Entrainment/mapping criteria for the prediction of termination of ventricular tachycardia by single radiofrequency lesion in patients with coronary artery disease

Ventricular Tachycardia Ablation Endpoints: Moving Beyond Noninducibility

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

Impedance-decline-guide power control long application time bipolar radiofrequency catheter ablation

INTRODUCTION

Bipolar (BIP) radiofrequency (RF) ablation creates deep myocardial lesions but ideal energy application modes to treat ventricular arrhythmias originating from deep inside the thick myocardium have not been well established. An experimental study was performed to clarify whether high power and long application time BIP ablation were performable by impedance-decline-guide power control (PC) and whether it could create transmural lesions in the thick ventricle with a minimum risk of steam-pop.

METHODS AND RESULTS

Perfused porcine ventricle (18.4 ± 2.3 mm) was placed in an experimental bath and BIP ablation (50 W) for 120 s was attempted with catheter contact of 30-g using two protocols; fixed power (FP) and impedance-decline-guide PC. In the latter protocol, BIP ablation was started from 50 W, while the energy was decreased to 40-20 W according to the impedance decline during RF ablation. FP ablation was attempted in 30 applications and the transmural lesion was created in all 30, although steam-pop occurred in 16/30 applications (53%). Low minimum impedance, large total impedance decline (TID), and %-TID were associated with the steam-pop occurrence. PC ablation was attempted in another 21 applications, and the transmural lesion was created in all 21 without steam-pop. PC ablation was superior to FP ablation (21/21 vs. 14/30, p < .001) in the creation of a transmural lesion without resulting in steam-pop.

CONCLUSIONS

High power and long application time BIP ablation seems to be feasible according to the impedance-decline-guide approach, which could create transmural lesions in thick porcine ventricles with minimal risk of steam-pop.

Contemporary Management of Complex Ventricular Arrhythmias

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

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.

Activation During Sinus Rhythm in Ventricles With Healed Infarction: Differentiation Between Arrhythmogenic and Nonarrhythmogenic Scar

BACKGROUND

In infarct-related ventricular tachycardia (VT), the circuit often corresponds to a location characterized by activation slowing during sinus rhythm (SR). However, the relationship between activation slowing during SR and vulnerability for reentry and correlation to components of the VT circuit are unknown. This study examined the relationship between activation slowing during SR and vulnerability for reentry and correlated these areas with components of the circuit.

METHODS

In a porcine model of healed infarction, the spatial distribution of endocardial activation velocity was compared between SR and VT. Isthmus sites were defined using activation and entrainment mapping as areas exhibiting diastolic activity within the circuit while bystanders were defined as areas displaying diastolic activity outside the circuit.

RESULTS

Of 15 swine, 9 had inducible VT (5.2±3.0 per animal) while in 6 swine VT could not be induced despite stimulation from 4 RV and LV sites at 2 drive trains with 6 extra-stimuli down to refractoriness. Infarcts with VT had a greater magnitude of activation slowing during SR. A minimal endocardial activation velocity cutoff ≤0.1 m/s differentiated inducible from noninducible infarctions (P=0.015). Regions of maximal endocardial slowing during SR corresponded to the VT isthmus (area under curve=0.84 95% CI, 0.78-0.90) while bystander sites exhibited near-normal activation during SR. VT circuits were complex with 41.7% exhibiting discontinuous propagation with intramural bridges of slow conduction and delayed quasi-simultaneous endocardial activation. Regions forming the VT isthmus borders had faster activation during SR while regions forming the inner isthmus were activated faster during VT.

CONCLUSIONS

Endocardial activation slowing during SR may differentiate infarctions vulnerable for VT from those less vulnerable for VT. Sites of slow activation during SR correspond to sites forming the VT isthmus but not to bystander sites.

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.

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.

