Radiofrequency catheter ablation of idiopathic left ventricular tachycardia guided by a Purkinje potential

Verapamil-Sensitive Upper Septal Idiopathic Left Ventricular Tachycardia: Prevalence, Mechanism, and Electrophysiological Characteristics

OBJECTIVES

This study sought to demonstrate the prevalence, mechanism, and electrocardiographic and electrophysiological characteristics of upper septal idiopathic left fascicular ventricular tachycardia (US-ILVT).

BACKGROUND

ILVT is classified into left anterior and posterior types with no clear data about US-ILVT.

METHODS

Among 193 ILVT patients, we identified 12 patients (6.2%; age 41 ± 22 years, 7 men) with US-ILVT.

RESULTS

Of 12 patients with US-ILVT, 6 patients (50%) had previous history of radiofrequency catheter ablation for common ILVT. Sustained VT (cycle length: 349 ± 53 ms) was seen in all patients with a QRS interval slightly wider (104 ± 18 ms) than that during sinus rhythm (90 ± 19 ms). The VT exhibited an identical QRS configuration as sinus rhythm in 6 (50%) and incomplete right bundle branch block configuration in another 6. His-ventricular interval during VT was always shorter than that during sinus rhythm (27 ± 5 ms vs. 47 ± 10 ms). Purkinje potentials were activated in a reverse direction to that of common ILVT; namely, the diastolic potential (P₁) was activated retrogradely but the pre-systolic potential (P₂) was activated antegradely. At the left upper-middle ventricular septum, P₁ potential was recorded during VT, preceding the QRS by 54 ± 20 ms. Radiofrequency catheter ablation at that site eliminated the VT with no recurrence during a 58 ± 35 months of follow-up.

CONCLUSIONS

US-ILVT is an identifiable VT that shares common criteria with ILVT and has a narrow QRS interval. Some US-ILVT cases appeared after common ILVT ablation. It is a reverse type of common ILVT (orthodromic form) with baseline morphological abnormalities that might provide a potential substrate for such VT.

Catheter Ablation of Fascicular Ventricular Tachycardia: Long-Term Clinical Outcomes and Mechanisms of Recurrence

Supplemental Digital Content is available in the text.

Fascicular ventricular tachycardia (FVT) is a common form of sustained idiopathic left ventricular tachycardia with an Asian preponderance. This study aimed to prospectively investigate long-term clinical outcomes of patients undergoing ablation of FVT and identify predictors of arrhythmia recurrence.

Insights into the mechanism of idiopathic left ventricular tachycardia: a case report and literature review

Left ventricular posterior fascicular tachycardia (LVPFT) is an idiopathic form of VT characterized by right bundle branch block morphology and left axis deviation. The mechanism of LPFVT is thought to be localized reentry close to the posterior fascicle. We present the case of a 24-year-old medical student who was admitted to the emergency department complaining of palpitations. The ECG showed an aspect suggestive of LVPFT. Vagal maneuvers, adenosine and i.v. Metoprolol were ineffective in terminating the arrhythmia. Conversion to sinus rhythm was obtained 10 h later, with i.v Amiodarone. The ECG in sinus rhythm showed left posterior fascicular block. Because antiarrhythmic drugs were not desired by the patient, VT ablation was proposed. The electrophysiological study identified the mechanism of arrhythmia to be reentry using the slowly conducting verapamil-sensitive fibers as the antegrade limb and the posterior fascicle as the retrograde limb. Radiofrequency applications near the posterior fascicle, in the lower half of the interventricular septum, at the junction of the two proximal thirds with the distal third interrupted the tachycardia and made it non-inducible at programmed stimulation. The case is unusual as the patient had a left posterior fascicular block during sinus rhythm before ablation. This demonstrates that the reentry circuit of VT does not need antegrade conduction through the posterior fascicle for perpetuation.

Ablation of idiopathic ventricular tachycardia originating from posterior mitral annulus by using electroanatomical mapping

Idiopathic ventricular tachycardia (IVT) is an important type of arrhythmia, which has distinct electrocardiographic features and treatment options. Most of the cases originate from right ventricular outflow tract and less frequently from the left ventricular outflow tract. IVTs originating from mitral annulus are rare, and little is known about the efficacy of radiofrequency catheter ablation in this form. We hereby present a rare case of IVT arising from posterior mitral annulus. The electrocardiographic, electrophysiological, and electroanatomical characteristics of this tachycardia are discussed.

