Contact Force Monitoring for Cardiac Mapping in Patients with Ventricular Tachycardia

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Impact of artificial intelligence arrhythmia mapping on time to first ablation, procedure duration, and fluoroscopy use

INTRODUCTION

Artificial intelligence (AI) ECG arrhythmia mapping provides arrhythmia source localization using 12-lead ECG data; whether this information impacts procedural efficiency is unknown. We performed a retrospective, case-control study to evaluate the hypothesis that AI ECG mapping may reduce time to ablation, procedural duration, and fluoroscopy.

MATERIALS AND METHODS

Cases in which system output was used were retrospectively enrolled according to IRB-approved protocols at each site. Matched control cases were enrolled in reverse chronological order beginning on the last day for which the technology was unavailable. Controls were matched based upon physician, institution, arrhythmia, and a predetermined complexity rating. Procedural metrics, fluoroscopy data, and clinical outcomes were assessed from time-stamped medical records.

RESULTS

The study group consisted of 28 patients (age 65 ± 11 years, 46% female, left atrial dimension 4.1 ± 0.9 cm, LVEF 50 ± 18%) and was similar to 28 controls. The most common arrhythmia types were atrial fibrillation (n = 10), premature ventricular complexes (n = 8), and ventricular tachycardia (n = 6). Use of the system was associated with a 19.0% reduction in time to ablation (133 ± 48 vs. 165 ± 49 min, p = 0.02), a 22.6% reduction in procedure duration (233 ± 51 vs. 301 ± 83 min, p < 0.001), and a 43.7% reduction in fluoroscopy (18.7 ± 13.3 vs. 33.2 ± 18.0 min, p < 0.001) versus controls. At 6 months follow-up, arrhythmia-free survival was 73.5% in the study group and 63.3% in the control group (p = 0.56).

CONCLUSION

Use of forward-solution AI ECG mapping is associated with reductions in time to first ablation, procedure duration, and fluoroscopy without an adverse impact on procedure outcomes or complications.

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

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

Catheter ablation of ventricular tachycardia: strategies to improve outcomes

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

Is catheter-tissue contact force value important for ablation of ventricular arrhythmias originating from the left ventricular papillary muscles?

Background

Good catheter-tissue contact is mandatory to create effective ablation lesions. The minimal contact force value for ablation of arrhythmias originating from the left ventricle is 8.0-10.0 grams but is not known for arrhythmias arising from papillary muscles.

Purpose

To analyze contact force values during successful ablation procedures of arrhythmias originating from the left ventricular papillary muscles.

Methods

24 consecutive patients (mean age 57.9 ± 11.9 years, 16 males) underwent ablation of premature ventricular complexes originating from left ventricular papillary muscles with the use of CARTO electro-anatomical system and intracardiac echocardiography.

Results

Acute complete abolition of ventricular ectopy was obtained in 23 (96%) patients. The fluoroscopy time was 3.9 ± 3.5 min and procedure duration - 114.8 ± 37.9 min. The mean contact force during successful ablations was 3.0 ± 1.1 grams and 3.18 ± 1.8 grams for antero-lateral and postero-medial papillary muscle, respectively (NS). The mean contact force during a single unsuccessful ablation was 3.0 grams. At control Holter ECG, the mean Ectopy Burden was Reduced in the Antero-Lateral Papillary Muscle Group from 18.0% ± 7.9% to 2.6% ± 2.9% (p = 0.005415) and in the Postero-Medial Papillary Muscle Group - from 34.8% ± 13.7%-1.7% ± 1.3% (p = 0.012694). During Median 27 (IQR: 17-34) Months of Follow-up There one Recurrence of Arrhythmia.

Conclusion

The values of contact force for successful ablation of ventricular ectopy originating from the left ventricular papillary muscles may be much lower than those for ablation of other foci which questions the role of contact force measurement when ablating these arrhythmias.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Contact Force-Sensing versus Standard Catheters in Non-Fluoroscopic Radiofrequency Catheter Ablation of Idiopathic Outflow Tract Ventricular Arrhythmias

Background: Adequate contact between the catheter tip and tissue is important for optimal lesion formation and, in some procedures, it has been associated with improved effectiveness and safety. We evaluated the potential benefits of contact force-sensing (CFS) catheters during non-fluoroscopic radiofrequency catheter ablation (NF-RFCA) of idiopathic ventricular arrhythmias (VAs) originating from outflow tracts (OTs). Methods: A group of 102 patients who underwent NF-RFCA (CARTO, Biosense Webster Inc., Irvine, CA, USA) of VAs from OTs between 2014 to 2018 was retrospectively analyzed. Results: We included 52 (50.9%) patients in whom NF-RFCA was performed using CFS catheters and 50 (49.1%) who were ablated using standard catheters. Arrhythmias were localized in the right and left OT in 70 (68.6%) and 32 (31.4%) patients, respectively. The RFCA acute success rate was 96.1% (n = 98) and long-term success during a minimum 12-month follow-up (mean 51.3 ± 21.6 months) was 85.3% (n = 87), with no difference between CFS and standard catheters. There was no difference in complications rate between CFS (n = 1) and standard catheter (n = 2) ablations. Conclusions: There is no additional advantage of CFS catheters use over standard catheters during NF-RFCA of OT-VAs in terms of procedural effectiveness and safety.

