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.     

Ventricular tachycardias mimicking those arising from the right ventricular outflow tract

INTRODUCTION: Ablation of ventricular tachycardia (VT) arising from the right ventricular outflow tract (RVOT) has proven highly successful, yet VTs with similar ECG features may originate outside the RVOT. METHODS AND RESULTS: We reviewed the clinical, echocardiographic, and ECG findings of 29 consecutive patients referred for ablation of monomorphic VT having a left bundle branch block pattern in lead V1 and tall monophasic R waves inferiorly. Nineteen patients (group A) had VTs ablated from the RVOT, and 10 patients (group B) had VTs that could not be ablated from the RVOT. The QRS morphology during VT or frequent ventricular premature complexes was the only variable that distinguished the two groups. During the target arrhythmia, ECGs of group B patients displayed earlier precordial transition zones (median V3 vs V5; P < 0.001), more rightward axes (90 +/- 4 vs 83 +/- 5; P = 0.002), taller R waves inferiorly (aVF: 1.9 +/- 1.0 vs 2.4 +/- 0.5; P = 0.020) and small R waves in lead V1 (10/10 vs 9/19; P = 0.011). Radiofrequency catheter ablation from the RVOT failed to eliminate VT in any group B patient, but ablation from the left ventricular outflow tract (LVOT) eliminated VT in 2 of 6 patients in whom left ventricular ablation was attempted. CONCLUSION: The absence of an R wave in lead V1 and a late precordial transition zone suggest an RVOT origin of VT, whereas an early precordial transition zone characterizes VTs that mimic an RVOT origin. The latter VTs occasionally can be ablated from the LVOT. Recognition of these ECG features may help the physician advise patients and direct one's approach to ablation.     

Autonomic and pharmacological responses of idiopathic ventricular tachycardia arising from the left ventricular outflow tract

Background: It is well recognized that the mechanism of idiopathic ventricular tachycardia (VT) arising from the right ventricular outflow tract (RVOT) is mostly due to cyclic AMP-mediated triggered activity. The mechanism of VT arising from the left ventricular outflow tract (LVOT) has not been well clarified whether it is the same as VT of RVOT.
Methods: We studied autonomic modulations and pharmacological interventions on VT/premature ventricular contractions (PVCs) from LVOT to explore its possible mechanism in six patients (age: 49 ± 14, three males). None of them had structural heart diseases.
Results: Isoproterenol application easily induced VT and/or PVCs from LVOT. Valsalva maneuvers suppressed isoproterenol-induced VT in two and PVCs in two, and carotid sinus massage (CSM) suppressed PVCs in one patient. Adenosine triphosphate inhibited both VT and PVCs in all six patients. Propranolol, lidocaine, and procainamide eliminated VT/PVCs in four, three, and four patients, respectively. Verapamil terminated VT in one and PVCs in another one patient, but aggravated PVCs to VT in one patient.
Conclusion: The results suggest that the mechanism of VT from LVOT is mostly due to cAMP-mediated triggered activity as similar to that in VT from RVOT.     

Electrocardiographic pattern as a guide for management and radiofrequency ablation of idiopathic ventricular tachycardia

BACKGROUND: Idiopathic ventricular tachycardia (VT) often originates from the right ventricular outflow tract (RVOT), but foci deep to the endocardium, in the epicardium, or in the left ventricle are not uncommon. Although these extra-RVOT foci can be targeted with ablation, risks involved are higher and success rates lower. Simple electrocardiographic (ECG) criteria allowing (1) discrimination of RVOT foci from extra-RVOT foci and (2) assessment of the chance of success of a right heart ablation procedure are desirable. METHODS: Twenty-five consecutive patients referred for radiofrequency (RF) ablation of idiopathic VT or severely symptomatic idiopathic ventricular premature contractions were included. Localization of VT origin and success rates of VT ablation in the RVOT were analyzed according to the ECG pattern. RESULTS: The analysis of the R wave in V2 was the strongest single predictor of whether the VT had an RVOT or an extra-RVOT origin. An R wave amplitude < or =30% of the QRS amplitude designated the VT focus in the RVOT with positive and negative predictive values of 95 and 100%, respectively. Analysis of R wave duration in V2 had similar predictive values, whereas the R/S transition zone in precordial leads had slightly lower predictive values. Seventeen of 20 arrhythmias (85%) with an R wave amplitude < or =30% of the QRS amplitude in V2 could be successfully abolished by an exclusively right heart procedure. CONCLUSIONS: The analysis of ECG pattern makes it possible to guide the management of patients with idiopathic VT in predicting the arrhythmias that can be safely targeted with RF ablation from the RVOT with high success rates.     

