Short-term results of substrate mapping and radiofrequency ablation of ischemic ventricular tachycardia using a saline-irrigated catheter

Programmed Ventricular Stimulation: Risk Stratification and Guiding Antiarrhythmic Therapies

Electrophysiologic testing with programmed ventricular stimulation (PVS) has been utilized to induce ventricular tachycardia (VT), thereby improving risk stratification for patients with ischemic and nonischemic cardiomyopathies and determining the effectiveness of antiarrhythmic therapies, especially catheter ablation. A variety of procedural aspects can be modified during PVS in order to alter the sensitivity and specificity of the test including the addition of multiple baseline pacing cycle lengths, extrastimuli, and pacing locations. The definition of a positive result is also critically important, which has varied from exclusively sustained monomorphic VT (>30 seconds) to any ventricular arrhythmia regardless of morphology. In this review, we discuss the history of PVS and evaluate its role in sudden cardiac death risk stratification in a variety of patient populations. We propose an approach to future investigations that will capitalize on the unique ability to vary the sensitivity and specificity of this test. We then discuss the application of PVS during and following catheter ablation. The strategies that have been utilized to improve the efficacy of intraprocedural PVS are highlighted during a discussion of the limitations of this probabilistic strategy. The role of noninvasive programmed stimulation is also reviewed in predicting recurrent VT and informing management decisions including repeat ablations, modifications in antiarrhythmic drugs, and implantable cardioverter-defibrillator programming. Based on the available evidence and guidelines, we propose an approach to future investigations that will allow clinicians to optimize the use of PVS for risk stratification and assessment of therapeutic efficacy.

Lateral Boundaries of the Ventricular Tachycardia Circuit Align With Sinus Rhythm Discontinuities

BACKGROUND

Sinus rhythm electrical activation mapping can provide information regarding the ischemic re-entrant ventricular tachycardia (VT) circuit. The information gleaned may include the localization of sinus rhythm electrical discontinuities, which can be defined as arcs of disrupted electrical conduction with large activation time differences across the arc.

OBJECTIVES

This study sought to detect and localize sinus rhythm electrical discontinuities that might be present in activation maps constructed from infarct border zone electrograms.

METHODS

Monomorphic re-entrant VT with a double-loop circuit and central isthmus was repeatedly inducible by programmed electrical stimulation in the epicardial border zone of 23 postinfarction canine hearts. Sinus rhythm and VT activation maps were constructed from 196 to 312 bipolar electrograms acquired surgically at the epicardial surface and analyzed computationally. A complete re-entrant circuit was mappable from the epicardial electrograms of VT, and isthmus lateral boundary (ILB) locations were ascertained. The difference in sinus rhythm activation time across ILB locations, vs the central isthmus and vs the circuit periphery, was determined.

RESULTS

Sinus rhythm activation time differences averaged 14.4 milliseconds across the ILB vs 6.5 milliseconds at the central isthmus and 6.4 milliseconds at the periphery (ie, the outer circuit loop) (P ≤ 0.001). Locations with large sinus rhythm activation difference tended to overlap ILB (60.3% ± 23.2%) compared with their overlap with the entire grid (27.5% ± 18.5%) (P < 0.001).

CONCLUSIONS

Disrupted electrical conduction is evident as discontinuity in sinus rhythm activation maps, particularly at ILB locations. These areas may represent permanent fixtures relating to spatial differences in border zone electrical properties, caused in part by alterations in underlying infarct depth. The tissue properties producing sinus rhythm discontinuity at ILB may contribute to functional conduction block formation at VT onset.

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

INTRODUCTION

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

METHODS AND RESULTS

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

CONCLUSION

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

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Structure and function of the ventricular tachycardia isthmus

Catheter ablation of postinfarction reentrant ventricular tachycardia (VT) has received renewed interest owing to the increased availability of high-resolution electroanatomic mapping systems that can describe the VT circuits in greater detail, and the emergence and need to target noninvasive external beam radioablation. These recent advancements provide optimism for improving the clinical outcome of VT ablation in patients with postinfarction and potentially other scar-related VTs. The combination of analyses gleaned from studies in swine and canine models of postinfarction reentrant VT, and in human studies, suggests the existence of common electroanatomic properties for reentrant VT circuits. Characterizing these properties may be useful for increasing the specificity of substrate mapping techniques and for noninvasive identification to guide ablation. Herein, we describe properties of reentrant VT circuits that may assist in elucidating the mechanisms of onset and maintenance, as well as a means to localize and delineate optimal catheter ablation targets.

Catheter ablation of ventricular tachycardia in ischemic cardiomyopathy: Impact of concomitant amiodarone therapy on short- and long-term clinical outcomes

BACKGROUND

Substrate catheter ablation of scar-related ventricular tachycardia (VT) is a widely accepted therapeutic option for patients with ischemic cardiomyopathy (ICM).

OBJECTIVE

The purpose of this study was to investigate whether concomitant amiodarone therapy affects procedural outcomes.

METHODS

A total of 134 consecutive patients (89% male; age 66 ± 10 years) with ICM undergoing catheter ablation of VT were included in the study. Patients were sorted by amiodarone therapy before ablation. In all patients, a substrate-based catheter ablation (endocardial ± epicardial) in sinus rhythm abolishing all "abnormal" electrograms within the scar was performed. The endpoint of the procedure was VT noninducibility. After the ablation procedure, all antiarrhythmic medications were discontinued. All patients had an implantable cardioverter-defibrillator, and recurrences were analyzed through the device.

