Repetitive ventricular responses induced by radiofrequency ablation for idiopathic ventricular tachycardia originating from the outflow tract of the right ventricle

Prognostic significance of accelerated ventricular response during radiofrequency ablation of premature ventricular complexes

Background

Accelerated ventricular response is frequently observed during radiofrequency ablation (RFA) of premature ventricular complexes (PVCs). We hypothesized that acceleration indicates an appropriate site and adequate injury to the arrhythmogenic tissue, and sought to investigate its value in predicting the outcome.

Methods

We retrospectively analyzed RFA procedures performed for PVCs in our institution from 2011 to 2019.

Results

Fifty-eight patients (29 male; age 42.7 ± 15.6 years) underwent 62 RFA procedures. The most common site was the right ventricular outflow tract (67.7%). Acute success was seen in 88.7%. Accelerated ventricular response was observed in 60.0% of the successful procedures. After a median follow-up of 14.0 months (IQR: 6.0–26.6 months), 16 patients had a recurrence. Recurrence was significantly lower in the group with acceleration than in the group without acceleration (12.5% vs. 57.1%; log-rank P < 0.001). The 1-year recurrence rate was 6.5% in the acceleration group and 41.6% in the group without acceleration. On multivariable analysis the adjusted hazard ratio was 0.17 (95% CI, 0.04–0.64; Cox regression P = 0.009). The sensitivity, specificity, positive predictive, and negative predictive values of accelerated response to predict long-term success were 75.7%, 75.0%, 87.5%, and 57.2%, respectively.

Conclusions

The recurrence after PVC ablation is significantly lower when an accelerated response was observed at the successful location during RFA. This can be an additional useful marker of long-term success.

[Premature ventricular contractions and tachycardia in a structurally normal heart : Idiopathic PVC and VT]

Premature ventricular contractions (PVC) are a common, often incidental and mostly benign finding. Treatment is indicated in frequent and symptomatic PVC or in cases of worsening of left ventricular function. Idiopathic ventricular tachycardia (VT) is mostly found in patients with a structurally healthy heart. These PVC/VT usually have a focal origin. The most likely mechanism is delayed post-depolarization. Localization of the origin is based on the creation of an activation map with or without combination of pace mapping. Idiopathic PVC/VT are most frequently located on the outflow tracts of the right and left ventricles, including the aortic root. Other typical locations include the annulus of the tricuspid or mitral valve, papillary muscles and Purkinje fibers. Catheter ablation is an alternative to antiarrhythmic medication in symptomatic monomorphic PVC/VT. The success rate is good whereby mapping and ablation can often represent a challenge. This article is the fifth part of a series dedicated to specific advanced training in the field of special rhythmology and invasive electrophysiology. It describes the pathophysiological principles, types and typical findings that can be obtained during an electrophysiological investigation.

Long-term mode and timing of premature ventricular complex recurrence following successful catheter ablation

PURPOSE

Catheter ablation of premature ventricular contractions (PVCs) is highly successful and has become the hallmark treatment for symptomatic or highly prevalent cases. However, few studies exist that evaluate the outcomes of ablation and likely mechanisms of PVC recurrence beyond 1 year of follow-up.

METHODS

This study is a retrospective analysis of patients who underwent catheter ablation for symptomatic PVCs with acute procedural success and had clinical follow-up ≥ 12 months.

RESULTS

Forty-four patients (24 women; age 53.5 ± 4.8 years) following acutely successful PVC ablation with long-term follow-up were studied. At a mean of 36 ± 6 months, overall long-term ablation success was 75% (33/44 patients). Notably, recurrence of the targeted PVC focus was low (6.8%, 3/44 patients); the majority of recurrences were from a new source location (18.2%, 8/44 patients). The time course for targeted versus de novo PVC recurrences was significantly different: recurrence of a PVC similar to the targeted PVC morphology occurred at a mean of 5.0 ± 2.0 months, while recurrence of a PVC different from the index case occurred at a mean of 35.8 ± 17.1 months (p = 0.01). Non-ischemic cardiomyopathy was associated with increased risk of PVC recurrence (odds ratio [OR] 14.50 (95% confidence interval [CI] 1.92-109.33, p = 0.01)) and was a significant negative prognostic factor in multivariate analysis for PVC recurrence survival (hazard ratio [HR] 4.63, 95% CI 1.03-20.74, p = 0.04).

CONCLUSIONS

The majority of long-term PVC recurrences occur late in follow-up, at locations remote from the targeted PVC source or sources. Such sites may represent ongoing substrate evolution; additional work is required to determine the precise substrate alterations which promote such arrhythmogenic changes.

