Endo-epicardial homogenization of the scar versus limited substrate ablation for the treatment of electrical storms in patients with ischemic cardiomyopathy

Catheter Ablation of Ventricular Tachycardia in Ischemic Heart Disease: What Is Known and New Perspectives

PURPOSE OF THE REVIEW

This review aims to evaluate current evidence regarding ventricular tachycardia ablation in patients with ischemic heart disease and explore novel approaches currently developing to improve procedural and long-term outcomes.

RECENT FINDINGS

Recently published trials (PARTITA, PAUSE-SCD, and SURVIVE-VT) have demonstrated the prognostic benefit of prophylactic ventricular tachycardia ablation compared to current clinical practice. Advanced cardiac imaging provides a valuable pre-procedural evaluation of the arrhythmogenic substrate, identifying ablation targets non-invasively. Advanced cardiac mapping techniques allow to better characterize arrhythmogenic substrate during ablation procedure. Emerging technologies like pulsed field ablation and ultra-low temperature cryoablation show promise in ventricular tachycardia ablation. Advancements in mapping techniques, ablation technologies, and pre-procedural cardiac imaging offer promise for improving ventricular tachycardia ablation outcomes in ischemic heart disease.

Efficacy of catheter ablation for ventricular tachycardia in ischemic cardiomyopathy patients without an ICD implantation

BACKGROUND

The implantable cardioverter-defibrillator (ICD) prevents sudden cardiac death in patients with ischemic cardiomyopathy (ICM). Catheter ablation has been shown to effectively reduce ventricular tachycardia (VT) recurrence, yet its efficacy in patients without an ICD implantation remains uncertain.

OBJECTIVE

We aimed to investigate the outcomes of ablation for VT in patients with ICM without a backup ICD.

METHODS

Patients with ICM who received ablation for VT without an ICD implantation were included in this study. Ablation was guided by either activation mapping or substrate mapping. Endocardial ablation was the primary strategy; epicardial access was considered when endocardial ablation failed. The primary end point was VT recurrence during follow-up; secondary end points included cardiovascular rehospitalization, all-cause mortality, and a composite of these events.

RESULTS

A total of 114 patients were included, with the mean age of 58.2 ± 11.1 years, 102 of whom (89.5%) were male. Twelve patients (10.5%) underwent endo-epicardial ablation, whereas the rest received endocardial ablation. With a median follow-up of 53.8 months (24.8-84.2 months), VT recurred in 45 patients (39.5%), and 6 patients (5.3%) died, including 2 sudden cardiac deaths. The recurrence rate of VT was significantly lower in patients undergoing endo-epicardial ablation than in those with endocardial ablation only (8.3% vs 43.1%; log-rank P = .032). After multivariate adjustment, epicardial ablation remained associated with a reduced risk of VT recurrence (hazard ratio, 0.14; 95% confidential interval, 0.02-0.98; P = .048).

CONCLUSION

Patients with ICM undergoing VT ablation without a backup ICD experienced a notably low rate of arrhythmic death. Most recurrences proved nonlethal.

Ventricular Tachycardia Ablation Endpoints: Moving Beyond Noninducibility

In patients with structural heart disease and ventricular tachycardia (VT) undergoing catheter ablation, the response to programmed electrical stimulation (PES) at the end of the procedure has been traditionally used to evaluate the acute success and predict long-term outcomes. Although noninducibility at PES has been extensively investigated and validated in clinical trials and large multicenter registries, its performance in predicting long-term freedom from VT is suboptimal. In addition, PES has inherent limitations related to the influence of background antiarrhythmic drug therapy, periprocedural use of anesthesia, and the heterogeneity in PES protocols. The increased utilization of substrate-based ablation approaches that focus on ablation of abnormal electrograms identified with mapping in sinus or paced rhythm has been paralleled by a need for additional procedural endpoints beyond VT noninducibility at PES. This article critically appraises the relative merits and limitations of different procedural endpoints according to different ablation techniques for catheter ablation of scar-related VT.

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.

Feasibility of carbon dioxide insufflation and impact on epicardial approach utilization for ventricular tachycardia ablation in a midvolume referral center

BACKGROUND

Epicardial access is often crucial for successful ventricular tachycardia (VT) ablation, but it is often burdened by significant procedural risk. Intentional coronary vein exit and intrapericardial CO2 insufflation (EpiCO2) can facilitate subxiphoid pericardial access.

OBJECTIVE

This prospective study aimed to assess procedural feasibility, safety, and impact of the introduction of intrapericardial CO2 insufflation for epicardial access in a referral center for VT ablation.

METHODS

All consecutive patients treated with epicardial VT ablation between November 2022 and January 2024 with the EpiCO2 technique at Pisa University Hospital were prospectively enrolled and compared in terms of feasibility, efficiency, and safety with a local retrospective cohort of patients treated with subxiphoid dry puncture between July 2018 and October 2022.

RESULTS

Twenty-two consecutive patients (90.9% male; mean age, 54.3 years) underwent VT ablation with EpiCO2 during the study period. Epicardial access was achieved in all patients; median time from coronary sinus (CS) cannulation to epicardial access was 33 minutes. Intentional vein exit was successful in all cases, whereas CO2 insufflation was not feasible in 1 patient. There were no major complications and no significant bleeding. Since EpiCO2 introduction, epicardial approach utilization increased from 17.8% to 40% of all VT procedures. Comparison with 20 standard dry approach epicardial ablations showed no significant differences in terms of total procedural duration (322.5 [interquartile range, 296.75-363.75] minutes vs 359 [interquartile range, 323-409] minutes; P = .08).

