Specific noninvasive signal processing was applied to identify drivers in distinct categories of persistent atrial fibrillation (AF).
In 103 consecutive patients with persistent AF, accurate biatrial ...geometry relative to an array of 252 body surface electrodes was obtained from a noncontrast computed tomography scan. The reconstructed unipolar AF electrograms acquired at bedside from multiple windows (duration, 9±1 s) were signal processed to identify the drivers (focal or reentrant activity) and their cumulative density map. The driver domains were catheter ablated by using AF termination as the procedural end point in comparison with the stepwise-ablation control group. The maps showed incessantly changing beat-to-beat wave fronts and varying spatiotemporal behavior of driver activities. Reentries were not sustained (median, 2.6 rotations lasting 449±89 ms), meandered substantially but recurred repetitively in the same region. In total, 4720 drivers were identified in 103 patients: 3802 (80.5%) reentries and 918 (19.5%) focal breakthroughs; most of them colocalized. Of these, 69% reentries and 71% foci were in the left atrium. Driver ablation alone terminated 75% and 15% of persistent and long-lasting AF, respectively. The number of targeted driver regions increased with the duration of continuous AF: 2 in patients presenting in sinus rhythm, 3 in AF lasting 1 to 3 months, 4 in AF lasting 4 to 6 months, and 6 in AF lasting longer. The termination rate sharply declined after 6 months. The mean radiofrequency delivery to AF termination was 28±17 minutes versus 65±33 minutes in the control group (P<0.0001). At 12 months, 85% patients with AF termination were free from AF, similar to the control population (87%,); P=not significant.
Persistent AF in early months is maintained predominantly by drivers clustered in a few regions, most of them being unstable reentries.
Noninvasive Panoramic Mapping of Human Atrial Fibrillation Mechanisms
Introduction
Recent developments in body surface mapping and computer processing have allowed noninvasive mapping of atrial ...activation responsible for various cardiac arrhythmias with increasingly greater resolution. We developed specific algorithms to identify localized sources and atrial propagation occurring simultaneously during ongoing atrial fibrillation (AF).
Methods and Results
We report the feasibility of noninvasive panoramic mapping of human AF mechanisms and its validation by successful ablation. We used a commercially available mapping system using an array of 252 body surface electrodes and noncontrast thoracic CT scan to obtain high‐resolution images of the biatrial geometry and the relative electrode positions. On the surface unipolar electrograms acquired during AF we developed specific signal‐analysis process combining filtering, wavelet transform, and phase mapping. At least 5 windows with spontaneous, long ventricular pauses were selected for mapping. The incidence, location and characteristics of localized sources (foci and rotors) were assessed on the cumulative duration of all recorded windows.
In a patient with paroxysmal AF, noninvasive maps showed multiple single or repetitive discharges from 3 pulmonary veins (PVs), a rotor meandering along the right venous ostia, and their mutual interplay. All areas outside the left posterior wall were passively activated. AF terminated during isolation of right PV.
In a patient with persistent AF for 7 months, a rotor was identified recurrently, drifting in the left atrial inferior and posterior wall and in the roof. It was not stationary for more than 2 rotations. The right atrial free wall was activated over the Bachman's bundle by a passive wavefront propagating in a counterclockwise pattern. Ablation at the rotor locations abruptly converted AF into atrial tachycardia after 10 minutes of radiofrequency application. Further mapping and ablation confirmed a counterclockwise cavotricuspid isthmus—dependent flutter.
Conclusions
This report demonstrates the feasibility of noninvasive panoramic mapping of AF in identifying active sources, which include unstable rotors and PV foci, and its validation by ablation results.
Risk stratification in Brugada syndrome (BS) remains controversial. The time interval between the peak and the end of the T wave (Tpe interval), a marker of transmural dispersion of repolarization, ...has been linked to malignant ventricular arrhythmias in various settings but leads to discordant results in BS.
We study the correlation of the Tpe interval with arrhythmic events in a large cohort of patients with BS.
A total of 325 consecutive patients with BS (mean age 47±13 years, 259 men-80%) with spontaneous (n=143, 44%) or drug-induced (n=182, 56%) type 1 electrocardiogram were retrospectively included. 235 were asymptomatic (70%), 80 presented with unexplained syncope (22%), and 10 presented with sudden death (SD) or appropriate implantable cardioverter-defibrillator therapy (AT) (8%) at diagnosis or over a mean follow-up of 48 ± 34 months. The Tpe interval was calculated as the difference between the QT interval and the QT peak interval as measured in each of the precordial leads.
