Optimized lesion size index (o-LSI): A novel predictor for sufficient ablation of pulmonary vein isolation

Voltage-guided pulmonary vein isolation for atrial fibrillation

BACKGROUND

Bipolar voltage amplitude is capable of helping determine the ideal lesion size index (LSI) setting during radiofrequency ablation for atrial fibrillation (AF).

OBJECTIVE

We aimed to determine whether voltage-guided pulmonary vein isolation (PVI) is noninferior to conventional LSI-guided PVI in patients with nonvalvular AF.

METHODS

This was a multicenter randomized trial conducted during a period of 12 months. The primary efficacy end points of the study were AF recurrence, atrial flutter, and atrial tachycardia, and the noninferiority margin was set at a hazard ratio of 1.4. The primary safety end point was a composite of procedure-related complications.

RESULTS

A total of 370 patients underwent randomization; 189 and 181 were assigned to the voltage (underwent voltage-guided PVI) and control (underwent conventional LSI-guided PVI) groups, respectively. The primary efficacy end point occurred in 22 patients (12.0%) in the voltage group and 23 patients (12.9%) in the control group (1-year Kaplan-Meier event-free rate estimates, 88.0% and 87.1%, respectively; hazard ratio, 1.00; 95% confidence interval, 0.80-1.25). The primary safety end points were 4.8% in the voltage group and 6.6% in the control group (P = .2791). PVI time was significantly shorter in the voltage group (35.7 ± 14.5 minutes vs 39.7 ± 14.7 minutes; P < .001).

CONCLUSION

Voltage-guided PVI was noninferior to conventional LSI-guided PVI with respect to efficacy in the treatment of patients with AF, and its use significantly reduced procedure time. UMIN Clinical Trials Registry: UMIN000042325.

Evaluation and comparison of impedance and amplitude changes in lesion index-guided pulmonary vein isolation

Background

The lesion index (LSI) has been used to estimate lesion formation after radiofrequency catheter ablation. However, the impedance drop and decrease in bipolar amplitude of intracardiac electrograms, which are parameters that are traditionally used to predict effective ablation lesions, are not used to calculate LSI. Therefore, we aimed to investigate the association between LSI and traditional parameters.

Methods

We retrospectively investigated 1355 ablation points from 31 patients who underwent LSI-guided pulmonary vein isolation (PVI) using TactiCath. All points were classified into 3 groups based on the impedance drop: (i) <10 Ω (n = 67), (ii) 10-20 Ω (n = 909), and (iii) >20 Ω (n = 379). The LSI targets were 4.5 for the posterior left atrium and 5.2 for the anterior left atrium. After excluding 583 points at which it was difficult to measure the amplitude, 772 ablation points during sinus rhythm were included in the analysis of bipolar amplitude.

Results

The target LSI was achieved at 1177 points (86.9%). The median total impedance drop and amplitude just after ablation were 16.0 [13.0-20.0] Ω and 0.21 [0.14-0.30] mV, respectively. There were significant differences among the 3 groups in the impedance and amplitude before ablation, power, target LSI, final LSI, contact force, and interlesion distance. An impedance drop of >10 Ω or an amplitude reduction of >50% was achieved at 95% and 82% of the study points, respectively. There were no major complications at any of the ablation points.

Conclusion

LSI-guided PVI seemed to be useful for making sufficient ablation lesions, as assessed by the conventional parameters of impedance and amplitude change.

Efficacy of High-Density Three-Dimensional Mapping for Verapamil-Sensitive Left Posterior Fascicular Ventricular Tachycardia in Pediatric Patients

In verapamil-sensitive left posterior fascicular ventricular tachycardia (LPF-VT), radiofrequency catheter ablation (RFA) is performed targeting mid-to-late diastolic potential (P1) and presystolic potential (P2) during tachycardia. This study included four patients who had undergone electrophysiological study (EPS) and pediatric patients with verapamil-sensitive LPF-VT who had undergone RFA using high-density three-dimensional (3D) mapping. The included patients were 11-14 years old. During EPS, right bundle branch block and superior configuration VT were induced in all patients. VT mapping was performed via the transseptal approach. P1 and P2 during VT were recorded in three of the four patients. All patients initially underwent RFA via the transseptal approach. In three patients, P1 during VT was targeted, and VT was terminated. The lesion size indices in which VT was terminated were 4.6, 4.6, and 4.7. For one patient whose P1 could not be recorded, linear ablation was performed perpendicularly in the area where P2 was recorded during VT. Among the three patients in whom VT was terminated, linear ablation was performed in two to eliminate the ventricular echo beats. In all patients, VT became uninducible in the acute phase and had not recurred 8-24 months after RFA. High-density 3D mapping with an HD Grid Mapping Catheter allows recording of P1 and P2 during VT and may improve the success rate of RFA in pediatric patients with verapamil-sensitive LPF-VT.

Quantitative late gadolinium enhancement cardiac magnetic resonance analysis of the relationship between ablation parameter and left atrial tissue lesion following pulmonary vein isolation

Background

The impact of ablation parameters on acute tissue lesion formation after pulmonary vein isolation (PVI) has not been sufficiently evaluated in patients with atrial fibrillation. Radiofrequency ablation lesion can be visualized by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). We sought to quantitatively analyze the relationship between ablation parameter and tissue lesion following PVI at different segments of pulmonary vein (PV) using LGE-CMR.

