Local abnormal ventricular activity detection in scar-related VT: Microelectrode versus conventional bipolar electrode.

BACKGROUND: Conventional bipolar electrodes (CBE) may be suboptimal to detect local abnormal ventricular activities (LAVAs). Microelectrodes (ME) may improve the detection of LAVAs. This study sought to elucidate the detectability of LAVAs using ME compared with CBE in patients with scar-related ventricular tachycardia (VT). METHODS: We included consecutive patients with structural heart disease who underwent radiofrequency catheter ablation for scar-related VT using either of the following catheters equipped with ME: QDOTTM or IntellaTip MIFITM. Detection field of LAVA potentials were classified as three types: Type 1 (both CBE and ME detected LAVA), Type 2 (CBE did not detect LAVA while ME did), and Type 3 (CBE detected LAVA while ME did not). RESULTS: In 16 patients (68 ± 16 years; 14 males), 260 LAVAs electrograms (QDOT = 72; MIFI = 188) were analyzed. Type 1, type 2, and type 3 detections were 70.8% (QDOT, 69.4%; MIFI, 71.3%), 20.0% (QDOT, 23.6%; MIFI, 18.6%) and 9.2% (QDOT, 6.9%; MIFI, 10.1%), respectively. The LAVAs amplitudes detected by ME were higher than those detected by CBE in both catheters (QDOT: ME 0.79 ± 0.50 mV vs. CBE 0.41 ± 0.42 mV, p = .001; MIFI: ME 0.73 ± 0.64 mV vs. CBE 0.38 ± 0.36 mV, p < .001). CONCLUSIONS: ME allow to identify 20% of LAVAs missed by CBE. ME showed higher amplitude LAVAs than CBE. However, 9.2% of LAVAs can still be missed by ME.

High-Power (40-50 W) Radiofrequency Ablation Guided by Unipolar Signal Modification for Pulmonary Vein Isolation: Experimental Findings and Clinical Results.

Background Although proposed to facilitate pulmonary vein isolation (PVI), high-power ablation may favor extracardiac damage. Negative component abolition of the unipolar signal reflects lesion transmurality. The present study sought to evaluate the safety and efficacy of high-power ablation using unipolar signal modification as a local end point. Methods High power and standard power were compared in 4 swine and 100 consecutive patients referred for PVI. The first 50 patients were included in the control group (25-30 W) and the last 50 patients in the study group (40-50 W). Atrial radiofrequency applications were stopped 2 s (study group and swine) or 5 s (control group) after unipolar signal modification. Ventricular radiofrequency applications of 500 J (25 W·20 s versus 50 W·10 s) were performed at the swine epicardium. Results Swine gross necropsy did not show any extracardiac damage related to atrial lesions. At equal energy of 500 J, 50 W lesions were deeper (3±0.9 versus 2.6±1.1 mm; P=0.03) and wider (6.2±2 versus 5±2.3 mm; P=0.006) than 25 W lesions. No complications occurred during the clinical study, whatever the power output used for PVI. For a similar sinus rhythm maintenance at 12 months (90% versus 88%; P=0.75), the study group displayed higher first-pass PVI (92% versus 73%; P<0.001), lower acute pulmonary vein reconnection (2% versus 17%; P<0.001), reduced procedure time (73.1±18.2 versus 107.4±21.2 min; P<0.001), and ablation time (13±2.9 versus 30.3±8.8 min; P<0.001). Conclusions High-power PVI guided by unipolar signal modification safely decreases procedural burden while ensuring robust 12-month outcomes.

Complexity and Distribution of Drivers in Relation to Duration of Persistent Atrial Fibrillation.