The Tpe interval from lead V1 to lead V4, maximum value of the Tpe interval (max Tpe), and Tpe dispersion in all precordial leads were significantly higher in patients with SD/AT or in patients with syncope than in asymptomatic patients (P < .001). A max Tpe of ≥100 ms was present in 47 of 226 asymptomatic patients (21%), in 48 of 73 patients with syncope (66%), and in 22 of 26 patients with SD/AT (85%) (P < .0001). In multivariate analysis, a max Tpe of ≥100 ms was independently related to arrhythmic events (odds ratio 9.61; 95% confidence interval 3.13-29.41; P < .0001).
The Tpe interval in the precordial leads is highly related to malignant ventricular arrhythmias in this large cohort of patients with BS. This simple electrocardiographic parameter could be used to refine risk stratification.
Treatment options for high-risk Brugada syndrome (BrS) with recurrent ventricular fibrillation (VF) are limited. Catheter ablation is increasingly performed but a large study with long-term outcome ...data is lacking. We report the results of the multicenter, international BRAVO (Brugada Ablation of VF Substrate Ongoing Registry) for treatment of high-risk symptomatic BrS.
We enrolled 159 patients (median age 42 years; 156 male) with BrS and spontaneous VF in BRAVO; 43 (27%) of them had BrS and early repolarization pattern. All but 5 had an implantable cardioverter-defibrillator for cardiac arrest (n=125) or syncope (n=34). A total of 140 (88%) had experienced numerous implantable cardioverter-defibrillator shocks for spontaneous VF before ablation. All patients underwent a percutaneous epicardial substrate ablation with electroanatomical mapping except for 8 who underwent open-thoracotomy ablation.
In all patients, VF/BrS substrates were recorded in the epicardial surface of the right ventricular outflow tract; 45 (29%) patients also had an arrhythmic substrate in the inferior right ventricular epicardium and 3 in the posterior left ventricular epicardium. After a single ablation procedure, 128 of 159 (81%) patients remained free of VF recurrence; this number increased to 153 (96%) after a repeated procedure (mean 1.2±0.5 procedures; median=1), with a mean follow-up period of 48±29 months from the last ablation. VF burden and frequency of shocks decreased significantly from 1.1±2.1 per month before ablation to 0.003±0.14 per month after the last ablation (
<0.0001). The Kaplan-Meier VF-free survival beyond 5 years after the last ablation was 95%. The only variable associated with a VF-free outcome in multivariable analysis was normalization of the type 1 Brugada ECG, both with and without sodium-channel blockade, after the ablation (hazard ratio, 0.078 95% CI, 0.008 to 0.753;
=0.0274). There were no arrhythmic or cardiac deaths. Complications included hemopericardium in 4 (2.5%) patients.
Ablation treatment is safe and highly effective in preventing VF recurrence in high-risk BrS. Prospective studies are needed to determine whether it can be an alternative treatment to implantable cardioverter-defibrillator implantation for selected patients with BrS.
URL: https://www.
gov; Unique identifier: NCT04420078.
Atrial tachycardias (ATs) are often seen in the context of atrial fibrillation (AF) ablation.
To evaluate the role of the Marshall bundle (MB) network in left atrial (LA) ATs using high-density ...3-dimensional mapping.
A total of 199 ATs were mapped in 140 patients (112 male, mean age: 61.8 years); 133 (66.8%) were macroreentrant and 66 (33.2%) were scar-related reentry circuits. MB-dependent ATs were suggested by activation mapping analysis and confirmed with entrainment along the circuit.
The MB network participated in 60 (30.2%) reentrant ATs: 31 perimitral ATs (PMATs) and 29 localized reentry circuits. Of 60 MB-related ATs, 49 (81.6%) terminated with radiofrequency (RF) ablation: 44 (73.3%) at the MB-LA junction and 5 (8.3%) at the MB-coronary sinus (CS) junction, while 9 (15%) terminated after 2.5-5 cc of ethanol infusion inside the vein of Marshall (VOM). Of the 31 PMATs, 17 (54.8%) terminated at the MB-LA junction, 5 (16.1%) at the MB-CS junction, and 7 (22.6%) with ethanol infusion. Of the 29 localized reentry circuits using the MB, 27 (93.1%) terminated at the MB-LA junction, none at the MB-CS junction, and 2 (6.9%) after ethanol infusion. Recurrences were mostly observed after RF ablation (18 of 37 patients, 49%) compared to ethanol infusion (1 of 9 patients, 11%) (P = .06).
