Characterization of Fractionated Atrial Electrograms Critical for Maintenance of Atrial Fibrillation

Background—

Whether ablation of complex fractionated atrial electrograms (CFAE) modifies atrial fibrillation (AF) by eliminating drivers or atrial debulking remains unknown. This randomized study aimed to determine the effect of ablating different CFAE morphologies compared with normal electrograms (ie, debulking normal tissue) on the cycle length of persistent AF (AFCL).

Methods and Results—

After pulmonary vein isolation left and right atrial CFAE were targeted, until termination of AF or abolition of CFAE before DC cardioversion. Ten-second electrograms were classified according to a validated scale, with grade 1 being most fractionated and grade 5 normal. Patients were randomly assigned to have CFAE grades eliminated sequentially, from grade 1 to 5 (group 1) or grade 5 to 1 (group 2). An increase in AFCL (mean of left and right atrial appendage) ≥5 ms after a lesion was regarded as significant. CFAE (n=968) were targeted in 20 patients. AFCL increased after targeting 51±35% of grade 1 CFAE, 30±15% grade 2, 12±5% grade 3, 33±12% grade 4, and 8±15% grade 5 CFAE ( P <0.01 for grades 1, 2, and 4 versus 5; 3 versus 5, not significant). The proportion of lesions causing AFCL prolongation was unaffected by the order in which CFAE were targeted.

Conclusions—

Targeting CFAE is not simply atrial debulking. Ablating certain grades of CFAE increases AFCL, suggesting they are more important in maintaining AF.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00894400.

Target Indices for Clinical Ablation in Atrial Fibrillation

Background—

In animal studies of radiofrequency ablation, lesion sizes plateau as the maximum lesion size is reached for an ablation. Lesion parameters are not available in clinical ablations, but preclinical work suggests that these correlate with impedance drop and electrogram attenuation. Characterization of the relationships between catheter contact force, ablation duration, and these surrogate markers of lesion formation may allow us to define targets for effective ablation.

Methods and Results—

Fifteen patients undergoing first-time radiofrequency ablation for nonparoxysmal atrial fibrillation were studied. All were in atrial fibrillation at the time of the procedure. Ablations were performed with an irrigated-tip contact force–sensing catheter in temperature-controlled mode (temperature limited to 48°C, power to 30 W). Included were 285 left atrial static ablations, 247 with additional impedance data. The ablation force time integral (FTI) correlated with the attenuation of the electrogram with ablation (Spearman ρ, –0.14; P =0.02): the relationship plateauing from 500 g·s, a reduction in the electrogram amplitude of 20%. The FTI also correlated with the impedance drop during ablation (Spearman ρ, 0.79; P <0.0005): the relationship was logarithmic, the reduction in the impedance with an increasing FTI also plateauing from 500 g·s, an impedance drop of 7.5%. The ablation duration affected the impedance drop at an FTI if the duration was <10 s. Beyond this time point, the FTI achieved rather than the ablation duration or mean contact force applied determined the impedance drop.

Conclusions—

During nonparoxysmal atrial fibrillation ablation, an FTI of 500 g·s should be targeted with ablation duration of ≥10 s.

Clinical Trials Registration—

URL: http://clinicaltrials.gov/ . Unique Identifier: NCT01587404.

Validation of a classification system to grade fractionation in atrial fibrillation and correlation with automated detection systems

AIMS

We tested application of a grading system describing complex fractionated electrograms (CFE) in atrial fibrillation (AF) and used it to validate automated CFE detection (AUTO).

METHODS AND RESULTS

Ten seconds bipolar electrograms were classified by visual inspection (VI) during ablation of persistent AF and the result compared with offline manual measurement (MM) by a second blinded operator: Grade 1 uninterrupted fractionated activity (defined as segments > or =70 ms) for > or =70% of recording and uninterrupted > or =1 s; Grade 2 interrupted fractionated activity > or =70% of recording; Grade 3 intermittent fractionated activity 30-70%; Grade 4 discrete (<70 ms) complex electrogram (> or =5 direction changes); Grade 5 discrete simple electrograms (< or =4 direction changes); Grade 6 scar. Grade by VI and MM for 100 electrograms agreed in 89%. Five hundred electrograms were graded on Carto and NavX by VI to validate AUTO in (i) detection of CFE (grades 1-4 considered CFE), and (ii) assessing degree of fractionation by correlating grade and score by AUTO (data shown as sensitivity, specificity, r): NavX 'CFE mean' 92%, 91%, 0.56; Carto 'interval confidence level' using factory settings 89%, 62%, -0.72, and other published settings 80%, 74%, -0.65; Carto 'shortest confidence interval' 74%, 70%, 0.43; Carto 'average confidence interval' 86%, 66%, 0.53.