Creation of partial fascicular block: an approach to ablation of idiopathic left ventricular tachycardia in the pediatric population

BACKGROUND

Catheter ablation of idiopathic left ventricular tachycardia in the pediatric population remains challenging. A recent multicenter study reported limited success with 14% not undergoing ablation due to inability to induce ventricular tachycardia (VT) or blood pressure instability during tachycardia. Creating complete or partial fascicular block with radiofrequency catheter ablation is a technique that may eliminate VT. This approach is performed during sinus rhythm, enabling atrioventricular conduction monitoring and maintaining stable hemodynamics. Importantly, induction of VT is not necessary for mapping or assessing efficacy of the procedure.

METHODS

A retrospective review of pediatric patients (3-17 years) with recurrent, documented idiopathic left ventricular tachycardia by electrocardiogram who received catheter ablation by creating fascicular block as a therapeutic endpoint was performed. All had ablation at the site of an identified Purkinje potential.

RESULTS

There were six patients with idiopathic left ventricular tachycardia, five originating from the posterior fascicle and one from the anterior fascicle. VT was not induced or spontaneous in four patients using programmed stimulation and isoproterenol infusion. All patients had a QRS axis shift following ablation, though none met criteria for fascicular block. At follow up (7-49 months, mean 27 months), all patients had persistence of this shift. There were no recurrences of VT and none of the patients were taking antiarrhythmic medication.

CONCLUSION

The technique of creating partial fascicular block appears to be a safe and effective approach to ablation of idiopathic left ventricular tachycardia in children.

Successful control of life-threatening polymorphic ventricular tachycardia by radiofrequency catheter ablation in an infant

We present a case of a 9-month-old girl in whom malignant polymorphic ventricular tachycardia (VT) was successfully controlled by radiofrequency catheter ablation under guidance with a three-dimensional mapping system. The VTs originated from the left ventricular lateral wall, left ventricular anterior wall, and left ventricular apex. At least six types of VTs were documented during the electrophysiology study. All VTs were successfully controlled after two sessions of radiofrequency catheter ablation, and she was discharged from our hospital on propranolol, mexiletine, flecainide, and aprindine.

Demonstration of posterior fascicle to myocardial conduction block during ablation of idiopathic left ventricular tachycardia: an electrophysiological predictor of long-term success

BACKGROUND

Idiopathic left ventricular tachycardia (ILVT) is a common form of ventricular tachycardia (VT) in structurally normal heart. Different methods have been proposed for radiofrequency ablation (RFA) of ILVT that have good short-term results but recurrence is higher. Termination of tachycardia during RFA and/or noninduciblity has been the procedural end point.

OBJECTIVE

To describe electrophysiological markers that add to long-term freedom from recurrences.

METHODS

Fifteen patients with ILVT underwent RFA guided by 3-dimensional electroanatomical mapping. After creating a 3-dimensional geometry of the left ventricle (LV), the conduction system of the LV was mapped by tracing from His recording from the left ventricular outflow tract and distally till the fascicles and perifascicular myocardium. VT was induced by using programmed electrical stimulation. Ablation was done targeting the distal posterior fascicle and extended linearly to the surrounding myocardium till conduction block was achieved between the fascicle-Purkinje network and the left ventricular myocardium.

RESULTS

All patients (13 men; mean age 32 ± 9 years) had inducible VTs. The mean tachycardia cycle length was 320 ± 28 ms. Radiofrequency energy was given to the distal posterior fascicle and the myocardium, with an aim to achieve a myocardial-fascicular conduction block in addition to the termination of VT and noninducibility. Ablation was successful in all. No recurrence of tachycardia was seen in any patient on follow-up (20.8 ± 8.5 months).

CONCLUSIONS

Distal posterior fascicle and Purkinje-myocardial junction is an effective target site for ILVT ablation. The demonstration of myocardial to fascicle conduction block serves as an important electrophysiological marker of successful ablation and improved long-term success.

Biophysics and clinical utility of irrigated-tip radiofrequency catheter ablation

Catheter ablation by radiofrequency (RF) energy has successfully eliminated cardiac tachyarrhythmias. RF ablation lesions are created by thermal energy. Electrode catheters with 4-mm-tips have been adequate to ablate arrhythmias located near the endocardium; however, the 4-mm-tip electrode does not readily ablate deeper tachyarrhythmia substrate. With 8- and 10-mm-tip RF electrodes, ablation lesions were larger; yet, these catheters are associated with increased risk for coagulum, char and thrombus formation, as well as myocardial steam rupture. Cooled-tip catheter technology was designed to cool the electrode tip, prevent excessive temperatures at the electrode tip-tissue interface, and thus allow continued delivery of RF current into the surrounding tissue. This ablation system creates larger and deeper ablation lesions and minimizes steam pops and thrombus formation. The purpose of this article is to review cooled-tip RF ablation biophysics and outcomes of clinical studies as well as to discuss future technological improvements.