特发性流出道室性期前收缩体表心电图207例分析

目的:分析特发性流出道室性期前收缩(室早,premature ventricular contractions,PVC)的体表心电图定位特征,进而指导射频导管消融。方法:回顾性分析连续207例接受射频消融治疗、术中经电生理检查和(或)心室造影,证实起源于左心室流出道(LVOT)或右室流出道(RVOT)室性心律失常(VAs)患者体表心电图特点,测量胸前导联R波、S波的振幅,分析胸前导联QRS波群R/S转换与起源部位的关系,R/S转换在V3导联时计算V2导联R/S振幅比值。结果:VAs时胸前导联R/S转换在V2或以前的VAs患者18(男8,女10)例,年龄23~87(44±17)岁,起源于LVOT 17例,特异性99%,敏感性68%。胸前导联R/S转换在V4或以后的共113(男43,女70)例,年龄4~73(42±14)岁,均起源于RVOT,特异性100%,敏感性62%。胸前导联R/S转换在V3的VAs患者76(男25,女51)例,年龄17~82(46±13)岁;起源于RVOT 68例,起源于LVOT 8例,V2导联R/S值比分别为0.32±0.17vs.0.64±0.21(P<0.05)。结论:流出道室早胸前导联R/S转换早于V2和晚于V4分别提示起源于LVOT和RVOT的特异性和敏感性均较高。转换在V3时,起源于LVOT的VAs胸前V2导联的R/S比值明显高于起源于RV-OT者。     

An Unusual Case Of Right Ventricular Outflow Tract Tachycardia

In this report, we describe an unusual case of right ventricular outflow tract (RVOT) tachycardia with episodes of repetitive monomorphic ventricular tachycardia (VT), paroxysmal sustained VT and incessant monomorphic VT of the same morphology. Diltiazem, adenosine, or metoprolol failed to interrupt these arrhythmias. However, administration of intravenous propafenone completely eliminated all ventricular ectopic activity. Electrophysiologic study performed off propafenone showed that the ventricular ectopic activity originated from a single locus at the anterior wall of the RVOT. Two radiofrequency applications at this site resulted in complete elimination of ventricular ectopic activity.     

Substrate in the interventricular septum for left ventricular and right ventricular outflow tract tachycardia: ablation from the right side of the septum

Simultaneous epicardial and endocardial mapping demonstrated that in a substantial number of ventricular tachycardias (VTs) endocardial, intramural, and epicardial structures are involved in the substrate of the reentrant circuits. Both right and left ventricular breakthrough has also been described during VT originating in the interventricular septum. We report the case of a patient with a nonischemic left ventricular aneurysm presenting with a left ventricular outflow tract (LVOT) tachycardia and a right ventricular outflow tract (RVOT) tachycardia. Mapping from the anterior interventricular vein and the endocardium of the RVOT revealed mid-diastolic potentials at the epicardium of the LVOT and the endocardium of RVOT, where the criteria of central isthmus sites could be demonstrated. Ablation targeting an isolated late potential during sinus rhythm in RVOT eliminated both the LVOT tachycardia and the RVOT tachycardia. In this patient with a nonischemic left ventricular aneurysm, the substrate of a LVOT tachycardia and RVOT tachycardia is described, and successful catheter ablation of the right and left ventricular tachycardia from the septal wall of RVOT is reported.     

S‐R difference in V1‐V2 is a novel criterion for differentiating the left from right ventricular outflow tract arrhythmias

Aim

The correct estimation of the VA origin as RVOT or LVOT results in reduced ablation duration reduced radiation exposure and decreased number of vascular access. In our study, we aimed to detect the predictive value of S‐R difference in V1‐V2 for differentiating the left from right ventricular outflow tract arrhythmias.