Characteristics and outcomes of ventricular tachycardia and premature ventricular contractions ablation in patients with prior mitral valve surgery

BACKGROUND

Data regarding ventricular tachycardia (VT) or premature ventricular complex (PVC) ablation following mitral valve surgery (MVS) is limited. Catheter ablation (CA) can be challenging given perivalvular substrate in the setting of mitral annuloplasty or prosthetic valves.

OBJECTIVE

To investigate the characteristics, safety, and outcomes of radiofrequency CA in patients with prior MVS and ventricular arrhythmias (VA).

METHODS

We identified consecutive patients with prior MVS who underwent CA for VT or PVC between January 2013 and December 2018. We investigated the mechanism of arrhythmia, ablation approach, peri-operative complications, and outcomes.

RESULTS

In our cohort, 31 patients (77% men, mean age 62.3 ± 10.8 years, left ventricular ejection fraction 39.2 ± 13.9%) with prior MVS underwent CA (16 VT; 15 PVC). Access to the left ventricle was via transseptal approach in 17 patients, and a retrograde aortic approach was used in 13 patients. A combined transseptal and retrograde aortic approach was used in one patient, and a percutaneous epicardial approach was combined with trans-septal approach in one patient. Heterogenous scar regions were present in 94% of VT patients and scar-related reentry was the dominant mechanism of VT. Forty-seven percent of PVC patients had abnormal substrate at the site targeted for ablation. Clinical VA substrates involved the peri-mitral area in six patients with VT and five patients with PVC ablation. No procedure-related complications were reported. The overall recurrence-free rate at 1-year was 72.2%; 67% in the VT group and 78% in the PVC group. No arrhythmia-related death was documented on long-term follow-up.

CONCLUSION

CA of VAs can be performed safely and effectively in patients with MVS.

Characterization of the electrophysiological substrate in patients with Barlow's disease

BACKGROUND

Myxomatous mitral valve prolapse (MVP) and mitral-annular disjunction (Barlow disease) are at-risk for ventricular arrhythmias (VA). Fibrosis involving the papillary muscles and/or the infero-basal left ventricular (LV) wall was reported at autopsy in sudden cardiac death (SCD) patients with MVP.

OBJECTIVES

We investigated the electrophysiological substrate subtending VA in MVP patients with Barlow disease phenotype.

METHODS

Twenty-three patients with VA were enrolled, including five with syncope and four with a history of SCD. Unipolar (Uni < 8.3 mV) and bipolar (Bi < 1.5 mV) low-voltage areas were analyzed with electro-anatomical mapping (EAM), and VA inducibility was evaluated with programmed ventricular stimulation (PES). Electrophysiological parameters were correlated with VA patterns, electrocardiogram (ECG) inferior negative T wave (nTW), and late gadolinium enhancement (LGE) assessed by cardiac magnetic resonance.

RESULTS

Premature ventricular complex (PVC) burden was 12 061.9 ± 12 994.6/24 h with a papillary-muscle type (PM-PVC) in 18 patients (68%). Twelve-lead ECG showed nTW in 12 patients (43.5%). A large Uni less than 8.3 mV area (62.4 ± 45.5 cm² ) was detected in the basal infero-lateral LV region in 12 (73%) patients, and in the papillary muscles (2.2 ± 2.9 cm² ) in 5 (30%) of 15 patients undergoing EAM. A concomitant Bi less than 1.5 mV area (5.0 ± 1.0 cm² ) was identified in two patients. A history of SCD, and the presence of nTW, and LGE were associated with a greater Uni less than 8.3 mV extension: (32.8 ± 3.1 cm² vs. 9.2 ± 8.7 cm² ), nTW (20.1 ± 11.0 vs. 4.1 ± 3.8 cm² ), and LGE (19.2 ± 11.7 cm² vs. 1.0 ± 2.0 cm² , p = .013), respectively. All patients with PM-PVC had a Uni less than 8.3 mV area. Sustained VA (ventricular tachycardia 2 and VF 2) were induced by PES only in four patients (one with resuscitated SCD).

CONCLUSIONS

Low unipolar low voltage areas can be identified with EAM in the basal inferolateral LV region and in the papillary muscles as a potential electrophysiological substrate for VA and SCD in patients with MVP and Barlow disease phenotype.

Similar outcomes with manual contact force ablation catheters and traditional catheters in the treatment of outflow tract premature ventricular complexes

Aims

Unlike in atrial fibrillation ablation, there is a lack of appropriately sized and properly designed studies regarding outflow tract (OT) premature ventricular complex (PVC) ablation outcomes with contact force sensing (CFS) catheters. We aimed to compare the acute success-, complication-, and long-term recurrence rates of manual CFS catheters with traditional irrigated catheters (T) in OT PVC ablation.

Methods and results

Single-centre, propensity-matched data of 75–75 patients ablated for right-sided OT (RVOT) or left-sided OT (LVOT) PVCs in 2015–17 with CFS or T catheters were compared. Acute success rate, peri-procedural complications, post-procedural daily PVC burden, and long-term recurrence rates were compared on intention-to-treat basis. Acute success rate equalled 80% in both groups, with no difference in force values in the CFS group comparing successful or failed cases [12.0 (8.75–17.0) vs. 16.0 (10.25–22.25) g, P = 0.21]. There were three cases of pseudo-aneurysm and one cardiac tamponade. PVC burden fell significantly from baseline 22 (15–30)% to 2 (0–10)% (P < 0.0001), with no difference between catheter types [CFS: 1 (0–7)% vs. T: 4 (1–12) %; P = 0.21]. There was no significant difference in recurrence-free survival of CFS and T catheters (58 vs. 59%, P = 0.29) during 12 months of follow-up, respectively. Recurrence in the CFS group did not differ either by the force exerted below or above the median value of 12 g (P = 0.66).

