Radiofrequency Ablation of Idiopathic Left Anterior Fascicular Tachycardia

Left Anterior Fascicular Tachycardia. Introduction: A 45-year-old man with idiopathic ventricular tachycardia (VT) having a right bundle branch block configuration with right-axis deviation underwent au electrophysiologic test.
Methods and Results: Mapping demonstrated a site on the auterobasal wall of the left ventricle where there was an excellent pace map and an endocardial activation time of -20 msec, hut radiofrequency catheter ablation at this site was unsuccessful. At a nearby site, a presumed Purkinje potential preceded the QRS complex by 30 msec during VT and sinus rhythm, and catheter ablation was effective despite a poor pace map and an endocardial ventricular activation time of zero.
Conclusion: Idiopathic VT with a right bundle branch configuration and right-axis deviation may originate in the area of the left anterior fascicle. A potential presumed to represent a Purkinje potential may he more helpful than endocardial ventricular activation mapping or pace mapping in guiding ablation of this type of VT.     

Resetting of ventricular tachycardia: implications for localizing the area of slow conduction

Analysis of local endocardial electrograms recorded during reentrant ventricular tachycardia does not provide direct information as to the participation of the recording site in the tachycardia circuit. To determine if programmed electrical stimulation at the recording site can assist in localizing areas of slow conduction that are participating in the tachycardia circuit, seven patients with sustained monomorphic ventricular tachycardia were studied. The cardiac cycle was scanned with single stimuli delivered during ventricular tachycardia at multiple endocardial sites. In four patients, an endocardial site was identified at which stimuli advanced the tachycardia with marked conduction delay and without alteration of the ventricular activation sequence, as indicated by a lack of change in the configuration of the QRS complex and endocardial electrograms distant from the stimulation site. This finding was seen only during stimulation at sites displaying abnormal electrograms and is consistent with premature depolarization of an area of slow conduction within the tachycardia focus by stimuli delivered at or near that area. Attempted endocardial catheter ablation at or adjacent to these sites in three patients was followed by persistent noninducibility of ventricular tachycardia in one patient, marked modification of the configuration and cycle length of inducible tachycardia in one patient and transient noninducibility of tachycardia in one patient. Programmed electrical stimulation during ventricular tachycardia at sites with abnormal electrograms may provide information about the proximity of the stimulation site to the tachycardia circuit.     

Radiofrequency Catheter Ablation of Left Ventricular Outflow Tract Tachycardia from the Coronary Cusp: A New Approach to the Tachycardia Focus

INTRODUCTION: Idiopathic ventricular tachycardia (VT) originating from the left ventricular outflow tract (LVOT) is rare. Previously reported were two cases of LVOT tachycardia which were treated with radiofrequency (RF) catheter ablation through endocardial aortomitral continuity. We report here a case of a repetitive LVOT tachycardia in which the QRS morphology during VT exhibited an atypical left bundle branch block and inferior axis. Pace mapping revealed that the origin of this VT was very close to the left sinus of Valsalva. Transcoronary cusp RF catheter ablation abolished the VT in this patient and is a new approach for the treatment of this kind of VT. The application of this approach to the other types of VT has yet to be determined.     

Insights into the mechanism of sustained ventricular tachycardia after myocardial infarction in a closed chest porcine model using a multielectrode "basket" catheter