Treatment of Ventricular Arrhythmias and Use of Implantable Cardioverter-Defibrillators to Improve Survival in Older Adult Patients with Cardiac Disease

Ventricular arrhythmia (VA) and sudden cardiac death (SCD) are well-recognized problems in the overall heart failure population, but treatment decisions can be more complex and nuanced in older patients. Sustained VA does not always lead to SCD, but identifies a higher risk population and may cause significant symptoms. Antiarrhythmic drugs (AAD) and catheter ablation are the mainstays for prevention of VA, but have not been shown to improve mortality. The value of implantable cardiac defibrillators (ICDs) may be influenced by patient age. This article discusses long-term treatment of VA and the use of ICDs in the elderly.

[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.

Mark E Josephson: Clinical Investigator

Mark E Josephson entered the world of clinical cardiac electrophysiology (EP) almost at its inception (1972); with so much to learn and so many directions one could take, he dived into the field with unbridled enthusiasm and an uncommon - perhaps almost unique - aptitude for asking questions and finding ways to answer them. Few aspects of EP escaped his indelible influence. In this short paper, I will attempt to touch on some of the high points of his astounding career as a clinical investigator.

Long Postpacing Interval After Entrainment of Tachycardia Including a Slow Conduction Zone Within the Circuit

BACKGROUNDS

Postpacing interval (PPI) measured after entrainment pacing describes the distance between pacing site and reentrant circuit. However, the influential features to PPI remain to be elucidated.

METHODS AND RESULTS

This study included 22 cases with slow/fast atrioventricular (AV) nodal reentrant tachycardia (AVNRT), 14 orthodromic AV reciprocating tachycardia (AVRT) using an accessary pathway, 22 typical atrial flutter (AFL), and 18 other macroreentrant atrial tachycardia (atypical AFL). Rapid pacing at a pacing cycle length (PCL) 5% shorter than tachycardia cycle length (TCL) was done from a site on or close to the reentry circuit. Pacing sites included the coronary sinus ostium in AVNRT, earliest atrial activation site in AVRT, and cavotricuspid isthmus in typical AFL. In atypical AFL, tachycardia circuit was determined on the basis of CARTO mapping, and then the pacing site was. TCL was significantly longer in AVNRT and AVRT than in typical AFL and atypical AFL (both P < 0.05). PCL minus TCL value was similar among the 4 groups. PPI minus TCL value (milliseconds) was significantly longer in AVNRT (median, 40 [IQR, 29-60.8]) and AVRT (34 [20-47]) than in typical AFL (0 [0-4]) and atypical AFL (3.5 [0-8]) (both P < 0.05). Furthermore, PPI minus TCL was prolonged with shortening of PCL in AVNRT and AVRT (both P < 0.05), whereas it was unchanged in typical AFL (P = 0.50).

CONCLUSION

PPI after concealed entrainment is prolonged compared with TCL when the reentry circuit involves a slow conduction zone with a decremental conduction property such as the AV node.

Usefulness of combined CARTO electroanatomical mapping and manifest entrainment in ablating adenosine triphosphate-sensitive atrial tachycardia originating from the atrioventricular node vicinity

Background

By using a noncontact mapping system, adenosine triphosphate (ATP)-sensitive atrial tachycardia (ATP-AT) originating from the atrioventricular (AV) node vicinity was successfully ablated at the entrance to the slow conduction zone indicated by the manifest entrainment technique. We aimed to prospectively validate the efficacy of the combination of CARTO electroanatomical mapping and manifest entrainment in ablating this ATP-AT.

Methods

Of the 27 AT patients from January 2013 to March 2014, 6 patients with sustained ATP-AT were studied (age, 67±13 years; tachycardia cycle length, 350±95 ms). We first created the CARTO map during AT, and performed rapid pacing from the anterior right atrial wall (ARAW) and cavotricuspid isthmus (CTI) approximately 30 mm remote from the earliest activation site (EAS). We identified the site where manifest entrainment, defined as the orthodromic capture of the EAS with a long conduction time, was observed, and ablated the site approximately 20 mm remote from the EAS, between the pacing site and the EAS.

Results

Manifest entrainment was demonstrated in all patients paced from the ARAW (four patients) and from the CTI (two patients). Ablation at the prespecified site terminated AT in 6±3 s, and AT became no longer inducible in all patients. At the successful ablation sites, discrete atrial electrograms were recorded; however, low-amplitude, fractionated electrograms suggestive of slow conduction were not observed in all patients. The atrio-His interval during sinus rhythm remained unchanged (from 96±12 to 89±7 ms, p=NS). During 11±6 months, no patients showed AT recurrence and AV conduction abnormality.