CONCLUSION

In our single-center experience, EpiCO2 was feasible and safe and led to significant increase in procedural volume without affecting total procedural time compared with standard dry puncture.

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.

Ventricular Tachycardia Catheter Ablation: Retrospective Analysis and Prospective Outlooks-A Comprehensive Review

Ventricular tachycardia is a potentially life-threatening arrhythmia associated with an overall high morbi-mortality, particularly in patients with structural heart disease. Despite their pivotal role in preventing sudden cardiac death, implantable cardioverter-defibrillators, although a guideline-based class I recommendation, are unable to prevent arrhythmic episodes and significantly alter the quality of life by delivering recurrent therapies. From open-heart surgical ablation to the currently widely used percutaneous approach, catheter ablation is a safe and effective procedure able to target the responsible re-entry myocardial circuit from both the endocardium and the epicardium. There are four main mapping strategies, activation, entrainment, pace, and substrate mapping, each of them with their own advantages and limitations. The contemporary guideline-based recommendations for VT ablation primarily apply to patients experiencing antiarrhythmic drug ineffectiveness or those intolerant to the pharmacological treatment. Although highly effective in most cases of scar-related VTs, the traditional approach may sometimes be insufficient, especially in patients with nonischemic cardiomyopathies, where circuits may be unmappable using the classic techniques. Alternative methods have been proposed, such as stereotactic arrhythmia radioablation or radiotherapy ablation, surgical ablation, needle ablation, transarterial coronary ethanol ablation, and retrograde coronary venous ethanol ablation, with promising results. Further studies are needed in order to prove the overall efficacy of these methods in comparison to standard radiofrequency delivery. Nevertheless, as the field of cardiac electrophysiology continues to evolve, it is important to acknowledge the role of artificial intelligence in both the pre-procedural planning and the intervention itself.

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.

Ablation targets of scar-related ventricular tachycardia identified by dynamic functional substrate mapping

BACKGROUND

Dynamic functional substrate mapping of scar-related ventricular tachycardia offers better identification of ablation targets with limited ablation lesions. Several functional substrate mapping approaches have been proposed, including decrement-evoked potential (DEEP) mapping. The aim of our study was to compare the short- and long-term efficacy of a DEEP-guided versus a fixed-substrate-guided strategy for the ablation of scar-related ventricular tachycardia (VT).

RESULTS

Forty consecutive patients presenting for ablation of scar-related VT were randomized to either DEEP-guided or substrate-guided ablation. Late potentials were tagged and ablated in the non-DEEP group, while those in the DEEP group were subjected to RV extrastimulation after a drive train. Only potentials showing significant delay were ablated. Patients were followed for a median duration of 12 months. Twenty patients were allocated to the DEEP group, while the other 20 were allocated to the non-DEEP group. Twelve patients (60%) in the DEEP group had ischemic cardiomyopathy versus 10 patients (50%) in the non-DEEP group (P-value 0.525). Intraoperatively, the median percentage of points with LPs was 19% in the DEEP group and 20.6% in the non-DEEP group. The procedural time was longer in the DEEP group, approaching but missing statistical significance (P-value 0.059). VT non-inducibility was successfully accomplished in 16 patients (80%) in the DEEP group versus 17 patients (85%) in the non-DEEP group (P value 0.597). After a median follow-up duration of 12 months, the VT recurrence rate was 65% in both groups (P value 0.311), with a dropout rate of 10% in the DEEP group. As for the secondary endpoints, all-cause mortality rates were 20% and 25% in the DEEP and non-DEEP groups, respectively (P-value 0.342).

CONCLUSIONS

DEEP-assisted ablation of scar-related ventricular tachycardia is a feasible strategy with comparable short- and long-term outcomes to a fixed-substrate-based strategy with more specific ablation targets, albeit relatively longer but non-significant procedural times and higher procedural deaths. The imbalance between the study groups in terms of epicardial versus endocardial mapping, although non-significant, warrants the prudent interpretation of our results. Further large-scale randomized trials are recommended.

TRIAL REGISTRATION

clinicaltrials.gov, registration number: NCT05086510, registered on 28th September 2021, record https://classic.

CLINICALTRIALS

gov/ct2/show/NCT05086510.

Correlation Between Functional Substrate Mapping and Cardiac Computed Tomography-Derived Wall Thinning for Ventricular Tachycardia Ablation

BACKGROUND

Functional substrate mapping during baseline rhythm can identify arrhythmogenic tissue during ventricular tachycardia (VT) ablation. Wall thinning and wall thickness channels (WTCs) derived from computed tomography angiography have been shown to correlate with low voltage and VT isthmuses. The correlation between functional substrate mapping, wall thinning, and WTCs in patients with infarct- or non-infarct-related cardiomyopathies (ICM and NICM, respectively) has not been previously described.

OBJECTIVES

The purpose of this study was to correlate cardiac CTA-derived myocardial wall thinning with functional VT substrate mapping using isochronal late activation mapping.

METHODS

In 34 patients with ICM or NICM undergoing VT ablation who had a preprocedure computed tomography angiography, myocardial wall thinning was segmented in layers of 1 to 5 mm. Areas of wall thinning and WTCs were then spatially correlated with deceleration zones (DZs) from registered left ventricular endocardial isochronal late activation maps.