INTRODUCTION: Accurate analysis of the arrhythmia substrate is important for successful radiofrequency ablation of sustained ventricular tachycardia (VT) after myocardial infarction (MI). METHODS AND RESULTS: A multielectrode "basket" catheter capable of endocardial recording and pacing was inserted percutaneously into the left ventricle of post-MI swine for analysis of the mechanism of sustained VT. Sustained VT was induced in 42 of 61 pigs that survived an acute MI produced by percutaneous transluminal coronary angioplasty balloon occlusion of the left anterior descending coronary artery and injection of agarose gel beads. A multielectrode "basket" catheter (Constellation) with 64 electrodes was inserted in 35 of these animals for analysis of the VT. Induced VT had a cycle length of 179 +/- 25 msec at control and 230 +/- 43 msec after administration of intravenous procainamide. Presystolic electrical activity was recorded from at least 1 of 32 bipolar pairs of electrodes at a mean 40.7 +/- 23.6 msec prior to QRS onset. Isolated mid-diastolic potentials were recorded in 26 of 35 animals. In 22 animals, there were multiple isolated potentials recorded from adjacent electrode pairs. Isochronal maps demonstrated that these potentials returned to the systolic site of origin. Resetting of sustained VT by single premature ventricular stimuli was observed in 6 of 12 animals. Entrainment with overdrive pacing was seen in 19 of 26 animals with induced VT. Concealed entrainment was observed in ten animals. The mean stimulus to QRS interval was 45 +/- 28 msec. Concealed entrainment was observed from adjacent electrode pairs with different stimulus to QRS intervals. CONCLUSION: These data suggest that sustained VT in this model is due to reentry with an excitable gap. A multielectrode "basket" catheter is useful for analyzing the zone of slow conduction participating in the tachycardia circuit. Such analysis may provide useful information to guide successful catheter ablation of sustained VT after MI.     

Alternating and gradually changing narrow QRS complex tachycardia in a patient with heart failure: What is the mechanism?

A 23-year-old woman with palpitations for 9 years was referred for catheter ablation. ECG showed an irregular narrow complex tachycardia with alternating and gradually changing QRS morphologies after alternating and changing RR intervals, with a clear pattern of 2 alternating QRS complexes. An electrophysiology study was performed and confirmed that the mechanism of tachycardia was an automatic left-side His-Purkinje system (HPS) ventricular tachycardia. The gradually changing type-2 QRS complexes was the conduction delayed in the left anterior fascicle due to the short RR interval or the short left-side HH interval. Nine months after the index electrophysiology study, the patient encounter a progressive of heart failure with increased heart rate to 130-150 bpm during rest. Radiofrequency ablation was performed at the upper-septum for eliminating the tachycardia and resulted in complete atrioventricular block. A permanent pacemaker with left bundle branch pacing was implanted. Twelve months after the ablation, the enlarged heart shrink to normal with normal left ventricular ejection fraction. In conclusion, careful interpretation of the ECG can identify the sinus P waves followed by irregular narrow complexes, thus avoiding misdiagnosis and unnecessary treatment. Unifocal HPS tachycardia could present with alternating and gradually changing narrow QRS complexes tachycardia and lead to tachycardia cardiomyopathy. Electrophysiology study and catheter ablation were useful for the diagnosis and treatment of HPS tachycardia but with high risk of atrioventricular block. However, successfully elimination the tachycardia would resolve and reverse the enlarged heart and deteriorative heart function.     

Epicardial Macro-Reentrant Ventricular Tachycardia Exhibiting an Endocardial Centrifugal Activation Pattern in a Case with Arrhythmogenic Right Ventricular Cardiomyopathy

A 55-year-old man with arrhythmogenic right ventricular cardiomyopathy underwent catheter ablation of ventricular tachycardia (VT) with left bundle branch block and left superior axis QRS morphology with an early precordial transition. Endocardial mapping during the VT revealed a focal activation pattern from a small region of low voltage in the left ventricular (LV) septum. Despite earliest endocardial activation in the LV septum, epicardial mapping demonstrated a macro-reentrant circuit with successful catheter ablation at an inferior peritricuspid annular site. Activation from the reentrant circuit propagated through the scar area in the epicardial right ventricle to the remote endocardial LV breakout site.     