RESULTS

In 84 patients (63%), the ablation was performed on amiodarone; the remaining 50 patients (37%) were off amiodarone. Patients had comparable baseline characteristics. Mean scar size area was 143.6 ± 44.9 cm² on amiodarone vs 139.2 ± 36.8 cm² off amiodarone (P = .56). More radiofrequency time was necessary to achieve noninducibility in the off-amiodarone group compared to the on-amiodarone group (68.1 ± 20.1 minutes vs 51.5 ± 19.7 minutes; P <.001). In addition, due to persistent VT inducibility, more patients in the off-amiodarone group required epicardial ablation than in the on-amiodarone group (13/50 [26%] vs 5/84 [6%], respectively; P <.001). During mean follow-up of 23.9 ± 11.6 months, recurrence of any ventricular arrhythmias off antiarrhythmic drugs was 44% (37/84) in the on-amiodarone group vs 22% (11/50) in the off-amiodarone group (P = .013).

CONCLUSION

Albeit, VT noninducibility after substrate catheter ablation for scar related VT was achieved faster, with less radiofrequency time and less need for epicardial ablation in patients taking amiodarone, these patients had significantly higher VT recurrence at long-term follow-up when this medication was discontinued.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Characterization of Lesions Created by a Heated, Saline Irrigated Needle-Tip Catheter in the Normal and Infarcted Canine Heart

BACKGROUND

Inability to eliminate intramural arrhythmogenic substrate may lead to recurrent ventricular tachycardia after catheter ablation. The aim of the present study was to evaluate intramural and full thickness lesion formation using a heated saline-enhanced radiofrequency (SERF) needle-tip catheter, compared with a conventional ablation catheter in normal and infarcted myocardium.

METHODS

Twenty-two adult mongrel dogs (30-40 kg, 15 normal and 7 myocardial infarct group) were studied. Lesions were created using the SERF catheter (40 W/50 °C) or a standard contact force (CF) catheter in both groups.

RESULTS

Comparing SERF to CF ablation, the SERF catheter produced larger lesion volumes than the standard CF catheter-even with >20 g of CF-in both normal (983.1±905.8 versus 461.9±178.3 mm³; P=0.023) and infarcted left ventricular myocardium (1052.3±543.0 versus 340.3±160.5 mm³; P=0.001). SERF catheter lesions were more often transmural than standard CF lesions with >20 g of CF in both groups (59.1% versus 7.7%; P<0.001 and 60.0% versus 12.5%; P=0.017, respectively). Using the SERF catheter, mean depth of ablated lesions reached 90% of the left ventricular wall in both normal and infarcted myocardium.

CONCLUSIONS

The SERF catheter created more transmural and larger ablative lesions in both normal and infarcted canine myocardium. SERF ablation is a promising new approach for endocardial intramural and full thickness ablation of ventricular tachycardia substrate that is not accessible with current techniques.

Prolonged action potential duration and dynamic transmural action potential duration heterogeneity underlie vulnerability to ventricular tachycardia in patients undergoing ventricular tachycardia ablation

Aims

Differences of action potential duration (APD) in regions of myocardial scar and their borderzones are poorly defined in the intact human heart. Heterogeneities in APD may play an important role in the generation of ventricular tachycardia (VT) by creating regions of functional block. We aimed to investigate the transmural and planar differences of APD in patients admitted for VT ablation.

Methods and results

Six patients (median age 53 years, five male); (median ejection fraction 35%), were studied. Endocardial (Endo) and epicardial (Epi) 3D electroanatomic mapping was performed. A bipolar voltage of <0.5 mV was defined as dense scar, 0.5–1.5 mV as scar borderzone, and >1.5 mV as normal. Decapolar catheters were positioned transmurally across the scar borderzone to assess differences of APD and repolarization time (RT) during restitution pacing from Endo and Epi. Epi APD was 173 ms in normal tissue vs. 187 ms at scar borderzone and 210 ms in dense scar (P < 0.001). Endocardial APD was 210 ms in normal tissue vs. 222 ms in the scar borderzone and 238 ms in dense scar (P < 0.01). This resulted in significant transmural RT dispersion (ΔRT 22 ms across dense transmural scar vs. 5 ms in normal transmural tissue, P < 0.001), dependent on the scar characteristics in the Endo and Epi, and the pacing site.

Conclusion

Areas of myocardial scar have prolonged APD compared with normal tissue. Heterogeneity of regional transmural and planar APD result in localized dispersion of repolarization, which may play an important role in initiating VT.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Surgical Endoepicardial Linear Ablation for Ventricular Tachycardia With Postinfarction Left Ventricular Aneurysm

This retrospective study evaluated the feasibility of surgical endoepicardial linear ablation for ventricular tachycardia in patients with postinfarction left ventricular aneurysm. Sixty-four patients with multivessel coronary artery disease and left ventricular aneurysm but no mural thrombosis of the aneurysm or valve disease were treated at our institution from March 2012 through July 2015. All underwent off-pump coronary artery bypass grafting and left ventricular aneurysm repair by linear plication. Twenty-three patients (35.9%) had ventricular tachycardia and underwent surgical endoepicardial linear ablation on the beating heart guided by epicardial substrate mapping with the Carto 3 system. The remaining 41 patients (64.1%) composed the no-ablation group. The effectiveness of surgical linear ablation in the ablation group was evaluated. Safety and clinical outcomes were evaluated and compared between the groups. The ventricular tachycardia recurrence rate in the ablation group was 17.4% in the immediate postoperative period and 23.8% at last follow-up (39 ± 21 mo). Early (<30-d) mortality rates were 8.7% in the ablation group and 4.9% in the no-ablation group (P=0.41); the respective late mortality rates were 19.1% and 18% (P=0.70). Multivariate Cox regression analysis indicated that preoperatively poor left ventricular function was an independent risk factor for early and late death in both groups. The groups were similar in terms of the need for postoperative mechanical circulatory support, intensive care unit stay, and cumulative survival rate. We conclude that, for carefully selected candidates, surgical endoepicardial linear ablation combined with off-pump coronary artery bypass grafting and left ventricular aneurysm linear plication is a feasible treatment for ventricular tachycardia with postinfarction left ventricular aneurysm.

