Focal Impulse And Rotor Mapping Research Articles

Retrospective analysis of FIRM-guided ablation in patients with recurrent atrial fibrillation: asingle-center study.

Ablation of recurrent atrial fibrillation (AF) is common. Studies indicate that AF recurrence is primarily due to pulmonary vein (PV) re-conduction. This retrospective analysis characterized and evaluated recurrent AF patients using focal impulse and rotor mapping (FIRM) plus PV re-isolation, with follow up at3, 6, 12, and 24months after the repeat ablation. Patients (consecutive, n = 100) underwent FIRM-guided ablation followed by conventional PV re-isolation for recurrent AF treatment. All FIRM patients had failed one or more conventional ablation procedures (1.4 ± 0.08) for paroxysmal (14%), persistent (15%), and long-standing persistent (71%) AF. Stable rotors were identified in 97/100patients: 60% in the right atrium (RA) and 82% in left atrium (LA) (mean 1.5 ± 0.8 and 2.1 ± 1.2 per patient, respectively). No correlation was noted between the previous number of ablations, AF duration, or LA diameter to the number of rotors (R2 = 0.0039, R2 = 0.0017, and R2 = 0.006, respectively). In this limited observation, only 22% of identified rotors were associated with proximity to low voltage areas. The 12- and 24-month arrhythmia free rate was 93% (13/14) and 92% (12/13) for paroxysmal AF, 60% (9/15) and 47% (7/15) for persistent AF, and 70% (48/69) and 64% (43/67) for long-standing persistent AF, respectively, after asingle FIRM procedure and re-isolation of the veins. The data show abenefit for FIRM-guided ablation in recurrent AF at 12months. No correlation was found between rotors and tissue characterization, AF duration, or previous number of ablations, suggesting that rotors may play an independent role in maintaining recurrent AF after prior failed ablation.

Velocity characteristics of atrial fibrillation sources determined by electrographic flow mapping before and after catheter ablation

BackgroundElectrographic-Flow-(EGF)-Mapping is a novel method to identify Atrial Fibrillation (AF) drivers. Sources of excitation during AF can be characterized and monitored. ObjectiveThe aim of this study was to evaluate the correlation between velocity of EGF around a respective AF source and its spatial variability (SV) and stability (SST). Methods25 patients with AF were included in this study (persistent: n = 24, long-standing persistent: n = 1; mean age 70 ± 8.3 years, male: n = 17). Focal impulse and Rotor-Mapping (FIRM) was performed in addition to pulmonary vein isolation. One-minute epochs of unipolar electrograms recorded via a 64-pole basket catheter in both atria were re-analyzed with EGF-Mapping. SST was calculated as the percentage of time in which a source was detected. ResultsAF sources identified with EGF-Mapping show a wide range of SV during 1 min covering between 0.12% and 38% of the recorded basket-catheter surface. The 12 atria where the sources showed highest temporal stability (TS; between 34% and 97% of 1 min recorded) and those 12 with the lowest TS (between 11 and 20%) differed significantly in their velocities (17.8 el/s vs 12.2 el/s; p < 0.01). In 11 atria ablation caused an average decrease of TS by 47% and of velocity by 27% while SV more than doubled. ConclusionLess stable AF-sources with high spatial variability showed reduced excitation propagation velocity while stable AF sources displayed a high average velocity in their vicinity. Importantly, catheter ablation reduced stability of sources and velocity suggesting a role of these parameters in guidance of ablation. Condensed abstractElectrographic Flow (EGF)-Mapping is a novel method to identify Atrial Fibrillation (AF) drivers based on modeling of an electrical potential surface and subsequent flow analysis. Sources of excitation during AF can be characterized and monitored. The aim of this study was to evaluate the correlation between velocity of EGF around a respective AF source and its spatial variability and stability. Less stable AF sources with high spatial variability showed reduced excitation propagation velocity while very stable AF sources displayed a high average velocity in their vicinity. Catheter ablation reduced stability of sources and velocity.

Clinical and regulatory considerations for novel electrophysiology mapping systems: Lessons from FIRM.

