Exploring postinfarction reentrant ventricular tachycardia with entrainment mapping

The Utility of Coronary Revascularization to Reduce Ventricular Arrhythmias in Coronary Artery Disease Patients: A Systematic Review

Ventricular arrhythmias (VA) are a major cause of morbidity and mortality in patients with coronary artery disease (CAD). Current guidelines recommend revascularization of significant CAD to improve survival in patients with ventricular fibrillation (VF), polymorphic ventricular tachycardia (VT), or those who are post-cardiac arrest. However, revascularization is not recommended for CAD patients with suspected scar-mediated monomorphic VT. There is a paucity of data detailing the utility of revascularization in reducing VA in CAD patients who do not present with acute coronary syndrome (ACS) and are not immediately post-cardiac arrest, which is the focus of this review. Medline, Scopus, and the Cochrane Central Register of Controlled Trials were systematically searched to identify relevant studies addressing this question. Studies that included patients presenting with ACS or those who were immediately post-cardiac arrest at the time of revascularization were excluded. In total, five studies comprising 2663 patients were reviewed.

Assessment of Intraprocedural Automated Arrhythmia Origin Localization System for Localizing Pacing Sites in 3D Space

BACKGROUND

The Automated Arrhythmia Origin Localization (AAOL) algorithm was developed for real-time prediction of early ventricular activation origins on a patient-specific electroanatomic (EAM) surface using a 3-lead electrocardiogram (AAOL-Surface). It has not been evaluated in 3-dimensional (3D) space (AAOL-3D), however, which may be important for predicting the arrhythmia origin from intramural or intracavity sites.

OBJECTIVES

This study sought to assess the accuracy of AAOL for localizing earliest ventricular activation in 3D space.

METHODS

This was a retrospective study of 3 datasets (BWH [Brigham and Women's Hospital], JHH [Johns Hopkins Hospital], and QEII [Queen Elizabeth II Health Sciences Centre]) involving 47 patients and 48 procedures, with an average of 19 ± 10 pacing sites each. In each patient, individual pacing sites were identified as target sites; the remaining pacing sites served as a training set (including QRS integrals from leads III, V2, and V6 with associated 3D coordinates). The AAOL-3D was then used to predict 3D coordinates of the pacing site. Localization error was assessed as the distance between known and predicted site coordinates, considering different EAM resolutions.

RESULTS

The AAOL-3D achieved a localization accuracy of 7.2 ± 3.1 mm, outperforming the AAOL-Surface (7.2 vs 7.8 mm; P < 0.05), with greater localization error for epicardial than endocardial pacing sites (8.7 vs 7.1 mm; P < 0.05). Cohort-specific analysis consistently favored AAOL-3D over AAOL-Surface in terms of accuracy. Exploration of AAOL-Surface accuracy across varying EAM resolutions showed optimal performance at the original and 75% resolution, with performance declining as resolution decreased.

CONCLUSIONS

The AAOL approach accurately identifies early ventricular activation origins in 3D and on EAM surfaces, potentially useful for identifying intramural arrhythmia origins.

Yield of Coronary Assessment in Sustained Monomorphic Ventricular Tachycardia

BACKGROUND

Coronary assessment is frequently conducted in patients with sustained monomorphic ventricular tachycardia (SMVT); however, its yield and subsequent treatment implications remain unclear. This study aimed to determine the prevalence of coronary artery disease (CAD) in patients presenting with SMVT, factors influencing clinician referral for coronary assessment, and clinical outcomes based on revascularisation or medical management of CAD.

METHOD

Consecutive patients presenting with acute SMVT requiring inpatient admission between 2017 and 2022 were identified.

RESULTS

A total of 249 individual patients with SMVT were identified, with 140 undergoing coronary assessment. Referral for coronary assessment was driven by chest pain (p<0.001) and increased troponin kinetics (p<0.001). No patient with SMVT had an acute coronary occlusion. Significant CAD was found in 48 (34%) patients, and traditional ischaemic features did not predict significant CAD. Nineteen (40%) patients with significant CAD underwent revascularisation (n=15 percutaneous coronary intervention, n=4 coronary artery bypass grafting). There was no significant difference in time to ventricular tachycardia (VT) recurrence between revascularised and medically managed CAD (hazard ratio 1.670; 95% confidence interval 0.756-3.687; p=0.199). A total of five of six patients who underwent a revascularisation-only strategy (no upfront antiarrhythmic therapy or ablation) had VT recurrence (median time to recurrence 8.9 months).

CONCLUSIONS

Despite being frequently performed, coronary assessment in SMVT has only modest yield, with no patients having an acute coronary occlusion. Traditional clinical factors of ischaemia did not improve this yield. Revascularisation alone did not improve freedom from VT.

Augmentation of Atrial Conduction Velocity With Pharmacological and Direct Electrical Sympathetic Stimulation

BACKGROUND

Atrial conduction velocity (CV) is influenced by autonomic tone and contributes to the pathophysiology of re-entrant arrhythmias and atrial fibrillation. Cardiac sympathetic nerve activation has been reported via electrical stimulation within the vertebral vein (VV).

OBJECTIVES

This study sought to characterize changes in right atrial (RA) CV associated with sympathetic stimulation from pharmacologic (isoproterenol) or direct electrical (VV stimulation) approaches.

METHODS

Subjects undergoing catheter ablation for atrial fibrillation had baseline RA electroanatomic maps performed in sinus rhythm (SR). RA mapping was repeated during right VV stimulation (20 Hz; up to 20 mA) and again with both RA pacing and during isoproterenol infusion, each titrated to the heart rate achieved with VV stimulation.

RESULTS

A total of 100 RA maps were analyzed from 25 subjects (mean age: 58 ± 14 years; 56% male), and CV was calculated from 51,534 electroanatomic map points. VV stimulation increased heart rate from baseline in all subjects (22.5 ± 5.5 beats/min). The average CV increased with VV stimulation (82.0 ± 34.5 cm/s) or isoproterenol (83.7 ± 35.0 cm/s) when compared to SR (70.8 ± 32.5 cm/s; P < 0.001). Heterogeneity of CV decreased with VV stimulation or isoproterenol when compared to SR (coefficient of variation: 0.33 ± 0.21 vs 0.35 ± 0.23 vs 0.57 ± 0.29; P < 0.001). There was no difference in CV or CV heterogeneity between SR and RA pacing, suggesting that these changes were independent of heart rate.

CONCLUSIONS

Global RA CV is enhanced, and heterogeneity of CV is reduced, with either pharmacologic or direct electrical sympathetic stimulation via the right VV.

Wavefront curvature analysis derived from preprocedural imaging can identify the critical isthmus in patients with postinfarcted ventricular tachycardia

BACKGROUND

Where activation wavefront curvature is convexly shaped, functional conduction block can occur.

OBJECTIVE

The purpose of this study was to determine whether left ventricular (LV) wall thickness determined from contrast-enhanced computed tomography (CT) is useful in localizing such areas in clinical postinfarction reentrant ventricular tachycardia (VT).