Cardiac sympathetic denervation in patients with nonischemic cardiomyopathy and refractory ventricular arrhythmias: a single-center experience

INTRODUCTION

Cardiac sympathetic denervation (CSD) is an effective therapy for selected patients with drug refractory ventricular arrhythmias (VA). Data about the role of CSD in patients with structural heart disease and VAs are sparse. We herein present our experience of CSD in patients with nonischemic cardiomyopathy and VAs despite prior ablation procedure and/or antiarrhythmic drug (AAD) therapy.

METHODS

A total of ten patients (mean age 61.6 ± 19.6, mean LVEF 29.5 ± 12.1%) with nonischemic dilated cardiomyopathy (NICM) (n = 9) and hypertrophic cardiomyopathy (HCM) (n = 1) underwent CSD (left sided in six and bilateral in four patients) due to refractory VA despite multiple AADs (mean number of AADs was 1.6 ± 0.7) and prior VT ablation (mean number of procedures per patient was 1.5 ± 1.3).

RESULTS

Mean follow-up was 10.1 ± 6.9 months. The median number of VA and ICD shocks decreased significantly from 9.0 and 2.5 episodes 6 months prior to CSD to 0 and 0 episodes within 6 months after CSD (p = 0.012 and p = 0.011). Five patients remained free from sustained VA recurrences. Two patients experienced single ICD shock due to a polymorphic VT (triggered by severe hypokalemia in one patient) and one patient a single shock due to monomorphic VT. One patient had five episodes of slow VT under amiodarone therapy (three of them terminated by antitachycardia pacing) and underwent endo- epicardial re-ablation. Two patients died 1 month after CSD. One of them due to electrical storm and cardiogenic shock and the second one due to refractory cardiogenic shock, without recurrence of VAs though. No major complications of CSD occurred. No patient suffered from Horner syndrome.

CONCLUSION

In this study, CSD was effective for treatment of VAs in patients with structural heart disease refractory to antiarrhythmic drugs and catheter ablation. Further larger studies are required to confirm these findings.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Rationale and design of BERLIN VT study: a multicenter randomised trial comparing preventive versus deferred ablation of ventricular tachycardia

INTRODUCTION

Catheter ablation (CA) has shown to effectively reduce the burden of ventricular tachycardia in patients with implanted cardioverter-defibrillator (ICD). However, in patients with ICD implantation for secondary prevention of ventricular tachycardia (VT), the appropriate time point of CA and its effect on mortality and heart failure progression remains a matter of debate.

METHODS AND ANALYSIS

We present the design of the ongoing preventive aB lation of vE ntriculartachyca R dia in patients with myocardia LIN farction (BERLIN VT) study that aims to prospectively enrol 208 patients with a stable ischaemic cardiomyopathy, a left ventricular ejection fraction of 30% to 50% and documented ventricular tachycardia. Patients will be 1:1 randomised to undergo CA at the time of ICD implantation or CA after the third appropriate ICD shock for ventricular tachycardia. ICD implantation will be performed in all patients. The primary endpoint is defined as the time to first event comprising all-cause mortality and unplanned hospital admission for congestive heart failure or for symptomatic VT/ventricular fibrillation. The patients will be followed until study termination according to the event driven design. Completion of enrolment is expected for mid of 2019.

ETHICS AND DISSEMINATION

The study had been approved by the "Ethik-kommission der Landesärztekammer Hamburg" as well as the local institutional review boards for each of the participation sites. The results of the trial will be published in peer-reviewed journals TRIAL REGISTRATION NUMBER: NCT02501005.

Characteristics of ventricular tachycardia and long-term treatment outcome in patients with dilated cardiomyopathy complicated by lamin A/C gene mutations

BACKGROUND

Dilated cardiomyopathy caused by lamin A/C gene (LMNA) mutation is complicated with atrioventricular (AV) conduction disturbances, malignant ventricular arrhythmias, and progressive severe heart failure. Radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) has been reported to be challenging due to the high recurrence rate in patients with LMNA-related cardiomyopathy. However, electrophysiological and histopathological characteristics of VT substrate remain to be fully elucidated.

METHODS AND RESULTS

We experienced 6 familial patients with LMNA-related cardiomyopathy in 3 pedigrees (6 males, 43.7±4.5 [SD] years). All patients had first VT attack at 50±6.6 [SD] years of age, and 4 underwent RFCA for incessant VT. Their electrocardiograms during VT showed similar QRS morphologies, characterized by an inferior axis, SR pattern in aVR, and QS pattern in aVL, suggesting the origin of the basal anterior ventricle. Indeed, the VTs had multiple exits around the basal anterior ventricular septum in all RFCA cases. Although we performed multiple RFCA procedures including epicardial ablation and surgical cryoablation, all cases experienced VT recurrences in 4.5±6.4 [SD] months after last procedure. All patients developed end-stage heart failure with frequent VT events, and died at 59.5±3.6 years of age (severe heart failure in 5 and lung disease in 1). In three autopsy cases with RFCA, fibrofatty degeneration was noted in the AV node. In addition, in the deep basal ventricular septum, inhomogenous fibrotic degenerated tissue was noted beyond the reach of RF lesions.