Conventional mapping and ablation of focal ventricular tachycardias in the healthy heart

Ventricular tachycardias (VT) in the healthy heart, also known as idiopathic VTs, often have a focal origin. Triggered activity due to delayed after-depolarization is the most likely mechanism of focal VTs. Localization of the site of origin of focal VTs is based on activation mapping with or without combination with pace mapping. The characteristic anatomic site of origin of idiopathic VTs is the right and left outflow tract. Other sites include the tricuspid and mitral annulus, the papillary muscles, and Purkinje fibers. Catheter ablation is indicated for monomorphic symptomatic VT and can be an alternative to antiarrhythmic drugs. Success rates are high, but mapping and ablation can be challenging. We review the main electrophysiological findings and the important clues for ablation of focal VTs. Specific considerations for each location are considered.

Catheter ablation for ventricular tachycardia following surgical treatment of pulmonary stenosis with intact ventricular septum

AIMS

This study was aimed to report the characteristics and treatment of ventricular tachycardia (VT) following surgical treatment of pulmonary stenosis with intact ventricular septum.

METHODS AND RESULTS

Five patients underwent radiofrequency catheter ablation for sustained monomorphic left bundle branch block (LBBB) type VT who previously underwent surgical treatment of pulmonary stenosis. Except stimulation, voltage and activation mapping was performed using three-dimensional (3D) electro-anatomic mapping and ablation was applied accordingly. Four VTs were induced during EP study. Two VTs were focal and the earliest activity was targeted in the right ventricular apex (RVA). The other two VTs were reentrant and the critical isthmus located in the mid-lateral wall and anterior wall of right ventricle, respectively. Ablation abolished all inducible VTs in four patients. In the patient whose VT was non-inducible, radiofrequency (RF) energy was delivered to the RVA where pacing mapping matched the clinical VT. One focal VT recurred 60 months after the initial RF ablation. Repeat mapping and ablation was performed and no VT recurred over a 24-month period.

CONCLUSIONS

The mechanism of VT following surgical treatment of pulmonary stenosis can be either focal or reentrant. Ablation of this subgroup of VT is feasible.

Radiofrequency catheter ablation of idiopathic right ventricular outflow tract arrhythmias

Idiopathic ventricular arrhythmias (VA) consist of various subtypes of VA that occur in the absence of clinically apparent structural heart disease. Affected patients account for approximately 10% of all patients referred for evaluation of ventricular tachycardia (VT). Arrhythmias arising from the outflow tract (OT) are the most common subtype of idiopathic VA and more than 70-80% of idiopathic VTs or premature ventricular contractions (PVCs) originate from the right ventricular (RV) OT. Idiopathic OT arrhythmias are thought to be caused by adenosine-sensitive, cyclic adenosine monophosphate (cAMP) mediated triggered activity and, in general, manifest at a relatively early age. Usually they present as salvos of paroxysmal ventricular ectopic beats and are rarely life-threatening. When highly symptomatic and refractory to antiarrhythmic therapy or causative for ventricular dysfunction, ablation is a recommended treatment with a high success rate and a low risk of complications.

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".

Thermal mapping of right ventricular outflow tract tachycardia

BACKGROUND

Acute and long-term success of catheter ablation of right ventricular outflow tract tachycardia (RVOT VT) may be limited by the inability to reproduce the arrhythmia at the time of activation (AM) and pace mapping (PM). We have observed early initiation of the clinical VT when subtherapeutic radiofrequency (RF) energy was applied to the target area (TA), defined as a 2-cm(2) area around a pace match. We describe a novel approach using thermal mapping (TM) to guide the ablation of RVOT VT.

METHODS

Thirteen patients (10 female, mean age 46.2 +/- 13.7 years) with symptomatic VT of left bundle branch block (LBBB) inferior axis morphology and no structural heart disease underwent standard electrophysiologic evaluation with PM (n = 13), AM (n = 13), and 3D noncontact mapping (n = 4). Thermal mapping was performed after standard techniques failed to induce stable sustained VT for mapping in all 13 patients: RF was applied for 5-10 seconds in the TA to achieve a tip temperature of 45-50 degrees C. At sites where morphologically consistent with the clinical VT was induced, RF was applied at target temperature between 50 and 60 degrees C for 30-60 seconds. TM was repeated before and after intravenous Isoproterenol infusion until no further VT could be induced by low temperature application.

RESULTS

Noninducibility was achieved in all 13 patients. During a mean follow-up of 29 months (9-69 months), all patients remain arrhythmia-free, off antiarrhythmic medications.

CONCLUSION

Thermal mapping is a safe and effective adjunctive technique for the mapping and ablation of RVOT VT when sustained tolerated clinical VT cannot be induced.

Idiopathic Ventricular Tachycardia: Diagnosis and Management

Idiopathic ventricular tachycardia (VT) is an uncommon form of VT that is seen in patients without structural heart disease. It is commonly seen in young patients and usually has a benign course. Recent studies have delineated the mechanisms and anatomical locations of this form of VT. Recognition of various forms of idiopathic VT based on characteristic QRS morphology from the 12-lead electrocardiogram (ECG) has important prognostic and therapeutic implications. The understanding of the mechanisms of idiopathic VT has led to the use of specific antiarrhythmic drugs targeting particular arrhythmias. Recent technological advances in the field of mapping and catheter ablation have led to a suitable alternative to drug therapy with a very high cure rate. This review describes the clinical features, ECG recognition, and management of idiopathic monomorphic VT.