Conclusion

Both types of catheters can effectively reduce OT PVC burden with minimal serious complication rates. Ablation with CFS or T catheters gives similar acute- and long-term results.

Contact force sensors in minimally invasive catheters: current and future applications

INTRODUCTION

Advances in catheter design for minimally invasive surgery have brought about the incorporation of contact force (CF) sensors in catheters. Two main approaches to achieve CF sensing at the catheter end-effector consist of fiber optic or magnetic solutions. CF sensing feedback can be used to assist in ablation procedures, mapping cardiac regions, identifying tissue characteristics, and enhancing robotic catheter control.

AREAS COVERED

This review covers the technological and clinical aspects of CFS in catheters. Contact force and force-time integral thresholds for ablation procedures, procedural complications, and electroanatomical mapping strategies are discussed. Future applications of improving catheter control, minimizing complications, and enhancing mapping techniques through CF are examined.

EXPERT OPINION

Fiber optic CF catheters may be more desirable compared to magnetic modalities due to the lower cost, compactness, and higher accuracy. In ablation procedures, complications due to higher ablation duration, power, contact force, and force time can be reduced through practical experience and informed training for catheter operators. Future prospects consist of the incorporation of CF sensors with remote catheter systems to assist in catheter control. We propose that CF can also be used in machine learning decision-making algorithms to prevent complications or improve tissue characterization.

Updates in Ventricular Tachycardia Ablation

Sudden cardiac death (SCD) due to recurrent ventricular tachycardia is an important clinical sequela in patients with structural heart disease. As a result, ventricular tachycardia (VT) has emerged as a major clinical and public health problem. The mechanism of VT is predominantly mediated by re-entry in the presence of arrhythmogenic substrate (scar), though focal mechanisms are also important. Catheter ablation for VT, when compared to standard medical therapy, has been shown to improve VT-free survival and burden of device therapies. Approaches to VT ablation are dependent on the underlying disease process, broadly classified into idiopathic (no structural heart disease) or structural heart disease (ischemic or non-ischemic heart disease). This update aims to review recent advances made for the treatment of VT ablation, with respect to current clinical trials, peri-procedure risk assessments, pre-procedural cardiac imaging, electro-anatomic mapping and advances in catheter and non-catheter based ablation techniques.

Patient Selection for Epicardial Ablation-Part II: The Epicardial Approach and Current Challenges Associated with Epicardial Ablation

Since their inception, percutaneous epicardial approaches have become increasingly common in clinical practice with the advent of new technology and the growth of catheter ablation for both ventricular and supraventricular arrhythmias. In addition to identifying the arrhythmogenic foci, there remain challenges to successful epicardial ablation such as the choice of energy source, optimizing irrigation during ablation, and anatomic barriers such as epicardial fat and coronary vessels. The performance of continued translational studies to understand how each of these factors contribute to lesion formation will be essential to guide future advances in the field of epicardial ablation.

Contact feedback improves 1-year outcomes of remote magnetic navigation-guided ischemic ventricular tachycardia ablation

INTRODUCTION

Remote magnetic navigation (RMN)-guided catheter ablation (CA) is a feasible treatment option for patients presenting with ischemic ventricular tachycardia (VT). Catheter-tissue contact feedback, enhances lesion formation and may consequently improve CA outcomes. Until recently, contact feedback was unavailable for RMN-guided CA. The novel e-Contact Module (ECM) was developed to continuously monitor and ensure catheter-tissue contact during RMN-guided CA.

OBJECTIVE

The present study aims to evaluate the effect of ECM implementation on acute and long-term outcomes in RMN-guided ischemic VT ablation.

METHOD

This retrospective, two-center study included consecutive ischemic VT patients undergoing RMN-guided CA from 2010 to 2017. Baseline clinical data, procedural data, including radiation times, and acute success rates were compared between CA procedures performed with ECM (ECM+) and without ECM (ECM-). One-year VT-free survival was analyzed using Cox-proportional hazards models, adjusting for potential confounders: age, left ventricular function, VT inducibility at baseline and substrate based ablation strategy.

RESULTS

The current study included 145 patients (ECM+ N = 25, ECM- N = 120). Significantly lower fluoroscopy times were observed in the ECM+ group (9.5 (IQR 5.3-13.5) versus 12.5 min (IQR 8.0-18.0), P = 0.025). Non-inducibility of the clinical VT at the end of procedure was observed in 92% ECM+ versus 72% ECM- patients (P = 0.19). ECM guidance was associated with significantly lower VT-recurrence rates during 1-year follow-up (16% ECM+ versus 40% ECM-; multivariable HR 0.29, 95%-CI 0.10-0.69, P = 0.021, reference group: ECM-).

CONCLUSION

Contact feedback by the ECM further decreases fluoroscopy exposure and improves VT-free survival in RMN-guided ischemic VT ablation.

