Limitations of Unipolar Signals in Guiding Successful Outflow Tract Premature Ventricular Contraction Ablation

Catheter Ablation of Parahisian Premature Ventricular Complexes From the Right Sinus of Valsalva

BACKGROUND

Cather ablation of parahisian premature ventricular complexes (PVCs) often requires ablation in multiple cardiac chambers, including the sinuses of Valsalva (SoV). The safety and efficacy of ablation within the right SoV to target parahisian arrhythmias has not been widely reported.

OBJECTIVE

To report on the demographic and procedural characteristics of patients undergoing catheter ablation of PVCs who underwent ablation in the right SoV, and to examine the impact of late-gadolinium enhanced cardiac magnetic resonance (LGE-CMR) on procedural findings.

METHODS

Consecutive patients undergoing ablation of parahisian PVCs and ablation in the right SoV with preprocedural LGE-CMR were included.

RESULTS

Eleven patients were included in the study population (11 males (100%), median age: 68 ± 7 years, median ejection fraction: 53% ± 7%, PVC burden 23% ± 13%). Intramural LGE-CMR scar was present in all patients and involved the basal anteroseptum/outflow tract in nine patients. Ablation within the right SoV eliminated (n = 9) or suppressed (n = 2) PVCs in all patients. The successful SoV site displayed the absolute earliest presystolic activation time or matching pacemaps in only 44% and 55% of patients, respectfully. Transient heart block during right SoV ablation occurred in 1/11(9%) patients. The post procedure PVC burden decreased from 23% ± 13% to 7% ± 6%, procedural success was attained in 10/11(91%) of patients.

CONCLUSIONS

Parahisian PVCs ablated from the right SoV are often intramural, may require ablation in multiple chambers, and colocalize with intramural LGE-CMR scar. Traditional EGM markers of successful ablation sites were less frequently seen at successful site of SoV ablation, long term success was achieved in 91% of patients.

Predictability of indicators in local activation time mapping of ablation success for premature ventricular contractions

Introduction

Differences in predictability of ablation success for premature ventricular contractions (PVCs) between earliest isochronal map area (EIA), local activation time (LAT) differences on unipolar and bipolar electrograms (⊿LATBi-Uni), LAT prematurity on bipolar electrograms (LATBi), and unipolar morphology of QS or Q pattern remain unclear. We verified multiple statistical predictabilities of those indicators of ablation success on mapped cardiac surface.

Methods

Thirty-five patients with multiple PVCs underwent catheter ablation after LAT mapping using multipolar mapping catheters with unipolar-based annotation. Patients were divided into success and failure groups based on ablation success on mapped cardiac surfaces. Discrimination ability, reclassification table, calibration plots, and decision curve analysis of 10 ms EIA (EIA10ms), ⊿LATBi-Uni, and LATBi were validated. Unipolar morphology was compared between success and failure groups.

Results

Right ventricular outflow tract, aortic cusp, and left ventricle were mapped in 17, 10, and 8 patients, respectively. In 14/35 (40%) patients, successful ablation was performed on mapped cardiac surfaces. Area under the curve of receiver-operating characteristic curve of EIA10ms, ⊿LATBi-Uni, and LATBi were 0.874, 0.801, and 0.650, respectively (EIA10ms vs. LATBi, p =.014; ⊿LATBi-Uni vs. LATBi, p =.278; EIA10ms vs. ⊿LATBi-Uni, p =.464). EIA10ms and ⊿LATBi-Uni demonstrated better predictability, calibration, and clinical utility on reclassification table, calibration plots, and decision curve analysis than LATBi. Unipolar morphology of QS or Q pattern did not correlate with ablation success (p =.518).

Conclusion

EIA10ms and ⊿LATBi-Uni more accurately predict ablation success for PVCs on mapped cardiac surfaces than LATBi and unipolar morphology.

