Rapid acquisition of high-resolution electroanatomical maps using a novel multielectrode mapping system

Uniform slow conduction during sinus rhythm and low voltage/low voltage gradient ΔV/V characterize the VT isthmus location

BACKGROUND

Reentrant ventricular tachycardia (VT) properties require further elucidation.

OBJECTIVE

To understand circuit mechanisms and improve ablation targeting.

METHODS

In postinfarction VT patients undergoing electrophysiology study and catheter ablation, high-density endocardial electrogram contact mapping data was acquired during sinus rhythm (n = 6) and during VT (n = 12) and annotated by the system. Bipolar endocardial VT voltage was used to compute the voltage gradient, ΔV/V, at isthmus midline and at the lateral boundaries. Voltage was additionally represented as a depth as well as a color change, to better visualize level. Linear regression analysis was implemented to quantitate the sinus rhythm activation gradient along the isthmus long-axis midline, and along 3 other spokes originating from a last activation point.

RESULTS

The mean voltage along the isthmus long-axis was 0.234 ± 0.137 mV, vs 0.383 ± 0.290 mV aside boundaries (P < .001). The gradient ΔV/V along the isthmus long-axis was 0.425 ± 0.324, vs 0.823 ± 0.550 at boundaries (P < .001). Sinus rhythm activation was uniform (mean r2 = 0.93 ± 0.05) and slow (∇ = 0.16 ± 0.03 mm/msec) along the spoke coinciding with isthmus long-axis midline, vs less uniform (mean r2 = 0.32 ± 0.25) and rapid (∇ = 0.73 ± 0.62 mm/msec) along the other spokes (P < .001 and P = .003, respectively). Plotting r2 vs ∇, parameters of isthmus vs nonisthmus spokes were clearly separable.

CONCLUSION

A low-voltage trench coincides with the VT isthmus, vs abrupt voltage increase at the lateral boundaries, which may contravene prior definitions of conducting channels. Sinus rhythm uniform slow conduction occurs at the VT isthmus location, preventing circuit disruption while enabling the formation of an excitable gap to perpetuate reentry.

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.

Recent advances in the tools available for atrial fibrillation ablation

INTRODUCTION

Atrial fibrillation (AF) is the commonest arrhythmia in clinical practice with significant detrimental health impacts. Much effort has been spent in mapping AF, determine its triggers and drivers, and how to develop tools to eliminate these triggers.

AREAS COVERED

In this state of-the-art review article, we aim to highlight the recent techniques in catheter-based management of Atrial Fibrillation; including new advancements either in the catheter design or the software used. This includes a comprehensive summary of the most recent tools used in AF mapping and subsequent ablation.

EXPERT OPINION

Electrical isolation of the pulmonary veins has been developed and established as the cornerstone in AF ablation with good results in patients with paroxysmal AF (PAF) whilst new ablation tools are aimed at streamlining the procedure. However, the quest for persistent AF (PeAF) remains. The future of AF ablation, we believe, lies in identifying AF drivers by means of the new developing mapping tools and altering their electrical properties in a safe, reproducible, and effective manner.

Anatomical targets and expected outcomes of catheter-based ablation of atrial fibrillation in 2020

Anatomical-based approaches, targeting either pulmonary vein isolation (PVI) or additional extra PV regions, represent the most commonly used ablation treatments in symptomatic patients with atrial fibrillation (AF) recurrences despite antiarrhythmic drug therapy. PVI remains the main anatomical target during catheter-based AF ablation, with the aid of new technological advances as contact force monitoring to increase safety and effective radiofrequency (RF) lesions. Nowadays, cryoballoon ablation has also achieved the same level of scientific evidence in patients with paroxysmal AF undergoing PVI. In parallel, electrical isolation of extra PV targets has progressively increased, which is associated with a steady increase in complex cases undergoing ablation. Several atrial regions as the left atrial posterior wall, the vein of Marshall, the left atrial appendage, or the coronary sinus have been described in different series as locations potentially involved in AF initiation and maintenance. Targeting these regions may be challenging using conventional point-by-point RF delivery, which has opened new opportunities for coadjuvant alternatives as balloon ablation or selective ethanol injection. Although more extensive ablation may increase intraprocedural AF termination and freedom from arrhythmias during the follow-up, some of the targets to achieve such outcomes are not exempt of potential severe complications. Here, we review and discuss current anatomical approaches and the main ablation technologies to target atrial regions associated with AF initiation and maintenance.

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.

