Multisize Electrode Field-of-View: Validation by High Resolution Gadolinium-Enhanced Cardiac Magnetic Resonance

BACKGROUND

Voltage mapping to detect ventricular scar is important for guiding catheter ablation, but the field-of-view of unipolar, bipolar, conventional, and microelectrodes as it relates to the extent of viable myocardium (VM) is not well defined.

OBJECTIVES

The purpose of this study was to evaluate electroanatomic voltage-mapping (EAVM) with different-size electrodes for identifying VM, validated against high-resolution ex-vivo cardiac magnetic resonance (HR-LGE-CMR).

METHODS

A total of 9 swine with early-reperfusion myocardial infarction were mapped with the QDOT microcatheter. HR-LGE-CMR (0.3-mm slices) were merged with EAVM. At each EAVM point, the underlying VM in multisize transmural cylinders and spheres was quantified from ex vivo CMR and related to unipolar and bipolar voltages recorded from conventional and microelectrodes.

RESULTS

In each swine, 220 mapping points (Q1, Q3: 216, 260 mapping points) were collected. Infarcts were heterogeneous and nontransmural. Unipolar and bipolar voltage increased with VM volumes from >175 mm3 up to >525 mm3 (equivalent to a 5-mm radius cylinder with height >6.69 mm). VM volumes in subendocardial cylinders with 1- or 3-mm depth correlated poorly with all voltages. Unipolar voltages recorded with conventional and microelectrodes were similar (difference 0.17 ± 2.66 mV) and correlated best to VM within a sphere of radius 10 and 8 mm, respectively. Distance-weighting did not improve the correlation.

CONCLUSIONS

Voltage increases with transmural volume of VM but correlates poorly with small amounts of VM, which limits EAVM in defining heterogeneous scar. Microelectrodes cannot distinguish thin from thick areas of subendocardial VM. The field-of-view for unipolar recordings for microelectrodes and conventional electrodes appears to be 8 to 10 mm, respectively, and unexpectedly similar.

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

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

Frequency Domain Analysis of Endocardial Electrograms for Detection of Nontransmural Myocardial Fibrosis in Nonischemic Cardiomyopathy

BACKGROUND

Voltage mapping in nonischemic cardiomyopathy can fail to identify midmyocardial substrate for ventricular arrhythmias, an important cause of ablation failure.

OBJECTIVES

The aim of this study was to assess whether frequency domain analysis of endocardial left ventricular electrograms (EGMs) can better predict the presence of midmyocardial fibrosis (MMF) compared with voltage amplitude.

METHODS

Nonischemic cardiomyopathy patients undergoing ventricular tachycardia ablation with registered preprocedural cardiac computed tomography and late iodine enhancement were included. Presence of fibrosis at each EGM site was assessed. Bipolar and unipolar EGMs were transformed to the frequency domain using multitaper spectral analysis. Singular value decomposition of the EGM frequency spectrum was used within a supervised machine learning process to select features to predict the presence of MMF and compare against predictions using voltage amplitude.

RESULTS

Thirteen patients were included (median age 57 years [IQR: 28-73 years], median ejection fraction 40% [IQR: 15%-57%]). A total of 6,015 EGM pairs were processed: 2,459 EGM pairs in MMF areas and 3,556 EGM pairs in non-MMF areas. Supervised classifiers were trained with stratified k-fold cross-validation within patients. The distribution of mean area under the curve metrics using frequency features, f, was significantly greater than voltage feature area under the curve metrics, v, (mean f = 0.841 [95% CI: 0.789-0.884] vs mean v = 0.591 [95% CI: 0.530-0.658]; P < 0.001), indicating that frequency-trained classifiers better predicted the presence of MMF.

CONCLUSIONS

These data indicate the promising discriminatory value of endocardial EGM frequency content in the assessment of concealed myocardial substrate. Further studies are needed to investigate the importance of the specific frequency features identified.