METHODS

We evaluated data from 6 patients who underwent catheter ablation for postinfarction VT. CT imaging with inHEART processing was conducted 1-3 days before electrophysiological (EP) study to determine LV wall thickness (T). Activation wavefront curvature was approximated as ΔT/T, where ΔT represents wall thickness change. During EP study, bipolar LV VT electrograms were acquired using a high-density mapping catheter, and activation times were determined. Maps of T, ΔT/T, and VT activation were subsequently compared using statistical analyses.

RESULTS

Two of 6 cases exhibited dual circuit morphologies, resulting in a total of 8 VT morphologies analyzed. The LV wall near the VT isthmus location tended to be thin, on the order of a few hundred micrometers. Regions of largest ΔT/T partially coincided with the lateral isthmus boundaries where electrical conduction block occurred during VT. ΔT/T at the boundaries, measured from imaging, was significantly larger compared to values at the isthmus midline and to the global LV mean value (P <.001).

CONCLUSION

Wavefront curvature measured by ΔT/T and caused by source-sink mismatch is dependent on ventricular wall thickness. Areas of high wavefront curvature partly coincide with and may be helpful in locating the VT isthmus in infarct border zones using preprocedural imaging analysis.

Optimal cardiac rhythm during substrate mapping in scar-related ventricular tachycardia: Significance of wavefront direction on identifying critical sites

BACKGROUND

A rotational activation pattern (RAP) around the localized line of a conduction block often correlates with sites specific to the critical zones of ventricular tachycardia (VT). The wavefront direction during substrate mapping affects manifestation of the RAP and line of block.

OBJECTIVE

The purpose of this study was to investigate the most optimal cardiac rhythm for identifying RAP and line of block in substrate mapping.

METHODS

We retrospectively evaluated 71 maps (median 3205 points/map) in 46 patients (65 ± 15 years; 33% with ischemic cardiomyopathy) who underwent high-density substrate mapping and ablation of scar-related VT. Appearance of a RAP during sinus, right ventricular (RV)-paced, left ventricular (LV)-paced, and biventricular-paced rhythms was investigated.

RESULTS

RAP was identified in 24 of 71 maps (34%) in the region where wavefronts from a single direction reached but not in the region where wavefronts from multiple directions centripetally collided. The probability of identifying the RAP depended on scar location; that is, anteroseptal and inferoseptal, inferior and apical, and basal lateral RAPs were likely to be identified during sinus/atrial, RV-paced, and LV-paced rhythms, respectively. In 13 patients, the RAP was not evident in the baseline map but became apparent during remapping in the other rhythm, in which the wavefront reached the site earlier within the entire activation time.

CONCLUSION

The optimal rhythm for substrate mapping depends on the spatial distribution of the area of interest. A paced rhythm with pacing sites near the scar may facilitate the identification of critical VT zones.

Scar-Related Monomorphic Ventricular Tachycardia After Treated Right Ventricular Metastatic Diffuse Large B-Cell Lymphoma

A patient with ventricular tachycardia (VT) and right ventricular (RV) metastatic diffuse large B-cell lymphoma had persistent RV gadolinium enhancement following chemotherapy and disease remission. Electrophysiology study demonstrated inducible sustained monomorphic VT requiring subcutaneous implantable cardioverter-defibrillator implantation. This highlights the arrhythmogenic potential of residual scar after resolution of cardiac masses.

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.

Role of activation signatures in re-entrant ventricular tachycardia circuits

INTRODUCTION

Development of a rapid means to verify the ventricular tachycardia (VT) isthmus location from heart surface electrogram recordings would be a helpful tool for the electrophysiologist.

METHOD

Myocardial infarction was induced in 22 canines by left anterior descending coronary artery ligation under general anesthesia. After 3-5 days, VT was inducible via programmed electrical stimulation at the anterior left ventricular epicardial surface. Bipolar VT electrograms were acquired from 196 to 312 recording sites using a multielectrode array. Electrograms were marked for activation time, and activation maps were constructed. The activation signal, or signature, is defined as the cumulative number of recording sites that have activated per millisecond, and it was utilized to segment each circuit into inner and outer circuit pathways, and as an estimate of best ablation lesion location to prevent VT.

RESULTS

VT circuit components were differentiable by activation signals as: inner pathway (mean: 0.30 sites activating/ms) and outer pathway (mean: 2.68 sites activating/ms). These variables were linearly related (p < .001). Activation signal characteristics were dependent in part upon the isthmus exit site. The inner circuit pathway determined by the activation signal overlapped and often extended beyond the activation map isthmus location for each circuit. The best lesion location estimated by the activation signal would likely block an electrical impulse traveling through the isthmus, to prevent VT in all circuits.

CONCLUSIONS

The activation signal algorithm, simple to implement for real-time computer display, approximates the VT isthmus location and shape as determined from activation marking, and best ablation lesion location to prevent reinduction.

Optimal Annotation of Local Activation Time in Ventricular Tachycardia Substrate Mapping

BACKGROUND

Accurate annotation of electrogram local activation time (LAT) is critical to the functional assessment of ventricular tachycardia (VT) substrate. Contemporary methods of annotation include: 1) earliest bipolar electrogram (LATearliest); 2) peak bipolar electrogram (LATpeak); 3) latest bipolar electrogram (LATlatest); and 4) steepest unipolar -dV/dt (LAT-dV/dt). However, no direct comparison of these methods has been performed in a large dataset, and it is unclear which provides the optimal functional analysis of the VT substrate.

OBJECTIVES

This study sought to investigate the optimal method of LAT annotation during VT substrate mapping.

METHODS

Patients with high-density VT substrate maps and a defined critical site for VT re-entry were included. All electrograms were annotated using 5 different methods: LATearliest, LATpeak, LATlatest, LAT-dV/dt, and the novel steepest unipolar -dV/dt using a dynamic window of interest (LATDWOI). Electrograms were also tagged as either late potentials and/or fractionated signals. Maps, utilizing each annotation method, were then compared in their ability to identify critical sites using deceleration zones.

RESULTS

Fifty cases were identified with 1,.813 ± 811 points per map. Using LATlatest, a deceleration zone was present at the critical site in 100% of cases. There was no significant difference with LATearliest (100%) or LATpeak (100%). However, this number decreased to 54% using LAT-dV/dt and 76% for LATDWOI. Using LAT-dV/dt, only 33% of late potentials were correctly annotated, with the larger far field signals often annotated preferentially.

CONCLUSIONS

Annotation with LAT-dV/dt and LATDWOI are suboptimal in VT substrate mapping. We propose that LATlatest should be the gold standard annotation method, as this allows identification of critical sites and is most suited to automation.