Conclusion

CARTO mapping- and manifest entrainment-guided ablation strategy is effective and safe in the treatment of ATP-AT.

Long-term Outcomes of Ventricular Tachycardia Ablation in Different Types of Structural Heart Disease

Ventricular tachycardia (VT) often occurs in the setting of structural heart disease and can affect patients with ischaemic or nonischaemic cardiomyopathies. Implantable cardioverter-defibrillators (ICDs) provide mortality benefit and are therefore indicated for secondary prevention in patients with sustained VT, but they do not reduce arrhythmia burden. ICD shocks are associated with increased morbidity and mortality, and antiarrhythmic medications are often used to prevent recurrent episodes. Catheter ablation is an effective treatment option for patients with VT in the setting of structural heart disease and, when successful, can reduce the number of ICD shocks. However, whether VT ablation results in a mortality benefit remains unclear. We aim to review the long-term outcomes in patients with different types of structural heart disease treated with VT ablation.

Substrate Mapping for Ventricular Tachycardia: Assumptions and Misconceptions

Substrate mapping was developed to treat poorly tolerated infarct-related ventricular tachycardias (VTs). This concept was based on 30-year-old data derived from surgical and percutaneous mapping during sinus rhythm and VT that demonstrated specific electrograms (EGMs) that characterized the "arrhythmogenic substrate" of VT. Electrogram characteristics of the arrhythmogenic VT substrate during sinus rhythm included low-voltage, fractionation, long duration, split signals, and isolated late potentials as well as EGMs demonstrating adjacent early and late activation. Introduction of electroanatomical mapping (EAM) systems during the mid-1990s has allowed investigators to record electrograms in 3 dimensions and to identify sites assumed to represent the central common pathway ("isthmus") during re-entrant VTs. However, several important assumptions and misconceptions make currently used "substrate mapping" techniques inaccurate. These include: 1) re-entrant circuits are produced by fixed barriers of immutable "inexcitable" scar; 2) low voltage amplitude (≤0.5 mV) implies dense "inexcitable" scar; 3) isthmuses identified in patients with tolerated VTs using entrainment mapping are both valid and provide an accurate depiction of isthmuses in less hemodynamically tolerated VTs; and 4) current mapping tools and methods can delineate specific electrophysiologic features that will determine the barriers forming channels during re-entrant VTs. None of these assumptions has been validated and recent experimental and human data using higher resolution mapping with very small electrodes cast doubt on their validity. These data call for re-evaluation of substrate-mapping techniques to characterize the arrhythmogenic substrate of post-infarction VT. Standardization of recording techniques including electrode size, interelectrode spacing, tissue contact, catheter orientation, and wavefront activation must be taken into consideration.

Management of ventricular arrhythmias in structural heart disease

Ventricular arrhythmias (VA) are a source of significant morbidity and mortality in patients with structural heart disease (SHD). The advent of the implantable cardiac defibrillator (ICD) has had a positive effect on mortality, but the associated morbidity remains a significant problem. Modern treatment of VA has advanced far beyond medical therapy and includes strategies as simple as intelligent ICD programming and as complex as catheter ablation (CA). In these pages, the spectrum of management strategies will be discussed; from anti-arrhythmic drugs and ICD implantation and programming to CA and autonomic modulation. The focus of this review will be on strategies for secondary prevention of VA in patients with SHD, supported by clinical evidence for their utilization.

Recent developments in the ablation of ventricular arrhythmias

Catheter ablation for the management of recurrent ventricular arrhythmias (VAs) is an emerging technology, with good efficacy in selected patients. It is an effective treatment for recurrent VA and can terminate VA during electrical storm. Recent innovations enhance the accuracy of ventricular mapping, allowing for substrate modification while the patient remains in sinus rhythm, thus facilitating the treatment of different types of VA. Epicardial ablation is now a feasible option for treating VA and increases the likelihood of success in certain types of VA. Percutaneous hemodynamic support facilitates successful ablation during poorly tolerated VA. This article reviews recent advances in catheter ablation techniques for VA and approaches to the management of specific types of VA, with a view toward future developments.

