Cardiac magnetic resonance-aided scar dechanneling: Influence on acute and long-term outcomes

Variations in threshold values for border zone and dense scar produce significant changes in scar parameters obtained by ADAS-3D

BACKGROUND

ADAS-3D software elaborates cardiac magnetic resonance (CMR) images to obtain a quantitative evaluation of dense scar and border zone (BZ), including BZ channels, which can be useful for ventricular tachycardia ablation and risk stratification. However, most prior reports with ADAS-3D used flexible thresholds (60% ± 5% and 40% ± 5% of maximum pixel signal intensity) to define dense scar and BZ. The impact of such variations of the threshold values on the measurements obtained with ADAS-3D is unknown.

OBJECTIVE

This study aimed to quantify the degree of change in ADAS-3D measurements when different thresholds for dense scar and BZ are employed.

METHODS

A single-center retrospective observational cohort study including 87 consecutive patients with previous myocardial infarction who underwent CMR was conducted. ADAS-3D software semiautomatically processed CMR sequences. We compared the scar measurements obtained with the 9 possible combinations of thresholds (55%/60%/65% and 35%/40%/45% of maximum pixel signal intensity).

RESULTS

The overall comparison between thresholds showed highly significant differences (P < .001) in all scar parameters. Not a single patient maintained the same number of BZ channels with all the thresholds settings. A percentage difference of up to 200% in BZ channel numbers and channel mass was observed in all 36 comparisons. An absolute difference of up to 10 channels was also recorded. Of note, the highest median channel mass (obtained with the thresholds 35-65) was 59-fold higher compared with the lowest one (obtained with the 45-55 cutoffs).

CONCLUSION

Variations in threshold values result in statistically significant and high-magnitude changes in the quantification of scar parameters by ADAS-3D.

Substrate Mapping for Ventricular Tachycardia Ablation Through High-Density Whole-Chamber Double Extra Stimuli: The S3 Protocol

BACKGROUND

A partial delineation of targets for ablation of ventricular tachycardia (VT) during a stable rhythm is likely responsible for a suboptimal success rate. The abnormal low-voltage near-field functional components may be hidden within the high-amplitude far-field signal.

OBJECTIVES

The aim of this study was to evaluate the benefit and feasibility of functional substrate mapping using a full-ventricle S3 protocol and to assess its colocalization with arrhythmogenic conducting channels (CCs) on late gadolinium enhancement cardiac magnetic resonance.

METHODS

An S3 mapping protocol with a drive train of S1 followed by S2 (effective refractory period + 30 ms) and S3 (effective refractory period + 50 ms) from the right ventricular apex was performed in 40 consecutive patients undergoing scar-related VT ablation. Deceleration zones (DZs) and areas of late potentials (LPs) were identified for all maps. A preprocedural noninvasive substrate assessment was done using late gadolinium enhancement cardiac magnetic resonance and postprocessing with automated CC identification.

RESULTS

The S3 protocol was completed in 34 of the 40 procedures (85.0%). The S3 protocol enhanced the identification of VT isthmus on the basis of DZ (89% vs 62%; P < 0.01) and LP (93% vs 78%; P = 0.04) assessment. The percentage of CCs unmasked by DZs and LPs using S3 maps was significantly higher than the ones using S2 and S1 maps (78%, 65%, and 48% [P < 0.001] and 88%, 81%, and 68% [P < 0.01], respectively). The functional substrate identified during S3 activation mapping was significantly more extensive than the one identified using S2 and S1, including a greater number of DZs (2.94, 2.47, and 1.82, respectively; P < 0.001) and a wider area of LPs (44.1, 38.2, and 29.4 cm2, respectively; P < 0.001). After VT ablation, 77.9% of patients have been VT free during a median follow-up period of 13.6 months.

CONCLUSIONS

The S3 protocol was feasible in 85% of patients, allows a better identification of targets for ablation, and might improve VT ablation results.

Tachyarrhythmias in congenital heart disease

The prevalence of congenital heart disease (CHD) in adult patients has risen with advances in diagnostic and surgical techniques. Surgical modifications and hemodynamic changes increase the susceptibility to arrhythmias, impacting morbidity and mortality rates, with arrhythmias being the leading cause of hospitalizations and sudden deaths. Patients with CHD commonly experience both supraventricular and ventricular arrhythmias, with each CHD type associated with different arrhythmia patterns. Macroreentrant atrial tachycardias, particularly cavotricuspid isthmus-dependent flutter, are frequently reported. Ventricular arrhythmias, including monomorphic ventricular tachycardia, are prevalent, especially in patients with surgical scars. Pharmacological therapy involves antiarrhythmic and anticoagulant drugs, though data are limited with potential adverse effects. Catheter ablation is preferred, demanding meticulous procedural planning due to anatomical complexity and vascular access challenges. Combining imaging techniques with electroanatomic navigation enhances outcomes. However, risk stratification for sudden death remains challenging due to anatomical variability. This article practically reviews the most common tachyarrhythmias, treatment options, and clinical management strategies for these patients.

Pre- and post-procedural cardiac imaging (computed tomography and magnetic resonance imaging) in electrophysiology: a clinical consensus statement of the European Heart Rhythm Association and European Association of Cardiovascular Imaging of the European Society of Cardiology

Imaging using cardiac computed tomography (CT) or magnetic resonance (MR) imaging has become an important option for anatomic and substrate delineation in complex atrial fibrillation (AF) and ventricular tachycardia (VT) ablation procedures. Computed tomography more common than MR has been used to detect procedure-associated complications such as oesophageal, cerebral, and vascular injury. This clinical consensus statement summarizes the current knowledge of CT and MR to facilitate electrophysiological procedures, the current value of real-time integration of imaging-derived anatomy, and substrate information during the procedure and the current role of CT and MR in diagnosing relevant procedure-related complications. Practical advice on potential advantages of one imaging modality over the other is discussed for patients with implanted cardiac rhythm devices as well as for planning, intraprocedural integration, and post-interventional management in AF and VT ablation patients. Establishing a team of electrophysiologists and cardiac imaging specialists working on specific details of imaging for complex ablation procedures is key. Cardiac magnetic resonance (CMR) can safely be performed in most patients with implanted active cardiac devices. Standard procedures for pre- and post-scanning management of the device and potential CMR-associated device malfunctions need to be in place. In VT patients, imaging-specifically MR-may help to determine scar location and mural distribution in patients with ischaemic and non-ischaemic cardiomyopathy beyond evaluating the underlying structural heart disease. Future directions in imaging may include the ability to register multiple imaging modalities and novel high-resolution modalities, but also refinements of imaging-guided ablation strategies are expected.

Personalized voltage maps guided by cardiac magnetic resonance in the era of high-density mapping

BACKGROUND

Voltage mapping could identify the conducting channels potentially responsible for ventricular tachycardia (VT). Standard thresholds (0.5-1.5 mV) were established using bipolar catheters. No thresholds have been analyzed with high-density mapping catheters. In addition, channels identified by cardiac magnetic resonance (CMR) has been proven to be related with VT.

OBJECTIVE

The purpose of this study was to analyze the diagnostic yield of a personalized voltage map using CMR to guide the adjustment of voltage thresholds.

METHODS

All consecutive patients with scar-related VT undergoing ablation after CMR (from October 2018 to December 2020) were included. First, personalized CMR-guided voltage thresholds were defined systematically according to the distribution of the scar and channels. Second, to validate these new thresholds, a comparison with standard thresholds (0.5-1.5 mV) was performed. Tissue characteristics of areas identified as deceleration zones (DZs) were recorded for each pair of thresholds. In addition, the relation of VT circuits with voltage channels was analyzed for both maps.

RESULTS

Thirty-two patients were included [mean age 66.6 ± 11.2 years; 25 (78.1%) ischemic cardiomyopathy]. Overall, 52 DZs were observed: 44.2% were identified as border zone tissue with standard cutoffs vs 75.0% using personalized voltage thresholds (P = .003). Of the 31 VT isthmuses detected, only 35.5% correlated with a voltage channel with standard thresholds vs 74.2% using adjusted thresholds (P = .005). Adjusted cutoff bipolar voltages that better matched CMR images were 0.51 ± 0.32 and 1.79 ± 0.71 mV with high interindividual variability (from 0.14-1.68 to 0.7-3.21 mV).