Percutaneous Epicardial Approach to Catheter Ablation of Cardiac Arrhythmias

Since their introduction >2 decades ago, percutaneous catheter-based epicardial mapping and ablation have become widely adopted by cardiac electrophysiologists around the world. Although epicardial mapping has been used for catheter ablation of a wide variety of cardiac arrhythmias, its most common use is for ablation of intramural and subepicardial substrates that give rise to ventricular tachycardia, particularly in patients with nonischemic cardiomyopathy. As such, the subxiphoid percutaneous epicardial approach has emerged as an important adjunct, and, in some cases, is the preferred strategy in this regard. This review discusses the rationale and indications for epicardial catheter mapping and/or ablation. This paper also reviews the prevalence of epicardial arrhythmias and their electrocardiographic criteria. In addition, it examines the anatomy of the pericardium and commonly used epicardial access techniques, as well as the optimal methodologies for epicardial mapping and ablation and the impact of epicardial fat. Finally, this review discusses the potential of the various complications associated with the percutaneous epicardial approach, in addition to patient-specific risk factors, and potential strategies to mitigate the risk of complications.

Role of Contact Force Sensing in Catheter Ablation of Cardiac Arrhythmias: Evolution or History Repeating Itself?

Adequate catheter-tissue contact facilitates efficient heat energy transfer to target tissue. Tissue contact is thus critical to achieving lesion transmurality and success of radiofrequency (RF) ablation procedures, a fact recognized more than 2 decades ago. The availability of real-time contact force (CF)-sensing catheters has reinvigorated the field of ablation biophysics and optimized lesion formation. The ability to measure and display CF came with the promise of dramatic improvement in safety and efficacy; however, CF quality was noted to have just as important an influence on lesion formation as absolute CF quantity. Multiple other factors have emerged as key elements influencing effective lesion formation, including catheter stability, lesion contiguity and continuity, lesion density, contact homogeneity across a line of ablation, spatiotemporal dynamics of contact governed by cardiac and respiratory motion, contact directionality, and anatomic wall thickness, in addition to traditional ablation indices of power and RF duration. There is greater appreciation of surrogate markers as a guide to lesion formation, such as impedance fall, loss of pace capture, and change in unipolar electrogram morphology. In contrast, other surrogates such as tactile feedback, catheter motion, and electrogram amplitude are notably poor predictors of actual contact and lesion formation. This review aims to contextualize the role of CF sensing in lesion formation with respect of the fundamental principles of biophysics of RF ablation and summarize the state-of-the-art evidence behind the role of CF in optimizing lesion formation.

Retrograde aortic access during ventricular tachycardia ablation: Indications, techniques, and challenges

The retrograde aortic (RA) route is a widely used access route for mapping and ablation of ventricular tachycardias (VT) arising from the left ventricular endocardium. With the expanding role of VT ablation in patients with significant comorbidity, the choice between the RA and transseptal access routes is an increasingly important consideration. An individualized decision based on the location of the arrhythmogenic substrate, vascular anatomy, aortic valve morphology, and operator experience is necessary when deciding on the optimal access route. Among patients with challenging vascular anatomy, growing experience from structural interventions such as transcatheter aortic valve replacements and peripheral vascular interventions has provided valuable insights into techniques for safe retrograde access. The present review focuses on patient selection for RA access, potential complications associated with the technique, and optimal approaches for access in patients with challenging vascular or aortic valve anatomy.

Endo/epicardial ablation of ventricular arrhythmias with contact force-sensing catheters in arrhythmogenic right ventricular dysplasia/cardiomyopathy

Objective:

To control ventricular arrhythmia in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C), ablation may be required both from the endocardial and epicardial side. In this study, we analyzed the results of contact force–sensing (CFS) catheters in the endo/epicardial ablation of ventricular arrhythmias in ARVD/C.

Methods:

We included 17 patients with ARVD/C, 5 of whom had premature ventricular contractions (PVC), and the rest of them were admitted with a ventricular tachycardia (VT) storm, between September 2014 and October 2016. We divided patients into two groups: the PVC and VT groups. Irrigated CFS catheters (Smart Touch, Biosense Webster, Inc.) were utilized in all procedures.

Results:

In the PVC group, the mean ratio of PVC during the 24-hour Holter monitoring was 31.8±7.6%. The mean contact force during mapping and ablation in the right ventricle was 13±1.2 and 12.8±1.9 grams, respectively. The mean follow-up duration was 15±3.1 months for the PVC group. The left ventricular ejection fraction improved in all patients (52.8±10%). All patients in the VT group underwent endo/epicardial ablation, except one. The mean contact force during the endocardium and epicardium mapping was 12.5±1.2 and 12.5±4.6 grams, respectively. The mean contact force during ablation for the endocardium and epicardium was 12.1±1.4 and 12.8±1.9 grams, respectively. All clinical and non-clinical VTs were ablated successfully, except in 2 patients who still had non-clinical VTs. The mean follow-up was 15.5±4.5 months. None of the VT patients experienced electrical storm or death. Two patients had single shock, and 1 patient had two shocks during the follow-up.

Conclusion:

Endo/epicardial ablation of ventricular arrhythmias with CFS catheters in ARVD/C seems to be promising.

