYLINE-Lumipoint Feature in the Catheter Ablation of Atypical Atrial Flutter: Insight from a Novel Lumipoint Module of Rhythmia Mapping System

Background: Atypical atrial flutter (aAFL) is not uncommon, especially after a prior cardiac surgery or extensive ablation in atrial fibrillation (AF). Aims: To revisit aAFL, we used a novel Lumipoint algorithm in the Rhythmia mapping system to evaluate tachycardia circuit by the patterns of global activation histogram (GAH, SKYLINE) in assisting aAFL ablation. Methods: Fifteen patients presenting with 20 different incessant aAFL, including two naïve, six with a prior AF ablation, and seven with prior cardiac surgery were studied. Results: Reentry aAFL in SKYLINE typically was a multi-deflected peak with 1.5 GAH-valleys. Valleys were sharp and narrow-based. Most reentry aAFL (18/20, 90%) lacked a plateau and displayed a steep GAH-valley with 2 GAH-valleys per tachycardia. Each GAH-valley highlighted 1.9 areas in the map. Successful sites of ablation all matched one of the highlighted areas based on GAH-valleys < 0.4. These sites corresponded with the areas highlighted by GAH-score < 0.4 in reentry aAFL, and by GAH-score < 0.2 in localized-reentry aAFL. Conclusions: The present study showed benefits of the LumipointTM module applied to the RhythmiaTM mapping system. The results were the efficient detection of the slow conduction, better identification of ablation sites, and fast termination of the aAFL with favorable outcomes.

The impact of ultra-high-density mapping on long-term outcome after catheter ablation of ventricular tachycardia

Ultra-high-density (UHD) mapping can improve scar area detection and fast activation mapping in patients undergoing catheter ablation of ventricular tachycardia (VT). The aim of the present study was to compare the outcome after VT ablation guided by UHD and conventional point-by-point 3D-mapping. The acute and long-term ablation outcome of 61 consecutive patients with UHD mapping (64-electrode mini-basket catheter) was compared to 61 consecutive patients with conventional point-by-point 3D-mapping using a 3.5 mm tip catheter. Patients, whose ablation was guided by UHD mapping had an improved 24-months outcome in comparison to patients with conventional mapping (cumulative incidence estimate of the combination of recurrence or disease-related death of 52.4% (95% confidence interval (CI) [36.9-65.7]; recurrence: n = 25; disease-related death: n = 4) versus 69.6% (95% CI [55.9-79.8]); recurrence: n = 31; disease-related death n = 11). In a cause-specific Cox proportional hazards model, UHD mapping (hazard ratio (HR) 0.623; 95% CI [0.390-0.995]; P = 0.048) and left ventricular ejection fraction > 30% (HR 0.485; 95% CI [0.290-0.813]; P = 0.006) were independently associated with lower rates of recurrence or disease-related death. Other procedural parameters were similar in both groups. In conclusion, UHD mapping during VT ablation was associated with fewer VT recurrences or disease-related deaths during long-term follow-up in comparison to conventional point-by-point mapping. Complication rates and other procedural parameters were similar in both groups.

Improved procedural workflow for catheter ablation of paroxysmal AF with high-density mapping system and advanced technology: Rationale and study design of a multicenter international study

BACKGROUND

The antral region of pulmonary veins (PV)s seems to play a key role in a strategy aimed at preventing atrial fibrillation (AF) recurrence. Particularly, low-voltage activity in tissue such as the PV antra and residual potential within the antral scar likely represent vulnerabilities in antral lesion sets, and ablation of these targets seems to improve freedom from AF. The aim of this study is to validate a structured application of an approach that includes the complete abolition of any antral potential achieving electrical quiescence in antral regions.

METHODS

The improveD procEdural workfLow for cathETEr ablation of paroxysmal AF with high density mapping system and advanced technology (DELETE AF) study is a prospective, single-arm, international post-market cohort study designed to demonstrate a low rate of clinical atrial arrhythmias recurrence with an improved procedural workflow for catheter ablation of paroxysmal AF, using the most advanced point-by-point RF ablation technology in a multicenter setting. About 300 consecutive patients with standard indications for AF ablation will be enrolled in this study. Post-ablation, all patients will be monitored with ambulatory event monitoring, starting within 30 days post-ablation to proactively detect and manage any recurrences within the 90-day blanking period, as well as Holter monitoring at 3, 6, 9, and 12 months post-ablation. Healthcare resource utilization, clinical data, complications, patients' medical complaints related to the ablation procedure and patient's reported outcome measures will be prospectively traced and evaluated.

DISCUSSION

The DELETE AF trial will provide additional knowledge on long-term outcome following a structured ablation workflow, with high density mapping, advanced algorithms and local impedance technology, in an international multicentric fashion. DELETE AF is registered at ClinicalTrials.gov (NCT05005143).

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.

Comparison of clockwise and counterclockwise right atrial flutter using high-resolution mapping and automated velocity measurements

BACKGROUND

Only few studies have been performed that explore the electrophysiological differences between clockwise (CW) and counterclockwise (CCW) right atrial (RA) cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) using the high-resolution Rhythmia mapping system.

