Usefulness of filtered unipolar electrogram morphology for evaluating transmurality of ablated lesions during pulmonary vein isolation

Continuous and discontinuous radiofrequency energy delivery on the atrial free wall: Lesion transmurality, width, and biophysical characteristics

Background

Although lesion transmurality is required for durable pulmonary vein isolation, excess ablation is associated with increased risk of complications.

Objective

We sought to understand the impact of interrupted radiofrequency (RF) delivery conditions on lesion characteristics in the atrial free wall.

Methods

Thirty-three (11 left atrial, 22 right atrial) RF ablation lesions were created in the atria of 6 swine using power control mode (25 W, target contact force 15 g) with 1 of 3 conditions: 15 seconds ablation (n = 8), 30 seconds ablation (n = 14), or 2 15-second ablations at the same site separated by a 2-minute interruption (15 seconds × 2) (n = 11).

Results

Thirty of 33 lesions were transmural. Rates of transmurality (P = .45) and endocardial lesion width (5.6 ± 1.2 mm, P = .70) were similar between conditions. Mean tissue thickness was 1.7 ± 0.8 mm for transmural lesions. Wide variability in bipolar electrogram attenuation was observed across and within conditions and there were no significant between-group differences. Although impedance reductions were numerically greater in the 30-second and 15-second × 2 conditions (-14.6 ± 6.6 ohms and -14.0 ± 4.4 ohms, respectively) compared to the 15-second condition (-10.3 ± 6.4 ohms), variability was large, and differences were not statistically significant (P = .243). Impedance changes after ablation were largely transient.

Conclusion

A single 15-second ablation at 25 W (target contact force of 15 g) with good stability produced similarly sized lesions compared to 30-second ablations and 2 15-second ablations at the same site in atrial free wall tissue. These data suggest over-ablation in the atria is common, larger-diameter lesions may require greater power, and many clinically available parameters of lesion size may be unreliable on the posterior wall.

Monitoring the dynamics of acute radiofrequency ablation lesion formation in thin-walled atria - a simultaneous optical and electrical mapping study

Background Radiofrequency ablation (RFA) is a common approach to treat cardiac arrhythmias. During this intervention, numerous strategies are applied to indirectly estimate lesion formation. However, the assessment of the spatial extent of these acute injuries needs to be improved in order to create well-defined and durable ablation lesions. Methods We investigated the electrophysiological characteristics of rat atrial myocardium during an ex vivo RFA procedure with fluorescence-optical and electrical mapping. By analyzing optical data, the temporal growth of punctiform ablation lesions was reconstructed after stepwise RFA sequences. Unipolar electrograms (EGMs) were simultaneously recorded by a multielectrode array (MEA) before and after each RFA sequence. Based on the optical results, we searched for electrical features to delineate these lesions from healthy myocardium. Results Several unipolar EGM parameters were monotonically decreasing when distances between the electrode and lesion boundary were smaller than 2 mm. The negative component of the unipolar EGM [negative peak amplitude (Aneg)] vanished for distances lesser than 0.4 mm to the lesion boundary. Median peak-to-peak amplitude (Vpp) was decreased by 75% compared to baseline. Conclusion Aneg and Vpp are excellent parameters to discriminate the growing lesion area from healthy myocardium. The experimental setup opens new opportunities to investigate EGM characteristics of more complex ablation lesions.

Unipolar electrogram-guided radiofrequency catheter ablation in paroxysmal atrial fibrillation: electrogram patterns and outcomes

BACKGROUND

Transmural lesions (TLs) are the crucial point for radiofrequency catheter ablation (RFCA) in atrial fibrillation (AF) patients. Previous studies have reported that complete positive unipolar electrogram (UP-EGM) after ablation is associated with transmural lesions. However, UP-EGM patterns may differ in different regions of continuous circular lesions (CCLs) around the pulmonary vein ostia after ablation. We aimed to analyze the different UP-EGM patterns in different CCL regions after ablation and the effectiveness of UP-EGM guided RFCA in paroxysmal atrial fibrillation (PAF).

METHODS

A total of 43 patients with PAF (aged 59 ± 11 years; 65% male) were consecutively included. Pulmonary vein isolation was achieved by contiguous point-by-point RFCA. UP-EGM was recorded by the ablation catheter. Both CCLs were divided into six regions. Two points were randomly chosen from each region to analyze UP-EGM type after ablation. All the patients were followed for atrial arrhythmias recurrence.

RESULTS

All pulmonary veins were isolated with complete bidirectional block. A total of 1032 RFCA points with complete positive UP-EGM were collected. UP-EGM morphology after ablation was divided into four different types defined as R, rR', Rr', and M. M patterns mostly appeared in anterosuperior (65%) and roof (49%) regions of left CCLs. In the remaining regions, the percentage of non-M patterns (R, rR', and Rr') ranged from 63% in posteroinferior regions of right CCLs to 88% in anteroinferior regions of right CCLs. After a mean follow-up time of 19 months, 37 (86%) patients remained in sinus rhythm.

CONCLUSION

Most (72%) UP-EGM types after ablation are non-M patterns. Pulmonary vein isolation guided by UP-EGM with a complete positive pattern in PAF patients is reliable.