Diastolic potentials observed in idiopathic left ventricular tachycardia

Radiofrequency catheter ablation (RF-CA) has demonstrated a high success rate in eliminating idiopathic left ventricular tachycardia (ILVT), and the target site is determined by the score of pace mapping or the Purkinje potential (PP) preceding the onset of the ventricular activation, which is considered to indicate the exit site of the reentrant circuit. However, only a few reports have described the potential obtained from the slow conduction zone. RF-CA was successfully performed in 8 patients with ILVT. Careful mapping of the left ventricle during tachycardia was carried out to find the diastolic potential (DP). A DP was obtained in 4 patients (group 1), but not in 4 others (group 2). The local electrogram was recorded from the distal tip of the ablation catheter during the RF current application in order to investigate the pattern of termination of ILVT. A DP was recorded at the point where the catheter was slightly pulled back to a site proximal to the exit site of the reentrant circuit at the left interventricular basal septum. In group 1, conduction block between the DP and PP eliminated ILVT in 3 out of 4 cases, and 1 case showed conduction block between the DP and ventricular potential. In 2 out of 4 patients in group 2, the local electrogram showed conduction block between PP and the ventricular potential when VT terminated. The ablation site in group 1 was located relatively more basal than that in group 2 in anatomy. A DP was obtained in a half of the cases with ILVT and RF-CA at this site could eliminate ILVT. A DP was obtained at a site relatively basal to the exit of the reentrant circuit and it is considered that this is a useful marker in terms of the successful ablation of ILVT.     

Successful catheter ablation of idiopathic left ventricular tachycardia during sinus rhythm

Successful catheter ablation of idiopathic left ventricular tachycardia (ILVT) can be performed at the site of the earliest Purkinje potential or at the site with recording of diastolic and presystolic Purkinje potentials simultaneously during ventricular tachycardia (VT). However, these critical potentials might be difficult to be recorded and mapped in some patients during VT. It is rare to report the ablation of ILVT during sinus rhythm. We present a case with ILVT who received successful catheter ablation during sinus rhythm.     

Structure of the reentrant circuit of idiopathic left ventricular tachycardia: new insights into the role of the Purkinje network

In idiopathic left ventricular tachycardia (ILVT), the reentrant circuit is considered to involve the Purkinje system, and the Purkinje potential (P-potential) appears to be a marker for successful ablation. However, the characteristics of the reentrant circuit in ILVT have not yet been defined. In 2 cases of ILVT, we performed detailed mapping along the left ventricular septum during VT and sinus rhythm. ILVTs were successfully ablated at the posteroapical area of the left ventricular septum where the high frequency P-potential was recorded and this portion was considered to be the exit site of the reentrant circuit. A small P-potential was also recorded at the portion proximal to the exit site, and it preceded the P-potential at the exit site. However, the local ventricular electrogram at the exit site preceded that at the proximal site during VT. Moreover, the small P-potential was orthodromically entrained by ventricular pacing from the proximal site. These findings suggest that the reentry circuit of ILVT appeared to have considerable size.     

A Case with Occurrence of Antidromic Tachycardia After Ablation of Idiopathic Left Fascicular Tachycardia: Mechanism of Left Upper Septal Ventricular Tachycardia

A 36‐year‐old male presented with verapamil‐sensitive narrow QRS tachycardia. The patient underwent the catheter ablation of common idiopathic left fascicular ventricular tachycardia (ILVT) 2 years ago. During narrow QRS tachycardia, the diastolic and presystolic potentials (P1 and P2) were recorded at the left septum. Activation sequences of P1 and P2 were opposite from those in common ILVT. Entrainment of P1 at the upper septum exhibited concealed fusion and S‐QRS equal to P1‐QRS. Radiofrequency current to P1 suppressed VT. Idiopathic left upper septal VT might be the antidromic macroreentry of the common form of ILVT.     