Limitation of Unipolar Electrograms in Guiding Successful RFCA of Idiopathic Ventricular Arrhythmias Associated With Discrete Pre-Potential

OBJECTIVES

Activation mapping for idiopathic ventricular arrhythmias (IVAs) typically relies on identifying the earliest bipolar electrograms and unipolar electrograms characterized by an initial QS morphology preceding the intrinsic deflection. However, the utility of unipolar electrogram morphology, particularly when associated with discrete pre-potentials, in guiding IVA mapping is not well understood.

METHODS

We retrospectively analyzed 537 patients who underwent successful radiofrequency catheter ablation (RFCA) for IVAs between March 2016 and August 2023. Among them, 23 patients (4.3%) exhibited discrete bipolar pre-potentials with an isoelectric line between the end of the discrete pre-potential and the onset of the QRS complex during IVAs at the successful RFCA site. These cases were included in this study.

RESULTS

The time interval from the onset of the discrete pre-potential to the onset of the QRS complex was 66.4 ± 18.3 ms. The duration of the isoelectric line between the end of the discrete pre-potential and the onset of the QRS complex was 36.9 ± 13.6 ms. Unipolar electrograms associated with discrete pre-potentials exhibited an initial negative morphology in only 13 out of 23 patients (56.5%). In contrast, initial positive and isoelectric configurations in unipolar electrograms were observed in two patients (8.7%) and eight patients (34.8%), respectively. Perfect pace mapping was obtained in 21 patients (91.3%). RFCA was successful at the earliest site of the pre-potential within 3.5 ± 1.5 s in all 23 patients. During the 2.4 ± 1.2 years follow-up period, only one patient (4.3%) experienced a recurrence of clinical IVAs, with no complications reported during RFCA or follow-up.

CONCLUSIONS

Unipolar electrograms show limited reliability in guiding the identification of IVAs origins compared to bipolar electrograms associated with discrete pre-potentials.

Anatomical approach to suppression of para-Hisian ventricular arrhythmias with changes in QRS morphology after ablation at the earliest activation site

BACKGROUND

The anatomical approach for the management of para-Hisian ventricular arrhythmias (VAs) with QRS morphological changes after catheter ablation (CA) has not been well investigated.

OBJECTIVE

We aimed to evaluate the electrocardiographic and electrophysiological findings and ablation outcomes of para-Hisian VAs with QRS morphological changes after CA.

METHODS

Of the 30 patients who underwent CA for para-Hisian VAs at 4 institutions, 10 (33%) had QRS morphological changes after ablation. All 10 patients underwent an anatomical approach, targeting the site anatomically opposite to the site where the QRS morphology had been changed by ablation. We investigated the safety and efficacy of the anatomical approach.

RESULTS

Of the 10 patients evaluated, the approach was switched from the right ventricular septum to the left ventricular septum/aortic root in 7 (70%) (RL group) whereas 3 (30%) underwent left-to-right switches (LR group). After CA, the precordial transition zone tended to be earlier in the RL group and later in the LR group. In the RL group, successful VA suppression was achieved, despite suboptimal pace map concordance from the left side or a relatively delayed earliest activation time. Of the 10 patients who underwent an anatomical approach, 8 (80%) had procedural success, and ablation was discontinued in 1 (10%) because of the risk of atrioventricular block.

CONCLUSION

The anatomical approach showed promising results regarding safety and efficacy. Therefore, it should be considered when QRS morphological changes are observed during or after CA of para-Hisian VAs.

Left Ventricular Summit Arrhythmias: State-of-the-Art Review of Anatomy, Mapping, and Ablation Strategies

The left ventricular summit (LVS) is the most common site of epicardial arrhythmias. Ablation of LVS arrhythmias continue to pose a challenge to the electrophysiologist because of its complex and intimate anatomical location. In this review, we undertake a detailed examination of the intricate anatomy of the LVS alongside a comprehensive synthesis of mapping and ablation strategies used to treat LVS arrhythmias.

Electrophysiological characteristics and catheter ablation of ventricular arrhythmias arising from the superior septal left ventricle

BACKGROUND AND AIMS

Electrophysiological characteristics and radiofrequency catheter ablation (RFCA) of premature ventricular contractions (PVCs) originating from the superior septal left ventricle (SSLV) have not yet been fully characterized.

