Electrographic flow mapping of persistent atrial fibrillation: intra- and inter-procedure reproducibility in the absence of 'ground truth'

AIMS

Validating mapping systems that identify atrial fibrillation (AF) sources (focal/rotational activity) is confounded by the absence of ground truth. A key concern of prior mapping technologies is spatiotemporal instability, manifesting as poor map reproducibility. Electrographic flow (EGF) employs a novel algorithm that visualizes atrial electrical wavefront propagation to identify putative AF sources. We analysed both intra- (3 min) and inter- (>3 months) procedure EGF map reproducibility.

METHODS AND RESULTS

In 23 persistent AF patients, after pulmonary vein isolation (PVI), EGF maps were generated from 3 serial 1 min recordings using a 64-electrode basket mapping catheter (triplets) at right and left atrial locations. Source prevalence from map triplets was compared between recordings. Per protocol, 12 patients returned for 3-month remapping (1 non-inducible): index procedure post-PVI EGF maps were compared with initial EGF remapping at 3-month redo. Intra-procedure reproducibility: analysing 224 map triplets (111 right atrium, 113 left atrium) revealed a high degree of map consistency with minimal min-to-min shifts: 97 triplets (43%), exact match of leading sources on all 3 maps; 95 triplets (42%), leading source within 1 electrode space on 2 of 3 maps; and 32 triplets (14%), chaotic leading source pattern. Average deviation in source prevalence over 60 s was low (6.4%). Inter-procedure reproducibility: spatiotemporal stability of EGF mapping >3 months was seen in 16 of 18 (89%) sources mapped in 12 patients with (re)inducible AF.

CONCLUSION

Electrographic flow mapping generates reproducible intra- and inter-procedural maps, providing rationale for randomized clinical trials targeting these putative AF sources.

Comparison of Outcomes between a Basket Catheter and a Balloon Catheter for Endoscopic Common Bile Duct Stone Removal

INTRODUCTION

Evidence for the outcomes of endoscopic retrograde cholangiopancreatography (ERCP) between a basket catheter and a balloon catheter for endoscopic common bile duct stone (CBDS) removal is lacking. This study aimed to compare ERCP outcomes using a basket catheter and a balloon catheter for endoscopic CBDS removal.

METHODS

This multicenter retrospective study included 904 consecutive patients with native papilla who underwent endoscopic stone removal for CBDS ≤10 mm using a basket catheter and/or a balloon catheter at three institutions in Japan. ERCP outcomes between the basket and balloon groups were compared using inverse probability of treatment weighting (IPTW) method.

RESULTS

ERCP-related adverse events occurred in 6.5% (29/449) and 7.7% (35/455) of patients in the basket and balloon groups, respectively (IPTW-adjusted p = 0.52). The incidences of post-ERCP pancreatitis, cholangitis, and perforation were similar in the basket and balloon groups (3.8% vs. 2.9%, 1.3% vs. 0.9%, and 0.7% vs. 0.7%, respectively). However, bleeding incidences were significantly higher in the balloon group than in the basket group (3.3% vs. 0.7%, IPTW-adjusted p = 0.012). Successful complete stone removal at one ERCP session using a single catheter was achieved in 17.8% (80/449) in the basket group and in 81.3% (370/455) in the balloon group (IPTW-adjusted p < 0.001).

DISCUSSION

A balloon catheter is more likely to complete stone extraction for CBDS ≤10 mm with a single catheter at one endoscopic stone removal session. However, the risk for post-ERCP bleeding is higher in the balloon group than in the basket group.

Technical advance in silico and in vitro development of a new bipolar radiofrequency ablation device for renal denervation

Background

Renal denervation with radiofrequency ablation has become an accepted treatment for drug-resistant hypertension. However, there is a continuing need to develop new catheters for high-accuracy, targeted ablation. We therefore developed a radiofrequency bipolar electrode for controlled, targeted ablation through Joule heating induction between 60 and 100 °C. The bipolar design can easily be assembled into a basket catheter for deployment inside the renal artery.

