Right ventricular outflow tract pacing: radiographic and electrocardiographic correlates of lead position

OBJECTIVE: To characterize the pacing site in an unselected series of patients undergoing right ventricular outflow tract (RVOT) lead placement and investigate the role of the electrocardiogram (ECG) in predicting implantation. BACKGROUND: Right ventricular apical pacing is associated with long-term adverse effects on left ventricular function, fuelling interest in alternative pacing sites, especially the RVOT. Previous studies have been conflicting, possibly due to poor definition of pacing site within the RVOT. METHODS: In 150 patients undergoing pacemaker implantation, implanters were asked to place the lead in the RVOT. Radiographs were performed in the antero-posterior (AP) and 40 degrees right and left anterior-oblique projections post procedure. Fifty-six had left lateral radiographs. Lead position was categorized using AP/RAO (right anterior oblique) to confirm RVOT placement and left anterior oblique to distinguish free wall from septum. A 12-lead ECG was performed during ventricular pacing. RESULTS: Leads were below the RVOT in 18. Of the remaining 132, the majority (94%) were in the inferior/low RVOT. Eighty-one out of 132 were septal and 51 free wall. Septal sites were associated with shorter QRS duration (134 ms vs 143 ms, P < 0.02). Free wall sites displayed more frequent notching of the inferior leads (P < 0.01). A negative deflection in lead I provided a positive predictive value of 90% for septal sites. In those with lateral radiographs, a posteriorly projected lead was 100% specific for septal placement. CONCLUSIONS: This study demonstrates the heterogeneity of lead placement within the RVOT. Septal and free wall sites display characteristic ECG patterns which may be used to aid placement. The left lateral radiograph is useful in confirming a true septal location.     

Importance of using standard rather than torso surface electrocardiographic leads for pacemapping at the right ventricular outflow tract

Although pacemapping has been used to localize the origin of ventricular tachycardia, the effect of changes in the position of ECG electrodes during ventricular pacing remains unknown. To clarify the relationship between the position of ECG limb electrodes and QRS configuration during pacemapping at the right ventricular outflow tract (RVOT), RVOT pacing was performed on 12 patients at eight pacing sites located in the anterior, septal, lateral, and posterior portions each in the high and low RVOT. Standard and torso ECGs were recorded simultaneously during each pacing protocol, and the QRS axis and amplitude were compared between the two ECGs. Differences between sites in the horizontal plane and in the longitudinal direction were also compared. The QRS axis on the torso ECG was significantly more rightward than that on the standard ECG at all eight pacing sites (72.1+/-17.4 vs 64.0+/-21.9 degrees). The magnitude of differences in the QRS axis and amplitude between the anterior and other sites at the same height was significantly greater in the standard ECG in all locations and in 7 of 18 comparable leads, respectively. The magnitude of differences between high and low sites was significantly greater in the standard ECG in three of four locations and in 5 of 12 comparable leads, respectively. In conclusion, the torso ECG is less sensitive to changes in pacing site at the RVOT than the standard ECG. The torso ECG is, therefore, not proper for pacemapping in attempts to ablate ventricular tachycardia arising from the RVOT.     

The role of Purkinje and pre-Purkinje potentials in the reentrant circuit of verapamil-sensitive idiopathic LV tachycardia