RESULTS

In 21 ICM patients and 13 NICM patients, ICM patients had greater surfaces areas of wall thinning (P < 0.001). In ICM patients, 94.1% of primary DZs were located on areas of wall thinning, compared to 20% of DZs in NICM patients overall but 50% if there was any wall thinning present. Fifty-nine percent of DZs in ICM patients and 56% of DZs in NICM patients were located near WTCs. The positive predictive value for WTC in localizing DZs was 22.5% and 37.8% in ICM and NICM patients, respectively.

CONCLUSIONS

Wall thinning is highly sensitive for functional substrate in ICM patients. WTCs had modest sensitivity for functional substrate but low positive predictive value for identifying DZs in ICM and NICM patients. These findings suggest that wall thinning may facilitate more efficient mapping in ICM patients, but WTCs are insufficient to localize wavefront discontinuities.

Venous Ethanol Ablation Approaches for Radiofrequency-Refractory Cardiac Arrhythmias

PURPOSE OF REVIEW

In this review, we summarize the procedural approach and outcomes of venous ethanol infusion in the treatment of ventricular arrhythmias with intramural site of origin.

RECENT FINDINGS

Coronary venous ethanol infusion has emerged as a novel, safe, and effective adjunctive strategy to radiofrequency ablation of drug refractory ventricular arrhythmias with an intramural origin. Radiofrequency catheter ablation is the first-line treatment for drug refractory ventricular arrythmias. Its success is highly dependent on the ability to reach targeted myocardium. Radiofrequency failures are common in patients with ventricular arrhythmias arising from deep intramural substrates, and those whose origin is in close proximity to vital structures such as coronary arteries or the phrenic nerve. Coronary venous ethanol infusion has emerged as a novel technique that circumvents these limitations.

Stereotactic arrhythmia radioablation: A novel therapy for cardiac arrhythmia

Cardiac arrhythmia is a global health problem, and catheter ablation has been one of its main treatments for decades. However, catheter ablation is an invasive method that cannot reach the deep myocardium, and it carries a considerable risk of side effects and recurrence. Therefore, it is necessary to explore a novel approach. Stereotactic body radiotherapy, which has been widely used in the field of radiation oncology, has recently expanded in the treatment of cardiac arrhythmia; when used in this context, it is known as stereotactic arrhythmia radioablation (STAR). As a noninvasive, effective, and well-tolerated treatment, STAR may be a suitable alternative method for patients with cardiac arrhythmia who are resistant or intolerant to catheter ablation. The main particles used to deliver energy in STAR are photons, protons, and carbon ions. Most studies have shown the short-term effectiveness of STAR, but problems such as a high long-term recurrence rate with a cumulative ventricular tachycardia-free survival rate from the published literature of 38.6% and related complications have also emerged. Therefore, in this article, we review the application of stereotactic body radiotherapy in cardiac arrhythmia, analyze its potential problems, and explore methods for improvement.

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.

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.

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.

Endocardial-Epicardial Catheter Ablation Versus Endocardial Catheter Ablation Alone for Ventricular Arrhythmia in Patients With Structural Heart Disease (Meta-Analysis of Reconstructed Time-to-Event Data)

Endocardial-epicardial (Endo-epi) catheter ablation (CA) has been shown to reduce the rate of ventricular arrhythmia (VA) ablation in patients with structural heart disease (SHD). However, the effectiveness of this technique compared with endocardial (Endo) CA alone remains uncertain. This meta-analysis aims to compare the effectiveness of Endo-epi versus Endo alone in reducing the risk of VA recurrence in patients with SHD. We searched PubMed, Embase, and Cochrane Central Register with a comprehensive strategy. We used reconstructed time-to-event data to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for VA recurrence accompanied by at least one Kaplan-Meier curve for ventricular tachycardia recurrence. Our meta-analysis included 11 studies with a total of 977 patients. Endo-epi had a significantly lower risk of VA recurrence compared with those treated with Endo alone (HR 0.43, 95% CI 0.32 to 0.57, p <0.001). Subgroup analysis based on the type of cardiomyopathy revealed that patients with arrhythmogenic right ventricular cardiomyopathy and ischemic cardiomyopathy (ICM) benefited significantly from Endo-epi in reducing the risk of VA recurrence (HR 0.835, 0.55 to 0.87, p <0.021). However, there was no significant difference with non-ICM (HR 0.440, 0.55 to 0.87, p <0.33). The analysis of conditional survival showed that patients who remained free of VA recurrence for 5 years after the procedure had a very low probability of developing VA recurrence thereafter. In conclusion, Endo-epi CA is more effective than Endo CA alone in reducing the risk of VA recurrence in patients with SHD, especially those with arrhythmogenic right ventricular cardiomyopathy and ICM.

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.

An approach to help differentiate postinfarct scar from borderzone tissue using Ripple Mapping during ventricular tachycardia ablation

BACKGROUND

Ventricular scar is traditionally highlighted on a bipolar voltage (BiVolt) map in areas of myocardium <0.50 mV. We describe an alternative approach using Ripple Mapping (RM) superimposed onto a BiVolt map to differentiate postinfarct scar from conducting borderzone (BZ) during ventricular tachycardia (VT) ablation.

