Combined analysis of unipolar and bipolar voltage mapping identifies recurrences after unmappable scar-related ventricular tachycardia ablation

Intramural needle ablation or repeated standard ablation in patients referred for repeat ablation of scar-related ventricular tachycardia

INTRODUCTION

When ventricular tachycardia (VT) recurs after standard RF ablation (sRFA) some patients benefit from repeat sRFA, whereas others warrant advanced methods such as intramural needle ablation (INA). Our objectives are to assess the utility of repeat sRFA and to clarify the benefit of INA when repeat sRFA fails in patients with VT due to structural heart disease.

METHODS

In consecutive patients who were prospectively enrolled in a study for INA for recurrent sustained monomorphic VT despite sRFA, repeat sRFA was considered first. INA was performed during the same procedure if repeat sRFA failed or no targets for sRFA were identified.

RESULTS

Of 85 patients enrolled, acute success with repeat sRFA was achieved in 30 patients (35%), and during the 6-month follow-up, 87% (20/23) were free of VT hospitalization, 78% were free of any VT, and 7 were lost to follow-up. INA was performed in 55 patients (65%) after sRFA failed, or no endocardial targets were found abolished or modified inducible VT in 35/55 patients (64%). During follow-up, 72% (39/54) were free of VT hospitalization, 41% were free of any VT, and 1 was lost to follow-up. Overall, 59 out of 77 (77%) patients were free of hospitalization and 52% were free of any VT. Septal-origin VTs were more likely to need INA, whereas RV and papillary muscle VTs were less likely to require INA.

CONCLUSIONS

Repeat sRFA was beneficial in 23% (18/77) of patients with recurrent sustained VT who were referred for INA. The availability of INA increased favorable outcomes to 52%.

Epicardial ablation of ventricular tachycardia in ischemic cardiomyopathy: A review and local experience

Myocardial scar in ischemic cardiomyopathy is predominantly endocardial, however, between 5% and 15% of these patients have an arrhythmogenic epicardial substrate. Percutaneous epicardial ablation should be considered in patients with ICM and VT especially if they failed an endocardial ablation. Simultaneous epicardial and endocardial ablation of VT in ICM may reduce short- and medium-term VT recurrence compared with an endocardial only approach. Cardiac imaging could be used to help guide patient selection for a combined epi-endo approach. Complications related to epicardial access can happen in up to 7% of patients. Epicardial ablation in these patients should be referred to experienced tertiary centers. We review the literature and share interesting cases.

Correlation of spatial patterns of endocardial pace mapping to underlying scar topography in patients with scar-related ventricular tachycardia

INTRODUCTION

Endocardial pace mapping (PM) can identify conducting channels for ventricular tachycardia (VT) circuits in patients with structural heart disease (SHD). Recent findings show the temporal and spatial pattern of PM may aid identification of the surface harboring VT isthmii. The specific correlation of PM patterns to scar topography has not been examined.

OBJECTIVE

To correlate the pattern of endocardial PMs to underlying scar topography in SHD patients with VT.

METHODS

Data from patients undergoing VT ablation from August 2018 to February 2022 were reviewed.

RESULTS

Sixty-three patients with SHD-related VT (mean age 65 ± 14 years) with 83 endocardial PM correlation maps were analysed. Two main correlation patterns were identified, an "abrupt-change correlation pattern (AC-pattern)" and "centrifugal-attenuation correlation pattern (CA-pattern)." AC-pattern had lower scar ratio (unipolar/bipolar % scar area; 1.1 vs. 1.5, p < .001), had longer maximal stimulus-QRS intervals (97.5 vs. 68 ms, p = .002), and higher likelihood of endocardial dominant scar (11/21 [52%] vs. 3/38 [8%], p < .001) than CA-pattern seen on intracardiac echocardiography (ICE). In contrast, CA-pattern was more likely to have epicardial dominant scar or mid-intramural scar on ICE (epicardial dominant scar; CA-pattern: 12/38 [32%] vs. AC-pattern: 1/21 [5%], p = .02, mid-intramural scar; CA-pattern: 15/38 [39%] vs. AC-pattern: 1/21 [5%], p = .005).