OBJECTIVES

We sought to compare CW and CCW CTI-dependent AFL in pure right AFL patients (pts) using the ultra-high-definition (ultra-HD) Rhythmia mapping system and we mathematically developed a cartography model based on automatic velocity RA measurements to identify electrophysiological AFL specificities.

METHODS AND RESULTS

Thirty-three pts were recruited. The mean age was 71 ± 13 years old. The sinus venosus (SV) block line was present in 32/33 of cases (97%) and no significant difference was found between CCW and CW CTI AFL (100% vs. 91%; p = .7). No line was localized in the region of the crista terminalis (CT). A superior gap was present in the posterior line in 14/31 (45.2%) but this was similarly present in CCW AFL, when compared to CW AFL (10/22 [45.5%] vs. 4/10 [40%]; p = .9). When present, the extension of the posterior line of block was observed in 18/31 pts (58%) without significant differences between CCW and CW CI AFL (12/22 [54.5%] vs. 6/10 [60%]; p = .9) The Eustachian ridge line of block was similarly present in both groups (82% [18/22] vs. 45.5% [5/11]; p = .2). The absence of the Eustachian ridge line of block led to significantly slowed velocity in this area (28 ± 10 cm/s; n = 8), and the velocities were similarly altered between both groups (26 ± 10 [4/22] vs. 29.8 ± 11 cm/s [4/11]; p = .6). We created mathematical, three-dimensional RA reconstruction-velocity model measurements. In each block localization, when the block line was absent, velocity was significantly slowed (≤20 cm/s). A systematic slowdown in conduction velocity was observed at the entrance and exit of the CTI in 100% of cases. This alteration to the conduction entrance was localized at the lateral side of the CTI for the CCW AFL and at the septal side of the CTI for CW AFL. The exit-conduction alteration was localized at the CTI septal side for the CCW AFL and at the CTI lateral side for the CW AFL.

CONCLUSION

The ultra-HD Rhythmia mapping system confirmed the absence of significant electrophysiological differences between CCW and CW AFL. The mechanistic posterior SV and Eustachian ridge block lines were confirmed in each arrhythmia. A systematic slowing down at the entrance and exit of the CTI was demonstrated in both CCW and CW AFL, but in reverse positions.

Specific electrogram characteristics impact substrate ablation target area in patients with scar-related ventricular tachycardia-insights from automated ultrahigh-density mapping

INTRODUCTION

Substrate-based catheter ablation approaches to ventricular tachycardia (VT) focus on low-voltage areas and abnormal electrograms. However, specific electrogram characteristics in sinus rhythm are not clearly defined and can be subject to variable interpretation. We analyzed the potential ablation target size using automatic abnormal electrogram detection and studied findings during substrate mapping in the VT isthmus area.

METHODS AND RESULTS

Electrogram characteristics in 61 patients undergoing scar-related VT ablation using ultrahigh-density 3D-mapping with a 64-electrode mini-basket catheter were analyzed retrospectively. Forty-four complete substrate maps with a mean number of 10319 ± 889 points were acquired. Fractionated potentials detected by automated annotation and manual review were present in 43 ± 21% of the entire low-voltage area (<1.0 mV), highly fractionated potentials in 7 ± 8%, late potentials in 13 ± 15%, fractionated late potentials in 7 ± 9% and isolated late potentials in 2 ± 4%, respectively. Highly fractionated potentials (>10 ± 1 fractionations) were found in all isthmus areas of identified VT during substrate mapping, while isolated late potentials were distant from the critical isthmus area in 29%.

CONCLUSION

The ablation target area varies enormously in size, depending on the definition of abnormal electrograms. Clear linking of abnormal electrograms with critical VT isthmus areas during substrate mapping remains difficult due to a lack of specificity rather than sensitivity. However, highly fractionated, low-voltage electrograms were found to be present in all critical VT isthmus sites.

Spatial phase discontinuity at the center of moving cardiac spiral waves

BACKGROUND

Precise analysis of cardiac spiral wave (SW) dynamics is essential for effective arrhythmia treatment. Although the phase singularity (PS) point in the spatial phase map has been used to determine the cardiac SW center for decades, quantitative detection algorithms that assume PS as a point fail to trace complex and rapid PS dynamics. Through a detailed analysis of numerical simulations, we examined our hypothesis that a boundary of spatial phase discontinuity induced by a focal conduction block exists around the moving SW center in the phase map.

METHOD

In a numerical simulation model of a 2D cardiac sheet, three different types of SWs (short wavelength; long wavelength; and low excitability) were induced by regulating ion channels. Discontinuities of all boundaries among adjacent cells at each instance were evaluated by calculating the phase bipolarity (PB). The total amount of phase transition (PTA) in each cell during the study period was evaluated.

RESULTS

Pivoting, drifting, and shifting SWs were observed in the short-wavelength, low-excitability, and long-wavelength models, respectively. For both the drifting and shifting cases, long high-PB edges were observed on the SW trajectories. In all cases, the conduction block (CB) was observed at the same boundaries. These were also identical to the boundaries in the PTA maps.