Methods

Twenty-one patients with atrial fibrillation who underwent PVI procedure were retrospectively enrolled. All patients underwent LGE-CMR examination within 3 days after radiofrequency ablation. Ablation parameters during PVI were documented, including lesion size index (LSI), force-time integral (FTI), power, contact force, temperature, and time of duration. The ablation point was projected onto 3-dimensional (3D) left atrial shell constructed base on LGE-CMR and corresponding image intensity ratio (IIR) was calculated on the same shell. A tissue lesion point was defined when the LGE-CMR IIR was > 1.2.

Results

In total, 1,759 ablation points were analyzed. The ablation parameters and IIRs for each PV segment were significantly different (P < 0.0001). IIRs corresponding to ablation points at posterior of PV tended to be higher than those at non-posterior of PV when similar ablation parameters were applied during ablation. LSI was a better predictor of tissue lesion existence following PVI than FTI, contact force, power, temperature, and duration time at non-posterior wall of PV. The IIR showed positive correlation with LSI at non-posterior wall of PV (non-posterior of right PV, r = 0.13, P = 0.001, non-posterior of left PV, r = 0.26, P < 0.0001).

Conclusion

When similar ablation parameters were applied during PVI, the posterior wall of PV had more severe tissue lesion than non-posterior wall of PV. Therefore, it was reasonable to decrease ablation energy at posterior wall of PV. Moreover, LSI was a better index to reflect tissue lesion quality following PVI at non-posterior of PV.

Comparison of the empirical linear ablation and low voltage area-guided ablation in addition to pulmonary vein isolation in patients with persistent atrial fibrillation: a propensity score-matched analysis

Background

The efficacy of pulmonary vein isolation (PVI) alone is not guaranteed for persistent atrial fibrillation (PeAF), and it is unclear which type of ablation approach should be applied in addition to PVI. This study aimed to compare outcomes and prognosis between empirical linear ablation and low-voltage area (LVA) ablation after PVI for PeAF.

Methods

We enrolled 128 patients with PeAF who were assigned to the linear ablation group (n = 64) and the LVA ablation group (n = 64) using a propensity score-matched model. After PVI and cardioversion, the patients underwent either empirical linear ablation or LVA ablation during sinus rhythm. All patients in the linear ablation group underwent both roof line and mitral valve isthmus (MVI) ablations. An electrical-guided ablation targeting LVA (< 0.5 mV) was performed in the LVA group. When there was no LVA in the LVA group, only PVI was applied. We compared the procedural outcomes and recurrence after ablation between the two groups.

Results

The baseline characteristics were well-balanced between the two groups. Fifty patients had LVA (22 and 28 patients in the linear and LVA groups). The roof and MVI lines were completed in 100% and 96.9% of the patients. During the mean follow-up of 279.5 ± 161.3 days, the LVA group had significantly lower recurrence than the linear group (15 patients [23%] vs. 29 patients [45%], p = 0.014). Thirty-five patients were prescribed antiarrhythmic drugs during the follow-up period (linear group, n = 17; LVA group, n = 18); amiodarone and bepridil were administered to most of the patients (15 and 17 patients, respectively). The difference in the prognosis was relevant among the patients with LVA, while this trend was not observed in those without LVA. The LVA ablation group demonstrated significantly lower radiofrequency energy and shorter procedural time compared to the linear ablation group. The recurrence of atrial flutter was more likely to occur in the linear group than in the LVA group (14 [22%] vs. 6 [9.4%], p = 0.052).

Conclusion

The electrophysiological-guided LVA ablation is more effective than empirical linear ablation in PeAF patients with LVA. Unnecessary empirical linear ablation might have a risk of iatrogenic gap and atrial flutter recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02460-9.

Higher than recommended lesion size index target values for pulmonary vein isolation result in better clinical outcomes in paroxysmal atrial fibrillation patients

PURPOSE

Catheter ablation is a cornerstone of the therapy for paroxysmal atrial fibrillation. The importance of effective lesion size formation during pulmonary vein isolation is gauged through conduction recovery and recurrence of arrhythmia. Therefore, the lesion size index (LSI) is designed to utilize traditional intraprocedural parameters and predict procedural success. The impact of the optimal LSI index and the respective segments of the pulmonary veins has not been commonly evaluated. We aimed to assess whether higher and targeted LSI on the different segments of pulmonary veins could actually lead to better clinical outcomes of paroxysmal atrial fibrillation ablation.

METHODS

Retrospective analyses of drug-refractory paroxysmal atrial fibrillation patients who underwent first catheter ablation were conducted. Targeted LSI of 6.5 at the anterior wall and 5.2 at the posterior wall, roof, and floor of the pulmonary vein was applied. The primary endpoint was defined as arrhythmias recurrence assessed by routine electrocardiograms and 24-h ambulatory electrocardiographic monitoring at 3, 6, and 12 months post-ablation.

RESULTS

Among the included 39 patients, the single-procedure 12-month freedom from arrhythmias was reached in 92.3% of patients. Interestingly, there was no tendency towards an increased number of adverse effects using a higher LSI index.

CONCLUSIONS

Atrial fibrillation ablation guided by targeted LSI value showed efficiency on the freedom from arrhythmias during 1-year follow-up period without harmful effects.