CONCLUSIONS

These results demonstrate that patients with LMNA-related cardiomyopathy are characterized by VTs refractory to RFCA probably because of the deep intramural focus at the basal ventricular septum, resulting in poor prognosis with progressive severe heart failure despite all available optimized therapies. Thus, we should consider heart transplantation in their early 50s when several VT events begin to occur.

Open chest epicardial and transapical endocardial substrate ablation for ventricular tachycardia with left ventricular aneurysm in a porcine model

BACKGROUND

Endo-epicardial radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) as a first-line strategy has been shown to improve outcomes. This study sought to evaluate the feasibility and validity of open-chest epicardial and transapical endocardial substrate ablation for VT with left ventricular aneurysm (LVA) applying to routine cardiac surgery.

METHODS

Porcine models of LVA with VT were developed and were divided into a study group (RFCA from the epicardium via direct-view and endocardium via transapical access) and a control group (endocardial RFCA via retrograde transaortic access). Substrate-based mapping and ablation targeting abnormal potentials were performed under thoracotomy. Outcomes, including procedural success and acute freedom from VT, were analysed.

RESULTS

Twenty-four of 35 (68.57%) acute myocardial infarction (AMI) pigs developed LVA with VT in a 6-week survival period and were randomly divided into a study group (n=12) and a control group (n=12). All animals in the study group successfully underwent endocardial mapping and ablation by transapical access. The scar size of the endocardium and the left ventricular chamber volume were similar in the two groups. Acute freedom from VT in the study group was remarkably superior to that in the control group (88.33% vs. 58.33%, p=0.04).

CONCLUSIONS

Combined, direct epicardial and transapical endocardial substrate mapping and ablation appeared to be feasible and effective for treating VT with LVA under thoracotomy.

Prognostic Value of Noninducibility on Outcomes of Ventricular Tachycardia Ablation: A VANISH Substudy

OBJECTIVES

This study sought to evaluate the predictive value of noninducibility on long-term outcomes.

BACKGROUND

The traditional endpoint for catheter ablation of ventricular tachycardia (VT) is noninducibility of VT by programmed stimulation; however, the definition of inducibility remains variable and its prognostic value limited by nonstandardized periprocedural antiarrhythmic drug therapy and implantable cardioverter-defibrillator programming in prior observational studies. The VANISH trial randomized patients with prior myocardial infarction and VT to ablation (with an endpoint of noninducibility of VT ≥300 ms after ablation) versus antiarrhythmic drug escalation.

METHODS

Patients enrolled in the VANISH study randomized to catheter ablation were included. The relationship between post-ablation inducibility and the primary composite endpoint (death, VT storm >30 days, or appropriate implantable cardioverter-defibrillator shock >30 days) was assessed using a time-to-event analysis, adjusting for other clinical and procedural characteristics.

RESULTS

A total of 129 patients from the ablation arm were included in the primary analysis, of which 51 were noninducible post-ablation compared with 78 who had inducible VT or in whom inducibility testing was not performed. There were no significant baseline characteristic or procedural differences except for increased implantable cardioverter-defibrillator shocks before randomization in the noninducible group. In multivariate analysis, inducibility significantly increased the risk of death, appropriate shock, or VT storm after 30 days (HR: 1.87; p = 0.017).

CONCLUSIONS

Inducibility of any VT post-ablation was associated with an increased risk of the composite endpoint in the VANISH trial. A randomized trial is required to confirm whether more aggressive ablation targeting faster induced VTs (<300 ms) can improve outcomes.

Surgical linear ablation for ventricular tachycardia with postinfarction ventricular aneurysm

BACKGROUND

Left ventricular aneurysm (LVA) might be an arrhythmogenic substrate. Endocardiectomy and cryoablation for ventricular tachycardia (VT) with LVA can cause extensive myocardial damage. We aimed to evaluate the feasibility of surgical radial linear ablation for VT with LVA guided by electrophysiological mapping.

MATERIALS AND METHODS

Porcine models of VT with LVA were developed. Endocardial and epicardial substrate mapping during sinus rhythm were performed under thoracotomy. Surgical radial linear ablation was achieved by a bipolar radiofrequency ablation device. Outcomes, including procedural success and acute freedom of VT, were analyzed.

RESULTS

Fifteen of 20 pigs developed LVA in a 6-wk survival period. A total of 28 sustained monomorphic VTs were initiated in 13 of 15 pigs (86.67%). The number of potential points captured from the endocardium and epicardium were 319 ± 45 and 358 ± 52 per animal, respectively. The ablative targets containing abnormal potentials were located largely on the border zone of LVA. Eight linear lesions from core to border zone of LVA were achieved per animal in a radial and even manner continuously, and ablation was repeated three times to transect border zone. The acute freedom of VT was 84.62%, P < 0.05.

CONCLUSIONS

Surgical linear endo-epicardial ablation seemed to be feasible in a porcine model with VT and LVA.

Point-by-point versus multisite electrode mapping in VT ablation: does freedom from VT recurrences depend on mapping catheter? An observational study

PURPOSE

This study was conducted with the purpose of determining whether or not the potential technical advantages of multi-electrode mapping catheters in catheter ablation (CA) of ventricular tachycardia (VT) result in any relevant clinical benefit for VT patients.