Acute and one year outcome of premature ventricular contraction ablation guided by contact force and automated pacemapping software

BACKGROUND

Radiofrequency (RF) ablation is a well-established approach to treat premature ventricular contractions (PVC) and is associated with good outcomes.

AIM

The present study sought to analyze the acute efficacy and 1-year outcomes of PVC ablation using RF technology with an approach based on automated pace-mapping and contact force (CF) information.

METHODS

Sixty-one consecutive patients (52.4% males, age 45.9 ± 12.5) underwent catheter ablation for symptomatic monomorphic PVC. All procedures were guided by a 3-dimensional mapping system; site of ablation was selected based on PASO™ aided pace-mapping; RF was started on the selected location when stable catheter position with >10 g of CF were obtained.The procedure was defined as acutely effective if the PVC was eliminated and it did not recur during within 30 minutes. Long-term efficacy was defined as a decrease by more than 95% at 1 year of the initial PVC burden at ECG Holter monitoring.

RESULTS

The PVC ablation was performed in the right ventricular outflow tract in 37 patients (60.7%), left ventricle in 15 patients (24.6%), coronary cusps in 6 patients (9.8%), right ventricle in 3 patients (4.9%); PVC ablation was acutely successful in 59 of patients (96.7%). At 1-year efficacy was obtained in 57 patients (93.4%). No major complications occurred. Mean procedural and fluoroscopy time were 94.5 ± 20.9 and 4.3 ± 2.5 minutes respectively.

CONCLUSION

Premature ventricular contraction RF ablation mainly guided by PASO™ and CF showed high success rate in both acute and 1-year follow-up (96.7% and 93.4% respectively). The best efficacy cut-off for RF ablation of PVCs has been identified in presence of both PASO™ ≥95% and CF >10 g.

Usefulness of Electroanatomical Mapping with Contact Force Monitoring for Accessory Pathways Ablation in Pediatric Population

The current approach for catheter ablation (CA) of accessory pathways (AP) includes the use of standard catheters under fluoroscopic visualization. We hypothesize that use of contact force (CF) irrigated tip catheters might increase procedural safety in pediatric patients compared to standard irrigated tip catheters, by decreasing the number of radiofrequency (RF) pulses required to obtain AP elimination. Seventy-one pediatric patients (13.7 ± 2.5 years, 45 male) with ventricular pre-excitation were enrolled in the study. CA was performed with a standard irrigated tip catheter up to June 2013 in 41 patients (Group S) and with a CF sensing irrigated tip catheter later on in 30 patients (Group CF). In the Group CF, RF was applied with a minimal CF of 5 g; CF > 35 g was avoided. Group CF procedures required less fluoroscopy (6.8 ± 4.8 min), compared to Group S (12.2 ± 10.8 min, p = 0.007). The number of RF pulses was smaller in Group CF compared to Group S (2.5 ± 2.0 vs 5.5 ± 1.9, p < 0.01). The mean CF during the effective RF pulse was 18 ± 7.7 g, force-time integral was 1040.7 ± 955.9 gs, Ablation Index was 513.0 ± 214.2. The procedure was acutely successful in 70 patients; at 12 months follow-up 2 patients had AP recurrence, one for each group. No major complications were reported. The use of CF irrigated tip catheters was associated with a smaller number of RF pulses and less fluoroscopy, as compared to mapping and ablation with standard irrigated tip catheters.

Substrate Mapping and Ablation for Ventricular Tachycardia in Patients with Structural Heart Disease: How to Identify Ventricular Tachycardia Substrate

Catheter ablation for ventricular tachycardia (VT) has been increasingly used over the past two decades in patients with structural heart disease (SHD). In these individuals, a substrate mapping strategy is being more commonly applied to identify targets for VT ablation, which has been shown to be more effective versus targeting mappable VTs alone. There are a number of substrate mapping methods in existence that aim to explore potential VT isthmuses, although their success rates vary. Most of the reported electrogram-based mapping studies have been performed with ablation catheters; meanwhile, the use of multipolar mapping catheters with smaller electrodes and closer interelectrode spacing has emerged, which allows for an assessment of detailed near-field abnormal electrograms at a higher resolution. Another recent advancement has occurred in the use of imaging techniques in VT ablation, particularly in refining the substrate. The goal of this paper is to review the key developments and limitations of current mapping strategies of substrate-based VT ablation and their outcomes. In addition, we briefly summarize the role of cardiac imaging in delineating VT substrate.

Contact Forces Required to Record Monophasic Action Potentials: A Complement to Catheter Contact Force Measurement

OBJECTIVE

The ability to monitor catheter contact force (CF) plays a major role in assessing radiofrequency ablation, impacting lesion size and arrhythmia recurrence, and dictating ablation duration and/or overall patient safety. Our study sought to determine the relative CFs required to elicit reproducible monophasic action potential (MAP) recordings.

METHODS

The study utilized four swine in which: first, median sternotomies were performed and MAPs were collected from seven ventricular locations on the epicardial surface of each heart; and second, a subset of endocardial signals was recorded from a reanimated heart. In these studies, the initial elicitation and then loss of stable MAP waveforms were recorded, as were their associated catheter CFs (n = 371).