CONCLUSION

Personalized voltage CMR-guided personalized voltage maps enable a better identification of the substrate with a higher correlation with both DZs and VT isthmuses than do conventional voltage maps using fixed thresholds.

Surpoint algorithm for improved guidance of ablation for ventricular tachycardia (SURFIRE-VT): A pilot study

INTRODUCTION

The utility of ablation index (AI) to guide ventricular tachycardia (VT) ablation in patients with structural heart disease is unknown. The aim of this study was to assess procedural characteristics and clinical outcomes achieved using AI-guided strategy (target value 550) or conventional non-AI-guided parameters in patients undergoing scar-related VT ablation.

METHODS

Consecutive patients (n = 103) undergoing initial VT ablation at a single center from 2017 to 2022 were evaluated. Patient groups were 1:1 propensity-matched for baseline characteristics. Single lesion characteristics for all 4707 lesions in the matched cohort (n = 74) were analyzed. The impact of ablation characteristics was assessed by linear regression and clinical outcomes were evaluated by Cox proportional hazard model.

RESULTS

After propensity-matching, baseline characteristics were well-balanced between AI (n = 37) and non-AI (n = 37) groups. Lesion sets were similar (scar homogenization [41% vs. 27%; p = .34], scar dechanneling [19% vs. 8%; p = .18], core isolation [5% vs. 11%; p = .4], linear and elimination late potentials/local abnormal ventricular activities [35% vs. 44%; p = .48], epicardial mapping/ablation [11% vs. 14%; p = .73]). AI-guided strategy had 21% lower procedure duration (-47.27 min, 95% confidence interval [CI] [-81.613, -12.928]; p = .008), 49% lower radiofrequency time per lesion (-13.707 s, 95% CI [-17.86, -9.555]; p < .001), 21% lower volume of fluid administered (1664 cc [1127, 2209] vs. 2126 cc [1750, 2593]; p = .005). Total radiofrequency duration (-339 s [-24%], 95%CI [-776, 62]; p = .09) and steam pops (-155.6%, 95% CI [19.8%, -330.9%]; p = .08) were nonsignificantly lower in the AI group. Acute procedural success (95% vs. 89%; p = .7) and VT recurrence (0.97, 95% CI [0.42-2.2]; p = .93) were similar for both groups. Lesion analysis (n = 4707) demonstrated a plateau in the magnitude of impedance drops once reaching an AI of 550-600.

CONCLUSION

In this pilot study, an AI-guided ablation strategy for scar-related VT resulted in shorter procedure time and average radiofrequency time per lesion with similar acute procedural and intermediate-term clinical outcomes to a non-AI-guided approach utilizing traditional ablation parameters.

Non-invasive detection of slow conduction with cardiac magnetic resonance imaging for ventricular tachycardia ablation

AIMS

Non-invasive myocardial scar characterization with cardiac magnetic resonance (CMR) has been shown to accurately identify conduction channels and can be an important aid for ventricular tachycardia (VT) ablation. A new mapping method based on targeting deceleration zones (DZs) has become one of the most commonly used strategies for VT ablation procedures. The aim of the study was to analyse the capability of CMR to identify DZs and to find predictors of arrhythmogenicity in CMR channels.

METHODS AND RESULTS

Forty-four consecutive patients with structural heart disease and VT undergoing ablation after CMR at a single centre (October 2018 to July 2021) were included (mean age, 64.8 ± 11.6 years; 95.5% male; 70.5% with ischaemic heart disease; a mean ejection fraction of 32.3 ± 7.8%). The characteristics of CMR channels were analysed, and correlations with DZs detected during isochronal late activation mapping in both baseline maps and remaps were determined. Overall, 109 automatically detected CMR channels were analysed (2.48 ± 1.15 per patient; length, 57.91 ± 63.07 mm; conducting channel mass, 2.06 ± 2.67 g; protectedness, 21.44 ± 25.39 mm). Overall, 76.1% of CMR channels were associated with a DZ. A univariate analysis showed that channels associated with DZs were longer [67.81 ± 68.45 vs. 26.31 ± 21.25 mm, odds ratio (OR) 1.03, P = 0.010], with a higher border zone (BZ) mass (2.41 ± 2.91 vs. 0.87 ± 0.86 g, OR 2.46, P = 0.011) and greater protectedness (24.97 ± 27.72 vs. 10.19 ± 9.52 mm, OR 1.08, P = 0.021).

CONCLUSION

Non-invasive detection of targets for VT ablation is possible with CMR. Deceleration zones found during electroanatomical mapping accurately correlate with CMR channels, especially those with increased length, BZ mass, and protectedness.

Post-Ablation cardiac Magnetic resonance to assess Ventricular Tachycardia recurrence (PAM-VT study)

AIMS

Conducting channels (CCs) detected by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) are related to ventricular tachycardia (VT). The aim of this work was to study the ability of post-ablation LGE-CMR to evaluate ablation lesions.

METHODS AND RESULTS

This is a prospective study of consecutive patients referred for a scar-related VT ablation. LGE-CMR was performed 6-12 months prior to ablation and 3-6 months after ablation. Scar characteristics of pre- and post-ablation LGE-CMR were compared. During the study period (March 2019-April 2021), 61 consecutive patients underwent scar-related VT ablation after LGE-CMR. Overall, 12 patients were excluded (4 had poor-quality LGE-CMR, 2 died before post-ablation LGE-CMR, and 6 underwent post-ablation LGE-CMR 12 months after ablation). Finally, 49 patients (age: 65.5 ± 9.8 years, 97.9% male, left ventricular ejection fraction: 34.8 ± 10.4%, 87.7% ischaemic cardiomyopathy) were included. Post-ablation LGE-CMR showed a decrease in the number (3.34 ± 1.03 vs. 1.6 ± 0.2; P < 0.0001) and mass (8.45 ± 1.3 vs. 3.5 ± 0.6 g; P < 0.001) of CCs. Arrhythmogenic CCs disappeared in 74.4% of patients. Dark core was detected in 75.5% of patients, and its presence was not related to CC reduction (52.2 ± 7.4% vs. 40.8 ± 10.6%, P = 0.57). VT recurrence after one year follow-up was 16.3%. The presence of two or more channels in the post-ablation LGE-CMR was a predictor of VT recurrence (31.82% vs. 0%, P = 0.0038) with a sensibility of 100% and specificity of 61% (area under the curve 0.82). In the same line, a reduction of CCs < 55% had sensibility of 100% and specificity of 61% (area under the curve 0.83) to predict VT recurrence.

CONCLUSION

Post-ablation LGE-CMR is feasible, and a reduction in the number of CCs is related with lower risk of VT recurrence. The dark core was not present in all patients. A decrease in VT substrate was also observed in patients without a dark core area in the post-ablation LGE-CMR.

SCMR expert consensus statement for cardiovascular magnetic resonance of patients with a cardiac implantable electronic device

Cardiovascular magnetic resonance (CMR) is a proven imaging modality for informing diagnosis and prognosis, guiding therapeutic decisions, and risk stratifying surgical intervention. Patients with a cardiac implantable electronic device (CIED) would be expected to derive particular benefit from CMR given high prevalence of cardiomyopathy and arrhythmia. While several guidelines have been published over the last 16 years, it is important to recognize that both the CIED and CMR technologies, as well as our knowledge in MR safety, have evolved rapidly during that period. Given increasing utilization of CIED over the past decades, there is an unmet need to establish a consensus statement that integrates latest evidence concerning MR safety and CIED and CMR technologies. While experienced centers currently perform CMR in CIED patients, broad availability of CMR in this population is lacking, partially due to limited availability of resources for programming devices and appropriate monitoring, but also related to knowledge gaps regarding the risk-benefit ratio of CMR in this growing population. To address the knowledge gaps, this SCMR Expert Consensus Statement integrates consensus guidelines, primary data, and opinions from experts across disparate fields towards the shared goal of informing evidenced-based decision-making regarding the risk-benefit ratio of CMR for patients with CIEDs.