Radiofrequency catheter ablation of left ventricular tachycardia in the normal heart

Background: Radiofrequency (RF) catheter ablation is a safe and effective cure for many forms of supraventricular tachycardia. Its efficacy in the cure of right ventricular outflow tract tachycardia, and some forms of left ventricular tachycardia in patients with left ventricular dysfunction, has also been shown. In contrast limited data are available to assess the role of RF catheter ablation in treating idiopathic left ventricular tachycardia (ILVT), an unusual form of tachycardia occurring in patients without demonstrable heart disease.
Aim: To examine the efficacy and safety of RF catheter ablation in patients with ILVT.
Methods: Three patients without structural heart disease and with recurrent drug-refractory ILVT (right bundle branch block and left axis morphology) underwent electrophysiologic study (EPS) to initiate and localise the site of origin of their VT. RF catheter ablation of the VT focus was performed, with success being defined as failure to reinduce VT during incremental infusion of isoprenaline.
Results: In all three patients VT was inducible by rapid right atrial pacing and/or programmed ventricular stimulation, and could be terminated by intravenous verapamil. RF catheter ablation was successful in all patients. The site of successful ablation was common to each patient and was localised to the infero-apical aspect of the left ventricular septum. It was characterised by the recording of the earliest presystolic 'P' potential during both sinus rhythm and induced ILVT. No complications occurred during the procedure. During follow-up periods ranging from six to 12 months there were no symptomatic or documented episodes of recurrent ILVT.
Conclusions: We conclude that ILVT can be safely and effectively cured by RF catheter ablation.     

Novel mechanism of postinfarction ventricular tachycardia originating in surviving left posterior Purkinje fibers

BACKGROUND: Other than bundle branch reentry and interfascicular reentry, monomorphic postmyocardial infarction (post-MI) reentrant ventricular tachycardia (VT) including the His-Purkinje system has not been reported. Verapamil-sensitive idiopathic left VT includes the left posterior Purkinje fibers but develops in patients without structural heart disease. OBJECTIVES: The purpose of this study was to describe a novel mechanism of reentrant VT arising from the left posterior Purkinje fibers in patients with a prior MI. METHODS: The study consisted of four patients with a prior MI and symptomatic heart failure who underwent electrophysiologic study and catheter ablation for VT showing right bundle branch block (n = 3) or atypical left bundle branch block (n = 1) morphology with superior axis. In two patients, the VT frequently emerged during the acute phase of MI and required emergency catheter ablation. RESULTS: Clinical VT was reproducibly induced by programmed stimulation. In three patients, both diastolic and presystolic Purkinje potentials were sequentially recorded along the left ventricular posterior septum during the VT, whereas in the fourth patient, only presystolic Purkinje potentials were observed. During entrainment pacing from the right atrium, diastolic Purkinje potentials were captured orthodromically and demonstrated decremental conduction properties, whereas presystolic Purkinje potentials were captured antidromically and appeared between the His and QRS complex. Radiofrequency energy delivered at the site exhibiting a Purkinje-QRS interval of 58 +/- 26 ms successfully eliminated the VTs without provoking any conduction disturbances. CONCLUSION: Reentrant monomorphic VT originating from the left posterior Purkinje fibers, which is analogous to idiopathic left VT, can develop in the acute or chronic phase of MI. Catheter ablation is highly effective in eliminating this VT without affecting left ventricular conduction.     

Comparison of Presystolic Purkinje and Late Diastolic Potentials for Selection of Ablation Site in Idiopathic Verapamil Sensitive Left Ventricular Tachycardia

