Contribution of myocardium responsible for ventricular tachycardia to abnormalities detected by analysis of signal-averaged ECGs.

BACKGROUND. Current methods of signal-averaged ECG analysis interrogate the terminal 40 msec of the QRS complex and/or the ST segment and have a low positive-predictive accuracy for detecting vulnerability to sustained ventricular tachycardia (VT). The extent to which abnormalities detected during these ECG intervals are generated by myocardial tissue responsible for VT has not been well defined. The purpose of this study was to determine when, during sinus rhythm, myocardium responsible for VT is activated. METHODS AND RESULTS. Three-dimensional ventricular activation maps were analyzed during sinus rhythm and during 10 VTs in eight patients with healed myocardial infarctions undergoing arrhythmia surgery for sustained monomorphic VT. The mechanism of VT was focal in five instances and macroreentrant in five. During sinus beats, myocardium responsible for all focal VTs activated 43 +/- 38 msec before the onset of the terminal 40-msec interval of the QRS complex. During sinus rhythm, activation of the myocardium critical to macroreentrant VT began 72 +/- 13 msec before the onset of the terminal QRS interval and in only three instances extended 2-25 msec into the terminal 40 msec of the QRS complex. Electrograms recorded during the ST segment represented late activation of epicardial sites overlying zones of infarction that were temporally and spatially remote from tissue critical to VT. CONCLUSIONS. Current methods of signal-averaged ECG analysis limiting interrogation to the terminal QRS/ST segment exclude detection of > 95% of the signals generated by myocardium responsible for sustained VT. These results establish a pathophysiological basis for expanding signal-averaged ECG analysis to include more of the cardiac cycle.     

Discrete systolic potentials during ventricular tachycardia in patients with prior myocardial infarction

INTRODUCTION: Isolated diastolic potentials have been found to be helpful in identifying critical sites for ablation of ventricular tachycardia (VT) in patients with coronary artery disease. However, discrete potentials that occur during systole have not been previously described. The purpose of this study was to determine the significance of discrete systolic potentials during VT in patients with coronary artery disease. METHODS AND RESULTS: Twenty-seven patients with a mean age of 66 +/- 12 years ( +/- standard deviation) who had coronary artery disease underwent radiofrequency catheter ablation of 42 VTs that had a mean cycle length of 486 +/- 78 msec. The only criterion used to select target sites for ablation was concealed entrainment, which was present at 92 sites. Thirty-five of the 42 VTs (83%) were successfully ablated. A discrete systolic potential was recorded during 7 of the 42 VTs (17%). In all cases, the interval between the discrete systolic potential and the next QRS complex was equal to the stimulus-QRS interval during concealed entrainment. At all seven sites where a discrete systolic potential was recorded, delivery of radiofrequency energy resulted in successful ablation of the VT. CONCLUSION: Discrete systolic potentials may be present in patients with coronary artery disease in approximately 17% of VTs in which there is concealed entrainment. If the interval between the discrete systolic potential and the next QRS complex matches the stimulus-QRS interval during concealed entrainment, delivery of radiofrequency energy is likely to result in successful ablation of the VT.     

Left Ventricular Outflow Tract Tachycardia Including Ventricular Tachycardia from the Aortic Cusps and Epicardial Ventricular Tachycardia

Idiopathic outflow tract ventricular tachycardia (VT) can arise from the right (RVOT) or left ventricular outflow tract (LVOT). The electrocardiographic (ECG) pattern of RVOT VT is typical in most patients, showing a monomorphic left bundle branch block (LBBB) QRS morphology with an inferior axis. Radiofrequency catheter ablation can be performed with a high success rate and provides a curative therapeutic approach. However, not all VTs with LBBB and inferior axis can be ablated from the RVOT. It has become apparent that LVOT VTs including VT originating from the aortic sinus of Valsalva or epicardium represent underrecognized VT entities which are also amenable to successful catheter ablation. Twelve-lead ECG criteria can contribute to distinguish between sites of VT origin.LVOT arrhythmias represent an increasingly recognized VT entity which can be safely and successfully treated by catheter ablation. Identification of VT origin using ECG criteria and differentiation of LVOT versus RVOT origin is essential in the careful planning of the ablation strategy.     