METHODS

Fifteen consecutive patients (left ventricular ejection fraction 30 ± 7%) underwent endocardial left ventricle pentaray mapping (median 5148 points) and ablation targeting areas of late Ripple activation. BiVolt maps were studied offline at initial voltage of 0.50-0.50 mV to binarize the color display (red and purple). RMs were superimposed, and the BiVolt limits were sequentially reduced until only areas devoid of Ripple bars appeared red, defined as RM-scar. The surrounding area supporting conducting Ripple wavefronts in tissue <0.50 mV defined the RM-BZ.

RESULTS

RM-scar was significantly smaller than the traditional 0.50 mV cutoff (median 4% vs. 12% shell area, p < .001). 65 ± 16% of tissue <0.50 mV supported Ripple activation within the RM-BZ. The mean BiVolt threshold that differentiated RM-scar from BZ tissue was 0.22 ± 0.07 mV, though this ranged widely (from 0.12 to 0.35 mV). In this study, septal infarcts (7/15) were associated with more rapid VTs (282 vs. 347 ms, p = .001), and had a greater proportion of RM-BZ to RM-scar (median ratio 3.2 vs. 1.2, p = .013) with faster RM-BZ conduction speed (0.72 vs. 0.34 m/s, p = .001). Conversely, scars that supported hemodynamically stable sustained VT (6/15) were slower (367 ± 38 ms), had a smaller proportion of RM-BZ to RM-scar (median ratio 1.2 vs. 3.2, p = .059), and slower RM-BZ conduction speed (0.36 vs. 0.63 m/s, p = .036). RM guided ablation collocated within 66 ± 20% of RM-BZ, most concentrated around the RM-scar perimeter, with significant VT reduction (median 4.0 episodes preablation vs. 0 post, p < .001) at 11 ± 6 months follow-up.

CONCLUSION

Postinfarct scars appear significantly smaller than traditional 0.50 mV cut-offs suggest, with voltage thresholds unique to each patient.

Ripple mapping in ventricular tachycardia substrate mapping and ablation of nonischemic ventricular tachycardia

INTRODUCTION

Substrate-based ablation for ventricular tachycardia (VT) using Ripple map (RM) is an effective treatment strategy for patients with ischemic cardiomyopathy but has yet to be evaluated in patients with nonischemic cardiomyopathy (NICMO). The aim of this study is to determine the feasibility and effectiveness of an RM-based ablation for NICMO patients.

METHODS AND RESULTS

This was a single-center, retrospective study including all NICMO patients undergoing VT ablation at St Vincent Hospital between January 1, 2018 and January 12, 2019. Retrospective RM analysis was performed on those that had a substrate-based ablation to identify the location and number of Ripple channels as well as their proximity to ablation lesions. Thirty-three patients met the inclusion criteria and had a median age of 65 (58, 73.5) with 15.2% of the population being female, and were followed for a median duration of 451 (217.5, 586.5) days. Of these patients, 23 (69.7%) had a substrate-based ablation with a median procedural duration of 196.4 (186.8, 339) min, 1946 (517, 2750) points collected per map, and 277 (141, 554) points were within the scar. Two (8.6%) procedural complications occurred, and 7 (30.4%) patients had VT recurrence during follow-up. RM analysis revealed an average of two Ripple channels and the patients without VT recurrence had ablation performed closer to the Ripple channels: 0 (0, 4.7) versus 14.3 (0, 23.5) cm; p = .02.

CONCLUSION

An RM-based substrate ablation can be performed in NICMO patients and ablation within Ripple channels is a predictor of VT freedom.

Comparison of combined substrate-based mapping techniques to identify critical sites for ventricular tachycardia ablation

BACKGROUND

Established electroanatomic mapping techniques for substrate mapping for ventricular tachycardia (VT) ablation includes voltage mapping, isochronal late activation mapping (ILAM), and fractionation mapping. Omnipolar mapping (Abbott Medical, Inc.) is a novel optimized bipolar electrogram creation technique with integrated local conduction velocity annotation. The relative utilities of these mapping techniques are unknown.

OBJECTIVE

The purpose of this study was to evaluate the relative utility of various substrate mapping techniques for the identification of critical sites for VT ablation.

METHODS

Electroanatomic substrate maps were created and retrospectively analyzed in 27 patients in whom 33 VT critical sites were identified.

RESULTS

Both abnormal bipolar voltage and omnipolar voltage encompassed all critical sites and were observed over a median of 66 cm² (interquartile range [IQR] 41.3-86 cm²) and 52 cm² (IQR 37.7-65.5 cm²), respectively. ILAM deceleration zones were observed over a median of 9 cm² (IQR 5.0-11.1 cm²) and encompassed 22 critical sites (67%), while abnormal omnipolar conduction velocity (CV <1 mm/ms) was observed over 10 cm² (IQR 5.3-16.6 cm²) and identified 22 critical sites (67%), and fractionation mapping was observed over a median of 4 cm² (IQR 1.5-7.6 cm²) and encompassed 20 critical sites (61%). The mapping yield was the highest for fractionation + CV (2.1 critical sites/cm²) and least for bipolar voltage mapping (0.5 critical sites/cm²). CV identified 100% of critical sites in areas with a local point density of >50 points/cm².

CONCLUSION

ILAM, fractionation, and CV mapping each identified distinct critical sites and provided a smaller area of interest than did voltage mapping alone. The sensitivity of novel mapping modalities improved with greater local point density.

