Bipolar ablation of ventricular arrhythmias: Step-by-step

Using the QRS-VHis Interval-based Algorithm to Optimize the Ablation Process of Outflow Tract Premature Ventricular Complexes

BACKGROUND

The choice between left- and right-sided ablation for outflow tract premature ventricular complexes (OT-PVCs) during procedures remains a topic of ongoing discussion. In this study we aim to elucidate the value of the QRS-VHis interval in distinguishing between left and right origins in left bundle branch block (LBBB)-type OT-PVCs, thereby optimizing the ablation process.

METHODS

The QRS-VHis interval was measured in consecutive patients with LBBB-type OT-PVCs. The performance of this interval was compared with traditional electrocardiographic (ECG) algorithms and prospectively validated in a cohort from 8 centers. Based on the interval, we developed an algorithm to assess its efficacy in optimizing the ablation process.

RESULTS

A total of 166 patients were enrolled in the development cohort, and 53 patients in the validation cohort. The QRS-VHis interval demonstrated greater accuracy than ECG algorithms among 153 patients with typical endocardial origins (area under the curve = 0.962). At a cutoff of 30 ms, the QRS-VHis interval showed a sensitivity of 71.8% and a specificity of 98.2% for identifying left-sided locations. A flowchart was developed based on the QRS-VHis interval, indicating that a QRS-VHis value of < 30 ms necessitated left-sided ablation with a 94% likelihood, leading to an 88% success rate. Conversely, when the QRS-VHis value was ≥ 30 ms, the likelihood of requiring left-sided ablation dropped to only 16%. The accuracy of the flowchart was validated in the independent cohort.

CONCLUSIONS

The QRS-VHis interval is superior for distinguishing between left and right ventricular outflow tract origins in LBBB-type OT-PVCs and has proven valuable in optimizing the intraprocedural process.

Electrophysiological Phenotype-Genotype Study of Sustained Monomorphic Ventricular Tachycardia in Inherited, High Arrhythmic Risk, Left Ventricular Cardiomyopathy

BACKGROUND

Among inherited cardiomyopathies involving the left ventricle, whether dilated or not, certain genotypes carry a well-established arrhythmic risk, notably manifested as sustained monomorphic ventricular tachycardia (SMVT). Nonetheless, the precise localization and electrophysiological profile of this substrate remain undisclosed across different genotypes.

METHODS

Patients diagnosed with cardiomyopathy and left ventricle involvement due to high-risk genetic variants and SMVT treated by electrophysiological study were recruited from 18 European/US centers. Electrophysiological study, imaging, and outcomes data after ablation were assessed in relation to genotype.

RESULTS

Seventy-one patients were included (49.6 Q1-Q3 [40-60] years, 76% men). They were divided into 4 groups according to the affected protein: desmosomal (DSP, PKP2, DSG2, and DSC2), nuclear membrane (LMNA and TMEM43), cytoskeleton (FLNC and DES), and sarcoplasmic reticulum (PLN). Desmosomal genes, TMEM43, and PLN were associated with biventricular disease, while variants in LMNA and cytoskeleton genes had predominant left ventricle involvement (P=0.001). The location of the clinical-SMVT substrate was significantly different based on genotype (P=0.005). DSP and cytoskeleton genes presented SMVTs with right bundle branch block morphology, which origin was identified in the inferolateral segments of the left ventricle. The other desmosomal genes (PKP2 and DSG2), along with TMEM43, showed SMVTs with left bundle branch block morphology and predominantly right ventricular substrate. In contrast, LMNA substrate was mainly observed in the interventricular septum. During a median of 26 Q1-Q3 (10.6-65) months, 27% of patients experienced recurrences of clinical SMVT with differences between genotypes (log-rank 0.016). Nuclear membrane genes demonstrated the highest recurrence rate compared with desmosomal genes (hazard ratio, 4.56 [95% CI, 1.5-13.8]).

CONCLUSIONS

The anatomic substrate of SMVTs shows a strong correlation with the underlying genotype, electrocardiographic morphology, and recurrence rate. Particularly, patients with nuclear membrane gene variants have a significantly higher recurrence rate compared with those with desmosomal gene variants.

Volumetric lesion analysis and validation of various bipolar configurations in radiofrequency ablation of ventricular myocardium in a bovine model

BACKGROUND

The bipolar radiofrequency ablation(B-RFA) strategy was increasingly used to target deep intramural re-entrant foci responsible for the arrhythmia not ablated by conventional unipolar RFA / sequential unipolar RFA. Lesional characteristics of various bipolar configurations were largely unknown.

OBJECTIVE

To investigate the lesional geometry in relation to various factors to determine the most effective ablation strategy that minimises steam pops and achieves transmurality. To assess the temperatures at the return electrode.

METHODS

A custom-made validated ex-vivo bipolar ablation model was used to assess lesion formation. The myocardial sample was placed between two ablation catheters in four different orientations. Lesions were created using different power (30 W, 40 W, 50 W) and time settings(30, 40 and 50 s) with different catheter orientations. Data was analysed using binary logistic regression and multiple linear regression.

RESULTS

Among 107 lesions, The volume of the active catheter lesion (266 +/- 137 mm^3) significantly differed from their return electrode counterparts (130 +/- 91.8 mm^3) (p < 0.001), and the temperatures at the return electrode end were lower than at the active electrode (p = 0.004). Higher power and longer duration application led to more frequent steam pops (p < 0.001), while true parallel configuration resulted in fewer steam pops (p < 0.001).

CONCLUSION

A custom model without ground electrode temperature monitoring is safe and cost-effective. The safest strategy is a true parallel configuration with an inter-electrode distance of at least 15 mm and a power of 30 W to 40 W, which generates lower steam pops and better transmurality.

Ventricular Tachycardia Ablation Endpoints: Moving Beyond Noninducibility

In patients with structural heart disease and ventricular tachycardia (VT) undergoing catheter ablation, the response to programmed electrical stimulation (PES) at the end of the procedure has been traditionally used to evaluate the acute success and predict long-term outcomes. Although noninducibility at PES has been extensively investigated and validated in clinical trials and large multicenter registries, its performance in predicting long-term freedom from VT is suboptimal. In addition, PES has inherent limitations related to the influence of background antiarrhythmic drug therapy, periprocedural use of anesthesia, and the heterogeneity in PES protocols. The increased utilization of substrate-based ablation approaches that focus on ablation of abnormal electrograms identified with mapping in sinus or paced rhythm has been paralleled by a need for additional procedural endpoints beyond VT noninducibility at PES. This article critically appraises the relative merits and limitations of different procedural endpoints according to different ablation techniques for catheter ablation of scar-related VT.