MB reentrant ATs accounted for up to 30.2% of the left ATs after AF ablation. Ablation of the MB-LA or CS-MB connections or ethanol infusion inside the VOM is required to treat these arrhythmias.
This study aimed to determine 5-year efficacy of catheter ablation for persistent atrial fibrillation (AF) using AF termination as a procedural end point.
One hundred fifty patients (57±10 years) ...underwent persistent AF ablation using a stepwise ablation approach (pulmonary vein isolation, electrogram-guided, and linear ablation) with the desired procedural end point being AF termination. Repeat ablation was performed for recurrent AF or atrial tachycardia. AF was terminated by ablation in 120 patients (80%). Arrhythmia-free survival rates after a single procedure were 35.3%±3.9%, 28.0%±3.7%, and 16.8%±3.2% at 1, 2, and 5 years, respectively. Arrhythmia-free survival rates after the last procedure (mean 2.1±1.0 procedures) were 89.7%±2.5%, 79.8%±3.4%, and 62.9%±4.5%, at 1, 2, and 5 years, respectively. During a median follow-up of 58 (interquartile range, 43-73) months after the last ablation procedure, 97 of 150 (64.7%) patients remained in sinus rhythm without antiarrhythmic drugs. Another 14 (9.3%) patients maintained sinus rhythm after reinitiation of antiarrhythmic drugs, and an additional 15 (10.0%) patients regressed to paroxysmal recurrences only. Failure to terminate AF during the index procedure (hazard ratio 3.831; 95% confidence interval, 2.070-7.143; P<0.001), left atrial diameter≥50 mm (hazard ratio 2.083; 95% confidence interval, 1.078-4.016; P=0.03), continuous AF duration≥18 months (hazard ratio 1.984; 95% confidence interval, 1.024-3.846; P<0.04), and structural heart disease (hazard ratio 1.874; 95% confidence interval, 1.037-3.388; P=0.04) predicted arrhythmia recurrence.
In patients with persistent AF, an ablation strategy aiming at AF termination is associated with freedom from arrhythmia recurrence in the majority of patients over a 5-year follow-up period. Procedural AF nontermination and specific baseline factors predict long-term outcome after ablation.
Abstract
Aims
Mapping data of human ventricular fibrillation (VF) are limited. We performed detailed mapping of the activities underlying the onset of VF and targeted ablation in patients with ...structural cardiac abnormalities.
Methods and results
We evaluated 54 patients (50 ± 16 years) with VF in the setting of ischaemic (n = 15), hypertrophic (n = 8) or dilated cardiomyopathy (n = 12), or Brugada syndrome (n = 19). Ventricular fibrillation was mapped using body-surface mapping to identify driver (reentrant and focal) areas and invasive Purkinje mapping. Purkinje drivers were defined as Purkinje activities faster than the local ventricular rate. Structural substrate was delineated by electrogram criteria and by imaging. Catheter ablation was performed in 41 patients with recurrent VF. Sixty-one episodes of spontaneous (n = 10) or induced (n = 51) VF were mapped. Ventricular fibrillation was organized for the initial 5.0 ± 3.4 s, exhibiting large wavefronts with similar cycle lengths (CLs) across both ventricles (197 ± 23 vs. 196 ± 22 ms, P = 0.9). Most drivers (81%) originated from areas associated with the structural substrate. The Purkinje system was implicated as a trigger or driver in 43% of patients with cardiomyopathy. The transition to disorganized VF was associated with the acceleration of initial reentrant activities (CL shortening from 187 ± 17 to 175 ± 20 ms, P < 0.001), then spatial dissemination of drivers. Purkinje and substrate ablation resulted in the reduction of VF recurrences from a pre-procedural median of seven episodes interquartile range (IQR) 4–16 to 0 episode (IQR 0–2) (P < 0.001) at 56 ± 30 months.
Conclusions
The onset of human VF is sustained by activities originating from Purkinje and structural substrate, before spreading throughout the ventricles to establish disorganized VF. Targeted ablation results in effective reduction of VF burden.
Key question
The initial phase of human ventricular fibrillation (VF) is critical as it involves the primary activities leading to sustained VF and arrhythmic sudden death. The origin of such activities is unknown.
Key finding
Body-surface mapping shows that most drivers (≈80%) during the initial VF phase originate from electrophysiologically defined structural substrates. Repetitive Purkinje activities can be elicited by programmed stimulation and are implicated as drivers in 37% of cardiomyopathy patients.