Although the mechanism of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) is usually reentry, the actual reentrant circuit is not clearly understood. This study examined the relationship between the Purkinje potential (PP) and a dull potential preceding PP (pre-PP) during ILVT to elucidate the roles of these potentials in the reentrant circuit of ILVT. Electrophysiological studies and radiofrequency catheter ablation were performed in ten patients (7 men, 3 women, mean age 29 years) who had an ILVT with a right bundle branch block configuration and left-axis deviation. Left ventricular endocardial mapping using an octapolar catheter and entrainment and resetting studies during VT was performed by pacing from the right ventricular outflow tract (RVOT) and each site of the left ventricular mapping catheter. PP and pre-PP were recorded simultaneously during VT in all patients. The earliest PP during VT was recorded at the inferoposterior septum, and PP was activated bidirectionally toward the proximal (basal) and distal (apical) sites along the left posterior fascicle. In contrast, pre-PP was recorded at sites slightly proximal to the earliest PP recording site, and was activated toward the earliest PP site. Pacing from RVOT confirmed manifest entrainment, and the stimulus to pre-PP interval was prolonged with a shorter pacing cycle length. Concealed entrainment was demonstrated by capture of the PPs of the left ventricular mapping catheter in six patients, and the postpacing interval at each PP site was equal to the tachycardia cycle length. The pre-PP was orthodromically activated from the proximal to the distal site during pacing. More rapid pacing also produced delay in activation from PP to pre-PP, indicating slow conduction in ILVT. Catheter ablation was performed at the pre-PP recording site during VT, and was successful in all patients. The reentrant circuit of ILVT could be constructed based on the pre-PP, PP, and slow conduction between the PP and pre-PP. Catheter ablation of ILVT was successful at the pre-PP recording site.     

The right ventricular outflow tract: a comparative study of septal, anterior wall, and free wall pacing

BACKGROUND: There is marked heterogeneity in right ventricular outflow tract (RVOT) pacemaker lead placement using conventional leads. As a result, we have sought to identify a reproducible way of placing a ventricular lead onto the RVOT septum. METHODS AND RESULTS: A major determinant is the shape of the stylet used to deliver the active-fixation lead. We compared stylet shapes and configurations in patients who initially had a ventricular lead placed onto the anterior or free wall of the RVOT and then had the lead repositioned onto the septum. All leads were loaded with a stylet fashioned with a distal primary curve to facilitate delivery of the lead to the pulmonary artery, then using a pullback technique the lead was retracted to the RVOT. All lead placements were confirmed by fluoroscopy and electrocardiography. Anterior or free wall placement was achieved by the stylet having either the standard curve or an added distal anterior angulation. In contrast, septal lead positioning was uniformly achieved by a distal posterior angulation of the curved stylet. This difference in tip shape was highly predictive for septal placement (P < 0.001). With septal pacing, a narrower QRS duration was noted, compared to anterior or free wall pacing (136 vs 155 ms, P < 0.001). All pacing parameters were within acceptable limits. CONCLUSION: Using appropriately shaped stylets, pacing leads can now be placed into specific positions within the RVOT and in particular septal pacing can be reliably and reproducibly achieved. This is an important step in the standardization of lead placement in the RVOT.     

The right ventricular outflow tract: the road to septal pacing

BACKGROUND: Pacing from the right ventricular apex is associated with long-term adverse effects on left ventricular function. This has fuelled interest in alternative pacing sites, especially the septal aspect of the right ventricular outflow tract (RVOT). However, it is a common perception that septal RVOT pacing is difficult to achieve. METHODS AND RESULTS: In this article, we will review the anatomy of the RVOT and discuss the importance of standard radiographic views and the 12-lead electrocardiogram in aiding lead placement. We will also describe a method utilizing a novel stylet shape, whereby a conventional active-fixation, stylet-driven lead can be easily and reliably deployed onto the RVOT septum.     

Reinitiation of ventricular macroreentry within the His-Purkinje system by back-up ventricular pacing - a mechanism of ventricular tachycardia storm