Methods

Finite element modeling was used to determine the optimum catheter design to deliver a minimum ablation zone of 4 mm (W) × 10 mm (L) × 4 mm (H) within 60 s with a 500 kHz, 60 Vp-p signal, and 3 W maximum. The in silico model was validated with in vitro experiments using a thermochromic phantom tissue prepared with polyacrylamide gel and a thermochromic ink additive that permanently changes from pink to magenta when heated over 60 °C.

Results

The in vitro ablation zone closely matched the size and shape of the simulated area. The new electrode design directs the current density towards the artery walls and tissue, reducing unwanted blood temperature increases by focusing energy on the ablation zone. In contrast, the basket catheter design does not block renal flow during renal denervation.

Conclusions

This computational model of radiofrequency ablation can be used to estimate renal artery ablation zones for highly targeted renal denervation in patients with resistant hypertension. Furthermore, this innovative catheter has short ablation times and is one of the lowest power requirements of existing designs to perform the ablation.

Absence of rotational activity detected using 2-dimensional phase mapping in the corresponding 3-dimensional phase maps in human persistent atrial fibrillation

BACKGROUND

Current phase mapping systems for atrial fibrillation create 2-dimensional (2D) maps. This process may affect the accurate detection of rotors. We developed a 3-dimensional (3D) phase mapping technique that uses the 3D locations of basket electrodes to project phase onto patient-specific left atrial 3D surface anatomy.

OBJECTIVE

We sought to determine whether rotors detected in 2D phase maps were present at the corresponding time segments and anatomical locations in 3D phase maps.

METHODS

One-minute left atrial atrial fibrillation recordings were obtained in 14 patients using the basket catheter and analyzed off-line. Using the same phase values, 2D and 3D phase maps were created. Analysis involved determining the dominant propagation patterns in 2D phase maps and evaluating the presence of rotors detected in 2D phase maps in the corresponding 3D phase maps.

RESULTS

Using 2D phase mapping, the dominant propagation pattern was single wavefront (36.6%) followed by focal activation (34.0%), disorganized activity (23.7%), rotors (3.3%), and multiple wavefronts (2.4%). Ten transient rotors were observed in 9 of 14 patients (64%). The mean rotor duration was 1.1 ± 0.7 seconds. None of the 10 rotors observed in 2D phase maps were seen at the corresponding time segments and anatomical locations in 3D phase maps; 4 of 10 corresponded with single wavefronts in 3D phase maps, 2 of 10 with 2 simultaneous wavefronts, 1 of 10 with disorganized activity, and in 3 of 10 there was no coverage by the basket catheter at the corresponding 3D anatomical location.

CONCLUSION

Rotors detected in 2D phase maps were not observed in the corresponding 3D phase maps. These findings may have implications for current systems that use 2D phase mapping.

Prospective randomized study of endoscopic biliary stone extraction using either a basket or a balloon catheter: the BasketBall study

BACKGROUND

In Japan and Europe, a retrieval basket is generally used for endoscopic extraction of bile duct stones, while in the US, a retrieval balloon is mainly used. However, the efficacies of these two devices have not been previously compared. Therefore, the present multicenter, prospective, randomized study was performed to compare the efficacies of these two devices for endoscopic biliary stone extraction.

METHODS

This study was designed as a non-inferiority study in comparing a basket removal with a balloon removal. Six Japanese institutions participated in this study, which included 184 patients with bile duct stones <11 mm in diameter with no limitation in the number of stones. The stones were identified and measured during ERCP, after which the patients were randomly assigned to undergo endoscopic stone extraction using either a basket catheter or a balloon catheter. The primary end point was the rate of complete removals of stones within 10 min, and the secondary end point was the rate of procedure-related complications.

RESULTS

There were 91 patients in the basket group and 93 in the balloon group. The rate of successful stone extraction within 10 min was 81.3 % (74/91) in the basket group and 83.9 % (78/93) in the balloon group (p = 0.7000). The complication rate was 6.6 % in the basket group and 11.8 % in the balloon group (p = 0.3092). Complications included bleeding, pancreatitis, and cholangitis.

