Relationship between the atrial-activation pattern around the triangle of Koch and successful ablation sites in slow-fast atrioventricular nodal reentrant tachycardia

Background

The precise details of atrial activation around the triangle of Koch (ToK) remain unknown. We evaluated the relationship between the atrial-activation pattern around the ToK and success sites for slow-pathway (SP) modification ablation in slow-fast atrioventricular reentrant tachycardia (AVNRT).

Methods

Thirty patients with slow-fast AVNRT who underwent successful ablation were enrolled. Atrial activation around the ToK during sinus rhythm was investigated using ultra-high-density mapping pre-ablation. The relationships among features of atrial-activation pattern and success sites were examined.

Results

Of 30 patients (22 cryoablation; 8 radiofrequency ablation), 26 patients had a collision site of two wavefronts of delayed atrial activation within ToK, indicating a success site. The activation-search function of Lumipoint software, which highlights only atrial activation with a spatiotemporal consistency, showed non-highlighted area on the tricuspid-annulus side of ToK. In 23 of the patients, a spiky potential was recorded at that collision site outside the Lumipoint-highlighted area. Fifteen cryoablation patients with a success site coincident with a collision site outside the Lumipoint-highlighted area had significantly more frequent disappearances of SP after initial cryoablation (46.7% vs. 0%, p = .029), fewer cryoablations (3.7 ± 1.8 vs. 5.3 ± 1.3, p = .045), and shorter procedure times (170 ± 57 vs. 228 ± 91 min, p = .082) compared to the seven cryoablation patients without such sites. Four patients had transient AV block by ablation inside the Lumipoint-highlighted area with fractionated signals, but no patient developed permanent AV block or recurrence post-procedure (median follow-up: 375 days).

Conclusions

SP modification ablation at the collision site of atrial activation of the tricuspid-annulus side along with a spiky potential could provide a better outcome.

Electrogram characteristics at successful cryoablation sites in slow-fast atrioventricular nodal reentrant tachycardia

PURPOSE

Cryoablation is a safe alternative to radiofrequency (RF) ablation for slow-fast atrioventricular reentrant tachycardia (AVNRT); however, optimal electrogram parameters for site selection remain unknown. We retrospectively investigated local electrograms for slow pathway (SP) modification in cryoablation.

METHODS

Forty-five consecutive patients with slow-fast AVNRT who underwent cryoablation using a 6-mm-tip catheter were enrolled. Electrogram parameters for sites of successful SP modification (success-sites) were investigated; these included the interval between atrial activation at His and the last deflection of SP potential, defined as the His(A)-SPP interval. In 8 patients, 3-dimensional mapping by multi-electrode catheter was performed pre-ablation for more detailed SP assessment.

RESULTS

Twenty-seven of 45 patients had successful SP modification by 1 cycle of freeze-thaw-freeze cryoablation at a single site with a low amplitude and fragmented SP potential. Among a total of 76 cryoablation sites in all patients, the His(A)-SPP interval at success-sites (45 sites) was significantly longer than that at unsuccess-sites (31 sites) (86 ± 9 vs.78 ± 10 msec, p < 0.0001). The AV amplitude ratio was not significantly different between success-and unsuccess-sites (0.21 ± 0.22 vs.0.25 ± 0.23, p = 0.429). The cutoff value of the His(A)-SPP interval for successful cryoablation was 82 msec with a sensitivity of 0.67 and specificity of 0.71 (AUC: 0.739; 95%CI: 0.626-0.852; p < 0.0001). Three-dimensional mapping in all 8 patients showed that sites with the most delayed atrial activation and the last deflection of the fragmented SP potential within the Koch's triangle coincided with success-sites.

CONCLUSION

A longer His(A)-SPP interval and fractionated SP potential were characteristics of successful cryoablation for SP modification in slow-fast AVNRT.

Contact Force Guided Radiofrequency Current Application at Developing Myocardium: Summary and Conclusions

BACKGROUND

Catheter contact is one key determinant for lesion size in radiofrequency catheter ablation (RFA). Monitoring of contact force (CF) during RFA has been shown to improve efficacy of RFA in experimental settings as well as in adult patients. Coronary artery narrowing after RFA has been described in experimental settings as well as in children and adults and may be dependent from catheter contact. Value of CF monitoring concerning these issues has not been systematically yet.

