Radiofrequency catheter ablation for idiopathic right ventricular tachycardia with special reference to morphological variation and long-term outcome

Unipolar and bipolar electrogram characteristics of recurrent cases of idiopathic ventricular arrhythmias undergoing repeat catheter ablation

Introduction

Activation mapping guided catheter ablation (CA) of ventricular arrhythmias (VAs) is limited in some cases when it is only relied on bipolar electrogram (EGM). We hypothesized that activation mapping with use of combined bipolar and unipolar EGM facilitates to identify the focal origin of VAs and results in reduction of recurrence rate of CA of VAs.

Methods

We analyzed the data of patients undergoing repeat ablations for idiopathic out-flow tract VAs. The EGM of the 1 st and 2 nd ablations were compared for earliest local activation time (LAT), presence of discrete potentials, and polarity reversal, unipolar potential morphology (QS or non-QS), potential amplitude and activation slope.

Results

Thirty-seven patients were included. The Local activation time was significantly earlier in the 2nd ablation as compared to the 1st procedure (36.90 msec vs 31.85 msec, P < 0.01). The incidence of discrete potentials and polarity reversal were similar in both procedures (51% vs 57%, P = 0.8 and 62% in both the occasions, respectively). The unipolar voltage was similar in both occasions (6.94 mV vs 7.22 mV in repeat ablations, P = 0.7). The recurrence rate (5.7%) was significantly lower with routine use of combined unipolar and bipolar EGMs, as compared to the use of bipolar EGM alone (16.7%)

Conclusions

Use of both bipolar and unipolar electrograms helps in better delineation of the sites of earliest activation for effective ablation of VAs. Use of unipolar electrograms in addition to bipolar electrograms is associated with lower long term recurrence rate.

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In patients undergoing redo ablations for idiopathic OTVAs, a slow-rapid initial QS morphology with its earlier timing prior to onset of QRS on unipolar EGM facilitate identification of early activation sites and improves success of CA.

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Bipolar EGM chracteristics like polarity reversal and presence of discrete potentials have no additive efficacy in redo CA cases.

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A slow-rapid initial QS morphology with its earlier timing to QRS onset may improve the success of CA in idiopathic OTVAs.

Electrocardiographic recognition of benign and malignant right ventricular arrhythmias

Ventricular arrhythmias (VAs) can originate from different anatomical locations of the right ventricle. Ventricular arrhythmias originating from right ventricle have unique electrocardiographic (ECG) characteristics that can be utilized to localize the origin of the arrhythmia. This is crucial in pre-procedural planning particularly for ablation treatments. Moreover, non-ischaemic structural heart diseases, such as infiltrative and congenital heart diseases, are associated with the VAs that exhibit particular ECG findings. This article comprehensively reviews discriminatory ECG characteristics of VAs in the right ventricle with and without structural right ventricular diseases.

Predictive value of unipolar and bipolar electrograms in idiopathic outflow tract ventricular arrhythmia mapping and ablation

INTRODUCTION

Radiofrequency catheter ablation is an effective therapy for focal idiopathic outflow tract ventricular arrhythmia (OTVA). However, visual inspection of the unipolar electrogram (EGM) QS morphology is subjective with a poor specificity for predicting successful ablation sites. This study aims to evaluate the predictive value of unipolar and bipolar EGMs in OTVA mapping and ablation.

METHODS AND RESULTS

Twenty-two patients scheduled for idiopathic OTVA ablation were prospectively enrolled. During the procedure, unipolar and bipolar EGMs were recorded simultaneously and visually inspected by the operator to identify their values for predicting arrhythmogenic sites. Quantitative features of the unipolar EGM including the ratio of amplitude of the first positive peak versus the nadir (R-ratio), the maximum descending slope (MaxSlope), and the time interval between the initial deflection point to the MaxSlope (D-Max) were calculated for each target site in offline analysis. EGMs from 100 sites were collected in 20 patients and analyzed. The bipolar reverse polarity characteristic was not as practical for identifying successful ablation site as the unipolar QS characteristic. Successful ablation sites demonstrated smaller R-ratio and shorter D-Max than unsuccessful sites, but no significant difference in MaxSlope. A unipolar EGM-derived quantitative criterion provided significantly better specificity (0.70) than visual inspection (0.37) without compromising on the sensitivity (0.83 vs. 0.89).