BACKGROUND: The underlying mechanisms sustaining human persistent atrial fibrillation (PsAF) is poorly understood. OBJECTIVES: This study sought to investigate the complexity and distribution of AF drivers in PsAF of varying durations. METHODS: Of 135 consecutive patients with PsAF, 105 patients referred for de novo ablation of PsAF were prospectively recruited. Patients were divided into 3 groups according to AF duration: PsAF presenting in sinus rhythm (AF induced), PsAF <12 months, and PsAF >12 months. Patients wore a 252-electrode vest for body surface mapping. Localized drivers (re-entrant or focal) were identified using phase-mapping algorithms. RESULTS: In this patient cohort, the most prominent re-entrant driver regions included the pulmonary vein (PV) regions and inferoposterior left atrial wall. Focal drivers were observed in 1 or both PV regions in 75% of patients. Comparing between the 3 groups, with longer AF duration AF complexity increased, reflected by increased number of re-entrant rotations (p < 0.05), number of re-entrant rotations and focal events (p < 0.05), and number of regions harboring re-entrant (p < 0.01) and focal (p < 0.05) drivers. With increased AF duration, a higher proportion of patients had multiple extra-PV driver regions, specifically in the inferoposterior left atrium (p < 0.01), superior right atrium (p < 0.05), and inferior right atrium (p < 0.05). Procedural AF termination was achieved in 70% of patients, but decreased with longer AF duration. CONCLUSIONS: The complexity of AF drivers increases with prolonged AF duration. Re-entrant and focal drivers are predominantly located in the PV antral and adjacent regions. However, with longer AF duration, multiple drivers are distributed at extra-PV sites. AF termination rate declines as patients progress to longstanding PsAF, underscoring the importance of early intervention.

Persistent Atrial Fibrillation From the Onset: A Specific Subgroup of Patients With Biatrial Substrate Involvement and Poorer Clinical Outcome.

OBJECTIVES: This study sought to characterize the clinical characteristics, atrial substrate, and prognosis in a subgroup of patients with persistent atrial fibrillation (AF) from the onset (PsAFonset). BACKGROUND: Patients with AF frequently progress from trigger-driven paroxysmal arrhythmias to substrate-dependent persistent arrhythmias. METHODS: Patients referred for persistent AF (PsAF) ablation were enrolled from 3 centers. Consecutive patients with PsAFonset (n = 129) were compared with patients with PsAF that progressed from paroxysmal AF (n = 231). In addition, 90 patients (30 patients with PsAFonset and 60 control subjects) were studied with noninvasive mapping to characterize the AF drivers. The degree of fractionation and endocardial voltages were assessed invasively. RESULTS: Patients with PsAFonset were younger (p = 0.047) and more obese (p < 0.001); there were more men (p = 0.034), more patients with hypertension (p = 0.044), and these patients had larger left (p < 0.05) and right atria (p < 0.05). Baseline AF cycle length was shorter in the PsAFonset group (p < 0.01); the degree of fractionation was higher (p < 0.001 for both atria), and the endocardial voltage was lower (p < 0.05 for both atria). Patients with PsAFonset had higher a number of re-entrant driver regions (p < 0.001) and extrapulmonary vein regions that had re-entrant drivers (p < 0.05), whereas control subjects displayed more focal driver regions (p = 0.029). The acute AF termination rate was lower in the PsAFonset group (42% vs. 81%; p < 0.001). During a mean follow-up of 17 ± 11 months from the last procedure, patients with PsAFonset had significantly higher AF, atrial tachycardia (AT), and AF/AT recurrence rates (p < 0.01). CONCLUSIONS: Patients with PsAFonset represent a distinct subgroup defined by specific demographics, underlying diffuse biatrial substrate disease, and worse clinical outcome. The findings highlight the importance of defining criteria for early detection of atrial substrate disease.

Computation and projection of spiral wave trajectories during atrial fibrillation: a computational study.

To show how atrial fibrillation rotor activity on the heart surface manifests as phase on the torso, fibrillation was induced on a geometrically accurate computer model of the human atria. The Hilbert transform, time embedding, and filament detection were compared. Electrical activity on the epicardium was used to compute potentials on different surfaces from the atria to the torso. The Hilbert transform produces erroneous phase when pacing for longer than the action potential duration. The number of phase singularities, frequency content, and the dominant frequency decreased with distance from the heart, except for the convex hull.