Methods

We included 123 patients with symptomatic frequent premature ventricular outflow tract contractions who underwent successful catheter ablation (70 male, 53 female; mean age 46.2 ± 13.9 years, 61 RVOT, 62 LVOT origins). S‐R difference in V1‐V2 was calculated with this formula on the 12‐lead surface ECG: (V1S + V2S) – (V1R + V2R). Conventional ablation was performed in 101 (82.1%) patients, CARTO electroanatomic mapping system was used in 22 (17.9%) patients.

Results

V1‐2 SRd was found to be significantly lower for LVOT origins than RVOT origins (p < .001). The cutoff value of V1‐2 SRd obtained by ROC curve analysis was 1.625 mV for prediction of RVOT origin (sensitivity: 95.1%, specificity: 85.5%, positive predictive value: 86.5%, negative predictive value: 94.5%). The area under the curve (AUC) was 0.929 (p < .001).

Conclusion

S‐R difference in V1‐V2 is a novel and simple electrocardiographic criterion for accurately differentiating RVOT from LVOT sites of ventricular arrhythmia origins. The use of this simple ECG measurement could improve the accuracy of OTVA localization, could be beneficial for decreasing ablation duration and radiation exposure. Further studies with larger patient population are needed to verify the results of this study.

     

Electrocardiographic patterns of superior right ventricular outflow tract tachycardias: distinguishing septal and free-wall sites of origin

INTRODUCTION: The superior right ventricular outflow tract (RVOT) septum and free wall are common locations of origin for outflow tract ventricular tachycardias (VT). We hypothesized that (1) unique ECG morphologies of pace maps from septal and free-wall sites in the superior RVOT could be identified using magnetic electroanatomic mapping for accurate anatomical localization; and (2) this ECG information could help facilitate pace mapping and accurate VT localization. METHODS AND RESULTS: In 14 patients with structurally normal hearts who were undergoing ablation for outflow tract VT, a detailed magnetic electroanatomic map of RVOT was constructed in sinus rhythm, then pace mapping was performed from anterior, mid, and posterior sites along the septum and free wall of the superior RVOT. Pace maps were analyzed for ECG morphologies in limb leads and transition patterns in precordial leads. Monophasic R waves in inferior leads for septal sites were taller (1.7 +/- 0.4 mV vs 1.1 +/- 0.3 mV; P < 0.01) and narrower (158 +/- 21 msec vs 168 +/- 15 msec; P < 0.01) compared with free-wall sites; lacked "notching" (28.6% vs 95.2%; P < 0.05); and showed early precordial transition (by lead V4; 78.6% vs 4.8%; P < 0.05). A positive R wave in lead I also distinguished posterior from anterior septal and free-wall sites. Based on QRS morphology in limb leads and precordial transition pattern (early vs late), in a retrospective analysis, a blinded reviewer was able to accurately localize the site of origin of clinical arrhythmia (the successful ablation site on the magnetic electroanatomic map) in 25 of 28 patients (90%) with superior RVOT VT. CONCLUSION: Pace maps in the superior RVOT region manifest site-dependent ECG morphologies that can help in differentiating free-wall from septal locations and posterior from anterior locations. Despite overlap in QRS amplitude and duration, in the majority of patients a combination of ECG features can serve as a useful template in predicting accurately the site of origin of clinical arrhythmias arising from this region.     