OBJECTIVE

Value of high versus low CF during RFA in piglets was studied to assess lesion size and potential coronary artery involvement mimicking RFA in small children.

ANIMALS AND METHODS

RFA with continuous CF monitoring was performed in 24 piglets (median weight 18.5 kg) using a 7F TactiCath Quartz RF ablation catheter (Abbott, Illinois, USA). A total of 7 lesions were induced in each animal applying low (10-20 g) or high (40-60 g) CF. RF energy was delivered with a target temperature of 65 °C at 30 W for 30 seconds. Coronary angiography was performed prior and immediately after RF application. Animals were assigned to repeat coronary angiography followed by heart removal after 48 h (n=12) or 6 months (n=12). Lesions with surrounding myocardium were excised, fixated and stained. Lesion volumes were measured by microscopic planimetry.

RESULTS

A total of 148 RF lesions were identified in the explanted hearts. Only in the subset of lesions at the AV annulus 6 month after ablation, lesion size and number of lesions exhibiting transmural extension were higher in the high CF group compared to low CF. In all other locations CF had no impact on lesion size and mural extension after 48 h as well as after 6 months. Additional parameters as Lesion Size Index and Force Time Integral were also not related to lesion size. Coronary artery damage was present in 2 animals after 48 h and in 1 after 6 months and was not related to CF. This article is protected by copyright. All rights reserved.

Double cryoenergy application (freeze-thaw-freeze) at growing myocardium: Lesion volume and effects on coronary arteries late after energy application. Implications for efficacy and safety in pediatric patients

INTRODUCTION

Cryoenergy is accepted as an alternative to radiofrequency ablation (RFA) in childen for ablation of supraventricular tachycardia substrates. Single cryoenergy application has been shown to be inferior to RFA. Double cryoenergy application has therefore been introduced into clinical practice, but experience concerning efficacy is limited. Coronary artery stenosis has been reported as serious complication after RFA for arrhythmia substrates but not after single cryoablation. The purpose of the study was to assess lesion volume (efficacy) and risk of coronary artery damage (safety), late, that is, 6 months, after double cryoenergy application in a piglet model.

METHODS

Two sequential cycles of cryoenergy were delivered at -75°C for 4 minutes at the atrioventricular groove in five piglets. Animals were restudied after 6 months by coronary angiography and intracoronary ultrasound (ICUS). Ablation lesions were examined histologically and lesion volume was determined by three-dimensional morphometric analysis.

RESULTS

Cryolesion volume was 174.04 ± 67.18 mm³ for atrial and 238.69 ± 112.1 mm³ for ventricular lesions (P > .05). Ventricular lesions, 4.06 ± 1.05 mm, were significantly deeper than atrial lesions, 3.58 ± 0.78 mm, (P < .05). In two of the 29 lesions, cryoenergy induced minor coronary artery injury with mild medial and adventitial thickening as well as minimal intimal proliferation, which had neither been detected by coronary angiography nor by ICUS.

CONCLUSION

Late after double cryoenergy application at growing myocardium, subclinical minor affection of the coronary artery wall could be detected with minimal intimal proliferation. As lifetime sequelae of this finding remains unknown, further studies are warranted to address safety of repeated cycles of cryoenergy application for tachycardia substrates in children.

Comparison of 6-mm Versus 8-mm-Tip Cryoablation Catheter for the Treatment of Atrioventricular Nodal Reentrant Tachycardia in Children: A Prospective Study

Due to its safety profile, cryoablation (Cryo) for atrioventricular nodal reentrant tachycardia (AVNRT) is more commonly preferred over radiofrequency (RF) ablation in children in recent years. Recent studies demonstrated high long-term success rates comparable to radiofrequency ablation. The aim of this prospective study was to compare the efficacy and safety of an 8-mm-tip versus 6-mm-tip Cryo catheter in the treatment of AVNRT in children. A total of 125 consecutive patients over 10 years of age with AVNRT were included. EnSite system (St. JudeMedical, St Paul, MN, USA) was used to reduce or eliminate fluoroscopy. The acute procedural success was 100% in both groups. The prodecure duration for the 8-mm-tip group was shorter (151.6 ± 63.2 vs. 126.6 ± 36.7 min, p < 0.01, respectively). Fluoroscopy was used in only 7 patients. The mean follow-up duration was 14.6 ± 8.4 months (median 13.5 months, min. 3 months and max. 27 months). The recurrence rate for AVNRT was also comparable between the two groups (6-mm tip: 9.6 vs. 8-mm tip: 8%). Cryo of AVNRT is a safe and effective procedure with comparable acute and mid-term follow-up success rates using 6-mm and 8-mm-tip catheters in children. In addition, procedure duration is shorter with an 8-mm-tip Cryo catheter.