BACKGROUND: We describe immediate reinitiation of macroreentry ventricular tachycardia (VT) involving the His-Purkinje system by ventricular pacing from the electrode of an implantable cardioverter defibrillator (ICD) as a mechanism of VT storm refractory to ICD therapy. METHODS AND RESULTS: Repetitive reinitiation of bundle branch reentry tachycardia (BBRT), interfascicular tachycardia, or both VTs by ventricular pacing was identified in four ICD patients presenting with VT storm or incessant VT. All patients had a pre-existing prolonged HV interval (75 +/- 9 ms) and left bundle branch block (LBBB) or bifascicular block during sinus rhythm. The VTs included BBRT with LBBB in three patients and interfascicular tachycardia with right bundle branch block (RBBB) and left anterior or left posterior fascicular block in two patients. The paced beats from the ICD electrode exhibited a LBBB pattern of depolarization in two patients and a RBBB contour in V1 and V2 with left axis deviation in two patients. The QRS complex during pacing from the ICD electrode closely resembled that of the recurrent VT in all four patients suggesting that the pacing site of the ICD electrode was in proximity to the myocardial exit site of the bundle fascicle used for antegrade conduction during the reinitiated VT. Ventricular pacing from the ICD electrode after termination of the VT apparently encountered the retrograde refractoriness of this bundle fascicle and allowed immediate re-propagation of the wavefront orthodromically along the VT circuit. BBRT was eliminated by ablation of the right bundle branch. Successful ablation of the interfascicular tachycardias was achieved by targeting (1) an abnormal potential of the distal left posterior Purkinje network or (2) a diastolic potential during VT in the midinferior left ventricular (LV) septum. CONCLUSIONS: Repetitive reinitiation of BBRT and interfascicular tachycardia by ventricular pacing from the ICD electrode should be considered as a mechanism of VT storm refractory to ICD therapy in patients with a pre-existing conduction delay within the His-Purkinje system.     

Early Afterdepolarizations in a Patient with Idiopathic Monomorphic Right Ventricular Tachycardia

To identify the role of afterdepolarizations in the induction of idiopathic monomorphic right ventricular tachycardia (VT), monophasic action potentials (MAPs) were recorded in a patient with this type of VT. The VT had a left bundle branch block configuration and inferior axis, and originated in the right ventricular outflow tract (RVOT). MAPs were recorded with a contact electrode at the origin of the VT, as well as other ventricular sites. The VT was induced by the intravenous administration of isoproterenol and/or rapid ventricular pacing and was preceded by short-long-short sequences of RR intervals. Early afterdepolarizations (EADs) in MAPs were recorded at the origin of VT (RVOT), but not recorded at other ventricular sites. These data suggest that catecholamine sensitive triggered activity seems to be the mechanism of idiopathic monomorphic right VT and EADs can be recorded in association with the occurrence of this type of VT.     

Determinants of successful ablation of idiopathic ventricular tachycardias with left bundle branch block morphology from the right ventricular outflow tract

The aim of the study was to define the factors that may predict the outcomes of radiofrequency ablation from the right ventricular outflow tract (RVOT) in patients with idiopathic VT with a QRS morphology of LBBB. Endocardial mapping and RF ablation from the RVOT were performed in 35 patients (14 men, mean age 41 +/- 14 years), and VT was successfully ablated in 30 patients. There was no significant difference with regard to clinical characteristics and electrophysiological findings between patients with successful and failed ablation. The VTs with successful ablation showed an rS (n = 16) or QS (n = 14) pattern in lead V1, and all five VTs with failed ablation showed an rS pattern in lead V1. Although the absence of an R wave in lead V1 did not differ between patients with successful and failed ablation (P = 0.13), the absence of an R wave in lead V1 predicted VT successfully ablated from the RVOT (positive predictive value 100%; negative predictive value 24%). The VTs with successful ablation had a median precordial transitional zone at lead V4 (range V3-V6), whereas all five VTs with failed ablation had precordial transition zones at lead V3 (P = 0.004). Furthermore, a presence of an R wave in lead V1 associated with a precordial transition zone at lead V3 predicted VT not successfully ablated from the RVOT (positive predictive value 100%; negative predictive value 100%). In conclusion, some VTs with LBBB and inferior or normal axis cannot be ablated from the RVOT. The presence of an R wave in lead V1 associated with a precordial transition zone at lead V3 suggest that some VTs may not arise from the RVOT.     

