Advanced Mapping Systems To Guide Atrial Fibrillation Ablation: Electrical Information That Matters

State of the Art and Future Opportunities in MRI-Guided Robot-Assisted Surgery and Interventions

Magnetic resonance imaging (MRI) can provide high-quality 3-D visualization of target anatomy, surrounding tissue, and instrumentation, but there are significant challenges in harnessing it for effectively guiding interventional procedures. Challenges include the strong static magnetic field, rapidly switching magnetic field gradients, high-power radio frequency pulses, sensitivity to electrical noise, and constrained space to operate within the bore of the scanner. MRI has a number of advantages over other medical imaging modalities, including no ionizing radiation, excellent soft-tissue contrast that allows for visualization of tumors and other features that are not readily visible by other modalities, true 3-D imaging capabilities, including the ability to image arbitrary scan plane geometry or perform volumetric imaging, and capability for multimodality sensing, including diffusion, dynamic contrast, blood flow, blood oxygenation, temperature, and tracking of biomarkers. The use of robotic assistants within the MRI bore, alongside the patient during imaging, enables intraoperative MR imaging (iMRI) to guide a surgical intervention in a closed-loop fashion that can include tracking of tissue deformation and target motion, localization of instrumentation, and monitoring of therapy delivery. With the ever-expanding clinical use of MRI, MRI-compatible robotic systems have been heralded as a new approach to assist interventional procedures to allow physicians to treat patients more accurately and effectively. Deploying robotic systems inside the bore synergizes the visual capability of MRI and the manipulation capability of robotic assistance, resulting in a closed-loop surgery architecture. This article details the challenges and history of robotic systems intended to operate in an MRI environment and outlines promising clinical applications and associated state-of-the-art MRI-compatible robotic systems and technology for making this possible.

Ablation of Atrial Fibrillation in Patients With Hypertrophic Cardiomyopathy: Treatment Strategy, Characteristics of Consecutive Atrial Tachycardia and Long-Term Outcome

Background

Atrial fibrillation (AF) is common in patients with hypertrophic cardiomyopathy (HCM) and is associated with a deterioration of clinical status. Ablation of symptomatic AF is an established therapy, but in HCM, the characteristics of recurrent atrial arrhythmias and the long‐term outcome are uncertain.

Methods and Results

Sixty‐five patients with HCM (aged 64.5±9.9 years, 42 [64.6%] men) underwent AF ablation. The ablation strategy included pulmonary vein isolation in all patients and ablation of complex fractionated atrial electrograms or subsequent atrial tachycardias (AT) if appropriate. Paroxysmal, persistent AF, and a primary AT was present in 13 (20.0%), 51 (78.5%), and 1 (1.5%) patients, respectively. Twenty‐five (38.4%) patients developed AT with a total number of 54 ATs. Stable AT was observed in 15 (23.1%) and unstable AT in 10 (15.3%) patients. The mechanism was characterized as a macroreentry in 37 (68.5%), as a localized reentry in 12 (22.2%), a focal mechanism in 1 (1.9%), and not classified in 4 (7.4%) ATs. After 1.9±1.2 ablation procedures and a follow‐up of 48.1±32.5 months, freedom of AF/AT recurrences was demonstrated in 60.0% of patients. No recurrences occurred in 84.6% and 52.9% of patients with paroxysmal and persistent AF, respectively (P<0.01). Antiarrhythmic drug therapy was maintained in 24 (36.9%) patients.

Conclusions

AF ablation in patients with HCM is effective for long‐term rhythm control, and especially patients with paroxysmal AF undergoing pulmonary vein isolation have a good clinical outcome. ATs after AF ablation are frequently observed in HCM. Freedom of atrial arrhythmia is achieved by persistent AF ablation in a reasonable number of patients even though the use of antiarrhythmic drug therapy remains high.

Catheter Ablation for Treatment of Atrial Fibrillation and Supraventricular Arrhythmias Without Fluoroscopy Use: Acute Efficacy and Safety

Fundamento

O uso da radiação ionizante em procedimentos médicos está associado a riscos significativos à saúde dos pacientes e da equipe de saúde.

Objetivos

Avaliar a segurança e a eficácia aguda da ablação por cateter para tratamento da fibrilação atrial (FA) e arritmias supraventriculares (SVTs), utilizando uma abordagem exclusivamente não fluoroscópica, guiada por eco intracardíaco (ICE) e mapeamento 3D.