METHODS

A single-center VT study, having taken place from 2012 to 2014 using a standard 3.5-mm catheter (Thermocool SF® group 1) and from 2014 to 2016 using a 1-mm multi-electrode-mapping catheter (PentaRay® group 2), was conducted. The endpoint was the complete elimination of late potentials (LPs), local abnormal ventricular activities (LAVA), and VT non-inducibility. Follow-up consisted of device interrogation to monitor for VT recurrence.

RESULTS

Out of 74 VT patients aged 64.5 ± 12.0 years (66 male [89.2%], 56 with ICM [75.7%], and 18 with NICM [24.3%)]), 48 patients (64.9%) were investigated in group 1 and 26 (35.1%) in group 2. Using the multi-point acquisition approach, a tendency to require less mapping time (group 1 65.2 ± 37.6 min, group 2 55.6 ± 34.4 min, p ns) was determined. During 12-month follow-up, 57 patients had freedom from VT recurrences (79.2%). The result was insignificant between the groups (38 patients (79.2%) in group 1 and 19 patients (73.1%) in group 2).

CONCLUSIONS

In a single-center observational study, both conventional and high-density mapping approaches in VT patients are comparable in terms of procedure duration and outcome. Mapping time when using a multi-electrode catheter seems to have the tendency of being shorter. We should be encouraged to recruit more patients comparing the benefit of different catheter types.

Influence of Intramyocardial Adipose Tissue on the Accuracy of Endocardial Contact Mapping of the Chronic Myocardial Infarction Substrate

BACKGROUND

Recent studies have demonstrated that intramyocardial adipose tissue (IMAT) may contribute to ventricular electrophysiological remodeling in patients with chronic myocardial infarction. Using an ovine model of myocardial infarction, we aimed to determine the influence of IMAT on scar tissue identification during endocardial contact mapping and optimal voltage-based mapping criteria for defining IMAT dense regions.

METHOD AND RESULTS

In 7 sheep, left ventricular endocardial and transmural mapping was performed 84 weeks (15-111 weeks) post-myocardial infarction. Spearman rank correlation coefficient was used to assess the relationship between endocardial contact electrogram amplitude and histological composition of myocardium. Receiver operator characteristic curves were used to derive optimal electrogram thresholds for IMAT delineation during endocardial mapping and to describe the use of endocardial mapping for delineation of IMAT dense regions within scar. Endocardial electrogram amplitude correlated significantly with IMAT (unipolar r=-0.48±0.12, P<0.001; bipolar r=-0.45±0.22, P=0.04) but not collagen (unipolar r=-0.36±0.24, P=0.13; bipolar r=-0.43±0.31, P=0.16). IMAT dense regions of myocardium reliably identified using endocardial mapping with thresholds of <3.7 and <0.6 mV, respectively, for unipolar, bipolar, and combined modalities (single modality area under the curve=0.80, P<0.001; combined modality area under the curve=0.84, P<0.001). Unipolar mapping using optimal thresholding remained significantly reliable (area under the curve=0.76, P<0.001) during mapping of IMAT, confined to putative scar border zones (bipolar amplitude, 0.5-1.5 mV).

CONCLUSIONS

These novel findings enhance our understanding of the confounding influence of IMAT on endocardial scar mapping. Combined bipolar and unipolar voltage mapping using optimal thresholds may be useful for delineating IMAT dense regions of myocardium, in postinfarct cardiomyopathy.

Catheter Ablation for Ventricular Tachycardia in Patients with Nonischemic Cardiomyopathy

Although catheter ablation has been successful in reducing the recurrence of ventricular tachycardia in patients with ischemic disease, outcomes in patients with nonischemic cardiomyopathy (NICM) have not met with the same results. Success is predicated on a methodical approach to diagnosis of disease type and identification of critical substrate, and the ablation strategies used. Cardiac MRI with delayed enhancement is able to identify areas of substrate involvement, particularly in situations when conventional catheter mapping is not able to do so. Radiofrequency needle, irrigated bipolar radiofrequency, and transcoronary alcohol ablation are effective and alternative techniques to endocardial and epicardial ablation.

Interactive In-Vitro Training In Physics Of Radiofrequency Ablation For Physicians And Medical Engineering Students

Radiofrequency (RF) ablation requires a complex set of devices as well as profound electrophysiological experience and substantial knowledge of physical science basics. To establish RF ablation in-vitro teaching-system, six workstations were equipped with computer-controlled RF ablation generators. Universal connection boxes allow ablation-essays with catheters of different make and model. Special wetlabs were developed combining a basin containing isotonic saline solution with a thermostat and a pump to simulate blood flow. This hands-on teaching system can be used to demonstrate differences in lesion-forming dependent on tip-electrodes, sensor technology and ablation techniques, influence of blood flow and electrode-angle to the myocardium. It was also utilized to reproduce industrial in-vitro tests.

Ultrasound-Guided Transesophageal High-Intensity Focused Ultrasound Cardiac Ablation in a Beating Heart: A Pilot Feasibility Study in Pigs

Catheter ablation for the treatment of arrhythmia is associated with significant complications and often-repeated procedures. Consequently, a less invasive and more efficient technique is required. Because high-intensity focused ultrasound (HIFU) enables the generation of precise thermal ablations in deep-seated tissues without harming the tissues in the propagation path, it has the potential to be used as a new ablation technique. A system capable of delivering HIFU into the heart by a transesophageal route using ultrasound (US) imaging guidance was developed and tested in vivo in six male pigs. HIFU exposures were performed on atria and ventricles. At the time of autopsy, visual inspection identified thermal lesions in the targeted areas in three of the animals. These lesions were confirmed by histologic analysis (mean size: 5.5 mm(2) × 11 mm(2)). No esophageal thermal injury was observed. One animal presented with bradycardia due to an atrio-ventricular block, which provides real-time confirmation of an interaction between HIFU and the electrical circuits of the heart. Thus, US-guided HIFU has the potential to minimally invasively create myocardial lesions without an intra-cardiac device.