特发性室性心动过速射频导管消融标测方法探讨

目的探讨特发性室性心动过速（IVT）的标测方法.方法对52例行射频消融的IVT患者进行标测.39例源于右心室的IVT采用消融导管右心室起搏标测法,以起搏时与室性心动过速（室速）发作时的12导联心电图QRS波形态与振幅完全相同的起搏部位为消融靶点.12例起源于左心室的IVT以发作时消融电极导管在左心室内标测到较体表心电图QRS波提前≥20 ms的最早高频低振幅电位为消融靶点（激动顺序标测法）,1例左心室室速采用起搏标测法.结果左心室IVT消融成功率100%（13/13）,右心室IVT消融成功率94.87%（37/39）.结论起源于左心室的IVT宜采用激动顺序标测法,起源于右心室的IVT宜采用起搏标测法.     

Radiofrequency Catheter Ablation of Idiopathic Left Ventricular Tachycardia:

Idiopathic Left Ventricular Tachycardia. Introduction: Idiopathic left ventricular tachycardia with a QRS pattern of right bundle branch block and left-axis deviation constitutes a rare but electrophysiologically distinct arrhythmia entity. The underlying mechanism of this tachycardia, however, is still a matter of controversy. This report describes findings in a 42-year-old man who underwent successful radiofrequency catheter ablation of idiopathic left ventricular tachycardia.
Methods and Results: On electrophysiologic study, the tachycardia was reproducibly induced and terminated with double ventricular extrastimuli. Intravenous verapamil terminated the tachycardia whereas adenosine did not. Detailed left ventricular catheter mapping during sinus rhythm revealed a fragmented delayed potential at the mid-apical region of the inferior site near the posterior fascicle of the left bundle branch. At the same site, continuous electrical activity throughout the entire cardiac cycle was recorded during ventricular tachycardia. Repeated spontaneous termination of this continuous electrical activity in late diastole was followed immediately by termination of the tachycardia. Single application of radiofrequency current for 20 seconds at this site completely abolished inducibility of the tachycardia. After catheter ablation, at the identical site of preablation recording of the fractionated potential during sinus rhythm, no fragmented delayed activity could be recorded. There was no complication from the ablation procedure.
Conclusion: The preablation recordings of fragmented delayed potentials during sinus rhythm and continuous diastolic electrical activity during tachycardia, together with ablation characteristics and previously reported electrophysiologic properties of this arrhythmia, may further support microreentry as the underlying mechanism in idiopathic left ventricular tachycardia.     

Successful radiofrequency catheter ablation of epicardial left ventricular outflow tract tachycardia from the anterior interventricular coronary vein

We report a case of idiopathic left ventricular outflow tract (LVOT) tachycardia that was eliminated by a radiofrequency application from the anterior interventricular coronary vein (AIV). The ECG exhibited QRS complexes with an inferior axis and atypical left bundle branch block pattern with an early transition of the precordial R waves at V3. Several radiofrequency applications from the coronary cusps and endocardial LVOT were not effective. Radiofrequency applications in the AIV, where the activation preceded the onset of the QRS by 30 msec, successfully eliminated the tachycardia. The AIV may be an optional site for radiofrequency ablation of idiopathic epicardial LVOT tachycardia.     

Endocardial and Epicardial Ablation Guided by Nonsurgical Transthoracic Epicardial Mapping to Treat Recurrent Ventricular Tachycardia

Nonsurgical Epicardial Ablation. Introduction : An epicardial site of origin of ventricular tachycardia (VT) may explain unsuccessful endocardial radiofrequency (RF) catheter ablation. A new technique to map the epicardial surface of the heart through pericardial puncture was presented recently and opened the possibility of using epicardial mapping to guide endocardial ablation or epicardial catheter ablation. We report the efficacy and safety of these two approaches to treat 10 consecutive patients with VT and Chagas' disease.
Methods and Results : Epicardial mapping was carried out with a regular steerable catheter introduced into the pericardial space. An epicardial circuit was found in 14 of 18 mapable VTs induced in 10 patients. Epicardial mapping was used to guide endocardial ablation in 4 patients and epicardial ablation in 6. The epicardial earliest activation site occurred 107 ± 60 msec earlier than the onset of the QRS complex. At the epicardial site used to guide endocardial ablation, earliest activation occurred 75 ± 55 msec before the QRS complex. Epicardial mid-diastolic potentials and/or continuous electrical activity were seen in 7 patients. After 4.8 ± 2.9 seconds of epicardial RF applications, VT was rendered noninducible. Hemopericardium requiring drainage occurred in 1 patient; 3 others developed pericardial friction without hemopericardium. Patients remain asymptomatic 5 to 9 months after the procedure. Interruption during endocardial pulses occurred after 20.2 ± 14 seconds (P = 0.004), hut VT was always reinducible and the patients experienced a poor outcome.
Conclusion : Epicardial mapping does not enhance the effectiveness of endocardial pulses of RF. Epicardial applications of RF energy can safely and effectively treat patients with VT and Chagas' disease.     