Comprehensive Phenotypic Characterization of Late Gadolinium Enhancement Predicts Sudden Cardiac Death in Coronary Artery Disease

BACKGROUND

Late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) offers the potential to noninvasively characterize the phenotypic substrate for sudden cardiac death (SCD).

OBJECTIVES

The authors assessed the utility of infarct characterization by CMR, including scar microstructure analysis, to predict SCD in patients with coronary artery disease (CAD).

METHODS

Patients with stable CAD were prospectively recruited into a CMR registry. LGE quantification of core infarction and the peri-infarct zone (PIZ) was performed alongside computational image analysis to extract morphologic and texture scar microstructure features. The primary outcome was SCD or aborted SCD.

RESULTS

Of 437 patients (mean age: 64 years; mean left ventricular ejection fraction [LVEF]: 47%) followed for a median of 6.3 years, 49 patients (11.2%) experienced the primary outcome. On multivariable analysis, PIZ mass and core infarct mass were independently associated with the primary outcome (per gram: HR: 1.07 [95% CI: 1.02-1.12]; P = 0.002 and HR: 1.03 [95% CI: 1.01-1.05]; P = 0.01, respectively), and the addition of both parameters improved discrimination of the model (Harrell's C-statistic: 0.64-0.79). PIZ mass, however, did not provide incremental prognostic value over core infarct mass based on Harrell's C-statistic or risk reclassification analysis. Severely reduced LVEF did not predict the primary endpoint after adjustment for scar mass. On scar microstructure analysis, the number of LGE islands in addition to scar transmurality, radiality, interface area, and entropy were all associated with the primary outcome after adjustment for severely reduced LVEF and New York Heart Association functional class of >1. No scar microstructure feature remained associated with the primary endpoint when PIZ mass and core infarct mass were added to the regression models.

CONCLUSIONS

Comprehensive LGE characterization independently predicted SCD risk beyond conventional predictors used in implantable cardioverter-defibrillator (ICD) insertion guidelines. These results signify the potential for a more personalized approach to determining ICD candidacy in CAD.

Stereotactic Arrhythmia Radioablation Treatment of Ventricular Tachycardia: Current Technology and Evolving Indications

Ventricular tachycardia in patients with structural heart disease is a significant cause of morbidity and mortality. According to current guidelines, cardioverter defibrillator implantation, antiarrhythmic drugs, and catheter ablation are established therapies in the management of ventricular arrhythmias but their efficacy is limited in some cases. Sustained ventricular tachycardia can be terminated by cardioverter-defibrillator therapies although shocks in particular have been demonstrated to increase mortality and worsen patients' quality of life. Antiarrhythmic drugs have important side effects and relatively low efficacy, while catheter ablation, even if it is actually an established treatment, is an invasive procedure with intrinsic procedural risks and is frequently affected by patients' hemodynamic instability. Stereotactic arrhythmia radioablation for ventricular arrhythmias was developed as bail-out therapy in patients unresponsive to traditional treatments. Radiotherapy has been mainly applied in the oncological field, but new current perspectives have developed in the field of ventricular arrhythmias. Stereotactic arrhythmia radioablation provides an alternative non-invasive and painless therapeutic strategy for the treatment of previously detected cardiac arrhythmic substrate by three-dimensional intracardiac mapping or different tools. Since preliminary experiences have been reported, several retrospective studies, registries, and case reports have been published in the literature. Although, for now, stereotactic arrhythmia radioablation is considered an alternative palliative treatment for patients with refractory ventricular tachycardia and no other therapeutic options, this research field is currently extremely promising.

Outcomes of early catheter ablation for ventricular tachycardia in adult patients with structural heart disease and implantable cardioverter-defibrillator: An updated systematic review and meta-analysis of randomized trials

Aims

Catheter ablation (CA) for ventricular tachycardia (VT) can improve outcomes in patients with ischemic cardiomyopathy. Data on patients with non-ischemic cardiomyopathy are scarce. The purpose of this systematic review and meta-analysis is to compare early CA for VT to deferred or no ablation in patients with ischemic or non-ischemic cardiomyopathy.