The Nottingham Ischaemic Cardiovascular Magnetic Resonance resource (NotIs CMR): a prospective paired clinical and imaging scar database-protocol

INTRODUCTION

Research utilising artificial intelligence (AI) and cardiovascular magnetic resonance (CMR) is rapidly evolving with various objectives, however AI model development, generalisation and performance may be hindered by availability of robust training datasets including contrast enhanced images.

METHODS

NotIs CMR is a large UK, prospective, multicentre, observational cohort study to guide the development of a biventricular AI scar model. Patients with ischaemic heart disease undergoing clinically indicated contrast-enhanced cardiac magnetic resonance imaging will be recruited at Nottingham University Hospitals NHS Trust and Mid-Yorkshire Hospital NHS Trust. Baseline assessment will include cardiac magnetic resonance imaging, demographic data, medical history, electrocardiographic and serum biomarkers. Participants will undergo monitoring for a minimum of 5 years to document any major cardiovascular adverse events. The main objectives include (1) AI training, validation and testing to improve the performance, applicability and adaptability of an AI biventricular scar segmentation model being developed by the authors and (2) develop a curated, disease-specific imaging database to support future research and collaborations and, (3) to explore associations in clinical outcome for future risk prediction modelling studies.

CONCLUSION

NotIs CMR will collect and curate disease-specific, paired imaging and clinical datasets to develop an AI biventricular scar model whilst providing a database to support future research and collaboration in Artificial Intelligence and ischaemic heart disease.

Myocardial scarring and recurrence of ventricular arrhythmia in patients surviving an out-of-hospital cardiac arrest

INTRODUCTION

Prediction of recurrent ventricular arrhythmia (VA) in survivors of an out-of-hospital cardiac arrest (OHCA) is important, but currently difficult. Risk of recurrence may be related to presence of myocardial scarring assessed with late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). Our study aims to characterize myocardial scarring as defined by LGE-CMR in survivors of a VA-OHCA and investigate its potential role in the risk of new VA events.

METHODS

Between 2015 and 2022, a total of 230 VA-OHCA patients without ST-segment elevation myocardial infarction had CMR before implantable cardioverter-defibrillator implantation for secondary prevention at Copenhagen University Hospital, Rigshospitalet, and Hospital Clínic, University of Barcelona, of which n = 170 patients had a conventional (no LGE protocol) CMR and n = 60 patients had LGE-CMR (including LGE protocol). Scar tissue including core, border zone (BZ) and BZ channels were automatically detected by specialized investigational software in patients with LGE-CMR. The primary endpoint was recurrent VA.

RESULTS

After exclusion, n = 52 VA-OHCA patients with LGE-CMR and a mean left ventricular ejection fraction of 49 ± 16% were included, of which 18 (32%) patients reached the primary endpoint of VA. Patients with recurrent VA in exhibited greater scar mass, core mass, BZ mass, and presence of BZ channels compared with patients without recurrent VA. The presence of BZ channels identified patients with recurrent VA with 67% sensitivity and 85% specificity (area under the ROC curve (AUC) 0.76; 95% CI: 0.63-0.89; p < .001) and was the strongest predictor of the primary endpoint.

CONCLUSIONS

The presence of BZ channels was the strongest predictor of recurrent VA in patients with an out of-hospital cardiac arrest and LGE-CMR.

Initial experience on cardiac magnetic resonance-aided VT ablation in South America

BACKGROUND

Cardiac magnetic resonance (CMR) allowed to precisely identify the substrate in scar-related ventricular tachycardia (VT). New software has been developed to define the 3D scar and corridors to help VT ablation by integrating the scar and electroanatomical mapping (EAM). The objective of this study is to evaluate the results of VT ablation aided by the integration of EAM and CMR software processed scar.

METHODS

We selected patients that underwent VT ablation with the integration of EAM and CMR processed using ADAS software and imported to the CARTO system using VTK file format.

RESULTS

From 2019 to 2021, eight patients (mean age 63 ± 4.4, 62.5% male; EF 47 ± 12%) underwent CMR-aided VT ablation. Mean procedural time was 281 ± 77 min. There was of 9 ± 4.4 epicardial and 7.9 ± 4.3 endocardial bulls eye segments with at least 2 g of border zone or core scar. In a median follow-up time of 532 days (Q1: 284, Q3: 688), three patients (37.5%) presented VT recurrence, all three underwent a second procedure, with no VT recurrence on the follow-up. No patient died in the follow-up.

CONCLUSION

CMR aided is ablation is feasible and effective in patients with scar related VT.

Real-time cardiovascular magnetic resonance-guided radiofrequency ablation: A comprehensive review

Cardiac magnetic resonance (CMR) imaging could enable major advantages when guiding in real-time cardiac electrophysiology procedures offering high-resolution anatomy, arrhythmia substrate, and ablation lesion visualization in the absence of ionizing radiation. Over the last decade, technologies and platforms for performing electrophysiology procedures in a CMR environment have been developed. However, performing procedures outside the conventional fluoroscopic laboratory posed technical, practical and safety concerns. The development of magnetic resonance imaging compatible ablation systems, the recording of high-quality electrograms despite significant electromagnetic interference and reliable methods for catheter visualization and lesion assessment are the main limiting factors. The first human reports, in order to establish a procedural workflow, have rationally focused on the relatively simple typical atrial flutter ablation and have shown that CMR-guided cavotricuspid isthmus ablation represents a valid alternative to conventional ablation. Potential expansion to other more complex arrhythmias, especially ventricular tachycardia and atrial fibrillation, would be of essential impact, taking into consideration the widespread use of substrate-based strategies. Importantly, all limitations need to be solved before application of CMR-guided ablation in a broad clinical setting.

Innovations in ventricular tachycardia ablation

Catheter ablation of ventricular arrhythmias (VAs) has evolved significantly over the past decade and is currently a well-established therapeutic option. Technological advances and improved understanding of VA mechanisms have led to tremendous innovations in VA ablation. The purpose of this review article is to provide an overview of current innovations in VA ablation. Mapping techniques, such as ultra-high density mapping, isochronal late activation mapping, and ripple mapping, have provided improved arrhythmogenic substrate delineation and potential procedural success while limiting duration of ablation procedure and potential hemodynamic compromise. Besides, more advanced mapping and ablation techniques such as epicardial and intramyocardial ablation approaches have allowed operators to more precisely target arrhythmogenic substrate. Moreover, advances in alternate energy sources, such as electroporation, as well as stereotactic radiation therapy have been proposed to be effective and safe. New catheters, such as the lattice and the saline-enhanced radiofrequency catheters, have been designed to provide deeper and more durable tissue ablation lesions compared to conventional catheters. Contact force optimization and baseline impedance modulation are important tools to optimize VT radiofrequency ablation and improve procedural success. Furthermore, advances in cardiac imaging, specifically cardiac MRI, have great potential in identifying arrhythmogenic substrate and evaluating ablation success. Overall, VA ablation has undergone significant advances over the past years. Innovations in VA mapping techniques, alternate energy source, new catheters, and utilization of cardiac imaging have great potential to improve overall procedural safety, hemodynamic stability, and procedural success.

Twenty-five years of research in cardiac imaging in electrophysiology procedures for atrial and ventricular arrhythmias

Catheter ablation is nowadays considered the treatment of choice for numerous cardiac arrhythmias in different clinical scenarios. Fluoroscopy has traditionally been the primary imaging modality for catheter ablation, providing real-time visualization of catheter navigation. However, its limitations, such as inadequate soft tissue visualization and exposure to ionizing radiation, have prompted the integration of alternative imaging modalities. Over the years, advancements in imaging techniques have played a pivotal role in enhancing the safety, efficacy, and efficiency of catheter ablation procedures. This manuscript aims to explore the utility of imaging, including electroanatomical mapping, cardiac computed tomography, echocardiography, cardiac magnetic resonance, and nuclear cardiology exams, in helping electrophysiology procedures. These techniques enable accurate anatomical guidance, identification of critical structures and substrates, and real-time monitoring of complications, ultimately enhancing procedural safety and success rates. Incorporating advanced imaging technologies into routine clinical practice has the potential to further improve clinical outcomes of catheter ablation procedures and pave the way for more personalized and precise ablation therapies in the future.

