Idiopathic monomorphic ventricular tachycardia: clinical outcome, electrophysiologic characteristics and long-term results of catheter ablation

Electrical and Structural Insights into Right Ventricular Outflow Tract Arrhythmogenesis

The right ventricular outflow tract (RVOT) is the major origin of ventricular arrhythmias, including premature ventricular contractions, idiopathic ventricular arrhythmias, Brugada syndrome, torsade de pointes, long QT syndrome, and arrhythmogenic right ventricular cardiomyopathy. The RVOT has distinct developmental origins and cellular characteristics and a complex myocardial architecture with high shear wall stress, which may lead to its high vulnerability to arrhythmogenesis. RVOT myocytes are vulnerable to intracellular sodium and calcium overload due to calcium handling protein modulation, enhanced CaMKII activity, ryanodine receptor phosphorylation, and a higher cAMP level activated by predisposing factors or pathological conditions. A reduction in Cx43 and Scn5a expression may lead to electrical uncoupling in RVOT. The purpose of this review is to update the current understanding of the cellular and molecular mechanisms of RVOT arrhythmogenesis.

Advanced glycation end products modulate electrophysiological remodeling of right ventricular outflow tract cardiomyocytes: A novel target for diabetes-related ventricular arrhythmogenesis

Diabetes mellitus is associated with cardiovascular disease and cardiac arrhythmia. Accumulation of advanced glycation end products closely correlates with cardiovascular complications through mitochondrial dysfunction or oxidative stress and evoke proliferative, inflammatory, and fibrotic reactions, which might impair cardiac electrophysiological characteristics and increase the incidence of cardiac arrhythmia. This study examined the mechanisms how advanced glycation end products may contribute to arrhythmogenesis of right ventricular outflow tract-a unique arrhythmogenic substrate. A whole-cell patch clamp, conventional electrophysiological study, fluorescence imaging, Western blot, and confocal microscope were used to study the electrical activity, and Ca2+ homeostasis or signaling in isolated right ventricular outflow tract myocytes with and without advanced glycation end products (100 μg/ml). The advanced glycation end products treated right ventricular outflow tract myocytes had a similar action potential duration as the controls, but exhibited a lower L-type Ca2+ current, higher late sodium current and transient outward current. Moreover, the advanced glycation end products treated right ventricular outflow tract myocytes had more intracellular Na+ , reverse mode Na+ -Ca2+ exchanger currents, intracellular and mitochondrial reactive oxygen species, and less intracellular Ca2+ transient and sarcoplasmic reticulum Ca2+ content with upregulated calcium homeostasis proteins and advanced glycation end products related signaling pathway proteins. In conclusions, advanced glycation end products modulate right ventricular outflow tract electrophysiological characteristics with larger late sodium current, intracellular Na+ , reverse mode Na+ -Ca2+ exchanger currents, and disturbed Ca2+ homeostasis through increased oxidative stress mediated by the activation of the advanced glycation end products signaling pathway.

Predictors and Long-Term Outcome of Ablation of Discrete Pre-potentials in Patients With Idiopathic Ventricular Arrhythmias Originating From the Aortic Sinuses of Valsalva

Background: The predictability and long-term outcome of the discrete pre-potential (DPP) of idiopathic ventricular arrhythmias (VAs) arising from the aortic sinuses of Valsalva (ASV) have not been fully identified.

Methods: Of 687 consecutive patients undergoing ablation of outflow tract VAs, there were 105 (15.3%) patients with VAs originating from the ASV region who were included. Detailed mapping was performed within the ASV in all patients. Electrocardiographic, electrophysiological parameters, and long-term success rate were compared between patients with and without the DPPs.

Results: A DPP was recorded in 67 of 105 (63.8%) patients, including 38 left sinus of Valsalva (LSV)-VAs (38/105, 36.2%) and 29 right sinus of Valsalva (RSV)-VAs (29/105, 27.6%). The patients with DPPs had wider QRS duration (152 ± 17 vs. 145 ± 14 ms, p < 0.001). The average of earliest activation time was significantly earlier in patients with DPPs (−38.6 ± 8.5 vs. −27.7 ± 5.7 ms, p < 0.001). Mean time from the first lesion to elimination of VAs was shorter in patients with DPPs (2.3 ± 2.1 s vs. 4.9 ± 1.0 s, p < 0.001). A stepwise logistic multivariable analysis identified only younger age as a significant predictor of DPP (age ≤ 35.5 years predicted DPP with 92.9% positive predictive value). During a follow-up duration of 42.5 ± 22.3 months, 63 (94.0%) patients with DPPs and 30 (78.9%) patients without DPPs remained free of recurrent VAs (p = 0.027).

