Endocardial unipolar voltage mapping to detect epicardial ventricular tachycardia substrate in patients with nonischemic left ventricular cardiomyopathy

Comparison of the residual unipolar voltage following left atrial posterior wall isolation with radiofrequency and cryoballoon catheters for persistent atrial fibrillation

BACKGROUND

Achieving transmural lesions during left atrial posterior wall isolation (LAPWI) is challenging, and the differences in the lesion transmurality between radiofrequency ablation (RFA) and cryoballoon ablation (CBA) remain unclear. Endocardial unipolar voltage mapping is reported to be more sensitive than bipolar voltage mapping for detecting intramural viable myocardium, with 1.08 mV as the cutoff threshold in the atria.

OBJECTIVE

This study compared the residual unipolar LAPW potentials after the LAPWI of persistent atrial fibrillation (PersAF) between RFA and CBA and assessed their association with atrial arrhythmia recurrence.

METHODS

We enrolled 183 patients with PersAF who underwent a pulmonary vein isolation (PVI) and LAPWI, both evaluated as successful using bipolar voltage mapping. Among them, 97 underwent RFA (RFA group) and 86 CBA (CBA group). The residual unipolar LAPW potentials exceeding 1.08 mV were analyzed, along with the residual potential area, maximum voltage, and arrhythmia recurrence rates.

RESULTS

Residual LAPW unipolar potentials >1.08 mV were more common in the RFA group than CBA group (29.9% vs. 15.1%, P=0.018), with larger potential areas (1.7±3.6 cm2 vs. 0.25±0.69 cm2; P<0.001) and higher maximum voltages (0.83±0.41 mV vs. 0.69±0.32 mV; P=0.0093). The 1-year atrial arrhythmia recurrence rate was higher in the RFA group patients with residual LAPW potentials (36.1% vs. 18.0%, P=0.033), whereas no significant difference was observed in the CBA group (15.4% vs. 18.7%, P=0.98).

CONCLUSION

Residual unipolar LAPW potentials were more prevalent and associated with arrhythmia recurrence following RFA, whereas those residual potentials had no significant impact on recurrence after CBA.

Impact of catheter ablation for ventricular tachycardia on left ventricular ejection fraction in patients with structural heart disease

Background

Catheter ablation (CA) is efficacious for the treatment of ventricular tachycardia (VT) in patients with structural heart disease; however, heart failure contributes to long-term mortality in this cohort. Whether CA worsens left ventricular function requires investigation.

Methods

We retrospectively analyzed 142 consecutive patients with structural heart disease undergoing CA for VT. Pre-ablation left ventricular ejection fraction (LVEF) was compared to LVEF postablation, predictors of change in LVEF were identified, and the relationship between change in LVEF and arrhythmic recurrence was assessed.

Results

Patients with ischemic cardiomyopathy (ICM) had lower pre-ablation LVEF than patients with non-ischemic cardiomyopathy (NICM) (36.2 ± 14.3% vs. 50.8 ± 12.8%, p < 0.001). There was no statistically significant change in LVEF following ablation for patients with ICM (p = 0.45) or NICM (p = 0.75). Patients with pre-ablation LVEF ≤20% experienced the largest recovery in LVEF, mean recovery 5.3% (95% CI: 0.6-10.1), p = 0.03, with LVEF recovery postablation similar in ICM and NICM patients (p = 0.69). Recovery of LVEF was associated with a decreased incidence of ventricular arrhythmia (VA) recurrence (p = 0.03) and an increased VA-recurrence-free survival (p = 0.04).

Conclusion

CA for VT does not cause a decline in LVEF among patients with structural heart disease. The subset of patients with severely impaired LVEF may experience an increase in LVEF following ablation and an associated reduction in VA recurrence.

Repolarization time map in catheter ablation for scar-related reentrant ventricular tachycardia

Background

Ventricular tachycardias (VTs) associated with scar tissue involve reentry mechanisms influenced by both conduction abnormalities and repolarization heterogeneity. However, existing mapping techniques have predominantly focused on conduction delay.

Methods

This retrospective study analyzed 33 consecutive cases of catheter ablation for sustained VT. The EnSite system was employed to measure repolarization time (RT) with a high-pass filter setting of 0.05 Hz. We compared the characteristics and concordance rates of short RT areas, defined as white or red-colored regions, with those identified through conventional mappings in relation to ablation targets. These short RT areas were defined based on the longest interval from the QRS onset to the maximal dV/dt point of unipolar potentials, which was divided into eight equal segments.

Results

Out of 31 VTs across 26 cases, we found that 18 (58%) of the identified ablation targets corresponded to deceleration zones (DZs). Of them, 16 (89%) also overlapped with areas of short RTs. Notably, among the remaining 13 VTs without ablation targets corresponding to DZs, 9 (69%) had ablation targets located in areas with short RTs. The distribution analysis revealed that 84% of short RT regions were located near the exit site, whereas 75% of DZs were situated near the entrance site. The distance between the two was 16 mm (interquartile range: 6.5-27.5 mm).

Conclusion

This study underscored the potential of RT mapping in identifying ablation targets in scar-related VTs. Incorporating both repolarization heterogeneity and conduction delay could significantly enhance the understanding of the intricate circuits involved in these arrhythmias.

Patient selection, ventricular tachycardia substrate delineation, and data transfer for stereotactic arrhythmia radioablation: a clinical consensus statement of the European Heart Rhythm Association of the European Society of Cardiology and the Heart Rhythm Society

Stereotactic arrhythmia radioablation (STAR) is a novel, non-invasive, and promising treatment option for ventricular arrhythmias (VAs). It has been applied in highly selected patients mainly as bailout procedure, when (multiple) catheter ablations, together with anti-arrhythmic drugs, were unable to control the VAs. Despite the increasing clinical use, there is still limited knowledge of the acute and long-term response of normal and diseased myocardium to STAR. Acute toxicity appeared to be reasonably low, but potential late adverse effects may be underreported. Among published studies, the provided methodological information is often limited, and patient selection, target volume definition, methods for determination and transfer of target volume, and techniques for treatment planning and execution differ across studies, hampering the pooling of data and comparison across studies. In addition, STAR requires close and new collaboration between clinical electrophysiologists and radiation oncologists, which is facilitated by shared knowledge in each collaborator's area of expertise and a common language. This clinical consensus statement provides uniform definition of cardiac target volumes. It aims to provide advice in patient selection for STAR including aetiology-specific aspects and advice in optimal cardiac target volume identification based on available evidence. Safety concerns and the advice for acute and long-term monitoring including the importance of standardized reporting and follow-up are covered by this document. Areas of uncertainty are listed, which require high-quality, reliable pre-clinical and clinical evidence before the expansion of STAR beyond clinical scenarios in which proven therapies are ineffective or unavailable.

Epicardial ventricular arrhythmia ablation: a clinical consensus statement of the European Heart Rhythm Association of the European Society of Cardiology and the Heart Rhythm Society, the Asian Pacific Heart Rhythm Society, the Latin American Heart Rhythm Society, and the Canadian Heart Rhythm Society

Epicardial access during electrophysiology procedures offers valuable insights and therapeutic options for managing ventricular arrhythmias (VAs). The current clinical consensus statement on epicardial VA ablation aims to provide clinicians with a comprehensive understanding of this complex clinical scenario. It offers structured advice and a systematic approach to patient management. Specific sections are devoted to anatomical considerations, criteria for epicardial access and mapping evaluation, methods of epicardial access, management of complications, training, and institutional requirements for epicardial VA ablation. This consensus is a joint effort of collaborating cardiac electrophysiology societies, including the European Heart Rhythm Association, the Heart Rhythm Society, the Asia Pacific Heart Rhythm Society, the Latin American Heart Rhythm Society, and the Canadian Heart Rhythm Society.

Clinical Impact of High-Intensity Targeted Ablation of Identifiable Critical Zones in Scar-Related Ventricular Tachycardia

BACKGROUND

Ventricular tachycardia (VT) isthmus boundaries correlate with a localized line of conduction block (LOB) identified by substrate mapping during baseline rhythm. In particular, a rotational activation pattern (RAP), which is characterized as a wavefront propagation pivoting around the edge of the fixed LOB accompanied by conduction slowing, may have a high proclivity toward re-entry.

OBJECTIVES

This study aimed to assess outcomes of ablation targeting the RAP around the LOB identifiable during substrate mapping.

METHODS

We studied 81 patients (median age 68 years; 85% male; 25% ischemic cardiomyopathy) who underwent ablation primarily targeting the regions exhibiting a RAP around the LOB associated with clinical VT.

RESULTS

High-resolution substrate mapping identified a RAP in 41 patients (51%). Of these, 30 patients (Group A) underwent ablation of an area with a radius >1 cm, including the targeted RAP regions. In 11 patients (Group B), RAPs were unable to be ablated because of the proximity of the RAP site to the conduction system, coronary arteries, or phrenic nerves, or based on the operator's discretion to avoid hemodynamic decompensation. The remaining 40 patients (Group C) had no identifiable RAP, and none of them had no mid-diastolic activities during VT due to intramural or contra-surface arrhythmogenic substrate. During 1-year follow-up, 83% freedom from VT recurrence was achieved in Group A, compared with 41% and 39% in Groups B and C, respectively (P = 0.003).

CONCLUSIONS

The identification of critical zones of the VT re-entrant circuit, which may be co-localized with regions hosting RAP around the LOB, as well as high-intensity ablation targeting these regions, appear to be important for successful ablation.