Interventional cardiovascular magnetic resonance: state-of-the-art

Transcatheter cardiovascular interventions increasingly rely on advanced imaging. X-ray fluoroscopy provides excellent visualization of catheters and devices, but poor visualization of anatomy. In contrast, magnetic resonance imaging (MRI) provides excellent visualization of anatomy and can generate real-time imaging with frame rates similar to X-ray fluoroscopy. Realization of MRI as a primary imaging modality for cardiovascular interventions has been slow, largely because existing guidewires, catheters and other devices create imaging artifacts and can heat dangerously. Nonetheless, numerous clinical centers have started interventional cardiovascular magnetic resonance (iCMR) programs for invasive hemodynamic studies or electrophysiology procedures to leverage the clear advantages of MRI tissue characterization, to quantify cardiac chamber function and flow, and to avoid ionizing radiation exposure. Clinical implementation of more complex cardiovascular interventions has been challenging because catheters and other tools require re-engineering for safety and conspicuity in the iCMR environment. However, recent innovations in scanner and interventional device technology, in particular availability of high performance low-field MRI scanners could be the inflection point, enabling a new generation of iCMR procedures. In this review we review these technical considerations, summarize contemporary clinical iCMR experience, and consider potential future applications.

Twenty-five years of catheter ablation of ventricular tachycardia: a look back and a look forward

This article will discuss the past, present, and future of ventricular tachycardia ablation and the continuing contribution of the Europace journal as the platform for publication of milestone research papers in this field of ventricular tachycardia ablation.

Management of Ventricular Arrhythmias in Heart Failure

PURPOSE OF REVIEW

Despite substantial progress in medical and device-based heart failure (HF) therapy, ventricular arrhythmias (VA) and sudden cardiac death (SCD) remain a major challenge. Here we review contemporary management of VA in the context of HF with one particular focus on recent advances in imaging and catheter ablation.

RECENT FINDINGS

Besides limited efficacy of antiarrhythmic drugs (AADs), their potentially life-threatening side effects are increasingly acknowledged. On the other hand, with tremendous advances in catheter technology, electroanatomical mapping, imaging, and understanding of arrhythmia mechanisms, catheter ablation has evolved into a safe, efficacious therapy. In fact, recent randomized trials support early catheter ablation, demonstrating superiority over AAD. Importantly, CMR imaging with gadolinium contrast has emerged as a central tool for the management of VA complicating HF: CMR is not only essential for an accurate diagnosis of the underlying entity and subsequent treatment decisions, but also improves risk stratification for SCD prevention and patient selection for ICD therapy. Finally, 3-dimensional characterization of arrhythmogenic substrate by CMR and imaging-guided ablation approaches substantially enhance procedural safety and efficacy. VA management in HF patients is highly complex and should be addressed in a multidisciplinary approach, preferably at specialized centers. While recent evidence supports early catheter ablation of VA, an impact on mortality remains to be demonstrated. Moreover, risk stratification for ICD therapy may have to be reconsidered, taking into account imaging, genetic testing, and other parameters beyond left ventricular function.

Impact of filter configurations on bipolar EGMs: An optimal filter setting for identifying VT substrates

BACKGROUND

The impact of filtering on bipolar electrograms (EGMs) has not been systematically examined. We tried to clarify the optimal filter configuration for ventricular tachycardia (VT) ablation.

METHODS

Fifteen patients with VT were included. Eight different filter configurations were prospectively created for the distal bipoles of the ablation catheter: 1.0-250, 10-250, 100-250, 30-50, 30-100, 30-250, 30-500, and 30-1000 Hz. Pre-ablation stable EGMs with good contact (contact force > 10 g) were analyzed. Baseline fluctuation, baseline noise, bipolar peak-to-peak voltage, and presence of local abnormal ventricular activity (LAVA) were compared between different filter configurations.

RESULTS

In total, 2276 EGMs with multiple bipolar configurations in 246 sites in scar and border areas were analyzed. Baseline fluctuation was only observed in the high-pass filter of (HPF) ≤ 10 Hz (p < .001). Noise level was lowest at 30-50 Hz (0.018 [0.012-0.029] mV), increased as the low-pass filter (LPF) extended, and was highest at 30-1000 Hz (0.047 [0.041-0.061] mV) (p < .001). Conversely, the HPF did not affect the noise level at ≤30 Hz. As the HPF extended to 100 Hz, bipolar voltages significantly decreased (p < .001), but were not affected when the LPF was extended to ≥100 Hz. LAVAs were most frequently detected at 30-250 Hz (207/246; 84.2%) and 30-500 Hz (208/246; 84.6%), followed by 30-1000 Hz (205/246; 83.3%), but frequently missed at LPF ≤ 100 Hz or HPF ≤ 10 Hz (p < .001). A 50-Hz notch-filter reduced the bipolar voltage by 43.9% and LAVA-detection by 34.5% (p < .0001).

CONCLUSION

Bipolar EGMs are strongly affected by filter settings in scar/border areas. In all, 30-250 or 30-500 Hz may be the best configuration, minimizing the baseline fluctuation, baseline noise, and detecting LAVAs. Not applying the 50-Hz notch filter may be beneficial to avoid missing VT substrate.

Utility of Substrate Mapping Using Extrasystole to Localise Comprehensive Ventricular Tachycardia Circuits: Results From Intra-operative Mapping Studies

BACKGROUND

Substrate mapping-based identification of all ventricular tachycardia (VT) circuits (diastolic activation), including partial and complete diastolic circuits in clinical and nonclinical VT, could be beneficial in guiding VT ablation to prevent VT recurrence. The utility of extrasystole induced late potentials has not been compared with late potentials in sinus rhythm (SR) and right ventricular pacing (RVp).

METHODS

Intraoperative simultaneous panoramic endocardial mapping of 21 VTs in 16 ischemic heart disease patients was performed with the use of a 112-bipole endocardial balloon. The decrement of near-field electrogram later than surface QRS during extrasystole (eLP) was studied.

RESULTS

Patients had a mean age of 52 ± 9 years and were predominantly (75%) male. The mean sensitivity of eLP (0.75 [95% confidence interval [CI] 0.72-0.78]) to detect VT circuits was better than SR (0.33 [0.30-0.36]; P < 0.001) and RVp (0.36 [0.33-0.39]; P < 0.001) without significant differences in specificity, eLP (0.77 [0.74-0.81], SR (0.82 [0.80-0.84]; P = 0.23), and RVp (0.81 [0.78-0.83]; P = 0.11). Both negative (NPV) and positivie (PPV) predictive values were significantly better for eLP mapping. The mean NPV was 0.77 (95% CI 0.74-0.81), 0.57 (0.55-0.59), and 0.58 (0.55-0.61) for eLP, SR, and RVp, respectively (P < 0.0001). PPV was 0.75 (95% CI 0.72-0.78), 0.63 (0.59-0.67), and 0.63 (0.59-0.67) for eLP, SR, and RVp, respectively (P < 0.001). Overall diagnostic performance (area under the receiver operating characteristic curve) was significantly better for eLP (0.85 [95% CI 0.80-0.90] compared with SR (0.63 [0.56-0.72]; P < 0.001) or RVp (0.61 [0.52-0.74]; P < 0.001).

CONCLUSIONS

Evoked late potential mapping is a better tool to detect comprehensive diastolic circuits activated during VT, compared with eLP mapping in sinus rhythm or RV pacing.