Magnetic Resonance Imaging Abnormalities in Right Ventricular Outflow Tract Tachycardia and the Prediction of Radiofrequency Ablation Outcome

BACKGROUND

Recent reports have shown abnormalities on cardiac magnetic resonance imaging (MRI) in patients with right ventricular outflow tract (RVOT) tachycardia.

OBJECTIVES

OBJECTIVES of this study were to demonstrate abnormalities on MRI and signal-averaged ECG (SAECG) in patients with RVOT tachycardia and their correlation with the outcome of radiofrequency (RF) ablation.

METHODS

We studied 41 patients with symptomatic RVOT tachycardia and 15 controls. SAECG and cardiac MRI were performed on every subject. An evaluation of structural abnormality, chamber size, function, and wall motion abnormality of the left and right ventricle was performed by MRI. Focal wall thinning was evaluated by the black blood technique and fatty infiltration was evaluated by the T1 image with and without fat suppression.

RESULTS

MRI abnormalities were demonstrated in 24 (58.5%) patients with RVOT tachycardia. The abnormalities included localized wall bulging in 22 (53.7%), focal wall thinning in 10 (24.4%), and fatty replacement in 9 (22%) patients. MRI abnormality was found in only one patient in the control group (P < 0.001). Late potentials from SAECG were demonstrated in six (10.7%) patients but none in the controls (P = 0.117). Among 29 patients who underwent RF ablation, 3 patients had a failed procedure and 3 having arrhythmia recurrence needed repeated ablation. MRI abnormalities and late potentials were associated with an unfavorable outcome of RF ablation.

CONCLUSIONS

MRI abnormalities were frequently found in patients with RVOT tachycardia. MRI abnormalities and late potentials can predict outcomes of RF ablation.

Idiopathic premature ventricular contractions arising from the pulmonary artery: importance of mapping in the pulmonary artery in left bundle branch block-shaped ventricular arrhythmias

A patient underwent radiofrequency (RF) catheter ablation of symptomatic idiopathic ventricular contractions (PVCs). RF energy applications at 2 sites in the right ventricular outflow tract (RVOT), where both the earliest ventricular activation and near-perfect pace mapping were obtained, did not abolish the PVC but resulted in changes in the QRS morphology of the PVC. Complete elimination of the PVC was achieved with RF energy application at a site within the pulmonary artery 13 mm above the pulmonary valve, which was greater than 20 mm away from the failed ablation sites within the RVOT.

Ablation of Idiopathic Right Ventricular Outflow Tract Tachycardia: Current Perspectives

Ventricular tachycardia (VT) arising from the right ventricular outflow tract (RVOT) in the absence of overt structural heart disease is a common entity. Exclusion of occult structural disease such as arrhythmogenic right ventricular cardiomyopathy is critical as this diagnosis impacts both ablation outcomes and long-term prognosis. VT is most commonly due to triggered activity. Induction of the target arrhythmia in the laboratory is often problematic, and is frequently facilitated by catecholamine infusion. Recent data indicate that high-density three-dimensional activation mapping facilitates identification of target sites for ablation, and that the spatial resolution of pacemapping may be more limited than previously recognized. A standard 12-lead electrocardiogram is useful in providing an initial approximation of the site of origin within the outflow tract, and may contain subtle clues to potentially confounding foci on the left ventricular endocardial or epicardial surface. When sufficient arrhythmia is present to permit mapping, successful ablation can be expected in 90-95% of patients, with a recurrence risk of approximately 5%. In experienced centers, major complications are <or=1% and outcomes should approach those obtained for the common forms of supraventricular tachycardia.

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.

Idiopathic ventricular tachycardia

Most ventricular tachycardias encountered in clinical practice occur in patients who have structural heart disease. Idiopathic ventricular tachycardia refers to those arrhythmias that occur in patients without structural heart disease, metabolic/electrolyte abnormalities, or the long QT syndrome. Three commonly recognized forms of idiopathic ventricular tachycardia include: (a) ventricular tachycardia associated with mitral valve prolapse, (b) ventricular tachycardia originating from the right ventricular outflow tract, and (c) ventricular tachycardia originating from the left ventricle. Recently, a fourth type of idiopathic ventricular tachycardia, termed the Brugada syndrome, has been identified as responsible for some cases of cardiac arrest in persons without apparent structural heart disease. Each form of ventricular tachycardia may be considered a discrete syndrome based on its electrocardiographic characteristics, mechanisms, responses to pharmacologic intervention, and prognosis (good in most cases). Ventricular tachycardias range from the common to the exotic, but all represent syndromes with which the internist and general cardiologist should be familiar.