Programmed electrical stimulation at potential ventricular reentry circuit sites. Comparison of observations in humans with predictions from computer simulations

The purpose of this study was to define specific types of resetting responses to programmed electrical stimulation during human ventricular tachycardia and to use computer simulations of reentry circuits to assess the possible mechanisms and pacing site location relative to the reentry circuit for each type of response. The effects of scanning single stimuli at 35 left ventricular endocardial sites during sustained monomorphic ventricular tachycardia in 12 patients were studied. In considering alterations in QRS configuration and the delay between the stimulus and the advanced QRS, we identified three types of resetting responses to scanning stimuli consistent with stimulation at sites in or near the reentry circuit at 12 abnormal endocardial sites in eight patients. Type 1: all capturing stimuli were followed after a delay by early QRS complexes that had the same configuration as the tachycardia complexes. Type 2: late stimuli reset tachycardia as in type 1 but early stimuli reset the tachycardia after altering the QRS configuration. Type 3: late stimuli reset tachycardia as in type 1, but early stimuli advanced tachycardia with a short stimulus to QRS delay without altering the QRS configuration. In the simulations, premature depolarization of sites in the circuit produced orthodromic and antidromic wavefronts. The orthodromic wavefront propagated through the circuit and exited the circuit at the same site as did the previous tachycardia wavefronts and advanced the tachycardia without altering the configuration of the advanced QRS. The antidromic wavefront of relatively late stimuli was confined within or near the circuit by collision with the orthodromic wavefront of the preceding tachycardia beat and failed to alter ventricular activation distant from the circuit. Therefore, the QRS configuration after the stimulus was unchanged. A type 1 response occurred when all capturing stimuli produced this effect. However, with increasing stimulus prematurity, the antidromic wavefront propagated farther before colliding with an orthodromic wavefront, and under some conditions, it exited the circuit from a site other than the original circuit "exit," and altered the ventricular activation sequence distant from the circuit and, therefore, the QRS configuration, producing a type 2 pattern. The type 3 pattern occurred when the antidromic wavefront of early premature beats captured the original circuit exit. The effect of a stimulus was dependent on the stimulus prematurity, the relative conduction times from the stimulation site to the potential sites of "exit" from the circuit, and the timing of the excitable gap at the stimulation site.(ABSTRACT TRUNCATED AT 400 WORDS)     

Mechanical interruption of postinfarction ventricular tachycardia as a guide for catheter ablation

BACKGROUND: Mechanical trauma has been described as a helpful guide for ablation of atrial tachycardias and accessory pathways. In postinfarction ventricular tachycardia (VT), the reentrant circuit is partly endocardial and therefore may be susceptible to catheter trauma. OBJECTIVES: The purpose of this study was to determine the prevalence and significance of VT termination resulting from catheter trauma. METHODS: A consecutive series of 39 patients (mean age 68 +/- 7 years, ejection fraction 0.25 +/- 0.02) underwent left ventricular mapping for postinfarction VT. Mapping was performed during 62 hemodynamically tolerated VTs (mean cycle length 451 +/- 88 ms). Only hemodynamically tolerated VTs that did not terminate spontaneously and VTs that were reproducibly inducible were included in the study. VT termination was considered mechanical only if it was not caused by a premature depolarization. RESULTS: In 13 of 62 VTs (21%) in 8 of 39 patients (21%), either VT terminated during catheter placement at a particular site (n = 7) or a previously reproducibly inducible VT became no longer inducible with the mapping catheter located at a particular site (n = 6). The stimulus-QRS interval was significantly shorter at sites where mechanical trauma affected the reentrant circuit compared with sites having concealed entrainment (102 +/- 56 ms vs 253 +/- 134 ms, P = .003). At the site that was susceptible to mechanical trauma, the pace map was identical or highly similar in 13 of 13 VTs. After radiofrequency ablation at these sites, the targeted VTs were no longer inducible. No patient had recurrence of the targeted VT during a mean follow-up of 15 +/- 11 months. CONCLUSIONS: Catheter contact at a critical endocardial site can interrupt postinfarction VT or prevent its induction. Radiofrequency ablation at sites of mechanical termination of VT has a high probability of success.     