The value of functional substrate mapping in ventricular tachycardia ablation

In the setting of structural heart disease, ventricular tachycardia (VT) is typically associated with a re-entrant mechanism. In patients with hemodynamically tolerated VTs, activation and entrainment mapping remain the gold standard for the identification of the critical parts of the circuit. However, this is rarely accomplished, as most VTs are not hemodynamically tolerated to permit mapping during tachycardia. Other limitations include noninducibility of arrhythmia or nonsustained VT. This has led to the development of substrate mapping techniques during sinus rhythm, eliminating the need for prolonged periods of mapping during tachycardia. Recurrence rates following VT ablation are high; therefore, new mapping techniques for substrate characterization are required. Advances in catheter technology and especially multielectrode mapping of abnormal electrograms has increased the ability to identify the mechanism of scar-related VT. Several substrate-guided approaches have been developed to overcome this, including scar homogenization and late potential mapping. Dynamic substrate changes are mainly identified within regions of myocardial scar and can be identified as local abnormal ventricular activities. Furthermore, mapping strategies incorporating ventricular extrastimulation, including from different directions and coupling intervals, have been shown to increase the accuracy of substrate mapping. The implementation of extrastimulus substrate mapping and automated annotation require less extensive ablation and would make VT ablation procedures less cumbersome and accessible to more patients.

Management of patients with electrical storm: an educational review

Electrical storm (ES) is a medical emergency that is defined as ≥ 3 separate ventricular tachycardia (VT) episodes causing ICD therapy within 24 h. Patients with ES have high risk for hospitalization, heart failure (HF) decompensation, in-hospital death. Furthermore, it is associated with significant anxiety and distress for the patients. Frequent triggers of ES are myocardial ischaemia, acute decompensation of HF, metabolic and electrolyte disorders, drug side-effects, increased sympathetic tone. Acute management of ES requires sedation, antiarrhythmic drugs and correction of the precipitating factors; although, in severe refractory cases, intubation, mechanical ventilation, and circulatory support might be necessary. Radiofrequency catheter ablation is superior than antiarrhythmic drugs to suppress the ES and is also frequently required to terminate the ES, as well as to achieve acute and long-term freedom of VT. Optimization of the ICD programming is crucial to reduce the burden of further appropriate and inappropriate shocks. Use of appropriate discrimination criteria and algorithms, ATPs and extending the detection times are important measures to reduce the burden of ES. In patients with end-stage HF, ES can be a sign of failing heart and can be refractory of treatment. In such cases, deactivation of the ICD therapy should be considered and discussed with patients and their care givers.

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.

Long-term outcome of ventricular tachycardia ablation in patients who did not undergo programmed electrical stimulation after ablation

BACKGROUND

Ventricular arrhythmia inducibility is one of the ideal endpoints of ventricular tachycardia (VT) ablation. However, it may be challenging to implement programmed electrical stimulation (PES) at the end of the procedure under several circumstances. The long-term outcome of patients who did not undergo PES after VT ablation remains largely unknown.

PURPOSE

To investigate the details and long-term outcome of VT ablation in patients who did not undergo PES at the end of the ablation procedure.

METHODS

Among 183 VT ablation procedures in patients with structural heart disease who underwent VT ablation using an irrigated catheter, we enrolled those who did not undergo PES after VT ablation. VT ablation strategy involved targeting clinical VT plus pacemap-guided substrate ablation if inducible. When VT was not inducible, substrate-based ablation was performed. The primary endpoint was VT recurrence.

RESULTS

In 58 procedures, post-ablation VT inducibility was not assessed. The causes were non-inducibility of sustained VT before ablation (27/58, 46.6%), long procedure time (27.6%, mean 392 min), complications (10.3%), intolerant hemodynamic state (10.3%), and inaccessible or unsafe target (6.9%). With regard to the primary endpoint, 23 recurrences (39.7%) were observed during a mean follow-up period of 2.5 years. Patients with non-inducibility before ablation showed less VT recurrences (4/27, 14.8%) during follow-up than patients with other causes of untested PES after ablation (19/31, 61.2%) (Log-rank < 0.001).

CONCLUSIONS

VT recurrence was not observed in approximately 60% of the patients who did not undergo PES at the end of the ablation procedure. PES after VT ablation may be not needed among patients with pre-ablation non-inducibility.

Outcomes of a combined vs non-combined endo-epicardial ventricular tachycardia ablation strategy

BACKGROUND

Direct comparisons of combined (C-ABL) and non-combined (NC-ABL) endo-epicardial ventricular tachycardia (VT) ablation outcomes are scarce. We aimed to investigate the long-term clinical efficacy and safety of these 2 strategies in ischemic heart disease (IHD) and non-ischemic cardiomyopathy (NICM) populations.

METHODS

Multicentric observational registry included 316 consecutive patients who underwent catheter ablation for drug-resistant VT between January 2008 and July 2019. Primary and secondary efficacy endpoints were defined as VT-free survival and all-cause death after ablation. Safety outcomes were defined by 30-day mortality and procedure-related complications.