CONCLUSION

The bipolar reverse polarity characteristic was not a practical method for identifying target in idiopathic OTVA ablation. The unipolar EGM-derived quantitative criteria have better predictive performance than visual inspection of the QS characteristic and are likely to reduce unnecessary ablation sites.

Noncontact mapping to guide ablation of right ventricular outflow tract arrhythmias

BACKGROUND

There is limited data on outcomes after noncontact mapping (NCM)-guided right ventricular outflow tract (RVOT) ventricular arrhythmia (VA) ablation.

OBJECTIVES

To assess outcomes of NCM-guided RVOT VA ablation in a large cohort with extended follow-up, to determine optimal ablation site, and to analyze limitations of conventional mapping techniques.

METHODS

In consecutive patients undergoing RVOT VA ablation, 2 sites of early activation--earliest activation (EA) and breakout (BO) sites--were identified on NCM maps. Pace mapping and activation mapping were performed at both sites. The area of depolarized myocardium during the first 10 ms of spontaneous VA and pacing was measured. The initial site of ablation was randomized to either EA or BO sites, with crossover to the alternate site if ablation was not successful.

RESULTS

In 136 patients, prematurity of local activation and pace maps were similar at EA and BO sites. More myocardium was depolarized 10 ms after pacing than during spontaneous VA (12.9 ± 7.8 cm(2) vs 5.3 ± 3.9 cm(2); P < .01). Clinical success was more likely achieved when initial ablation was directed toward the EA site (P < .05). A wider EA-BO separation was associated with acute procedural failure (P < .01). With a follow-up of 36.2 ± 17.5 months, the success rate after a single procedure without antiarrhythmic agents was 86.8%.

CONCLUSIONS

NCM-guided RVOT VA ablation is highly effective, and clinical success is best achieved by ablating the EA site. Broad regions of early activation are associated with worsened clinical outcomes. Spatial resolution of activation and pace mapping is limited by rapid electrical propagation in the RVOT.

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.

Single-centre experience with an 8-mm tip catheter for radiofrequency catheter ablation of outflow tract ventricular ectopic beats

BACKGROUND

Radiofrequency ablation (RFA) of outflow tract ventricular ectopic beats (OTVEBs) can be performed using a 4-mm or externally-cooled tip RFA catheter, but no data are available concerning the safety and efficacy of a large-tip (8-mm) catheter.

AIMS

To evaluate the feasibility of using an 8-mm tip catheter in patients with OTVEBs.

METHODS

In this prospective cohort study, the 8-mm tip catheter was tested in patients who were referred to our centre for RFA of symptomatic OTVEBs.

RESULTS

The mean age of the 16 patients recruited between September 2008 and March 2010 was 53±18 years and 56.3% were male. Mean left ventricular ejection fraction was 62±9%, mean ventricular ectopic beat width was 144±21 ms, and all patients had left bundle branch block. Fourteen patients had inferior axis QRS morphology and two had superior. The main symptoms were palpitations and pre-syncope. RFA parameters were: procedure time 94±35 min; duration of application 11±10 min; impedance 81±12 Ω; temperature 50±5 °C; and power 46±17 W. RFA succeeded in 15 over 16 patients (93.8%); and recurrence was seen in one patient after a mean follow-up time of 11±6 months. No complications were noted.

CONCLUSIONS

This preliminary study suggests that an 8-mm tip catheter may represent an alternative for RFA in patients with OTVEBs in whom a 4-mm tip was not successful. Larger randomized studies are therefore warranted.