Ablation of Ventricular Tachycardia in Patients with Ischemic Cardiomyopathy

Ventricular tachycardias (VTs) occurring after prior myocardial infarction are usually caused by reentrant circuits formed by surviving myocardial bundles. Although part of the reentrant circuits may be located in the midmyocardium or epicardium, most of the VTs can be safely and successfully ablated by endocardial ablation targeting the late potentials/local abnormal ventricular activation, which are surrogates for the surviving myocardial bundles. A combination of activation, substrate, pace, and entrainment mapping, as well as the use of contact force catheters, further improves ablation success and safety.

Irrigated Needle Ablation Creates Larger and More Transmural Ventricular Lesions Compared With Standard Unipolar Ablation in an Ovine Model

Background—

Ventricular tachycardia recurrence can occur after ventricular tachycardia ablation because of incomplete and nontransmural ventricular lesion formation. We sought to compare the lesions made by a novel irrigated needle catheter to conventional radiofrequency lesions.

Methods and Results—

Thirteen female sheep (4.6±0.7 years, 54±8 kg) were studied. In 7 sheep, 60-s radiofrequency applications were performed using an irrigated needle catheter. In 6 sheep, conventional lesions were made using a 4-mm irrigated catheter. 1.5T in vivo and high-density magnetic resonance imaging (9.4T) were performed on explanted hearts from animals receiving needle radiofrequency. Conventional lesion volume was calculated as (1/6)×π×(A×B 2 +C×D 2 /2). Needle lesion volume was measured as Σ(π×r 2 )/2 with a slice thickness of 1 mm. The dimensions of all lesions were also measured on gross pathology. Additional histological analysis of the needle lesions was performed. One hundred twenty endocardial left ventricular ablation lesions (conventional, n=60; needle, n=60) were created. At necropsy, more lesions were found using needle versus conventional radiofrequency (90% versus 75%; P <0.05). Comparing needle versus conventional radiofrequency: lesion volume was larger (1030±362 versus 488±384 mm 3 ; P <0.001), lesion depth was increased (9.9±2.7 versus 5±2.4 mm; P <0.001), and more transmural lesions were created (62.5% versus 17%; P <0.01). Pericardial contrast injection was observed in 4 apical attempts using needle radiofrequency, however, with no adverse effects. Steam pops occurred in 3 attempts using conventional radiofrequency.

Conclusions—

Irrigated needle ablation is associated with more frequent, larger, deeper, and more often transmural lesions compared with conventional irrigated ablation. This technology might be of value to treat intramural or epicardial ventricular tachycardia substrates resistant to conventional ablation.

Approach to ablation of unmappable ventricular arrhythmias

Most patients with structural heart disease referred for ventricular tachycardia ablation have unstable tachycardias not suitable for conventional mapping (ie, entrainment mapping). Substrate-guided mapping and ablation during sinus rhythm are intended to overcome the limitations of conventional mapping and ablation. Substrate ablation permits elimination of multiple ventricular tachycardias irrespective of their inducibility during the procedure or their hemodynamic tolerability. Moreover, the elimination/isolation of the arrhythmogenic substrate identified during sinus rhythm has been associated with better outcomes. There is currently no standardized approach for substrate-guided ablation. This article discusses the main aspects of the proposed techniques and substrate ablation targets.

Scar Dechanneling

Background—

Ventricular tachycardia (VT) substrate ablation usually requires extensive ablation. Scar dechanneling technique may limit the extent of ablation needed.

Methods and Results—

The study included 101 consecutive patients with left ventricular scar–related VT (75 ischemic patients; left ventricular ejection fraction, 36±13%). Procedural end point was the elimination of all identified conducting channels (CCs) by ablation at the CC entrance followed by abolition of residual inducible VTs. By itself, scar dechanneling rendered noninducibility in 54.5% of patients; ablation of residual inducible VT increased noninducibility to 78.2%. Patients needing only scar dechanneling had a shorter procedure (213±64 versus 244±71 minutes; P =0.027), fewer radiofrequency applications (19±11% versus 27±18%; P =0.01), and external cardioversion/defibrillation shocks (20% versus 65.2%; P <0.001). At 2 years, patients needing scar dechanneling alone had better event-free survival (80% versus 62%) and lower mortality (5% versus 11%). Incomplete CC-electrogram elimination was the only independent predictor (hazard ratio, 2.54 [1.06–6.10]) for the primary end point. Higher end point-free survival rates were observed in patients noninducible after scar dechanneling (log-rank P =0.013) and those with complete CC-electrogram elimination (log-rank P =0.013). The complications rate was 6.9%, with no deaths.

Conclusions—

Scar dechanneling alone results in low recurrence and mortality rates in more than half of patients despite the limited ablation extent required. Residual inducible VT ablation improves acute results, but patients who require it have worse outcomes. Recurrences are mainly related to incomplete CC-electrogram elimination.