CONCLUSIONS

The analysis of the simulations revealed that the conduction block at the center of a moving SW induces discontinuous boundaries in spatial phase maps that represent a more appropriate model of the SW center than the PS point.

Scar identification, quantification, and characterization in complex atrial tachycardia: a path to targeted ablation?

Successful catheter ablation of scar-related atrial tachycardia depends on correct identification of the critical isthmus. Often, this is a represented by a small bundle of viable conducting tissue within a low-voltage area. It's identification depends on the magnitude of the signal/noise ratio. Ultra-high density mapping, multipolar catheters with small (eventually unidirectional) and closely-spaced electrodes improves low-voltage electrogram detection. Background noise limitation is also of major importance for improving the signal/noise ratio. Electrophysiological properties of the critical isthmus and the characteristics of the local bipolar electrograms have been recently demonstrated as hallmarks of successful ablation sites in the setting of scar-related atrial tachycardia.

Multilayer fabrication of durable catheter-deployable soft robotic sensor arrays for efficient left atrial mapping

Devices that perform cardiac mapping and ablation to treat atrial fibrillation provide an effective means of treatment. Current devices, however, have limitations that either require tedious point-by-point mapping of a cardiac chamber or have limited ability to conform to the complex anatomy of a patient's cardiac chamber. In this work, a detailed, scalable, and manufacturable technique is reported for fabrication of a multielectrode, soft robotic sensor array. These devices exhibit high conformability (~85 to 90%) and are equipped with an array of stretchable electronic sensors for voltage mapping. The form factor of the device is intended to match that of the entire left atrium and has a hydraulically actuated soft robotic structure whose profile facilitates deployment from a 13.5-Fr catheter. We anticipate that the methods described in this paper will serve a new generation of conformable medical devices that leverage the unique characteristics of stretchable electronics and soft robotics.

High-density mapping in patients undergoing ablation of atrial fibrillation with the fourth-generation cryoballoon and the new spiral mapping catheter

AIMS

To assess the value of high-density mapping (HDM) in revealing undetected incomplete pulmonary vein isolation (PVI) after the fourth-generation cryoballoon (CB4G) ablation compared to the previous cryoballoon's versions.

METHODS AND RESULTS

Consecutive patients with paroxysmal or early-persistent atrial fibrillation (AF) undergoing CB ablation as the index procedure, assisted by HDM, were retrospectively included in this study. A total of 68 patients (52 males; mean age: 60 ± 12 years, 58 paroxysmal AF) were included, and a total of 272 veins were mapped. Fourth-generation cryoballoon with the new spiral mapping catheter (SMC) was used in 35 patients (51%). Time to PVI was determined in 102/132 (77%) and in 112/140 (80%) veins during second-generation cryoballoon/third-generation cryoballoon (CB2G/CB3G) and CB4G ablation, respectively (P = 0.66). There was a statistically significant difference in terms of discrepancy rate between the SMC and the mini-basket catheter in PV detection after CB4G and CB2G/CB3G ablation(1.4% vs. 7.6%; P = 0.01). A total of 57 patients (84%) remained free of symptomatic AF during a mean follow-up of 9.8 ± 4.6 months.

CONCLUSION

High-density mapping after cryoballoon ablation using CB4G and the new SMC identifies incomplete PVI, not detected by the new SMC, in a significantly lower proportion of veins compared to HDM performed after the other generation CB ablation.

Is the mid-diastolic isthmus always the best ablation target for re-entrant atrial tachycardias?

AIMS

We evaluated the ability of an ultrahigh mapping system to identify the most convenient Rhythmia ablation target (RAT) in intra-atrial re-entrant tachycardias (IART) in terms of the narrowest area to transect to interrupt the re-entry.

METHODS

A total of 24 consecutive patients were enrolled with a total of 26 IARTs. The Rhythmia mapping system was used to identify the RAT in all IARTs.

RESULTS

In 18 cases the RAT matched the mid-diastolic phase of the re-entry whereas in 8 cases the RAT differed. In these patients, the mid-diastolic tissue in the active circuit never represented the area with the slowest conduction velocity of the re-entry. The mean conduction velocity at the mid-diastolic site was significantly slower in the group of patients in which the RAT matched the mid-diastolic site (P = 0.0173) and that of the remaining circuit was significantly slower in the group in which the RAT did not match (P = 0.0068). The mean conduction velocity at the RAT was comparable between the two groups (P = 0.66).

CONCLUSION

Identifying the RAT in challenging IARTs by means of high-density representation of the wavefront propagation of the tachycardia seems feasible and effective. In one-third of cases this approach identifies an area that differs from the mid-diastolic corridor.