非接触球囊标测指导血流动力学不稳定性或非持续性室性心动过速的射频消融

目的探讨非接触球囊标测在指导血流动力学不稳定性或非持续性室性心动过速(室速)射频消融中的作用。方法17例室速患者,年龄50岁±9岁,经心室刺激诱发血流动力学不稳定性或非持续性室速后,使用非接触标测系统ENSITE3000标测室速的出口和(或)慢传导区,然后使用温控大头导管在室速出口作环形消融或横跨慢传导区进行线性消融。结果17例患者共诱发18次室速,周长为336MS±58MS。15例患者可确定室速的出口,为QRS波前10MS±16MS;其中5例是心肌梗死后室速,9例为右室流出道室速。5例心肌梗死后室速均可确定舒张期慢传导区,最早的心内膜舒张期电活动在QRS波前60·1MS±42·6MS。3例非持续性室速均可确定最早的心室激动点。18次室速中15次消融成功,1例没有进行消融,2例消融失败。结论非接触球囊心内膜标测能成功指导血流动力学不稳定性或非持续性室速的射频消融。     

Preferential conduction across the ventricular outflow septum in ventricular arrhythmias originating from the aortic sinus cusp.

OBJECTIVES: The purpose of this study was to examine the relationship between the origin and breakout site of idiopathic ventricular tachycardia (VT) or premature ventricular contractions (PVCs) originating from the myocardium around the ventricular outflow tract. BACKGROUND: The myocardial network around the ventricular outflow tract is not well known. METHODS: We studied 70 patients with idiopathic VT (n = 23) or PVCs (n = 47) with a left bundle branch block and inferior QRS axis morphology. Electroanatomical mapping was performed in both the right ventricular outflow tract (RVOT) and aortic sinus cusp (ASC) during VT or PVCs. RESULTS: The earliest ventricular activation (EVA) was recorded in the RVOT in 55 patients (group R) and in the ASC in 15 (group A). In all group R patients, the closest pace map and successful ablation were achieved at the EVA site. Although a successful ablation was achieved at the EVA site in all group A patients, the closest pace map was obtained at the EVA site in 8 and RVOT in 7 (with an excellent pace map in 4). The stimulus to QRS interval was 0 ms during pacing from the RVOT and 36 +/- 8 ms from the ASC. The distance between the EVA and perfect pace map sites in those 4 patients was 11.9 +/- 3.0 mm. CONCLUSIONS: Ventricular arrhythmias originating from the ASC often show preferential conduction to the RVOT, which may render pace mapping or some algorithms using the electrocardiographic characteristics less reliable. In some of those cases, an insulated myocardial fiber across the ventricular outflow septum may exist.     

Ventricular tachycardias arising from the aortic sinus of valsalva: an under-recognized variant of left outflow tract ventricular tachycardia

OBJECTIVES: To describe a normal heart left bundle branch block, inferior axis ventricular tachycardia (VT), that could not be ablated from the right or left ventricular outflow tracts. BACKGROUND: Whether these VTs are epicardial and can be identified by a specific electrocardiographic pattern is unclear. METHODS: Twelve patients with normal heart left bundle branch block, inferior axis VT and previously failed ablation were included in this study. Together with mapping in the right and left ventricular outflow tracts, we obtained percutaneous epicardial mapping in the first five patients and performed aortic sinus of Valsalva mapping in all patients. RESULTS: No adequate pace mapping was observed in the right and left ventricular outflow tracts. Earliest ventricular activation was noted in the epicardium and the aortic cusps. All patients were successfully ablated from the aortic sinuses of Valsalva (95% CI 0% to 18%). The electrocardiographic pattern associated with this VT was left bundle branch block, inferior axis and early precordial transition with Rs or R in V2 or V3. Ventricular tachycardia from the left sinus had rS pattern in lead I, and VT from the noncoronary sinus had a notched R wave in lead I. None of the patients had complications and all remained arrhythmia-free at a mean follow-up of 8 +/- 2.6 months. CONCLUSIONS: Normal heart VT with left bundle branch block, inferior axis and early precordial transition can be ablated in the majority of patients from either the left or the noncoronary aortic sinus of Valsalva.     