Procedural Adaptations to Avoid Haemodynamic Instability During Catheter Ablation of Scar-related Ventricular Tachycardia

Classically, catheter ablation for scar-related ventricular tachycardia (VT) relied upon activation and entrainment mapping of induced VT. Advances in post-MI therapies have led to VTs that are faster and haemodynamically less stable, because of more heterogeneous myocardial fibrosis patterns. The PAINESD score is one means of identifying patients at highest risk for haemodynamic decompensation during attempted VT induction, who may, therefore, benefit from alternative ablation strategies. One strategy is to use temporary mechanical circulatory support, although this warrants formal assessment of cost-effectiveness. A second strategy is to minimise or avoid VT induction altogether by employing a family of 'substrate'-based approaches aimed at identifying VT isthmuses during sinus or paced rhythm. Substrate mapping techniques are diverse, and focus on the timing, morphology and amplitude of local ventricular electrograms - sometimes aided by advanced non-invasive cardiac imaging modalities. In this review, the evolution of VT ablation over time is discussed, with an emphasis on procedural adaptations to the challenge of haemodynamic instability.

Advanced Imaging Integration for Catheter Ablation of Ventricular Tachycardia

PURPOSE OF REVIEW

Imaging plays a crucial role in the therapy of ventricular tachycardia (VT). We offer an overview of the different methods and provide information on their use in a clinical setting.

RECENT FINDINGS

The use of imaging in VT has progressed recently. Intracardiac echography facilitates catheter navigation and the targeting of moving intracardiac structures. Integration of pre-procedural CT or MRI allows for targeting the VT substrate, with major expected impact on VT ablation efficacy and efficiency. Advances in computational modeling may further enhance the performance of imaging, giving access to pre-operative simulation of VT. These advances in non-invasive diagnosis are increasingly being coupled with non-invasive approaches for therapy delivery. This review highlights the latest research on the use of imaging in VT procedures. Image-based strategies are progressively shifting from using images as an adjunct tool to electrophysiological techniques, to an integration of imaging as a central element of the treatment strategy.

Solving the Reach Problem: A Review of Present and Future Approaches for Addressing Ventricular Arrhythmias Arising from Deep Substrate

Ventricular tachycardia (VT) is a significant cause of morbidity and mortality in patients with ischaemic and non-ischaemic cardiomyopathies. In most patients, the primary strategy of VT catheter ablation is based on the identification of critical components of reentry circuits and modification of abnormal substrate which can initiate reentry. Despite technological advancements in catheter design and improved ability to localise abnormal substrates, putative circuits and site of origins of ventricular arrhythmias (VAs), current technologies remain inadequate and durable success may be elusive when the critical substrate is deep or near to critical structures that are at risk of collateral damage. In this article, we review the available and potential future non-surgical investigational approaches for treatment of VAs and discuss the viability of these modalities.

Scar conducting channel characterization to predict arrhythmogenicity during ventricular tachycardia ablation

AIMS

Heterogeneous tissue channels (HTCs) detected by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) are related to ventricular arrhythmias, but there are few published data about their arrhythmogenic characteristics.

METHODS AND RESULTS

We enrolled 34 consecutive patients with ischaemic and non-ischaemic cardiomyopathy who were referred for ventricular tachycardia (VT) ablation. LGE-CMR was performed prior to ablation, and the HTCs were analyzed. Arrhythmogenic HTCs linked to induced VT were identified during the VT ablation procedure. The characteristics of arrhythmogenic HTCs were compared with those of non-arrhythmogenic HTCs. Three patients were excluded due to low-quality LGE-CMR images. A total of 87 HTCs were identified on LGE-CMR in 31 patients (age:63.8 ± 12.3 years; 96.8% male; left ventricular ejection fraction: 36.1 ± 10.7%). Of the 87 HTCs, only 31 were considered arrhythmogenic because of their relation to a VT isthmus. The HTCs related to a VT isthmus were longer [64.6 ± 49.4 vs. 32.9 ± 26.6 mm; OR: 1.02; 95% CI: (1.01-1.04); P < 0.001] and had greater mass [2.5 ± 2.2 vs. 1.2 ± 1.2 grams; OR: 1.62; 95% CI: (1.18-2.21); P < 0.001], a higher degree of protectedness [26.19 ± 19.2 vs. 10.74 ± 8.4; OR 1.09; 95% CI: (1.04-1.14); P < 0.001], higher transmurality [number of wall layers with CCs: 3.8 ± 2.4 vs. 2.4 ± 2.0; OR: 1.31; 95% CI: (1.07-1.60); P = 0.008] and more ramifications [3.8 ± 2.0 vs. 2.7 ± 1.1; OR: 1.59; 95% CI: (1.15-2.19); P = 0.002] than non-arrhythmogenic HTCs. Multivariate logistic regression analysis revealed that protectedness was the strongest predictor of arrhythmogenicity.

CONCLUSION

The protectedness of an HTC identified by LGE-CMR is strongly related to its arrhythmogenicity during VT ablation.

The scar: the wind in the perfect storm-insights into the mysterious living tissue originating ventricular arrhythmias

BACKGROUND

Arrhythmic death is very common among patients with structural heart disease, and it is estimated that in European countries, 1 per 1000 inhabitants yearly dies for sudden cardiac death (SCD), mainly as a result of ventricular arrhythmias (VA). The scar is the result of cardiac remodelling process that occurs in several cardiomyopathies, both ischemic and non-ischemic, and is considered the perfect substrate for re-entrant and non-re-entrant arrhythmias.

METHODS

Our aim was to review published evidence on the histological and electrophysiological properties of myocardial scar and to review the central role of cardiac magnetic resonance (CMR) in assessing ventricular arrhythmias substrate and its potential implication in risk stratification of SCD.

RESULTS

Scarring process affects both structural and electrical myocardial properties and paves the background for enhanced arrhythmogenicity. Non-uniform anisotropic conduction, gap junctions remodelling, source to sink mismatch and refractoriness dispersion are some of the underlining mechanisms contributing to arrhythmic potential of the scar. All these mechanisms lead to the initiation and maintenance of VA. CMR has a crucial role in the evaluation of patients suffering from VA, as it is considered the gold standard imaging test for scar characterization. Mounting evidences support the use of CMR not only for the definition of gross scar features, as size, localization and transmurality, but also for the identification of possible conducting channels suitable of discrete ablation. Moreover, several studies call out the CMR-based scar characterization as a stratification tool useful in selecting patients at risk of SCD and amenable to implantable cardioverter-defibrillator (ICD) implantation.

CONCLUSIONS

Scar represents the substrate of ventricular arrhythmias. CMR, defining scar presence and its features, may be a useful tool for guiding ablation procedures and for identifying patients at risk of SCD amenable to ICD therapy.

Catheter ablation of ventricular tachycardia associated with structural heart disease: Current status and perspectives

Catheter ablation is an effective and safe treatment for ventricular tachycardia attributable to structural heart disease, reducing the risk of recurrent arrhythmias and defibrillator shock therapy. Advances in medical technology and an accumulation of data have led to the development of detailed guidelines. Successful ablation requires accurate identification of the arrhythmia substrate and effective delivery of radiofrequency energy to the target tissue. Modern practice requires use of traditional electrophysiological mapping processes such as entrainment mapping and three-dimensional activation sequence mapping in combination with newer functional mapping techniques for which there is growing support. Thorough non-invasive preoperative assessment is also necessary before an invasive procedure is undertaken. In this review, we summarize contemporary practice and recent randomized controlled trials underpinning the latest developments in mapping and ablation and discuss potential future developments in this field.

Scar border zone mass and presence of border zone channels assessed with cardiac magnetic resonance imaging are associated with ventricular arrhythmia in patients with ST-segment elevation myocardial infarction

AIMS

Late gadolinium enhancement cardiac magnetic resonance (CMR) permits characterization of left ventricular ischaemic scars. We aimed to evaluate if scar core mass, border zone (BZ) mass, and BZ channels are risk markers for subsequent ventricular arrhythmia (VA) in ST-segment elevation myocardial infarction (STEMI).