Basket catheter-guided ultra-high-density mapping of cardiac arrhythmias: a systematic review and meta-analysis

Aim: Ultra-high-density mapping (HDM) is increasingly used for guidance of catheter ablation in cardiac arrhythmias. While initial results are promising, a systematic evaluation of long-term outcome has not been performed so far. Methods: A systematic review and meta-analysis was conducted on studies investigating long-term outcome after Rhythmia HDM-guided atrial fibrillation (AF) or atrial tachycardia catheter ablation. Results: Beyond multiple studies providing novel insights into arrhythmia mechanisms, follow-up data from 17 studies analyzing Rhythmia HDM-guided ablation (1768 patients, 49% with previous ablation) were investigated. Cumulative acute success was 100/90.2%, while 12 months long-term pooled success displayed at 71.6/71.2% (AF/atrial tachycardia). Prospective data are limited, showing similar outcome between HDM-guided and conventional AF ablation. Conclusion: Acute results of HDM-guided catheter ablation are promising, while long-term success is challenged by complex arrhythmogenic substrates. Prospective randomized trials investigating different HDM-guided ablation strategies are warranted and underway.

Catheter Ablation of Atrial Fibrillation: State of the Art and Future Perspectives

PURPOSE OF REVIEW

Atrial fibrillation (AF), the most common sustained arrhythmia, is associated with high rates of morbidity and mortality. Maintenance of stable sinus rhythm (SR) is the intended treatment target in symptomatic patients, and catheter ablation aimed at isolating the pulmonary veins provides the most effective treatment option, supported by encouraging clinical outcome data. A variety of energy sources and devices have been developed and evaluated. In this review, we summarize the current state of the art of catheter ablation of AF and describe future perspectives.

RECENT FINDINGS

Catheter ablation is a well-established treatment option for patients with symptomatic AF and is more successful at maintaining SR than antiarrhythmic drugs. Antral pulmonary vein isolation (PVI) as a stand-alone ablation strategy results in beneficial clinical outcomes and is therefore recommended as first-line strategy for both paroxysmal and persistent AF. While radiofrequency-based PVI in conjunction with a three-dimensional mapping system was for many years considered to be the "gold standard", the cryoballoon has emerged as the most commonly used alternative AF ablation tool, especially in patients with paroxysmal AF. Patients with persistent or long-standing persistent AF and with arrhythmia recurrence after previous PVI may benefit from additional ablation strategies, such as substrate modification of various forms or left atrial appendage isolation. New technologies and techniques, such as identification of the AF sources and magnetic resonance imaging-guided substrate modification, are on the way to further improve the success rates of catheter ablation for selected patients and might help to further reduce arrhythmia recurrence.

CONCLUSIONS

Pulmonary vein isolation is the treatment of choice for symptomatic patients with paroxysmal and persistent drug-refractory AF. The reconnection of previously isolated pulmonary veins remains the major cause of AF recurrence. Novel ablation tools, such as balloon technologies or alternative energy sources, might help to overcome this limitation. Patients with non-paroxysmal AF and with AF recurrence might benefit from alternative ablation strategies. However, further studies are warranted to further improve our knowledge of the underlying mechanisms of AF and to obtain long-term clinical outcomes on new ablation techniques.

Differential Atrial Pacing to Detect Reconnection Gaps After Pulmonary Vein Isolation in Atrial Fibrillation

High-resolution mapping is useful to identify reconnection gaps in the pulmonary vein after pulmonary vein isolation for atrial fibrillation. However, it is sometimes difficult to differentiate pulmonary vein potentials from far-field potentials because of very low amplitudes. Our purpose was to evaluate the usefulness of a novel differential atrial pacing method to differentiate reconnected pulmonary vein potentials from isolated pulmonary vein potentials. This retrospective observational study included 34 patients with atrial fibrillation (22 men; mean age, 64 ± 14 years; 28 with paroxysmal atrial fibrillation) who underwent radiofrequency or cryoballoon ablation. Following pulmonary vein isolation, we created a high-resolution activation map during pacing from both the coronary sinus and left atrial appendage. We compared the characteristics of the pulmonary vein potentials and the pattern of activation between the reconnected and isolated pulmonary veins. We analyzed 131 pulmonary veins and found reconnections in 41 pulmonary veins (R group); 90 pulmonary veins had no reconnection (NR group). The R group had a significantly shorter distance between the earliest pulmonary vein activation sites in both activation maps, compared with the NR group (5.22 ± 0.53 mm versus 17.08 ± 0.36 mm, respectively; P < 0.0001). The amplitude of the pulmonary vein potentials was higher in the R group versus the NR group (0.61 ± 0.05 mV versus 0.04 ± 0.03 mV, respectively; P < 0.0001). Six gaps (14%) in the R group that were unrecognized using a conventional method were identified using our novel method. In conclusion, differential atrial pacing was useful to identify pulmonary vein reconnection gaps during ablation using a novel high-resolution mapping system.

[Catheter ablation of atrial fibrillation : Status quo]

Catheter ablation of atrial fibrillation (AF) is a standard part of treatment with respect to rhythm control. In this article, the authors provide a review of the state-of-the-art knowledge of AF catheter ablation including current indications, possible energy forms, procedural methods and endpoints as well as follow-up and further anticoagulation.

Impact of mapping points in high-density mapping of the left atrium

PURPOSE

Currently, high-density mapping techniques are being discussed for more precise voltage mapping, lesion validation after pulmonary vein isolation (PVI) and superior left atrial tachycardia (LAT) mapping. However, the quality of high-density maps varies according to different mapping systems, multipolar catheter (MPC) types and numbers of mapping points. The aim of this study was to evaluate the impact of different numbers of mapping points in high-density mapping on validity.