BACKGROUND: Idiopathic verapamil-sensitive left ventricular tachycardia (ILVT) is the most common form of idiopathic left ventricular tachycardia (VT). Different methods have been proposed for ablation of ILVT. METHODS: Between June 2002 and February 2004, 15 patients (12 men; age 28 +/- 11 years, range 12 to 51) with ILVT underwent radiofrequency (RF) ablation at our center. We retrospectively assessed the significance of recording purkinje potential (PP) and late diastolic potential (DP) and its effect on selection of ablation target and number of RF application. RESULTS: Sixteen VTs were observed. The clinical VT had either RBBB and left axis morphology (14 cases) or RBBB and right axis morphology (2 cases). The QRS duration during tachycardia was 124 +/- 12 ms and the tachycardia cycle length was 356 +/- 53 ms. DP and PP were recorded at the targeted area for RF ablation in 11 and 9 patients respectively. The PP-Q interval, DP-Q interval and DP width were 18 +/- 4, 53 +/- 18 and 14 +/- 8 ms, respectively. The number of RF application was 7.2 +/- 4.3. Fewer applications were needed in whom RF ablation was initially targeted to PP (with or without DP) recording site (10 patients, 4.7 +/- 1.8) compared to those targeted to DP recording site (5 patients, 12.2 +/- 3.3) ( P < 0.05). CONCLUSION: Compared to DP alone, earliest PP (with or without concomitant DP) might be superior for selection of target site of RF ablation in patients with ILVT.     

Demonstration of the reentrant circuit of verapamil-sensitive idiopathic left ventricular tachycardia: direct evidence for macroreentry as the underlying mechanism

The exact reentrant circuit of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) remains unclear. This case report demonstrates the reentrant circuit of ILVT. A 20-pole electrode catheter was placed along the left posterior fascicle during electrophysiologic study. ILVT was reproducibly induced by programmed ventricular stimulation. During the tachycardia, sequential diastolic potentials bridging the entire diastolic period were observed in the recordings from the electrodes positioned from left ventricular mid-septum to inferoapical septum. The slow conduction zone appeared to be composed of a false tendon in this patient. Entrainment of the ILVT from the right ventricular outflow tract at a different pacing cycle length revealed that a dominant conduction delay occurred at the proximal site of the slow conduction zone. Entrainment studies from several sites on the left ventricular septum confirmed that these sites where sequential electrical activity was recorded were included within the reentrant circuit. However, the left posterior fascicle itself seemed to be a bystander. This report provides the direct evidence of macroreentry as the underlying mechanism of this ILVT, adjacent to the left posterior fascicle.     

Ablation of postinfarction ventricular tachycardia guided by isolated diastolic potentials.

Frequent recurrences of ventricular tachycardia (VT) despite implantable cardioverter-defibrillator (ICD) and antiarrhythmic drug therapy are a typical indication for catheter ablation. We performed endocardial mapping of an haemodynamically tolerated VT in a 67-year-old male patient. Isolated diastolic potentials (IDPs) of similar morphology were recorded during atrial paced rhythm at baseline and during monomorphic VT. The isolated potentials were required for initiation and maintenance of ventricular arrhythmia. These diastolic electrograms were considered to be part of the reentry circuit, as they remained constantly associated with VT during oscillations of cycle length and resetting. Validation of the ablation target was not performed by exact entrainment pacing in order to test the predictive value of the observed diagnostic phenomena. Radiofrequency (RF) energy applications were successful at the site where IDPs were recorded during atrial paced rhythm and VT. Ablation decreased the need for ICD therapies effectively in a patient with scar-related, slow VT.     

Retrograde Purkinje Potential Activation During Sinus Rhythm Following Catheter Ablation of Idiopathic Left Ventricular Tachycardia

Idiopathic Left VT and Purkinje Potentials . We describe two patients with idiopathic left ventricular tachycardia that were cured by radiofrequency catheter ablation. Tachycardia was inducible by ventricular stimulation and was verapamil sensitive. Two distinct presystolic potentials (PI and P2) were recorded during tachycardia in the mid-septal or inferoapical area, but only one potential (P2) was recorded during sinus rhythm. After catheter ablation at this site, the PI potential was noted after the QRS complex during sinus rhythm, while the P2 was still observed before the QRS complex. The P1 potential showed a decremental property during atrial or ventricular pacing. These data suggest that Purkinje tissue with decremental properties was responsible for the tachycardia mechanism, and that the reentry circuit involving this tissue is likely to be of considerable size.     