METHODS AND RESULTS

A sub-study of the DANish Acute Myocardial Infarction-3 multi-centre trial and Danegaptide phase II proof-of-concept clinical trial in which a total of 843 STEMI patients had a 3-month follow-up CMR. Of these, 21 patients subsequently experienced VA during 100 months of follow-up and were randomly matched 1:5 with 105 controls. A VA event was defined as: ventricular tachycardia, ventricular fibrillation, or sudden cardiac death. Ischaemic scar characteristics were automatically detected by specialized software. We included 126 patients with a median left ventricular ejection fraction of 51.0 ± 11.6% in cases with VA vs. 55.5 ± 8.5% in controls (P = 0.10). Cases had a larger mean BZ mass and more often BZ channels compared to controls [BZ mass: 17.2 ± 10.3 g vs. 10.3 ± 6.0 g; P = 0.0002; BZ channels: 17 (80%) vs. 44 (42%); P = 0.001]. A combination of ≥17.2 g BZ mass and the presence of BZ channels was five times more prevalent in cases vs. controls (P ≤ 0.00001) with an odds ratio of 9.40 (95% confidence interval 3.26-27.13; P ≤ 0.0001) for VA. This identified cases with 52% sensitivity and 90% specificity.

CONCLUSION(S)

Scar characterization with CMR indicates that a combination of ≥17.2 g BZ mass and the presence of BZ channels had the strongest association with subsequent VA in STEMI patients.

CLINICALTRIALS.GOV

Unique identifier: NCT01435408 (DANAMI 3-iPOST and DANAMI 3-DEFER), NCT01960933 (DANAMI 3-PRIMULTI), and NCT01977755 (Danegaptide).

Patient Selection, Techniques, and Complication Mitigation for Epicardial Ventricular Tachycardia Ablation

Percutaneous epicardial ventricular tachycardia ablation can decrease implanted cardioverter defibrillator shocks and hospitalizations; proper patient selection and procedural technique are imperative to maximize the benefit-risk ratio. The best candidates for epicardial ventricular tachycardia will depend on history of prior ablation, type of cardiomyopathy, and specific electrocardiogram and cardiac imaging findings. Complications include hemopericardium, hemoperitoneum, coronary vessel injury, and phrenic nerve injury. Modern epicardial mapping techniques provide new understandings of the 3-dimensional nature of reentrant ventricular tachycardia circuits across cardiomyopathy etiologies. Where epicardial access is not feasible, alternative techniques to reach epicardial ventricular tachycardia sources may be necessary.

Best Practices for the Catheter Ablation of Ventricular Arrhythmias

Techniques for catheter ablation have evolved to effectively treat a range of ventricular arrhythmias. Pre-operative electrocardiographic and cardiac imaging data are very useful in understanding the arrhythmogenic substrate and can guide mapping and ablation. In this review, we focus on best practices for catheter ablation, with emphasis on tailoring ablation strategies, based on the presence or absence of structural heart disease, underlying clinical status, and hemodynamic stability of the ventricular arrhythmia. We discuss steps to make ablation safe and prevent complications, and techniques to improve the efficacy of ablation, including optimal use of electroanatomical mapping algorithms, energy delivery, intracardiac echocardiography, and selective use of mechanical circulatory support.

Improving Outcomes in Ventricular Tachycardia Ablation Using Imaging to Identify Arrhythmic Substrates

Ventricular tachycardia (VT) ablation is limited by modest acute and long-term success rates, in part due to the challenges in accurately identifying the arrhythmogenic substrate. The combination of multimodality imaging along with information from electroanatomic mapping allows for a more comprehensive assessment of the arrhythmogenic substrate which facilitates VT ablation, and the use of preprocedural imaging has been shown to improve long-term ablation outcomes. Beyond regional recognition of the arrhythmogenic substrate, advanced imaging techniques can be used to create tailored ablation strategies preprocedurally. This review will focus on how imaging can be used to guide ablation planning and execution with a focus on clinical applications aimed at improving the outcome of VT ablation procedures.

Early de-cannulation from extracorporeal membrane oxygenation following ventricular tachycardia radiofrequency ablation

Objectives

Ventricular tachycardia ablation (VTA) with hemodynamic compromise presents a challenge. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support allows the safe completion of the procedure. There are limited data regarding the safety of weaning off VA-ECMO at the end of the procedure. We report our experience with early VA-ECMO de-cannulation after VTA.

Materials and methods

All patients undergoing VA-ECMO-assisted VTA, between January 2013 and December 2020 at a large tertiary center were included. Clinical characteristics, history of arrhythmia, procedural details, and outcomes were collected. Patients weaned from VA-ECMO immediately at the end of the procedure were compared to those that were de-cannulated at a later time.

Results

A total of 46 patients (93.5% male, age 62 ± 10 years) were ablated with VA-ECMO support. Most had ischemic cardiomyopathy (65%) and (70%) presented with VT storm. The clinical VT was induced in the majority of patients (76%). A total of 99 VTs were induced of which 76 (77%) were targeted and successfully ablated. Non-inducibility was achieved in 74% of cases and most patients (83%) were de-cannulated at the end of the procedure on the procedure table. Survival at 1 year was higher among early de-cannulated patients (86 vs. 38% [log-rank p-value < 0.001]). At 1-year follow-up, 91.3% of surviving patients were free of appropriate ICD shocks.

Conclusion

De-cannulation from VA-ECMO may be done immediately at the conclusion of VTA in most cases. Failure to timely wean off VA-ECMO is a strong predictor of mortality.

Fat infiltration in the infarcted heart as a paradigm for ventricular arrhythmias

Infiltrating adipose tissue (inFAT) has been recently found to co-localize with scar in infarcted hearts and may contribute to ventricular arrhythmias (VAs), a life-threatening heart rhythm disorder. However, the contribution of inFAT to VA has not been well-established. We investigated the role of inFAT versus scar in VA through a combined prospective clinical and mechanistic computational study. Using personalized computational heart models and comparing the results from simulations of VA dynamics with measured electrophysiological abnormalities during the clinical procedure, we demonstrate that inFAT, rather than scar, is a primary driver of arrhythmogenic propensity and is frequently present in critical regions of the VA circuit. We determined that, within the VA circuitry, inFAT, as opposed to scar, is primarily responsible for conduction slowing in critical sites, mechanistically promoting VA. Our findings implicate inFAT as a dominant player in infarct-related VA, challenging existing paradigms and opening the door for unexplored anti-arrhythmic strategies.

Role of advanced imaging with cardiac computed tomography and MRI in atrial and ventricular ablation

PURPOSE OF REVIEW

Increasing evidence supports the use of advanced imaging with cardiac computed tomography (CCT) and cardiac magnetic resonance (CMR) in the work-up of patients with arrythmias being considered for ablation.

RECENT FINDINGS

Advances in imaging technology and postprocessing are facilitating the use of advanced imaging before, during and after ablation in patients with both atrial and ventricular arrhythmias.In atrial arrythmias, quantitative assessment of left atrial wall thickness on CCT and quantification of late gadolinium enhancement (LGE) on CMR identify patients more likely to develop recurrent atrial arrythmias following ablation. In addition, in patients with recurrent arrythmia post ablation, LGE CMR can potentially identify targets for repeat ablation.In ventricular arrythmias, qualitative assessment of LGE can aide in determining the optimal ablation approach and predicts likelihood of ventricular arrythmias inducibility. Quantitative assessment of LGE can identify conduction channels that can be targeted for ablation. On CCT, quantitative assessment of left ventricular wall thickness can demonstrate myocardial ridges associated with re-entrant circuits for ablation.

SUMMARY

This review focuses on the utility of CCT and CMR in identifying key anatomical components and arrhythmogenic substrate contributing to both atrial and ventricular arrhythmias in patients being considered for ablation. Advanced imaging has the potential to improve procedural outcomes, decrease complications and shorten procedural time.

Substrate-based approaches in ventricular tachycardia ablation

Catheter ablation for ventricular tachycardia (VT) in patients with structural heart disease is now part of standard care. Mapping and ablation of the clinical VT is often limited when the VT is noninducible, nonsustained or not haemodynamically tolerated. Substrate-based ablation strategies have been developed in an aim to treat VT in this setting and, subsequently, have been shown to improve outcomes in VT ablation when compared to focused ablation of mapped VTs. Since the initial description of linear ablation lines targeting ventricular scar, many different approaches to substrate-based VT ablation have been developed. Strategies can broadly be divided into three categories: 1) targeting abnormal electrograms, 2) anatomical targeting of conduction channels between areas of myocardial scar, and 3) targeting areas of slow and/or decremental conduction, identified with “functional” substrate mapping techniques. This review summarises contemporary substrate-based ablation strategies, along with their strengths and weaknesses.