Identification of the slow conduction zone in a macroreentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia using electroanatomic mapping

BACKGROUND

Although idiopathic left ventricular tachycardia (ILVT) has been shown to possess a slow conduction zone (SCZ), the details of the electrophysiological and anatomic aspects are still not well understood.

OBJECTIVE

We hypothesized that the SCZ can be identified using a 3-dimensional electroanatomic (EA) mapping system.

METHODS

Ten patients with ILVT were mapped using a 3-dimensional electroanatomic (EA) mapping system. After a 3-dimensional endocardial geometry of the left ventricular was created, the conduction system with left Purkinje potential (PP) and the SCZ with diastolic potential (DP) in LV were mapped during sinus rhythm (SR) and ventricular tachycardia (VT) and were tagged as special landmarks in the geometry. The electrophysiological and anatomic aspects of it were investigated.

RESULTS

EA mapping during SR and VT was successfully performed in 7 patients, during VT in 3 patients. The SCZ with DPs located at the inferoposterior septum was found in 7 patients during SR and all patients during VT. The length of the SCZ was 25.2 ± 2.3 mm with conduction velocity 0.08 ± 0.01 m/s. No differences in these parameters were found between patients during SR and VT (P > 0.05). An area with PP was found within the posterior septum. A crossover junction area with DP and PP was found in 7 patients during SR and VT. This area with DP and PP during SR coincided or were in proximity to such area during VT and radiofrequency ablation targeting the site within the area abolished VT in all patients.

CONCLUSION

The ILVT substrate within the junction area of the SCZ and the posterior fascicular can be identified and can be used to guide the ablation of ILVT.

Electroanatomical characteristics of idiopathic left ventricular tachycardia and optimal ablation target during sinus rhythm: significance of preferential conduction through Purkinje fibers

PURPOSE

We hypothesized that Purkinje potential and their preferential conduction to the left ventricle (LV) posteroseptum during sinus rhythm (SR) are part of reentrant circuits of idiopathic left ventricular tachycardia (ILVT) and reentry anchors to papillary muscle.

MATERIALS AND METHODS

In 14 patients with ILVT (11 men, mean age 31.5±11.1 years), we compared Purkinje potential and preferential conduction during SR with VT by non-contact mapping (NCM). If clear Purkinje potential(SR) was observed in the LV posteroseptum and the earliest activation site (EA) of preferential conduction at SR (EA(SR)) was well matched with that of VT (EA(VT)), EA(SR) was targeted for radiofrequency catheter ablation (RFCA). Also, the anatomical locations of successful ablation sites were evaluated by echocardiography in five additional patients.

RESULTS

1) All induced VTs exhibited clear Purkinje potential(VT) and preferential conduction in the LV posteroseptum. The Purkinje potential(VT) and EA(VT) was within 5.8±8.2 mm of EA(SR). However, the breakout sites of VT were separated by 30.2±12.6 mm from EA(VT) to the apical side. 2) Purkinje potential(SR) demonstrated a reversed polarity to Purkinje potential(VT), and the interval of Purkinje potential(SR)-QRS was longer than the interval of Purkinje potential(VT)-QRS (p<0.02) 3) RFCA targeting EA(SR) eliminated VT in all patients without recurrence within 23.3±7.5 months, and the successful ablation site was discovered at the base of papillary muscle in the five additional (100%) patients.

CONCLUSION

NCM-guided localization of EA(SR) with Purkinje potential(SR) matches well with EA(VT) with Purkinje potential(VT) and provides an effective target for RFCA, potentially at the base of papillary muscle in patients with ILVT.

Case of Idiopathic Left Ventricular Tachycardia (ILVT)

Introduction:

The objective of this case report is to illustrate a case of idiopathic left ventricular tachycardia (ILVT). It is important to distinguish key features to differentiate ILVT from other types of ventricular tachycardias.

Clinical picture:

A 33-year-old male presented with palpitations. Clinical examination was unremarkable, except a heart rate of 170 beats/min. ECG showed a right bundle branch morphology, left superior frontal plane and a relatively narrow QRS duration. A diagnosis of ILVT was made.

Treatment:

Intravenous verapamil was given and the ILVT was terminated.

Conclusion:

ILVT differs from other types of VT, such as right ventricular outflow tract (RVOT), in terms of mechanisms, site of origin and management. Overall, ILVT has a good prognosis, compared to VTs seen in ischaemic cardiomyopathy.