Take-home message
The onset of human VF is mostly associated with activities from the Purkinje network and structural substrate, before spreading throughout the ventricles to establish sustained VF. Targeted ablation reduces or eliminates VF recurrence.
Structured Graphical Abstract
Structured Graphical Abstract
Ventricular fibrillation (VF) onset in humans—Purkinje and structural substrate govern the transition from trigger to disorganized VF. Schematic view of initial VF activities in patients with cardiac structural abnormalities. The upper panel shows an electrocardiogram of spontaneous VF onset in a patient with a prior history of myocardial infarction. The three illustrations show the sequence of trigger, initial organized VF, and disorganized VF. The trigger is shown as a red star close to the structural substrate (mottled white area). Initial VF activities are represented as localized waves generated from the ventricular or Purkinje substrate. Then the acceleration of activities in parallel with previously described changes (reduction in action potential duration, Ca handling…) leads to dissemination of activities and VF disorganization.
Anatomic macroreentrant atrial tachycardias (MATs) are conventionally reported to depend on the cavotricuspid isthmus, the mitral isthmus, or the left atrial roof, and are commonly seen following ...catheter ablation for atrial fibrillation.
To define the precise circuits of anatomic MAT with ultrahigh-resolution mapping.
In 57 patients (mean age, 62 years; 10 female) who developed ≥1 anatomic MAT, we analyzed 88 MAT circuits including 16 peritricuspid, 42 perimitral, and 30 roof-dependent circuits, using high-density mapping and entrainment.
Of 16 peritricuspid atrial tachycardias (ATs), 8 (50.0%) showed a circuit not limited to the tricuspid annulus. However, cavotricuspid isthmus ablation terminated the tachycardia in all patients. Similarly, 26 of 42 perimitral ATs (61.9%) showed a circuit not limited to the mitral annulus, and a low-voltage zone <0.1 mV around the mitral annulus was associated with nontypical perimitral ATs (P < .0001). The practical isthmus was not in the mitral isthmus in 13 of these 26 perimitral ATs (50%). Finally, 22 of 30 roof-dependent ATs (73.3%) had a circuit not rotating around both pairs of pulmonary veins. Brief assessment of the activation direction on the posterior wall in relation to that on the septal, anterior, and lateral wall helped deduce the circuit of roof-dependent AT in 27 of 30 (90.0%). Practical isthmus was not in the roof in 8 of 22 (36.4%). Practical isthmuses mapped with the system were significantly shorter than the usual anatomic isthmuses (16.1 ± 8.2 mm vs 33.7 ± 10.4 mm) (P < .0001).
High-density mapping successfully identified the precise circuits and the practical isthmus of anatomic MATs in patients with prior atrial fibrillation ablation.
Introduction
Successful catheter ablation is limited by both poor spatial resolution of abnormal local signals and inability to deliver an effective lesion due to poor tissue contact. We report first ...worldwide use of the Intellanav MiFi OI catheter (Boston Scientific), providing ultra‐high density mapping and incorporating a “DirectSense” algorithm to measure local tissue impedance (LI).
Methods and results
31 patients (65±6 years, 20 male) underwent ablation. LI from the catheter, generator impedance (GI) and maximum electrogram amplitude were recorded in the blood pool, and in regions from healthy to dense scar before, during and after ablation. The catheter demonstrated clear nearfield signal where standard bipolar recordings included farfield signal. LI was lower in dense scar than either healthy tissue or blood pool, and demonstrated an exponential relationship with maximum electrogram amplitude.
Maximum LI drop on ablation linearly correlated with initial LI. The median LI drop for successful lesions, resulting in lack of local tissue capture, was 16.0Ω (12.1–19.8 Ω) for LV and 14.6 Ω (10.0–18.3 Ω) for LA, which was larger than for unsuccessful lesions (LV: 9.4 Ω 5.4–15.6 Ω P = 0.001; LA: 6.8 Ω 4.7–13.0 Ω, P = 0.049). LI percentage drop was also significantly larger for successful than unsuccessful lesions (LV: 17.1 Ω 14.0–19.6 Ω vs. 10.6 Ω (7.1–16.5 Ω) P = 0.002; LA: 14.2 Ω 10.8‐19.5 Ω vs. 7.5Ω 5.1–11.0 Ω, P = 0.005).
Conclusion
This novel catheter gives reproducible recordings of local impedance, which are dependent on scar level. Absolute LI drop, and also percentage drop, on ablation may give an indication of tissue contact and subsequent effective lesion formation.
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