起源于主动脉窦频发室性期前收缩的心电生理特征及射频消融治疗

目的报道11例起源于主动脉窦的频发室性期前收缩（premature ventricular contraction,PVC）患者的心电生理特征、射频消融（radiofrequency catheter ablation,RFCA）方法及疗效。方法分析患者术前体表心电图和动态心电图PVC的特点,测量V1或V2导联r波时限和振幅,计算r波与QRS波时限的比值及r波于S波振幅的比值。术中行主动脉窦内激动标测和起搏标测确定PVC起源部位,并行冠状动脉造影辅助定位后行RFCA。结果11例均有频发PVC,5例有反复短阵室性心动过速。下壁导联QRS波呈R形且高大直立,V1导联呈rS型,胸前导联多移行于V3以前,V6导联多呈Rs型或无S波。V1导联r波时限（84.6±9.8）ms,占QRS波时限的50%以上;r/S振幅比值0.72±0.31。有效消融靶点局部电图V波较体表心电图的QRS波明显提前（35.6±8.9）ms,有效靶点放电2～8 s见PVC减少至消失。结论起源于主动脉窦的PVC其下壁导联QRS波呈R形且高大直立,V1或V2导联r波时限宽（〉50%同导联QRS波）,r波振幅高（〉30%同导联S波）;主动脉窦内PVC的射频消融治疗是安全、有效的。     

Bundle branch reentrant tachycardia in patients with apparent normal His-Purkinje conduction: the role of functional conduction impairment

INTRODUCTION: His-Purkinje conduction delay, manifested by bundle branch block QRS complex configuration or by HV interval prolongation, is considered an essential condition for maintenance of bundle branch reentrant tachycardia (BBRT). METHODS AND RESULTS: Of 178 patients with different types of ventricular tachycardia (VT), 13 were found to have BBRT as the underlying electrophysiologic mechanism. Of these 13 patients (9 men and 4 women; mean age 64 +/- 13 years), 6 had an HV interval < or = 55 msec (group A), and 7 had a prolonged HV interval (> 55 msec; group B) during sinus rhythm (SR). PR interval (169 +/- 32 vs 339 +/- 138 msec, P = 0.01) and QRS duration (116 +/- 17 vs 167 +/- 29 msec, P = 0.003) during SR were significantly shorter in group A than in group B. In group A, the HV interval was significantly longer during VT than during SR (73 +/- 18 vs 47 +/- 7 msec, P = 0.007). There were more patients with functional His-Purkinje block (split His potentials, a jump of HV interval induced by programmed atrial stimulation or burst pacing) or phase 3 block in group A than group B (6/6 patients vs 0/7 patients, P < 0.001). Successful ablation of the right bundle branch was performed in all 13 patients without deteriorating AV block. Two patients died in each group, and VTs (other than BBRT) or ventricular fibrillation were documented by ICD electrogram storages in 4 patients during follow-up of 27 +/- 17 months. CONCLUSION: A prolonged HV interval during SR is not a prerequisite for BBRT. Functional His-Purkinje system abnormalities appear to be the electrophysiologic substrate for this specific type of BBRT.     

Relative Timing of Isolated Potentials During Postinfarction Ventricular Tachycardia and Sinus Rhythm

BACKGROUND: In postinfarction patients, isolated potentials separated by an isoelectric segment from the ventricular electrogram indicate areas of block. Isolated potentials can be recorded during both sinus rhythm and ventricular tachycardia (VT). In an attempt to differentiate bystander pathways from critical sites within a reentry circuit, we compared the relative timing of isolated potentials during VT and sinus rhythm. METHODS: In 19 patients (mean age 68 +/- 6 years) with postinfarction VT who were referred for VT ablation, mapping was performed in the presence and absence of VT. Forty-three sites at which there was concealed entrainment during 35 VT's (mean cycle length 469 +/- 74 ms) displayed an isolated potential separated from the main portion of the ventricular electrogram by an isoelectric segment of >/=30 msec in the presence and absence of VT. The interval between the ventricular electrogram and the isolated potential was measured during VT and baseline rhythm, and the absolute difference (DeltaIPI) was calculated. The DeltaIPI was significantly greater at effective ablation sites (119 +/- 69 ms) than at ineffective ablation sites (30 +/- 28 ms, p < 0.001). The positive predictive value of a DeltaIPI > 85 ms for an effective ablation site was 100%. CONCLUSION: At sites of concealed entrainment, an absolute difference >85 ms between the isolated potential intervals during sinus rhythm and VT is highly specific for a critical area of the VT reentry circuit in post-infarction patients.     