Atrial fibrillation (AF) presents a growing clinical and public health burden for which better rhythm control therapies are needed. Focal impulse and rotor mapping (FIRM), currently marketed as a part of the Topera Rotor Mapping system (Abbott Laboratories, Austin, TX, USA), represents a potentially transformational approach to guide the invasive treatment of AF. However, many years after its initial marketing clearance, the clinical utility of this technology remains uncertain. In this article, we review the scientific rationale for this novel approach to AF ablation, evaluate the current clinical evidence for FIRM-guided ablation, and characterize its premarket regulatory assessment. Lessons for clinicians considering adoption of newly marketed mapping systems are presented.

The Fibrotic Substrate in Persistent Atrial Fibrillation Patients: Comparison Between Predictions From Computational Modeling and Measurements From Focal Impulse and Rotor Mapping.

Focal impulse and rotor mapping (FIRM) involves intracardiac detection and catheter ablation of re-entrant drivers (RDs), some of which may contribute to arrhythmia perpetuation in persistent atrial fibrillation (PsAF). Patient-specific computational models derived from late gadolinium-enhanced magnetic resonance imaging (LGE-MRI) has the potential to non-invasively identify all areas of the fibrotic substrate where RDs could potentially be sustained, including locations where RDs may not manifest during mapped AF episodes. The objective of this study was to carry out multi-modal assessment of the arrhythmogenic propensity of the fibrotic substrate in PsAF patients by comparing locations of RD-harboring regions found in simulations and detected by FIRM (RDsim and RDFIRM) and analyze implications for ablation strategies predicated on targeting RDs. For 11 PsAF patients who underwent pre-procedure LGE-MRI and FIRM-guided ablation, we retrospectively simulated AF in individualized atrial models, with geometry and fibrosis distribution reconstructed from pre-ablation LGE-MRI scans, and identified RDsim sites. Regions harboring RDsim and RDFIRM were compared. RDsim were found in 38 atrial regions (median [inter-quartile range (IQR)] = 4 [3; 4] per model). RDFIRM were identified and subsequently ablated in 24 atrial regions (2 [1; 3] per patient), which was significantly fewer than the number of RDsim-harboring regions in corresponding models (p < 0.05). Computational modeling predicted RDsim in 20 of 24 (83%) atrial regions identified as RDFIRM-harboring during clinical mapping. In a large number of cases, we uncovered RDsim-harboring regions in which RDFIRM were never observed (18/22 regions that differed between the two modalities; 82%); we termed such cases “latent” RDsim sites. During follow-up (230 [180; 326] days), AF recurrence occurred in 7/11 (64%) individuals. Interestingly, latent RDsim sites were observed in all seven computational models corresponding to patients who experienced recurrent AF (2 [2; 2] per patient); in contrast, latent RDsim sites were only discovered in two of four patients who were free from AF during follow-up (0.5 [0; 1.5] per patient; p < 0.05 vs. patients with AF recurrence). We conclude that substrate-based ablation based on computational modeling could improve outcomes.

Identification of active atrial fibrillation sources and their discrimination from passive rotors using electrographical flow mapping.

The optimal ablation approach for the treatment of persistent atrial fibrillation (AF) is still under debate; however, the identification and elimination of AF sources is thought to play a key role. Currently available technologies for the identification of AF sources are not able to differentiate between active rotors or focal impulse (FI) and passive circular turbulences as generated by the interaction of a wave front with a functional obstacle such as fibrotic tissue. This study introduces electrographic flow (EGF) mapping as a novel technology for the identification and characterization of AF sources in humans. Twenty-five patients with AF (persistent: n = 24, long-standing persistent: n = 1; mean age 70.0 ± 8.3 years, male: n = 17) were included in this prospective study. Focal impulse and Rotor-Mapping (FIRM) was performed in addition to pulmonary vein isolation using radiofrequency in conjunction with a 3D-mapping-system. One-minute epochs were exported from the EP-recording-system and re-analyzed using EGF mapping after the procedure. 44 potential AF sources (43 rotors and one FI) were identified with FIRM and 39 of these rotors were targeted for ablation. EGF mapping verified 40 of these patterns and identified 24/40 (60%) as active sources while 16/40 (40%) were classified as passive circular turbulences. Four rotors were not identified by EGF mapping. EGF is the first method to identify active AF sources during AF ablation procedures in humans and discriminate them from passive rotational phenomena, which occur if the excitation wavefront passes conduction bariers. EGF mapping may allow improved guidance of AF ablation procedures.