The critical isthmus sites of ischemic ventricular tachycardia are in zones of tissue heterogeneity, visualized by magnetic resonance imaging

BACKGROUND

A need exists to develop alternative approaches to VT ablation that provide an improved delineation of the arrhythmogenic substrate.

OBJECTIVE

The aim of this study was to evaluate the hypotheses that: (1) the heterogeneous zone (HZ, a mixture of normal-appearing tissue and scar) in magnetic resonance imaging (MRI) contains the critical isthmus(es) for ventricular tachycardia (VT), (2) successful ablation of VT would include ablation in the HZ, and (3) inadequate ablation of HZ allows for VT recurrence.

METHODS

MRI and an electrophysiology study (EP) were performed in a model of chronic myocardial infarction in 17 pigs. In animals that were inducible for VT, ablations were done guided by standard EP criteria and blinded to the MRI. After ablation, electroanatomic mapping results were co-registered with MRI.

RESULTS

In 8 animals, 22 sustained monomorphic VTs were generated. The HZ was substantially larger in inducible (n = 8) compared with noninducible animals (n = 9) [25% ± 10% vs 13% ± 5% of total scar, respectively, P = .007]. Acutely, all targeted VTs were successfully ablated, and postprocedure analysis showed that at least 1 ablation was in the HZ in each animal. In 5 animals, a second EP and MRI were performed 1 week after ablation. Three animals had inducible VTs, and MRI showed that the HZ had not been completely ablated. In contrast, the 2 animals without inducible VT revealed no remaining HZ.

CONCLUSION

These findings show that MRI can define an HZ and determine the location of ablated lesions. The HZ may be a promising ablation target to cure ischemic VTs. Remnants of HZ after ablation may be the substrate for clinical relapses.

Endocardial and epicardial mapping and catheter ablation of post myocardial infarction ventricular tachycardia: A substrate modification approach

Ventricular tachycardia associated with prior myocardial infarction account for significant morbidity, mortality, and health care costs despite the favorable outcomes shown by ICD clinical trials. Catheter ablation has been increasingly used as an adjunctive therapy in the management of scar-related ventricular tachycardia. Novel technologies have facilitated the outcomes of current ablation strategies. Three-dimensional mapping systems have allowed identification of the scar substrate, its critical sites in the tachycardia circuit, and selection of ablation sites based on fairly precise electroanatomic substrate.

Epicardial Ablation of Ischemic Ventricular Tachycardia

Endocardial catheter ablation for ventricular arrhythmias in patients with ischemic cardiomyopathy decreases ventricular tachycardia (VT) episodes, and painful implantable defibrillator shocks and can be lifesaving in the context of VT storm. Unfortunately, up to approximately one-third of postinfarction VTs are not accessible for ablation from the endocardium. Percutaneous access to the epicardial space has allowed ablation of a portion of these circuits, although anatomic barriers, such as the phrenic nerve, coronary arteries, and intramural circuits, still limit success in some cases. Adhesions, most often due to prior cardiac surgery, frequently necessitate a surgical approach to the pericardial space.

Ventricular Tachycardia Ablation-For Whom, When, and How?

This article discusses how ventricular tachycardia ablation should be used, discusses which patients may derive benefit from this treatment, and highlights the best means of implementing it.

Catheter ablation of ventricular tachycardia. From indication to three-dimensional mapping technology