CONCLUSION

Grading CFE by VI is accurate and correlates with AUTO.

A prospective comparison of echocardiography and device algorithms for atrioventricular and interventricular interval optimization in cardiac resynchronization therapy

AIMS

Echocardiographic optimization of atrioventricular (AV) and interventricular (VV) intervals in cardiac resynchronization therapy (CRT) is costly, time-consuming, and requires skill and expertise so is usually undertaken only in 'non-responder' patients. An algorithm in St Jude Medical CRT devices (QuickOpt) claims to optimize these settings automatically. The aim of this study was to compare the two optimization techniques.

METHODS AND RESULTS

Optimization of AV and VV intervals was performed a month after CRT device implantation in 26 patients with heart failure, first by echocardiography then by QuickOpt. The left ventricular outflow tract (LVOT) velocity-time integral (VTI) was measured after optimization by each method. Agreement between the optimization methods was assessed by the Bland-Altman analysis and correlation by Pearson's correlation coefficient. There was good correlation between the LVOT VTI following optimization by both methods (R2 = 0.77, P < 0.001). However, agreement between the two methods was poor, with 15 of 26 and 10 of 26 patients having a >20 ms difference in the optimal AV and VV interval values, respectively. Left ventricular outflow tract VTI was significantly better (22 of 26 patients; P < 0.001) in patients optimized by echocardiography than by QuickOpt.

CONCLUSION

There is a poor agreement in optimal AV and VV intervals determined by echocardiography and QuickOpt, with echocardiographic optimization giving a superior haemodynamic outcome.

Long-term efficacy of catheter ablation for atrial fibrillation: impact of additional targeting of fractionated electrograms

OBJECTIVES

To investigate long-term efficacy of catheter ablation for atrial fibrillation (AF) and the impact of ablating complex or fractionated electrograms (CFEs) in addition to pulmonary vein isolation and linear lesions in persistent AF (PeAF).

METHODS

Consecutive cases from 2002-2007 were analysed. All the patients underwent a wide-area circumferential ablation with confirmation of electrical isolation. For PeAF, linear lesions were added, with additional targeting of CFE from 2005. Data were collected in a prospective database. Attempts were made to contact all patients for follow-up.

RESULTS

285 patients underwent 530 procedures. The mean (SD) age was 57 (11) years, 75% were male, 20% had structural heart disease and 53% had paroxysmal AF (PAF). The mean number of procedures was 1.9 per patient (1.7 for PAF and 2.0 for PeAF). Procedural complications included stroke or transient ischemic attack in 0.6% and pericardial effusion requiring drainage in 1.7%. During 2.7 years (0.2 to 7.4 years) of follow-up from the last procedure, there were seven deaths (unrelated to their ablation or AF) and three strokes or transient ischemic attack (0.3% per year). Freedom from AF/atrial tachyarrhythmia was 86% for PAF and 68% for PeAF. Late recurrence was 3 per 100 years of follow-up after >3 years. The Kaplan-Meier analysis showed that CFE ablation improved the outcome for PeAF after the first cluster of procedures (p=0.049), with a trend towards improved final outcome (p=0.130).

CONCLUSIONS

Long-term freedom from AF is achievable in most patients with PAF and PeAF with low rates of late recurrence. Additional targeting of CFE improves outcome for PeAF. Late adverse events including stroke are few.

Evaluation of ECG Imaging to Map Hemodynamically Stable and Unstable Ventricular Arrhythmias

BACKGROUND

ECG imaging (ECGI) has been used to guide treatment of ventricular ectopy and arrhythmias. However, the accuracy of ECGI in localizing the origin of arrhythmias during catheter ablation of ventricular tachycardia (VT) in structurally abnormal hearts remains to be fully validated.