Cellular heterogeneity of pluripotent stem cell-derived cardiomyocyte grafts is mechanistically linked to treatable arrhythmias

Preclinical data have confirmed that human pluripotent stem cell-derived cardiomyocytes (PSC-CMs) can remuscularize the injured or diseased heart, with several clinical trials now in planning or recruitment stages. However, because ventricular arrhythmias represent a complication following engraftment of intramyocardially injected PSC-CMs, it is necessary to provide treatment strategies to control or prevent engraftment arrhythmias (EAs). Here, we show in a porcine model of myocardial infarction and PSC-CM transplantation that EAs are mechanistically linked to cellular heterogeneity in the input PSC-CM and resultant graft. Specifically, we identify atrial and pacemaker-like cardiomyocytes as culprit arrhythmogenic subpopulations. Two unique surface marker signatures, signal regulatory protein α (SIRPA)+CD90-CD200+ and SIRPA+CD90-CD200-, identify arrhythmogenic and non-arrhythmogenic cardiomyocytes, respectively. Our data suggest that modifications to current PSC-CM-production and/or PSC-CM-selection protocols could potentially prevent EAs. We further show that pharmacologic and interventional anti-arrhythmic strategies can control and potentially abolish these arrhythmias.

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.

Septal Substrate Ablation Guided by Delayed Transmural Conduction Times: A Novel Ablation Approach to Target Intramural Substrates

BACKGROUND

Intraprocedural identification of intramural septal substrate for ventricular tachycardia (ISS-VT) in nonischemic cardiomyopathy (NICM) is challenging. Delayed (>40 ms) transmural conduction time (DCT) with right ventricular basal septal pacing has been previously shown to identify ISS-VT.

OBJECTIVES

This study sought to determine whether substrate catheter ablation incorporating areas of DCT may improve acute and long-term outcomes.

METHODS

We included patients with NICM and ISS-VT referred for catheter ablation between 2016 and 2020. ISS-VT was defined by the following: 1) confluent septal areas of low unipolar voltage (<8.3 mV) in the presence of normal or minimal bipolar abnormalities; and 2) presence of abnormal electrograms in the septum. Substrate ablation was guided by the following: 1) activation and/or entrainment mapping for tolerated VT and pace mapping with ablation of abnormal septal electrograms for unmappable VTs (n = 57, Group 1); and 2) empirically extended to target areas of DCT during right ventricular basal septal pacing regardless of their participation in inducible VT(s) but sparing the conduction system when possible (n = 24, Group 2).

RESULTS

There were no significant baseline differences between Groups 1 and 2. Noninducibility of any VT programmed stimulation at the end of ablation was higher in Group 2 compared with Group 1 (80% vs 53%; P = 0.03). At 12-month follow-up, single-procedure VT-free survival was significantly higher (79% vs 46%; P = 0.006) and the time to VT recurrence was longer (mean 10 ± 3 months vs 7 ± 4 months; P = 0.02) in Group 2 compared with Group 1.

CONCLUSIONS

In patients with NICM and ISS-VT, a substrate ablation strategy that incorporates areas of DCT appears to improve freedom from recurrent VT.

Transcoronary mapping using a guidewire during transcoronary ethanol ablation for ventricular tachycardia with a deep intramural substrate: a case report

Background

Transcoronary ethanol ablation is effective in treating ventricular tachycardia (VT) in the deep myocardium. The selection of the target coronary artery plays an important role in the success of transcoronary ethanol ablation. Transcoronary mapping, using a guidewire, may be effective for identifying the target coronary artery.

Case summary

A 72-year-old man, who had undergone thrombolytic therapy for acute myocardial infarction 40 years ago, was admitted to the emergency department with a chief complaint of syncope. Five years ago, a cardiac resynchronization therapy defibrillator was implanted for a left bundle branch block (QRS duration 153 ms), with New York Heart Association Class Ⅲ and a left ventricular ejection fraction of 30%.Due to VT, he experienced a critical deterioration in his vital parameters, leading to shock. The first VT ablation was performed on the 3rd day of hospitalization. Activation mapping showed that the earliest activation site was located in the mid-anterior septum of the left ventricle. Mapping from the endocardial surface showed no mid-diastolic potential around the VT. Radiofrequency catheter ablation therapy was performed at the targeted site, resulting in transient termination of VT. However, the VT showed recurrence the next day. A transcoronary ethanol ablation was performed on the 10th day of hospitalization. A 0.014 inch guidewire and microcatheter were advanced into the target coronary septal branch, and the myocardial septum was mapped. The guidewire-assisted transcoronary mapping showed a potential 43 ms ahead of QRS onset during VT. The coronary septal artery branch was considered the target artery, and 0.5 mL of ethanol was injected. No further VT was observed for 12 months after the transcoronary ethanol ablation.

Discussion

Transcoronary ethanol ablation is considered in cases where a deep intramural substrate is suspected or when early activation at the interventricular septum is identified. Guidewire-assisted transcoronary mapping allows mapping of VT with deep intramural substrates and may be useful in selecting target coronary arteries while performing transcoronary ethanol ablation.

Quantification of Large Transmural Biopsies Reveals Heterogeneity in Innervation Patterns in Chronic Myocardial Infarction

BACKGROUND

Abnormal cardiac innervation plays an important role in arrhythmogenicity after myocardial infarction (MI). Data regarding reperfusion models and innervation abnormalities in the medium to long term after MI are sparse. Histologic quantification of the small-sized cardiac nerves is challenging, and transmural analysis has not been performed.

OBJECTIVES

This study sought to assess cardiac innervation patterns in transmural biopsy sections in a porcine reperfusion model of MI (MI-R) using a novel method for nerve quantification.

METHODS

Transmural biopsy sections from 4 swine (n = 83) at 3 months after MI-R and 3 controls (n = 38) were stained with picrosirius red (fibrosis) and beta-III-tubulin (autonomic nerves). Biopsy sections were classified as infarct core, border zone, or remote zone. Each biopsy section was analyzed with a custom software pipeline, allowing calculation of nerve density and classification into innervation types at the 1 × 1-mm resolution level. Relocation of the classified squares to the original biopsy position enabled transmural quantification and innervation heterogeneity assessment.

RESULTS

Coexisting hyperinnervation, hypoinnervation, and denervation were present in all transmural MI-R biopsy sections. The innervation heterogeneity was greatest in the infarct core (median: 0.14; IQR: 0.12-0.15), followed by the border zone (median: 0.05; IQR: 0.04-0.07; P = 0.02) and remote zone (median: 0.02; IQR: 0.02-0.03; P < 0.0001). Only in the border zone was a positive linear relation between fibrosis and innervation heterogeneity observed (R = 0.79; P < 0.0001).

CONCLUSIONS

This novel method allows quantification of nerve density and heterogeneity in large transmural biopsy sections. In the chronic phase after MI-R, alternating innervation patterns were identified within the same biopsy section. Persistent innervation heterogeneity, in particular in the border zone biopsy sections, may contribute to late arrhythmogenicity.

Association of Sinus Wavefront Activation and Ventricular Extrastimuli Mapping With Ventricular Tachycardia Re-Entrant Circuits

BACKGROUND

Substrate-based ablation targets areas of delayed and fractionated electrograms during sinus rhythm, which are sensitive for identifying the ventricular tachycardia (VT) isthmus but is influenced by the activation wavefront direction and decremental pacing.

