Intramural Mapping of Intramural Septal Ventricular Arrhythmias

Relationship of Structural Abnormalities of Papillary Muscles to the Site of Origin of Ventricular Arrhythmias

BACKGROUND

Arrhythmias originating from papillary muscles (PAPs) can be challenging when targeted with catheter ablation. The prevalence and impact of structural abnormalities on PAPs in patients with focal PAP arrhythmias is unknown.

OBJECTIVES

The purpose of this study was to analyze, in a consecutive patient series with focal PAP arrhythmias, the impact of structural abnormalities detected by multimodality imaging.

METHODS

In a series of 43 consecutive patients with focal PAP arrhythmias referred for ablation, the prevalence and location of structural abnormalities on PAPs were assessed with cardiac magnetic resonance imaging, computed tomographic angiography and intracardiac echocardiography (ICE). Sites of origin of ventricular arrhythmias (VAs) were correlated with structural abnormalities.

RESULTS

On PAPs, late gadolinium enhancement (LGE) was present on cardiac magnetic resonance imaging in 19 of 43 patients, calcifications on computed tomography in 2 of 43 and on ICE in 3 of 43 patients, and increased echogenicity on ICE in 39 of 43 patients. A total of 141 focal PAP arrhythmias were identified, and VA target sites were localized adjacent to areas with increased echogenicity on ICE for 59 of 141 (44%) VAs, adjacent to LGE for 35 of 141 (25%) VAs, and adjacent to calcifications for 14 of 141 (10%) VAs. At least one VA target site was localized to areas of structural abnormalities in 32 of 43 (74%) patients.

CONCLUSIONS

Multimodality imaging identifies arrhythmogenic PAPs preprocedurally and in real time during the ablation procedure in most patients. Increased echogenicity, LGE, and calcifications are often seen on PAPs in patients with focal PAP arrhythmias and can indicate the site of origin.

Ventricular arrhythmias in patients with bicuspid aortic valves

INTRODUCTION

Bicuspid aortic valves (BAV) are the most common congenital heart defects and the extent of ventricular arrhythmias (VA) in patients with BAV is unclear. The objective of this study is to describe VAs and late gadolinium enhancement cardiac magnetic resonance imaging (LGE-CMR) in patients with BAV.

METHODS

A total of 19 patients with BAV (18 males, age: 58 ± 13 years) were referred for VA ablation procedures. Ten patients had BAVs at the time of ablation, nine patients had prior aortic valve replacement for a BAV. All but one patient had LGE-CMR and all patients underwent programmed ventricular stimulation at the time of the ablation.

RESULTS

Frequent PVCs were the targeted VAs in 17/19 patients and VT in 2/19 patients. Monomorphic ventricular tachycardia (VT) was inducible in 6 patients. A total of 15 VTs were inducible (2.5 ± 1.0 VTs per patient with a mean cycle length of 322 ± 83 msec). LGE was present in 13 patients. Patients with inducible VT had larger borderzone and core scar compared to non-inducible patients (7.8 ± 2.1 cm3 vs. 2.5 ± 3.1 cm3 and 5.1 ± 2.6 cm3 vs. 1.9 ± 3.0 cm3, p-value < .05 for both). PVCs and VTs were mapped to the periaortic valve area in 12 patients and 4 patients, respectively. The PVC burden was reduced from 27 ± 13 to 3 ± 6 (p < .001) and the ejection fraction improved from 49 ± 13% to 55 ± 9% (p = .005).

CONCLUSIONS

VAs in patients with BAV often originate from the perivalvular area and patients often have LGE and inducible VT. LGE may be due to ventricular remodeling secondary to the presence of BAV and harbors the arrhythmogenic substrate for VT.

Bipolar catheter ablation with dedicated radiofrequency system for highly refractory ventricular arrhythmia-Does the rate of success depend on arrhythmia origin?

INTRODUCTION

Despite rapid technological progress, some arrhythmias are still resistant to standard unipolar ablation. These include arrhythmias arising from the base of the heart, cardiac crux, or epicardium. Bipolar radiofrequency ablation (B-RFA) may be useful in some cases, however, data on the efficacy of this approach in various arrhythmia localizations are scarce. The aim of this study was to assess the efficacy of B-RFA in patients with ventricular arrhythmias originating from various locations, occurring refractory to standard unipolar ablation approaches.

METHODS

An observational, single center study was conducted over a 30-month period. B-RFA were performed using dedicated radio frequency (RF) generator and electroanatomic mapping system.

RESULTS

Twenty-four procedures, in 23 patients with a median (range) of 1 (1-2) previously failed unipolar ablation procedures, were included in the final analysis. There were 12 ablations of ventricular arrhythmias originating from interventricular septum with an acute success rate of 75%, and 12 from left ventricular (LV) summit with an acute success rate of 58%. The midterm success rate (median interquartile range follow-up of 205 days [188-338]) was 66% and 50%, respectively.

CONCLUSIONS

B-RFA is a promising method of catheter ablation for refractory cardiac arrhythmias. A higher success rate was observed in ablation for difficult ventricular arrhythmias originating from interventricular septal region than LV summit.

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.

Septal Substrate Ablation Guided by Delayed Transmural Conduction Times: A Novel Ablation Approach to Target Intramural Substrates

BACKGROUND

Intraprocedural identification of intramural septal substrate for ventricular tachycardia (ISS-VT) in nonischemic cardiomyopathy (NICM) is challenging. Delayed (>40 ms) transmural conduction time (DCT) with right ventricular basal septal pacing has been previously shown to identify ISS-VT.

OBJECTIVES

This study sought to determine whether substrate catheter ablation incorporating areas of DCT may improve acute and long-term outcomes.

METHODS

We included patients with NICM and ISS-VT referred for catheter ablation between 2016 and 2020. ISS-VT was defined by the following: 1) confluent septal areas of low unipolar voltage (<8.3 mV) in the presence of normal or minimal bipolar abnormalities; and 2) presence of abnormal electrograms in the septum. Substrate ablation was guided by the following: 1) activation and/or entrainment mapping for tolerated VT and pace mapping with ablation of abnormal septal electrograms for unmappable VTs (n = 57, Group 1); and 2) empirically extended to target areas of DCT during right ventricular basal septal pacing regardless of their participation in inducible VT(s) but sparing the conduction system when possible (n = 24, Group 2).

RESULTS

There were no significant baseline differences between Groups 1 and 2. Noninducibility of any VT programmed stimulation at the end of ablation was higher in Group 2 compared with Group 1 (80% vs 53%; P = 0.03). At 12-month follow-up, single-procedure VT-free survival was significantly higher (79% vs 46%; P = 0.006) and the time to VT recurrence was longer (mean 10 ± 3 months vs 7 ± 4 months; P = 0.02) in Group 2 compared with Group 1.

CONCLUSIONS

In patients with NICM and ISS-VT, a substrate ablation strategy that incorporates areas of DCT appears to improve freedom from recurrent VT.