Effects of Triple Cryoenergy Application on Lesion Formation and Coronary Arteries in the Developing Myocardium

To improve long-term outcome after cryoablation of substrates of supraventricular tachycardia, application of two and three consecutive freeze-thaw cycles has been performed. The effect of triple freeze-thaw cycles on lesion formation within developing myocardium and coronary arteries, however, has not been studied yet. In eight piglets (mean age 15 weeks, weight 15-20 kg), 30 cryolesions (three consecutive freeze-thaw cycles) were applied to the atrial aspect of both AV valve annuli (n = 18) as well as to ventricular myocardium below the valves (n = 12). Coronary angiography was performed before and after cryoenergy application. The animals were reevaluated by coronary angiography and intracoronary ultrasound (ICUS) after 48 h. All hearts were removed for histological examination of the lesions subsequently. After staining (hematoxylin-eosin, desmin immunohistochemistry), lesions was measured by planimetry with a digital virtual miscroscope analysis system and volumes of the cryolesions were calculated. Mean atrial lesion volume was 190.68 ± 167.53 mm³ (n = 18), and mean ventricular lesion volume was 184.34 ± 107.42 mm³ (n = 12). Compared with previously reported data on lesion volumes after single and double freeze-thaw cycles, lesions were significantly larger. Coronary arteries were unaffected on coronary angiography as well as on ICUS. No affection of coronary arteries was found on histological examination. Application of three consecutive freeze-thaw cycles resulted in increased lesion volume compared with single and double freeze-thaw cycles. No affection of the coronary arteries was evident. To evaluate the clinical benefit and safety of triple cryoenergy application for catheter ablation, prospective randomized trials are required.

Cryoablation of typical AVNRT: Younger age and administration of bonus ablation favor long-term success

BACKGROUND

Cryoablation (CA) is an emerging tool for the treatment of supraventricular tachyarrhythmias. Determinants of long-term success still need clarification.

OBJECTIVE

The purpose of this study was to assess which patients' and procedural features affect the long-term efficacy of CA for typical atrioventricular nodal reentrant tachycardia (AVNRT).

METHODS

Eighty-five consecutive patients undergoing CA for typical AVNRT were divided into 3 groups of age: group A, ≤20 years, n = 20 (23.5%); group B, 21-50 years, n = 30 (35.3%); group C, ≥51 years, n = 35 (41.2%). CA was performed for 5 minutes at -75°C in all; 4-minute bonus CA was delivered if not contraindicated (ie, transient PR interval lengthening during the first application and narrow triangle of Koch). The efficacy end point was the absence of recurrences at 12-month follow-up.

RESULTS

CA was acutely successful in all 85 patients (100%). Bonus ablation was performed in 69 (81.2%). No permanent complications were observed. At follow-up, AVNRT recurrences occurred in 9 patients (10.6%): group A, 0 (0%); group B, 2 (6.7%), group C, 7 (20%). Incidence of recurrences was significantly different between age groups (P = .047) and between patients receiving (7.2%) and not receiving (25.0%) bonus CA (P = .038). In multivariable analysis, age groups (odds ratio [OR] 5.917; 95% confidence interval [CI] 1.372-25.518; P = .017) and bonus CA (OR 0.115; 95% CI 0.018-0.724; P = .021) were the only independent predictors of recurrences. Furthermore, age as a continuous variable remained statistically associated with recurrences (OR 1.046; 95% CI 1.002-1.091; P = .038).

CONCLUSION

CA is effective and safe for typical AVNRT ablation. Younger age and bonus CA administration are independent predictors of success at 12 months. Incidence of recurrences is low in patients younger than 21 years.