Impact of respiration on electroanatomical mapping of the right atrium: implication for cavotricuspid isthmus ablation

Tissue thickness measured with dielectric-based technology during radiofrequency catheter ablation

Radiofrequency catheter ablation of the cavotricuspid isthmus is the standard treatment for patients suffering from typical atrial flutter. The aim of this study was to test the feasibility of tissue thickness and lesion transmurality measurement by a novel dielectric system. This was a retrospective multicentric non-randomized open-label, single-arm study. The atrial wall thickness was significantly higher close to the tricuspid annulus than close to the inferior vena cava and a trend towards a progressive decrease of atrial wall thickness was observed moving the mapping catheter from the tricuspid valve to the inferior vena cava. The possibility to visualize the tissue thickness could modify the way to deliver radiofrequency energy, allowing a tailored approach in cardiac ablation procedures.

Effect of contact vector direction on achieving cavotricuspid isthmus block

Cavotricuspid isthmus (CTI) ablation is an important treatment strategy for CTI-dependent atrial flutter (AFL). The location of the catheter contact area is confirmed by the contact vector direction (CVD) through three-dimensional mapping during the procedure. However, the relationship between CVD during radiofrequency ablation and its efficacy in achieving CTI block has not been clarified. This study aimed to investigate the relationship between CVD and efficacy in achieving CTI block. CVDs during radiofrequency ablation were divided into proximal vectors against the distal tip (P-vector) and other vectors (normal-vector). In 39 patients who underwent CTI linear ablation, the CTIs were divided into two segments: the tricuspid valve area (anterior) and inferior vena cava area (posterior). The frequency of the residual conduction gap was compared between segments in which the P- and normal-vectors were observed. P-vectors were observed in 13 of the 78 segments. The median ablation index was not significantly different between segments in which the P-vector and normal-vector were observed (398.2 [384.2-402.2] vs. 393.3 [378.3-400.1], p = 0.15). However, residual conduction gaps were significantly more frequently observed in the segment in which the P-vector was observed than those in which only the normal-vector was observed (6/13, 46.2% vs. 3/65, 4.6%; p < 0.01). During a 6-month follow-up, two patients required a second session of ablation due to AFL recurrence. A residual conduction gap was observed in one patient at the site where the P-vector was observed in the first session. Avoiding the P-vector might be an important factor in improving CTI block and reducing AFL recurrence.

Computational ECG mapping and respiratory gating to optimize stereotactic ablative radiotherapy workflow for refractory ventricular tachycardia

BACKGROUND

Stereotactic ablative radiotherapy (SAbR) is an emerging therapy for refractory ventricular tachycardia (VT). However, the current workflow is complicated, and the precision and safety in patients with significant cardiorespiratory motion and VT targets near the stomach may be suboptimal.

OBJECTIVE

We hypothesized that automated 12-lead electrocardiogram (ECG) mapping and respiratory-gated therapy may improve the ease and precision of SAbR planning and facilitate safe radiation delivery in patients with refractory VT.

METHODS

Consecutive patients with refractory VT were studied at 2 hospitals. VT exit sites were localized using a 3-D computational ECG algorithm noninvasively and compared to available prior invasive mapping. Radiotherapy (25 Gy) was delivered at end-expiration when cardiac respiratory motion was ≥0.6 cm or targets were ≤2 cm from the stomach.

RESULTS

In 6 patients (ejection fraction 29% ± 13%), 4.2 ± 2.3 VT morphologies per patient were mapped. Overall, 7 out of 7 computational ECG mappings (100%) colocalized to the identical cardiac segment when prior invasive electrophysiology study was available. Respiratory gating was associated with smaller planning target volumes compared to nongated volumes (71 ± 7 vs 153 ± 35 cc, P < .01). In 2 patients with inferior wall VT targets close to the stomach (6 mm proximity) or significant respiratory motion (22 mm excursion), no GI complications were observed at 9- and 12-month follow-up. Implantable cardioverter-defibrillator shocks decreased from 23 ± 12 shocks/patient to 0.67 ± 1.0 (P < .001) post-SAbR at 6.0 ± 4.9 months follow-up.

CONCLUSIONS

A workflow including computational ECG mapping and protocol-guided respiratory gating is feasible, is safe, and may improve the ease of SAbR planning. Studies to validate this workflow in larger populations are required.

Impact of respiration gating on image integration guided atrial fibrillation ablation

BACKGROUND

Radiofrequency (RF) catheter ablation guided by electroanatomic mapping systems is an effective therapy for atrial fibrillation. However, it may be affected by respiration movements. The aim of this study was to determine the impact of respiratory gating on procedural parameters in patients undergoing catheter ablation of atrial fibrillation (AF).

METHODS AND RESULTS

One-hundred forty consecutive patients undergoing pulmonary vein isolation were admitted to study. Respiratory gating module (AccuResp algorithm, Carto3, Biosense Webster) was enabled in 70 patients and disabled in 70 patients during procedures. Successful pulmonary vein isolation and sinus rhythm were obtained in all patients. A significant reduction in total procedure times [median 77, interquartile range (IQR 66-95) min vs median 82 (IQR 72-104) min, p < 0.05] and fluoroscopy times [median 14 (IQR 9-17) min vs median 16 (IQR 12-22) min, p < 0.05] were observed in the respiratory gated group. Although ablation times (duration between the first and last ablation) were significantly shorter in respiratory gated group [median 37 (IQR 32-53) min vs median 48 (IQR 39-65) min, p < 0.05], total RF application durations were not different between two groups [median 1,554 (IQR 1,213-2,196) s vs median 1,802 (IQR 1,344-2,448) s, p = 0.11]. Difference in electroanatomical map reconstruction times was not significant [median 14 (IQR 12-16) min in gated group vs median 13 (IQR 10-18) min in nongated group, p = 0.19].

CONCLUSION

Respiratory gating significantly improves fluoroscopy and ablation times during electroanatomic mapping guided AF ablation. Respiratory gated maps may provide uninterrupted continuous ablation applications. Furthermore, using automatic respiratory gating module does not prolong mapping times.