METHODS AND RESULTS

This study included 247 patients who underwent RFCA for PVCs arising from the ventricular outflow tract between February 2020 and August 2022. The successful ablation site was on the SSLV in 37 of the 247 patients. In 12 (32.4%) of those 37 patients, a low amplitude and high frequency spiky potential (SP) was recognized. Five patients showed a narrow QRS duration (86.8 ± 4.6 ms), with a discrete SP observed in PVCs and sinus rhythm, which showed an isoelectric line with the ventricular electrogram at the earliest activation site. Seven patients showed a wide QRS duration (131.6 ± 4.5 ms), with SP observed in PVCs without an isoelectric line with the ventricular electrogram. RFCA was successful at the site of the earliest SP in all 12 patients. The time from SP onset at the successful ablation site to the QRS onset (local activation time) was 30 ± 12 ms, which differed significantly from that for the remaining 25 patients withoutSP(22.1 ± 7.1 ms, P < 0.05).

CONCLUSIONS

SPs were recorded in 12 (32.4%) of the 37 patients with PVCs originating from the SSLV. The morphology of the PVCs may show a narrow or wide QRS duration and the target site for successful ablation should be identified by the earliest SP.

Anatomically Based Ablation of Left Ventricular Summit Premature Ventricular Complexes Guided by Intracardiac Echocardiography

Catheter ablation of premature ventricular contractions (PVCs) arising from the left ventricular summit (LVS) presents technical challenges due to the regional anatomy and frequent intramural site of origin (SOO). Intracardiac echocardiography (ICE) and the CARTOSOUND® (Biosense Webster, Diamond Bar, CA, USA) module allow the operator to directly reconstruct and visualize the dimensions and orientation of the LVS live and present it in relation to neighboring structures. We retrospectively reviewed consecutive cases between January 2021 and December 2022 of patients undergoing PVC ablation for a presumed LVS origin. The LVS was reconstructed by creating a three-dimensional representation of the left ventricular septum, using two-dimensional ICE sections. The earliest site in each chamber was tagged on the reconstructed LVS, and the presumed SOO was localized using a geometrical center point from all sites. Ablation was first delivered to the earliest site, except when the presence of coronary branches precluded radiofrequency delivery within the great cardiac vein. Of 20 patients (8 women, 62.4 ± 7.1 years old) with a presumed LVS origin, 12 had PVC recurrence within the monitoring period after the initial ablation for 192.5 ± 37.2 s at the earliest site. Among them, earliest activation was seen at the sinus of Valsalva (SoV), coronary venous system (CVS), and left ventricular endocardium (LVE) in four, six, and two patients, respectively. Using the reconstructed LVS, the anatomically closest site to the SOO was identified in the SoV, CVS, and LVE in four, two, and six cases, respectively. Throughout the study period (14.5 months; range, 9.3-19.7 months), 17 patients (85%) had complete elimination of PVCs as evaluated by 24-h event monitors at the 12-month visit. In 50% of cases, among patients in whom ablation at the earliest signal was unsuccessful, the site of successful ablation did not correlate with the second earliest signal or had no identifiable signal during initial activation mapping. The reconstructed LVS not only guided activation mapping but also identified sites proximal to the center point that had either a late activation signal, a low-amplitude signal, or no signal at all.

Unipolar and bipolar electrograms to predict successful ablation site of premature ventricular contractions originating from the free wall of the tricuspid annulus

INTRODUCTION

This study aimed to identify the characteristics of unipolar and bipolar electrogram (UniEGM and BiEGM) in guiding successful ablation of premature ventricular contractions (PVCs) originating from the free wall of the ventricular aspect of the tricuspid annulus (TA). We hypothesized that the negative concordance pattern (NCP) on the onset of UniEGM and BiEGM, together with the least value of the difference between the earliest BiEGM and UniEGM dV/dTmax, might improve the accuracy of conventional mapping.