MEMBRANE AND TISSUE LEVEL CONTRIBUTIONS TO PURKINJE-VENTRICULAR INTERACTIONS: A MODEL STUDY

Purkinje-to-ventricular (P-to-V) propagation and electrotonic modulation of repolarization at discrete Purkinje-ventricular junctions (PVJs) depend on differences in the ionic currents and tissue structure of the P network and the V myocardium. We used computer simulations to assess these membrane and tissue level contributions to P-V interactions. At the membrane level, we used the DiFrancesco-Noble membrane equations to model P ionic kinetics and the Luo-Rudy dynamic membrane equations to model V ionic kinetics. At the tissue level, we modeled the P network as a layer of branching cables, and we modeled a single myocardial sheet with an anisotropic layer of excitable cells. P-to-V propagation was enhanced at the tissue level when multiple wavefronts in the branching P network collided at the PVJ. At the membrane level, P-to-V propagation was enhanced by a reduced transient outward current (Ito) in the P layer. Repolarization at the PVJ was also modulated by both membrane and tissue level contributions. Under nominal conditions, action potential duration (APD) shortened in the P layer and prolonged in the V layer. However, when the V mass was reduced, both P and V cell APDs shortened during coupling with nominal Ito. Subsequent Ito inhibition restored coupling-induced prolongation of the V action potential in the reduced V mass. These results suggest that under physiologic conditions, both membrane and tissue level contributions to P-V interactions are important, while membrane level contributions become even more important under pathologies that reduce the difference in P and V tissue size, particularly in the setting of healed myocardial infarction.

The characteristics of verapamil-sensitive idiopathic left ventricular tachycardia combined with a left accessory pathway and the effect of radiofrequency catheter ablation

AIMS

Verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) combined with a left accessory pathway (AP) is a relatively rare condition. This study examines the characteristics of patients with this condition and the effect of radiofrequency catheter ablation (RFCA).

METHODS AND RESULTS

Catheter ablation was performed on 140 ILVT patients at a single centre from January 2004 to December 2009. A concealed left AP was found in seven patients (5%), all of whom were male, with an average age of 21 ± 9 years. Sustained ILVT and orthodromic atrioventricular reentrant tachycardia (AVRT) were induced in all seven patients. Retrograde activation through a bystander AP occurred concomitantly with ILVT, with an average tachycardia length of 346 ± 29 ms (range 310-400 ms). The location of the APs in four patients was left posterior, two of which showed a slow and decremental property, while in three it was left lateral. Ablation via a retrograde transaortic approach was performed in the seven patients. The left AP was ablated first in six patients, but ILVT was no longer induced in one and became non-sustained in another. In the seventh patient, ILVT was ablated first and this proved successful.

CONCLUSIONS

Among patients with IVLT, 5% had a concomitant left AP, most of who were young men. The location of the left AP was mainly posterior and lateral, with 30% showing a slow and decremental property. Idiopathic left ventricular tachycardia and AP should be ablated simultaneously.

Nonfluoroscopic and radiation-limited ablation of ventricular arrhythmias in children and young adults: a case series

The purpose of this study was to report the feasibility and procedural technique of minimal or no fluoroscopy in the ablation of ventricular arrhythmias in the pediatric population. A retrospective review was performed of all patients <21 years old who underwent ablation of ventricular arrhythmias using three-dimensional (3D) mapping with no or minimal fluoroscopy at a single institution. Five patients underwent electrophysiology studies for ventricular tachycardia or frequent premature ventricular complexes. Three patients had right-sided arrhythmias, and two patients had left-sided arrhythmias. Electro-anatomic mapping with the 3D EnSite NavX system and radiofrequency ablation was used in all patients. No fluoroscopy was used in the patients with right-sided arrhythmias. The two patients with left-sided arrhythmias had 1.0 and 1.9 min of fluoroscopy, respectively. The mean procedure time was 168 min (range 95 to 270). There has been no recurrence at mean follow-up of >1 year. Three-dimensional mapping systems have allowed pediatric electrophysiologic procedures to be performed with minimal to no fluoroscopy in patients with challenging arrhythmias, including ventricular arrhythmias. The decrease in radiation exposure decreases the risk of long-term adverse sequelae resulting from radiation exposure, which is especially important in children.