Whole-Heart Histological and CMR Validation of Electroanatomic Mapping by Multielectrode Catheters in an Ovine Model

BACKGROUND

Accurate electroanatomic mapping is critical for identifying scar and the long-term success of ventricular tachycardia ablation.

OBJECTIVES

This study sought to determine the accuracy of multielectrode mapping (MEM) catheters to identify scar on cardiac magnetic resonance (CMR) and histopathology.

METHODS

In an ovine model of myocardial infarction, we examined the effect of electrode size, spacing, and mapping rhythm on scar identification compared to CMR and histopathology using 5 multielectrode mapping catheters. We co-registered electroanatomic mapping, CMR, and histopathology for comparison. Catheter-specific voltage thresholds were identified based on underlying amounts of normal myocardium on transmural histology biopsies.

RESULTS

Ten animals were included: 6 with anteroseptal myocardial infarction and 4 control animals. A total of 419,597 points were manually reviewed across the catheters, with 315,487 points used in the analysis. There were minimal differences in bipolar and unipolar voltages, scar areas, and abnormal electrograms between catheters and between rhythms. Catheter-specific bipolar and unipolar voltage thresholds for normal myocardium were High-Density Grid >2.78 mV and >6.19 mV, DuoDecapolar >2.22 mV and >6.05 mV, PentaRay >1.66 mV and >5.35 mV, Decanav >1.36 mV and >4.75 mV, Orion >1.21 mV and >6.05 mV, respectively. Catheter-specific bipolar thresholds improved the accuracy for detecting endo-mid myocardial scar on CMR by 1.8%-15.6% and catheter-specific unipolar thresholds improved the accuracy in the mid-epicardial layers by 25.3%-81.1%.

CONCLUSIONS

Minimal differences were observed in scar detection and electrogram markers between commercially available multielectrode mapping catheters and differing wave fronts. Compared to traditional voltage criteria for bipolar and unipolar scar, catheter-specific thresholds markedly improved accuracy for delineating scar on CMR.

Personalized Heart Digital Twins Detect Substrate Abnormalities in Scar-Dependent Ventricular Tachycardia

BACKGROUND

Current outcomes from catheter ablation for scar-dependent ventricular tachycardia (VT) are limited by high recurrence rates and long procedure durations. Personalized heart digital twin technology presents a noninvasive method of predicting critical substrate in VT, and its integration into clinical VT ablation offers a promising solution. The accuracy of the predictions of digital twins to detect invasive substrate abnormalities is unknown. We present the first prospective analysis of digital twin technology in predicting critical substrate abnormalities in VT.

METHODS

Heart digital twin models were created from 18 patients with scar-dependent VT undergoing catheter ablation. Contrast-enhanced cardiac magnetic resonance images were used to reconstruct finite-element meshes, onto which regional electrophysiological properties were applied. Rapid-pacing protocols were used to induce VTs and to define the VT circuits. Predicted optimum ablation sites to terminate all VTs in the models were identified. Invasive substrate mapping was performed, and the digital twins were merged with the electroanatomical map. Electrogram abnormalities and regions of conduction slowing were compared between digital twin-predicted sites and nonpredicted areas.

RESULTS

Electrogram abnormalities were significantly more frequent in digital twin-predicted sites compared with nonpredicted sites (468/1029 [45.5%] versus 519/1611 [32.2%]; P<0.001). Electrogram duration was longer at predicted sites compared with nonpredicted sites (82.0±25.9 milliseconds versus 69.7±22.3 milliseconds; P<0.001). Digital twins correctly identified 21 of 26 (80.8%) deceleration zones seen on isochronal late activation mapping.

CONCLUSIONS

Digital twin-predicted sites display a higher prevalence of abnormal and prolonged electrograms compared with nonpredicted sites and accurately identify regions of conduction slowing. Digital twin technology may help improve substrate-based VT ablation.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04632394.

Ventricular tachycardia substrate mapping: What's been done and what needs to be done

Substrate mapping is an important component of electrophysiological (EP) study for the treatment of reentrant ventricular tachycardia (VT). It is used to detect characteristics of the electrical circuit and, in particular, the location and properties of the central common pathway, aka the isthmus, where multiple circuit loops can coincide. Typically, reentrant circuits are single or double loop, but as the common pathway size increases, 4-loop patterns may emerge, consisting of 2 parallel isthmuses or a single isthmus with 4 loops. Arrhythmogenic substrate contains a mixture of scar, calcification, and fibrofatty regions blended with viable ventricular myocytes, which can slow conduction. It is identified in the EP laboratory in part by the presence of low-amplitude electrograms and a zone of uniform slow conduction resulting from a sparsity of remaining viable myocytes and molecular-level remodeling. The electrograms recorded near isthmus boundaries frequently exhibit an abnormal morphology, such as fractionation and late or split deflections, due to the separation of muscle fiber bundles by fibroadipose tissue or calcification, and due to other conduction impediments such as source-sink mismatch, wherein topographic changes to the viable myocardial structure occur. Substrate mapping facilitates the identification of arrhythmogenic regions during sinus rhythm, whereas inducible VT with periods of ongoing reentry, when recordable, can be used for further assessment. Substrate modeling augments substrate mapping by seeking to predict electrogram morphology and mapped features and properties to be encountered during EP study based on an accurate depiction of arrhythmogenic tissue. Herein, we elaborate on the details of VT substrate mapping and modeling to the present time.

Unipolar Voltage Mapping to Predict Recovery of Left Ventricular Ejection Fraction in Patients With Recent-Onset Nonischemic Cardiomyopathy

BACKGROUND

The ability to predict recovery of left ventricular ejection fraction (LVEF) in response to guideline-directed therapy among patients with nonischemic cardiomyopathy is desired. We sought to determine whether left ventricular endocardial unipolar voltage measured during invasive electroanatomic mapping could be used to predict LVEF recovery among those with recent-onset nonischemic cardiomyopathy.

METHODS

We analyzed the left ventricular voltage maps of patients included in the eMAP trial (Electrogram-Guided Myocardial Advanced Phenotyping; NCT03293381), a prospective, nonrandomized, interventional trial conducted at 2 institutions between 2017 and 2020. Patients had recent-onset nonischemic cardiomyopathy defined by LVEF ≤45% and development of symptoms or signs of heart failure within the past 6 months. Detailed voltage maps of the left ventricular endocardium were generated using the Carto electroanatomic mapping system. Abnormal unipolar amplitude was defined as <8.27 mV. The primary end point was recovery of LVEF (Recovery) defined by a 1-year LVEF ≥50% or ≥45% with ≥10% increase from baseline.

RESULTS

Of the 29 enrolled patients (median age, 49 years [25th percentile, 39; 75th percentile, 59], 8 females [27.6%]), LVEF recovered in 13 (44.8%) by 1-year follow-up. The percentage of total endocardial surface area with unipolar voltage abnormality (AUA) was significantly lower among Recovery patients than No Recovery patients (18.2% [25th percentile, 6.4; 75th percentile, 22.4] versus 80.0% [25th percentile, 29.5; 75th percentile, 90.9]; P=0.004). Percent AUA was associated with lower likelihood of Recovery (odds ratio, 0.64 per 10% increase in AUA; 95% CI, 0.47-0.88; P=0.006). A 28% cutoff value for percent AUA was 92% sensitive and 75% specific with an area under the receiver operating characteristic curve of 0.81 (95% CI, 0.63-0.99; P=0.001) for predicting recovery versus no recovery. The majority of patients (12 of 13; 92.3%) with a percent AUA >28% did not recover.

CONCLUSIONS

Left ventricular unipolar voltage abnormality is a potent predictor of LVEF recovery among patients recently diagnosed with nonischemic cardiomyopathy. Detailed left ventricular unipolar voltage mapping could therefore be used as a valuable prognostic tool in guiding treatment decisions.

Moving from voltage mapping to scar mapping using novel "near-field" metrics

BACKGROUND

In ventricular arrhythmia ablation procedures, traditional voltage mapping calculates overall peak-to-peak measurements. However, this methodology incorporates multiple signal components that do not distinguish near-field vs far-field components.

OBJECTIVE

This study aimed to determine how the use of local bipolar measurements as identified by the first derivative of voltage over time (dV/dT) affects traditional voltage mapping characteristics.

METHODS

Percutaneous endocardial and epicardial electroanatomic mapping was performed in a porcine myocardial infarction model (n = 5) with a multipolar and a point-by-point catheter. Electrograms were examined offline based on standard bipolar and unipolar voltage values and then reanalyzed by a novel algorithm that measures only the voltage magnitude pertaining to the maximum absolute dV/dT within a given electrogram. Computed tomography, gross pathology, and histopathology features were examined.

RESULTS

There were 25,114 bipolar mapping points across multipolar catheter maps and 6317 mapping points across point-by-point catheter maps. A difference in calculated voltage occurred in >80% of all mapping points, with all changes using dV/dT methodology resulting in lower bipolar voltage values compared with traditional methods. There was a categorical change in standard voltage (scar, border zone, normal) in >7% of all points. Unipolar voltage calculated by local dV/dT also resulted in a lower value in >90% of all mapping points. Histologic examination of discrepant regions revealed patterns of diffuse fibrosis.

CONCLUSION

In a porcine infarct model, the use of dV/dT to identify bipolar voltage results in lower measured values in >80% of all mapping points compared with traditional peak-to-peak measurement. This methodology may more accurately identify local tissue properties by selection of near-field components within substrates implicated in ventricular arrhythmias.