Conclusion: Discrete pre-potentials were observed in 63.8% of patients with VAs arising from the ASV. Ablation in patients with DPPs was associated with higher long-term success. DPPs were seen more commonly in younger (age ≤ 35.5 years) patients.

Calcium dysregulation increases right ventricular outflow tract arrhythmogenesis in rabbit model of chronic kidney disease

Chronic kidney disease (CKD) increases the risk of arrhythmia. The right ventricular outflow tract (RVOT) is a crucial site of ventricular tachycardia (VT) origination. We hypothesize that CKD increases RVOT arrhythmogenesis through its effects on calcium dysregulation. We analysed measurements obtained using conventional microelectrodes, patch clamp, confocal microscopy, western blotting, immunohistochemical examination and lipid peroxidation for both control and CKD (induced by 150 mg/kg neomycin and 500 mg/kg cefazolin daily) rabbit RVOT tissues or cardiomyocytes. The RVOT of CKD rabbits exhibited a short action potential duration, high incidence of tachypacing (20 Hz)‐induced sustained VT, and long duration of isoproterenol and tachypacing‐induced sustained and non‐sustained VT. Tachypacing‐induced sustained and non‐sustained VT in isoproterenol‐treated CKD RVOT tissues were attenuated by KB‐R7943 and partially inhibited by KN93 and H89. The CKD RVOT myocytes had high levels of phosphorylated CaMKII and PKA, and an increased expression of tyrosine hydroxylase‐positive neural density. The CKD RVOT myocytes exhibited large levels of I_to, I_Kr, NCX and L‐type calcium currents, calcium leak and malondialdehyde but low sodium current, SERCA2a activity and SR calcium content. The RVOT in CKD with oxidative stress and autonomic neuron hyperactivity exhibited calcium handling abnormalities, which contributed to the induction of VT.

Epicardial adipose tissue modulates arrhythmogenesis in right ventricle outflow tract cardiomyocytes

AIMS

Ventricular arrhythmia (VA) frequently occurs in fatty infiltrative cardiomyopathy or epicardial adipose tissue (EAT) abundant hearts. Right ventricular outflow tract (RVOT), commonly covered with EAT, is vital for VA genesis. This study explored whether EAT contributes to RVOT arrhythmogenesis.

METHODS AND RESULTS

Conventional microelectrodes and whole-cell patch clamp were used to record electrical activity and ionic currents in rabbit RVOT tissue preparation or isolated single cardiomyocytes with or without (control) connected EAT. Epicardial adipose tissue-connected (N = 6) RVOT had more portions of fibrosis than did control (N = 5) RVOT (160.3 ± 23.2 vs. 91.9 ± 13.4 μm2/mm2, P < 0.05). Epicardial adipose tissue-connected RVOT cardiomyocytes (n = 18) had lower negative resting membrane potential (-68 ± 1 vs. -73 ± 2 mV, P < 0.05); smaller action potential (AP) amplitude (108 ± 4 vs. 135 ± 6 mV, P < 0.005); and longer 90%, 50%, and 20% of AP duration repolarization (361 ± 18 vs. 309 ± 9 ms, P < 0.05; 310 ± 17 vs. 256 ± 13 ms, P < 0.05; and 182 ± 19 vs. 114 ± 24 ms, P < 0.05, respectively) than did control (n = 13) RVOT cardiomyocytes. Moreover, compared with control RVOT cardiomyocytes, EAT-connected RVOT cardiomyocytes had larger transient outward potassium currents, similar delayed rectifier potassium currents, smaller L-type calcium currents, and inward rectifier potassium currents. After ajmaline (10 μM, a sodium channel blocker) superfusion, high VA inducibility was observed through rapid pacing in EAT-connected RVOT but not in control RVOT.

CONCLUSIONS

Epicardial adipose tissue exerts distinctive electrophysiological effects on RVOT with a propensity towards VA induction, which might play a role in lipotoxicity pathogenesis-related ventricular arrhythmogenesis.

State of the art paper: Cardiovascular CT for planning ventricular tachycardia ablation procedures

In the last 20 years coronary computed tomography angiography (CCTA) gained a pivotal role in the evaluation of patients with suspected coronary artery disease (CAD) as finally recognized by the ESC guidelines on stable CAD. Technological advances have progressively improved the temporal resolution of CT scanners, contemporary reducing acquisition time, radiation dose and contrast volume needed for the whole heart volume acquisition, further expanding the role of cardiac CT beyond coronary anatomy evaluation. Aim of the present review is to discuss use and benefit of cardiac CT for the planning and preparation of VT ablation.