Successful epicardial catheter ablation of a septal ventricular tachycardia after myocardial infarction

A 55-year-old man underwent catheter ablation of ventricular tachycardia (VT) after anterior myocardial infarction. Although electrophysiological study suggested that the VT originated from the septum, biventricular endocardial irrigated radiofrequency ablation failed to interrupt the VT. Epicardial ablation at the site located halfway between the lesions in the right and left ventricles via a pericardial approach eliminated the VT, suggesting that the VT likely originated from the top of the septum. When VTs originating from the upper septum are refractory to endocardial ablation, epicardial mapping and ablation may be considered because only that site may be accessible with an epicardial approach.     

Right Ventricular Outflow Tract Septal Pacing: Long-Term Follow-Up of Ventricular Lead Performance

Background: The detrimental effects of right ventricular apical pacing on left ventricular function has driven interest in selective site pacing, predominantly on the right ventricular outflow tract (RVOT) septum. There is currently no information on long-term ventricular lead electrical performance from this site.
Methods: A total of 100 patients with ventricular lead placement on the RVOT septum undergoing pacemaker implantation for bradycardia indications were analyzed retrospectively. Lead positioning was confirmed with the use of fluoroscopy. Long-term (1 year) follow-up was obtained in 92 patients. Information on stimulation threshold, R-wave sensing, lead impedance, and lead complications were collected.
Results: Lead performance at the RVOT septal position was stable in the long term. Ventricular electrical parameters were acceptable with stable long-term stimulation thresholds, sensing, and impedance for all lead types. One-year results demonstrated mean stimulation threshold of 0.71 ± 0.25 V, mean R wave of 12.4 ± 6.05 mV, and mean impedance values of 520 ± 127 Ω. There were no cases of high pacing thresholds or inadequate sensing.
Conclusions: This study confirms satisfactory long-term performance with leads placed on the RVOT septum, comparable to traditional pacing sites. It is now time to undertake studies to examine the long-term hemodynamic effects of RVOT septal pacing.     

Electrocardiographic Identification of Mid-Septal Accessory Pathways in Close Proximity to the Atrioventricular Conduction System

In order to identify ECG characteristics of overt midseptal accessory pathways (APs) predictive of close proximity to the AV conduction system we analyzed data from patients who underwent successful RF catheter ablation of a mid-septal AP, Mean patient age was 31 ± 16 years, and 13 were male. The 40° right anterior oblique view was used to divide the mid-septal area into 3 zones: 1 (anteriorportion); 2 (intermediate); and 3 (posterior portion). The 12-lead ECG was analyzed with regard to delta wave polarity and R/S transition in the precordial leads. The findings from patients ablated at zone 3 were compared to those at zones 1 and 2. All patients had a positive delta wave in the leads I, II, aVL, and negative delta wave in the leads III and aVR. The R/S transition occurred in lead V₂ in 80% of patients. The delta wave in lead aVF was the only ECG characteristic that correlated with the AP ablation zone. Six of 8 patients ablated at zone 3 had a negative delta wave in lead aVF while 6 out of 7 patients ablated at zone 1 or 2 had a positive or isoelectric delta wave in lead aVF (P = 0.03). A positive or isoelectric delta wave in lead aVF identifies mid-septal AP in close proximity to the AV conduction system.     

十二导联心电图对左主干病变导致急性冠状动脉综合征的诊断价值

目的探讨十二导联心电图对左主干病变导致急性冠状动脉综合征（ACS）的诊断价值。方法37例ACS患者根据冠状动脉造影结果分为A组（左主干病变导致ACS组）17例和B组（左前降支近段病变导致ACS组）20例,2组患者胸痛发作时均行十二导联心电图检查,分析冠状动脉病变血管与相应心电图变化的关系。结果A组在Ⅱ、Ⅲ、aVF、V2、V3、V4、V5、V6导联上相应ST段压低的发生率高于B组（P〈0．05或P〈0．01）。A组ST段在aVR、V1导联抬高并aVF、V2、V4导联压低发生率高于B组（P〈0．05）。结论十二导联心电图上aVR、V1导联ST段抬高并aVF、V2、V4导联压低对ACS患者左主干病变有较好的阳性预测价值。     