胸导联R／S波振幅转换及V2导联R波振幅比例比较在判断室性心律失常左右流出道起源中的价值

目的 探讨通过比较流出道室性心律失常（OTA）及窦性心律（SR）时胸导联R/ S波振幅转换及V2导联R波振幅比例变化,判断OTA起源于右室流出道（RVOT）或左室流出道（LVOT）的价值。方法 回顾性分析208例经射频导管消融治疗成功证实的起源于RVOT或LVOT的OTA患者的ECG特点。观察OTA时发生R/ S转换的胸前导联,发生在V3以前判定OTA起源于LVOT;R/ S转换发生在V3导联时,比较OTA及SR时V2导联R波振幅比例,如V2转换率大于1则判定OTA起源于LVOT;R/ S转换发生在V3以后时判定OTA起源于RVOT。统计各诊断方法的灵敏度、特异度。结果 208例患者中男性76例,年龄43. 6±13. 8岁。 OTA的成功射频消融靶点位于RVOT者181例,位于LVOT者27例。 OTA时ECG形态表现R/ S转换在V3以前的患者18例,起源于LVOT者17例。以OTA的R/ S转换早于V3即诊断OTA起源于LVOT为标准,其灵敏度为63. 0% ,特异度99. 5%。 OTA时ECG形态表现R/ S转换在V3以后的共112例,均起源于RVOT。以OTA的R/ S转换晚于V3即诊断OTA起源于RVOT为标准,其灵敏度为61. 9%,特异度100%。 OTA的ECG形态表现R/ S转换在V3的患者78例,起源于RVOT 68例。起源于LVOT的V2转换率大于起源于RVOT的V2转换率（1. 32±0. 26 vs 0. 52±0. 20,P〈0. 05）。 OTA的R/ S转换在V3时,如果以V2转换率≥1即诊断OTA起源于LVOT为标准,其灵敏度80. 0% ,特异度94. 2%。OTA时R/ S转换在V3而SR时R/ S转换在V2的患者共22例,均起源于RVOT,此方法灵敏度32. 4%,特异度100%。结论 OTA的胸前导联R/ S转换早于V3和晚于V3作为诊断OTA起源于LVOT和RVOT的标准具有很高的特异度和灵敏度。 OTA时R/ S转换在V3时,比较OTA及SR时V2导联R波振幅比例,如V2转换率大于1则判定OTA起源于LVOT具有较高的实用价值。     

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.     

Radiofrequency Ablation Guided by Mechanical Termination of Idiopathic Ventricular Arrhythmias Originating in the Right Ventricular Outflow Tract

Mapping of Idiopathic Ventricular Arrhythmias. Background: Termination of ventricular tachycardia (VT) by mechanical pressure has been described for fascicular and postinfarction VT. Mechanical interruption of idiopathic ventricular arrhythmias (VT/premature ventricular complexes [PVCs]) arising in the right ventricular outflow tract (RVOT) has not been described in systematic fashion. Methods: Eighteen consecutive patients (13 females, age 49 ± 13 years, ejection fraction 0.55 ± 0.12) underwent mapping and ablation of RVOT VT or PVCs. In 7 patients, 9 distinct VTs (mean cycle length 440 ± 127 ms), and in 11 patients, 11 distinct PVCs originating in the RVOT were targeted. Mechanical termination was considered present if a reproducibly inducible VT was no longer inducible or if frequent PVCs suddenly ceased with the mapping catheter at a particular location. Endocardial activation time, electrogram characteristics, and pace‐mapping morphology were assessed at this location. Radiofrequency energy was delivered if mechanical termination was observed. Results: All targeted arrhythmias were successfully ablated. In 7 of 18 patients (39%), catheter manipulation terminated the arrhythmia with the mapping catheter located at a particular site. Local endocardial activation time was earlier at sites of mechanical termination (?31 ± 7 ms) compared with effective sites without termination (?25 ± 3 ms, P = 0.04). The 10‐ms isochronal area was smaller in patients with mechanical interruption (0.35 ± 0.2 cm²) than in patients without mechanical termination (1.33 ± 0.9 cm², P = 0.01). At all sites susceptible to mechanical trauma, the pace map displayed a match with the targeted VT/PVC. All sites where mechanical termination of VT or PVCs occurred were effective ablation sites. Conclusions: Mechanical suppression at the site of origin of idiopathic RVOT arrhythmias frequently occurs during the mapping procedure and is a reliable indicator of effective ablation sites. Mechanical termination of RVOT arrhythmias may be indicative of a more localized arrhythmogenic substrate. (J Cardiovasc Electrophysiol, Vol. 21, pp. 42–46, January 2010)     

Left ventricular outflow tract tachycardia originating from the right coronary cusp: identification of location of origin by endocardial noncontact activation mapping from the right ventricular outflow tract

Idiopathic left ventricular outflow tract (LVOT) tachycardia has been shown to originate from a supravalvular site in some patients. Considerable attention recently has focused on identifying this variant of LVOT tachycardia on 12-lead ECG. We report the case of 15-year-old boy in whom a noncontact three-dimensional mapping electrode deployed in the right ventricular outflow tract (RVOT) assisted in identifying a supravalvular LVOT tachycardia. Observation of two early breakthrough sites in the RVOT and right ventricular septum suggested a right aortic cusp origin of the tachycardia. Pace mapping in the right aortic cusp identified a successful ablation site.     