Ablation of Focal Impulses and Rotational Sources: What Can Be Learned from Differing Procedural Outcomes?

There is considerable interest in identifying potential drivers for human atrial fibrillation (AF), in order to improve therapy. Ablation via pulmonary vein isolation (PVI) is broadly used, yet is insufficient in many patients yet its outcomes are unimproved by adding extensive ablation of lines or complex electrogram sites, particularly in patients with persistent AF. Rotational and focal sources for AF represent novel mechanistic and therapeutic targets, often remote from the PVs and proven to drive AF in many studies. This chapter discusses this issue. AF sources can now routinely be identified clinically by many methods, yet discrepant results have been reported. AF drivers identified by Focal Impulse and Rotor Mapping (FIRM), the most widely applied method, are also seen in simultaneous optical maps of human atria and have now been detected by other mapping methods applied to the exact same signals. In proof-of-concept studies, ablation of drivers can terminate persistent AF and, in over a thousand patients reported thus far, yield favorable long-term outcomes versus PVI alone. Nevertheless, some centers show disappointing results. This review focuses on discrepant results, which may reflect challenging patients, operator unfamiliarity with basket catheter use, or the technical ablation of drivers, amongst other factors. We discuss challenges, potential solutions, and future directions for map-guided AF driver ablation including basket-data collection, interpreting AF maps, ablation guidance, and extent. Mapping and ablation of AF drivers is a rapidly growing field which, with continued scientific discovery and procedural advances, offers a strong mechanistic foundation to improve patient-tailored ablation for complex arrhythmias.

A Focal Impulse and Rotor Mapping (FIRM) Ablation Approach for Recurrent Persistent Atrial Fibrillation

A Focal Impulse and Rotor Mapping (FIRM) Ablation Approach for Recurrent Persistent Atrial Fibrillation

Treatment of Recurrent Nonparoxysmal Atrial Fibrillation Using Focal Impulse and Rotor Mapping (FIRM)-Guided Rotor Ablation: Early Recurrence and Long-Term Outcomes.

A patient-tailored ablation approach focused on the elimination of both pulmonary vein triggers as well as substrate drivers may result in favorable outcomes in recurrent persistent AF patients. We evaluated the long-term outcomes of rotor ablation combined with conventional pulmonary vein isolation (PVI) in patients with recurrent nonparoxysmal AF. Fifty-eight consecutive patients underwent FIRM-guided rotor ablation followed by conventional PVI for the treatment of recurrent nonparoxysmal AF. A software algorithm was used to display rotational activity at rotor sites by creating propagation maps from unipolar electrograms recorded using a 64-electrode basket catheter. These rotor sites were targeted for ablation, followed by conventional PVI. All patients had nonparoxysmal AF (83% longstanding persistent) and a previously failed conventional ablation procedure. Stable rotors were identified in all patients (mean of 3.0 ± 1.6 per patient), with 55.2% having right atrial rotors and 96.6% left atrial rotors, respectively. Complications occurred in 5.2% of patients, none related to the FIRM procedure. The median follow-up was 12 months. At 6 and 12 months of follow-up, 73.2% and 76.9% of patients remained free from AF/AT, respectively. Excluding 2 patients who underwent a successful redo ablation procedure/electrical cardioversion, at 12 months of follow-up, 69.2% were free from any AF/AT and 73.1% were free from AF after a single FIRM-guided ablation procedure. A high degree of success was observed in this cohort of primarily longstanding persistent AF patients treated for recurrent AF with FIRM-guided rotor ablation. Prospective randomized controlled trials are needed.