Ablation of idiopathic ventricular tachycardia

Idiopathic ventricular arrhythmias occur in patients without structural heart disease. They can arise from a variety of specific areas within both ventricles and in the supravalvular regions of the great arteries. Two main groups need to be differentiated: arrhythmias from the outflow tract (OT) region and idiopathic left ventricular, so-called fascicular, tachycardias (ILVTs). OT tachycardia typically originates in the right ventricular OT, but may also occur in the left ventricular OT, particularly in the sinuses of Valsalva or the anterior epicardium or the great cardiac vein. Activation mapping or pace mapping for the OT regions and mapping of diastolic potentials in ILVTs are the mapping techniques that are typically used. The ablation of idiopathic ventricular arrhythmias is highly successful, associated with only rare complications. Newly recognized entities of idiopathic ventricular tachycardias are those originating in the papillary muscles and in the atrioventricular annular regions.

Premature ventricular contractions originating from the left ventricular septum: results of radiofrequency catheter ablation in twenty patients

BACKGROUND

RFCA has been established as an effective and curative therapy for severely symptomatic PVC from the outflow tract in structurally normal hearts. However, it is unknown whether PVCs originating from the left ventricular septum, are effectively eliminated by RFCA. This study aimed to investigate electrophysiologic characteristics and effects of radiofrequency catheter ablation (RFCA) for patients with symptomatic premature ventricular contraction (PVC) originating from the left ventricular septum without including fascicular PVCs.

METHODS

Characteristics of body surface electrocardiogram (ECG) and electrophysiologic recordings endocardiogram in a successful RFCA target were analyzed in 20 patients with symptomatic PVCs originating from the left ventricular septum. RFCA was performed using pace mapping and activation mapping.

RESULTS

The QRS morphology of PVCs originating from the left ventricular septum is similar to that seen in fascicular tachycardia. Most of the PVCs originated from the left septum appears in the form of ventricular parasystole. The incidence of ventricular parasystole was 70%. Sustained ventricular tachycardia was not inducible by electrical stimulation and isoproterenol infusion in all 20 patients, ablation at the site recording the earliest Purkinje potential was not effective in all 20 patients, and Purkinje potentials were not identified at successful sites during point mapping. Sixteen patients were successful with RFCA using pace mapping and activation mapping, 3 failed, and 1 recurrent.

CONCLUSION

Although the ECG characteristics of the PVCs arising from the left ventricular septum are similar to that seen in fascicular tachycardia, the electrophysiologic characteristics are different between the two types of PVCs. The distinguishing characteristic of the PVCs is that Purkinje potentials were not present at the site of successful ablation, suggesting a myocardial as opposed to fascicular substrate. RFCA is an effective curative therapy for symptomatic PVCs originating from the left ventricular septum (not from the left anterior and posterior fascicle).

Ablation strategies in a patient with Belhassen tachycardia

The verapamil-sensitive Belhassen tachycardia is a ventricular reentrant tachycardia, involving left-sided Purkinje fibers and abnormal Purkinje or myocardial tissue. Ablation is feasible, targeting a diastolic fascicular potential in the apical left ventricle.

CASE REPORT

We report on a 13-year-old girl with left posterior fascicular ventricular tachycardia. Tachycardia stopped during ablation, targeting a left-sided distal fascicular potential, and afterward, there was no tachycardia inducible, but it reoccurred 2 weeks later. During a second procedure, we transected the left posterior fascicle by a line, also with early success. After a further recurrence, we ablated a longer proximal segment of the left posterior fascicle including its most proximal electrograms. After this ablation, there was no further recurrence.

CONCLUSION

In refractory patients, proximal ablation of the posterior fascicle might be indicated.

The significance of repetitive ventricular responses induced by radiofrequency energy application for idiopathic left ventricular tachycardia

In radiofrequency (RF) ablation for idiopathic left ventricular tachycardia (ILVT), the termination of tachycardia during RF ablation is considered a hallmark of success. However, in cases of patients with difficulty of induction of ventricular tachycardia (VT), the evaluation of procedural success can be problematic. We have observed thermal responses reflected as ventricular rhythm change to RF energy delivered on sinus rhythm for ILVT. We therefore describe the significance of repetitive ventricular responses. The study subjects were 11 ILVT patients for whom RF energy was delivered during sinus rhythm because of difficulty in re-induction of tachycardia. During each energy delivery, we focused on the occurrence of repetitive ventricular responses especially exhibiting a similar morphology to clinical VT. The repetitive ventricular responses were noted in 10 of 11 patients. Two patients received a second procedure due to the recurrence of ILVT. The mean follow-up period was 36.2+/-12.8 months. The clinical course of the remaining patients was favorable and without recurrence of ILVT. Based on the favorable clinical outcomes, ablation-induced repetitive ventricular responses with similar QRS morphology to clinical ILVT are useful markers for selecting an ablation site and could be used as an additional mapping method, termed as "thermal mapping".