Métodos

95 pts (idade média 60 ± 18 anos, 61% do sexo masculino) programados para ablação de FA (69 pts, 45 FA paroxística e 24 FA persistente) ou SVTs (26 pts – 14 reentrada nodal, 6 Wolf-Parkinson-White [WPW], 5 flutter atrial direito [AD], 1 taquicardia atrial). Nove pacientes (9,5%) tinham marcapasso definitivo ou dispositivos de ressincronização com desfibrilador. Dois sistemas de mapeamento eletroanatômico foram utilizados – CARTO (65%) e NAVx (35%), bem como cateteres de ICE disponíveis – Acunav e ViewFlex.

Resultados

O isolamento das veias pulmonares (VPs), bem como todos os outros alvos que precisavam de ablação em ambos os átrios, foram alcançados e adequadamente visualizados. Não foram observados derrames pericárdicos, complicações trombóticas ou outras intercorrências nesta série. Punções transseptais difíceis (19 pacientes – 20%) foram realizadas sem fluoroscopia em todos os casos. Não foi utilizada fluoroscopia de backup, e nenhum vestuário de chumbo foi necessário. Avaliações detalhadas dos marcapassos após o procedimento não mostraram nenhum dano aos eletrodos, deslocamentos ou mudanças de limiar.

Conclusões

Uma estratégia de ablação por cateter sem uso de radiação para FA e outras arritmias atriais é segura e eficaz quando guiada pela utilização adequada do ICE e do mapeamento 3D. Diversos sítios em ambos os átrios podem ser alcançados e adequadamente ablacionados sem a necessidade de fluoroscopia de backup. Não foram observadas complicações. (Arq Bras Cardiol. 2020; 114(6):1015-1026)

Role of pre-procedural CT imaging on catheter ablation in patients with atrial fibrillation: procedural outcomes and radiological exposure

BACKGROUND

Cardiac computed tomography (CT) is commonly used to study left atrial (LA) and pulmonary veins (PVs) anatomy before atrial fibrillation (AF) ablation. The aim of the study was to determine the impact of pre-procedural cardiac CT with 3D reconstruction on procedural outcomes and radiological exposure in patients who underwent radiofrequency catheter ablation (RFA) of AF.

METHODS

In this registry, 493 consecutive patients (age 62 ± 8 years, 70% male) with paroxysmal (316) or persistent (177) AF who underwent first procedure of RFA were included. A pre-procedural CT scan was obtained in 324 patients (CT group). Antral pulmonary vein isolation was performed in all patients using an open-irrigation-tip catheter with a 3D electroanatomical navigation system. Procedural outcome, including radiological exposure, and clinical outcomes were compared among patients who underwent RFA with (CT group) and without (no CT group) pre-procedural cardiac CT.

RESULTS

Acute PV isolation was obtained in all patients, with a comparable overall complication rate between CT and no CT group (4.3% vs 3%, p = 0.7). No differences were observed about mean duration of the procedure (231 ± 60 vs 233 ± 58 min, p = 0.7) and fluoroscopy time (13 ± 10 vs 13 ± 8 min, p = 0.6) among groups. Cumulative radiation dose resulted significantly higher in the CT group compared with no CT group (8.9 ± 24 vs 4.8 ± 15 mSv, P = 0.02). At 1 year, freedom from AF/atrial tachycardia were comparable among groups (CT group, 227/324 (70%), vs no CT group,119/169 (70%), p = ns).

CONCLUSIONS

Pre-procedural CT does not improve safety and efficacy of AF ablation, increasing significantly the cumulative radiological exposure.

High-resolution Mapping in Patients with Persistent AF

Ablation of AF through electrical isolation of the pulmonary veins is a well-established technique and a cornerstone in the ablation of AF, although there are a variety of techniques and ablation strategies now available. However, high numbers of patients are returning to hospital after ablation procedures such as pulmonary vein isolation (PVI). Scar tissue (as identified by contact voltage mapping) is found to be present in many of these patients, especially those with persistent AF and even those with paroxysmal AF. This scarring is associated with poor outcomes after PVI. Cardiac mapping is necessary to locate triggers and substrate so that an ablation strategy can be optimised. Multipolar mapping catheters offer more information regarding the status of the tissue than standard ablation catheters. A patient-tailored catheter ablation approach, targeting the patient-specific low voltage/fibrotic substrate can lead to improved outcomes.