CONCLUSIONS

The spatial pattern of endocardial PM in SHD-related VT directly correlates with scar topography. AC-pattern is associated with endocardial dominant scar on ICE with lower scar ratio and longer stimulus-QRS intervals, whereas CA-pattern is strongly associated with epicardial dominant or mid-intramural scar with higher scar ratio and shorter stimulus-QRS intervals.

Comparison of the arrhythmogenic substrate for ventricular tachycardia in patients with ischemic vs non-ischemic cardiomyopathy - insights from high-density, multi-electrode catheter mapping

PURPOSE

The purpose of this study was to compare the differences of arrhythmogenic substrate using high-density mapping in ventricular tachycardia (VT) patients with ischemic (ICM) vs non-ischemic cardiomyopathy (NICM).

METHODS

Data from patients presenting for VT ablation from December 2016 to December 2020 at Westmead Hospital were reviewed.

RESULTS

Sixty consecutive patients with structural heart disease (ICM 57%, NICM 43%, mean age 66 years) having catheter ablation of scar-related VT with pre-dominant left ventricular involvement were included. ICM was associated with larger proportion of dense scar area (bipolar; 19 [12-29]% vs 6 [3-10]%, P < 0.001, unipolar; 20 [12-32]% vs 11 [7-19]%, P = 0.01) compared with NICM. However, the scar ratio (unipolar dense scar [%]/bipolar dense scar [%]) was significantly higher in NICM patients (1.2 [0.8-1.7] vs 1.7 [1.3-2.3], P = 0.003). Larger scar area in ICM was paralleled by higher proportion of complex electrograms (6 [2-13] % vs 3 [1-5] %, P = 0.01), longer and wider voltage based conducting channels, higher incidence of late potential-based conducting channels, longer VT cycle-length (399 ± 80 ms vs 359 ± 68 ms, P = 0.04) and greater maximal stimulation-QRS interval among sites with good pace-map correlation (75 [51-99]ms vs 48 [31-73]ms, P = 0.02). Ventricular arrhythmia (VA) storm was more highly prevalent in ICM than NICM (50% vs 23%, P = 0.03). During the follow-up period, NICM had a significantly higher cumulative incidence for the VA recurrence than ICM (P = 0.03).

CONCLUSIONS

High-density multi-electrode catheter mapping of left ventricular arrhythmogenic substrate of NICM tends to show smaller dense scar area and higher scar ratio, compared with ICM, suggestive the extent of epicardial/intramural substrate, with paucity of substrate targets for ablation, which results in the worse outcomes with ablation.

Detection of endo-epicardial atrial low-voltage areas using unipolar and omnipolar voltage mapping

Background: Low-voltage areas (LVA) can be located exclusively at either the endocardium or epicardium. This has only been demonstrated for bipolar voltages, but the value of unipolar and omnipolar voltages recorded from either the endocardium and epicardium in predicting LVAs at the opposite layer remains unknown. The goal of this study was therefore to compare simultaneously recorded endo-epicardial unipolar and omnipolar potentials and to determine whether their voltage characteristics are predictive for opposite LVAs.

Methods: Intra-operative simultaneous endo-epicardial mapping (256 electrodes, interelectrode distances 2 mm) was performed during sinus rhythm at the right atrium in 93 patients (67 ± 9 years, 73 male). Cliques of four electrodes (2 × 2 mm) were used to define maximal omnipolar (Vomni,max) and unipolar (Vuni,max) voltages. LVAs were defined as Vomni,max ≤0.5 mV or Vuni,max ≤1.0 mV.