Successful catheter ablation in a patient with polymorphic ventricular tachycardia

We describe a patient with polymorphic ventricular tachycardia (PVT)/ventricular fibrillation (VF) without organic heart disease who was cured by radiofrequency catheter ablation. The patient was a 65-year-old woman with a 10-year history of recurrent syncope. There was no evidence of organic heart disease, and the QT interval during sinus rhythm was borderline normal (corrected QT interval = 0.45 sec1/2). ECG recording during syncope showed PVT. On one occasion, PVT degenerated into VF. This PVT was always induced by a premature ventricular complex (PVC) originating from the right ventricular (RV) outflow tract. Rapid pacing (220 beats/min) at the site of PVC origin reproduced polymorphic change of the QRS wave on surface ECG that was similar to PVT. This suggests that the PVT originated from a single focus in the RV outflow tract. Catheter ablation was performed at the site of PVC origin. During 18-month follow-up, PVT/VF was not documented.     

Radiofrequency catheter ablation in recurrent ventricular tachycardia.

Catheter ablation by radiofrequency energy was carried out in 10 patients with one type of recurrent monomorphic sustained ventricular tachycardia resistant to medical antiarrhythmic management. Electrophysiological studies before ablation included activation and pace-mapping. In all patients, the origin of the tachycardia was localized in the left ventricle: in the septum in six, at the posterolateral wall in three and anterobasal in one. The earliest onset of endocardial activation preceding the QRS complex during ventricular tachycardia ranged between -45 and -90 ms. Transcatheter ablation was performed with a bipolar or quadripolar catheter using a radiofrequency generator (HAT 100, Osypka). No complications occurred during the ablation procedure. Thereafter, in all patients, the clinical tachycardia was no longer inducible by programmed stimulation. During a follow-up period of 22 to 32 months including eight patients, the tachycardia recurred in two; one of these patients subsequently died suddenly. A third patient had one episode of a new type of sustained ventricular tachycardia some hours after catheter ablation. In the remaining patients, there was no recurrence of symptomatic tachycardia under maintenance of the antiarrhythmic management which, prior to ablation had been ineffective. Thus, our preliminary results suggest that radiofrequency catheter ablation might be beneficial for these high risk patients.     

Case Report: Alternating Exit Sites in Reentry Circuit of Ventricular Tachycardia with Nonischemic Cardiomyopathy – Relationship between Ablation Site and Inner Loop

We present a patient with nonischemic cardiomyopathy who had ventricular tachycardia (VT) with QRS morphology alternans. VTs of two QRS morphologies (VT1 and VT2) exhibiting a right bundle branch block pattern with inferior axis was induced by ventricular pacing. The morphology of the QRS complex during VT1 exhibited more distinctively inferior axis than those during VT2. Induced VTs had similar morphologies to clinically the documented VTs. Pacemapping at anterolateral site of the left ventricle during sinus rhythm produced the same QRS complex of VT1 in a surface 12-lead electrocardiogram. A mapping study was performed with an electrode catheter located at the same site of LV during sustained VT1. The analysis of the local electrograms and postpacing interval during concealed entrainment at the catheter mapping revealed this pacing site was at the inner loop of the reentry circuit. Radiofrequency catheter ablation was performed at this site. The morphology of VT1 changed to different QRS morphology (VT2) during the first delivery of radiofrequency energy and was terminated after 20 seconds of the application. Then VT with alternans of QRS morphology and cycle length of VT1 and VT2 was induced by ventricular pacing, and was abolished by the second application of radiofrequency energy at this same site, suggesting that this site was located in the exit site close to inner loop of the reentry circuit and the alternans of QRS morphology was linked to the change of exit site.     