Methods and results

Studies were selected according to the following PICOS criteria: patients with structural heart disease and an implantable cardioverter-defibrillator (ICD) for VT, regardless of the antiarrhythmic drug treatment; intervention–early CA; comparison–no or deferred CA; outcomes–any appropriate ICD therapy, appropriate ICD shocks, all-cause mortality, VT storm, cardiovascular mortality, cardiovascular hospitalizations, complications, quality of life; published randomized trials with follow-up ≥12 months. Random-effect meta-analysis was performed. Outcomes were assessed using aggregate study-level data and reported as odds ratio (OR) or mean difference with 95% confidence intervals (CIs). Stratification by left ventricular ejection fraction (LVEF) was also done. Eight trials (n = 1,076) met the criteria. Early ablation was associated with reduced incidence of ICD therapy (OR 0.53, 95% CI 0.33–0.83, p = 0.005), shocks (OR 0.52, 95% CI 0.35–0.77, p = 0.001), VT storm (OR 0.58, 95% CI 0.39–0.85, p = 0.006), and cardiovascular hospitalizations (OR 0.67, 95% CI 0.49–0.92, p = 0.01). All-cause and cardiovascular mortality, complications, and quality of life were not different. Stratification by LVEF showed a reduction of ICD therapy only with higher EF (high EF OR 0.40, 95% CI 0.20–0.80, p = 0.01 vs. low EF OR 0.62, 95% CI 0.34–1.12, p = 0.11), while ICD shocks (high EF OR 0.54, 95% CI 0.25–1.15, p = 0.11 vs. low EF OR 0.50, 95% CI 0.30–0.83, p = 0.008) and hospitalizations (high EF OR 0.95, 95% CI 0.58–1.58, p = 0.85 vs. low EF OR 0.58, 95% CI 0.40–0.82, p = 0.002) were reduced only in patients with lower EF.

Conclusion

Early CA for VT in patients with structural heart disease is associated with reduced incidence of ICD therapy and shocks, VT storm, and hospitalizations. There is no impact on mortality, complications, and quality of life. (The review protocol was registered with INPLASY on June 19, 2022, #202260080).

Systematic review registration

[https://inplasy.com/], identifier [202260080].

Head-to-Head Comparison of T1 Mapping and Electroanatomical Voltage Mapping in Patients With Ventricular Arrhythmias

BACKGROUND

Electroanatomical voltage mapping (EAVM) has been compared with late gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR), which cannot delineate diffuse fibrosis. T1-mapping CMR overcomes the limitations of LGE-CMR, but it has not been directly compared against EAVM.

OBJECTIVES

This study aims to assess the relationship between left ventricular (LV) endocardial voltage obtained by EAVM and extracellular volume (ECV) obtained by T1 mapping.

METHODS

The study investigated patients who underwent endocardial EAVM for ventricular arrhythmias (CARTO 3, Biosense Webster) together with preprocedural contrast-enhanced T1 mapping (Ingenia 3T, Philips Healthcare). After image integration, EAVM datapoints were projected onto LGE-CMR and ECV-encoded images. Average values of unipolar voltage (UV), bipolar voltage (BV), LGE transmurality, and ECV were merged from corresponding cardiac segments (6 per slice) and pooled for analysis.

RESULTS

The analysis included data from 628 segments from 18 patients (57 ± 13 years of age, 17% females, LV ejection fraction 48% ± 14%, nonischemic/ischemic cardiomyopathy/controls: 8/6/4 patients). Based on the 95th and 5th percentile values obtained from the controls, ECV >33%, BV <2.9 mV, and UV <6.7 mV were considered abnormal. There was a significant inverse association between voltage and ECV, but only in segments with abnormal ECV. Increased ECV could predict abnormal BV and UV with acceptable accuracy (area under the curve of 0.78 [95% CI: 0.74-0.83] and 0.84 [95% CI: 0.79-0.88]).