RESULTS

Mean CF at the onset of stable MAP recordings was 14.2 ± 2.9 g for epicardial and 16.6 ± 2.5 g for endocardial locations. Across epicardial locations, no significant differences in CF were required to elicit MAPs. Additionally, endocardial and epicardial CFs for MAPs did not significantly differ for respective locations, i.e., right ventricular septum endocardial versus epicardial. In our study, the catheter CFs required to elicit MAPs were within optimal ranges previously reported for eliciting clinically viable radiofrequency ablations.

CONCLUSION

We believe that MAP recordings could complement CF measurements with electrical data, providing additional clinical feedback for physicians performing cardiac ablation.

SIGNIFICANCE

If applied clinically, MAP recordings could potentially improve ablation outcomes in patients with cardiac arrhythmias.

Ablation of recurrent malignant idiopathic ventricular tachycardia: When proper diagnosis and success is a matter of contact

Effective and stable contact between the catheter tip and the tissue is crucial for both mapping and lesion formation during cardiac ablation procedures. Contact force catheter may be not only a therapeutic approach to arrhythmias, but also a tool for achieving accurate characterization of the arrhythmic substrate.

Ventricular tachycardia ablation in structural heart disease: Impact of ablation strategy and non-inducibility as an end-point on long term outcome

BACKGROUND

To investigate the long term outcomes after catheter ablation (CA) of ventricular tachycardia (VT) in the context of structural heart disease in a multicenter cohort. The impact of different ablation strategies (substrate ablation versus activation guided versus combined) and non-inducibility as an end-point was evaluated.

METHODS

Data was pooled from prospective registries at 5 centres over a 5 year period. Success was defined as survival free from recurrent ventricular arrhythmias (VA). Multivariate analysis of factors predicting survival free from VA was analysed by Cox regression.

RESULTS

Five hundred sixty-six patients underwent CA for VT. Patients were 64 ± 15 years. Left ventricular ejection fraction was 35 ± 15% and 66% had ischaemic heart disease. At 2.3 (IQR 1.0-4.2) years, success was achieved in 44% after a single procedure, rising to 60% after repeat procedures. Mortality at final follow up was 22%. Multivariate analysis showed that higher left ventricular ejection fraction, younger age, ischaemic heart disease, and non-inducibility of VA predicted long term survival free from VA (all p < 0.05). There was no impact of the approach to ablation.

CONCLUSION

CA eliminates VT in a large proportion of patients long term. Ablation strategy did not impact outcome and hence substrate ablation is a reasonable initial strategy. Non-inducibility of VA predicted survival free from VA and may be worth pursuing as a procedural end-point.

Ventricular Tachycardia in Ischemic Heart Disease

Ventricular arrhythmias are a significant cause of morbidity and mortality in patients with ischemic structural heart disease. Endocardial and epicardial mapping strategies include scar characterization channel identification, and recording and ablation of late potentials and local abnormal ventricular activities. Catheter ablation along with new technology and techniques of bipolar ablation, needle catheter, and autonomic modulation may increase efficacy in difficult to ablate ventricular arrhythmias. Catheter ablation of ventricular arrhythmias seem to confer mortality and morbidity benefits in patients with ischemic heart disease.

Evolution of Force Sensing Technologies

In order to Improve the procedural success and long-term outcomes of catheter ablation techniques for atrial fibrillation (AF), an Important unfulfilled requirement is to create durable electrophysiologically complete lesions. Measurement of contact force (CF) between the catheter tip and the target tissue can guide physicians to optimise both mapping and ablation procedures. Contact force can affect lesion size and clinical outcomes following catheter ablation of AF. Force sensing technologies have matured since their advent several years ago, and now allow the direct measurement of CF between the catheter tip and the target myocardium in real time. In order to obtain complete durable lesions, catheter tip spatial stability and stable contact force are important. Suboptimal energy delivery, lesion density/contiguity and/or excessive wall thickness of the pulmonary vein-left atrial (PV-LA) junction may result in conduction recovery at these sites. Lesion assessment tools may help predict and localise electrical weak points resulting in conduction recovery during and after ablation. There is increasing clinical evidence to show that optimal use of CF sensing during ablation can reduce acute PV re-conduction, although prospective randomised studies are desirable to confirm long-term favourable clinical outcomes. In combination with optimised lesion assessment tools, contact force sensing technology has the potential to become the standard of care for all patients undergoing AF catheter ablation.

Recent advances in the management of ventricular tachyarrhythmias

Ventricular arrhythmias are an important cause of cardiovascular morbidity and mortality, particularly in those with structural heart disease, inherited cardiomyopathies, and channelopathies. The goals of ventricular arrhythmia management include symptom relief, improving quality of life, reducing implantable cardioverter defibrillator shocks, preventing deterioration of left ventricular function, reducing risk of arrhythmic death, and potentially improving overall survival. Guideline-directed medical therapy and implantable cardioverter defibrillator implantation remain the mainstay of therapy to prevent sudden cardiac death in patients with ventricular arrhythmias in the setting of structural heart disease. Recent advances in imaging modalities and commercial availability of genetic testing panels have enhanced our mechanistic understanding of the disease processes and, along with significant progress in catheter-based ablative therapies, have enabled a tailored and more effective management of drug-refractory ventricular arrhythmias. Several gaps in our knowledge remain and require further research. In this article, we review the recent advances in the diagnosis and management of ventricular arrhythmias.