OBJECTIVES

The aim of this study was to correlate the areas of latest activation during varying wavefront activation mapping and decremental pacing mapping with sites critical to the VT isthmus.

METHODS

Three high-density electroanatomical substrate maps were created in patients presenting for ablation of monomorphic VT: 1) native sinus rhythm; 2) right ventricular (RV) apical pacing; and 3) an RV apical S2 map following the S1 drive train at 20 ms above the ventricular effective refractory period. Areas corresponding to the latest activation were compared with the VT isthmus identified by conventional mapping.

RESULTS

Twenty patients with structural heart disease with a mean age of 55.6 ± 16.9 years were included. The majority of the cohort consisted of patients with ischemic heart disease (50%) and arrhythmogenic RV cardiomyopathy (35%). Epicardial ablation was performed in 45% of patients. The concordance of the site of latest activation in sinus rhythm with the VT isthmus was 75%. The location of the latest activation during RV apical pacing corresponded with the VT isthmus in 85% of cases. However, in 95% of cases, the site of the latest activation following the S2 stimulus colocalized to the VT isthmus.

CONCLUSIONS

In a mix of underlying myocardial substrates, regions of conduction slowing during decremental pacing colocalize with the VT isthmus more frequently than sinus rhythm activation mapping and may have a role in substrate-based ablation where VT induction is undesirable.

Effects of Mesenchymal Stem Cell Injection into Healed Myocardial Infarction Scar Border Zone on the Risk of Ventricular Tachycardia

The scar border zone is a main source of reentry responsible for ischemic ventricular tachycardia (VT). We evaluated the effects of mesenchymal stem cell (MSC) injection into the scar border zone on arrhythmic risks in a post-myocardial infarction (MI) animal model. Rabbit MI models were generated by left descending coronary artery ligation. Surviving rabbits after 4 weeks underwent left thoracotomy and autologous MSCs or phosphate-buffered saline (PBS) was administered to scar border zones in two rabbits in each group. Another rabbit without MI underwent a sham procedure (control). An implantable loop recorder (ILR) was implanted in the left chest wall in all animals. Four weeks after cell injections, ventricular fibrillation was induced in 1/2 rabbit in the PBS group by electrophysiologic study, and no ventricular arrhythmia was induced in the MSC group or control. Spontaneous VT was not detected during ILR analysis in any animal for 4 weeks. Histologic examination showed restoration of connexin 43 (Cx43) expression in the MSC group, which was higher than in the PBS group and comparable to the control. In conclusion, MSC injections into the MI scar border zone did not increase the risk of VT and were associated with favorable Cx43 expression and arrangement.

Prognostic Value of Different Thresholds for Myocardial Scar Quantification on Cardiac MRI Late Gadolinium Enhancement Images in Patients Receiving Implantable Cardioverter Defibrillators

Purpose

To compare the predictive value of different myocardial scar quantification thresholds using cardiac MRI for appropriate implantable cardioverter defibrillator (ICD) shock and mortality.

Materials and Methods

In this retrospective, two-center observational cohort study, patients with ischemic or nonischemic cardiomyopathy underwent cardiac MRI prior to ICD implantation. Late gadolinium enhancement (LGE) was first determined visually and then quantified by blinded cardiac MRI readers using different SDs above the mean signal of normal myocardium, full-width half-maximum, and manual thresholding. The intermediate signal "gray zone" was calculated as the differences between different SDs.

Results

Among 374 consecutive eligible patients (mean age, 61 years ± 13 [SD]; mean left ventricular ejection fraction, 32% ± 14; secondary prevention, 62.7%), those with LGE had a higher rate of appropriate ICD shock or death than those without (37.5% vs 26.6%, log-rank P = .04) over a median follow-up of 61 months. In multivariable analysis, none of the thresholds for quantifying scar was a significant predictor of mortality or appropriate ICD shock, while the extent of gray zone was an independent predictor (adjusted hazard ratio per 1 g = 1.025; 95% CI: 1.008, 1.043; P = .005) regardless of the presence or absence of ischemic heart disease (P interaction = .57). Model discrimination was highest for the model incorporating the gray zone (between 2 SD and 4 SD).

Conclusion

Presence of LGE was associated with a higher rate of appropriate ICD shock or death. Although none of the scar quantification techniques predicted outcomes, the gray zone both in infarct and nonischemic scar was an independent predictor and may refine risk stratification.Keywords: MRI, Scar Quantification, Implantable Cardioverter Defibrillator, Sudden Cardiac Death Supplemental material is available for this article. © RSNA, 2023.

Quelling the Storm: A Review of the Management of Electrical Storm

Heightened sympathetic input to the myocardium potentiates cardiac electrical instability and may herald an electrical storm. An electrical storm is characterized by 3 or more episodes of ventricular tachycardia, ventricular fibrillation, or appropriate internal cardiac defibrillator shocks within 24 hours. Management of electrical storms is resource-intensive and inevitably requires careful coordination between multiple subspecialties. Anesthesiologists have an important role in acute, subacute, and long-term management. Identifying the phase of an electrical storm and understanding the characteristics of each morphology may help the anesthesiologist anticipate the management approach. In the acute phase, management of an electrical storm is aimed at providing advanced cardiac life support and identifying reversible causes. After initial stabilization, subacute management focuses on dampening the sympathetic surge with sedation, thoracic epidural, or stellate ganglion blockade. Definitive long-term management with surgical sympathectomy or catheter ablation also may be warranted. Our objective is to provide an overview of electrical storms and the anesthesiologist's role in management.

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.

Retrospective Window of Interest Annotation Provides New Insights Into Functional Channels in Ventricular Tachycardia Substrate

BACKGROUND

Accurate annotation of local activation time is crucial in the functional assessment of ventricular tachycardia (VT) substrate. A major limitation of modern mapping systems is the standard prospective window of interest (sWOI) is limited to 490 to 500 milliseconds, preventing annotation of very late potentials (LPs). A novel retrospective window of interest (rWOI), which allows annotation of all diastolic potentials, was used to assess the functional VT substrate.

OBJECTIVES

This study sought to investigate the utility of a novel rWOI, which allows accurate visualization and annotation of all LPs during VT substrate mapping.

METHODS

Patients with high-density VT substrate maps and a defined isthmus were included. All electrograms were manually annotated to latest activation using a novel rWOI. Reannotated substrate maps were correlated to critical sites, with areas of late activation examined. Propagation patterns were examined to assess the functional aspects of the VT substrate.

RESULTS

Forty-eight cases were identified with 1,820 ± 826 points per map. Using the novel rWOI, 31 maps (65%) demonstrated LPs beyond the sWOI limit. Two distinct patterns of channel activation were seen during substrate mapping: 1) functional block with unidirectional conduction into the channel (76%); and 2) wave front collision within the channel (24%). In addition, a novel marker termed the zone of early and late crowding was studied in the rWOI substrate maps and found to have a higher positive predictive value (85%) than traditional deceleration zones (69%) for detecting critical sites of re-entry.