CONCLUSIONS

This study found a significant inverse relationship between LV endocardial voltage and ECV. Real-time integration of T1 mapping may guide catheter mapping and may allow identification of areas of diffuse fibrosis potentially related to ventricular arrhythmias.

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

OBJECTIVES

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Diagnostic potential of non-invasive mapping in the treatment of ventricular tachycardia in a patient with postinfarction scar: a case report

A case report of ventricular tachycardia (VT) treatment in a patient after myocardial infarction using non-invasive real-time electrophysiological mapping is presented. This clinical observation demonstrates the diagnostic possibilities of non-invasive mapping in the treatment of VT with hemodynamic instability. Non-invasive mapping can be used as a method for visualizing the early activation and slow conduction zones in hemodynamically instable VT, when effective endocardial mapping is not possible.

Important tips reflected in our daily practice from the American College of Cardiology Electrophysiology Council report on premature ventricular contractions

Premature ventricular contractions (PVCs) is one of the most common situations in the current cardiology practice. Although PVCs are generally benign in people without any structural heart disease, they may be associated with left ventricular dysfunction, cardiomyopathy, and, rarely, sudden death. Recently, there has been a considerable research in the pathophysiology of PVC, several clinical presentations in different situations, new proposals of successful diagnostic methods, and treatment modalities. Finally, the American College of Cardiology Electrophysiology Council has published a special report that deals with all the aspects of PVC. We reviewed the important points from this report that can be reflected in our daily practice.

Contact-force monitoring increases accuracy of right ventricular voltage mapping avoiding “false scar” detection in patients with no evidence of structural heart disease

Purpose

Electroanatomical mapping (EAM) could increase cardiac magnetic resonance imaging (CMR) sensitivity in detecting ventricular scar. Possible bias may be scar over-estimation due to inadequate tissue contact. Aim of the study is to evaluate contact-force monitoring influence during EAM, in patients with idiopathic right ventricular arrhythmias.

Methods

20 pts (13 M; 43 ± 12 y) with idiopathic right ventricular outflow tract (RVOT) arrhythmias and no structural abnormalities were submitted to Smarttouch catheter Carto3 EAM. Native maps included points collected without considering contact-force. EAM scar was defined as area ≥1 cm² including at least 3 adjacent points with signal amplitude (bipolar <0.5 mV, unipolar 3,5 mV), surrounded by low-voltage border zone. EAM were re-evaluated offline, removing points collected with contact force <5 g. Finally, contact force-corrected maps were compared to the native ones.

Results

An EAM was created for each patient (345 ± 85 points). After removing poor contact points, a mean of 149 ± 60 points was collected. The percentage of false scar, collected during contact force blinded mapping compared to total volume, was 6.0 ± 5.2% for bipolar scar and 7.1 ± 5.9% for unipolar scar, respectively. No EAM scar was present after poor contact points removal. Right ventricular areas analysis revealed a greater number of points with contact force < 5 g acquired in free wall, where reduced mean bipolar and unipolar voltage were recorded.

Conclusions

To date this is the first work conducted on structurally normal hearts in which contact-force significantly increases EAM accuracy, avoiding “false scar” related to non-adequate contact between catheter and tissue.

Premature ventricular complexes: diagnostic and therapeutic considerations in clinical practice : A state-of-the-art review by the American College of Cardiology Electrophysiology Council

Premature ventricular complexes (PVCs) are common arrhythmias in the clinical setting. PVCs in the structurally normal heart are usually benign, but in the presence of structural heart disease (SHD), they may indicate increased risk of sudden death. High PVC burden may induce cardiomyopathy and left ventricular (LV) dysfunction or worsen underlying cardiomyopathy. Sometimes PVCs may be a marker of underlying pathophysiologic process such as myocarditis. Identification of PVC burden is important, since cardiomyopathy and LV dysfunction can reverse after catheter ablation or pharmacological suppression. This state-of-the-art review discusses pathophysiology, clinical manifestations, how to differentiate benign and malignant PVCs, PVCs in the structurally normal heart, underlying SHD, diagnostic procedures (physical examination, electrocardiogram, ambulatory monitoring, exercise testing, echocardiography, cardiac magnetic resonance imaging, coronary angiography, electrophysiology study), and treatment (lifestyle modification, electrolyte imbalance, medical, and catheter ablation).