Dynamic Changes of QRS Morphology of Premature Ventricular Contractions During Ablation in the Right Ventricular Outflow Tract: A Case Report

Electrocardiographic characteristics can be useful in differentiating between right ventricular outflow tract (RVOT) and aortic sinus cusp (ASC) ventricular arrhythmias. Ventricular arrhythmias originating from ASC, however, show preferential conduction to RVOT that may render the algorithms of electrocardiographic characteristics less reliable. Even though there are few reports describing ventricular arrhythmias with ASC origins and endocardial breakout sites of RVOT, progressive dynamic changes in QRS morphology of the ventricular arrhythmias during ablation obtained were rare.This case report describes a patient with symptomatic premature ventricular contractions of left ASC origin presenting an electrocardiogram (ECG) characteristic of right ventricular outflow tract before ablation. Pacing at right ventricular outflow tract reproduced an excellent pace map. When radiofrequency catheter ablation was applied to the right ventricular outflow tract, the QRS morphology of premature ventricular contractions progressively changed from ECG characteristics of right ventricular outflow tract origin to ECG characteristics of left ASC origin.Successful radiofrequency catheter ablation was achieved at the site of the earliest ventricular activation in the left ASC. The distance between the successful ablation site of the left ASC and the site with an excellent pace map of the RVOT was 20 mm.The findings could be strong evidence for a preferential conduction via the myocardial fibers from the ASC origin to the breakout site in the right ventricular outflow tract. This case demonstrates that ventricular arrhythmias with a single origin and exit shift may exhibit QRS morphology changes.     

Ventricular tachycardia of right ventricular outflow tract origin during the perioperative period: A case report

Rationale:Idiopathic ventricular tachycardia (VT) occurs in individuals without structural abnormalities in the heart, accounts for approximately 10% of total VTs. Furthermore, approximately 70% of idiopathic VTs originate from Right ventricular outflow tract (RVOT). However, among perioperative arrhythmias, incidence of VT after surgery is extremely rare and most arrhythmias are atrial origin.Patient concerns:A 69-year-old man with permanent pacemaker underwent colon surgery.Diagnoses:Patient suffered from low blood pressure and dizziness, sweating at post anesthetic care unit (PACU) and heart rate (HR) increased suddenly to 200 beats/min with monomorphic VT after bolus ephedrine administration and continuous dopamine infusion.Interventions:Pacemaker interrogation followed by DC cardioversion was done.Outcomes:Patient''s vital signs became normal and symptoms are subsided.Lessons:RVOT VT can be caused by triggering activities, such as ephedrine, dopamine, and inadequate fluid management. These triggering activities are initiated by acceleration of HR from ventricles with infusion of catecholamine which lead monomorphic VT originating from RVOT.RVOT origin PVCs can be precipitated into monomorphic VT by administrating catecholamines such as ephedrine and dopamine even in patient with pacemaker. The mechanism of these VTs includes catecholamine induced acceleration of HR. Since RVOT PVCs can be recognize by 12 EKGs, we should be pay more attentions to the pre-operation EKG and be cautious using catecholamines.     

Human Model Simulating Right Ventricular Outflow Tract Tachycardia by High-Frequency Stimulation in the Left Pulmonary Artery: Autonomics and Idiopathic Ventricular Arrhythmias

Introduction: Frequent monomorphic premature ventricular contractions (PVC) and/or ventricular tachycardia (VT) in patients with structurally normal heart usually arise from the right ventricular outflow tract (RVOT). An animal model simulating RVOT tachycardia by high-frequency stimulation (HFS) of the sympathetic input to the proximal pulmonary artery (PA) has been previously described. The aim of this study was to similarly induce RVOT tachycardia in humans.
Methods: In 9 patients with no history of ventricular arrhythmias, a circumferential catheter was placed in the left, main, and proximal PA to contact the endovascular circumference of the PA. A 50-ms train of HFS (200 Hz/0.3 ms pulse duration), coupled to atrial pacing, was applied at each bipolar pair of the circumferential catheter. The coupling interval was adjusted so that the 50-ms train occurred during the ventricular refractory period.
Results: In 6 out of 9 patients, HFS in the left PA during dobutamine infusion induced monomorphic PVCs and/or VT with left bundle branch block (LBBB) morphology and inferior axis at an average stimulation level of 12.5 ± 2.7 V. HFS in the main PA and in the proximal PA did not induce any ventricular arrhythmias with the highest energy of 15 V in baseline state and during dobutamine infusion. HFS in the left PA was associated with hiccough in all patients.
Conclusion: Stimulation of the sympathetic input to the left PA during dobutamine infusion induces PVCs and/or VT exhibiting LBBB-morphology and inferior axis, closely simulating clinical RVOT tachycardia in humans.     