138-05: Evidence for a correlation between rotor activity and atrial fibrosis in patients with atrial fibrillation

Purpose: Despite significant progress in catheter techniques suboptimal ablation outcomes are observed for patients with atrial fibrillation (AF). This effect is potentially related to the standard approaches of most ablation techniques which mainly focus on anatomic rather than patient specific functional targets. Recently, two new ablation concepts have been introduced which are aimed on patient specific targets. First, stable electrical rotors and focal sources have been demonstrated to sustain AF. Therefore, the ablation of rotors has been associated in first studies with an improved clinical outcome in comparison to conventional ablation. Second, there is increasing evidence that atrial fibrosis can not only be considered as predictor for the ablation outcome but also as a primary disease driving AF. Along this line, atrial fibrosis could be a target for tailored ablation. The aim of this study is to investigate the correlation between rotor acticity and left atrial fibrosis in patients with AF. Methods: Patients that underwent redo procedure for AF using Focal Impulse and Rotor Mapping (FIRM) were analyzed for number and location of rotors and for degree and location of left atrial fibrosis. Left atrial (LA) voltage maps were generated during sinus rhythm after rotor and pulmonary vein isolation. Low voltage was defined as a signal amplitude < 0,5 mV. Fibrosis was categorized as stage 1 (<10% of the LA wall), 2 (≥10%- < 20%), 3 (≥20%- < 30%), and 4 (≥30%). Results: 42 patients (mean age 62 ± 9 years, 31 male) with recurrent AF (37 persistent, 5 paroxysmal) were included. There were 21 patients in stage 1 (50%), 7 in stage 2 (17%), 9 in stage 3 (21%) and 5 in stage 4 (12%). In patients with stage 1 we observed a mean number of RA rotors of 0.6 ± 0,7 (0–2) and LA rotors of 1.4 ± 0.9 (0–4), with stage 2 0.3 ± 0.5 (0–1) and 1.9 ± 0.7 (1–3), with stage 3 1.1 ± 1.1 (0–3) and 2.3 ± 1.0 (1–4) and with stage 4 0.6 ± 0.5 (0–1) and 3.0 ± 1.2 (2–5), respectively. We found significant more LA rotors (2.3 ± 1.0; 1–5) in patients with verification of LA fibrosis (stage 2–4) than in patients without relevant LA fibrosis (p = 0.04). A total of 29 out of 80 LA rotors (36%) in all patients were located in a spacial vicinity of a low voltage area. As expected, the number was higher in patients with LA fibrosis (59%), also depending on the degree of fibrosis (stage 2: 38%, stage 3: 57%, stage 4: 80%). Conclusions: Rotor activity has been identified in patients with and without LA fibrosis. However, more LA rotors have been observed in patients with LA fibrosis. Depending on the degree of fibrosis an increasing number of rotors have been found in spacial vicinity of LA fibrosis areas.

138-06: Evidence for a late effect of rotor ablation in patients undergoing redo procedure for atrial fibrillation

Purpose: Stable electrical rotors and focal sources have been demonstrated to sustain atrial fibrillation (AF). Rotor activity can be demonstrated using a special computational mapping procedure. The aim of this study is to analyze the characteristics of the course of heart rhythm (AF recurrence and restoration of sinus rhythm) after rotor ablation. Methods: Patients who underwent redo procedure for AF (Focal Impulse and Rotor Mapping (FIRM) guided ablation and additional re-pulmonary vein isolation) were analyzed with respect to the time of AF recurrence and the characteristics of restoration of sinus rhythm (SR). Follow-up visits including 96h Holter and/or device interrogation were performed 3, 6 and 12 months after ablation procedure. Results: 44 patients (mean age 63 ± 9 years, 27 male) with recurrent AF (8 paroxysmal, 36 persistent) were included, all of them had undergone 6 month follow-up visit and 26/44 (59%) 12 month follow-up visit so far. We found 52% (23/44) of the patients in stable SR at 3 month, 66% (29/44) at 6 month and 88% (23/26) at 12 month follow-up, respectively. 50% (22/44) of the patients remained in stable SR during the complete follow-up period without any recurrence of AF or atrial tachycardia (AT). 32% (14/44) of the patients were in stable SR at the currently last follow-up even though a recurrence of AF had been observed before at 3 or 6 month follow-up (8 patients with cardioversion to SR between 3 and 6 months after procedure, 6 patients between 6 and 12 months, respectively). The cases of this patient group can be classified as follows: We have observed a spontaneous cardioversion to SR without any intervention for 6/14 (43%) patients (despite persistent AF before). 3/14 (21%) received an additional antiarrhythmic drug therapy (despite ineffectiveness before ablation), 3/14 (21%) underwent an electrical cardioversion and 2/14 (14%) a reablation procedure, respectively. Conclusion: In this single left study we have detected a remarkable increase of success rate over time for patients in stable SR after FIRM-guided ablation from 52% at 3 month follow-up to 88% at 12 month follow-up. We suppose, that there is an additional late effect of rotor ablation, maybe due to a kind of “reverse remodeling” of atrial substrate. Therefore, final ablation outcome should be assessed at the earliest 9 to 12 months after procedure.