Results: The majority of both unipolar and omnipolar LVAs were located at only the endocardium (74.2% and 82.0% respectively) or epicardium (52.7% and 47.6% respectively). Of the endocardial unipolar LVAs, 25.8% were also located at the opposite layer and 47.3% vice-versa. In omnipolar LVAs, 18.0% of the endocardial LVAs were also located at the epicardium and 52.4% vice-versa. The combination of epicardial Vuni,max and Vomni,max was most accurate in identifying dual-layer LVAs (50.4%).

Conclusion: Unipolar and omnipolar LVAs are frequently located exclusively at either the endocardium or epicardium. Endo-epicardial LVAs are most accurately identified using combined epicardial unipolar and omnipolar voltages. Therefore, a combined endo-epicardial unipolar and omnipolar mapping approach is favoured as it may be more indicative of possible arrhythmogenic substrates.

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.

Identification of Low-Voltage Areas: A Unipolar, Bipolar, and Omnipolar Perspective

Low-voltage areas (LVAs) are commonly considered surrogate markers for an arrhythmogenic substrate underlying tachyarrhythmias. It remains challenging to define a proper threshold to classify LVA, and it is unknown whether unipolar, bipolar, and the recently introduced omnipolar voltage mapping techniques are complementary or contradictory in classifying LVAs. Therefore, this study examined similarities and dissimilarities in unipolar, bipolar, and omnipolar voltage mapping and explored the relation between various types of voltages and conduction velocity (CV).

Cardiac sympathetic denervation in patients with nonischemic cardiomyopathy and refractory ventricular arrhythmias: a single-center experience

INTRODUCTION

Cardiac sympathetic denervation (CSD) is an effective therapy for selected patients with drug refractory ventricular arrhythmias (VA). Data about the role of CSD in patients with structural heart disease and VAs are sparse. We herein present our experience of CSD in patients with nonischemic cardiomyopathy and VAs despite prior ablation procedure and/or antiarrhythmic drug (AAD) therapy.

METHODS

A total of ten patients (mean age 61.6 ± 19.6, mean LVEF 29.5 ± 12.1%) with nonischemic dilated cardiomyopathy (NICM) (n = 9) and hypertrophic cardiomyopathy (HCM) (n = 1) underwent CSD (left sided in six and bilateral in four patients) due to refractory VA despite multiple AADs (mean number of AADs was 1.6 ± 0.7) and prior VT ablation (mean number of procedures per patient was 1.5 ± 1.3).

RESULTS

Mean follow-up was 10.1 ± 6.9 months. The median number of VA and ICD shocks decreased significantly from 9.0 and 2.5 episodes 6 months prior to CSD to 0 and 0 episodes within 6 months after CSD (p = 0.012 and p = 0.011). Five patients remained free from sustained VA recurrences. Two patients experienced single ICD shock due to a polymorphic VT (triggered by severe hypokalemia in one patient) and one patient a single shock due to monomorphic VT. One patient had five episodes of slow VT under amiodarone therapy (three of them terminated by antitachycardia pacing) and underwent endo- epicardial re-ablation. Two patients died 1 month after CSD. One of them due to electrical storm and cardiogenic shock and the second one due to refractory cardiogenic shock, without recurrence of VAs though. No major complications of CSD occurred. No patient suffered from Horner syndrome.

CONCLUSION

In this study, CSD was effective for treatment of VAs in patients with structural heart disease refractory to antiarrhythmic drugs and catheter ablation. Further larger studies are required to confirm these findings.

Prognostic value role of radiofrequency lesion size by cardiac magnetic resonance imaging on outcomes of ablation in patients with ischemic scar-related ventricular tachycardia: A single center pilot study