Distribution of myocardial fibrosis in patients with nonischemic cardiomyopathy and ventricular tachycardia based on genetic variant

BACKGROUND

Many genetic nonischemic dilated cardiomyopathies (NICMs) cause ventricular tachycardias (VTs) originating from scar substrate identified as areas of low electrogram voltage. Substrate locations vary, and the causes of scar are not well defined.

OBJECTIVE

This study evaluated VT substrate locations in genetic NICM patients undergoing VT ablation to evaluate spatial relationships between specific variants and substrate locations.

METHODS

In this retrospective case series analysis, 32 patients (aged 55 ± 16 years; 94% male; left ventricular ejection fraction, 34% ± 13%) with genetic NICM referred for VT ablation between October 2018 and November 2022 at a single medical center were evaluated. Scar locations were defined as areas of low unipolar or bipolar voltage.

RESULTS

Of the 32 patients evaluated, mutations in TTN (n = 11), LMNA (n = 6), PKP2 (n = 5), MYBPC3 (n = 3), DSP (n = 2), TTR (n = 1), FLNC (n = 1), AGL (n = 1), DES (n = 1), and DSG2 (n = 1) were observed. Substrates associated with mutations in TTN were observed only in basal subregions, predominantly anterior (100%) and septal (50%) regions. LMNA mutations were associated with fibrosis in mid inferolateral (60%) and apical inferolateral (60%) regions. Substrate location for individuals with PKP2 mutations was solely observed in the right ventricle, predominantly basal inferolateral regions.

CONCLUSION

Understanding spatial relationships between genetic variants causing NICM and VT substrate locations can help lead to generalizable regions in patients with genetically related NICM presenting in VT, which can be investigated during ablation procedures.

Emergent Ablation for Ventricular Tachycardia: Predictors of Prolonged Hospitalization and Mortality

BACKGROUND

Patients with ventricular tachycardia (VT) frequently present in unstable VT and are subject to urgent/high-risk ablation procedures. Clinical predictors of prolonged hospitalization and mortality are needed for optimal management of these patients.

OBJECTIVES

This study seeks to identify factors associated with prolonged hospitalization and mortality in emergent unplanned VT ablation procedures.

METHODS

Fifty consecutive patients hospitalized emergently for VT with structural heart disease who underwent catheter ablation were prospectively followed up for outcomes and complications.

RESULTS

Of the 50 patients (mean age 67.6 ± 12.8 years), 86.0% were male, 62.0% had ischemic cardiomyopathy, and their median left ventricular ejection fraction was 28.5%. Hospital stay <7 days (median 3 days) occurred in 28 (56.0%) patients (Group 1) and >7 days (median 10 days) or death <7 days occurred in 22 (44.0%) patients (Group 2). PAINESD score and left ventricular ejection fraction were similar between the groups. Compared with Group 1, Group 2 had significantly worse NYHA functional class III or higher (25.0% vs 63.6%; P = 0.006), electrical storm (46.4% vs 77.3%; P = 0.027), and prior failed VT ablation (35.7% vs 68.2%; P = 0.023). Multivariable analysis showed that NYHA functional class III or higher and prior failed VT ablation were predictive of prolonged hospital stay. After ablation, compared with Group 1, Group 2 had worse heart failure (10.7% vs 54.5%; P = 0.001), VT recurrences (3.6% vs 68.2%; P < 0.001), and 7 deaths within 30 days.

CONCLUSIONS

Patients undergoing emergent VT ablation are at high risk for prolonged hospital stay, which is predicted by NYHA functional class III or higher and a prior failed ablation. Early VT recurrences and worsening heart failure contribute to prolonged hospitalization and a high 30-day mortality.

Prognostic value of electroanatomic-guided endomyocardial biopsy in patients with myocarditis, arrhythmogenic cardiomyopathy and non dilated left ventricular cardiomyopathy

A wide variety of non-invasive and invasive techniques for SCD risk stratification in non ischemic cardiomyopathy (NICM) have been proposed, including left ventricular (LV) ejection fraction, QRS duration, late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) and invasive electrophysiologic study with or without three-dimensional electroanatomic mapping (3D-EAM), to identify and characterize the arrhythmogenic substrate. There is still no clear consensus on the risk stratification in this clinical setting. The aim of our study is to characterize the 3D-EAM substrate in patients with the same clinical presentation of unexplained complex VAs and NICM using CMR, three-dimensional electranatomic mapping (3D-EAM) in association with endomyocardial biopsy (EMB) and genetic screening, as a more precise and early diagnostic assessment may provide important subsequent prognostic impact. The study was designed as a prospective multi-center observational evaluation and the patient follow-up was scheduled at 6 months interval. We enrolled 125 patients distinct into four different group by complete diagnostic work-up: myocarditis, non-dilated left ventricular cardiomyopathy, arrhythmogenic cardiomyopathy and control group. The four groups were compared in terms of clinical, imaging and 3D-EAM data. At multivariate analysis sustained VT/VF on admission [HR: 3.64 (1.79-7.4), p < 0.001], total bipolar scar area of left and right ventricle detected by 3D-EAM [HR: 2.24 (1.13-4.49), p = 0.02], histological diagnosis of myocarditis by 3D-EAM guided endomyocardial biopsy (EBM) [HR: 2.79 (1.04-7.44), p = 0.01] were independent predictors of complex VAs or death at follow-up. 3D-EAM guided EMB represent not only a valid diagnostic tool to identify the arrhythmogenic substrate in patients with NICM and ventricular arrhythmic phenotype but also an important predictor of complex Vas at long term follow-up.

Catheter Ablation for Ventricular Tachycardias: Current Status and Future Perspectives

Catheter ablation for ventricular tachycardia (VT) in patients with systolic heart failure remains a critical yet challenging area of non-pharmacological therapy. Despite positive outcomes in atrial fibrillation, evidence for the efficacy of VT ablation in reducing cardiac mortality is inconclusive due to the absence of standardized ablation strategies. The primary challenges include difficulties in identifying suitable ablation targets and their deep locations within myocardial tissue. Current techniques, such as voltage mapping, provide valuable insights; however, they are limited by the presence of numerous bystander areas and the occurrence of incomplete transmural scarring. Recent advancements in functional substrate mapping have focused on identifying critical isthmuses without requiring hemodynamic stabilization during VT, thereby shifting the emphasis to the analysis of potentials during baseline rhythm. While methods like isochronal late activation mapping have improved target identification, they primarily address conduction abnormalities without adequately considering repolarization heterogeneity. This review highlights emerging technologies that utilize unipolar potentials to assess repolarization heterogeneities and identify VT isthmuses. Furthermore, novel ablation sources such as pulsed-field ablation, bipolar ablation, and ultra-low temperature cryoablation are being explored to create deeper and more durable lesions, addressing the limitations of traditional radiofrequency ablation. These advancements aim to reduce VT recurrence and improve overall treatment efficacy. Ultimately, understanding these innovative strategies is expected to optimize procedural outcomes and significantly enhance the management of patients with scar-related VT.

VT ablation based on CT imaging substrate visualization: results from a large cohort of ischemic and non-ischemic cardiomyopathy patients

INTRODUCTION

The eradication of ventricular tachycardia (VT) isthmus sites constitutes the minimal procedural endpoint for VT ablation procedures. Contemporary high-resolution computed tomography (CT) imaging, in combination with computer-assisted analysis and segmentation of CT data, facilitates targeted elimination of VT isthmi. In this context, inHEART offers digitally rendered three-dimensional (3D) cardiac models which allow preoperative planning for VT ablations in ischemic and non-ischemic cardiomyopathies. To date, almost no data have been collected to compare the outcomes of VT ablations utilizing inHEART with those of traditional ablation approaches.

METHODS

The presented data are derived from a retrospective analysis of n = 108 patients, with one cohort undergoing VT ablation aided by late-enhancement CT and subsequent analysis and segmentation by inHEART, while the other cohort received ablation through conventional methods like substrate mapping and activation mapping. The ablations were executed utilizing a 3D mapping system (Carto3), with the mapping generated via the CARTO® PENTARAY™ NAV catheter and subsequently merged with the inHEART model, if available.

RESULTS

Results showed more successful outcome of ablations for the inHEART group with lower VT recurrence (27% vs. 42%, p < 0.06). Subsequent analyses revealed that patients with ischemic cardiomyopathies appeared to derive a significant benefit from inHEART-assisted VT ablation procedures, with a higher rate of successful ablation (p = 0.05).

CONCLUSION

Our findings indicate that inHEART-guided ablation is associated with reduced VT recurrence compared to conventional procedures. This suggests that employing advanced imaging and computational modeling in VT ablation may be valuable for VT recurrences.

Correlation of extent of left ventricular endocardial unipolar low-voltage zones with ventricular tachycardia in nonischemic cardiomyopathy

BACKGROUND

Endocardial electrogram (EGM) characteristics in nonischemic cardiomyopathy (NICM) have not been explored adequately for prognostication.

OBJECTIVE

We aimed to study correlation of bipolar and unipolar EGM characteristics with left ventricular ejection fraction (LVEF) and ventricular tachycardia (VT) in NICM.

METHODS

Electroanatomic mapping of the left ventricle was performed. EGM characteristics were correlated with LVEF. Differences between groups with and without VT and predictors of VT were studied.