METHODS

From February 2016 to August 2018, 154 patients with previous PVI ablation and recurrent atrial fibrillation (AF) or left atrial tachycardia (LAT) were mapped by Orion™ multipolar catheter and Rhythmia HDx™ mapping system at our centre. Of those, 90 maps from 25 patients [11 male patients/14 female patients; age 76 ± 12 years] with 8000 to 16,000 mapping points in the primary map were collected. All maps were evaluated offline by two independent and blinded electrophysiologists regarding the following issues: (1) Is PVI observable in all veins? (2) Does voltage map cover the whole left atrium? (3) Does activation map display one or more isthmuses? The 90 maps consist of 30 maps with deactivated 24 of 64 electrodes of MPC with < 1000 mapping points (A), 30 maps with deactivated 16 of 64 electrodes of MPC and 2000 to 6000 mapping points (B) and 30 primary maps with 8000 to 16,000 mapping points (C).

RESULTS

For (A), only in one map (3.3%), for (B) in 20 maps (66.7%, p < 0.05) and for (C) in 24 maps (80%) both investigators agreed with evaluable PVI in all veins. Investigators were able to assess whether the voltage map covered the whole left atrium and the same low voltage areas in (A) in 0 maps, in (B) in 16 maps (53%, p < 0.05) and in (C) in 23 maps (77%, p < 0.05). Also, investigators were able to locate the same critical isthmuses in the activation maps in (A) in 0 maps, in (B) in 2 maps (7%) and in (C) in 20 maps (67%, p < 0.05).

CONCLUSIONS

In order to achieve comparable high-density maps which are verified by independent investigators, a minimum of 2000 to 6000 mapping points are required in the majority of voltage maps to evaluate PVI and low voltage areas. To define the critical isthmuses in activations maps, 8000 mapping points or more might be necessary. High-density maps with more than 8000 points increase the interrater reliability.

Advanced mapping strategies for ablation therapy in adults with congenital heart disease

Background

Ultra-high density mapping (HDM) is a promising tool in the treatment of patients with complex arrhythmias. In adults with congenital heart disease (CHD), rhythm disorders are among the most common complications but catheter ablation can be challenging due to heterogenous anatomy and complex arrhythmogenic substrates. Here, we describe our initial experience using HDM in conjunction with novel automated annotation algorithms in patients with moderate to great CHD complexity.

Methods

We studied a series of consecutive adult patients with moderate to great CHD complexity and an indication for catheter ablation due to symptomatic arrhythmia. HDM was conducted using the Rhythmia™ mapping system and a 64-electrode mini-basket catheter for identification of anatomy, voltage, activation pattern and critical areas of arrhythmia for ablation guidance. To investigate novel advanced mapping strategies, postprocedural signal processing using the Lumipoint™ software was applied.

Results

In 19 patients (53±3 years; 53% male), 21 consecutive ablation procedures were conducted. Procedures included ablation of atrial fibrillation (n=7; 33%), atrial tachycardia (n=11; 52%), atrioventricular accessory pathway (n=1; 5%), the atrioventricular node (n=1; 5%) and ventricular arrhythmias (n=4; 19%). A total of 23 supraventricular and 8 ventricular arrhythmias were studied with the generation of 56 complete high density maps (atrial n=43; ventricular n=11, coronary sinus n=2) and an average of 12,043±1,679 mapping points. Multiple arrhythmias were observed in n=7 procedures (33% of procedures; range of arrhythmias detected 2-4). A total range of 1-4 critical areas were defined per procedure and treated within a radiofrequency application time of 16 (interquartile range 12-45) minutes. Postprocedural signal processing using Lumipoint™ allowed rapid annotation of fractionated signals within specific windows of interest. This supported identification of a practical critical isthmus in 20 out of 27 completed atrial and ventricular tachycardia activation maps.

Conclusions

Our findings suggest that HDM in conjunction with novel automated annotation algorithms provides detailed insights into arrhythmia mechanisms and might facilitate tailored catheter ablation in patients with moderate to great CHD complexity.

High-density Mapping Guided Pulmonary Vein Isolation for Treatment of Atrial Fibrillation - Two-year clinical outcome of a single center experience

Pulmonary vein isolation (PVI) as interventional treatment for atrial fibrillation (AF) aims to eliminate arrhythmogenic triggers from the PVs. Improved signal detection facilitating a more robust electrical isolation might be associated with a better outcome. This retrospective cohort study compared PVI procedures using a novel high-density mapping system (HDM) with improved signal detection vs. age- and sex-matched PVIs using a conventional 3D mapping system (COM). Endpoints comprised freedom from AF and procedural parameters. In total, 108 patients (mean age 63.9 ± 11.2 years, 56.5% male, 50.9% paroxysmal AF) were included (n = 54 patients/group). Our analysis revealed that HDM was not superior regarding freedom from AF (mean follow-up of 494.7 ± 26.2 days), with one- and two-year AF recurrence rates of 38.9%/46.5% (HDM) and 38.9%/42.2% (COM), respectively. HDM was associated with reduction in fluoroscopy times (18.8 ± 10.6 vs. 29.8 ± 13.4 min; p < 0.01) and total radiation dose (866.0 ± 1003.3 vs. 1731.2 ± 1978.4 cGy; p < 0.01) compared to the COM group. HDM was equivalent but not superior to COM with respect to clinical outcome after PVI and resulted in reduced fluoroscopy time and radiation exposure. These results suggest that HDM-guided PVI is effective and safe for AF ablation. Potential benefits in comparison to conventional mapping systems, e.g. arrhythmia recurrence rates, have to be addressed in randomized trials.