Procedural and long-term outcome after catheter ablation of idiopathic outflow tract ventricular arrhythmias: comparing manual, contact force, and magnetic navigated ablation

Aims

Currently, comparative data on procedural and long-term clinical outcome of outflow tract (OT) idiopathic ventricular arrhythmia (IVA) ablation with manual (MAN), contact force (CF), and magnetic navigation system (MNS) ablation are lacking. The aim of this study was to compare the procedural and long-term clinical outcome of MAN, CF, and MNS ablation of OT IVAs.

Methods and results

Seventy-three patients (31 MAN, 17 CF, and 25 MNS patients; consecutive per group) with OT IVA, who underwent catheter ablation in our centre were analysed. Procedural success rates (success at the end of the procedure), procedural data and long-term follow-up data were compared. Baseline patient demographics were comparable. Procedural success rates were similar (MAN 81%, 71% CF, and MNS 92%; P = 0.20). Median fluoroscopy time was shorter in the MNS group: MAN 29 (16-38), CF 37 (21-46), and MNS 13 (10-20) min (P = 0.002 for MNS vs. CF and MAN). The overall complication rate was: MAN 10%, CF 0%, and MNS 0% (P = 0.12). Median follow-up was: MAN 2184 (1672-2802), CF 1721 (1404-1913), and MNS 3031 (2524-3286) days (P <0.001). Recurrences occurred in MAN 46%, CF 50%, and MNS 46% (P = 0.97). Repeat procedures were performed in MAN 20%, CF 40%, and MNS 33% (P = 0.32).

Conclusion

Procedural and long-term clinical outcome of OT IVA ablation are equal for MAN, CF, and MNS. MNS has a favourable procedural safety profile due to the shorter fluoroscopy time compared with MAN and CF.

A novel noninvasive surface ECG analysis using interlead QRS dispersion in arrhythmogenic right ventricular cardiomyopathy

Background

This study investigated the feasibility of using the precordial surface ECG lead interlead QRS dispersion (IQRSD) in the identification of abnormal ventricular substrate in arrhythmogenic right ventricular cardiomyopathy (ARVC).

Methods

Seventy-one consecutive patients were enrolled and reclassified into 4 groups: definite ARVC with epicardial ablation (Group 1), ARVC with ventricular tachycardia (VT, Group 2), idiopathic right ventricular outflow tract VT without ARVC (Group 3), and controls without VT (Group 4). IQRSD was quantified by the angular difference between the reconstruction vectors obtained from the QRS-loop decomposition, based on a principal component analysis (PCA). Electroanatomic mapping and simulated ECGs were used to investigate the relationship between QRS dispersion and abnormal substrate.

Results

The percentage of the QRS loop area in the Group 1–2 was smaller than the controls (P = 0.01). The IQRSD between V1-V2 could differentiate all VTs from control (P<0.01). Group 1–2 had a greater IQRSD than the Group 3–4 (V4-V5,P = 0.001), and Group 1 had a greater IQRSD than Group 3–4 (V6-Lead I, P<0.001). Both real and simulated data had a positive correlation between the maximal IQRSD (γ = 0.62) and the extent of corresponding abnormal substrate (γ = 0.71, both P<0.001).

Conclusions

The IQRSD of the surface ECG precordial leads successfully differentiated ARVC from controls, and could be used as a noninvasive marker to identify the abnormal substrate and the status of ARVC patients who can benefit from epicardial ablation.

Discrepant effects of heart failure on electrophysiological property in right ventricular outflow tract and left ventricular outflow tract cardiomyocytes

Ventricular arrhythmias commonly arise from the right (RVOT) and left ventricular outflow tracts (LVOT) in patients without structural heart disease. Heart failure (HF) significantly increases the risk of ventricular arrhythmias. The regional differences and how HF affects the electrophysiological characteristics of RVOT and LVOT cardiomyocytes remain unclear. The whole-cell patch-clamp technique was used to investigate the action potentials and ionic currents in isolated single RVOT and LVOT cardiomyocytes from control rabbits and rabbits with HF induced by rapid ventricular pacing. Comparison with control LVOT cardiomyocytes showed that control RVOT cardiomyocytes have a shorter action potential duration (APD), smaller late Na+ currents (INa-late), larger transient outward (Ito) and larger delayed rectifier K+ currents (IKr-tail), but had similar L-type Ca2+ currents (ICa-L) and Na+/Ca2+ exchanger (NCX) current. HF increased APD, INa-late and NCX, but decreased ICa-L and Ito in RVOT cardiomyocytes. In contrast with this, HF decreased APD and ICa-L, but increased Ito and IKr-tail in LVOT cardiomyocytes. In conclusion, RVOT and LVOT cardiomyocytes had distinctive electrophysiological characteristics. HF differentially modulates action potential morphology and ionic currents in RVOT and LVOT cardiomyocytes.