METHODS

During catheter ablation of VT, simultaneous mapping was performed using electroanatomical mapping (CARTO, Biosense-Webster) and ECGI (CardioInsight, Medtronic) in 18 patients. Sites of entrainment, pace-mapping, and termination during ablation were used to define the VT site of origin (SoO). Distance between SoO and the site of earliest activation on ECGI were measured using co-registered geometries from both systems. The accuracy of ECGI versus a 12-lead surface ECG algorithm was compared.

RESULTS

A total of 29 VTs were available for comparison. Distance between SoO and sites of earliest activation in ECGI was 22.6, 13.9 to 36.2 mm (median, first to third quartile). ECGI mapped VT sites of origin onto the correct AHA segment with higher accuracy than a validated 12-lead ECG algorithm (83.3% versus 38.9%; P=0.015).

CONCLUSIONS

This simultaneous assessment demonstrates that CardioInsight localizes VT circuits with sufficient accuracy to provide a region of interest for targeting mapping for ablation. Resolution is not sufficient to guide discrete radiofrequency lesion delivery via catheter ablation without concomitant use of an electroanatomical mapping system but may be sufficient for segmental ablation with radiotherapy.

Characterization of drivers maintaining atrial fibrillation: Correlation with markers of rapidity and organization on spectral analysis

BACKGROUND

Better characterization of drivers in atrial fibrillation (AF) may facilitate their identification.

OBJECTIVE

The purpose of this study was to demonstrate that certain driver characteristics are associated with greater mechanistic importance in maintaining AF.

METHODS

Persistent AF was mapped in patients using the CARTOFINDER system with a 64-pole basket catheter to identify and ablate drivers with rotational or focal activity after pulmonary vein isolation. An ablation response was defined as cycle length (CL) slowing ≥30 ms or AF termination. Driver sites with an ablation response were correlated to sites of fastest CL, highest dominant frequency (DF), and greatest organization (lowest cycle length variability [CLV] and highest regularity index [RI]). Parameters predicting AF termination with driver ablation were evaluated.

RESULTS

All 29 patients had ≥1 driver identified. Forty-four potential drivers were identified. The predefined ablation response occurred with 39 drivers (89%): 23 rotational and 16 focal. During a 30-second recording, each driver occurred 8.7 ± 5.4 times and completed 3.1 ± 0.9 consecutive repetitions per occurrence. Driver sites correlated best with markers of organization, corresponding to the site of lowest CLV (29/39 [74%]) and highest RI (26/39 [67%]). Correlation with sites of fastest CL and highest DF was poor (17/39 and 15/39, respectively) and depended on driver temporal stability. Greater temporal stability (3.4 ± 0.9 vs 2.7 ± 0.6; P = .001) and driver correlation with sites of lowest CLV and highest RI (both P <.001) predicted AF termination with ablation.

CONCLUSION

Intermittent focal or rotational drivers were identified in all patients. Drivers consistently correlated to organization markers. Greater temporal stability and organization predicted AF termination with driver ablation.

Automated detection of repetitive focal activations in persistent atrial fibrillation: Validation of a novel detection algorithm and application through panoramic and sequential mapping

INTRODUCTION

Identifying drivers in persistent atrial fibrillation (AF) remains challenging. We sought to validate an automated system for detection of focal activation using basket and PentaRay catheters in AF.

METHODS

Patients having ablation for atrial tachycardia (AT) and persistent AF were mapped. Thirty-second unipolar basket and PentaRay recordings were analyzed using CARTOFINDER. Focal activation or "region of interest" (ROI) was defined as more than or equal to 2 consecutive focal activations with one electrode leading relative to its neighbors with QS morphology on the unipolar electrogram. ROI was validated in AT. AF patients were mapped to (1) look for evidence of focal activations on wavefront maps, (2) evaluate whether these were detected as ROI on basket recordings, and (3) whether these sites could be identified on sequential PentaRay recordings.