A decade of catheter ablation of cardiac arrhythmias in Sweden: ablation practices and outcomes

AIMS

Catheter ablation is considered the treatment of choice for many tachyarrhythmias, but convincing 'real-world' data on efficacy and safety are lacking. Using Swedish national registry data, the ablation spectrum, procedural characteristics, as well as ablation efficacy and reported adverse events are reported.

METHODS AND RESULTS

Consecutive patients (≥18 years of age) undergoing catheter ablation in Sweden between 01 January 2006 and 31 December 2015 were included in the study. Follow-up (repeat ablation and vital status) was collected through 31 December 2016. A total of 26 642 patients (57 ± 15 years, 62% men), undergoing a total of 34 428 ablation procedures were included in the study. In total, 4034 accessory pathway/Wolff-Parkinson-White syndrome (12%), 7358 AV-nodal re-entrant tachycardia (21%), 1813 atrial tachycardia (5.2%), 5481 typical atrial flutter (16%), 11 916 atrial fibrillation (AF, 35%), 2415 AV-nodal (7.0%), 581 premature ventricular contraction (PVC, 1.7%), and 964 ventricular tachycardia (VT) ablations (2.8%) were performed. Median follow-up time was 4.7 years (interquartile range 2.7-7.0). The spectrum of treated arrhythmias changed over time, with a gradual increase in AF, VT, and PVC ablation (P < 0.001). Decreasing procedural times and utilization of fluoroscopy with time, were seen for all arrhythmia types. The rates of repeat ablation differed between ablation types, with the highest repeat ablation seen in AF (41% within 3 years). The rate of reported adverse events was low (n = 595, 1.7%). Death in the immediate period following ablation was rare (n = 116, 0.34%).

CONCLUSION

Catheter ablations have shifted towards more complex procedures over the past decade. Fluoroscopy time has markedly decreased and the efficacy of catheter ablation seems to improve for AF.

Differences in scar lesion formation between radiofrequency and cryoballoon in atrial fibrillation ablation: a comparison study using ultra-high-density mapping

Aims

Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is usually associated to conduction gaps in pulmonary veins (PVs). Our objective was to characterize gaps in patients with recurrences after a first radiofrequency (RF) or cryoballoon (CB) PVI procedure, using a high-density mapping (HDM) system.

Methods and results

Fifty patients with AF recurrence after a first PVI procedure (pre-RF 25 patients; pre-CB 25 patients) were included at two centres. Activation map (AM) and voltage map (VM) of the left atrium and PVs were built using the HDM Rhythmia® system. Superior PVs were reconnected more frequently in both groups. Right PVs were reconnected more frequently in pre-RF patients. Pre-RF patients had more reconnected veins than pre-CB patients (mean ± standard deviation: 3.00 ± 0.96 vs. 1.88 ± 1.13; P < 0.001) and more gaps (4.84 ± 2.06 vs. 2.16 ± 1.49; P < 0.001). Gaps in the VM were wider in pre-CB patients (16.5 ± 9.5 mm vs. 12.1 ± 4.8 mm; P = 0.006). There was a gap in 179 of the 800 PV segments analysed (22%); 52% were identified in both AM and VM maps; 39% only in the AM and 8% only in the VM. The highest sensitivity and specificity for gap detection was obtained with VM in pre-CB patients and with AM in pre-RF patients.

Conclusion

In conclusion, HDM seems to be a useful and precise tool to detect conduction gaps after a first PVI procedure. The anatomical pattern and location of gaps depends on the technique used previously, usually being multiple, smaller, and better detected by AM after RF, and fewer, wider, and better detected by VM after CB.

An initial experience of high-density mapping-guided ablation in a cohort of patients with adult congenital heart disease

AIMS

In the management of both ventricular and supraventricular tachycardia in patients with congenital heart disease (CHD) catheter ablation has now been recognized as one of the mainstays.

METHODS AND RESULTS

We review our initial experience of using the Rhythmia mapping system in a cohort of 12 adult CHD patients presenting with multiple arrhythmia substrates. A total of 78 arrhythmia maps were attempted in a total of 15 procedures, but possible due to the dilatation of the target chamber only 44% of maps were able to reconstruct the entire arrhythmia. All patients underwent pre-procedure 3D imaging (either cardiac magnetic resonance or computed tomography), but image integration was suboptimal. A median of two maps per patient were finally analysed and acquisition took in median 22 min with a median number of 12 574 (8230-18 167) mapping points. Procedural data with a total duration amounting to in median 285 (194-403) min, with a median total fluoroscopy exposure of 7.5 (5.2-10.7) min. After a median of 1.5 procedures [median of 12 (8-16 months)], nine patients remained in stable sinus rhythm or atrial paced rhythm, while three patients had further sustained recurrences. One of these passed away in end-staged heart failure.