Verapamil-Sensitive Left Anterior Fascicular Ventricular Tachycardia: Results of Radiofrequency Ablation in Six Patients

Verapamil-Sensitive Left Anterior Fascicular VT. Introduction: Verapamil-sensitive left ventricular tachycardia (VT) with a right bundle branch block (RBBB) configuration and left-axis deviation bas been demonstrated to arise from the left posterior fascicle, and can be cured by catheter ablation guided by Purkinje potentials. Verapamil-sensitive VT with an RBBB configuration and right-axis deviation is rare, and may originate in the left anterior fascicle. Methods and Results: Six patients (five men and one woman, mean age 54 ± 15 years) with a history of sustained VT with an RBBB configuration and right-axis deviation underwent electrophysiologic study and radiofrequency (RF) ablation. VT was slowed and terminated by intravenous administration of verapamil in all six patients. Left ventricular endocardial mapping during VT identified the earliest ventricular activation in the anterolateral wall of the left ventricle in all patients. RF current delivered to this site suppressed the VT in three patients (ablation at the VT exit). The fused Purkinje potential was recorded at that site, and preceded the QRS complex by 35, 30, and 20 msec, with pace mapping showing an optimal match between the paced rhythm and the clinical VT. In the remaining three patients, RF catheter ablation at the site of the earliest ventricular activation was unsuccessful. In these three patients, Purkinje potential was recorded in the diastolic phase during VT at the mid-anterior left ventricular septum. The Purkinje potential preceded the QRS during VT by 66, 56, and 63 msec, and catheter ablation at these sites was successful (ablation at the zone of slow conduction). During 19 to 46 months of follow-up (mean 32 ± 9 months), one patient in the group of ablation at the VT exit bad sustained VT with a left bundle branch block configuration and an inferior axis, and one patient in the group of ablation at the zone of slow conduction experienced typical idiopathic VT with an RBBB configuration and left-axis deviation. Conclusion: Verapamil-sensitive VT with an RBBB configuration and right-axis deviation originates close to the anterior fascicle. RF catheter ablation can be performed successfully from the VT exit site or the zone of slow conduction where the Purkinje potential was recorded in the diastolic phase.     

Negative participation of the left posterior fascicle in the reentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia

Left posterior fascicle and idiopathic Left VT. The left posterior fascicle may be a bystander of the circuit of verapamil-sensitive idiopathic left ventricular tachycardia. During ventricular tachycardia (VT), 3 sequences of potentials were seen at the left posterior septum: diastolic Purkinje potentials propagating from base to apex and presystolic left posterior fascicular potentials and systolic left ventricular (LV) myocardial potentials propagating in the reverse direction. Selective capture of the left posterior fascicle by the sinus beat did not affect the VT cycle length. Entrainment pacing revealed that the retrograde limb of the circuit was not the left posterior fascicle, but the LV myocardium.     

Mid-Diastolic Potential is Related to the Reentrant Circuit in a Patient with Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia

Mid-Diastolic Potential in Idiopathic VT. We report a case of verapamil-sensitive idiopathic ventricular tachycardia in which a mid-diastolic potential (MDP) 45 msec preceding the Purkinje potential ( P potential) was recorded. Pacing during the tachycardia caused concealed entrainment, and the stimulus–QRS interval was equal to the P potential–QRS interval. The interval between the last pacing stimulus and the next P potential (postpacing interval) was longer than the ventricular tachycardia cycle length, but the MDP was orthodromically activated. These findings suggest that the MDP was on the reentrant circuit and the P potential was not on the reentrant circuit, but a bystander.     

Entrance Site of the Slow Conduction Zone of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia:

Entrance Site in ILVT. The entrance site of the slow conduction zone was identified by entrainment study in an 18 year-old woman with verapamil-sensitive idiopathic left ventricular tachycardia. Radiofrequency catheter ablation at this site eliminated the tachycardia. The entrance site was at a mid-septal location and was more than 2 cm away from the exit site. Electrophysiologic findings suggested macroreentry in the Purkinje system as the mechanism of idiopathic left ventricular tachycardia.     