Ultra-rapid high-density mapping system with the phase singularity technique is feasible in identifying rotors and focal sources and predicting AF termination

INTRODUCTION

Phase singularity (PS) mapping provides additional insight into the AF mechanism and is accurate in identifying rotors. The study aimed to evaluate the feasibility of PS mapping in identifying AF rotors using data obtained from an automatic ultra-rapid high-resolution mapping system with a high-density mini-basket catheter.

METHODS

Twenty-three pigs underwent rapid right atrial (RA) pacing (RAP 480 bpm) for 5 weeks before the experiment. During AF, RA endocardial automatic continuous mappings with a mini-basket catheter were generated using an automatic ultra-rapid mapping system. Both fractionation mapping and waveform similarity measurements using a PS mapping algorithm were applied on the same recording signals to localize substrates maintaining AF.

RESULTS

Seventeen (74%) pigs developed sustained AF after RAP. Three were excluded because of periprocedural ventricular arrhythmia and corrupted digital data. RA fractionation maps were acquired with 6.17 ± 4.29 minutes mean acquisition time, 13768 ± 12698 acquisition points mapped during AF from 581 ± 387 beats. Fractionation mapping identified extensively distributed (66.7%) RA complex fractionated atrial electrogram (CFAE), whereas the nonlinear analysis identified high similarity index (SI > 0.7) parts in limited areas (23.7%). There was an average of 1.67 ± 0.87 SI sites with 0.43 ± 0.76 rotor/focal source/chamber. AF termination occurred in 11/16 (68.75%) AF events in 14 pigs during ablation targeting max CFAE. There was a higher incidence of rotor/focal source at AF termination sites compared with non-AF termination sites (54.5% vs 0%, P = 0.011).

CONCLUSIONS

The data obtained from ultra-rapid high-density automatic mapping is feasible and effective in identifying AF rotors/focal sources using PS technique, and those critical substrates were closely related to AF procedural termination.

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.

Novel automated point collection software facilitates rapid, high-density electroanatomical mapping with multiple catheter types

INTRODUCTION

Manual, point-by-point electroanatomical mapping requires the operator to directly evaluate each point during map construction. Consequently, point collection can be a slow process. An automated 3D mapping system was developed with the goal of improving key mapping metrics, including map completion time and point density.

METHODS

Automated 3D mapping software that includes morphology and cycle length discrimination functions for surface and intracardiac electrograms was developed. In five swine, electroanatomical maps (EAMs) of all four cardiac chambers were generated in sinus rhythm. Four catheters were used: two different four-pole ablation catheters, a 20-pole circular catheter, and a 64-pole basket catheter. Automated and manual 3D mapping were compared for 12 different catheter-chamber combinations (paired sets of 10 maps for most combinations, for a total of 156 maps).

RESULTS

Automated 3D mapping produced more than twofold increase in the number of points per map, as compared with manual 3D mapping (P ≤0.007 for all catheter-chamber combinations tested). Automated 3D mapping also reduced map completion time by an average of 29% (P < 0.05 for all comparisons). The amount of manual editing of the maps acquired with automated 3D mapping was minimal.

CONCLUSION

Automated 3D mapping with the open-platform mapping software described in this study is significantly faster than manual, point-by-point 3D mapping. This resulted in shorter mapping time and higher point density. The morphology discrimination functions effectively excluded ectopic beats during mapping in sinus rhythm and allowed for rapid mapping of intermittent ventricular ectopic beats.

The identification of conduction gaps after pulmonary vein isolation using a new electroanatomic mapping system

BACKGROUND

The reconnection of left atrial-pulmonary vein (LA-PV) conduction after the initial procedure of pulmonary vein (PV) isolation is not rare, and is one of the main cause of atrial fibrillation (AF) recurrence after PV isolation.

OBJECTIVE

We investigated feasibility of a new ultrahigh-resolution mapping system using a 64-pole small basket catheter for the identification of LA-PV conduction gaps.

METHODS

This prospective study included 31 consecutive patients (20 with persistent AF) undergoing a second ablation after a PV isolation procedure with LA-PV reconnected conduction at any of the 4 PVs. An LA-PV map was created using the mapping system, and ablation was performed at the estimated gap location.

RESULTS

The propagation map identified 54 gaps from 39 ipsilateral PV pairs, requiring manual electrogram reannotation for 23 gaps (43%). Gaps at the anterior and carinal regions of left and right ipsilateral PVs required manual electrogram reannotation more frequently than the other regions. The voltage map could identify the gap only in 19 instances (35%). Electrophysiological properties of the gaps (multiple gaps in the same ipsilateral PVs, conduction time, velocity, width, and length) did not differ between those needing and not needing manual electrogram reannotation. During the gap ablation, either the activation sequence alteration or elimination of PV potentials was observed using a circular catheter placed in the PV, suggesting that all the identified gaps were correct.