The use of a novel signal analysis to identify the origin of idiopathic right ventricular outflow tract ventricular tachycardia during sinus rhythm: Simultaneous amplitude frequency electrogram transformation mapping

INTRODUCTION

The signal characteristics of intracardiac bipolar electrograms at the origin of idiopathic RVOT-VT during sinus rhythm remain unclear.

OBJECTIVE

The study sought to develop a novel real-time/online technique, simultaneous amplitude frequency electrogram transformation (SAFE-T), to quantify and localize the diseased ventricular substrate in idiopathic RVOT-VT.

METHODS

We retrospectively investigated the intracardiac bipolar recordings in 70 consecutive patients (26% male, mean age 42±12 years) who underwent successful radiofrequency catheter ablation of idiopathic RVOT-VT. We quantified the extent of the frequency fraction of ventricular potentials during sinus rhythm or ventricular pacing using a novel formula, the product of instantaneous amplitude and frequency, and showed that in a 3D geometry as an online SAFE-T map.

RESULTS

The characteristics of the HHT spectra of electrograms derived from VT origins demonstrated high frequency components (>70 Hz), which were independent of the rhythm. The density of the abnormal potentials at the VT origins were higher (VT origins, 7.5±2.3 sites/cm2 vs. surrounding myocardium, 1.5±1.3 sites/cm2, p<0.001), and were significantly decreased after ablation (0.7±0.6 sites/cm2, p<0.001). A small region of abnormal potentials were observed in the VT origins (mean area of 1.5±0.8 cm2). The SAFE-T maps predicted the VT origins with 92% sensitivity, 78% specificity with optimal cut-off value of >3.0 Hz·mV.

CONCLUSION

The online SAFE-T map was feasible for quantifying the diseased ventricular substrate, irrespective of the rhythm of activation, and can be used to identify the optimal ablation targets for idiopathic RVOT-VT. We found a limited region of abnormal potentials where the RVOT-VT origins were successfully ablated.

10-year follow-up after radiofrequency ablation of idiopathic ventricular arrhythmias from right ventricular outflow tract

Background

The aim of this study was to examine the effect of radiofrequency ablation (RFA) of ventricular arrhythmias from right ventricular outflow tract (RVOT) during long-term follow-up.

Methods

A follow-up analysis was conducted using an in-house questionnaire, as well as a qualitative assessment of the patients' medical records. The study population of 34 patients had a previous diagnosis of idiopathic VT or frequent PVCs from the RVOT, and received RFA treatment between 2002 and 2005.

Results

The main symptoms prior to RFA were palpitations (82.4%) and dizziness (76.5%). A reduction in symptoms following RFA was reported by 91.2% of patients (p < 0.001). Furthermore, there was a reduced use of antiarrhythmic medication after RFA (p < 0.001). General health perception classified on a scale of 1 (poor) to 4 (excellent), improved from median class 1 to 3 (p < 0.001) during long-term follow-up. The fitness to work increased from median class 3 to class 5 (1 = incapacitated, 5 = full time employment, p = 0.038), while the rate of patients in full time employment increased from 26.5% to 55.9% after RFA (p = 0.02).

Conclusions

A reduction of symptoms and use of antiarrhythmic medication, as well as an improvement in the general health perception and fitness to work after RFA of idiopathic ventricular arrhythmias can be demonstrated at ten-year follow-up.

The Different Substrate Characteristics of Arrhythmogenic Triggers in Idiopathic Right Ventricular Outflow Tract Tachycardia and Arrhythmogenic Right Ventricular Dysplasia: New Insight from Noncontact Mapping

Background

The aim of this study was to investigate the different substrate characteristics of repetitive premature ventricular complexed (PVC) trigger sites by the non-contact mapping (NCM).

Methods

Thirty-five consecutive patients, including 14 with arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC) and 21 with idiopathic right ventricular outflow tract tachycardia (RVOT VT), were enrolled for electrophysiological study and catheter ablation guided by the NCM. Substrate and electrogram (Eg) characteristics of the earliest activation (EA) and breakout (BO) sites of PVCs were investigated, and these were confirmed by successful PVC elimination.