Clinical Aspects and Ablation of Ventricular Arrhythmias in Tetralogy of Fallot

Life expectancy of patients with rToF has considerably improved due to refined surgical interventions. Monomorphic fast VTs are frequently encountered in adult patients with rToF. The dominant substrate of VT is anatomical isthmuses bordered by surgical incisions, patch material and valve annuli. Substrate based ablation strategies aim to transect all slow conducting anatomical isthmuses (SCAI) as identified by electroanatomical mapping. Procedural success is defined as non-inducibility of VT and confirmed conduction block over the SCAI resulting in long-term VT free survival in most patients. The identification of SCAIs in rToF may have important implications for risk stratification and preventive treatment.

[3-D mapping and ablation of recurrent ventricular tachycardia in patients with ischemic cardiomyopathy]

Catheter ablation of ventricular tachycardia (VT) is an established therapy for patients with ischemic cardiomyopathy to reduce implantable cardioverter-defibrillator (ICD) interventions and is a class I recommendation in international guidelines. Numerous publications confirm its value. Use of three-dimensional mapping systems with or without image integration is standard for ablation of complex arrhythmias. In patients with history of myocardial infarction they help to understand activation of reentrant circuits and are prerequisite for substrate mapping. While a combination of activation and substrate mapping is performed in many patients based on clinical presentation, substrate-based ablation appears to be superior to clinical VT ablation alone.

Catheter Ablation of Ventricular Tachycardia in Patients With MitraClip Device: Preliminary Findings

INTRODUCTION

Patients with mitral regurgitation are increasingly treated by percutaneous implantation of a MitraClip device (Abbott Park, IL, USA). We investigate the feasibility and safety of the transmitral catheter route for catheter ablation of ventricular tachycardia (VT) in these patients.

METHODS

The mitral valve with the MitraClip in situ was crossed under transesophageal 3-dimensional echocardiographic and fluoroscopic guidance using a steerable sheath for ablation of the left ventricle.

RESULTS

Five patients (all males, median age 74.0 ± 16.0 years) who had previously a MitraClip implanted were referred for catheter ablation of VT. The left ventricular ejection fraction was 29.0% ± 24.0%. One patient had both an atrial septal defect and a left atrial appendage occluder device in addition to a MitraClip. The duration between MitraClip implantation and ablation was 1019.0 ± 783.0 days. After transseptal puncture, ablation catheter was successfully steered through the mitral valve with the use of fluoroscopy. A complete high-density map of the substrate in sinus rhythm could be obtained in all patients using multipolar mapping catheters. In 1 patient, mapping was carried out using a mini-basket catheter. Procedural endpoints, noninducibility of all VTs, and abolition of all late potentials were achieved in all patients. Procedure time was 255.0 ± 52.5 minute, fluoroscopy time was 23.0 ± 7.3, and the radiation dose was 61.0 ± 37.5 Gycm² . No mitral insufficiency or worsening of regurgitation was documented after the procedure.

CONCLUSIONS

This is the first report demonstrating the feasibility and safety of VT ablation in patients with a MitraClip device using the anterograde transmitral catheter route.

Epicardial Catheter Ablation of Ventricular Tachycardia

Over the last two decades, epicardial catheter ablation has evolved into a practical approach for treatment of ventricular tachycardia (VT). There are certain considerations when performing this procedure. First, presence of epicardial fat can diminish peak-to-peak electrogram amplitude and also impede radiofrequency energy delivery. Hence, epicardial VT ablation should be performed with cooled-tip radiofrequency using reduced irrigation flow within a relatively 'dry' pericardial milieu. Furthermore, catheter orientation is key when performing epicardial ablation. Lastly, hemo-pericardium remains the most common major adverse event of epicardial ablation and its presenting timeline may be used to identify the precise nature of this complication.

Ablation of ischemic ventricular tachycardia: evidence, techniques, results, and future directions

PURPOSE OF REVIEW

This article summarizes current understanding of the arrhythmia substrate and effect of catheter ablation for infarct-related ventricular tachycardia, focusing on recent findings.

RECENT FINDINGS

Clinical studies support the use of catheter ablation earlier in the course of ischemic disease with moderate success in reducing arrhythmia recurrence and shocks from implantable defibrillators, although mortality remains unchanged. Ablation can be lifesaving for patients presenting with electrical storm. Advanced mapping systems with image integration facilitate identification of potential substrate, and several different approaches to manage hemodynamically unstable ventricular tachycardia have emerged. Novel ablation techniques that allow deeper lesion formation are in development.

SUMMARY

Catheter ablation is an important therapeutic option for preventing or reducing episodes of ventricular tachycardia in patients with ischemic cardiomyopathy. Present technologies allow successful ablation in the majority of patients, even when the arrhythmia is hemodynamically unstable. Failure of the procedure is often because of anatomic challenges that will hopefully be addressed with technological progress.

Contact Force-Guided Deep Engagement with a Steerable Sheath in the Distal Great Cardiac Vein: A Case Report

Ablation of ventricular tachycardia originating from the great cardiac vein involves the difficult step of deep engagement with an ablation catheter. The catheter and a steerable sheath (MobiCath, Biosense Webster, Diamond Bar, CA, USA) were advanced alternately only when the contact force vector was parallel to the coronary venous system. Deep engagement with a steerable sheath ensured a powerful backup force during ablation.