起源于左右心室流出道心动过速和早搏的射频导管消融治疗

目的 探讨射频导管消融（RFCA）治疗心室流出道特发性室性心动过速（室速）和室性早搏（室早）的临床效果、心电图及电生理特征。方法 58例患者中室速10例,室早48例。起源于右室流出道（RVOT）43例,左室流出道（LVOT）15例,其中起源于主动脉瓣上Valsalva左冠窦（LSV）12例。5例RVOT室速是在非接触标测系统Ensite3000指导下进行消融的。结果 （1）58例患者中55例成功,3例失败,9例复发。（2）其中1例患者术中出现急性心包压塞。（3）起源心室流出道的室速和室早具有典型的心电图特征,其中Ⅱ、Ⅲ、aVF导联单向R波是流出道室性心律失常的共同特点。（4）V1或V2导联的R波时限指数与R／S波幅指数可作为区别LSV与RVOT室速和室早的有效指标。结论 射频导管消融治疗心室流出道特发性室性心律失常是一种安全、有效的方法。非接触标测系统对于血流动力学不稳定的复杂性室性心律失常的标测与治疗具有重要的意义。     

Use of three-dimensional echocardiography for analysis of outflow obstruction in congenital heart disease

To evaluate the feasibility and accuracy of 3-dimensional (3D) echocardiography in analysis of left and right ventricular outflow tract (LVOT and RVOT) obstruction, 3D echocardiography was performed in 28 patients (age 4 months to 36 years) with outflow tract pathology. Type of lesion and relation to valves were assessed. Length and degree of obstruction were measured. Three-D data sets were adequate for reconstruction in 25 of 28 patients; 47 reconstructions were made. In 13 patients with LVOT obstruction, 3D echocardiography was used to study subvalvular details in 8, valvular in 13, and supravalvular in 1. Four of these 13 patients had complex subaortic obstruction. In 12 patients with RVOT lesions, 3D echocardiography was used to study subvalvular details in 11, valvular in 12, and supravalvular in 2. Three-dimensional reconstructions were suitable for analysis in 100% of subvalvular LVOT, 77% valvular LVOT, 100% supravalvular LVOT, 100% subvalvular RVOT, 50% valvular RVOT, and 50% supravalvular RVOT. Twenty patients underwent operation, and surgical findings served as morphologic control for thirty-four 3D reconstructions (LVOT 17, RVOT 17). Operative findings revealed an accuracy at subvalvular LVOT of 100%, valvular LVOT 90%, supravalvular LVOT 100%, subvalvular RVOT 100%, valvular RVOT 100%, and supravalvular RVOT 100%. Quantitative measurements could adequately be performed. Three-D echocardiography is feasible and accurate for analyzing both outflow tracts of the heart. Particularly, generation of nonconventional horizontal cross sections allows a good definition of extension and severity of lesions.     

Hypertrophic Cardiomyopathy with Right Ventricular Outflow Tract and Left Ventricular Intracavitary Obstruction

Obstruction of the right ventricular outflow tract (RVOT) is a rare finding in hypertrophic cardiomyopathy (HCM) patients unlike left ventricular outflow tract (LVOT) obstruction. Although there are guidelines that aid in clinical decision making in patients with LVOT obstruction, there are none addressing RVOT obstruction. As RVOT obstruction may pose serious clinical implications similar to LVOT obstruction, appropriate medical and surgical management is very important. A unique phenotype of HCM with RVOT obstruction in conjunction with left ventricle (LV) intracavitary obstruction is discussed.     

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.