RESULTS

In 43 patients, unipolar EGM variables had better correlation with baseline LVEF than bipolar EGM variables: unipolar voltage (r = +0.36), peak negative unipolar voltage (r = -0.42), peak positive unipolar voltage (r = +0.38), and percentage area of unipolar low-voltage zone (LVZ; r = -0.41). Global mean unipolar voltage (hazard ratio [HR], 0.4; 95% confidence interval [CI], 0.2-0.8), extent of unipolar LVZ (HR, 1.6; 95% CI, 1.1-2.3), and percentage area of unipolar LVZ (HR, 1.6; 95% CI, 1.1-2.3) were significant predictors of VT. For classification of patients with VT, extent of unipolar LVZ had an area under the curve of 0.82 (95% CI, 0.69-0.95; P < .001), and percentage area of unipolar LVZ had an area under the curve of 0.83 (95% CI, 0.71-0.96; P = .01). Cutoff of >3 segments for extent of unipolar LVZ had the best diagnostic accuracy (sensitivity, 90%; specificity, 67%) and cutoff of 33% for percentage area of unipolar LVZ had the best diagnostic accuracy (sensitivity, 95%; specificity, 60%) for VT.

CONCLUSION

In NICM, extent and percentage area of unipolar LVZs are significant predictors of VT. Cutoffs of >3 segments of unipolar LVZ and >33% area of unipolar LVZ have good diagnostic accuracies for association with VT.

Effect of reference electrode on intracardiac electrograms: Close indifferent electrode vs Wilson central terminal

BACKGROUND

Unipolar electrograms (uni-EGMs) are an essential part of intracardiac mapping. Although Wilson central terminal (WCT) is conventionally used as a reference for signals, avoidance of contamination by far-field and nonphysiologic signals is challenging.

OBJECTIVE

The aim of the study was to explore the impact of an intracardiac indifferent reference electrode close to the recording electrodes, in lieu of WCT, on electrograms.

METHODS

Sinus node activation was mapped in patients undergoing catheter ablation by a multielectrode array with a close indifferent electrode (CIE) embedded in the distal end of the catheter shaft. An equal number of points was sequentially acquired at each site with use of CIE as a reference first and subsequently with WCT. Uni-EGMs, bipolar EGMs, and the earliest activation area (defined as the area activated in the first 10 ms of the beat) were compared between CIE- and WCT-based activation maps.

RESULTS

Seventeen patients (61 ± 18 years; 76% male) were studied. Uni-EGM voltages acquired with CIE were significantly larger than (n = 11) or comparable to (n = 4) those acquired with WCT. When points from the entire cohort were analyzed altogether, unipolar voltages and their maximum negative dV/dT and bipolar voltages recorded with CIE were significantly larger than those recorded with WCT (2.36 [1.42-3.79] mV vs 1.96 [1.25-3.03] mV, P < .0001; 0.40 [0.18-0.77] mV/s vs 0.35 [0.15-0.71] mV/s, P < .0001; and 1.46 [0.66-2.81] mV vs 1.33 [0.54-2.64] mV, P < .0001, respectively). The earliest activation area was significantly smaller in CIE-based activation maps than in WCT-based ones (0.3 [0.7-1.4] cm2 vs 0.6 [1.0-1.8] cm2, P = .01).

CONCLUSION

CIE-based maps were associated with an approximately 20% increase in unipolar voltage and may highlight the origin of a focal activation more clearly than WCT-based ones.

Computer based method for identification of fibrotic scars from electrograms and local activation times on the epi- and endocardial surfaces of the ventricles

Cardiac fibrosis stands as one of the most critical conditions leading to lethal cardiac arrhythmias. Identifying the precise location of cardiac fibrosis is crucial for planning clinical interventions in patients with various forms of ventricular and atrial arrhythmias. As fibrosis impedes and alters the path of electrical waves, detecting fibrosis in the heart can be achieved through analyzing electrical signals recorded from its surface. In current clinical practices, it has become feasible to record electrical activity from both the endocardial and epicardial surfaces of the heart. This paper presents a computational method for reconstructing 3D fibrosis using unipolar electrograms obtained from both surfaces of the ventricles. The proposed method calculates the percentage of fibrosis in various ventricular segments by analyzing the local activation times and peak-to-peak amplitudes of the electrograms. Initially, the method was tested using simulated data representing idealized fibrosis in a heart segment; subsequently, it was validated in the left ventricle with fibrosis obtained from a patient with nonischemic cardiomyopathy. The method successfully determined the location and extent of fibrosis in 204 segments of the left ventricle model with an average error of 0.0±4.3% (N = 204). Moreover, the method effectively detected fibrotic scars in the mid-myocardial region, a region known to present challenges in accurate detection using electrogram amplitude as the primary criterion.

Substrate and arrhythmia characterization using the multi-electrode Optrell mapping catheter for ventricular arrhythmia ablation-a single-center experience

BACKGROUND

The use of a multi-electrode Optrell mapping catheter during ventricular tachycardia (VT) or premature ventricular complex (PVC) ablation procedures has not been widely reported.

OBJECTIVES

We aim to describe the feasibility and safety of using the Optrell multipolar mapping catheter (MPMC) to guide catheter ablation of VT and PVCs.

METHODS

We conducted a single-center, retrospective evaluation of patients who underwent VT or PVC ablation between June and November 2022 utilizing the MPMC.

RESULTS

A total of 20 patients met the inclusion criteria (13 VT and 7 PVC ablations, 80% male, 61 ± 15 years). High-density mapping was performed in the VT procedures with median 2753 points [IQR 1471-17,024] collected in the endocardium and 12,830 points [IQR 2319-30,010] in the epicardium. Operators noted challenges in manipulation of the MPMC in trabeculated endocardial regions or near valve apparatus. Late potentials (LPs) were detected in 11 cases, 7 of which had evidence of isochronal crowding demonstrated during late annotation mapping. Two patients who also underwent entrainment mapping had critical circuitry confirmed in regions of isochronal crowding. In the PVC group, high-density voltage and activation mapping was performed with a median 1058 points [IQR 534-3582] collected in the endocardium.

CONCLUSIONS

This novel MPMC can be used safely and effectively to create high-density maps in LV endocardium or epicardium. Limitations of the catheter include a longer wait time for matrix formation prior to starting point collection and challenges in manipulation in certain regions.

Cryocure-VT: the safety and effectiveness of ultra-low-temperature cryoablation of monomorphic ventricular tachycardia in patients with ischaemic and non-ischaemic cardiomyopathies

AIMS

The ultra-low-temperature cryoablation (ULTC) ablation system using -196°C N2 cryogen has been reported to create lesions with freeze duration-dependent depth titratable to over 10 mm with minimum attenuation by scar. Cryocure-VT (NCT04893317) was a first-in-human clinical trial evaluating the safety and efficacy of a novel, purpose-built ULTC catheter in endocardial ablation of scar-dependent ventricular tachycardias (VTs).

METHODS AND RESULTS

This prospective, multi-centre study enrolled patients referred for de novo or second ablations of recurrent monomorphic VT of both ischaemic and non-ischaemic aetiologies. Primary safety and efficacy endpoints of the study were freedom from device- or procedure-related major adverse events (MAEs) up to 30 days post-ablation, acute non-inducibility of clinical VTs at the end of the procedure, and freedom from sustained VT or implantable defibrillator intervention at 6 months. Ultra-low-temperature cryoablation was performed in 64 patients (age 67 ± 11 years, 78% ischaemic, ejection fraction = 35 ± 10%) at 9 centres. The primary acute effectiveness endpoint was achieved in 94% (51/54) of patients in whom post-ablation induction was attempted. There were no protocol-defined MAEs; four procedure-related serious adverse events resolved without clinical sequelae. At 6-month follow-up, 38 patients (60.3%) remained VT-free, and freedom from defibrillator shock was 81.0%, with no significant difference between ischaemic and non-ischaemic cohorts. In 47 patients with defibrillator for at least 6 months prior to the ablation, the VT burden was reduced from median of 4, inter-quartile range (IQR, 1-9) to 0, IQR (0-2).

CONCLUSION

In this first-in-human multi-centre experience, endocardial ULTC ablation of monomorphic VT appears safe and effective in patients with both ischaemic-cardiomyopathy and non-ischaemic-cardiomyopathy.

CLINICAL TRIAL REGISTRATION

NCT04893317.

Epicardial ablation of ventricular tachycardia in ischemic cardiomyopathy: A review and local experience

Myocardial scar in ischemic cardiomyopathy is predominantly endocardial, however, between 5% and 15% of these patients have an arrhythmogenic epicardial substrate. Percutaneous epicardial ablation should be considered in patients with ICM and VT especially if they failed an endocardial ablation. Simultaneous epicardial and endocardial ablation of VT in ICM may reduce short- and medium-term VT recurrence compared with an endocardial only approach. Cardiac imaging could be used to help guide patient selection for a combined epi-endo approach. Complications related to epicardial access can happen in up to 7% of patients. Epicardial ablation in these patients should be referred to experienced tertiary centers. We review the literature and share interesting cases.

Area-weighted unipolar voltage to predict heart failure outcomes in patients with ischaemic cardiomyopathy and ventricular tachycardia

AIMS

Patients with ischaemic cardiomyopathy (ICM) referred for catheter ablation of ventricular tachycardia (VT) are at risk for end-stage heart failure (HF) due to adverse remodelling. Local unipolar voltages (UV) decrease with loss of viable myocardium. A UV parameter reflecting global viable myocardium may predict prognosis. We evaluate if a newly proposed parameter, area-weighted unipolar voltage (awUV), can predict HF-related outcomes [HFO; HF death/left ventricular (LV) assist device/heart transplant] in ICM.