Effects of verapamil and lidocaine on two components of the re-entry circuit of verapamil-senstitive idiopathic left ventricular tachycardia

OBJECTIVES: We characterized pharmacologically the slow conduction zone of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) with regard to the late diastolic potential (LDP). BACKGROUND: We showed that the slow conduction zone of ILVT could be divided into two components by LDP; that is, the distal component with a tachycardia-dependent conduction delay property and the proximal one without it. METHODS: Electrophysiologic studies were performed in eight consecutive patients. The LDP was recorded during left ventricular (LV) mapping during ILVT. Entrainment was performed from the right ventricular outflow tract while recording LDP. The effects of lidocaine (1 mg/kg body weight) and verapamil (0.5 or 1.0 mg) were examined during entrainment. RESULTS: The LDPs preceding the Purkinje potential (PP) were serially recorded from the upper third to the middle of the LV septum along the narrow longitudinal line. The ventricular tachycardia (VT) cycle length increased after lidocaine (p < 0.05), and further after verapamil (p < 0.05). The increments in the VT cycle length after administration of the drugs strongly correlated with those in LDP-PP (r > 0.9 for both drugs). The interval from the ventricular potential to LDP was unchanged after administration of the drugs. In one patient, verapamil terminated VT by local conduction block between LDP and PP. The LDP-PP measured during entrainment increased after lidocaine, and further after verapamil, whereas the interval from the stimulus to LDP remained unchanged. CONCLUSIONS: The component distal to LDP is mainly calcium channel-dependent and partly depressed sodium channel-dependent. The proximal component is considered to be sodium channel-dependent (normal).     

Idiopathic left ventricular tachycardia: assessment and treatment

Idiopathic left ventricular tachycardia (VT) has been classified into three subgroups according to mechanism: verapamil-sensitive, adenosine-sensitive, and propranolol-sensitive types. VT can be categorized also into left fascicular VT and left outflow tract VT. Although the mechanism of fascicular VT is verapamil-sensitive reentry, the mechanism of left outflow tract VT is not homogeneous. Fascicular VT can be classified into three subtypes: (1) left posterior fascicular VT with a right bundle branch block (RBBB) and superior axis configuration (common form); (2) left anterior fascicular VT with RBBB and right-axis deviation configuration (uncommon form); and (3) upper septal fascicular VT with a narrow QRS and normal axis configuration (rare form). Posterior and anterior fascicular VT can be successfully ablated at the mid-septum guided by a diastolic Purkinje potential or at the VT exit site guided by a fused presystolic Purkinjepotential. Upper septal fascicular VT also can be ablated at the site indicated by a diastolic Purkinje potential. The mechanism of left ventricular outflow tract VT is most likely adenosine-sensitive triggered activity. This VT can be classified into three subtypes according to the location where catheter ablation is successful, i.e., (1) endocardial origin; (2) coronary cusp origin; and (3) epicardial origin. The R-wave duration and R/S-wave amplitude in V1/V2 can be used to differentiate coronary cusp VT from other types of outflow tract VT. Recognition of the characteristics of the various forms of this group of arrhythmias should facilitate appropriate diagnosis and therapy.     

Radiofrequency ablation of idiopathic left ventricular tachycardia at the site of earliest activation as determined by noncontact mapping

INTRODUCTION: The most effective method for guiding radiofrequency (RF) ablation of idiopathic left ventricular tachycardia (ILVT) has yet to be determined. We investigated the use of noncontact mapping in five patients with this condition. METHODS AND RESULTS: The multielectrode array was positioned in the left ventricular apex via the retrograde approach. Isopotential color maps of ILVT were examined to determine the site of earliest endocardial activation. The ablation catheter was steered to the target site using the locator signal. Pace mapping was performed and contact electrograms examined for diastolic potentials. RF energy was applied to the target site. Sustained ventricular tachycardia was induced in 2 patients and nonsustained ventricular tachycardia in 3. The site of earliest activation was at the apical septum in 3, the inferior apex in 1, and the base of the inferior wall in 1. Mean timing was 21 +/- 10 msec before onset of the surface QRS. Diastolic activity was visualized with noncontact mapping at the base of the septum in 1 patient. A Purkinje potential was seen at the ablation site in only 1 patient. No diastolic activity was seen in the remaining 3 patients. Tachycardia was successfully terminated in all 5 patients with a median of four RF applications. No patient suffered a recurrence after 9.6 +/- 4.7 months of follow-up. CONCLUSION: By identifying the precise site of earliest activation during ILVT, noncontact mapping has been shown to be an effective and safe method for guiding RF ablation.     