Results

Overall 35 dominant focal PVCs were identified. PVCs arose from the focal origins with preferential conduction, breakout, and spread to the whole right ventricle. The conduction time and distance from EA to BO site were both longer in the ARVC than the RVOT group. The conduction velocity was similar between the 2 groups. The negative deflection of local unipolar Eg at the EA site (EA slope_3,5,10ms values) was steeper in the RVOT, compared to ARVC patients. The PVCs of ARVC occurred in the diseased substrate in the ARVC patients. More radiofrequency applications were required to eliminate the triggers in ARVC patients.

Conclusions/Interpretation

The substrate characteristics of PVC trigger may help to differentiate between idiopathic RVOT VT and ARVC. The slowing and slurred QS unipolar electrograms and longer distance from EA to BO in RVOT endocardium suggest that the triggers of ARVC may originate from mid- or sub-epicardial myocardium. More extensive ablation to the trigger site was required in order to create deeper lesions for a successful outcome.

How To Identify & Treat Epicardial Origin Of Outflow Tract Tachycardias

The right ventricle outflow tract (RVOT) is the most common site of origin of idiopathic ventricular arrhythmias. The typical outflow tract arrhythmias pattern on ECG is an inferior axis deviation and left bundle branch block when originated on the RVOT and right bundle branch block morphology when originated on the left ventricular outflow tract (LVOT). There are several ECG tricks for different locations of origin. An increased Maximum Deflection Index (MDI) suggests epicardial origin of arrhythmia. In general the result of ablation is very good, but sometimes there are difficult and unsuccessful procedures. The origin in the aortic cusps and epicardium are the reason for failure in some cases. When they are epicardial, the arrhythmias can be accessed by the venous system or by subxiphoid epicardial mapping.

Verapamil-sensitive idiopathic left ventricular tachycardia in a 6-month-old: unique considerations in diagnosis and management in an infant

Idiopathic left ventricular tachycardia of the Belhassen type is rare in infants. We present a 6-month-old infant girl with a wide-complex tachycardia with right bundle branch block QRS morphology, a superior axis, and atrioventricular dissociation, consistent with a left anterior fascicular tachycardia. Initial echocardiogram revealed depressed ventricular function. The tachycardia was unresponsive to therapeutic trials of adenosine, esmolol, procainamide, and lidocaine. There was brief conversion of the tachycardia to sinus rhythm with transesophageal atrial overdrive pacing, suggesting a reentrant mechanism of the arrhythmia. Ultimately, the judicious administration of intravenous verapamil resulted in termination of the arrhythmia, which has been sustained on oral therapy.

Distinctive electrophysiological characteristics of right ventricular out-flow tract cardiomyocytes

Ventricular arrhythmias commonly originate from the right ventricular out-flow tract (RVOT). However, the electrophysiological characteristics and Ca(2+) homoeostasis of RVOT cardiomyocytes remain unclear. Whole-cell patch clamp and indo-1 fluorometric ratio techniques were used to investigate action potentials, Ca(2+) homoeostasis and ionic currents in isolated cardiomyocytes from the rabbit RVOT and right ventricular apex (RVA). Conventional microelectrodes were used to record the electrical activity before and after (KN-93, a Ca(2+) /calmodulin-dependent kinase II inhibitor, or ranolazine, a late sodium current inhibitor) treatment in RVOT and RVA tissue preparations under electrical pacing and ouabain (Na(+) /K(+) ATPase inhibitor) administration. In contrast to RVA cardiomyocytes, RVOT cardiomyocytes were characterized by longer action potential duration measured at 90% and 50% repolarization, larger Ca(2+) transients, higher Ca(2+) stores, higher late Na(+) and transient outward K(+) currents, but smaller delayed rectifier K(+) , L-type Ca(2+) currents and Na(+) -Ca(2+) exchanger currents. RVOT cardiomyocytes showed significantly more pacing-induced delayed afterdepolarizations (22% versus 0%, P < 0.05) and ouabain-induced ventricular arrhythmias (94% versus 61%, P < 0.05) than RVA cardiomyocytes. Consistently, it took longer time (9 ± 1 versus 4 ± 1 min., P < 0.05) to eliminate ouabain-induced ventricular arrhythmias after application of KN-93 (but not ranolazine) in the RVOT in comparison with the RVA. These results indicate that RVOT cardiomyocytes have distinct electrophysiological characteristics with longer AP duration and greater Ca(2+) content, which could contribute to the high RVOT arrhythmogenic activity.

Catheter ablation of idiopathic premature ventricular contractions and ventricular tachycardias originating from right ventricular septum

BACKGROUND

Idiopathic premature ventricular contractions (PVCs) and ventricular tachycardias (IVTs) originating from the subtricuspid septum and near the His bundle have been reported. However, little is known about the prevalence, distribution, electrocardiographic characteristics and the efficacy of radiofrequency catheter ablation (RFCA) for the ventricular arrhythmias arising from the right ventricular (RV) septum. This study aimed to investigate electrocardiographic characteristics and effects of RFCA for patients with symptomatic PVCs/IVTs, originating from the different portions of the RV septum.