Quantification of the transmural dynamics of atrial fibrillation by simultaneous endocardial and epicardial optical mapping in an acute sheep model.

BACKGROUND: Therapy strategies for atrial fibrillation based on electric characterization are becoming viable personalized medicine approaches to treat a notoriously difficult disease. In light of these approaches that rely on high-density surface mapping, this study aims to evaluate the presence of 3-dimensional electric substrate variations within the transmural wall during acute episodes of atrial fibrillation. METHODS AND RESULTS: Optical signals were simultaneously acquired from the epicardial and endocardial tissue during acute fibrillation in ovine isolated left atria. Dominant frequency, regularity index, propagation angles, and phase dynamics were assessed and correlated across imaging planes to gauge the synchrony of the activation patterns compared with paced rhythms. Static frequency parameters were well correlated spatially between the endocardium and the epicardium (dominant frequency, 0.79 ± 0.06 and regularity index, 0.93 ± 0.009). However, dynamic tracking of propagation vectors and phase singularity trajectories revealed discordant activity across the transmural wall. The absolute value of the difference in the number, spatial stability, and temporal stability of phase singularities between the epicardial and the endocardial planes was significantly >0 with a median difference of 1.0, 9.27%, and 19.75%, respectively. The number of wavefronts with respect to time was significantly less correlated and the difference in propagation angle was significantly larger in fibrillation compared with paced rhythms. CONCLUSIONS: Atrial fibrillation substrates are dynamic 3-dimensional structures with a range of discordance between the epicardial and the endocardial tissue. The results of this study suggest that transmural propagation may play a role in atrial fibrillation maintenance mechanisms.

Detailed analysis of ventricular activation sequences during right ventricular apical pacing and left bundle branch block and the potential implications for cardiac resynchronization therapy.

BACKGROUND: Left bundle branch block (LBBB) leads to prolonged left ventricular (LV) total activation time (TAT) and ventricular electrical uncoupling (VEU; mean LV activation time minus mean right ventricular [RV] activation time); both have been shown to be preferential targets for cardiac resynchronization therapy (CRT). Whether right ventricular apical pacing (RVAP) produces similar ventricular activation patterns has not been well studied. OBJECTIVE: The purpose of this study was to compare electrical ventricular activation patterns during RVAP and LBBB. METHODS: We performed ECG mapping during sinus rhythm, RVAP, and CRT in 24 patients with LBBB. RESULTS: We observed differences in the electrical activation pattern with RVAP compared to LBBB. During LBBB, RV activation occurred rapidly; in contrast, RV activation was prolonged during RVAP (46 ± 21 ms vs 69 ± 17 ms, P <.001). There was no significant difference in LVTAT; however, differences in conduction pattern were observed. During LBBB, LV activation was circumferential, whereas with RVAP, LV activation proceeded from apex to base. Differences in the number, size, and orientation of lines of slow conduction also were observed. With LBBB, VEU was nearly twice as long as during RVAP (73 ± 12 ms vs 38 ± 21 ms, P <.001). CRT resulted in a greater reduction in VEU relative to LBBB activation (P <.001). CONCLUSION: RVAP produces significant differences in ventricular activation characteristics compared to LBBB. Significantly less VEU occurs with RVAP, and as a result CRT produces a smaller relative reduction in VEU. This may explain the finding that CRT appears to be more effective in patients with LBBB than in those who were upgraded because of high percentages of RV pacing.

Driver domains in persistent atrial fibrillation.

BACKGROUND: Specific noninvasive signal processing was applied to identify drivers in distinct categories of persistent atrial fibrillation (AF). METHODS AND RESULTS: 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. CONCLUSIONS: Persistent AF in early months is maintained predominantly by drivers clustered in a few regions, most of them being unstable reentries.