RESULTS

Most of the patients were male (85%), with IHD (67%) and mean age of 63 ± 13 years. During a mean follow-up of 3 ± 2 years, 117 (37%) patients had VT recurrence and 73 (23%) died. Multivariate survival analysis identified electrical storm (ES) at presentation, IHD, left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) functional class III / IV, and C-ABL as independent predictors of VT recurrence. In 135 patients undergoing repeated procedures, only C-ABL and ES were independent predictors of relapse. The identified independent predictors of mortality were C-ABL, ES, LVEF, age, and NYHA class III / IV. C-ABL survival benefit was only seen in patients with a previous ablation (P for interaction = 0.04). Mortality at 30 days was similar between NC-ABL and C-ABL (4% vs. 2%, respectively, P = 0.777), as was complication rate (10.3% vs. 15.1%, respectively, P = 0.336).

CONCLUSION

A combined or sequential endo-epicardial VT ablation strategy was associated with lower VT recurrence and lower all-cause death in IHD and NICM patients undergoing repeated procedures. Both approaches seemed equally safe.

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.

Biophysical Tissue Characterization of Ventricular Tachycardia Substrate With Local Impedance Mapping to Predict Critical Sites

BACKGROUND

New tools are needed to improve ventricular tachycardia (VT) substrate characterization and optimize outcomes. LI provides biophysical tissue characterization.

OBJECTIVES

The purpose of this study was to test local impedance (LI)-based mapping to predict critical ventricular tachycardia components after myocardial infarction (MI).

METHODS

One month after a nonreperfused anterior MI, endo-epicardial high-density electroanatomic mapping and endocardial LI mapping were performed in 23 Landrace Large X White pigs. LI thresholds were set using the blood pool value to define a 10 Ω range: low (<blood pool -1Ω), intermediate (≥blood pool -1Ω and ≤blood pool +9Ω), and high (normal) tissue resistance (>blood pool +9Ω).

RESULTS

Low LI was detected in low-voltage areas in 100% of cases, but intermediate LI was found in both core (87%) and border zone (12.5%) voltage areas. A total of 17 VTs were induced (VT isthmus identified in 9 animals). VT inducibility was associated with the size of intermediate LI area (OR: 1.19 [95% CI: 1.0-1.4]; P = 0.039) and the presence of specific LI patterns: LI corridor (OR: 15.0 [95% CI: 1.3-169.9]; P = 0.029); LI gradient (OR: 30.0 [95% CI: 2.1-421.1]; P = 0.012), high LI heterogeneity (OR: 21.7 [95% CI: 1.8-260.6]; P = 0.015), and presence of ≥2 low LI regions (OR: 11.3 [95% CI: 1.0-130.2]; P = 0.053). Potential VT isthmuses were in areas of intermediate LI and colocalized to LI patterns associated with VT inducibility in all cases (LI corridors or LI gradient). Low LI regions did not actively participate in the VT circuit (0%).

CONCLUSIONS

LI mapping is feasible and may add useful characterization of the VT substrate. Specific LI patterns (ie, corridors, gradients) were associated with VT inducibility and colocalized with the VT isthmus, thus representing a potential new target for ablation in substrate-based procedures.

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.

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.

Substrate Ablation by Multivein, Multiballoon Coronary Venous Ethanol for Refractory Ventricular Tachycardia in Structural Heart Disease

BACKGROUND

Ablation of ventricular tachycardia (VT) in the setting of structural heart disease often requires extensive substrate elimination that is not always achievable by endocardial radiofrequency ablation. Epicardial ablation is not always feasible. Case reports suggest that venous ethanol ablation (VEA) through a multiballoon, multivein approach can lead to effective substrate ablation, but large data sets are lacking.

METHODS

VEA was performed in 44 consecutive patients with ablation-refractory VT (ischemic, n=21; sarcoid, n=3; Chagas, n=2; idiopathic, n=18). Targeted veins were selected by mapping coronary veins on the epicardial aspect of endocardial scar (identified by bipolar voltage <1.5 mV), using venography and signal recording with a 2F octapolar catheter or by guidewire unipolar signals. Epicardial mapping was performed in 15 patients. Vein segments in the epicardial aspect of VT substrates were treated with double-balloon VEA by blocking flow with 1 balloon while injecting ethanol through the lumen of the second balloon, forcing (and restricting) ethanol between balloons. Multiple balloon deployments and multiple veins were used as needed. In 22 patients, late gadolinium enhancement cardiac magnetic resonance imaged the VEA scar and its evolution.

RESULTS

Median ethanol delivered was 8.75 (interquartile range, 4.5-13) mL. Injected veins included interventricular vein (6), diagonal (5), septal (12), lateral (16), posterolateral (7), and middle cardiac vein (8), covering the entire range of left ventricular locations. Multiple veins were targeted in 14 patients. Ablated areas were visualized intraprocedurally as increased echogenicity on intracardiac echocardiography and incorporated into 3-dimensional maps. After VEA, vein and epicardial ablation maps showed elimination of abnormal electrograms of the VT substrate. Intracardiac echocardiography demonstrated increased intramural echogenicity at the targeted region of the 3-dimensional maps. At 1 year of follow-up, median of 314 (interquartile range, 198-453) days of follow-up, VT recurrence occurred in 7 patients, for a success of 84.1%.

CONCLUSIONS

Multiballoon, multivein intramural ablation by VEA can provide effective substrate ablation in patients with ablation-refractory VT in the setting of structural heart disease over a broad range of left ventricular locations.

[Not Available]

OBJECTIVE

. To report the results of ventricular tachycardia (VT) catheter ablation in ischemic heart disease (IHD), and to identify risk factors associated with recurrence in a Mexican center.