CONCLUSIONS

The standard WOI of contemporary mapping systems is arbitrarily limited and results in important very late potentials being excluded from annotation. Future versions of electroanatomical mapping systems should provide longer WOIs for accurate local activation time annotation.

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.

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.

Directed Graph Mapping for Ventricular Tachycardia: A Comparison to Established Mapping Techniques

BACKGROUND

Understanding underlying mechanism(s) and identifying critical circuit components are fundamental to successful ventricular tachycardia (VT) ablation. Directed graph mapping (DGM) offers a novel technique to identify the mechanism and critical components of a VT circuit.

OBJECTIVES

This study sought to evaluate the accuracy of DGM in VT ablation compared with traditional mapping techniques and a commercially available automated conduction velocity mapping (ACVM) tool.

METHODS

Patients with structural heart disease who had undergone a VT ablation with entrainment-proven critical isthmus and a high-density electroanatomical activation map were included. Traditional mapping (TM) consisted of a combination of local activation time and entrainment mapping and was considered the gold standard for determining the VT mechanism, circuit, and isthmus location. The same local activation time values were then processed using DGM and a commercially available ACVM (Coherent Mapping, Biosense Webster) tool. The aim of this study was to compare TM vs DGM and ACVM in their ability to identify the VT mechanism, characterize the VT circuit, and locate the critical isthmus.

RESULTS

Thirty-five cases were identified. TM classified the VT mechanism as focal in 7 patients and re-entrant in 28 patients. TM classified 11 VTs as single-loop re-entry, 15 as dual-loop re-entry, 1 as complex, and 1 case was indeterminant. The overall agreement between DGM and TM for determining VT mechanism and circuit type was strong (kappa value = 0.79; P < 0.01), as was the agreement between ACVM and TM (kappa value = 0.66; P < 0.01). Both DGM and ACVM identified the putative VT isthmus in 25 (89%) of the re-entrant cases. Focal activation was correctly identified by both techniques in all cases.

CONCLUSIONS

DGM is a rapid automated algorithm that has a strong level of agreement with TM for manually re-annotated VT maps.

The physics of heart rhythm disorders

The global burden caused by cardiovascular disease is substantial, with heart disease representing the most common cause of death around the world. There remains a need to develop better mechanistic models of cardiac function in order to combat this health concern. Heart rhythm disorders, or arrhythmias, are one particular type of disease which has been amenable to quantitative investigation. Here we review the application of quantitative methodologies to explore dynamical questions pertaining to arrhythmias. We begin by describing single-cell models of cardiac myocytes, from which two and three dimensional models can be constructed. Special focus is placed on results relating to pattern formation across these spatially-distributed systems, especially the formation of spiral waves of activation. Next, we discuss mechanisms which can lead to the initiation of arrhythmias, focusing on the dynamical state of spatially discordant alternans, and outline proposed mechanisms perpetuating arrhythmias such as fibrillation. We then review experimental and clinical results related to the spatio-temporal mapping of heart rhythm disorders. Finally, we describe treatment options for heart rhythm disorders and demonstrate how statistical physics tools can provide insights into the dynamics of heart rhythm disorders.

Distribution of evoked delayed potential and delayed potential in a patient with subendocardial inferior infarction and transmural postero-lateral infarction: A case report

A 47-year-old man with transmural posterolateral myocardial infarction (MI) and subendocardial inferior MI underwent catheter ablation for monomorphic ventricular tachycardia (VT). Right ventricular extra stimulation could unmask evoked delayed potentials in the subendocardial infarction area without delayed potentials in the sinus rhythm. Extra stimulation mapping for VT is useful for hidden VT substrates, particularly in the subendocardial infarction area.

Functional Assessment of Ventricular Tachycardia Circuits and Their Underlying Substrate Using Automated Conduction Velocity Mapping

OBJECTIVES

This study sought to describe the utility of automated conduction velocity mapping (ACVM) in ventricular tachycardia (VT) ablation.

BACKGROUND

Identification of areas of slowed conduction velocity (CV) is critical to our understanding of VT circuits and their underlying substrate. Recently, an ACVM called Coherent Mapping (Biosense Webster Inc) has been developed for atrial mapping. However, its utility in VT mapping has not been described.

METHODS

Patients with paired high-density VT activation and substrate maps were included. ACVM was applied to paired VT activation and substrate maps to assess regional CV and activation patterns. A combination of ACVM, traditional local activation time maps, electrogram analysis, and off-line calculated CV using triangulation were used to characterize zones of slowed conduction during VT and in substrate mapping.

RESULTS

Fifteen patients were included in the study. In all cases, ACVM identified slow CV within the putative VT isthmus, which colocalized to the VT isthmus identified with entrainment. The dimensions of the VT isthmus with local activation time mapping were 37.8 ± 13.7 mm long and 8.7 ± 4.2 mm wide. In comparison, ACVM produced an isthmus that was shorter (length: 25.1 ± 10.6 mm; mean difference: 12.8; 95% CI: 7.5-18.0; P < 0.01) and wider (width: 18.8 ± 8.1 mm; mean difference: 10.1; 95% CI: 6.1-14.2; P < 0.01). In VT, the CV using triangulation at the entrance (8.0 ± 3.6 cm/s) and midisthmus (8.1 ± 4.3 cm/s) was not significantly different (P = 0.92) but was significantly faster at the exit (16.2 ± 9.7 cm/s; P < 0.01). In the paired substrate analysis, traditional local activation time isochronal mapping identified 6.3 ± 2.0 deceleration zones. In contrast, ACVM identified a median of 0 deceleration zones (IQR: 0-1; P < 0.01).

CONCLUSIONS

ACVM is a novel complementary tool that can be used to accurately resolve complex VT circuits and identify slow conduction zones in VT but has limited accuracy in identifying slowed conduction during substrate-based mapping.

Sudden cardiac death in heart failure with preserved ejection fraction: an updated review

Despite the advances in medical and device therapies for heart failure (HF), sudden cardiac death (SCD) remains a tremendous global burden in patients with HF. Among the risk factors for SCD, HF has the greatest impact. Previous studies focusing on patients with systolic dysfunction have found several predictive factors associated with SCD, leading to the subsequent development of strategies of primary prevention, like placement of implantable cardioverter-defibrillator (ICD) in high-risk patients. Although patients with HF with preserved ejection fraction (HFpEF) were less prone to SCD compared to patients with HF with reduced ejection fraction (HFrEF), patients with HFpEF did account for a significant proportion of all HF patients who encountered SCD. The cutoff value of left ventricular ejection fraction (LVEF) to define the subset of HF did not reach consensus until 2016 when the European Society of Cardiology proposed a new classification system by LVEF. There is a great unmet need in the field of SCD in HFpEF regarding risk stratification and appropriate device therapy with ICD implantation. In this article, we will approach SCD in HFpEF from HFrEF subsets. We also aim at clarifying the mechanisms, risk factors, and prevention of SCD in HFpEF.