Orthogonal high-density mapping with ventricular tachycardia isthmus analysis vs. pure substrate ventricular tachycardia ablation: A case-control study

Background

Substrate-based ablation has become a successful technique for ventricular tachycardia (VT) ablation. High-density (HD) mapping catheters provide high-resolution electroanatomical maps and better discrimination of local abnormal electrograms. The HD Grid Mapping Catheter is an HD catheter with the ability to map orthogonal signals on top of conventional bipolar signals, which could provide better discrimination of the arrhythmic substrate. On the other hand, conventional mapping techniques, such as activation mapping, when possible, help to identify the isthmus of the tachycardia.

Aim

The purpose of this study was to compare clinical outcomes after using two different VT ablation strategies: one based on extensive mapping with the HD Grid Mapping Catheter, including VT isthmus analysis, and the other based on pure substrate ablation.

Methods

Forty consecutive patients undergoing VT ablation with extensive HD mapping method in the hospital clinic (November 2018–November 2019) were included. Clinical outcomes were compared with a historical cohort of 26 consecutive patients who underwent ablation using a scar dechanneling technique before 2018.

Results

The density of mapping points was higher in the extensive mapping group (2370.24 ± 920.78 vs. 576.45 ± 294.46; p < 0.001). After 1 year of follow-up, VT recurred in 18.4% of patients in the extensive mapping group vs. 34.6% of patients in the historical control group (p = 0.14), with a significantly greater reduction of VT burden: VT episodes (81.7 ± 7.79 vs. 43.4 ± 19.9%, p < 0.05), antitachycardia pacing (99.45 ± 2.29 vs. 33.9 ± 102.5%, p < 0.001), and implantable cardioverter defibrillator (ICD) shocks (99 ± 4.5 vs. 64.7 ± 59.9%, p = 0.02).

Conclusion

The use of a method based on extensive mapping with the HD Grid Mapping Catheter and VT isthmus analysis allows better discrimination of the arrhythmic substrate and could be associated with a greater decrease in VT burden.

Late Potential Abolition in Ventricular Tachycardia Ablation

Ventricular tachycardia (VT) substrate-based ablation has become the gold standard treatment for patients with structural heart disease-related VT. VT is linked to re-entry in relation to myocardial scarring, with areas of conduction block (core scar) and of slow conduction (border zone). Slow conduction areas can be detected in sinus rhythm as late potentials (LPs). LP abolition has been shown to be the best end point to avoid long-term recurrences. Our study aimed to analyze the challenges of LP abolition and the predictors of failure. We analyzed 169 consecutive patients with structural heart disease (61% ischemic cardiomyopathy, left ventricular ejection fraction: 37 ± 13%) who underwent VT ablation between 2013 and 2018. A preprocedural clinical evaluation, including cardiac magnetic resonance, was done in 66% of patients. Electroanatomical mapping with the identification of LPs was performed in all patients. Noninducibility was achieved in 71% (119), and complete LP abolition was achieved in 61% (103) of patients. Incomplete LP abolition was a powerful predictor of VT recurrence (67% vs 33%, hazard ratio 3.19 [2.1 to 4.7]; p <0.001). Lack of use of a high-density mapping catheter (odds ratio 6.2, 1.2 to 38.1; p = 0.028), the septal substrate (odds ratio 9.34, 2.27 to 38.4; p = 0.002), and larger left ventricular mass (190 ± 58 g vs 156 ± 46 g, p = 0.002) were predictors of incomplete LP abolition. The main reasons that contributed to unsuccessful LP abolition were anatomic obstacles (such as the conduction system) and large extension of the LP area. In conclusion, incomplete LP abolition is related to VT recurrence. Lack of use of a high-density mapping catheter, the septal substrate, and larger left ventricular mass are related to incomplete LP abolition.

Ventricular tachycardia ablation guided or aided by scar characterization with cardiac magnetic resonance: rationale and design of VOYAGE study

BACKGROUND

Radiofrequency ablation has been shown to be a safe and effective treatment for scar-related ventricular arrhythmias (VA). Recent preliminary studies have shown that real time integration of late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) images with electroanatomical map (EAM) data may lead to increased procedure efficacy, efficiency, and safety.

METHODS

VOYAGE is a prospective, randomized, multicenter controlled open label study designed to compare in terms of efficacy, efficiency, and safety a CMR aided/guided workflow to standard EAM-guided ventricular tachycardia (VT) ablation. Patients with an ICD or with ICD implantation expected within 1 month, with scar related VT, suitable for CMR and multidetector computed tomography (MDCT) will be randomized to a CMR-guided or CMR-aided approach, whereas subjects unsuitable for imaging or with image quality deemed not sufficient for postprocessing will be allocated to standard of care ablation. Primary endpoint is defined as VT recurrences (sustained or requiring appropriate ICD intervention) during 12 months follow-up, excluding the first month of blanking period. Secondary endpoints will include procedural efficiency, safety, impact on quality of life and comparison between CMR-guided and CMR-aided approaches. Patients will be evaluated at 1, 6 and 12 months.

DISCUSSION

The clinical impact of real time CMR-guided/aided ablation approaches has not been thoroughly assessed yet. This study aims at defining whether such workflow results in more effective, efficient, and safer procedures. If proven to be of benefit, results from this study could be applied in large scale interventional practice. Trial registrationClinicalTrials.gov, NCT04694079, registered on January 1, 2021.

Influence of respiration and tissue contact on ventricular substrate identification during high density mapping: results from an ovine infarct model

INTRODUCTION

Multi-electrode mapping (MEM) and automated point collection are important enhancements to substrate mapping in ventricular tachycardia ablation. The effects of tissue contact and respiration on electrogram voltage with differing depolarisation wavefronts with MEM catheters are unclear.

METHODS

Bipolar and unipolar voltages were collected from control (n=5) and infarcted (n=7) animals with a multi-spline MEM catheter. Electro-anatomic maps were created in sinus rhythm, and right and left ventricular pacing. Analysis was performed across three collection settings: standard (SS), respiratory-phase gating (RG), and electrode-tissue proximity (TP). Comparison was made to scar detected by cardiac MRI (cMRI).

RESULTS

Compared to SS and RG acquisition, median bipolar and unipolar voltages were higher using TP, regardless of the depolarization wavefront. In infarct animals, bipolar voltages were 30.7-50.5% higher for bipolar and 8.7-13.8% higher on unipolar voltages with TP, compared to SS. The effect of RG on bipolar and unipolar voltages was minimal. Percentage of local abnormal ventricular activities was not impacted by acquisition settings or wavefront direction in infarct animals. Compared with cMRI defined scar, all three acquisition settings overestimated scar area using standard voltage-based cutoffs. RG improved the low voltage area concordance with MRI by 1.6-5.1% whereas TP improved by 5.9-8.4%.

CONCLUSIONS

High density voltage mapping with a MEM catheter is influenced by point collection settings. Tissue contact filters reduced low voltage areas and improved agreement with cMRI fibrosis in infarcted ovine hearts. These findings have critical implications for optimising filter settings for high density substrate mapping in the left ventricle. This article is protected by copyright. All rights reserved.

Assessing Noninvasive Delineation of Low-Voltage Zones Using ECG Imaging in Patients With Structural Heart Disease

OBJECTIVES

This study sought to assess the association between electrocardiographic imaging (ECGI) parameters and voltage from simultaneous electroanatomic mapping (EAM).

BACKGROUND

ECGI offers noninvasive assessment of electrophysiologic features relevant for mapping ventricular arrhythmia and its substrate, but the accuracy of ECGI in the delineation of scar is unclear.

METHODS

Sixteen patients with structural heart disease underwent simultaneous ECGI (CardioInsight, Medtronic) and contact EAM (CARTO, Biosense-Webster) during ventricular tachycardia catheter ablation, with 7 mapped epicardially. ECGI and EAM geometries were coregistered using anatomic landmarks. ECGI points were paired to the closest site on the EAM within 10 mm. The association between EAM voltage and ECGI features from reconstructed epicardial unipolar electrograms was assessed by mixed-effects regression models. The classification of low-voltage regions was performed using receiver-operating characteristic analysis.