Successful focal ablation in a patient with electrical storm in the early postinfarction period: case report

Electrical storm (ES) is associated with a poor prognosis if it occurs in the early postinfarction period (within 4 weeks). There are limited data on the efficacy and safety of catheter ablation in the early period. In the patients with postinfarction cardiomyopathy, ventricular tachycardia (VT) is usually caused by re-entry through slowly conducting tissue within areas of a myocardial scar, whereas for the early postinfarction period, the underlying mechanism of ES is not fully understood. We report a case of ES for which macroreentry was excluded as a mechanism of VT because of the clinical and electrophysiological properties of the tachycardia. The tachycardia was terminated by focal radiofrequency catheter ablation of the earliest site. The total procedure time was only 35 minutes. During a 12-month follow-up period, the patient has remained free of monomorphic VT episodes. On the basis of this case, we aimed to discuss the underlying mechanism of ES in the early postinfarction period and to evaluate the role of radiofrequency catheter ablation as a primary approach for treating ES.

Noninducibility in Postinfarction Ventricular Tachycardia as an End Point for Ventricular Tachycardia Ablation and Its Effects on Outcomes

Background—

Although ventricular tachycardia (VT) ablation is a widely used therapy for patients with VT, the ideal end points for this procedure are not well defined. We performed a meta-analysis of the published literature to assess the predictive value of noninducibility of postinfarction VT for long-term outcomes after VT ablation.

Methods and Results—

We performed a systematic review of MEDLINE (1950–2013), EMBASE (1988–2013), the Cochrane Controlled Trials Register (Fourth Quarter, 2012), and reports presented at scientific meetings (1994–2013). Randomized controlled trials, case–control, and cohort studies of VT ablation were included. Outcomes reported in eligible studies were freedom from VT/ventricular fibrillation and all-cause mortality. Of the 3895 studies evaluated, we identified 8 cohort studies enrolling 928 patients for the meta-analysis. Noninducibility after VT ablation was associated with a significant increase in arrhythmia-free survival compared with partial success (odds ratio, 0.49; 95% confidence interval, 0.29–0.84; P =0.009) or failed ablation procedure (odds ratio, 0.10; 95% confidence interval, 0.06–0.18; P <0.001). There was also a significant reduction in all-cause mortality if patients were noninducible after VT ablation compared with patients with partial success (odds ratio, 0.59; 95% confidence interval, 0.36–0.98; P =0.04) or failed ablation (odds ratio, 0.32; 95% confidence interval, 0.10–0.99; P =0.049).

Conclusions—

Noninducibility of VT after VT ablation is associated with improved arrhythmia-free survival and all-cause mortality.

In vivo left-ventricular contact force analysis: comparison of antegrade transseptal with retrograde transaortic mapping strategies and correlation of impedance and electrical amplitude with contact force

AIMS

Clinical outcomes following radiofrequency ablation of ventricular tachycardias (VTs) depend on catheter tip-to-tissue contact force (CF). Left-ventricular (LV) mapping is performed via antegrade-transseptal or retrograde-transaortic approaches, and the applied CF may depend on the approach used. This study evaluated (i) the impact of antegrade-transseptal vs. retrograde-transaortic LV-mapping approaches on CF and catheter stability and (ii) the clinical value of the commonly used surrogate markers of catheter-myocardial contact-impedance, unipolar, and bipolar electrogram amplitudes.

METHODS AND RESULTS

An antegrade-transseptal and a retrograde-transaortic LV-mapping approach was performed in 10 patients undergoing VT ablation by using CF-sensing catheters. Operators were blinded to CF data and data were analysed according to 11 predefined LV segments. Three thousand three hundred and twenty-four mapping points (1577 antegrade, 1747 retrograde) were analysed, including 80 (2.4%) points with maximum CF > 100 g. Median antegrade and retrograde CF were 16.0 g (q1-q3; 8.4-26.2) and 15.3 g (9.8-23.4), respectively. Contact force was significantly higher antegradely in mid-anteroseptum, mid-lateral, and apical segments, and significantly higher retrogradely in basal-anteroseptum, basal-inferoseptum, basal-inferior, and basal-lateral segments. Contact force did correlate with impedance, unipolar, and bipolar electrogram amplitudes; however, there were large overlaps.

CONCLUSIONS

Antegrade vs. retrograde LV-mapping approaches result in different CF. A combined approach to the LV mapping may improve the overall LV mapping, potentially resulting in better clinical outcomes for the left VT catheter ablation. The previous surrogate markers used to assess CF do correlate with in vivo CF; however, due to a larger overlap, their clinical value is limited.

Catheter ablation for ventricular tachycardia: indications and techniques

Ventricular tachycardia (VT) may be secondary to many different underlying pathophysiologies. The nature of the underlying disorder determines amenability to catheter ablation, thus, dictating the circumstances under which it should be undertaken. The differing substrates also influence the choice of techniques that are used. The most intensively studied clinical subgroup of VT is re-entrant VT in the setting of ischemic heart disease. The approach to ablation in such patients is discussed in detail. Subsequent discussion focuses on other clinically encountered varieties of VT and the ablation methods used in each individual disease state.

[Use of cardiac MRI in the field of electrophysiology. Present status and future aspects]

In recent years, ablation therapy has become the first-line treatment of modern electrophysiology in patients with cardiac arrhythmias. Today, cardiac magnetic resonance imaging (cMRI) is an important supportive imaging technique in the implementation of complex electrophysiological investigations and ablation therapy. In clinical routine, cMRI is used not only to generate accurate three-dimensional (3D) models of cavities of the heart but also for visualization of complex anatomical structures. The development of cMRI makes it possible to detect the underlying substrate of complex arrhythmias such as myocardial scar in patients with ventricular tachycardia or the structural remodeling of the left atrium in patients with atrial fibrillation. The opportunity of fusion of the different imaging modalities (e.g., fluoroscopy, cMRI) has become essential for the planning and the implementation of a safe ablation therapy. The possibility of direct visualization of induced lesions using cMRI after and in the long term after ablation can predict the success of therapy and detects potential complications. The continuous research in the field of cMRI and the development of MRI-compatible pacing and ablation catheters provided the basics for performing electrophysiological treatment in humans directly inside the MRI. The implementation of ablation using exact visualization of the anatomical substrate, precise catheter navigation and real-time visualization of lesions in cMRI promises to improve success rates and the safety of complex ablation treatment and may revolutionize electrophysiology in the future.