METHODOLOGY/PRINCIPAL FINDINGS

Characteristics of body surface electrocardiogram and electrophysiologic recordings were analyzed in 29 patients with symptomatic PVCs/IVTs originating from the RV septum. Among 581 patients with PVCs/IVTs, the incidence of ventricular arrhythmias originating from the RV septum was 5%. Twenty (69%) had PVCs/IVTs from the septal portion of the tricuspid valvular RV region (3 from superoseptum, 15 from midseptum, 2 from inferoseptum), and 9 (31%) from the septal portion of the basal RV (1 from superoseptum, 4 from midseptum, 4 from inferoseptum). There were different characteristics of ECG of PVCs/VT originating from the different portions of the RV septum. Twenty-seven of 29 patients with PVCs/IVTs arising from the RV septum were successfully ablated (93.1% acute success).

CONCLUSIONS/SIGNIFICANCE

ECG characteristics of PVCs/VTs originating from the different portions of the RV septum are different, and can help regionalize the origin of these arrhythmias. The septal portion of the tricuspid valvular RV region was the preferential site of origin. RFCA was effective and safe for the PVCs/IVTs arising from the RV septum.

Clinical characteristics and acute results of catheter ablation for outflow tract ventricular tachycardia or premature beats

PURPOSE

Contemporary outcome data of catheter ablation for outflow tract tachycardia (OTT) and ventricular premature beats (VPBs) are rare. The aim of this study was to describe the clinical characteristics, the acute procedure success rate, and the long-term survival of patients who underwent an ablation procedure for OTT or VPBs.

METHODS

The study was a single-center retrospective cohort study. All 82 consecutive OTT and VPB first ablation procedures between 1999 and 2009 were included. Patients with structural heart disease were excluded.

RESULTS

Mean age was 46 ± 13 years. Forty-three percent of the patients were male. All patients were alive after a median follow-up duration of 31 months (interquartile range, 14-65 months). Eighty-nine percent suffered from palpitations and 12 % had a history of syncope. Ventricular tachycardia was documented in 73 % and monomorphic VPBs in 99 %. Seventy-three percent of the patients were ablated in the right ventricular outflow tract, 15 % in the left ventricular outflow tract, and 12 % in the coronary cusps. Radiofrequency energy was used in 95 % of the patients, cryo energy in 9 %. Acute success was achieved in 78 %. Six patients (7 %) experienced a complication (five pericardial effusions, one pseudo-aneurysm of the femoral artery). Three patients needed pericardiocentesis (4 %).

CONCLUSION

Ablation for OTT and VPB is successful in the vast majority of cases, with a low but still existing complication rate. Long-term survival was excellent, underscoring the benign nature of this arrhythmia.

Catheter Ablation of Right Ventricular Outflow Tract Tachycardia: Value of Defining Coronary Anatomy

INTRODUCTION

Thermal damage to coronary arteries during catheter ablation has been previously reported. Coronary artery damage during LV outflow tract ventricular tachycardia is well recognized. However, the relationship of the coronary arteries to the RV outflow tract during catheter ablation has not been delineated. The purpose of this study was to define the relationship between the RV outflow tract and the coronary arteries utilizing arteriography, echocardiography, CT angiography, and gross anatomic pathology.

METHODS

The relationship of the coronaries to the RV outflow tract was analyzed in three patients groups: Group 1: patients (n = 10) undergoing RV outflow tract ventricular tachycardia; Group 2: patients (n = 50) undergoing CT coronary angiography; Group 3: patients (n = 4) undergoing echocardiography during open heart surgery and intracardiac echocardiography (ICE) during catheter ablation of atrial fibrillation (n = 5).

RESULTS

Group 1: The left main coronary artery was found to be 3.8 +/- 1.2 mm from the right ventricular outflow tract in patients undergoing ablation. Group 2: The minimum distance between the left main, left anterior descending, and right coronary artery to the RV outflow tract endocardial wall were 4.1 +/- 1.9 mm, 2.0 +/- 0.6 mm, and 4.3 +/- 1.9 mm (average +/- SD) respectively. Group 3: During open heart surgery using echocardiography, the minimum distance between the left main and the right coronary artery to the RV outflow tract were 3.4 +/- 0.35 mm and 2.0 +/- 0.1 mm, respectively. The distance between the let main coronary artery and the RVOT by ICE was 3.8 +/- 0.45 mm.