Reversed polarity of bipolar electrograms for predicting a successful ablation site in focal idiopathic right ventricular outflow tract arrhythmias

BACKGROUND

Radiofrequency catheter ablation (RFCA) for idiopathic right ventricular outflow tract (RVOT) arrhythmias is typically guided by local activation time (LAT) mapping and unipolar electrogram morphology (QS configuration). However, LAT mapping is limited by the large variation among patients, and the area demonstrating a QS configuration of the unipolar electrogram may be larger than the focal source. Reversed polarity has been proposed as a criterion for guiding RFCA.

OBJECTIVE

The purpose of this study was to investigate the value of reversed polarity of adjacent bipolar electrograms for predicting a successful ablation site in idiopathic RVOT arrhythmias.

METHODS

Twenty-five consecutive patients (12 men [48%], age 43 ± 15 years) undergoing RFCA for RVOT arrhythmia were studied. Electrograms of ablation sites and of points within a 15-mm radius to the successful site were evaluated for LAT, unipolar electrogram morphology, and the presence of reversed polarity of adjacent bipolar electrograms. Electrogram characteristics of successful ablation sites were compared to those of nonsuccessful ablation sites. The spatial distribution of each electrogram characteristic was studied.

RESULTS

Successful ablation sites more often demonstrated reversed polarity and had an earlier LAT than nonsuccessful sites. A wide spatial distribution was observed for unipolar electrograms with a QS configuration around the successful ablation site. Mapping based on LAT and reversed polarity had a higher predictive value for a successful ablation site than mapping based on LAT and QS configuration.

CONCLUSION

The presence of reversed polarity has a high predictive value for successful ablation sites in focal idiopathic RVOT arrhythmias and is likely to reduce the number of RFCA applications.

Evaluation of cardiac arrhythmia among athletes

Due to the growing awareness of exercise-related arrhythmias and improved sensitivity of diagnostic modalities, physicians are increasingly faced with choices that may have life-changing impact for the athlete. This article surveys recent research and expert opinion addressing benign and pathogenic cardiac changes underlying arrhythmias in athletes.

Ventricular tachycardia and sudden cardiac death

Ventricular tachycardia (VT), which most commonly occurs in patients with structural heart disease, can be associated with an increased risk of sudden death. The most common cause of ventricular fibrillation is acute coronary ischemia, whereas a myocardial scar from prior infarct is the most common cause of sustained monomorphic VT in patients with structural heart disease. More benign forms of idiopathic VT can also occur in the absence of structural heart disease. Treatment of VT involves both emergent management and prevention of recurrence with medical and device therapy. Appropriately selected patients who have experienced VT or those who are at risk of VT may be candidates for an implantable cardioverter-defibrillator. The left ventricular ejection fraction is most frequently used to stratify patients with either ischemic or nonischemic cardiomyopathy who are at risk of sudden death and may be candidates for a prophylactic defibrillator. Catheter ablation may also be an option for appropriately selected patients with many forms of VT. This article discusses the etiologies and management of VT and its association with sudden death.

Ventricular tachycardia and sudden cardiac death

Ventricular tachycardia (VT), which most commonly occurs in patients with structural heart disease, can be associated with an increased risk of sudden death. The most common cause of ventricular fibrillation is acute coronary ischemia, whereas a myocardial scar from prior infarct is the most common cause of sustained monomorphic VT in patients with structural heart disease. More benign forms of idiopathic VT can also occur in the absence of structural heart disease. Treatment of VT involves both emergent management and prevention of recurrence with medical and device therapy. Appropriately selected patients who have experienced VT or those who are at risk of VT may be candidates for an implantable cardioverter-defibrillator. The left ventricular ejection fraction is most frequently used to stratify patients with either ischemic or nonischemic cardiomyopathy who are at risk of sudden death and may be candidates for a prophylactic defibrillator. Catheter ablation may also be an option for appropriately selected patients with many forms of VT. This article discusses the etiologies and management of VT and its association with sudden death.