The majority of ventricular tachycardias (VTs) occurs in patients with structural heart disease, predominantly coronary heart disease. Implantable cardioverter defibrillators (ICDs) are first-line therapy in patients with VT and structural heart disease. In patients who receive an ICD after a spontaneous sustained VT, recurrent VT episodes or an electrical storm are major problems. In addition, in patients with an ICD implanted for primary prevention of sudden cardiac death, 20% will experience at least one VT episode within 3-5 years after ICD implantation. Catheter ablation has a high acute success rate in eliminating clinical VT. However, several factors make catheter ablation of VT more difficult than ablation of supraventricular tachyarrhythmias. (1) The infarct region is often large. (2) The induced VT can be unstable or hemodynamically only poorly tolerated and therefore "unmappable". (3) Though most commonly located in the subendocardium, the critical VT zone can occasionally be epicardial or intramural in location. (4) In many cases, several reentrant circuits may coexist making ablation of a single form of VT a palliative procedure which does not obviate the risk of sudden death. Thus, catheter ablation of sustained VT in the setting of structural heart disease can only be considered an adjunctive therapy which, in general, will require ICD therapy. Numerous "modern" mapping technologies have been developed, which have increased success rates of catheter ablation of VT in patients with and without structural heart disease. The aim of the present article is to review current three-dimensional mapping systems in comparison to conventional mapping and to describe a reasonable, tailored approach for the individual patient with VT.

Non-pharmacological management of ventricular tachycardia

Ventricular tachyarrhythmias (VTA), a major cause of sudden cardiac death, require meticulous management in order to prevent recurrent episodes. Recently, non-pharmacological interventions, including radiofrequency catheter ablation and implantable cardioverter defibrillators (ICD), have become important treatments of VTA. Catheter ablation is curative in a relatively high percentage of patients presenting with idiopathic monomorphic ventricular tachycardia (VT). For VT associated with structural heart disease, however, the efficacy of catheter ablation remains limited, and ICD is the first-line therapy. In a subset of patients presenting with recurrent episodes of ventricular fibrillation (VF), catheter ablation is a therapeutic option when the VF is triggered by specific premature ventricular complexes. In Japan, unlike in the United States and Europe, ICD have not yet been accepted as first-line prevention of sudden cardiac death caused by VTA. The efficacy of ICD is occasionally limited by intolerable complications, such as electrical storm, inappropriate shock delivery and infection. Catheter ablation and ICD therapy might need to be combined for problematic cases.

Comparison of mapping criteria for hemodynamically tolerated, postinfarction ventricular tachycardia

BACKGROUND

Mapping criteria for hemodynamically tolerated, postinfarction ventricular tachycardia (VT) have been evaluated in only small series of patients.

OBJECTIVES

The purpose of this study was to evaluate the utility of various mapping criteria for identifying a critical VT circuit isthmus in a post hoc analysis.

METHODS

Ninety VTs (cycle length 491 +/- 84 ms) were mapped in 48 patients with a prior myocardial infarction. The mapping catheter was positioned within a protected area of the reentrant circuit of the targeted VTs at 176 sites. All sites showed concealed entrainment. The predictive values of the following mapping criteria for a successful ablation site were compared: discrete isolated potential during VT, inability to dissociate the isolated potential from the VT, endocardial activation time >70 ms, matching electrogram-QRS and stimulus-QRS intervals, VT termination without global capture during pacing, stimulus-QRS/VT cycle length ratio <or=0.7, and postpacing interval. For each criterion, the receiver operating characteristic curve was constructed, and the area under the curve was calculated to assess the discriminatory value of the criterion.

RESULTS

Seventy-eight of 90 VTs (87%) were successfully ablated. The area under the receiver operating characteristic curve was largest (0.89) for matching stimulus-QRS and electrogram-QRS intervals. In combination with an isolated potential that could not be dissociated from the VT, the area under the receiver operating characteristic curve increased to 0.93.

CONCLUSION

At sites with concealed entrainment, matching stimulus-QRS and electrogram-QRS intervals were superior to other criteria in differentiating a critical isthmus from bystander or noncritical sites in postinfarction VT.

Ventricular Tachycardia/Ventricular Fibrillation Ablation in the Setting of Ischemic Heart Disease

Recurrent ventricular tachycardia (VT) in the setting of coronary artery disease is frequently a life-threatening electrophysiologic emergency. Even in patients with an implantable defibrillator, recurrent VT is frequently accompanied by repeated and disabling shock therapy. Catheter ablative therapy offers the ability to provide immediate control of recurrent VT. Long-term elimination of VT should be anticipated in most patients. This article reviews the strategies, tools, techniques, and expected outcome for catheter ablation of stable and unstable ventricular arrhythmias in the setting ischemic heart disease.