Additional electrocardiographic leads in the ED chest pain patient: right ventricular and posterior leads

In the evaluation of the patient with chest pain, the 12-lead electro cardiogram is a less-than-(ECG) perfect indicator of acute myocardial infarction (AMI), particularly when used early in the course of the acute ischemic event; this relative insensitivity for AMI results from many different issues, including a less-than-optimal imaging of certain areas of the heart. It has been suggested that the sensitivity of the 12-lead ECG can be improved if 3 additional body surface leads are used in selected individuals. Acute posterior (PMI) and right ventricular myocardial infarctions are likely to be underdiagnosed, because the standard lead placement of the 12-lead ECG does not allow these areas to be assessed directly. Additional leads frequently used include leads V(8) and V(9), which image the posterior wall of the left ventricle, and lead V(4R), which reflects the status of the right ventricle. The standard ECG coupled with these additional leads constitutes the 15-lead ECG, the most frequently used additional lead ECG in clinical practice. The use of the additional leads might not only confirm the presence of AMI, but also provide a more accurate reflection of the true extent of myocardial damage.     

Alternation of QRS Morphology and Effect of Radiofrequency Ablation in Idiopathic Ventricular Tachycardia

We performed electrophysiological studies in 13 patients with idiopathic VT and attempted radiofrequency (RF) catheter ablation in 4 of them.Results: VT was induced by programmed stimulation in all patients and the mean cycle length was 363 ± 58 msec. In 8 of 13 patients (62%), alternation of either the cycle length and/or morphology of VT was observed. Transient entrainment was achieved in all patients by rapid pacing from the right ventricular outflow tract so reentry was considered the underlying mechanism of VT. The site of earliest activation (EAS) during VT was located at the apicoposterior portion of the left ventricular septum and used as the target site for RF catheter ablation. Spikelike presystolic activity was detected 20–40 msec prior to the large deflection of the local electrogram in four patients. VT was terminated by a few seconds of RF current in all four patients, but subsequently new VTs with a slightly different morphology were induced in three of them and re-mapping showed a shift of the EAS. After additional RF ablation at the new EAS, VT was no longer induced. No complication was noted and VT did not recur during a follow-up period for a mean of 9.3 ± 5.2 months.Conclusion: RF catheter ablation seems useful and safe for idiopathic VT. The alternation of QRS morphology and the findings at the time of catheter ablation suggest that an alternative pathway or multiple exits may be present in some patients with idiopathic VT, because the change in VT morphology was associated with a shift of the EAS.     

Right Ventricular Septal Pacing: The Success of Stylet-Driven Active-Fixation Leads

Background: The detrimental effects of right ventricular (RV) apical pacing on left ventricular function has driven interest in alternative pacing sites and in particular the mid RV septum and RV outflow tract (RVOT). RV septal lead positioning can be successfully achieved with a specifically shaped stylet and confirmed by the left anterior oblique (LAO) fluoroscopic projection. Such a projection is neither always used nor available during pacemaker implantation. The aim of this study was to evaluate how effective is the stylet-driven technique in septal lead placement guided only by posterior-anterior (PA) fluoroscopic view.
Methods: One hundred consecutive patients with an indication for single- or dual-chamber pacing were enrolled. RV septal lead positioning was attempted in the PA projection only and confirmed by the LAO projection at the end of the procedure.
Results: The RV lead position was septal in 90% of the patients. This included mid RV in 56 and RVOT in 34 patients. There were no significant differences in the mean stimulation threshold, R-wave sensing, and lead impedance between the two sites . In the RVOT, 97% (34/35) of leads were placed on the septum, whereas in the mid RV the value was 89% (56/63).
Conclusions: The study confirms that conventional active-fixation pacing leads can be successfully and safely deployed onto the RV septum using a purposely-shaped stylet guided only by the PA fluoroscopic projection. (PACE 2010; 49–53)     