Inadequate ablation lesion formation may be responsible for post-ablation ventricular tachycardia (VT) recurrences.We aimed to evaluate whether visualisation of radiofrequency (RF) lesion size by cardiac magnetic resonance imaging (CMR) has any role in predicting adequacy of lesion and in estimating outcome.Retrospective pilot studyNine consecutive patients (8 male, age 60 ± 13 years) underwent ablation for sustained VT because of ischemic scar were evaluated for pre- and post-procedure scar tissue by CMR to characterize ablation lesions. Microvascular obstruction (MVO) surrounded by late gadolinium enhancement was defined as irreversible RF lesion. All patients were followed for at least 6 months for recurrences.Five of the patients had previous inferior myocardial infarction (MI), whereas remaining 4 had anterior MI. Acute procedural success, as defined by termination of the arrhythmia without recurrence in 30 minutes, was attained in all patients. Contrast enhancement and wall motion abnormality in presumed infarction area were confirmed by pre-ablation CMR images. MVO was detected at the reported ablation site in 6/9 patients, all arrhythmia- and symptom-free at median 24 months (range 8-38 months) follow-up. In remaining 3 patients who had VT recurrence (clinical VT in 2, sustain VT with a new morphology in 1), MVO was not detected despite achievement of acute procedural success. There was no correlation with pre-ablation scar size and clinical arrhythmia recurrence.CMR is a useful imaging modality to guide ablation procedures by detecting scar tissue. Additionally MVO seen by post-procedural imaging may be related to adequacy of RF ablation lesions and may correlate with clinical outcome.

Frequent Premature Ventricular Contractions and Cardiomyopathy, Chicken and Egg situation

Premature ventricular contractions (PVCs) are usually regarded as benign in the absence of structural heart disease. However, frequent PVCs can lead to depressed LV function, called PVC-induced cardiomyopathy and can be reversible after suppression of PVCs. On the other hand, PVCs can be a part of underlying structural heart disease and may be linked to increased risk of sudden death. In this work, we reviewed the current literature on PVC-induced cardiomyopathy based on a case presentation.

Myocardial voltage ratio in arrhythmogenic right ventricular dysplasia/cardiomyopathy

AIMS

This study aimed to analyze the influence of scar distribution between the endocardium and the epicardium in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C).

METHODS

Electroanatomical mapping data were derived from our ARVD/C registry. Myocardial voltage distribution between the endocardium and the epicardium was analyzed in 28 patients (18 men, 49.9 ± 13.0 years) with previous ventricular tachycardia (VT) ablation and complete right ventricular maps.

RESULTS

During the follow-up period of 28 ± 22 months after ablation, 18 of 28 patients (64.3%) remained free from VT recurrence. In univariate analysis, five variables associated with VT recurrence, i. e., advanced age, right ventricular (RV) myocardial voltage ratio ≥0.58, inducibility of VT after ablation, and longer procedure and fluoroscopy time. In binary logistic regression analysis only RV myocardial voltage ratio ≥0.58 (hazard ratio 11.667, 95% confidence interval 1.487-91.543, p = 0.012) remained associated with an increased risk of VT recurrence.

CONCLUSION

The myocardial voltage ratio (bipolar low voltage area/unipolar low voltage area) as a potential surrogate parameter for scar distribution between the endocardium and the epicardium is significantly associated with the outcome after VT ablation in ARVD/C.

Limitations and Challenges in Mapping Ventricular Tachycardia: New Technologies and Future Directions

Recurrent episodes of ventricular tachycardia in patients with structural heart disease are associated with increased mortality and morbidity, despite the life-saving benefits of implantable cardiac defibrillators. Reducing implantable cardiac defibrillator therapies is important, as recurrent shocks can cause increased myocardial damage and stunning, despite the conversion of ventricular tachycardia/ventricular fibrillation. Catheter ablation has emerged as a potential therapeutic option either for primary or secondary prevention of these arrhythmias, particularly in post-myocardial infarction cases where the substrate is well defined. However, the outcomes of catheter ablation of ventricular tachycardia in structural heart disease remain unsatisfactory in comparison with other electrophysiological procedures. The disappointing efficacy of ventricular tachycardia ablation in structural heart disease is multifactorial. In this review, we discuss the issues surrounding this and examine the limitations of current mapping approaches, as well as newer technologies that might help address them.