METHODS AND RESULTS

From endocardial voltage maps of consecutive patients with ICM referred for VT ablation, awUV was calculated by weighted interpolation of local UV. Associations between clinical and mapping parameters and HFO were evaluated and validated in a second cohort. The derivation cohort consisted of 90 patients [age 68 ±8 years; LV ejection fraction (LVEF) 35% interquartile range (IQR) (24-40)] and validation cohort of 60 patients [age 67 ± 9, LVEF 39% IQR (29-45)]. In the derivation cohort, during a median follow-up of 45 months [IQR (34-83)], 36 (43%) patients died and 23 (26%) had HFO. Patients with HFO had lower awUV [4.51 IQR (3.69-5.31) vs. 7.03 IQR (6.08-9.2), P < 0.001]. A reduction in awUV [optimal awUV (5.58) cut-off determined by receiver operating characteristics analysis] was a strong predictor of HFO (3-year HFO survival 97% vs. 57%). The cut-off value was confirmed in the validation cohort (2-year HFO-free survival 96% vs. 60%).

CONCLUSION

The newly proposed parameter awUV, easily available from routine voltage mapping, may be useful at identifying ICM patients at high risk for HFO.

Epicardial Ventricular Tachycardia Ablation: Patient Selection, Access, and Ablation Techniques and Strategies to Manage Complications

Epicardial ventricular tachycardia ablation is an important treatment modality for refractory ventricular tachycardia. This comprehensive review guides clinicians through optimized strategies for improved procedural outcomes and patient safety during epicardial ventricular tachycardia ablation. Patient selection criteria, including cardiomyopathy type, electrocardiogram findings, and prior ablation history, are discussed. Detailed techniques for safe pericardial access are provided. Potential complications and strategies for prevention and management are explored. The review also addresses challenges and pitfalls of epicardial mapping and ablation.

Characteristics of the phenotype of mixed cardiomyopathy in patients with implantable cardioverter-defibrillators

BACKGROUND OR PURPOSE

The prognosis of m ixed cardiomyopathy (CMP) in patients with implanted cardioverter-defibrillators (ICDs) has not been investigated. We aim to study the demographic, clinical, device therapies and survival characteristics of mixed CMP in a cohort of patients implanted with a defibrillator.

METHODS

The term mixed CMP was used to categorise patients with impaired left ventricular ejection fraction attributed to documented non-ischemic triggers with concomitant moderate coronary artery disease. This is a single center observational cohort of 526 patients with a mean follow-up of 8.7 ± 3.5 years.

RESULTS

There were 42.5% patients with ischemic cardiomyopathy (ICM), 26.9% with non-ischemic cardiomyopathy (NICM) and 30.6% with mixed CMP. Mixed CMP, compared to NICM, was associated with higher mean age (69.1 ± 9.6 years), atrial fibrillation (55.3%) and greater incidence of comorbidities. The proportion of patients with mixed CMP receiving device shocks was 23.6%, compared to 18.4% in NICM and 27% in ICM. The VT cycle length recorded in mixed CMP (281.6 ± 43.1 ms) was comparable with ICM (282.5 ± 44 ms; p = 0.9) and lesser than NICM (297.7 ± 48.7 ms; p = 0.1). All-cause mortality in mixed CMP (21.1%) was similar to ICM (20.1%; p = 0.8) and higher than NICM (15.6%; p = 0.2). The Kaplan-Meier curves revealed hazards of 1.57 (95% CI: 0.91, 2.68) for mixed CMP compared to NICM.

CONCLUSION

In a cohort of patients with ICD, the group with mixed CMP represents a phenotype predominantly comprised of the elderly with a higher incidence of comorbidities. Mixed CMP resembles ICM in terms of number of device shocks and VT cycle length. Trends of long-term prognosis of patients with mixed CMP are worse than NICM and similar to ICM.

Mapping and Ablation of Ventricular Tachycardia in Inherited Left Ventricular Cardiomyopathies

Advances in the field of human genetics have led to an accumulating understanding of the genetic basis of distinct nonischemic cardiomyopathies associated with ventricular tachycardias (VTs) and sudden cardiac death. To date, there is an increasing proportion of patients with inherited cardiomyopathies requiring catheter ablation for VTs. This review provides an overview of disease-causing gene mutations frequently encountered and relevant for clinical electrophysiologists. Available data on VT ablation in patients with an inherited etiology and a phenotype of a nondilated left ventricular cardiomyopathy, dilated cardiomyopathy, or hypertrophic cardiomyopathy are summarized. VTs amenable to catheter ablation are related to nonischemic fibrosis. Recent insights into genotype-phenotype relations of subtype and location of fibrosis have important implications for treatment planning. Current strategies to delineate nonischemic fibrosis and related arrhythmogenic substrates using multimodal imaging, image integration, and electroanatomical mapping are provided. The ablation approach depends on substrate location and extension. Related procedural aspects including patient-tailored (enhanced) ablation strategies and outcomes are outlined. Challenging substrates for VT and the underlying inherited etiologies with a high risk for rapid progressive heart failure contribute to poor outcomes after catheter ablation. Electroanatomical data obtained during ablation may allow the identification of patients at particular risk who need to be considered for early work-up for left ventricular assist device implantation or heart transplantation.

Correlation of myocardial strain by CMR-feature tracking with substrate abnormalities detected by electro-anatomical mapping in patients with nonischemic cardiomyopathy

BACKGROUND

Late gadolinium enhancement (LGE) detected by cardiac MRI (CMR) has low correlation with low voltage zones (LVZs) detected by electroanatomical mapping (EAM). We aim to study correlation of myocardial strain by CMR- Feature Tracking (FT) alongside LGE with LVZs detected by EAM.

METHODS

Nineteen consecutive CMRs of patients with EAM were analyzed offline by CMR-FT. Peak value of circumferential strain (CS), longitudinal strain (LS), and LGE was measured in each segment of the left ventricle (17-segment model). The percentage of myocardial segments with CS and LS > -17% was determined. Percentage area of LGE-scar was calculated. Global and segment-wise bipolar and unipolar voltage was collected. Percentage area of bipolar LVZ (<1.5 mV) and unipolar LVZ (<8.3 mV) was calculated.

RESULTS

Mean age was 62±11 years. Mean LVEF was 37±13%. Mean global CS was -11.8±5%. Mean global LS was -11.2±4%. LGE-scar was noted in 74% of the patients. Mean percentage area of LGE-scar was 5%. There was significant correlation between percentage abnormality detected by LS with percentage bipolar LVZ (r = +0.5, p = 0.03) and combined percentage CS+LS abnormality with percentage unipolar LVZ (r = +0.5, p = 0.02). Per-unit increase in CS increased the percentage area of unipolar LVZ by 2.09 (p = 0.07) and per-unit increase in LS increased the percentage area of unipolar LVZ by 2.49 (p = 0.06). The concordance rates between CS and LS to localize segments with bipolar/unipolar LVZ were 79% and 95% compared to 63% with LGE.

CONCLUSIONS

Myocardial strain detected by CMR-FT has a better correlation with electrical low voltage zones than the conventional LGE.

Electroanatomical voltage mapping with contact force sensing for diagnosis of arrhythmogenic right ventricular cardiomyopathy

BACKGROUND

Three-dimensional electroanatomical mapping (EAM) can be helpful to diagnose arrhythmogenic right ventricular cardiomyopathy (ARVC). Yet, previous studies utilizing EAM have not systematically used contact-force sensing catheters (CFSC) to characterize the substrate in ARVC, which is the current gold standard to assure adequate tissue contact.

OBJECTIVE

To investigate reference values for endocardial right ventricular (RV) EAM as well as substrate characterization in patients with ARVC by using CFSC.

METHODS

Endocardial RV EAM during sinus rhythm was performed with CFSC in 12 patients with definite ARVC and 5 matched controls without structural heart disease. A subanalysis for the RV outflow tract (RVOT), septum, free-wall, subtricuspid region, and apex was performed. Endocardial bipolar and unipolar voltage amplitudes (BVA, UVA), signal characteristics and duration as well as the impact of catheter orientation on endocardial signals were also investigated.

RESULTS

ARVC patients showed lower BVA vs. controls (p = 0.018), particularly in the subtricuspid region (1.4, IQR:0.5-3.1 vs. 3.8, IQR:2.5-5 mV, p = 0.037) and RV apex (2.5, IQR:1.5-4 vs. 4.3,IQR:2.9-6.1 mV, p = 0.019). BVA in all RV regions yielded a high sensitivity and specificity for ARVC diagnosis (AUC 59-78%, p < 0.05 for all), with the highest performance for the subtricuspid region (AUC 78%, 95% CI:0.75-0.81, p < 0.001, negative predictive value 100%). A positive correlation between BVA and an orthogonal catheter orientation (46°-90°:r = 0.106, p < 0.001), and a negative correlation between BVA and EGM duration (r = -0.370, p < 0.001) was found.

CONCLUSIONS

EAM using CFSC validates previous bipolar cut-off values for normal endocardial RV voltage amplitudes. RV voltages are generally lower in ARVC as compared to controls, with the subtricuspid area being commonly affected and having the highest discriminatory power to differentiate between ARVC and healthy controls. Therefore, EAM using CFSC constitutes a promising tool for diagnosis of ARVC.