Resetting of ventricular tachycardia with electrocardiographic fusion: incidence and significance

The incidence and significance of fusion of the QRS complex during resetting of sustained ventricular tachycardias (VTs) was determined in 53 VTs induced by programmed stimulation in 46 patients with prior myocardial infarction. All 53 VTs were reset with one or two extrastimuli delivered at the right ventricular apex (RVA); 29 (54.7%) demonstrated fusion of the VT QRS complex coincident with the extrastimulus resetting the VT. Activation time at the RVA during VT (measured from the onset of the VT QRS complex to the first rapid deflection of the RVA electrogram) was longer in VT reset with fusion compared with those without fusion (91 +/- 30 vs 33 +/- 32 msec; p less than .001). A right bundle branch block VT QRS morphology and a rightward and inferior axis were more common in VT reset with electrocardiographic (ECG) fusion. Additionally, the shortest return cycle following the extrastimulus resetting the VT was shorter in VT reset with ECG fusion compared with those without (327 +/- 66 vs 423 +/- 84 msec; p less than .001). Fusion of the endocardial electrogram recorded at the site of VT origin was noted in 11 of 15 VTs that were reset while a recording catheter was positioned at this site, including all eight VTs with evidence of surface ECG fusion and three of seven VTs without fusion. Seventeen VTs were reset from the right ventricular outflow tract as well as the RVA; eight demonstrated QRS fusion at both sites, five from the right ventricular outflow tract only, and four from neither site.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical application of an integrated 3-phase mapping technique for localization of the site of origin of idiopathic ventricular tachycardia

BACKGROUND: Radiofrequency (RF) catheter ablation provides curative treatment for idiopathic ventricular tachycardia (VT). METHODS AND RESULTS: Nineteen consecutive patients with an idiopathic VT underwent RF catheter ablation. An integrated 3-phase mapping approach was used, consisting of the successive application of online 62-lead body surface QRS integral mapping, directed regional paced body surface QRS integral mapping, and local activation sequence mapping. Mapping phase 1 was localization of the segment of VT origin by comparing the VT QRS integral map with a database of mean paced QRS integral maps. Mapping phase 2 was body surface pace mapping during sinus rhythm in the segment localized in phase 1 until the site at which the paced QRS integral map matched the VT QRS integral map was identified (ie, VT exit site). Mapping phase 3 was local activation sequence mapping at the circumscribed area identified in phase 2 to identify the site with the earliest local endocardial activation (ie, site of VT origin). This site became the ablation target. Ten VTs were ablated in the right ventricular outflow tract, 2 at the basal LV septum, and 7 at the midapical posterior left ventricle. A high long-term ablation success (mean follow-up duration, 14+/-9 months) was achieved in 17 of the 19 patients (89%) with a low number of RF pulses (mean, 3.3+/-2.2 pulses per patient). CONCLUSIONS: This prospective study shows that integrated 3-phase mapping for localization of the site of origin of idiopathic VT offers efficient and accurate localization of the target site for RF catheter ablation.     

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.     