CONCLUSIONS

The major coronary arteries lie in close proximity of the RVOT, and their anatomic course should be taken into consideration during ablation of ventricular tachycardias arising from the RV outflow tract.

Remote magnetic navigation for mapping and ablating right ventricular outflow tract tachycardia

BACKGROUND

Navigation, mapping, and ablation in the right ventricular outflow tract (RVOT) can be difficult. Catheter navigation using external magnetic fields may allow more accurate mapping and ablation.

OBJECTIVES

The purpose of this study was to assess the feasibility of RVOT tachycardia ablation using remote magnetic navigation.

METHODS

Mapping and ablation were performed in eight patients with outflow tract ventricular arrhythmias. Tachycardia mapping was undertaken with a 64-polar basket catheter, followed by remote activation and pace-mapping using a magnetically enabled catheter. The area of interest was localized on the basket catheter in seven patients in whom an RVOT arrhythmia was identified. Remote navigation of the magnetic catheter to this area was followed by pace-mapping. Ablation was performed at the site of perfect pace-mapping, with earliest activation if possible.

RESULTS

Acute success was achieved in all patients (median four applications). Median procedural time was 144 minutes, with 13.4 minutes of patient fluoroscopy time and 3.8 minutes of physician fluoroscopy time. No complications occurred. One recurrence occurred during follow-up (mean 366 days).

CONCLUSION

RVOT tachycardias can be mapped and ablated using remote magnetic navigation, initially guided by a basket catheter. Precise activation and pace-mapping are possible. Remote magnetic navigation permitted low fluoroscopy exposure for the physician. Long-term results are promising.

Outflow tract tachycardia with R/S transition in lead V3

OBJECTIVES

The aim of this study was to analyze different anatomic mapping approaches for successful ablation of outflow tract tachycardia with R/S transition in lead V(3).

BACKGROUND

Idiopathic ventricular tachycardia can originate from different areas in the outflow tract, including the right and left ventricular endocardium, the epicardium, the pulmonary artery, and the aortic sinus of Valsalva. Although electrocardiographic criteria may be helpful in predicting the area of origin, sometimes the focus is complex to determine, especially when QRS transition in precordial leads is in V(3).

METHODS

We analyzed surface electrocardiograms of 33 successfully ablated patients with outflow tract tachycardia: 20 from the right ventricular outflow tract (RVOT) and 13 from different sites. The R/S transition was determined, and the different anatomic approaches needed for successful catheter ablation were studied.

RESULTS

Overall, R/S transition in lead V(3) was present in 19 (58%) of all patients. In these patients, mapping was started and successfully completed in the RVOT in 11 of 19 (58%) patients. The remaining eight patients with R/S transition in lead V(3) needed five additional anatomic accesses for successful ablation: from the left ventricular outflow tract (n = 3), aortic sinus of Valsalva (n = 2), coronary sinus (n = 1), the epicardium via pericardial puncture (n = 1), and the trunk of the pulmonary artery (n = 1), respectively.

CONCLUSIONS

A R/S transition in lead V(3) is common. In patients with outflow tract tachycardia with R/S transition in lead V(3), a stepwise endocardial and epicardial mapping through up to six anatomic approaches can lead to successful radiofrequency catheter ablation.

Is the Fascicle of Left Bundle Branch Involved in the Reentrant Circuit of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia?

The exact reentrant circuit of the verapamil-sensitive idiopathic left VT with a RBBB configuration remains unclear. Furthermore, if the fascicle of left bundle branch is involved in the reentrant circuit has not been well studied. Forty-nine patients with verapamil-sensitive idiopathic left VT underwent electrophysiological study and RF catheter ablation. Group I included 11 patients (10 men, 1 woman; mean age 25 +/- 8 years) with left anterior fascicular block (4 patients), or left posterior fascicular block (7 patients) during sinus rhythm. Group II included 38 patients (29 men, 9 women; mean age 35 +/- 16 years) without fascicular block during sinus rhythm. Duration of QRS complex during sinus rhythm before RF catheter ablation in group I patients was significant longer than that of group II patients (104 +/- 12 vs 95 +/- 11 ms, respectively, P=0.02). Duration of QRS complex during VT was similar between group I and group II patients (141 +/- 13 vs 140 +/- 14 ms, respectively, P=0.78). Transitional zones of QRS complexes in the precordial leads during VT were similar between group I and group II patients. After ablation, the QRS duration did not prolong in group I or group II patients (104 +/- 11 vs 95 +/- 10 ms, P=0.02); fascicular block did not occur in group II patients. Duration and transitional zone of QRS complex during VT were similar between the two groups, and new fascicular block did not occur after ablation. These findings suggest the fascicle of left bundle branch may be not involved in the antegrade limb of reentry circuit in idiopathic left VT.