Spectral characterisation of ventricular intracardiac potentials in human post-ischaemic bipolar electrograms

Abnormal ventricular potentials (AVPs) are frequently referred to as high-frequency deflections in intracardiac electrograms (EGMs). However, no scientific study performed a deep spectral characterisation of AVPs and physiological potentials in real bipolar intracardiac recordings across the entire frequency range imposed by their sampling frequency. In this work, the power contributions of post-ischaemic physiological potentials and AVPs, along with some spectral features, were evaluated in the frequency domain and then statistically compared to highlight specific spectral signatures for these signals. To this end, 450 bipolar EGMs from seven patients affected by post-ischaemic ventricular tachycardia were retrospectively annotated by an experienced cardiologist. Given the high variability of the morphologies observed, three different sub-classes of AVPs and two sub-categories of post-ischaemic physiological potentials were considered. All signals were acquired by the CARTO® 3 system during substrate-guided catheter ablation procedures. Our findings indicated that the main frequency contributions of physiological and pathological post-ischaemic EGMs are found below 320 Hz. Statistical analyses showed that, when biases due to the signal amplitude influence are eliminated, not only physiological potentials show greater contributions below 20 Hz whereas AVPs demonstrate higher spectral contributions above ~ 40 Hz, but several finer differences may be observed between the different AVP types.

Application of EnsiteTM LiveView Function for Identification of Scar-related Ventricular Tachycardia Isthmus

INTRODUCTION

Dynamic display of real-time wavefront activation pattern may facilitate the recognition of reentrant circuits, particularly the diastolic path of ventricular tachycardia (VT).

OBJECTIVE

We aimed to evaluate the feasibility of LiveView Dynamic Display for mapping the critical isthmus of scar-related reentrant VT.

METHODS

Patients with mappable scar-related reentrant VT were selected. The characteristics of the underlying substrates and VT circuits were assessed using HD grid multi-electrode catheter. The VT isthmuses were identified based on the activation map, entrainment, and ablation results. The accuracy of the LiveView findings in detecting potential VT isthmus was assessed.

RESULTS

We studied 18 scar-related reentrant VTs in 10 patients (median age: 59.5 years, 100% male) including 6 and 4 patients with ischemic and non-ischemic cardiomyopathy, respectively. The median VT cycle length was 426 ms (interquartile range: 386-466 ms). Among 590 regional mapping displays, 92.0% of the VT isthmus sites were identified by LiveView Dynamic Display. The accuracy of LiveView for isthmus identification was 84%, with positive and negative predictive values of 54.8% and 97.8%, respectively. The area with abnormal electrograms was negatively correlated with the accuracy of LiveView Dynamic Display (r = -0.506, p = 0.027). The median time interval to identify a VT isthmus using LiveView was significantly shorter than that using conventional activation maps (50.5 [29.8-120] vs. 219 [157.5-400.8] s, p = 0.015).

CONCLUSION

This study demonstrated the feasibility of LiveView Dynamic Display in identifying the critical isthmus of scar-related VT with modest accuracy. This article is protected by copyright. All rights reserved.

[Update on ablation of ventricular tachyarrhythmias]

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

Effect of implantable cardioverter-defibrillators in patients with non-ischaemic systolic heart failure and concurrent coronary atherosclerosis

Aims

Prophylactic implantable cardioverter‐defibrillators (ICD) reduce mortality in patients with ischaemic heart failure (HF), whereas the effect of ICD in patients with non‐ischaemic HF is less clear. We aimed to investigate the association between concomitant coronary atherosclerosis and mortality in patients with non‐ischaemic HF and the effect of ICD implantation in these patients.

Methods and results

Patients were included from DANISH (Danish Study to Assess the Efficacy of Implantable Cardioverter Defibrillators in Patients with Non‐Ischaemic Systolic Heart Failure on Mortality), randomizing patients to ICD or control. Study inclusion criteria for HF were left ventricular ejection fraction ≤ 35% and increased levels (>200 pg/mL) of N‐terminal pro‐brain natriuretic peptide. Of the 1116 patients from DANISH, 838 (75%) patients had available data from coronary angiogram and were included in this subgroup analysis. We used Cox regression to assess the relationship between coronary atherosclerosis and mortality and the effect of ICD implantation. Of the included patients, 266 (32%) had coronary atherosclerosis. Of these, 216 (81%) had atherosclerosis without significant stenoses, and 50 (19%) had significant stenosis. Patients with atherosclerosis were significantly older {67 [interquartile range (IQR) 61–73] vs. 61 [IQR 54–68] years; P < 0.0001}, and more were men (77% vs. 70%; P = 0.03). During a median follow‐up of 64.3 months (IQR 47–82), 174 (21%) of the patients died. The effect of ICD on all‐cause mortality was not modified by coronary atherosclerosis [hazard ratio (HR) 0.94; 0.58–1.52; P = 0.79 vs. HR 0.82; 0.56–1.20; P = 0.30], P for interaction = 0.67. In univariable analysis, coronary atherosclerosis was a significant predictor of all‐cause mortality [HR, 1.41; 95% confidence interval (CI), 1.04–1.91; P = 0.03]. However, this association disappeared when adjusting for cardiovascular risk factors (age, gender, diabetes, hypertension, smoking, and estimated glomerular filtration rate) (HR 1.05, 0.76–1.45, P = 0.76).

Conclusions

In patients with non‐ischaemic systolic heart failure, ICD implantation did not reduce all‐cause mortality in patients either with or without concomitant coronary atherosclerosis. The concomitant presence of coronary atherosclerosis was associated with increased mortality. However, this association was explained by other risk factors.

Rotational Activation Pattern During Functional Substrate Mapping: Novel Target for Catheter Ablation of Scar-Related Ventricular Tachycardia

BACKGROUND

Recent advancements in a 3-dimensional mapping system allow for the assessment of detailed conduction properties during sinus rhythm and thus the establishment of a strategy targeting functionally abnormal regions in scar-related ventricular tachycardia (VT). We hypothesized that a rotational activation pattern (RAP) observed in maps during baseline rhythm was associated with the critical location of VT.

METHODS

We retrospectively examined the pattern of wavefront propagation during sinus rhythm in patients with scar-related VT. The prevalence and features of the RAP on critical VT circuits were analyzed. RAP was defined as >90° of inward curvature directly above or at the edge of the slow conductive areas.

RESULTS

Forty-five VTs in 37 patients (66±15 years old, 89% male, 27% ischemic heart disease) were evaluated. High-density substrate mapping during sinus rhythm (median, 2524 points) was performed using the CARTO3 system before VT induction. Critical sites for reentry were identified by direct termination by radiofrequency catheter ablation in 21 VTs or by pace mapping in 12 VTs. Among them, RAP was present in 70% of the 33 VTs. Four VTs had no RAP at the critical sites during sinus rhythm, but it became visible in the mappings with different wavefront directions. Six VTs, in which intramural or epicardial isthmus was suspected, were rendered noninducible by radiofrequency catheter ablation to the endocardial surface without RAP. RAP had a sensitivity and specificity of 70% and 89%, respectively, for predicting the elements in the critical zone for VT.