Relationship between successful ablation sites and the scar border zone defined by substrate mapping for ventricular tachycardia post-myocardial infarction

INTRODUCTION: It is unknown if identification of scar border zones by electroanatomical mapping correlates with successful ablation sites determined from mapping during ventricular tachycardia (VT) post-myocardial infarction (MI). We sought to assess the relationship between successful ablation sites of hemodynamically stable post-MI VTs determined by mapping during VT with the scar border zone defined in sinus rhythm. METHODS AND RESULTS: Forty-six patients presenting with hemodynamically stable, mappable monomorphic VT post-MI and who had at least one such VT successfully ablated were prospectively included in the study. In each patient, VT was ablated by targeting regions during VT that exhibited early activation, +/- isolated mid-diastolic potentials, and concealed entrainment suggesting a critical isthmus site. Prior to ablation, a detailed sinus-rhythm CARTO voltage map of the left ventricle was obtained. A voltage <0.5 mV defined dense scar. Successful VT ablation sites were registered on the sinus voltage map to assess their relationship to the scar border zone. Of the 86 VTs, 68% were successfully ablated at sites in the endocardial border zone. The remaining VTs had ablation sites within the scar in (18%), in normal myocardium (4%), and on the epicardial surface (10%). There were no significant differences in VT recurrence amongst the different groups. CONCLUSION: Successful ablation sites of hemodynamically stable, monomorphic VTs post-MI are often located in the scar border zone as defined by substrate voltage mapping. However, in a sizable minority, ablation sites are located within endocardial scar, epicardially, and even in normal myocardium.     

Catheter ablation of haemodynamically unstable or non-sustained ventricular tachycardia

BACKGROUND: Ventricular tachycardia (VT) may be haemodynamically unstable or non-sustained, interfering with detailed activation mapping. Non-contact mapping permits beat-by-beat analysis of VT, projected upon a 3-dimensional reconstructed geometry of the cardiac chamber. Objective - The aim of the present study is to determine the utility of non-contact endocardial mapping to guide ablation of haemodynamically unstable VT or non-sustained VT. METHODS AND RESULTS: Eighteen VTs in 17 patients were induced (cycle length 336 +/- 58 ms) and mapped. Three patients were mapped during premature ventricular complexes (PVCs) because sustained VT could not be induced. Analysis of the archived non-contact activation maps was performed to identify the exit point and/or the diastolic pathway of theVT reentry circuit.The endocardial exit points (10 +/- 16 ms before QRS) were defined in 17/18 VTs (94%). A diastolic pathway was identified in 5/6 ischaemic VTs.The earliest activation sites were identified in all 3 patients with PVCs. Radiofrequency current was applied around the exit point or to create a line of block across the diastolic pathway. Catheter ablation was performed in 17/18 VTs, including 3 patients mapped using only PVCs. Ablation was successful in 16/18 VTs (89%) and in 1 5/17 patients (82%). Catheter ablation was not performed in one patient (peri-hisian VT) and was unsuccessful in one patient (mapped during PVCs). CONCLUSIONS: Non-contact endocardial mapping is useful to guide radiofrequency catheter ablation of untolerated or non-sustained VTs.     

Idiopathic ventricular arrhythmias arising from the pulmonary artery: Prevalence, characteristics, and topography of the arrhythmia origin

BACKGROUND: The characteristics of idiopathic ventricular tachycardias (VTs) or idiopathic premature ventricular contractions (PVCs) arising from the pulmonary artery (PA) have not been sufficiently clarified. OBJECTIVE: The purpose of this study was to clarify the prevalence, characteristics, and preferential sites of idiopathic VT/PVCs arising from the PA (PA-VT/PVCs). METHODS: Data obtained from 276 patients with idiopathic VT/PVCs who underwent radiofrequency (RF) catheter ablation were analyzed. RESULTS: Twelve VT/PVCs (4%) were PA-VT/PVCs, and their onset (34 +/- 14 years) was the youngest among all subgroups. Because those QRS morphologies were similar to VT/PVCs arising from the right ventricular outflow tract (RVOT-VT/PVC) and the earliest ventricular activation was from the RVOT, an initial ablation was performed in the RVOT in all patients. However, RF catheter ablation at the RVOT resulted in a QRS morphology change in all patients, so thereafter PA mapping and ablation was performed. A characteristic potential during sinus rhythm and/or the arrhythmia was recorded at the successful PA ablation site in all patients. A perfect or good pace map was obtained in 7 (70%) of 10 patients. The successful ablation site was the septal side of the PA close to the posterolateral attachment in 9 patients (75%) and the septal side close to the anterior attachment in the remaining 3 (25%). No PA-VT/PVCs recurred during follow-up of 27 +/- 13 months. CONCLUSION: PA-VT/PVCs should always be considered when the ECG suggests RVOT-VT/PVCs and RF catheter ablation in the RVOT results in both a failed ablation and a change in QRS morphology. PA-VT/PVCs often originate from the septal side of the PA.     