特发性左心室心动过速致心律失常基质的电解剖差异

目的 探索特发性左心室心动过速（ILVT）和房室折返性心动过速（AVRT）患者左心室传导系统和缓慢传导区电解剖变异情况.方法 选取2009年5月至2011年12月20例成功消融的ILVT患者（ILVT组）,年龄20～51（37±7）岁,男16例;26例AVRT患者（对照组）,年龄25～51（38±8）岁,男20例,窦性心律下分别建立左心室三维电解剖标测,标记左心室传导系统、缓慢传导区及其交汇区,分析变异情况.ILVT组患者依据消融关键区和拖带刺激进行消融.结果 根据浦肯野电位分布将传导系统变异分为3个亚型：两分支、三分支和扇形分布于左心室间隔,两组间各分支长度差异无统计学意义（P＞0.05）.缓慢传导区在ILVT中亦存在变异：17例位于后下间隔,1例位于下间隔近心尖处,2例于中、后间隔处.浦肯野电位和舒张期电位间存在面积约（1.5±0.4） cm2的交汇区,该处拖带和消融均取得成功.6例AVRT患者于后下间隔处记录到缓慢传导区,长度[12.0～28.7 （20.4±4.7） mm对11.8～ 20.3（16.1±3.3） mm,t=2.1,P=0.048]、面积[1.6～ 3.5（2.5±0.5） cm2对1.4～2.1 （1.8±0.3） cm2,t=3.0,P=0.006]显著小于ILVT组.结论 左心室传导系统和缓慢传导区存在多种变异,使ILVT折返机制更为复杂.     

Idiopathic left ventricular tachycardia with a change from left to right axis deviation during radiofrequency catheter ablation

A 62 year-old-woman presented with a right bundle branch block (RBBB) and left axis deviation (LAD) tachycardia. Radiofrequency (RF) energy was delivered to the left posterior fascicle (LPF) where 2 presystolic Purkinje potentials (P1 and P2) preceding onset of the QRS complex were recorded. During RF energy applications, the QRS morphology of the tachycardia changed from RBBB and LAD to RBBB and right axis deviation without termination of the tachycardia. The Purkinje potential was observed following the QRS complex during the tachycardia because of conduction block of the LPF distal to the reentry circuit due to RF catheter ablation.     

Sustained monomorphic ventricular tachycardia ablation from the aortic sinus of valsalva

INTRODUCTION: The aim of this study was to delineate the electrophysiologic mechanisms of a novel type of ventricular tachycardia (VT) originating from the aortic sinus of Valsalva. METHODS AND RESULTS: Endocardial mapping was performed in four patients with symptomatic VT originating from the aortic sinus of Valsalva. Two patients suffered from dilative cardiomyopathy; the other two patients had no structural heart disease. Five VTs could be induced and terminated by programmed ventricular stimulation. Successful ablation was performed in the noncoronary sinus of Valsalva in three VTs and in the left aortic sinus in two. Abnormal (diastolic or presystolic) potentials were recorded during sinus rhythm (mean interval from the end of QRS complex to the potential 121+/-98 msec) and during VT (mean interval from the potential to QRS complex 64+/-45 msec) at effective sites in the aortic sinuses of Valsalva. Concealed entrainment was demonstrated at all successful sites. VT recurred in one patient after 1 month, whereas no recurrences were observed during follow-up of 8+/-6 months in the other three patients. CONCLUSION: Reentry constitutes one mechanism of VT originating from the aortic sinus of Valsalva. Entrainment mapping is useful to characterize the reentrant circuit of these VTs and to guide ablation.