右心室不同部位起搏对心脏结构和左心功能的影响

[目的]对比研究右心室不同部位起搏对患者心脏结构和左心功能的影响.[方法]90例Ⅲ度或高度房室传导阻滞患者, 随机分为三组, A组行右室流入道（RVIS）间隔部起搏,B组行右室流出道（RVOT）间隔部起搏,C组行右心室心尖部（RVA）起搏. 观察三组手术中情况,监测术中血流动力学变化及手术曝光时间,比较三组术后随访的起搏器工作情况,心电图QRS波宽度,左心功能及血浆中B型钠尿肽（BNP）的差异.[结果]术中监测血流动力学,A组及B组明显优于C组.术后随访观察,A组及B组心电图QRS波宽度明显窄于C组,A组及B组具有更好的心脏功能.[结论]右心室间隔部起搏无论右室流出道起搏还是右室流入道间隔部起搏都是安全,有效的,比右室心尖部起搏更有利于双心室电激动的同步性,且长期对心脏结构及心功能影响也较少.     

体表心电图V1和aVL/aVR导联对房室结折返性心动过速的诊断价值

目的探讨体表心电图V1联合aVL或aVR导联对房室结折返性心动过速(AVNRT)的诊断价值。方法143例窄QRS心动过速患者的体表心电图,含窦性心律和心动过速心电图。由两位未知心动过速类型的心电生理医师进行诊断,记录包括V1导联假r′波、aVL导联末端切迹、心动过速RP′间期≥100 ms等指标,心动过速类型由心内电生理检查确定。结果AVNRT患者年龄较大(P<0.01),女性较多(72.4% vs 50.0%,P<0.01)。aVL导联末端切迹对于诊断AVNRT具有较高敏感度（60.9%）和特异度（89.3%）,高于传统V1导联假r′和下壁导联假s波（P均小于0.05）;联合V1导联假r′和aVL导联末端切迹或aVR导联假r′波明显提高AVNRT诊断敏感度至78.2%和74.7%,而阳性预测值无明显降低。RP′间期≥100 ms诊断顺向型房室折返性心动过速(AVRT)具有较高敏感度和特异度(敏感度69.6%, 特异度87.4%),联合aVR导联ST段J点后80 ms下斜型抬高超过1.5 mV指标,明显提高AVRT诊断敏感度（89.2%）。结论体表心电图V1和aVL或aVR导联可提高AVNRT诊断价值。     

不同导联连接方式对冠心病诊断的影响

目的:比较常规心电图(ECG)、动态心电图(AECG)采用Einthoven-Wilson12导联系统(A系统)和Mason-Likar12导联系统(B系统)记录时ST-T的差异。评价ECG、AECG采用不同导联系统对冠心病诊断的特异性,敏感性、误诊率、漏诊率。方法:选择207例行冠脉造影术(CAG)者为研究对象,其中CAG阳性者107例,CAG阴性者100例。均接受ECG、AECG检查,并分别采用A系统和B系统描记,每例4种描记方式在10min内完成。结果:(1)在ECG检查中,CAG阳性者,B系统与A系统相比,Ⅲ、V1～3的J点(以JⅢ、V1～3表示,以后类推)下移,STⅢ、aVR、V1～6下移,STⅠ上抬,TV2.4～6振幅降低,TⅠ、Ⅱ振幅升高;CAG阴性者,B系统与A系统相比,JⅡ、Ⅲ、aVF、V1下移,JaVR上抬,STⅡ、Ⅲ、V1、V3～4下移,TaVR、V4～5振幅降低。TⅡ振幅升高(2)在AECG检查中,CAG阳性者,B系统与A系统相比,JⅠ、Ⅲ、V1、V4～6下移,JaVR、aVL上抬,STⅢ、V1～2、V4～6下移,STⅠ、aVL上抬,TⅢ、5～6振幅降低,TⅠ、aVL振幅升高。CAG阴性者,B系统与A系统相比,JⅡ、aVF、V2、V6下移,JaVR上抬。STV1～2、V5～6下移,TaVR、V1～6振幅降低,TⅡ、aVF振幅升高。差异均有统计学意义,P<0.05。(3)不论ECG或AECG检查,采用B系统诊断冠心病较A系统误诊率增加。ECG检查中,采用A系统时,冠心病的误诊率为35.00%,漏诊率为36.45%;采用B系统诊断冠心病时,误诊率为46.00%,漏诊率为32.71%。在AECG检查中,采用A系统诊断冠心病时,误诊率为35.00%,漏诊率为35.51%;采用B系统诊断冠心病时,误诊率为47.00%,漏诊率为33.65%。结论:B系统记录的ST-T可能造成下壁、前壁心肌缺血的假象,在AECG诊断心肌缺血时应慎重,以免误诊,必要时应行CAG检查。     