CONCLUSIONS

The critical zone of VT appears to correspond to an area characterized by the RAP with slow conduction during sinus rhythm, which facilitates targeting areas specific for reentry. However, this may not be applicable to intramural VT substrates and might be affected by the direction of wavefront propagation to the scar during mapping.

A new biomarker that predicts ventricular arrhythmia in patients with ischemic dilated cardiomyopathy: Galectin-3

INTRODUCTION

Ventricular arrhythmias are caused by scar tissue in patients with ischemic dilated cardiomyopathy. The gold standard imaging technique for detecting scar tissue is magnetic resonance imaging (MRI). However, MRI is not feasible for use as a screening test, and also cannot be used in patients who have received an implantable cardioverter-defibrillator (ICD). In this study, we aimed to assess the association between levels of galectin-3 (Gal-3), which is known to be secreted by scar tissue, and the history of ventricular arrhythmias in patients with ischemic dilated cardiomyopathy who received an ICD.

METHODS

Nineteen healthy controls and 32 patients who had previously undergone VVI-ICD implantation due to ischemic dilated cardiomyopathy were enrolled in the study. Patients were divided into three groups: the first group including patients who had received no ICD therapies, the second including patients with arrhythmia requiring therapies with no arrhythmia storm, and the third including patients who had arrhythmia storm. We assessed the association between Gal-3 levels and the history of ventricular arrhythmias in these patients.

RESULTS

Gal-3 levels were significantly higher in the patient groups than in the control group (p<0.01). Gal-3 levels of patients with arrhythmias requiring ICD therapies were significantly higher than in patients with ICD not requiring therapies (p=0.02). They were also higher in patients with a history of arrhythmia storm than in patients without shocks (p=0.05). Receiver operating curve analysis showed with 84% sensitivity and 75% specificity that Gal-3 levels over 7 ng/ml indicated ventricular arrhythmia that required therapies.

CONCLUSION

Gal-3 may be used to further improve risk stratification in patients with ischemic cardiomyopathy who are more prone to developing life-threatening arrhythmias.

Late Gadolinium Enhancement Cardiovascular Magnetic Resonance Assessment of Substrate for Ventricular Tachycardia With Hemodynamic Compromise

Background: The majority of data regarding tissue substrate for post myocardial infarction (MI) VT has been collected during hemodynamically tolerated VT, which may be distinct from the substrate responsible for VT with hemodynamic compromise (VT-HC). This study aimed to characterize tissue at diastolic locations of VT-HC in a porcine model. Methods: Late Gadolinium Enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging was performed in eight pigs with healed antero-septal infarcts. Seven pigs underwent electrophysiology study with venous arterial-extra corporeal membrane oxygenation (VA-ECMO) support. Tissue thickness, scar and heterogeneous tissue (HT) transmurality were calculated at the location of the diastolic electrograms of mapped VT-HC. Results: Diastolic locations had median scar transmurality of 33.1% and a median HT transmurality 7.6%. Diastolic activation was found within areas of non-transmural scar in 80.1% of cases. Tissue activated during the diastolic component of VT circuits was thinner than healthy tissue (median thickness: 5.5 mm vs. 8.2 mm healthy tissue, p < 0.0001) and closer to HT (median distance diastolic tissue: 2.8 mm vs. 11.4 mm healthy tissue, p < 0.0001). Non-scarred regions with diastolic activation were closer to steep gradients in thickness than non-scarred locations with normal EGMs (diastolic locations distance = 1.19 mm vs. 9.67 mm for non-diastolic locations, p < 0.0001). Sites activated late in diastole were closest to steep gradients in tissue thickness. Conclusions: Non-transmural scar, mildly decreased tissue thickness, and steep gradients in tissue thickness represent the structural characteristics of the diastolic component of reentrant circuits in VT-HC in this porcine model and could form the basis for imaging criteria to define ablation targets in future trials.

Assessment of an ECG-Based System for Localizing Ventricular Arrhythmias in Patients With Structural Heart Disease

Background

We have previously developed an intraprocedural automatic arrhythmia‐origin localization (AAOL) system to identify idiopathic ventricular arrhythmia origins in real time using a 3‐lead ECG. The objective was to assess the localization accuracy of ventricular tachycardia (VT) exit and premature ventricular contraction (PVC) origin sites in patients with structural heart disease using the AAOL system.

Methods and Results

In retrospective and prospective case series studies, a total of 42 patients who underwent VT/PVC ablation in the setting of structural heart disease were recruited at 2 different centers. The AAOL system combines 120‐ms QRS integrals of 3 leads (III, V2, V6) with pace mapping to predict VT exit/PVC origin site and projects that site onto the patient‐specific electroanatomic mapping surface. VT exit/PVC origin sites were clinically identified by activation mapping and/or pace mapping. The localization error of the VT exit/PVC origin site was assessed by the distance between the clinically identified site and the estimated site. In the retrospective study of 19 patients with structural heart disease, the AAOL system achieved a mean localization accuracy of 6.5±2.6 mm for 25 induced VTs. In the prospective study with 23 patients, mean localization accuracy was 5.9±2.6 mm for 26 VT exit and PVC origin sites. There was no difference in mean localization error in epicardial sites compared with endocardial sites using the AAOL system (6.0 versus 5.8 mm, P=0.895).

Conclusions

The AAOL system achieved accurate localization of VT exit/PVC origin sites in patients with structural heart disease; its performance is superior to current systems, and thus, it promises to have potential clinical utility.

Refractory Ventricular Tachycardia Originating From an Intracardiac Metastasis Treated With Catheter Ablation

A 45-year-old man with stage IV melanoma presented with incessant nonsustained wide complex tachycardia. He was found to have a right ventricular intracardiac metastasis that created a nidus for ventricular tachycardia refractory to multiple therapeutic interventions. The patient underwent catheter ablation for this rare indication, with successful arrhythmia control by direct ablation over the tumor surface. (Level of Difficulty: Advanced.).

Dynamic spatial dispersion of repolarization is present in regions critical for ischemic ventricular tachycardia ablation

BACKGROUND

The presence of dynamic substrate changes may facilitate functional block and reentry in ventricular tachycardia (VT).

OBJECTIVE

We aimed to study dynamic ventricular repolarization changes in critical regions of the VT circuit during sensed single extrastimulus pacing known as the Sense Protocol (SP).

METHODS

Twenty patients (aged 67 ± 9 years, 17 male) underwent VT ablation. A bipolar voltage map was obtained during sinus rhythm (SR) and right ventricular SP pacing at 20 ms above ventricular effective refractory period. Ventricular repolarization maps were constructed. Ventricular repolarization time (RT) was calculated from unipolar electrogram T waves, using the Wyatt method, as the dV/dtmax of the unipolar T wave. Entrainment or pace mapping confirmed critical sites for ablation.