CONCLUSION

This new electroanatomic mapping system visualized all the LA-PV gaps in patients undergoing a second AF ablation.

Preprocessing of unipolar signals acquired by a novel intracardiac mapping system

The novel high-density mapping system Rhythmia TM Medical (Boston Scientific, Marlborough, USA) allows a fast and automatic acquisition of intracardiac electrograms (EGMs). For recording the ORION mini-basket catheter is used. Due to the small electrode surface, the spatial averaging is smaller than with other commonly used mapping catheters. This results in a higher quality of unipolar signals. However, these are still corrupted by noise such as high frequency interference. Within this project, methods were developed and benchmarked that can be applied to detect and remove these undesired components. An algorithm was implemented to detect and eliminate artificial peaks in the spectrum of the EGM. The filtered signals showed improved quality in time domain. The performance of the spectral peak detection resulted in a median sensitivity of 92.1% and in a median positive predictive value of 91.9%.

Contemporary Mapping Techniques of Complex Cardiac Arrhythmias - Identifying and Modifying the Arrhythmogenic Substrate

Cardiac electrophysiology has moved a long way forward during recent decades in the comprehension and treatment of complex cardiac arrhythmias. Contemporary electroanatomical mapping systems, along with state-of-the-art technology in the manufacture of electrophysiology catheters and cardiac imaging modalities, have significantly enriched our armamentarium, enabling the implementation of various mapping strategies and techniques in electrophysiology procedures. Beyond conventional mapping strategies, ablation of complex fractionated electrograms and rotor ablation in atrial fibrillation ablation procedures, the identification and modification of the underlying arrhythmogenic substrate has emerged as a strategy that leads to improved outcomes. Arrhythmogenic substrate modification also has a major role in ventricular tachycardia ablation procedures. Optimisation of contact between tissue and catheter and image integration are a further step forward to augment our precision and effectiveness. Hybridisation of existing technologies with a reasonable cost should be our goal over the next few years.

Correlation of scar in cardiac MRI and high-resolution contact mapping of left ventricle in a chronic infarct model

Background

Endocardial mapping for scars and abnormal electrograms forms the most essential component of ventricular tachycardia ablation. The utility of ultra‐high resolution mapping of ventricular scar was assessed using a multielectrode contact mapping system in a chronic canine infarct model.

Methods

Chronic infarcts were created in five anesthetized dogs by ligating the left anterior descending coronary artery. Late gadolinium‐enhanced magnetic resonance imaging (LGE MRI) was obtained 4.9 ± 0.9 months after infarction, with three‐dimensional (3D) gadolinium enhancement signal intensity maps at 1‐mm and 5‐mm depths from the endocardium. Ultra‐high resolution electroanatomical maps were created using a novel mapping system (Rhythmia Mapping System, Rhythmia Medical/Boston Scientific, Marlborough, MA, USA) Rhythmia Medical, Boston Scientific, Marlborough, MA, USA with an 8.5F catheter with mini‐basket electrode array (64 tiny electrodes, 2.5‐mm spacing, center‐to‐center).

Results

The maps contained 7,754 ± 1,960 electrograms per animal with a mean resolution of 2.8 ± 0.6 mm. Low bipolar voltage (<2 mV) correlated closely with scar on the LGE MRI and the 3D signal intensity map (1‐mm depth). The scar areas between the MRI signal intensity map and electroanatomic map matched at 87.7% of sites. Bipolar and unipolar voltages, compared in 592 electrograms from four MRI‐defined scar types (endocardial scar, epicardial scar, mottled transmural scar, and dense transmural scar) as well as normal tissue, were significantly different. A unipolar voltage of <13 mV correlated with transmural extension of scar in MRI. Electrograms exhibiting isolated late potentials (ILPs) were manually annotated and ILP maps were created showing ILP location and timing. ILPs were identified in 203 ± 159 electrograms per dog (within low‐voltage areas) and ILP maps showed gradation in timing of ILPs at different locations in the scar.

Conclusions

Ultra‐high resolution contact electroanatomical mapping accurately localizes ventricular scar and abnormal myocardial tissue in this chronic canine infarct model. The high fidelity electrograms provided clear identification of the very low amplitude ILPs within the scar tissue and has the potential to quickly identify targets for ablation.