Catheter ablation of stable and unstable ventricular tachycardias in patients with arrhythmogenic right ventricular dysplasia

INTRODUCTION: A reentrant circuit within an area of abnormal myocardium is suspected as the origin of ventricular tachycardia (VT) in patients with arrhythmogenic right ventricular dysplasia (ARVD). OBJECTIVES: To examine the relationship between the reentrant circuits of VT and the abnormal electrograms in ARVD, and to assess the feasibility of a block line formation in the reentrant circuit isthmus utilizing electroanatomical mapping system (CARTO) guidance. METHODS AND RESULTS: An electrophysiological study and catheter ablation (CA) were performed in 17 ARVD patients (13 men, 47 +/- 17 year) using CARTO. Endocardial mapping during sinus rhythm demonstrated electrogram abnormalities extended from the tricuspid annulus (TA) or the right ventricular outflow tract in 16 of 17 patients. In 13 hemodynamically stable VTs, the reentrant circuits and critical slow conduction sites for the CA were investigated during VTs. The entire macro-reentrant pathway was identified in 6/13 stable VTs (figure-of-8 in 4, single loop in 2). In the remaining seven VTs, a focal activation pattern was found in four and an unidentifiable pattern in three. CA successfully abolished all the macro-reentrant and focal tachycardias, however, not effective in three unidentifiable VTs. In the 13 cases with unstable VT, the linear conduction block zone was produced between the sites with abnormal electrograms and the TA. Ultimately, 23/26 VTs (88%) became noninducible after the CA. During follow-up (26 +/- 15 months), 13/17 patients remained free from any VT episodes. CONCLUSIONS: CARTO is useful for characterizing the anatomical and electrophysiological substrates, and for identifying the optimal ablation sites for VT associated with ARVD.     

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

OBJECTIVES: We evaluated the safety and acute procedural efficacy of a combined electrophysiologic and anatomic approach to ablation of all inducible ventricular tachycardias (VT) during sinus rhythm using an irrigated radiofrequency (RF) ablation catheter. BACKGROUND: Ventricular tachycardia associated with chronic myocardial infarction (MI) is frequently hemodynamically intolerable and associated with multiple electrocardiographic morphologies. Because traditional mapping techniques are contingent on hemodynamic stability for adequate VT mapping, VT ablation therapy for many patients has been disappointing. METHODS: High-density electroanatomic mapping was performed during either sinus rhythm in 11 consecutive patients with a history of MI and ventricular arrhythmias. The RF ablation was performed using an irrigated-tip ablation catheter. All inducible VTs were targeted for catheter ablation during sinus rhythm. RESULTS: The RF ablation lesions were placed in a linear fashion traversing the border zones of infarcted and normal tissue (mean of 3.4 linear lesions/patient). With this strategy, the target VT was eliminated in 9 of 11 patients (82%). Furthermore, when targeting all inducible monomorphic VTs, complete procedural success was achieved in 7 of 11 patients (64%). During the follow-up period (mean 13.1 +/- 1.9 weeks), spontaneous VT was only noted in the two patients with no acute procedural benefit. CONCLUSIONS: By identifying potentially arrhythmogenic tissue during sinus rhythm, substrate mapping can guide the ablation of a majority of inducible VTs using an irrigated RF ablation catheter. This emerging therapeutic paradigm may be considered in the management of patients with multiple hemodynamically unstable monomorphic VTs.     