Evaluation of the reentry vulnerability index to predict ventricular tachycardia circuits using high-density contact mapping

Background

Identifying arrhythmogenic sites to improve ventricular tachycardia (VT) ablation outcomes remains unresolved. The reentry vulnerability index (RVI) combines activation and repolarization timings to identify sites critical for reentrant arrhythmia initiation without inducing VT.

Objective

The purpose of this study was to provide the first assessment of RVI’s capability to identify VT sites of origin using high-density contact mapping and comparison with other activation-repolarization markers of functional substrate.

Methods

Eighteen VT ablation patients (16 male; 72% ischemic) were studied. Unipolar electrograms were recorded during ventricular pacing and analyzed offline. Activation time (AT), activation–recovery interval (ARI), and repolarization time (RT) were measured. Vulnerability to reentry was mapped based on RVI and spatial distribution of AT, ARI, and RT. The distance from sites identified as vulnerable to reentry to the VT site of origin was measured, with distances <10 mm and >20 mm indicating accurate and inaccurate localization, respectively.

Results

The origins of 18 VTs (6 entrainment, 12 pace-mapping) were identified. RVI maps included 1012 (408–2098) (median, 1st–3rd quartiles) points per patient. RVI accurately localized 72.2% VT sites of origin, with median distance of 5.1 (3.2–10.1) mm. Inaccurate localization was significantly less frequent for RVI than AT (5.6% vs 33.3%; odds ratio 0.12; P = .035). Compared to RVI, distance to VT sites of origin was significantly larger for sites showing prolonged RT and ARI and were nonsignificantly larger for sites showing highest AT and ARI gradients.

Conclusion

RVI identifies vulnerable regions closest to VT sites of origin. Activation-repolarization metrics may improve VT substrate delineation and inform novel ablation strategies.

Mapping and Ablation of Unmappable Ventricular Tachycardia, Ventricular Tachycardia Storm, and Those in Acute Myocardial Infarction

In stable ventricular tachycardia (VT), activation mapping and entrainment mapping are the most important strategies to describe the reentrant circuit and its critical components. In many patients, however, VT is noninducible or hemodynamically unstable and unmappable. Several technological advances have broadened ablation options in unmappable VTs. Preprocedural imaging and intraprocedural imaging play an important role in location and extent of the substrate. Electroanatomic mapping with several technological improvements allows more precise electrical assessment of the substrate. A combination of imaging and electroanatomic mapping allows substantial modification of arrhythmogenic substrate in sinus rhythm or during device pacing without hemodynamic compromise.

Use of Contemporary Imaging Techniques for Electrophysiological and Device Implantation Procedures

Recent technological advances in cardiac imaging allow the visualization of anatomic details up to millimeter size in 3-dimensional format. Thus, it is not surprising that electrophysiologists increasingly rely upon cardiac imaging for the diagnosis, treatment, and subsequent management of patients affected by various arrhythmic disorders. Cardiac imaging methods reviewed in the present work involve: 1) the prediction of arrhythmic risk for sudden cardiac death in patients with heart disease; 2) catheter ablation of atrial fibrillation or ventricular tachycardia; and 3) cardiac resynchronization therapy. Future integration of diagnostic and interventional cardiac imaging will further increase the effectiveness of cardiac electrophysiological procedures and will help in delivering patient-specific therapies with ablation and cardiac implantable electronic devices.

What Cannot be Missed: Must-read Papers, 2018

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