Advancing clinical translation of cardiac biomechanics models: a comprehensive review, applications and future pathways

Cardiac mechanics models are developed to represent a high level of detail, including refined anatomies, accurate cell mechanics models, and platforms to link microscale physiology to whole-organ function. However, cardiac biomechanics models still have limited clinical translation. In this review, we provide a picture of cardiac mechanics models, focusing on their clinical translation. We review the main experimental and clinical data used in cardiac models, as well as the steps followed in the literature to generate anatomical meshes ready for simulations. We describe the main models in active and passive mechanics and the different lumped parameter models to represent the circulatory system. Lastly, we provide a summary of the state-of-the-art in terms of ventricular, atrial, and four-chamber cardiac biomechanics models. We discuss the steps that may facilitate clinical translation of the biomechanics models we describe. A well-established software to simulate cardiac biomechanics is lacking, with all available platforms involving different levels of documentation, learning curves, accessibility, and cost. Furthermore, there is no regulatory framework that clearly outlines the verification and validation requirements a model has to satisfy in order to be reliably used in applications. Finally, better integration with increasingly rich clinical and/or experimental datasets as well as machine learning techniques to reduce computational costs might increase model reliability at feasible resources. Cardiac biomechanics models provide excellent opportunities to be integrated into clinical workflows, but more refinement and careful validation against clinical data are needed to improve their credibility. In addition, in each context of use, model complexity must be balanced with the associated high computational cost of running these models.

Catheter ablation of ventricular tachycardia: strategies to improve outcomes

Catheter ablation of ventricular arrhythmias has evolved considerably since it was first described more than 3 decades ago. Advancements in understanding the underlying substrate, utilizing pre-procedural imaging, and evolving ablation techniques have improved the outcomes of catheter ablation. Ensuring safety and efficacy during catheter ablation requires adequate planning, including analysis of the 12 lead ECG and appropriate pre-procedural imaging. Defining the underlying arrhythmogenic substrate and disease eitology allow for the developed of tailored ablation strategies, especially for patients with non-ischemic cardiomyopathies. During ablation, the type of anesthesia can affect VT induction, the quality of the electro-anatomic map, and the stability of the catheter during ablation. For high risk patients, appropriate selection of hemodynamic support can increase the success of VT ablation. For patients in whom VT is hemodynamically unstable or difficult to induce, substrate modification strategies can aid in safe and successful ablation. Recently, there has been an several advancements in substrate mapping strategies that can be used to identify and differentiate local late potentials. The incorporation of high-definition mapping and contact-sense technologies have both had incremental benefits on the success of ablation procedures. It is crucial to harness newer technology and ablation strategies with the highest level of peri-procedural safety to achieve optimal long-term outcomes in patients undergoing VT ablation.

Unipolar-voltage-based evaluation of left atrial tissue properties and ablation outcome in patients with atrial fibrillation

AIMS

The relationship between local unipolar voltage (UV) in the pulmonary vein (PV)-ostia and left atrial wall thickness (LAWT) and the utility of these parameters as indices of outcome after atrial fibrillation (AF) ablation remain unclear.

METHODS AND RESULTS

Two-hundred seventy-two AF patients who underwent AF ablation were enrolled. Unipolar voltage of PV-ostia was measured using a CARTO system, and LAWT was measured using computed tomography. The primary endpoint was atrial tachyarrhythmia (ATA) recurrence including AF. The ATA recurrence was documented in 74 patients (ATA-Rec group). The UV and LAWT of the bilateral superior PV roof to posterior and around the right-inferior PV in the ATA-Rec group were significantly greater than in patients without ATA recurrence (ATA-Free group) (P < 0.001). The UV had a strong positive correlation with LAWT (R2 = 0.446, P < 0.001). The UV 2.7 mV and the corresponding LAWT 1.6 mm were determined as the cut-off values for ATA recurrence (P < 0.001, respectively). Multisite LA high UV (HUV, ≥4 areas of >2.7 mV) or multisite LA wall thickening (≥5 areas of >1.6 mm), defined as LA hypertrophy (LAH), was related to higher ATA recurrence. Among 92 LAH patients, 66 had HUV (LAH-HUV) and the remaining 26 had low UV (LAH-LUV), characterized by history of non-paroxysmal AF and heart failure, reduced LV ejection fraction, or enlarged LA. In addition, LAH-LUV showed the worst ablation outcome, followed by LAH-HUV and No LAH (log-rank P < 0.001).

CONCLUSION

Combining UV and LAWT enables us to stratify recurrence risk and suggest a tailored ablation strategy according to LA tissue properties.

Association between residual unipolar voltage and arrhythmia recurrence after left atrial posterior wall isolation for persistent atrial fibrillation

INTRODUCTION

Posterior wall isolation (PWI) combined with pulmonary vein isolation (PVI) has proven effective for persistent atrial fibrillation (AF). However, when performing PWI, creating transmural lesions with subendocardial ablation is sometimes difficult. Endocardial unipolar voltage amplitude had a higher sensitivity than bipolar voltage mapping for identifying intramural viable myocardium in the atria. In this study, we aimed to retrospectively investigate the correlation between the residual potential in the posterior wall (PW) following PWI for persistent AF and atrial arrhythmia recurrence using endocardial unipolar voltage.

METHODS

This was a single-center observational study. Patients who underwent PVI and PWI for persistent AF in the first procedure between March 2018 and December 2021 at the Tokyo Metropolitan Hiroo Hospital were included in this study. The patients were divided into two groups based on the presence of residual unipolar PW potentials after PWI with a cutoff of 1.08 mV and the recurrence of atrial arrhythmias was compared.

RESULTS

In total, 109 patients were included in the analysis. Forty-three patients had residual unipolar potentials after PWI and 66 patients had no residual unipolar potentials. The atrial arrhythmia recurrence rate was significantly higher in the group with residual unipolar potential (41.8% vs. 17.9%, p = 0.003). The residual unipolar potential was an independent predictor of recurrence (odds ratio: 4.53; confidence interval: 1.67-12.3, p = 0.003).

CONCLUSION

Residual unipolar potential after PWI for persistent AF is associated with recurrent atrial arrhythmias.

Mitral Annular Substrate and Ventricular Arrhythmias in Arrhythmogenic Mitral Valve Prolapse With Mitral Annular Disjunction

BACKGROUND

In patients with bileaflet mitral valve prolapse (MVP), mitral annular disjunction (MAD) is associated with increased risk of sudden cardiac death via incompletely understood mechanisms.

OBJECTIVES

This study assessed the substrate for ventricular arrhythmias in patients with bileaflet MVP and MAD as well as outcomes of catheter ablation with an emphasis on sustained, monomorphic ventricular tachycardia (VT).

METHODS

A total of 18 consecutive patients (11 women, mean age 54 ± 15 years) with bileaflet MVP and MAD underwent catheter ablation for VT, and/or premature ventricular complexes (PVCs). Eight patients had a prior cardiac arrest.

RESULTS

PVCs were targeted for ablation in all 18 patients (symptomatic PVCs n = 15, PVC-induced ventricular fibrillation n = 3). Sustained monomorphic VT was targeted in 7 of 18 patients. Electroanatomic mapping showed low voltage in the area of the mitral annulus corresponding to VT target sites in 6 of 7 patients with sustained VT. Four of 7 patients had low voltage in the areas of MAD. Six of 7 patients with VT were rendered noninducible post-ablation. The PVC burden was reduced from 11.0% ± 10.4% to 4.0% ± 5.5% (P = 0.004). Over a mean follow-up of 33.9 ± 43.4 months, no VTs recurred. There were no major complications. No repeat ablations for VT occurred. Five of 18 patients required repeat ablation for PVCs.

CONCLUSIONS

In patients with bileaflet MVP and MAD undergoing catheter ablation, the mitral valve annulus often contains low-voltage areas harboring the substrate for monomorphic VT and PVCs. Ablation in these patients was safe and improved arrhythmia control.

Electroanatomic mapping in athletes: Why and when. An expert opinion paper from the Italian Society of Sports Cardiology

Three-dimensional electroanatomical mapping (EAM) has the potential to identify the pathological substrate underlying ventricular arrhythmias (VAs) in different clinical settings by detecting myocardial areas with abnormally low voltages, which reflect the presence of different cardiomyopathic substrates. In athletes, the added value of EAM may be to enhance the efficacy of third-level diagnostic tests and cardiac magnetic resonance (CMR) in detecting concealed arrhythmogenic cardiomyopathies. Additional benefits of EAM in the athlete include the potential impact on disease risk stratification and the consequent implications for eligibility to competitive sports. This opinion paper of the Italian Society of Sports Cardiology aims to guide general sports medicine physicians and cardiologists on the clinical decision when to eventually perform an EAM study in the athlete, highlighting strengths and weaknesses for each cardiovascular disease at risk of sudden cardiac death during sport. The importance of early (preclinical) diagnosis to prevent the negative effects of exercise on phenotypic expression, disease progression, and worsening of the arrhythmogenic substrate is also addressed.

Mortality after catheter ablation of structural heart disease related ventricular tachycardia

BACKGROUND

There is a paucity of data describing mortality after catheter ablation of ventricular tachycardia (VT).

OBJECTIVES

We describe the causes and predictors of cardiac transplant and/or mortality following catheter ablation of structural heart disease (SHD) related VT.

METHODS

Over 10-years, 175 SHD patients underwent VT ablation. Clinical characteristics, and outcomes, were compared between patients undergoing transplant and/or dying and those surviving.