Pilsicainide-induced Brugada-type ECG and ventricular arrhythmias originating from the left posterior fascicle in a case with Brugada syndrome associated with idiopathic left ventricular tachycardia.

The patient was a 50-year-old male in 2002, who was first suspected of having a Brugada-type electrocardiogram (ECG). A drug challenge test using pilsicainide was performed and unmasked a typical coved type ST elevation followed by ventricular arrhythmias (VAs) manifesting a QRS pattern with a right bundle branch block and left axis deviation. Three years later, he was transferred to the emergency room due to a wide QRS tachycardia with the same QRS morphology as the VA that previously occurred in the drug challenge test. An ECG just after the recorded termination of the tachycardia exhibited a typical Brugada-type ECG. In an electrophysiological study, ventricular fibrillation could be easily induced with reproducibility. Since the clinical tachycardia could not be sustained by an isoproterenol infusion, mapping and catheter ablation targeting the pilsicainide-induced VAs was performed. The successful ablation site was the left mid-lower septal wall where a Purkinje potential was recorded and a false tendon was attached just to it.     

特发性室性心动过速的射频消融

目的:对经射频消融术证实的特发性室性心动过速的病例进行总结分析,探讨室性心动过速的发病状况、心电图特点、消融靶点的确定及消融结果。方法:对68 例特发性室性心动过速的起源部位和体表心电图进行分析,所有患者在诱发出室性心动过速后进行射频消融治疗,观察特发性室性心动过速的射频消融成功率和复发率以及它们和消融靶点的关系。结果:本组特发性室性心动过速患者中右室室性心动过速较左室室性心动过速多见。右室特发性室性心动过速心电图表现为左束支传导阻滞,左室特发性室性心动过速心电图则多表现为右束支传导阻滞。消融靶点的确定右室特发性室性心动过速主要采用起搏标测法,左室特发性室性心动过速主要采用激动顺序标测法。右室流出道室速组在起搏标测时起搏ECG和VT时ECG的12导联QRS波完全相同处消融成功率较高。结论:室性心动过速发作时的体表心电图可初步估计特发性室性心动过速的起源部位,射频消融术治疗特发性室性心动过速成功率高,并发症少。     

Successful radiofrequency catheter ablation of incessant ventricular tachycardia with a delta wave-like beginning of the QRS complex

Ventricular tachycardia with a delta wave-like beginning of the QRS complex is considered to be refractory to endocardial catheter ablation because it originates from the epicardial region. A 45-year-old woman had incessant ventricular tachycardia with a delta wave-like beginning of the QRS complex which was resistant to several antiarrhythmic drugs. The origin of the arrhythmia was at the mitral annulus on the antero-lateral left ventricular wall. The earliest endocardial activation preceded the QRS complex by 18 msec. After 7 sec of endocardial radiofrequency application ventricular tachycardia was terminated. During a 2 year follow-up ventricular tachycardia did not recur and only small numbers of premature ventricular contractions (< 100/day) were noted. VT with delta wave-like QRS morphology which originates from the basal region of the ventricle may be treated successfully with radiofrequency catheter ablation using an endocardial approach.     