MATERIALS AND METHODS

. We made a retrospective review of the cases of VT ablation performed in our center from 2015 to 2022. We analyzed the characteristics of the patients and those of the procedures separately and we determined factors associated with recurrence.

RESULTS

. Fifty procedures were performed in 38 patients (84% male; mean age 58.1 years). Acute success rate was 82%, with a 28% of recurrences. Female sex (OR 3.33, IC 95% 1.66-6.68, p=0.006), atrial fibrillation (OR 3.5, IC 95% 2.08-5.9, p=0.012), electrical storm (OR 2.4, IC 95% 1.06-5.41, p=0.045), functional class greater than II (OR 2.86, IC 95% 1.34-6.10, p=0.018) were risk factors for recurrence and the presence of clinical VT at the time of ablation (OR 0.29, IC 95% 0.12-0.70, p=0.004) and the use of more than 2 techniques for mapping (OR 0.64, IC 95% 0.48-0.86, p=0.013) were protective factors.

CONCLUSIONS

. Ablation of ventricular tachycardia in ischemic heart disease has had good results in our center. The recurrence is similar to that reported by other authors and there are some factors associated with it.

Acute and long-term success of ventricular tachycardia ablation in patients with ischemic heart disease in a Mexican center

Objective

. To report the results of ventricular tachycardia (VT) catheter ablation in ischemic heart disease (IHD), and to identify risk factors associated with recurrence in a Mexican center.

Materials and methods

. We made a retrospective review of the cases of VT ablation performed in our center from 2015 to 2022. We analyzed the characteristics of the patients and those of the procedures separately and we determined factors associated with recurrence.

Results

. Fifty procedures were performed in 38 patients (84% male; mean age 58.1 years). Acute success rate was 82%, with a 28% of recurrences. Female sex (OR 3.33, IC 95% 1.66-6.68, p=0.006), atrial fibrillation (OR 3.5, IC 95% 2.08-5.9, p=0.012), electrical storm (OR 2.4, IC 95% 1.06-5.41, p=0.045), functional class greater than II (OR 2.86, IC 95% 1.34-6.10, p=0.018) were risk factors for recurrence and the presence of clinical VT at the time of ablation (OR 0.29, IC 95% 0.12-0.70, p=0.004) and the use of more than 2 techniques for mapping (OR 0.64, IC 95% 0.48-0.86, p=0.013) were protective factors.

Conclusions

. Ablation of ventricular tachycardia in ischemic heart disease has had good results in our center. The recurrence is similar to that reported by other authors and there are some factors associated with it.

Ventricular Tachycardia Ablation Guided by Functional Substrate Mapping: Practices and Outcomes

Catheter ablation of ventricular tachycardia has demonstrated its important role in the treatment of ventricular tachycardia in patients with structural cardiomyopathy. Conventional mapping techniques used to define the critical isthmus, such as activation mapping and entrainment, are limited by the non-inducibility of the clinical tachycardia or its poor hemodynamic tolerance. To overcome these limitations, a voltage mapping strategy based on bipolar electrograms peak to peak analysis was developed, but a low specificity (30%) for VT isthmus has been described with this approach. Functional mapping strategy relies on the analysis of the characteristics of the electrograms but also their propagation patterns and their response to extra-stimulus or alternative pacing wavefronts to define the targets for ablation. With this review, we aim to summarize the different functional mapping strategies described to date to identify ventricular arrhythmic substrate in patients with structural heart disease.

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.

Evaluation of Saline-Enhanced Radiofrequency Needle-Tip Ablation for Ventricular Tachycardia (SERF VT CANADA Trial)

BACKGROUND

Endocardial catheter ablation for ventricular tachycardia (VT) may fail owing to the inability to deliver transmural lesions. Saline-enhanced radiofrequency (SERF) ablation uses a needle-tip catheter that is placed at varying depths into the myocardial tissue and heated saline solution is injected along with radiofrequency power (RF), creating fully transmural lesions. We report the first in-human SERF ablation for VT in Canada.

METHODS

Twenty-five patients with ischemic and nonischemic cardiomyopathy, with recurrent monomorphic drug-refractory VT who had failed a prior catheter ablation underwent SERF ablation in 3 different centres in Canada. After a voltage map, the mapping catheter was replaced with the needle-tipped ablation catheter, which was located perpendicular to the myocardium and extended either 6 or 8 mm into the tissue. Sterile saline solution was infused at a flow rate of 10 mL/min and at 60 °C, and 20-50 W RF was used.

RESULTS

Baseline left ventricular ejection fraction was 33.3 ± 8.6%, mean age was 69.5 ± 6.4 years; 92% were male. From 43 clinical VTs induced, 42 were ablated and 266 SERF lesions were delivered (10.6 ± 4.9 per patient). Of the 42 treated clinical VTs, 41 VTs (98%) were noninducible and 24 patients (96%) had their VT eliminated. At 6 months' follow-up, 42% of patients were free from VT and there was a 73% reduction in shocks.

CONCLUSIONS

SERF ablation is feasible and permits control of symptomatic monomorphic VT in drug-refractory patients with a prior failed ablation.

High Density Pace-Mapping for Scar-related Ventricular Tachycardia Ablation

Despite advances in medical and interventional therapies, ventricular tachycardia (VT) due to reentrant activity within complex regions of myocardial scar remains a common late complication of myocardial infarction This article is protected by copyright. All rights reserved.