RESULTS

During 2.8 (IQR 1.9-5.0) years follow-up, 37/175 (21%) patients underwent transplant and/or died following VT ablation. Prior to ablation, these patients were older (70.3 ± 11.1 vs. 62.1 ± 13.9 years, P = 0.001), had lower left ventricular ejection fraction ([LVEF] 30 ± 12% vs. 44 ± 14%, P < 0.001), and were more likely to have failed amiodarone (57% vs. 39%, P = 0.050), compared to those that survived. Predictors of transplant and/or mortality included LVEF≤35% (HR 4.71 [95% CI 2.18-10.18], P < 0.001), age ≥ 65 years (HR 2.18 [95% CI 1.01-4.73], P = 0.047), renal impairment (HR 3.73 [95% CI 1.80-7.74], P < 0.001), amiodarone failure (HR 2.67 [95% CI 1.27-5.63], P = 0.010) and malignancy (HR 3.09 [95% CI 1.03-9.26], P = 0.043). Ventricular arrhythmia free survival at 6-months was lower in the transplant and/or deceased, compared to non-deceased group (62% vs. 78%, P = 0.010), but was not independently associated with transplant and/or mortality. The risk score, MORTALITIES-VA, accurately predicted transplant and/or mortality (AUC: 0.872 [95% CI 0.810-0.934]).

CONCLUSIONS

Cardiac transplant and/or mortality after VT ablation occurred in 21% of patients. Independent predictors included LVEF≤35%, age ≥ 65 years, renal impairment, malignancy, and amiodarone failure. The MORTALITIES-VA score may identify patients at high-risk of transplant and/or dying after VT ablation.

Personalized Management of Sudden Death Risk in Primary Cardiomyopathies: From Clinical Evaluation and Multimodality Imaging to Ablation and Cardioverter-Defibrillator Implant

Sudden cardiac death represents the leading cause of death worldwide; although the majority of sudden deaths occur in an elderly population with coronary artery disease, some occur in young and otherwise healthy individuals, as is the case of cardiomyopathies. The aim of the present review is to provide a stepwise hierarchical approach for the global sudden death risk estimation in primary cardiomyopathies. Each individual risk factor is analyzed for its contribution to the overall risk of sudden death for each specific cardiomyopathy as well as across all primary myocardial diseases. This stepwise hierarchical and personalized approach starts from the clinical evaluation, subsequently passes through the role of electrocardiographic monitoring and multimodality imaging, and finally concludes with genetic evaluation and electro-anatomical mapping. In fact, the sudden cardiac death risk assessment in cardiomyopathies depends on a multiparametric approach. Moreover, current indications for ventricular arrhythmia ablation and defibrillator implantation are discussed.

Sinus Rhythm Electrocardiographic Abnormalities, Sites of Origin, and Ablation Outcomes of Ventricular Premature Depolarizations Initiating Ventricular Fibrillation

BACKGROUND

Ventricular fibrillation (VF) can be initiated by ventricular premature depolarizations (VPDs) in the absence of obvious structural abnormalities.

OBJECTIVE

To determine the prevalence of 12-lead ECG sinus rhythm reduced QRS amplitude, QRS fractionation (QRSf) and early repolarization (ER) pattern, and the outcome of catheter ablation and VPD anatomic distribution in patients with VPDs initiating VF.

METHODS

We compared a cohort with no apparent structural heart disease and VPDs initiating VF (Group 1, n=42) to a reference cohort (Group 2, n=61) of patients with no structural heart disease and symptomatic unifocal VPDs.

RESULTS

A reduced QRS amplitude (<.55 mV) in aVF (59 % vs 10%, p<0.001), QRSf in ≥2 contiguous leads (50% vs 16%, p<0.001) and early repolarization pattern (21.4% vs 1.6%, p=0.01) were more common in Group 1 vs Group 2. At least one abnormal ECG finding was present in 34 (81%) Group 1 vs 17 (28%) Group 2 patients, (p<0.001). VPD origin included RV and LV distal Purkinje system and moderator band/ papillary muscles, in 83% Group 1 vs 18% Group 2 patients, p<0.001. VF was eliminated with single ablation procedure in 77% of Group 1 patients with at least 2 years of follow-up.

CONCLUSIONS

A reduced QRS amplitude (<.55 mV) in aVF, QRS fractionation in ≥2 contiguous leads and/or an early repolarization pattern are frequently observed in patients with VPDs initiating VF. VPDs initiating VF typically originate from the distal Purkinje system and papillary muscles and can be successfully eliminated with catheter ablation.

Adverse Prognosis of Patients with Septal Substrate After VT Ablation Due to Electrical Storm

BACKGROUND

Data about ventricular tachycardia (VT) ablation in patients with electrical storm (ES) is limited.

OBJECTIVES

This study sought to compare the prognostic outcome of patients undergoing VT ablation after ES with and without a septal substrate.

METHODS

In this large single-center study, consecutive patients presenting with ES and undergoing VT ablation from June 2018 to April 2021 were included. Patients with septal substrate were compared with patients without septal substrate regarding endpoints of cardiovascular mortality, VT recurrences, recurrences of the clinical VT, and rehospitalization rates.

RESULTS

A total of 107 patients undergoing a first VT ablation because of electrical storm (ES) were included (age 65 ± 13 years, 86% male, 45% ischemic cardiomyopathy). Major complications occurred in 11% of all patients with increased postinterventional third-degree atrioventricular blocks among patients with septal substrate (9% vs 0%; P = 0.063). Partial ablation successes were similar (95% with a septal substrate vs 100% without a septal substrate; P = 0.251). Complete ablation success was achieved in 63% with a septal substrate and in 87% without a septal substrate (P = 0.004). After a median 22 months of follow-up, patients with septal substrate died significantly more often from cardiovascular causes (26% vs 7%; log-rank P = 0.018). In univariate analysis cardiovascular mortality for ES patients with septal substrate was 4.1-fold higher (HR: 4.192; CI: 1.194-14.719; P = 0.025). Independent predictors of adverse outcome in multivariable regression analysis were presence of septal substrate (HR: 5.723; P = 0.025) and increased age (HR: 1.104; P = 0.003). Recurrences of any ventricular arrhythmia (67% vs 56%; log rank P = 0.554) and rehospitalization rates (80% vs 66%; log rank P = 0.515) were similar between groups. Recurrences of clinical VT were similar (7% vs 2%; P = 0.252).

CONCLUSIONS

Presence of a septal substrate is associated with adverse long-term cardiovascular mortality in patients admitted for VT ablation after ES. Despite decreased acute ablation successes in these patients, VT recurrence rates were similar to those without a septal substrate during follow-up.

First clinical experience using a novel automated mapping algorithm for mapping of ventricular arrhythmias

A new automated vector-based mapping algorithm (AMA) for 3-dimensional (3D) mapping has been introduced. The aim of this study was to present our experience using AMA to recognize additional catheter ablation targets in patients with ventricular arrhythmias (VA). A total of 16 patients (ICM; ischemic cardiomyopathy, n = 6; NICM; non-ischemic cardiomyopathy n = 10) suffering from VA underwent catheter ablation. Following bipolar voltage mapping, AMA was utilized to reveal zones of decelerated conduction velocity vectors (CVV) and this information was superimposed onto the 3D reconstructions and compared with the presence of scar. Mapping time was 28.1 ± 10 min for the endocardial reconstruction of the left ventricle (LV) and 17 ± 5.4 min for the epicardium (n = 6 patients). The mean area of LV low voltage was 13.9 ± 15% (endocardial) and 11.9 ± 5.7% (epicardial). Decelerating CVV zones were revealed in all patients (mean conduction velocity threshold of 39.3 ± 13%). Sustained VA have been terminated through ablation and substrate modification was performed in all patients. Correlation between the presence of CVV deceleration zones and areas of abnormal low voltage from bipolar mapping was revealed in only 37.5% of patients, but there was good correlation between scar from unipolar voltage mapping and the presence of CCV deceleration zones (94%; p = 0.008). The novel AMA may improve the understanding of individual VA substrates due to the visualization of decelerated CVV zones and their correlation with abnormal low voltage predominantly from unipolar mapping.

A Prospective, Multicentre Randomised Controlled Trial Comparing Catheter Ablation Versus Antiarrhythmic Drugs in Patients With Structural Heart Disease Related Ventricular Tachycardia: The CAAD-VT Trial Protocol

IMPORTANCE

Randomised trials have shown that catheter ablation (CA) is superior to medical therapy for ventricular tachycardia (VT) largely in patients with ischaemic heart disease. Whether this translates to patients with all forms and stages of structural heart disease (SHD-e.g., non-ischaemic heart disease) is unclear. This trial will help clarify whether catheter ablation offers superior outcomes compared to medical therapy for VT in all patients with SHD.

OBJECTIVE

To determine in patients with SHD and spontaneous or inducible VT, if catheter ablation is more efficacious than medical therapy in control of VT during follow-up.

DESIGN

Randomised controlled trial including 162 patients, with an allocation ratio of 1:1, stratified by left ventricular ejection fraction (LVEF) and geographical region of site, with a median follow-up of 18-months and a minimum follow-up of 1 year.

SETTING

Multicentre study performed in centres across Australia.

PARTICIPANTS

Structural heart disease patients with sustained VT or inducible VT (n=162).

INTERVENTION

Early treatment, within 30 days of randomisation, with catheter ablation (intervention) or initial treatment with antiarrhythmic drugs only (control).