VT ablation in heart failure

Ventricular tachycardias (VT), shocks, and clusters of shock are ominous signs in patients with implantable cardioverter-defibrillators and herald an increased risk of hospitalization and mortality. VT clusters have been associated with aggravation of heart failure (19%), acute coronary events (14%), and electrolyte imbalance (10%). Yet, any association of potential causative factors and aggravation of VT is vague. Maybe, in patients with any substrate for re-entry, progressive aggravation of ventricular dysrhythmias is to be expected. The high recurrence rate of electrical storm despite antiarrhythmic drug therapy supports this view. The optimal timing of VT ablation is unknown, but current convention is to perform VT ablation after shock clusters or incessant VT has occurred. Preemptive VT ablation before VT has occurred is rarely performed (only in 15% of active centers) and the majority of centers never perform VT ablation even after the first shock. Such practice is within guidelines that recommend VT ablation only in ICD patients with recurrent or incessant VT. However, there is strong data in support of preemptive VT ablation.

Role of catheter ablation of ventricular tachycardia associated with structural heart disease

In patients with structural heart disease, ventricular tachycardia (VT) worsens the clinical condition and may severely affect the short- and long-term prognosis. Several therapeutic options can be considered for the management of this arrhythmia. Among others, catheter ablation, a closed-chest therapy, can prevent arrhythmia recurrences by abolishing the arrhythmogenic substrate. Over the last two decades, different techniques have been developed for an effective approach to both tolerated and untolerated VTs. The clinical outcome of patients undergoing ablation has been evaluated in multiple studies. This editorial gives an overview of the role, methodology, clinical outcome and innovative approaches in catheter ablation of VT.

Spatiotemporal electrophysiological changes in a murine ablation model

AIMS

High recurrence rates after complex radiofrequency ablation procedures, such as for atrial fibrillation, remain a major clinical problem. Local electrophysiological changes that occur following cardiac ablation therapy are incompletely described in the literature. The purpose of this study was to determine whether alterations in conduction velocity, action potential duration (APD), and effective refractory period resolve dynamically following cardiac ablation.

METHODS AND RESULTS

Lesions were delivered to the right ventricle of mice using a subxiphoid approach. The sham-operated control group (SHAM) received the same procedure without energy delivery. Hearts were isolated at 0, 1, 7, 30, and 60 days following the procedure and electrophysiological parameters were obtained using high-resolution optical mapping with a voltage-sensitive dye. Conduction velocity was significantly decreased at the lesion border in the 0, 7, and 30 day groups compared to SHAM. APD(70) at the lesion border was significantly increased at all time points compared to SHAM. Effective refractory period was significantly increased at the lesion border at 0, 1, 7, and 30 days but not at 60 days post-ablation. This study demonstrated that post-ablation electrophysiological changes take place immediately following energy delivery and resolve within 60 days.

CONCLUSIONS

Cardiac ablation causes significant electrophysiological changes both within the lesion and beyond the border zone. Late recovery of electrical conduction in individual lesions is consistent with clinical data demonstrating that arrhythmia recurrence is associated with failure to maintain bi-directional conduction block.

Unmappable ventricular tachycardia after an old myocardial infarction. Long-term results of substrate modification in patients with an implantable cardioverter defibrillator

Purpose

The frequent occurrence of ventricular tachycardia can create a serious problem in patients with an implantable cardioverter defibrillator. We assessed the long-term efficacy of catheter-based substrate modification using the voltage mapping technique of infarct-related ventricular tachycardia and recurrent device therapy.

Methods

The study population consisted of 27 consecutive patients (age 68 ± 8 years, 25 men, mean left ventricular ejection fraction 31 ± 9%) with an old myocardial infarction and multiple and/or hemodynamically not tolerated ventricular tachycardia necessitating repeated device therapy. A total of 31 substrate modification procedures were performed using the three-dimensional electroanatomical mapping system. Patients were followed up for a median of 23.5 (interquartile range 6.5–53.2) months before and 37.8 (interquartile range 11.7–71.8) months after ablation. Antiarrhythmic drugs were not changed after the procedure, and were stopped 6 to 9 months after the procedure in patients who did not show ventricular tachycardia recurrence.

Results

Median ventricular tachycardias were 1.6 (interquartile range 0.7–6.7) per month before and 0.2 (interquartile range 0.00–1.3) per month after ablation (P = 0.006). Nine ventricular fibrillation episodes were registered in seven patients before and two after ablation (P = 0.025). Median antitachycardia pacing decreased from 1.6 (interquartile range 0.01–5.5) per month before to 0.18 (interquartile range 0.00–1.6) per month after ablation (P = 0.069). Median number of shocks decreased from 0.19 (interquartile range 0.04–0.81) per month before to 0.00 (interquartile range 0.00–0.09) per month after ablation (P = 0.001). One patient had a transient ischemic attack during the procedure, and another developed pericarditis. Nine patients died during follow-up, eight patients due to heart failure and one patient during valve surgery.

Conclusion

Catheter-based substrate modification using voltage mapping results in a long-lasting reduction of cardioverter defibrillator therapy in patients with multiple and/or hemodynamically not tolerated infarct-related ventricular tachyarrhythmia.