RESULTS

ROIs were identified in five focal ATs but none of 16 reentrant ATs. Twenty-eight AF patients had 35 focal drivers identified from basket wavefront maps with an ablation response in all (16 cycle length slowing and 19 AF termination). Thirty focal activations were detected on basket ROI maps (86%). Twenty-three of 28 patients had sequential PentaRay mapping and 22 of 30 focal drivers in these patients (73%) were identified as ROI. These drivers had greater temporal stability (3.6 ± 0.6 vs 2.7 ± 0.6; P < 0.001), higher recurrence rate (12.4 ± 2.7 vs 7.2 ± 0.9; P < 0.001), and more frequently were associated with AF termination ( P < 0.001) compared with those not identified as ROI.

CONCLUSIONS

Focal activations can be detected in AF using sequential recordings. The ablation response at focal sources suggests they may be viable therapeutic targets.

Catheter ablation of atrial fibrillation in patients with hypertrophic cardiomyopathy: a European observational multicentre study

AIMS

Atrial fibrillation (AF) is common in hypertrophic cardiomyopathy (HCM). Data on the efficacy of catheter ablation of AF in HCM patients are sparse.

METHODS AND RESULTS

Observational multicentre study in 137 HCM patients (mean age 55.0 ± 13.4, 29.1% female; 225 ablation procedures). We investigated (i) the efficacy of catheter ablation for AF beyond the initial 12 months; (ii) the available risk scores, stratification schemes and genotype as potential predictors of arrhythmia relapse, and (iii) the impact of cryoballoon vs. radiofrequency in procedural outcomes. Mean follow-up was 43.8 ± 37.0 months. Recurrences after the initial 12-month period post-ablation were frequent, and 24 months after the index procedure, nearly all patients with persistent AF had relapsed, and only 40% of those with paroxysmal AF remained free from arrhythmia recurrence. The APPLE score demonstrated a modest discriminative capacity for AF relapse post-ablation (c-statistic 0.63, 95% CI 0.52-0.75; P = 0.022), while the risk stratification schemes for sudden death did not. On multivariable analysis, left atrium diameter and LV apical aneurysm were independent predictors of recurrence. Fifty-eight patients were genotyped; arrhythmia-free survival was similar among subjects with different gene mutations. Rate of procedural complications was high (9.3%), although reducing over time. Outcome for cryoballoon and radiofrequency ablation was comparable.

CONCLUSION

Very late AF relapses post-ablation is common in HCM patients, especially in those with persistent AF. Left atrium size, LV apical aneurysm, and the APPLE score might contribute to identify subjects at higher risk of arrhythmia recurrence. First-time cryoballoon is comparable with radiofrequency ablation.

Comparison of robotic and manual persistent AF ablation using catheter contact force sensing: an international multicenter registry study

BACKGROUND

Catheter-based contact force sensing (CFS) technology gives detailed information regarding contact between the catheter tip and myocardium. This may result in more effective ablation procedures. The primary objective of this study was comparison of remote robotic navigation (RRN) and Manual CFS ablation. The secondary objective was to compare CFS with non-CFS ablation for both navigation modes.

METHODS

Prospective registries of consecutive cases undergoing their first ablation for persistent atrial fibrillation (AF) from six hospitals in the United Kingdom and South Africa were analyzed: 50 Manual/CFS and 50 RRN/CFS cases were included. Historical control non-CFS ablation patients were matched by propensity score, giving a total 200 patient cohort.

RESULTS

RRN/CFS was associated with improved single procedure 1-year success rates (64% vs 36%, P = 0.01) and shorter fluoroscopy times (41% reduction, P < 0.0005) than Manual/CFS ablation, without any difference in procedure times (P = 0.8). The mean contact force was higher in RRN/CFS than Manual/CFS cases (16 [15-18 g] vs 13 [12-15 g], respectively, P = 0.003). Compared with non-CFS historical controls, CFS cases had higher 1-year success rates for RRN (64% vs 36%, P = 0.01), but not Manual ablation (36% vs 38%, P = 1). Procedure times were reduced for CFS cases (20%, P < 0.005 both navigation modes), as were fluoroscopy times (Manual: 43%, RRN 83%, P < 0.005 for both). There were no differences in rates of major or minor complications for either comparison (P > 0.5).

CONCLUSIONS

A combination of RRN and CFS is associated with improved success rates at 1 year and fluoroscopy times for persistent AF ablation, compared with Manual ablation and non-CFS RRN ablation.