MAIN OUTCOMES, MEASURES, AND RESULTS

Primary endpoint will be a composite of recurrent VT, VT storm (≥3 VT episodes in 24 hrs or incessant VT), or death. Secondary outcomes will include each of the individual primary endpoints, VT burden (number of VT episodes in the 6 months preceding intervention compared to the 6 months after intervention), cardiovascular hospitalisation, mortality (including all-cause mortality, cardiac death, and non-cardiac death) and LVEF (assessed by transthoracic echocardiography from baseline to 6-, 12-, 24- and 36-months post intervention).

CONCLUSIONS AND RELEVANCE

The Catheter Ablation versus Anti-arrhythmic Drugs for Ventricular Tachycardia (CAAD-VT) trial will help determine whether catheter ablation is superior to antiarrhythmic drug therapy alone, in patients with SHD-related VT.

TRIAL REGISTRY

Australian New Zealand Clinical Trials Registry (ANZCTR) TRIAL REGISTRATION ID: ACTRN12620000045910 TRIAL REGISTRATION URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=377617&isReview=true.

Atrial Endocardial Unipolar Voltage Mapping for Detection of Viable Intramural Myocardium: A Proof-of-Concept Study

BACKGROUND

Endocardial bipolar voltage amplitude is largely derived from endocardial and subendocardial wall layers. This may result in situations of low bipolar voltage amplitude despite the presence of mid-myocardial including epicardial (ie, intramural-epicardial) viable myocardium. This study examined the utility of endocardial unipolar voltage mapping for detection of viable intramural-epicardial atrial myocardium.

METHODS

In 15 swine, an atrial intercaval ablation line with an intentional gap was created. Animals survived for 6 to 8 weeks before electroanatomical mapping followed by sacrifice. Gaps were determined by the presence of electrical conduction and classified based on the histopathologiclly layer(s) of viable myocardium into the following: (1) transmural, (2) endocardial, and (3) intramural-epicardial. Voltage data from healthy, scar, and gap points were exported into excel. The sensitivity and specificity of bipolar and unipolar voltage amplitude to detect intramural-epicardial gaps were compared using receiver operating characteristic analysis.

RESULTS

In 9 of 15 (60%) swine, a focal ablation gap was detected in the intercaval line, while in the remainder 6 of 15 (40%), the line was complete without gaps. Gaps were classified into transmural (n=3), endocardial (n=3), or intramural-epicardial (n=3). Intramural-epicardial gaps were characterized by very low bipolar voltage amplitude that was similar to areas with transmural scar (P=0.91). In comparison, unipolar voltage amplitude in intramural-epicardial gaps was significantly higher compared to transmural scar (P<0.001). Unipolar voltage amplitude had higher sensitivity (93% versus 14%, respectively) and similar specificity (95% versus 98%, respectively) to bipolar voltage for detection of intramural-epicardial gaps.

CONCLUSIONS

Atrial unipolar voltage mapping may be a useful technique for identifying viable intramural-epicardial myocardium in patients with endocardial scar.

Comparison of the arrhythmogenic substrate for ventricular tachycardia in patients with ischemic vs non-ischemic cardiomyopathy - insights from high-density, multi-electrode catheter mapping

PURPOSE

The purpose of this study was to compare the differences of arrhythmogenic substrate using high-density mapping in ventricular tachycardia (VT) patients with ischemic (ICM) vs non-ischemic cardiomyopathy (NICM).

METHODS

Data from patients presenting for VT ablation from December 2016 to December 2020 at Westmead Hospital were reviewed.

RESULTS

Sixty consecutive patients with structural heart disease (ICM 57%, NICM 43%, mean age 66 years) having catheter ablation of scar-related VT with pre-dominant left ventricular involvement were included. ICM was associated with larger proportion of dense scar area (bipolar; 19 [12-29]% vs 6 [3-10]%, P < 0.001, unipolar; 20 [12-32]% vs 11 [7-19]%, P = 0.01) compared with NICM. However, the scar ratio (unipolar dense scar [%]/bipolar dense scar [%]) was significantly higher in NICM patients (1.2 [0.8-1.7] vs 1.7 [1.3-2.3], P = 0.003). Larger scar area in ICM was paralleled by higher proportion of complex electrograms (6 [2-13] % vs 3 [1-5] %, P = 0.01), longer and wider voltage based conducting channels, higher incidence of late potential-based conducting channels, longer VT cycle-length (399 ± 80 ms vs 359 ± 68 ms, P = 0.04) and greater maximal stimulation-QRS interval among sites with good pace-map correlation (75 [51-99]ms vs 48 [31-73]ms, P = 0.02). Ventricular arrhythmia (VA) storm was more highly prevalent in ICM than NICM (50% vs 23%, P = 0.03). During the follow-up period, NICM had a significantly higher cumulative incidence for the VA recurrence than ICM (P = 0.03).

CONCLUSIONS

High-density multi-electrode catheter mapping of left ventricular arrhythmogenic substrate of NICM tends to show smaller dense scar area and higher scar ratio, compared with ICM, suggestive the extent of epicardial/intramural substrate, with paucity of substrate targets for ablation, which results in the worse outcomes with ablation.

Impact of sex on clinical, procedural characteristics and outcomes of catheter ablation for ventricular arrhythmias according to underlying heart disease

BACKGROUND

Women are under-represented in many key studies and trials examining outcomes of catheter ablation (CA) for ventricular arrhythmias (VA). We compared characteristics between men and women undergoing their first catheter ablation for VA at a single centre over 10 years.

METHODS

The clinical, procedural characteristics and outcomes of 287 consecutive patients (male = 182, female = 105), undergoing their first CA at our centre over 10 years were compared according to sex and underlying heart disease.

RESULTS

In the ablation population, women were younger, had fewer co-morbidities, were less likely to have ischemic cardiomyopathy (ICM) and VA storm and were more likely to have idiopathic VA and premature ventricular complexes as the indication for ablation (P < 0.05 for all). Amongst idiopathic and non-ischemic cardiomyopathy (NICM) subgroups, baseline characteristics were similar; amongst ICM, women were younger and had higher numbers of drug failure pre-ablation (P = 0.05). Women were similar to men in all procedural characteristics, acute procedural success and complications, regardless of underlying heart disease. At median follow-up of 666 days, VA-free survival, overall mortality and survival free of death or transplant were comparable in both groups. Sex was not a predictor of these outcomes, after accounting for clinical and procedural characteristics.

CONCLUSION

Women represented 36% of the real-world population at our centre referred for CA of VA. There are key differences in clinical features of women versus men referred for VA ablation. Despite these differences, VA ablation in women can be accomplished with similar success and complication rates to men, regardless of underlying heart disease.

Volume-Weighted Unipolar Voltage Predicts Heart Failure Mortality in Patients With Dilated Cardiomyopathy and Ventricular Arrhythmias

BACKGROUND

Patients with dilated cardiomyopathy (DCM) who are undergoing catheter ablation of ventricular arrhythmias (VAs) are at risk of rapidly progressive heart failure (HF). Endocardial voltages decrease with loss of viable myocardium. Global left ventricular (LV) voltage as a surrogate for the amount of remaining viable myocardium may predict prognosis.

OBJECTIVES

This study evaluated whether the newly proposed parameter volume-weighted (vw) unipolar voltage (UV) can predict HF-related adverse outcomes (HFOs), including death, heart transplantation, or ventricular assist device implantation, in DCM.

METHODS

In consecutive patients with DCM referred for VA ablation, vwUV was calculated by mathematically integrating UV over the left ventricle, divided by the endocardial LV surface area and wall thickness. Patients were followed for HFOs.

RESULTS

A total of 103 patients (57 ± 14 years of age; LV ejection fraction [LVEF], 39 ± 13%) were included. Median vwUV was 9.75 (IQR: 7.27-12.29). During a median follow-up of 24 months (IQR: 8-47 months), 25 patients (24%) died, and 16 had HFOs 7 months (IQR: 1-18 months) after ablation. Patients with HFOs had significantly lower LVEF (29% ± 10% vs 41% ± 12%), vw bipolar voltage (BV) (3.00 [IQR: 2.47-3.53] vs 5.00 [4.12-5.73]), and vwUV (5.94 [IQR: 5.28-6.55] vs 10.37 [IQR: 8.82-12.81]; all P < 0.001), than patients without HFOs. In Cox regression analysis and goodness-of-fit tests, vwUV was the strongest and independent predictor for HFOs (HR: 3.68; CI: 2.09-6.45; likelihood ratio chi-square, 33.05; P < 0.001).

CONCLUSIONS

The novel parameter vwUV, as a surrogate for the amount of viable myocardium, identifies patients with DCM with VA who are at high risk for HF progression and mortality.

Mechanisms of Ventricular Arrhythmias and Implications for Catheter Ablation

Ventricular arrhythmias present with a wide spectrum of clinical manifestations, from mildly symptomatic frequent premature ventricular contractions to life-threatening events. Pathophysiologically, idiopathic ventricular arrhythmias occur in the absence of structural heart disease or ion channelopathies. Ventricular arrhythmias in the context of structural heart disease are usually determined by scar-related reentry and are associated with increased mortality. Catheter ablation is safe and highly effective in treating ventricular arrhythmias. The proper characterization of the arrhythmogenic substrate is essential for accurate procedural planning. We provide an overview on the main mechanisms of ventricular arrhythmias and their implications for catheter ablation.