Right Ventricular Septal Pacing: A Comparative Study of Outflow Tract and Mid Ventricular Sites

Background: Prolonged right ventricle (RV) apical pacing is associated with left ventricle (LV) dysfunction due to dysynchronous ventricular activation and contraction. Alternative RV pacing sites with a narrower QRS compared to RV pacing might reflect a more physiological and synchronous LV activation. The purpose of this study was to compare the QRS morphology, duration, and suitability of RV outflow tract (RVOT) septal and mid‐RV septal pacing. Methods: Seventeen consecutive patients with indication for dual‐chamber pacing were enrolled in the study. Two standard 58‐cm active fixation leads were passed to the RV and positioned in the RVOT septum and mid‐RV septum using a commercially available septal stylet (model 4140, St. Jude Medical, St. Paul, MN, USA). QRS duration, morphology, and pacing parameters were compared at the two sites. The RV lead with less‐satisfactory electrical parameters was withdrawn and deployed in the right atrium. Results: Successful positioning of the pacing leads at the RVOT septum and mid‐RV septum was achieved in 15 patients (88.2%). There were no significant differences in the mean stimulation threshold, R‐wave sensing, and lead impedance between the two sites. The QRS duration in the RVOT septum was 151 ± 14 ms and in the mid‐RV septum 145 ± 13 ms (P = 0.150). Conclusions: This prospective observational study shows that septal pacing can be reliably achieved both in the RVOT and mid‐RV with active fixation leads using a specifically shaped stylet. There are no preferences in regard to acute lead performance or paced QRS duration with either position. (PACE 2010; 33:1169–1173)     

Diagnosis and treatment of idiopathic ventricular tachycardia

Idiopathic ventricular tachycardia in patients with an anatomically normal heart is a distinct entity whose management and prognosis differs from ventricular tachycardia associated with structural heart disease. The tachycardia's QRS morphology on surface electrocardiogram (ECG) predicts the site of origin and is commonly classified as right ventricular tachycardia or left ventricular tachycardia. The tachycardia is further characterized by clinical features such as repetitive monomorphic ventricular tachycardia (VT), paroxysmal sustained VT, or catecholamine dependent VT. The responsiveness of VT to adenosine or verapamil is useful in differentiating the mechanism, which may be reentry or triggered activity.Patients generally tolerate the tachycardia but may present with dizziness, syncope, or palpitations. Sudden cardiac death is rare in this patient population. Patient work-up should include 12-lead ECG, signal-averaged ECG, ambulatory ECG recording, stress testing, and tests to rule out structural heart disease such as echocardiography, cardiac angiography, endomyocardial biopsy, or magnetic resonance imaging. Treatment options include pharmacotherapy or catheter ablation. Although the prognosis of these patients remains excellent, they should continue to have periodic cardiac follow-up to rule out latent progressive heart disease such as arrhythmogenic right ventricular dysplasia or cardiomyopathy or other forms of cardiomyopathies.