Therapy for ventricular arrhythmias in structural heart disease: a multifaceted challenge

The unpredictable nature and potentially catastrophic consequences of ventricular arrhythmias (VAs) have obligated physicians to search for therapies to prevent sudden cardiac death (SCD). At present, a low left ventricular ejection fraction (LVEF) has been used as a risk factor to predict SCD in patients with structural heart disease and has been consistently adopted as the predominant, and sometimes sole, indication for implantable cardioverter defibrillator (ICD) therapy. Although the ICD remains the mainstay life-saving therapy for SCD, it does not modify the underlying arrhythmic substrate and may be associated with adverse effects from perioperative and long-term complications. Preventative pharmacological therapy has been associated with limited benefits, but anti-arrhythmic medications have significant side effects profiles. Catheter ablation of VAs has greatly evolved over the last few decades. Substrate mapping in sinus rhythm has allowed haemodynamically unstable VAs to be successfully treated. Both LVEF as an indication for ICD therapy and electro-anatomical mapping for substrate modification identify static components of underlying myocardial arrhythmogenicity. They do not take into account dynamic factors, such as the mechanisms of arrhythmia initiation and development of new anatomical or functional lines of block, leading to the initiation and maintenance of VAs. Dynamic factors are difficult to evaluate and consequently are not routinely used in clinical practice to guide treatment. However, progress in the treatment of VAs should consider and integrate dynamic factors with static components to fully characterize the myocardial arrhythmic substrate.

Substrate mapping for unstable ventricular tachycardia

The primary goal of catheter ablation of scar-related ventricular tachycardia (VT) is the interruption of critical areas of slow conduction responsible for the development and maintenance of the reentrant VT circuit. Most patients with scar-related VT present with unstable arrhythmias that are not amenable to interrogation from multiple sites to define the VT circuit based on the intracardiac activation sequence and the response to entrainment mapping. In order to effectively target unstable VTs, a number of ablation approaches have been described with the aim of targeting the abnormal substrate defined with mapping in sinus or paced rhythm. Some of these strategies (eg, late potential and local abnormal ventricular activity ablation or scar homogenization) target the entire abnormal substrate harboring abnormal electrograms, defined with a variety of different criteria. Scar dechanneling, linear ablation through sites matching VT with pacing, and the core isolation approach focus on more discrete regions within the abnormal substrate that have been proven relevant to the clinical and/or inducible arrhythmias by means of physiologic maneuvers, although this does not necessarily translate to fewer radiofrequency lesions to achieve the procedural end-point. Observational studies evaluating different substrate-based ablation techniques have reported fairly uniform arrhythmia-free survivals at short- and mid-term follow-up, although direct comparisons between different techniques are lacking. In this article, we summarize the different state-of-the-art substrate mapping and ablation approaches for targeting unstable VT, with a particular focus on the relative merits and limitations of the described techniques.

Safety and Clinical Outcome of Catheter Ablation of Ventricular Arrhythmias Using Contact Force Sensing: Consecutive Case Series

BACKGROUND

Poor catheter-to-myocardial contact can lead to ineffective ablation lesions and suboptimal outcome. Contact force (CF) sensing catheters in ventricular tachyarrhythmia (VT) ablations have not been studied for their long-term efficacy.

PURPOSE

The aim of this study was to compare CF ablation to manual ablation (MAN) and remote magnetic navigation (RMN) ablation for safety and efficacy in acute and long-term outcome.

METHODS

A total of 239 consecutive patients who underwent VT ablation with the use of MAN, CF, or RMN catheters were included in this single-center cohort study from January 2007 until March 2014. The primary endpoints were procedural success, acute major complications, and VT recurrences at follow-up. The median follow-up period was 25 months.

RESULTS

Acute success was achieved in 182 out of 239 procedures (76%). Acute success in manual ablation, CF ablation and RMN ablation was 71%, 71%, and 86%, respectively (P = 0.03). Major complications occurred in 3.3% and there were less major complications (P = 0.04) in the RMN group. After an initial successful procedure, 66 of 182 patients (36%) had a recurrence during follow-up. This was not significantly different between groups. Using an intention-to-treat analysis, 124 patients (52%) had a recurrence. The recurrence rate was lowest in the RMN group.

CONCLUSION

The use of CF sensing catheters did not improve procedural outcome or safety profile in comparison to non-CF sensing ablation in this observational study of ventricular arrhythmia ablations.

Contemporary Mapping Techniques of Complex Cardiac Arrhythmias - Identifying and Modifying the Arrhythmogenic Substrate

Cardiac electrophysiology has moved a long way forward during recent decades in the comprehension and treatment of complex cardiac arrhythmias. Contemporary electroanatomical mapping systems, along with state-of-the-art technology in the manufacture of electrophysiology catheters and cardiac imaging modalities, have significantly enriched our armamentarium, enabling the implementation of various mapping strategies and techniques in electrophysiology procedures. Beyond conventional mapping strategies, ablation of complex fractionated electrograms and rotor ablation in atrial fibrillation ablation procedures, the identification and modification of the underlying arrhythmogenic substrate has emerged as a strategy that leads to improved outcomes. Arrhythmogenic substrate modification also has a major role in ventricular tachycardia ablation procedures. Optimisation of contact between tissue and catheter and image integration are a further step forward to augment our precision and effectiveness. Hybridisation of existing technologies with a reasonable cost should be our goal over the next few years.