Feasibility of a novel mapping system combined with remote magnetic navigation for catheter ablation of premature ventricular contractions

BACKGROUND

Remote magnetic navigation (RMN) is often used in combination with a 3-dimensional mapping system to perform catheter ablations. This study aim to investigate the feasibility and effectiveness of a novel 3D-mapping system, EnSite Precision, combined with RMN for catheter ablation of premature ventricular contractions (PVCs), and compared it to the procedures performed by CARTO3 with RMN.

METHODS

Forty-three consecutive PVC patients were either ablated with the guidance of EnSite Precision (n = 22) or CARTO (n = 21) navigated by RMN. Procedure-related details, acute and long-term success were assessed.

RESULTS

Patient characteristics between both the groups were similar (age: 47.1 ± 19.8 vs 47.1 ± 12.7, female: 63.6% vs 57.1%). No significant difference was found in the procedure time (99.5 ± 30.4 vs 92.9 ± 24.8 min, P = 0.436), mapping time (18.6 ± 12.8 vs 15.5 ± 10.2 min, P = 0.390), radiofrequency ablation time (333.4 ± 267.0 vs 469.3 ± 343.1 s, P = 0.154), fluoroscopy time (4.0 ± 1.9 vs 3.8 ± 2.0 min, P = 0.635), and X-ray dose (1.8 ± 1.4 vs 2.0 ± 1.2 Gycm2, P = 0.649) between the two groups. No significant procedural complication occurred in either group. In addition, there was no significant differences regarding the acute success rate (90.9% vs 90.5%, P = 0.961) and long-term success rate (86.4% vs 81.0%, P = 0.631) after 16.2 ± 6.2 months of follow-up between the two groups.

CONCLUSIONS

RMN combined with EnSite Precision mapping system is effective and safe for catheter ablation of PVCs.

Stationary Atrial Fibrillation Properties in the Goat Do Not Entail Stable or Recurrent Conduction Patterns

Introduction: Electro-anatomical mapping of the atria is used to identify the substrate of atrial fibrillation (AF). Targeting this substrate by ablation in addition to pulmonary vein ablation did not consistently improve outcome in clinical trials. Generally, the assessment of the substrate is based on short recordings (≤10 s, often even shorter). Thus, targeting the AF substrate assumes spatiotemporal stationarity but little is known about the variability of electrophysiological properties of AF over time.

Methods: Atrial fibrillation (AF) was maintained for 3–4 weeks after pericardial electrode implantation in 12 goats. Within a single AF episode 10 consecutive minutes were mapped on the left atrial free wall using a 249-electrode array (2.25 mm inter-electrode spacing). AF cycle length, fractionation index (FI), lateral dissociation, conduction velocity, breakthroughs, and preferentiality of conduction (Pref) were assessed per electrode and AF property maps were constructed. The Pearson correlation coefficient (PCC) between the 10 AF-property maps was calculated to quantify the degree spatiotemporal stationarity of AF properties. Furthermore, the number of waves and presence of re-entrant circuits were analyzed in the first 60-s file. Comparing conduction patterns over time identified recurrent patterns of AF with the use of recurrence plots.

Results: The averages of AF property maps were highly stable throughout the ten 60-s-recordings. Spatiotemporal stationarity was high for all 6 property maps, PCC ranged from 0.66 ± 0.11 for Pref to 0.98 ± 0.01 for FI. High stationarity was lost when AF was interrupted for about 1 h. However, the time delay between the recorded files within one episode did not affect PCC. Yet, multiple waves (7.7 ± 2.3) were present simultaneously within the recording area and during 9.2 ± 11% of the analyzed period a re-entrant circuit was observed. Recurrent patterns occurred rarely and were observed in only 3 out of 12 goats.

Conclusions: During non-self-terminating AF in the goat, AF properties were stationary. Since this could not be attributed to stable recurrent conduction patterns during AF, it is suggested that AF properties are determined by anatomical and structural properties of the atria even when the conduction patterns are very variable.

Clinical scores for outcomes of rhythm control or arrhythmia progression in patients with atrial fibrillation: a systematic review

Patients with atrial fibrillation (AF) are commonly managed with rhythm control strategy, but the natural history of this common arrhythmia leads itself to progression from paroxysmal to persistent or permanent AF, and recurrences are evident despite rhythm control treatments using cardioversion or catheter ablation. Numerous clinical factors have been associated with outcomes of rhythm control or arrhythmia progression in patients with AF. The more common factors have been used to formulate risk stratification scores, to help predict the outcomes of rhythm control treatments or AF progression. This review article provides an overview on the published clinical risk scores related to outcomes of rhythm control strategy or AF progression.