RESULTS

The median global repolarization range (max-min RT per patient) was 166 ms (interquartile range [IQR] 143-181 ms) during SR mapping vs 208 ms (IQR 182-234) during SP mapping (P = .0003 vs intrinsic rhythm). Regions of late potentials (LP) had a longer RT during SP mapping compared to regions without LP (mean 394 ± 40 ms vs 342 ± 25 ms, P < .001). In paired regions of normal myocardium there was no significant spatial dispersion of repolarization (SDR)/10 mm2 during SP mapping vs SR mapping (SDR 11 ± 6 ms vs 10 ± 6 ms, P = .54). SDR/10 mm2 was greater in critical areas of the VT circuit during SP mapping 63 ± 29 ms vs SR mapping 16 ± 9 ms (P < .001).

CONCLUSION

Ventricular repolarization is prolonged in regions of LP and increases dynamically, resulting in dynamic SDR in critical areas of the VT circuit. These dynamic substrate changes may be an important factor that facilitates VT circuits.

Dynamic High-density Functional Substrate Mapping Improves Outcomes in Ischaemic Ventricular Tachycardia Ablation: Sense Protocol Functional Substrate Mapping and Other Functional Mapping Techniques

Post-infarct-related ventricular tachycardia (VT) occurs due to reentry over surviving fibres within ventricular scar tissue. The mapping and ablation of patients in VT remains a challenge when VT is poorly tolerated and in cases in which VT is non-sustained or not inducible. Conventional substrate mapping techniques are limited by the ambiguity of substrate characterisation methods and the variety of mapping tools, which may record signals differently based on their bipolar spacing and electrode size. Real world data suggest that outcomes from VT ablation remain poor in terms of freedom from recurrent therapy using conventional techniques. Functional substrate mapping techniques, such as single extrastimulus protocol mapping, identify regions of unmasked delayed potentials, which, by nature of their dynamic and functional components, may play a critical role in sustaining VT. These methods may improve substrate mapping of VT, potentially making ablation safer and more reproducible, and thereby improving the outcomes. Further large-scale studies are needed.

Prediction of Serious Adverse Events of Patients with Hypertrophic Cardiomyopathy by Magnetic Resonance

Although it is well known that patients with hypertrophic cardiomyopathy (HCM) have serious adverse events, such as life-threatening arrhythmia and heart failure, the prediction of such evens is still difficult. Recently, it has been reported that one of the causes of these serious adverse events is microvascular dysfunction, which can be noninvasively evaluated by employing cardiac magnetic resonance (CMR) imaging.We analyzed 32 consecutive HCM patients via CMR imaging and myocardial scintigraphy and divided them into two groups: ventricular tachycardia (VT) group and non-VT group. Myocardial perfusion studies were conducted quantitatively using the QMass^® software, and each slice image was divided into six segments. The time-intensity curve derived from the perfusion image by CMR imaging was evaluated, and the time to 50% of the peak intensity (time 50% max) was automatically calculated for each segment.Although no difference was observed in various parameters of myocardial scintigraphy between the two groups, the VT group exhibited a higher mean of time 50% max and wider standard deviation (SD) of time 50% max in each segment than the non-VT group. The cutoff values were obtained by the receiver operating characteristic curves derived from the mean of time 50% max and SD of time 50% max. The two groups divided by the cutoff values exhibited significant differences in the occurrence of serious adverse events.CMR imaging may be useful for predicting serious adverse events of patients with HCM.

Impact of a high-density grid catheter on long-term outcomes for structural heart disease ventricular tachycardia ablation

Background

Substrate mapping has highlighted the importance of targeting diastolic conduction channels and late potentials during ventricular tachycardia (VT) ablation. State-of-the-art multipolar mapping catheters have enhanced mapping capabilities. The purpose of this study was to investigate whether long-term outcomes were improved with the use of a HD Grid mapping catheter combining complementary mapping strategies in patients with structural heart disease VT.

Methods

Consecutive patients underwent VT ablation assigned to either HD Grid, Pentaray, Duodeca, or point-by-point (PbyP) RF mapping catheters. Clinical endpoints included recurrent anti-tachycardia pacing (ATP), appropriate shock, asymptomatic non-sustained VT, or all-cause death.

Results

Seventy-three procedures were performed (33 HD Grid, 22 Pentaray, 12 Duodeca, and 6 PbyP) with no significant difference in baseline characteristics. Substrate mapping was performed in 97% of cases. Activation maps were generated in 82% of HD Grid cases (Pentaray 64%; Duodeca 92%; PbyP 33% (p = 0.025)) with similar trends in entrainment and pace mapping. Elimination of all VTs occurred in 79% of HD Grid cases (Pentaray 55%; Duodeca 83%; PbyP 33% (p = 0.04)). With a mean follow-up of 372 ± 234 days, freedom from recurrent ATP and shock was 97% and 100% respectively in the HD Grid group (Pentaray 64%, 82%; Duodeca 58%, 83%; PbyP 33%, 33% (log rank p = 0.0042, p = 0.0002)).

Conclusions

This study highlights a step-wise improvement in survival free from ICD therapies as the density of mapping capability increases. By using a high-density mapping catheter and combining complementary mapping strategies in a strict procedural workflow, long-term clinical outcomes are improved.

CT- und MRT-Bildgebung in der Rhythmologie

Die Anwendung bildgebender Verfahren gewinnt in der interventionellen Elektrophysiologie entgegen der geringen Beachtung in den aktuell geltenden nationalen und internationalen Leitlinien zur Behandlung von Patienten mit Vorhofflimmern und ventrikulären Tachykardien auch über die reine Diagnostik zugrunde liegender struktureller Herzerkrankungen hinaus immer mehr an Bedeutung. Die breite Anwendung der Computertomografie (CT) und der Magnetresonanztomografie (MRT) ergibt sich aus den spezifischen Möglichkeiten dieser bildgebenden Techniken heraus: Gewebecharakterisierung des Myokards auf Vorhof- und Kammerebene mit präziser Darstellung von Infarktnarben, Grenzzonen und vitalem Myokard (MRT inklusive Late-Gadolinium-Enhancement-Darstellung); hochauflösende Darstellung wichtiger anatomischer Strukturen inklusive der Koronararterien und präzise Identifizierung von kritischer ventrikulärer Wandausdünnung im Infarktareal (CT); Identifizierung potenzieller Komplikationen nach Vorhofflimmerablation (Pulmonalvenenstenosen, Ösophagusruptur oder -fistel). Stärken und Schwächen sowie mögliche relative und absolute Kontraindikationen bei der Anwendung dieser beiden Methoden müssen jedoch berücksichtigt werden. Generell kann die Anwendung bildgebender Verfahren insbesondere für die Therapieplanung und -steuerung als wertvolle Ergänzung mit der Möglichkeit der Steigerung von Effektivität und Sicherheit gesehen werden. Prospektive randomisierte Studien liegen jedoch zu wichtigen aktuellen Anwendungsbereichen der CT und MRT noch nicht vor. Wichtigste Grundlage der interventionellen Elektrophysiologie in der Therapie supraventrikulärer und ventrikulärer Arrhythmien wird noch auf lange Sicht die Anwendung klassischer elektrophysiologischer Manöver und Strategien sowie die Verwendung sich immer weiter entwickelnder elektroanatomischer Mappingsysteme bleiben.