RESULTS

A total of 9,541 ECGI points (median: 596; interquartile range: 377-737 across patients) were paired to an EAM site. Epicardial EAM voltage was associated with ECGI features of signal fractionation and local repolarization dispersion (N = 7; P < 0.05), but they poorly classified sites with bipolar voltage of <1.5 mV or <0.5 mV thresholds (median area under the curve across patients: 0.50-0.62). No association was found between bipolar EAM voltage and low-amplitude reconstructed epicardial unipolar electrograms or ECGI-derived bipolar electrograms. Similar results were found in the combined cohort (n = 16), including endocardial EAM voltage compared to epicardial ECGI features (n = 9).

CONCLUSIONS

Despite a statistically significant association between ECGI features and EAM voltage, the accuracy of the delineation of low-voltage zones was modest. This may limit ECGI use for pr-procedural substrate analysis in ventricular tachycardia ablation, but it could provide value in risk assessment for ventricular arrhythmias.

Ablation Lesion Assessment with MRI

Late gadolinium enhancement (LGE) MRI is capable of detecting not only native cardiac fibrosis, but also ablation-induced scarring. Thus, it offers the unique opportunity to assess ablation lesions non-invasively. In the atrium, LGE-MRI has been shown to accurately detect and localise gaps in ablation lines. With a negative predictive value close to 100% it can reliably rule out pulmonary vein reconnection non-invasively and thus may avoid unnecessary invasive repeat procedures where a pulmonary vein isolation only approach is pursued. Even LGE-MRI-guided repeat pulmonary vein isolation has been demonstrated to be feasible as a standalone approach. LGE-MRI-based lesion assessment may also be of value to evaluate the efficacy of ventricular ablation. In this respect, the elimination of LGE-MRI-detected arrhythmogenic substrate may serve as a potential endpoint, but validation in clinical studies is lacking. Despite holding great promise, the widespread use of LGE-MRI is still limited by the absence of standardised protocols for image acquisition and post-processing. In particular, reproducibility across different centres is impeded by inconsistent thresholds and internal references to define fibrosis. Thus, uniform methodological and analytical standards are warranted to foster a broader implementation in clinical practice.

Contemporary Management of Complex Ventricular Arrhythmias

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field.

Spectral Analysis of Tissue Displacement for Cardiac Activation Mapping: Ex Vivo Working Heart and In Vivo Study

Characterizing myocardial activation is of major interest for understanding the underlying mechanism of cardiac arrhythmias. Electromechanical wave imaging (EWI) is an ultrafast ultrasound-based method used to map the propagation of the local contraction triggered by electrical activation of the heart. This study introduces a novel way to characterize cardiac activation based on the time evolution of the instantaneous frequency content of the cardiac tissue displacement curves. The first validation of this method was performed on an ex vivo dataset of 36 acquisitions acquired from two working heart models in paced rhythms. It was shown that the activation mapping described by spectral analysis of interframe displacement is similar to the standard EWI method based on zero-crossing of interframe strain. An average median error of 3.3 ms was found in the ex vivo dataset between the activation maps obtained with the two methods. The feasibility of mapping cardiac activation by EWI was then investigated on two open-chest pigs during sinus and paced rhythms in a pilot trial of cardiac mapping with an intracardiac probe. Seventy-five acquisitions were performed with reasonable stability and analyzed with the novel algorithm to map cardiac contraction propagation in the left ventricle (LV). Sixty-one qualitatively continuous isochrones were successfully computed based on this method. The region of contraction onset was coherently described while pacing in the imaging plane. These findings highlight the potential of implementing EWI acquisition on intracardiac probes and emphasize the benefit of performing short time-frequency analysis of displacement data to characterize cardiac activation in vivo.

Myocardial tissue imaging with cardiovascular magnetic resonance

Alteration in myocardial tissue, such as myocardial fibrosis, edema, inflammation, or accumulation with amyloid, lipids, or iron, has an important role in the cardiac remodeling that leads to diastolic and/or systolic dysfunction and the development of chronic heart failure, increasing the risk of adverse cardiovascular events. Thus, the early detection of changes at myocardial tissue level has great diagnostic and prognostic potential. The gold standard technique to assess these myocardial alterations is endomyocardial biopsy. However, this has been limited to a few patients due to the invasive nature, sampling errors, and its inability to assess the entire myocardium. Cardiovascular magnetic resonance (CMR) has emerged as the gold standard imaging not only for assessing cardiac volume, function quantification, and viability but also for noninvasive myocardial tissue characterization over the past decade. Its ability to characterize myocardial tissue composition is unique among noninvasive imaging modalities in cardiovascular disease. Currently, multi-parametric myocardial characterization with T1, T2, and extracellular volume has the potential to identify and track diffuse pathology in various diseases. In this review article, we present the role of established and emerging CMR techniques in myocardial tissue characterization, with an emphasis on T1 and T2 mapping, in clinical practice.

[Catheter ablation of ventricular tachycardias in patients with ischemic cardiomyopathy]

Radiofrequency (RF) ablation is an effective treatment option of scar-related ventricular tachycardias (VT) in patients with ischemic cardiomyopathy. Several studies proved the benefit of VT catheter ablation, which has become routine in most electrophysiology laboratories. This article provides practical instructions to perform a VT catheter ablation. The authors describe conventional and substrate-based mapping and ablation strategies as well as concepts for image integration. This article continues a series of publications created for education in advanced electrophysiology.

[Update on ablation of ventricular tachyarrhythmias]

Catheter ablation of ventricular tachycardia (VT) is performed with increasing frequency in clinical practice. Whereas the reported success rates of idiopathic VT are high, catheter ablation of VT in patients with structural heart disease with its scar-related re-entry mechanism may remain a challenge especially if deep intramyocardial or epicardial portions exist. The integration of modern cardiac imaging, new functional mapping strategies and catheter technologies allow optimized identification and characterization of the critical arrhythmogenic substrate and hence a more targeted VT ablation. The extent to which these innovations will have the potential to improve VT ablation success rates will be determined by future studies.

Detailed Assessment of Low-Voltage Zones Localization by Cardiac MRI in Patients With Implantable Devices

OBJECTIVES

The purpose of this study was to assess the performance and limitations of low-voltage zones (LVZ) localization by optimized late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) scar imaging in patients with cardiac implantable electronic devices (CIEDs).

BACKGROUND

Scar evaluation by LGE-CMR can assist ventricular tachycardia (VT) ablation, but challenges with electroanatomical maps coregistration and presence of imaging artefacts from CIED limit accuracy.

METHODS

A total of 10 patients underwent VT ablation and preprocedural LGE-CMR using wideband imaging. Scar was segmented from CMR pixel signal intensity maps using commercial software (ADAS-VT, Galgo Medical) with bespoke tools and compared with detailed electroanatomical maps (CARTO). Coregistration of EP and imaging-derived scar was performed using the aorta as a fiducial marker, and the impact of coregistration was determined by assessing intraobserver/interobserver variability and using computer simulations. Spatial smoothing was applied to assess correlation at different spatial resolutions and to reduce noise.

RESULTS

Pixel signal intensity maps localized low-voltage zones (V <1.5 mV) with area under the receiver-operating characteristic curve: 0.82 (interquartile range [IQR]: 0.76-0.83), sensitivity 74% (IQR: 71%-77%), and specificity 78% (IQR: 73%-83%) and correlated with bipolar voltage (r = -0.57 [IQR: -0.68 to -0.42]) across patients. In simulations, small random shifts and rotations worsened LVZ localization in at least some cases. The use of the full aortic geometry ensured high reproducibility of LVZ localization (r >0.86 for area under the receiver-operating characteristic curve). Spatial smoothing improved localization of LVZ. Results for LVZ with V <0.5 mV were similar.

CONCLUSIONS

In patients with CIEDs, novel wideband CMR sequences and personalized coregistration strategies can localize LVZ with good accuracy and may assist VT ablation procedures.