CONCLUSION

This initial experience of using high-density mapping for arrhythmia management in patients with CHD allowed rapid acquisition of multiple maps with high accuracy to identify surgical scars and fibrosis, however, it was limited by large atrial volumes and a high percentage of incomplete maps resulting in modest clinical success.

Is it feasible to offer 'targeted ablation' of ventricular tachycardia circuits with better understanding of isthmus anatomy and conduction characteristics?

Successful mapping and ablation of ventricular tachycardias remains a challenging clinical task. Whereas conventional entrainment and activation mapping was for many years the gold standard to identify reentrant circuits in ischaemic ventricular tachycardia ablation procedures, substrate mapping has become the cornerstone of ventricular tachycardia ablation. In the last decade, technology has dramatically improved. In parallel to high-density automated mapping, cardiac imaging and image integration tools are increasingly used to assess the structural ventricular tachycardia substrate. The aim of this review is to describe the technologies underlying these new mapping systems and to discuss their possible role in providing new insights into identification and visualization of reentrant tachycardia mechanisms.

Repeat ablation for paroxysmal atrial fibrillation - Does adenosine play a role in predicting pulmonary vein reconnection patterns?

BACKGROUND

Pulmonary vein (PV) reconduction after PV isolation (PVI) unmasked by adenosine is associated with a higher risk for paroxysmal atrial fibrillation (PAF) recurrence. It is unknown if the reconnected PVs after adenosine testing and immediate re-ablation can predict reconnection and reconnection patterns of PVs at repeat procedures. We assessed reconnection of PVs with and without dormant-conduction (DC) during the first and the repeat procedure.

METHODS

We included 67 patients undergoing PVI for PAF and a second procedure for PAF recurrence. DC during adenosine administration at first procedure was seen in 31 patients (46%). 264 PVs were tested with adenosine; DC was found in 48 PVs (18%) and re-ablated during first procedure. During the second procedure, all PVs where checked for reconnection.

RESULTS

Fifty-eight patients (87%) showed PV reconnection during the second procedure. Reconnection was found in 152/264 PVs (58%). Of 216 PVs without reconnection during adenosine testing at the first ablation, 116 PVs (53.7%) showed reconnection at the repeat procedure. Overall, 14.9% of patients showed the same PV reconnection pattern in the first and second procedure, expected statistical probability of encountering the same reconnection pattern was only 6.6%(p = 0.012).

CONCLUSIONS

In repeat procedures PVs showed significantly more often the same reconnection pattern as during first procedure than statistically expected. More than 50% of initial isolated PVs without reconnection during adenosine testing showed a reconnection during repeat ablation. Techniques to detect susceptibility for PV re-connection like prolonged waiting-period should be applied. Elimination of DC should be expanded from segmental to circumferential re-isolation or vaster RF application.

Value of high-resolution mapping in optimizing cryoballoon ablation of atrial fibrillation

BACKGROUND

Unrecognized incomplete pulmonary vein isolation (PVI), as opposed to post-PVI pulmonary vein reconnection, may be responsible for clinical recurrences of atrial fibrillation (AF). To date, no data are available on the use of high-resolution mapping (HRM) during cryoballoon (CB) ablation for AF as the index procedure. The aims of this study were: - to assess the value of using a HRM system during CB ablation procedures in terms of ability in acutely detecting incomplete CB lesions; - to compare the 8-pole circular mapping catheter (CMC, Achieve) and the 64-pole mini-basket catheter (Orion) with respect to pulmonary vein (PV) signals detection at baseline and after CB ablation; - to characterize the extension of the lesion produced by CB ablation by means of high-density voltage mapping.

METHODS

Consecutive patients with drug-resistant paroxysmal or early-persistent AF undergoing CB ablation as the index procedure, assisted by a HRM system, were retrospectively included in this study.

RESULTS

A total of 33 patients (25 males; mean age: 59 ± 18 years, 28 paroxysmal AF) were included. At baseline, CMC catheter revealed PV activity in 102 PVs (77%), while the Orion documented PV signals in all veins (100%). Failure of complete CB-PVI was more frequently revealed by atrial re-mapping with the Orion as compared to the Achieve catheter (24% vs 0%, p < 0.05). A repeat ablation was performed in 8 patients (24%). In 9% of cases, the Orion catheter detected far-field signals originating from the right atrium. Quantitative assessment of the created lesion revealed a significant reduction of the left atrial area having voltage >0.5 mV. A total of 29 patients (88%) remained free of symptomatic AF during a mean follow-up of 13.2 ± 3.7 months.

CONCLUSION

Atrial re-mapping after CB ablation by means of a HRM system improves the detection of areas of incomplete ablation, characterizes the extension of the cryo-ablated tissue and can identify abolishment of potential non-PVI related sources of AF.