Structural remodeling and conduction velocity dynamics in the human left atrium: Relationship with reentrant mechanisms sustaining atrial fibrillation

Background

Rate-dependent conduction velocity (CV) slowing is associated with atrial fibrillation (AF) initiation and reentrant mechanisms.

Objective

The purpose of this study was to assess the relationship between bipolar voltage, CV dynamics, and AF drivers.

Methods

Patients undergoing catheter ablation for persistent AF (<24 months) were enrolled. Unipolar electrograms were recorded with a 64-pole basket catheter during atrial pacing at 4 pacing intervals (PIs) during sinus rhythm. CVs were measured between pole pairs along the wavefront path and correlated with underlying bipolar voltage. CV dynamics within low-voltage zones (LVZs <0.5 mV) were compared to those of non-LVZs (≥0.5 mV) and were correlated to driver sites mapped using CARTOFINDER (Biosense Webster).

Results

Eighteen patients were included (age 62 ± 10 years). Mean CV at 600 ms was 1.59 ± 0.13 m/s in non-LVZs vs 0.98 ± 0.23 m/s in LVZs (P <.001). CV decreased incrementally over all 4 PIs in LVZs, whereas in non-LVZs a substantial decrease in CV was only seen between PIs 300–250 ms (0.59 ± 0.09 m/s; P <.001). Rate-dependent CV slowing sites measurements, defined as exhibiting CV reduction ≥20% more than the mean CV reduction seen between PIs 600–250 ms for that voltage zone, were predominantly in LVZs (0.2–0.5 mV; 75.6% ± 15.5%; P <.001). Confirmed rotational drivers were mapped to these sites in 94.1% of cases (sensitivity 94.1%, 95% CI 71.3%–99.9%; specificity 77.9%, 95% CI 74.9%–80.7%).

Conclusion

CV dynamics are determined largely by the extent of remodeling. Rate-dependent CV slowing sites are predominantly confined to LVZs (0.2–0.5 mV), and the resultant CV heterogeneity may promote driver formation in AF.

Transseptal puncture for left atrial ablation: risk factors for cardiac tamponade and a proposed causative classification system

Aims

Cardiac tamponade is a high morbidity complication of transseptal puncture (TSP). We examined the associations of TSP‐related cardiac tamponade (TRCT) for all patients undergoing left atrial ablation at our center from 2016 to 2020.

Methods and Results

Patient and procedural variables were extracted retrospectively. Cases of cardiac tamponade were scrutinized to adjudicate TSP culpability. Adjusted multivariate analysis examined predictors of TRCT. A total of 3239 consecutive TSPs were performed; cardiac tamponade occurred in 51 patients (incidence: 1.6%) and was adjudicated as TSP‐related in 35 (incidence: 1.1%; 68.6% of all tamponades). Patients of above‐median age [odds ratio (OR): 2.4 (1.19–4.2), p = .006] and those undergoing re‐do procedures [OR: 1.95 (1.29–3.43, p = .042] were at higher risk of TRCT. Of the operator‐dependent variables, choice of transseptal needle (Endrys vs. Brockenbrough, p > .1) or puncture sheath (Swartz vs. Mullins vs. Agilis vs. Vizigo vs. Cryosheath, all p > .1) did not predict TRCT. Adjusting for operator, equipment and demographics, failure to cross the septum first pass increased TRCT risk [OR: 4.42 (2.45–8.2), p = .001], whilst top quartile operator experience [OR: 0.4 (0.17–0.85), p = .002], transoesophageal echocardiogram [TOE prevalence: 26%, OR: 0.51 (0.11–0.94), p = .023], and use of the SafeSept transseptal guidewire [OR: 0.22 (0.08–0.62), p = .001] reduced TRCT risk. An increase in transseptal guidewire use over time (2016: 15.6%, 2020: 60.2%) correlated with an annual reduction in TRCT (R² = 0.72, p < .001) and was associated with a relative risk reduction of 70%.

Conclusions

During left atrial ablation, the risk of TRCT was reduced by operator experience, TOE‐guidance, and use of a transseptal guidewire, and was increased by patient age, re‐do procedures, and failure to cross the septum first pass.