Endocardial mapping of right ventricular outflow tract tachycardia using noncontact activation mapping

INTRODUCTION

Activation mapping and pace mapping identify successful ablation sites for catheter ablation of right ventricular outflow tract (RVOT) tachycardia. These methods are limited in patients with nonsustained tachycardia or isolated ventricular ectopic beats. We investigated the feasibility of using noncontact mapping to guide the ablation of RVOT arrhythmias.

METHODS AND RESULTS

Nine patients with RVOT tachycardia and three patients with ectopic beats were studied using noncontact mapping. A multielectrode array catheter was introduced into the RVOT and tachycardia was analyzed using a virtual geometry. The earliest endocardial activation estimated by virtual electrograms was displayed on an isopotential color map and measured 33 +/- 13 msec before onset of QRS. Virtual unipolar electrograms at this site demonstrated QS morphology. Guided by a locator signal, ablation was performed with a mean of 6.9 +/- 2.2 radiofrequency deliveries. Acute success was achieved in all patients. During follow-up, one patient had a recurrence of RVOT tachycardia. Compared with patients (n = 21) who underwent catheter ablation using a conventional approach, a higher success rate was achieved by noncontact mapping. Procedure time was significantly longer in the noncontact mapping group. Fluoroscopy time was not significantly different in the two groups.

CONCLUSION

Noncontact mapping can be used as a reliable tool to identify the site of earliest endocardial activation and to guide the ablation procedure in patients with RVOT tachycardia and in patients with ectopic beats originating from the RVOT.

Verapamil Sensitive Idiopathic Ventricular Tachycardia in an Infant

Idiopathic ventricular tachycardia is rare, especially in infants. We report here on an 8 month-old female infant who presented with tachycardia with a heart rate of 186 beats/ min. An electrocardiogram showed a right bundle branch block pattern, a QRS duration of 80 msec, a superior QRS axis, atrioventricular dissociation, and occasional fusion and capture beats. Suspected ventricular tachycardia was treated with lidocaine, propranolol and amiodarone, but in vain. The tachycardia was terminated and well controlled with the use of verapamil. According to an electrocardiogram and her clinical response, verapamil-sensitive idiopathic ventricular tachycardia was diagnosed with the arrhythmic origin in the left posterior fascicle.

Idiopathic sustained left ventricular tachycardia in pediatric patients

BACKGROUND

Idiopathic sustained ventricular tachycardia originating from the left ventricle (ILVT) has been an indication for catheter ablation. The present study evaluated the clinical features, long-term prognosis and indications for treatment in pediatric patients with ILVT.

METHODS

The subjects of the present study were eight patients (four males and four females) with a mean age at onset of 11.0 years (range 3-15 years). The mean follow-up period was 7.7 years (range 2.1-11.3 years).

RESULTS

In electrophysiologic studies, intravenously administered verapamil was effective for the termination of tachycardia in all six patients who received this treatment and for the prevention of tachycardia in four of five patients. Oral administration of verapamil was effective in five of seven patients. Propranolol or flecainide was added to the treatment protocol for two patients who did not respond to verapamil alone. Tachycardia disappeared without drugs in four patients during the follow-up period and became non-sustained in another patient. Two of three patients with persistent tachycardia underwent catheter ablation. Pharmacologic treatment was very effective for ILVT among these patients.

CONCLUSIONS

Pharmacologic therapy, such as with verapamil, is still the treatment of choice for ILVT because of a good long-term prognosis and potential risks and complications by manipulation of catheter ablation.

Ventricular arrhythmias in normal hearts

Idiopathic ventricular tachycardia (VT) is characterized by two predominant forms. The most common form originates from the right ventricular outflow tract and presents as repetitive monomorphic VT or exercise-induced VT. The tachycardia is adenosine sensitive and is thought to be because of cAMP-mediated triggered activity. The other major form of idiopathic VT is owing to verapamil-sensitive intrafascicular re-entrant tachycardia, which most often originates in the region of the left posterior fascicle. Both forms of idiopathic VT can be readily treated with radiofrequency catheter ablation.

Electrocardiographic predictors of successful ablation of tachycardia or bigeminy arising in the right ventricular outflow tract

Among various electrocardiographic variables, the QRS duration in V2 was found to be the best discriminator of outcome in patients undergoing radiofrequency catheter ablation of the right ventricular outflow tract tachycardia and/or bigeminy. If the QRS duration is <160 ms in lead V2, the probability of successful ablation is lower than if the QRS duration is longer.