动态基质标测在致心律失常右室心肌病患者室性心动过速射频消融中的应用

目的　探讨应用非接触球囊导管标测系统行动态基质标测,指导对致心律失常右室心肌病(ARVC)患者室性心动过速(室速)消融的价值。方法　应用非接触球囊导管标测系统在窦律下对 3例ARVC室速患者行动态基质标测,在确定室速的最早激动点、出口部位和传导顺序后,寻找与室速相关的峡部并行线性消融。结果　3例患者存在 3种不同形态的基质,分别位于右室流出道、右室前壁和右室前侧壁。共诱发 5种室速,平均心动周期为(348±65)ms,其中 3种室速起源于基质或基质边缘, 2种室速的起源远离基质; 1种室速经基质传导。5种室速全部消融成功。平均随访 20个月,无心动过速发作。结论　应用非接触球囊导管标测系统确定异常电生理基质有助于理解ARVC室速的发生机制和制定消融策略,行室速相关峡部的线性消融可有效治疗室速。     

Electrocardiographic characteristics of repetitive monomorphic right ventricular tachycardia originating near the His-bundle

INTRODUCTION: Most idiopathic nonreentrant ventricular tachycardia (VT) and ventricular premature contractions (VPCs) arise from the right or left ventricular outflow tract (OT). However, some right ventricular (RV) VT/VPCs originate near the His-bundle region. The aim of this study was to investigate ECG characteristics of VT/VPCs originating near the His-bundle in comparison with right ventricular outflow tract (RVOT)-VT/VPCs. METHODS AND RESULTS: Ninety RV-VT/VPC patients underwent catheter mapping and radiofrequency ablation. ECG variables were compared between VT/VPCs originating from the RVOT and near the His-bundle. Ten patients had foci near the His-bundle (HIS group), with the His-bundle local ventricular electrogram preceding the QRS onset by 15-35 msec (mean: 22 msec) and His-bundle pacing produced a nearly identical ECG to clinical VT/VPCs. The HIS group R wave amplitude in the inferior leads (lead III: 1.0 +/- 0.6 mV) was significantly lower than that of the RVOT group (1.7 +/- 0.4 mV, P < 0.05). An R wave in aVL was present in 6 of 10 HIS group patients, while almost all RVOT group patients had a QS pattern in aVL. Lead I in HIS group exhibited significantly taller R wave amplitudes than RVOT group. HIS group QRS duration in the inferior leads was shorter than that of the RVOT group. Eight of 10 HIS group patients exhibited a QS pattern in lead V1 compared to 14 of 81 RVOT group patients. HIS group had larger R wave amplitudes in leads V5 and V6 than RVOT group. CONCLUSION: VT/VPCs originating near the His-bundle have distinctive ECG characteristics. Knowledge of the characteristic QRS morphology may facilitate catheter mapping and successful ablation.     

Resetting response patterns during sustained ventricular tachycardia: relationship to the excitable gap

We analyzed the resetting response (a noncompensatory pause after electrical stimulation) during 37 hemodynamically tolerated ventricular tachycardias (VTs) induced by programmed electrical stimulation in 32 patients with chronic coronary artery disease. The mean cycle length of VT was 369 +/- 59 msec. Single extrastimuli were delivered at the right ventricular apex during all 37 VTs, and double extrastimuli were delivered at the same site during 23 VTs. The resetting response pattern was considered increasing, decreasing, or flat if the return cycle increased, decreased, or remained constant in response to progressively shorter coupling intervals of the extrastimuli. Ten VTs had an increasing pattern and nine a flat pattern. In 11 VTs the pattern was mixed (flat at longer coupling intervals and increasing at shorter ones), and in the remaining seven the pattern could not be defined. No VT had a decreasing pattern. The mean duration of the resetting interval (range of coupling intervals resulting in resetting) was 66 +/- 45 msec, or 17% of the cycle length of VT. VT with a mixed pattern had longer resetting intervals than VT with an increasing pattern (102 +/- 34 vs 64 +/- 40 msec; p less than .035); however, cycle lengths of VT were similar (370 +/- 58 vs 386 +/- 86, p = NS). An excellent correlation was observed between the shortest return cycles in response to single and double extrastimuli (r = .99), with a mean difference of 5 msec. The cycle length of VT exceeded the return cycle (measured to the QRS onset) during 15 VTs (41%).(ABSTRACT TRUNCATED AT 250 WORDS)