Repolarization Heterogeneity in Human Post-Infarct Ventricular Tachycardia

BACKGROUND

Slow conduction, caused by fibrosis between surviving myocytes and connexin remodeling, is an important prerequisite for post-infarction ventricular tachycardia (VT); however, slow conduction is present throughout the infarct whereas VT circuits are finite in number and discrete. In a porcine model of VT, re-entrant circuits occur at region of significant repolarization heterogeneity caused by up-regulation of potassium channel β-subunits KCNE3 (increasing repolarization current) and KCNE4 (decreasing repolarization current), causing heterogeneous action potential durations.

OBJECTIVES

This study was designed to determine whether re-entrant circuits in human post-infarction VT are associated with repolarization heterogeneity.

METHODS

In 6 patients, left ventricular mapping was performed during induced VT to identify sites within the VT circuit. Subsequently, unipolar mapping (3.5-mm tip ablation catheter) was performed to characterize activation-recovery intervals (ARIs), which are surrogates for local action potential durations, at sites documented within the VT circuit isthmus (IN) compared to sites within the infarct scar but outside of the VT circuit (OUT).

RESULTS

ARIs were significantly shorter in the IN compared with the OUT sites (420.2 ± 79.3 ms vs 462 ± 52.8 ms; P = 0.01). In all patients. sites that were associated with the circuit always had shorter ARI values than did those sampled from OUT regions.

CONCLUSIONS

VT circuit sites in human post-infarct VT are associated with repolarization heterogeneity, similar to what was previously reported in a porcine model. This suggests the possibility of a common mechanism between humans and the porcine model of post-infarct VT, and that development of ablation strategies or small molecule or genetic therapies to restore normal repolarization kinetics may be antiarrhythmic.

The impact of ultra-high-density mapping on long-term outcome after catheter ablation of ventricular tachycardia

Ultra-high-density (UHD) mapping can improve scar area detection and fast activation mapping in patients undergoing catheter ablation of ventricular tachycardia (VT). The aim of the present study was to compare the outcome after VT ablation guided by UHD and conventional point-by-point 3D-mapping. The acute and long-term ablation outcome of 61 consecutive patients with UHD mapping (64-electrode mini-basket catheter) was compared to 61 consecutive patients with conventional point-by-point 3D-mapping using a 3.5 mm tip catheter. Patients, whose ablation was guided by UHD mapping had an improved 24-months outcome in comparison to patients with conventional mapping (cumulative incidence estimate of the combination of recurrence or disease-related death of 52.4% (95% confidence interval (CI) [36.9-65.7]; recurrence: n = 25; disease-related death: n = 4) versus 69.6% (95% CI [55.9-79.8]); recurrence: n = 31; disease-related death n = 11). In a cause-specific Cox proportional hazards model, UHD mapping (hazard ratio (HR) 0.623; 95% CI [0.390-0.995]; P = 0.048) and left ventricular ejection fraction > 30% (HR 0.485; 95% CI [0.290-0.813]; P = 0.006) were independently associated with lower rates of recurrence or disease-related death. Other procedural parameters were similar in both groups. In conclusion, UHD mapping during VT ablation was associated with fewer VT recurrences or disease-related deaths during long-term follow-up in comparison to conventional point-by-point mapping. Complication rates and other procedural parameters were similar in both groups.

Endocardial Scar-Homogenization With vs Without Epicardial Ablation in VT Patients With Ischemic Cardiomyopathy

OBJECTIVES

In this study, the authors investigated the ablation success of scar homogenization with combined (epicardial + endocardial) vs endocardial-only approach for ventricular tachycardia (VT) in patients with ischemic cardiomyopathy (ICM) at 5 years of follow-up.

BACKGROUND

Best ablation approach to achieve long-term success rate in VT patients with ICM is not known yet.

METHODS

Consecutive ICM patients undergoing VT ablation at our center were classified into group 1: endocardial + epicardial scar homogenization and group 2: endocardial scar homogenization. Patients with previous open heart surgery were excluded. Epicardial ablation was performed despite being noninducible after endocardial ablation in all group 1 patients. All patients underwent bipolar substrate mapping with standard scar settings defined as normal tissue >1.5 mV and severe scar <0.5 mV. Noninducibility of monomorphic VT was the procedural endpoint in both groups. Patients were followed up every 4 months for 5 years with implantable device interrogations.

RESULTS

A total of 361 patients (group 1: n = 70 and group 2: n = 291) were included in the study. At 5 years, 81.4% (n = 57/70) patients from group 1 and 66.3% (n = 193/291) from group 2 were arrhythmia-free (P = 0.01) Of those patients, 26 of 57 (45.6%) and 172 of 193 (89.1%) from group 1 and group 2 respectively were on anti-arrhythmic drugs (AAD) (log-rank P < 0.001). After adjusting for age, sex, and obstructive sleep apnea, endo-epicardial scar homogenization was associated with a significant reduction in arrhythmia-recurrence (HR: 0.48; 95% CI: 0.27-0.86; P = 0.02).

CONCLUSIONS

In this series of patients with ICM and VT, epicardial substrate was detected in all group 1 patients despite being noninducible after endocardial ablation. Moreover, combined endo-epicardial scar homogenization was associated with a significantly higher success rate at 5 years of follow-up and a substantially lower need for antiarrhythmic drugs after the procedure compared with the endocardial ablation alone.