Management of ventricular tachycardia in the absence of structural heart disease

Ventricular tachycardia most often arises from the ventricular outflow tracts in patients with apparently structurally normal hearts, and is often termed idiopathic ventricular tachycardia. These tachycardias are characterized by a left bundle branch block, inferior axis QRS morphology, and a unique electropharmacologic profile. The choice of treatment is dictated by the severity of symptoms, and ranges from observation for asymptomatic patients, to antiarrhythmic agents for those who are mildly to moderately symptomatic (eg, palpitations), to catheter-based ablation for those with more troubling symptoms or those who develop tachycardia-mediated cardiomyopathy. Antiarrhythmic therapy can be effective for arrhythmia suppression, and radiofrequency ablation has a high success rate (> 90%) with few procedural complications. In general, ventricular outflow tract tachycardia has a favorable prognosis. Exclusion of arrhythmogenic right ventricular dysplasia/cardiomyopathy is important due to significant disparities in prognosis and treatment.

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.

Spatial Resolution of Pacemapping and Activation Mapping in Patients with Idiopathic Right Ventricular Outflow Tract Tachycardia

BACKGROUND

The purpose of this study was to compare the spatial resolution of activation mapping and pacemapping in patients undergoing ablation of idiopathic ventricular tachycardia (VT) arising from the right ventricular outflow tract (RVOT). A direct comparison of the two techniques has not been undertaken.

METHODS AND RESULTS

Electroanatomical activation maps of the RVOT were obtained during VT in 15 patients. Pacemaps were obtained from multiple sites, tagged on the activation map, and scored according the degree of concordance between the paced QRS configuration and that of VT. The site of successful ablation was considered the VT site of origin. Initial endocardial activation away from the site of origin was rapid; the mean area of myocardium activated within the first 10 msec (early activation area, EAA) was 3.0 +/- 1.6 cm(2) (range: 1.3-6.4 cm(2)). Best pacemap scores were always obtained adjacent to the site of origin. Pacemap concordance, and the probability of an exact pacemap match significantly decreased with increasing distance of the pacing site from the site of origin (P < 0.01). All patients had more than one pacing site yielding a best pacemap score. The greatest distance between such sites in an individual patient ranged from 11 to 26 mm (mean: 18 +/- 5 mm), and was strongly correlated with the size of the EAA (r = 0.77, P < 0.001).

CONCLUSIONS

Pacemapping and activation mapping provide similar localizing information. The spatial resolution of each technique is modest, varies between patients, and may be optimized by three-dimensional data display.

Electrocardiographic predictors of failure and recurrence in patients with idiopathic right ventricular outflow tract tachycardia and ectopy who underwent radiofrequency catheter ablation

This study reports new electrocardiographic (ECG) predictors of radiofrequency catheter ablation failure and recurrence in idiopathic right ventricular outflow tract (RVOT) ventricular tachycardia (VT) or ectopy based on 91 consecutive patients. Procedural success and failure rates were 85% (77/91) and 15% (14/91), respectively. Twenty three percent (18/77) had recurrence during the follow-up period of 1 to 120 months (mean 56 +/- 31 months). Baseline RVOT VT/ectopy on 12-lead ECG taken prior to ablation from 91 patients were retrospectively analyzed. Ablation performed with RVOT ectopy (isolated ectopies, bigeminy, trigeminy, or couplets) as template arrhythmia was more likely to fail (30% vs. 8%, P =.02) as opposed to RVOT VT (sustained or nonsustained). VT/ectopy-QRS morphology variation was more observed in failed ablations (36% vs. 7%, P =.001). Significantly wider mean VT/ectopy QRS in leads I, II, AVR, V2, V3, V5, and V6 were noted in failed ablation group. Mean R wave amplitude reached statistical significance only in lead II (22.0 +/- 5.1 mV for failed vs. 17.8 +/- 5.2 mV for successful outcomes; P =.009). QRS morphologic variation (47% vs. 16%; P =.009) was the only statistically significant ECG to be more common in patients with arrhythmia recurrence. In conclusion, ablation with ectopy over VT as template arrhythmia, presence of QRS morphologic variation, wider mean QRS width, and taller mean R-wave amplitude in lead II were identified ECG predictors of failed RVOT VT/Ectopy ablation. The only ECG predictor of recurrence was the presence of RVOT VT or ectopy QRS morphologic variation.