Characteristics of Local Electrograms with Diastolic Potentials: Identification of Different Components of Return Pathways in Ventricular Tachycardia

Background:Diastolic potentials are often sought as a possible site for catheter ablation in post-infarct ventricular tachycardia. However, delivery of energy at such sites is often unsuccessful. The purpose of this study was to determine the characteristics of local electrograms with diastolic potentials and to identify activation pattern which might indicate the critical portion of the return path of the ventricular tachycardia reentry circuit.Methods: In 17 patients with post-myocardial infarction ventricular tachycardia, 30 ventricular tachycardias were mapped with an 112 bipolar endocardial balloon at the time of surgery. Diastolic mapping of the return tract in ventricular tachycardia was performed. Four activation patterns were observed (15 figure 8 patterns, 2 circular patterns, 2 biregional patterns and 11 monoregional patterns). Of 3,360 local electrograms, 207 (6.2%) demonstrated a diastolic potential in ventricular tachycardia. They were classified into following four categories, based on the appearance and timing of the systolic component. Type A-1 electrogram: systolic activation was of low amplitude (<2 mV) and was prolonged (100 msec), but preceded the onset of the surface QRS in ventricular tachycardia. Type A-2 electrogram: systolic activation was of low amplitude, was prolonged, but followed the onset of the surface QRS. Type B electrogram: systolic electrogram was fractionated, but relatively normal amplitude (2.0–3.6 mV). Type C electrogram: systolic electrogram was almost normal.Results: Of all electrograms with diastolic potentials, three type A-1 electrograms (1.4%) were located at the exit of the return pathway, 11 type A-1 electrograms (5.3%) were located at the pre-exit site. No type A-1 was found at an entrance/bystander area. 21 type A-2 electrograms (10.1%) were at the pre-exit and 83 type A-2 electrograms (40.2%) were located at the entrance/bystander area, but such electrograms were never found at the exit site. 71 type B electrograms (34.3%) and 18 type C electrograms (8.7%) were located at the entrance/bystander area. To distinguish the type A-2 electrograms at the pre-exit site from those at the entrance/bystander area, the diastolic potential to QRS interval was measured. This interval at the pre-exit was significantly shorter than that at the entrance/bystander area (–47.2 ± 10.7 vs –96.3 ± 31.3 msec, p = 0.0001).Conclusion: Type A-1 electrograms indicated the exit or pre-exit site of return pathway. Type A-2 electrograms with diastolic potential to QRS interval <–50 msec indicated the pre-exit site. However, the other types of local electrograms with diastolic potential did not indicate the critical portion of the ventricular tachycardia circuit. These observations may be helpful during catheter mapping and ablation of patients with post-infarct ventricular tachycardia.Condensed Abstract. Diastolic potentials are often sought to direct catheter ablation in post-infarct ventricular tachycardia. We investigated the characteristics of local electrograms showing diastolic activity in an attempt to determine whether critical portions of the ventricular tachycardia circuit could be identified by a typical signature. In 17 patients with a remote myocardial infarction, 30 ventricular tachycardias were mapped with 112 bipolar endocardial balloon at the time of surgery. Diastolic potentials in association with low amplitude (<2 mV) and prolonged (100 msec) systolic electrograms preceding the onset of QRS were found at the exit site and pre-exit site of return pathway. A similar systolic electrogram occurring after QRS onset with a diastolic potential to QRS interval of <–50 msec was found at the pre-exit site. However, other local electrograms with diastolic activity were at sites remote from the exit or pre-exit of the return pathway. These observations may be helpful during catheter mapping and ablation in patients with ventricular tachycardia.     

Ablation of ventricular tachycardia by isolating the critical site in a patient with arrhythmogenic right ventricular cardiomyopathy

We describe a patient with arrhythmogenic right ventricular cardiomyopathy in whom ventricular tachycardia (VT) was ablated by isolating a relatively large area of the critical site using catheter ablation. Endocardial mapping showed abnormal fragmented electrograms with delayed potential (DP) from an entire area of the aneurysm. Pace mappings from the aneurysm produced a QRS morphology identical to that of clinical VT. After catheter ablation was performed at the exit site of the VT critical area, programmed stimulation inside the aneurysm captured the DP but not the QRS complexes. These data suggest that VT can be ablated successfully by isolation of the critical area.