METHODS AND RESULTS

Thirty consecutive patients who underwent successful catheter ablation from February 2018 to July 2021 were retrospectively analyzed. The BiEGM and UniEGM for successful ablation sites were compared with those for non-successful ablation sites. Among the 30 patients, 30 successful and 26 nonsuccessful ablation sites were compared. The earliest activation time of the BiEGM (BiEGMoneset-QRS) was 25 ± 6 ms for the successful ablation sites and 21 ± 6 ms for the nonsuccessful ablation sites (p = .47). The value of the difference in the earliest BiEGM and UniEGM dV/dTmax differed between successful and nonsuccessful ablation sites (6.4 ± 3.6 ms vs. 10.4 ± 6.8 ms). NCP was observed at 90.0% and 42.3% of the successful and nonsuccessful ablation sites, respectively. Alignment of NCP and BiEGMonset-UniEGM ≤6 ms was applied as the mapping criterion for successful PVC suppression (73.1% sensitivity and 87.7% specificity). The area under the receiver-operating characteristic curve for this cutoff was 0.85.

CONCLUSION

Mapping based on an NCP at the onset of the BiEGM and UniEGM and the least difference value of the earliest BiEGM and UniEGM dV/dTmax had an excellent predictive value for successful ablation. These strategies may reduce the number of radiofrequency catheter ablation (RFCA) applications for free-wall tricuspid annular PVCs.

Best Practices for the Catheter Ablation of Ventricular Arrhythmias

Techniques for catheter ablation have evolved to effectively treat a range of ventricular arrhythmias. Pre-operative electrocardiographic and cardiac imaging data are very useful in understanding the arrhythmogenic substrate and can guide mapping and ablation. In this review, we focus on best practices for catheter ablation, with emphasis on tailoring ablation strategies, based on the presence or absence of structural heart disease, underlying clinical status, and hemodynamic stability of the ventricular arrhythmia. We discuss steps to make ablation safe and prevent complications, and techniques to improve the efficacy of ablation, including optimal use of electroanatomical mapping algorithms, energy delivery, intracardiac echocardiography, and selective use of mechanical circulatory support.

Intracardiac electrogram characteristics of intramural outflow tract ventricular arrhythmias

BACKGROUND

Annotation of earliest depolarization which depends on maximum dV/dt of unipolar-electrograms and unipolar QS morphology identify site of origin for ventricular premature contractions (VPC). However, identification of unipolar QS morphology has limitations due to low spatial resolution. This study aims to compare electrogram characteristics at successful ablation site in patients with outflow tract (OT) VPC.

METHODS

Local activation time (LAT), duration, and voltage data of each bipolar- and unipolar-electrogram at the successful ablation sites from the right ventricle OT (RVOT) and the left ventricle OT (LVOT) cases were analyzed.

RESULTS

Forty-four of 60 (73%) of patients were ablated from RVOT and in 16/60 (27%) required ablation from both sides. All patients had acute VPC suppression. Bipolar-electrogram-QRS onset was earlier (36.4 ± 14.5 ms vs 26.3 ± 7.4 ms, p = 0.01), duration of bipolar-electrogram was shorter (56.9 ± 18.9 ms vs 78.9 ± 21.8 ms, p = 0.002), and bi-voltage amplitude was higher (3.2 ± 2.3 mV vs 1.4 ± 1.1 mV, p = 0.07) for patients with RVOT-only ablation. Mean bipolar-unipolar-electrogram difference was 4.4 ± 4.5 ms in the RVOT group vs 12.8 ± 4.9 ms in RVOT + LVOT group (p < 0.001). Unipolar QS morphology was recorded in 3.0 ± 3.9 vs 3.6 ± 1.8 cm² in RVOT and RVOT + LVOT group, respectively (p = 0.41). Unipolar-electrogram revealed W pattern in 3/44 of RVOT vs 5/16 of RVOT + LVOT group, respectively (p = 0.01). In 18/60 (30%) of patients, unipolar QS was not identified at successful ablation site.

CONCLUSION

QS in unipolar-electrogram was not a perfect predictor for successful ablation sites. Analysis of bipolar voltage amplitude and duration with bipolar-unipolar-electrogram time difference may identify presence of a deeper source.