Abstract 18402: Human Atrial Fibrillation Drivers Seen Simultaneously by Focal Impulse and Rotor Mapping and High-resolution Optical Mapping

Background: A mechanism of AF maintenance has been suggested to be a limited number of patient-specific AF drivers seen by optical mapping in animals and now Focal Impulse and Rotor Mapping (FIRM) in patients. The higher resolution optical mapping can only be performed ex vivo and, thus, these two different mapping approaches have never been evaluated simultaneously in human hearts. Methods: Coronary-perfused explanted human atria (n=5, 19-57 y.o.) were optically mapped using voltage sensitive near-infrared di-4-ANBDQBS with 2-4 high resolution CMOS cameras (100x100 pixels with 330-1000μM resolution) simultaneously with a 64-electrode basket catheter or a 64-electrode custom flat catheter from either the endocardium or epicardium. AF (&gt;10 min, 6.8±2.1Hz) was induced by perfusion of adenosine (10-100μM) and/or isoproterenol (10-100nM). AF drivers were defined as localized stable reentrant activity in areas of highest dominant frequency for optical mapping, while unipolar signals from the catheters were analyzed using experienced FIRM user interpretation and RAP, a signal analysis tool that highlights driver regions on commercially available systems. Results: Optical mapping identified reentrant AF drivers in 7/8 episodes of AF in both the left and right atria. Interestingly, one episode of AF was driven by two competing reentrant drivers. Six AF drivers seen by optical mapping were also seen with the same location and rotation by FIRM, while FIRM identified an AF driver in an 8th episode from an endocardial basket that was unseen by optical mapping from the epicardium. In one episode, the intramural AF driver was only defined by dual sided optical mapping and unseen by endocardial FIRM. Conclusions: Our study demonstrates that most localized reentrant AF drivers in ex vivo human hearts have similar spatiotemporal characteristics whether identified by high resolution optical mapping or FIRM and may represent the clinical phenomena seen in AF patients.

Theoretical considerations for mapping activation in human cardiac fibrillation

Defining mechanisms for cardiac fibrillation is challenging because, in contrast to other arrhythmias, fibrillation exhibits complex non-repeatability in spatiotemporal activation but paradoxically exhibits conserved spatial gradients in rate, dominant frequency, and electrical propagation. Unlike animal models, in which fibrillation can be mapped at high spatial and temporal resolution using optical dyes or arrays of contact electrodes, mapping of cardiac fibrillation in patients is constrained practically to lower resolutions or smaller fields-of-view. In many animal models, atrial fibrillation is maintained by localized electrical rotors and focal sources. However, until recently, few studies had revealed localized sources in human fibrillation, so that the impact of mapping constraints on the ability to identify rotors or focal sources in humans was not described. Here, we determine the minimum spatial and temporal resolutions theoretically required to detect rigidly rotating spiral waves and focal sources, then extend these requirements for spiral waves in computer simulations. Finally, we apply our results to clinical data acquired during human atrial fibrillation using a novel technique termed focal impulse and rotor mapping (FIRM). Our results provide theoretical justification and clinical demonstration that FIRM meets the spatio-temporal resolution requirements to reliably identify rotors and focal sources for human atrial fibrillation.