CONCLUSIONS

Basket and balloon catheters showed similar efficacies for endoscopic biliary stone extraction when stone size is 11 mm or smaller.

Catheter ablation of hemodynamically unstable ventricular tachycardia in ischemic cardiomyopathy using high-resolution mapping

Catheter ablation is a recommended therapy option for ventricular tachycardia (VT). The antegrade transseptal approach for targeting VT with left ventricular origin is feasible with the high-resolution basket catheter. High-resolution mapping offers the potential to quickly acquire detailed voltage and activation maps. This may help to identify the crucial VT-substrate even in patients with huge scar areas and hemodynamically unstable VT.

Effect of adenosine triphosphate on left atrial electrogram interval and dominant frequency in human atrial fibrillation

Background

Complex fractionated atrial electrograms (CFAEs) and high dominant frequency (DF) are targets for atrial fibrillation (AF) ablation. Although adenosine triphosphate (ATP) is known to promote AF by shortening the atrial refractory period, its role in the pathogenesis of CFAEs and DF during AF is not fully understood.

Methods

We recorded electrical activity from a 64-electrode basket catheter placed in the left atrium (LA) of patients with paroxysmal AF (PAF, n=18) or persistent AF (PerAF, n=19) before ablation. Atrial electrogram fractionation intervals (FIs) and DFs were measured from bipolar electrograms of each adjacent electrode pair. Offline mean atrial FIs and DFs were obtained before bolus injection of 30 mg ATP. Peak effect was defined as an R–R interval >3 s.

Results

With ATP, the mean FI decreased (from 110.4±29.1 ms to 90.5±24.7 ms, P<0.0001) and DF increased (from 6.4±0.6 Hz to 7.1±0.8 Hz, P<0.0001) in all patients. There was no difference in the FI decrease between the two groups (−20.3±20.5 ms vs. −19.6±14.5 ms, P=0.6032), but the increase in DF was significantly greater in PAF patients (1.1±0.8 Hz vs. 0.3±0.6 Hz, P=0.0051).

Conclusions

ATP shortens atrial FIs and increases DFs in both PAF and PerAF patients. The significant increase in DF in PAF patients suggests that pathophysiologic characteristics related to the frequency of atrial fractionation change as atrial remodeling progresses.

Spatial and temporal variability of the complex fractionated atrial electrogram activity and dominant frequency in human atrial fibrillation

BACKGROUND

The presence of complex fractionated atrial electrograms (CFAEs) and high dominant frequencies (DFs) during atrial fibrillation (AF) have been demonstrated to be related to AF maintenance. Therefore, sequential mapping of CFAEs and DFs have been used for target sites of AF ablation. However, such mapping strategies are valid only if the CFAEs and DFs are spatiotemporally stable during the mapping procedure. We obtained spatially stable multi-electrode recordings to assess the spatiotemporal stability of CFAEs and DFs.

METHODS

We recorded electrical activity during AF for 10 min with a 64-electrode basket catheter (48 bipole electrode pairs) placed in the left atrium in 36 patients with AF (paroxysmal AF [PAF], n=16; persistent AF [PerAF], n=20). The spatial and temporal distribution of the CFAEs (fractionation interval <120 ms) and high DFs (>8 Hz) at 1-min intervals for 10 min were compared for each of the 48 bipoles.

RESULTS

The baseline CFAEs were located at 68.5±14.0% (32.9±6.7) of the 48 bipoles; however, the high DF sites were fewer (9.6±8.6% [4.6±4.1 bipoles]). The CFAEs sites did not change significantly during the 10-min recording period (kappa statistic: 0.71±0.24); however, the high DF sites changed significantly (kappa statistic: 0.07±0.19). These spatiotemporal changes in the CFAEs and high DFs did not differ between patients with PAF and PerAF.

CONCLUSIONS

Regardless of the AF type, CFAEs sites, but not high DF sites, showed a high degree of spatial and temporal stability.