Detailed comparison between the wall thickness and voltages in chronic myocardial infarction

BACKGROUND

The relationship between the local electrograms (EGMs) and wall thickness (WT) heterogeneity within infarct scars has not been thoroughly described. The relationship between WT and voltages and substrates for ventricular tachycardia (VT) was examined.

METHODS

In 12 consecutive patients with myocardial infarction and VT, WT, defined by a multidetector computed tomography, and voltage were compared. In multicomponent EGMs, amplitudes of both far- and near-field components were manually measured, and the performance of the three-dimensional-mapping system automatic voltage measurement was assessed.

RESULTS

Of 15 748 points acquired, 2677 points within 5 mm of the endocardial surface were analyzed. In total, 909 (34.0%) multicomponent EGMs were identified; 785 (86.4%) and 883 (97.1%) were distributed in the WT less than 4 and 5 mm, respectively. Far-field EGM voltages increased linearly from 0.14 mV (0.08-0.28 mV) in the WT: 0 to 1 mm to 0.70 mV (0.43-2.62 mV) in the WT: 4 to 5 mm (ρ = 0.430; P < 0.001), and a significant difference was demonstrated between any two WT-groups (P ≤ 0.001). In contrast, near-field EGM voltages varied from 0.27 mV (0.11-0.44 mV) in the WT: 0 to 1 mm to 0.29 mV (0.17-0.53 mV) in the WT: 4 to 5 mm with a poorer correlation (ρ = 0.062, P = 0.04). The proportion of points where the system automatically measured the voltage on near-field EGMs increased from less than 10% in areas of WT: 4 to 5 mm to 50% in areas less than 2 mm. Of 21 VTs observed, seven hemodynamically stable VTs were mapped and terminated in WT: 1 to 4 mm area.

CONCLUSIONS

Although far-field voltages gradually increase with the WT, near-field does not. The three-dimensional-mapping system preferentially annotates the near-field components in thinner areas (center of the scar) and the far-field component in thicker areas when building a voltage map. Critical sites of VT are distributed in WT: 1 to 4 mm areas.

[High-resolution 3D mapping : Opportunities and limitations of the Rhythmia™ mapping system]

Three-dimensional mapping systems are used for the characterization and treatment of complex arrhythmias, such as atrial reentrant tachycardias, atrial fibrillation, or ventricular tachycardia. The Rhythmia™ mapping system (Boston Scientific, Natick, MA, USA) belongs to a novel generation of mapping systems that are able to rapidly create high-density and high-resolution three-dimensional maps in an automated manner. Mapping is performed with a magnetic- and impedance-based tracked bidirectional deflectable 64-pole basket catheter (IntellaMap Orion™, Boston Scientific). Based on previous studies, the system is effective and safe for the treatment of complex atrial and ventricular arrhythmias.

Initial single centre experience with the novel Rhythmia© high density mapping system in an all comer collective of 400 electrophysiological patients

BACKGROUND

A novel, automatically annotating ultra-high density mapping system (Rhythmia©, Boston Scientific) collects a high number and quality of electrograms (EGMs). So far, data on general use in the electrophysiological laboratory are sparse.

METHODS

We retrospectively analyzed all our ablations using Rhythmia and recorded patient clinical data, procedural parameters, and mapping parameters including the count of EGMs, mapping time, and mapping volume. Where appropriate, procedural parameters were compared over time to assess a learning curve.

RESULTS

400 patients underwent ablation of atrial fibrillation (n = 202), typical (n = 16) or atypical atrial flutter (n = 49), VT (n = 48), PVC (n = 35), accessory pathways (n = 14), AVNRT (n = 4), and focal atrial tachycardia (n = 32). System use was feasible, as no procedure had to be stopped for technical reasons and no ablation had to be withheld because of mapping failure, and safe, with an overall complication rate of 2.25%. Initial restrictions in manoeuvrability of the mapping catheter were overcome rapidly, as indicated by a significant decrease of fluoroscopy time (20 vs. 14 min, p = 0.02), use of contrast agent (50 vs. 40 ml; p < 0.01), and (not significant) lower procedure times (194 vs. 170 min; p = 0.12; comparing the first with the last third of patients undergoing pulmonary vein isolation only procedure). Ablation of complex left atrial, focal and ventricular tachycardias benefited from the reliable automatic annotation of a high number of EGMs.

CONCLUSION

The use of the Rhythmia is feasible and safe. Initial restrictions in manoeuvrability of the Orion mapping catheter were overcome rapidly. The procedures that benefit the most from ultra-high density mapping are complex left atrial tachycardias, focal tachycardias, and ventricular tachycardias.

[Modern mapping technologies : Technical background and clinical use]

Successful mapping and ablation of arrhythmias can be a challenging clinical task. For many years, conventional pacing maneuvers and activation mapping were the gold standard to identify underlying arrhythmia mechanisms in ablation procedures. In the last decade, technology has dramatically improved. In parallel to high-density automated mapping, cardiac imaging and image integration tools are increasingly used to assess the arrhythmia substrate and identify reentrant circuits. The aim of this review is to describe the technologies underlying these new mapping systems and to discuss their possible role in providing new insights into identification and visualization of arrhythmia mechanisms.