Anterior mitral line in patients with persistent atrial fibrillation and anterior scar: A multicenter matched comparison-The MiLine study.

BACKGROUND: The benefit of an anterior mitral line (AML) in patients with persistent atrial fibrillation (AF) and anterior atrial scar undergoing ablation has never been investigated. OBJECTIVE: The purpose of this study was to evaluate the outcomes of AML in addition to standard treatment compared to standard treatment alone (no AML) in this subset of patients. METHODS: Patients with persistent AF and anterior low-voltage zone (LVZ) treated with AML in 3 centers were retrospectively enrolled. The patients were matched in 1:1 fashion with patients having persistent AF and anterior LVZ who underwent conventional ablation in the same centers. Matching parameters were age, LVZ burden, and repeated ablation. Primary endpoint was AF/atrial tachycardia (AT) recurrence. RESULTS: One hundred eight-six patients (age 66 ± 9 years; 34% women) were selected and divided into 2 matched groups. Bidirectional conduction block was achieved in 95% of AML. After median follow-up of 2 years, AF/AT recurrence occurred in 29% of the patients in the AML group vs 48% in the no AML group (log-rank P = .024). On Cox regression multivariate analysis, left atrial volume (hazard ratio [HR] 1.03; P = .006) and AML (HR 0.46; P = .003) were significantly associated with the primary endpoint. On univariate logistic regression, lower body mass index, older age, extensive anterior LVZ, and position of the left atrial activation breakthrough away from the AML were associated with first-pass AML block. CONCLUSION: In this retrospective matched analysis of patients with persistent AF and anterior scar, AML in addition to standard treatment was associated with improved AF/AT-free survival compared to standard treatment alone.

Low voltage zones detected by omnipolar Vmax map accurately identifies the potential atrial substrate and predicts the AF ablation outcome after PV isolation.

INTRODUCTION: The presence of bipolar low-voltage zone (LVZ) is a predictor of AF recurrence after PV isolation (PVI). However, changes of wavefront and bipole directions may cause different electrogram characteristics. We aimed to investigate whether using omnipolar maximum voltage (Vmax) map derived from high density (HD) Grid mapping catheter could assess LVZ and AF ablation outcome accurately. METHODS: Fifty paroxysmal AF patients (27 males, 57.8 ± 9.5 years old) who underwent 3D mapping guided PVI were enrolled. Left atrial voltage mapping during sinus rhythm before ablation was performed. The significant LVZ (<0.5 mV with area > 5 cm2) were defined as sites by omnipolar Vmax, bipolar HD wave map, conventional bipolar electrograms acquired from electrode pairs along to and across to the catheter shaft. The primary end point was the first documented recurrence of any AF during follow-ups. RESULTS: PVI was performed in all patients, and there were 2 patients (4%) who also received additional non-PV triggers ablation. After a follow-up of 11.4 ± 5.4 months, recurrence of AF occurred in 12 patients (24%). The presence of a significant LVZ was less detected by omnipolar Vmax map, compared to HD wave map (24.0% vs. 58.0%, p = 0.001). LVZ detected by omnipolar Vmax map independently predicted the AF recurrence (odds ratio 16.91; 95% CI, 3.17-90.10; p = 0.001). CONCLUSION: LVZ detected by omnipolar Vmax map accurately predicts the AF recurrence following ablation in paroxysmal AF, compared to conventional bipolar and HD wave maps, suggesting the omnipolar Vmax map can precisely define the atrial substrate property.

Extensive right atrial free wall low-voltage zone as the substrate for atrial fibrillation: successful ablation by scar homogenization.

AIMS: Prior studies have described a variety of mechanisms for atrial fibrillation (AF) originating in the right atrium (RA). In this study, we report a series of patients in whom an extensive right atrial free wall low-voltage zone (LVZ) served as the AF substrate. METHODS AND RESULTS: Five patients with a clinical syndrome of paroxysmal AF and atrial tachycardia (AT) underwent electrophysiologic evaluation. Five patients (3 M; age 52 ± 7 years) had symptomatic paroxysmal AF for (28 ± 17 months) not responsive to medical therapy. At the initial EP study, AT was inducible in four patients and was spontaneous in one patient. In all patients, tachycardia instability precluded detailed AT mapping. Sinus or pace maps indicated an extensive LVZ in the lateral RA trabeculated free wall which consisted of regions of low amplitude complex signals interspersed between electrically silent areas. Radiofrequency ablation aimed at rendering the LVZ electrical inert was successful in eliminating AF in four of five patients. At a follow-up of 28 ± 15 months, one patient had an isolated recurrence of AF. However, two patients required repeat ablation for recurrent AT. CONCLUSION: An extensive LVZ in the trabeculated RA free wall constitutes an unusual substrate for AF. These patients also demonstrate unstable ATs originating from the same zone. Radiofrequency ablation to render the low-voltage zone electrically inert is an effective strategy to manage AF and AT.

Electrophysiological findings during atrial fibrillation reablation: Extending from pulmonary vein reconnection to sequential bipolar voltage map information.

BACKGROUND: Left atrial substrate modification targeting low voltage zones (LVZ) is an ablation strategy that-in addition to pulmonary vein (PV) isolation-tries to eliminate arrhythmogenic mechanisms harbored in such tissue. Electrophysiological findings at reablation include (a) PV reconnection, (b) reconnection over previous substrate ablation, and (c) de-novo LVZ. OBJECTIVE: To study, prevalence and contribution of these arrhythmogenic electrophysiological entities in patients with atrial fibrillation (AF) recurrences. METHODS: Consecutive patients with highly symptomatic AF undergoing index and reablation were included (n = 113). In all patients' PV reconnection, reconnection over previous substrate ablation and spontaneous de-novo LVZ were quantitatively assessed and integrated into an individual reablation strategy. Follow-up was based on continuous device monitoring. RESULTS: At re-do procedure, 45 out of 113 (39.8%) patients showed PV reconnection as the only electrophysiological abnormality. Reconduction over previous lines was the only electrophysiological abnormality in 8 out of 113 (7.1%) patients. Spontaneous de-novo LVZ was the only electrophysiological abnormality in 12 out of 113 (10.6%) patients. Combined findings of PV reconnection, line reconduction, and/or spontaneous de-novo LVZ were seen in 40 out of 113 (35.4%) patients. No detectable electrophysiological abnormality was observed in 8 out of 113 (7.1%) patients. In univariate analysis, none of the tested electrophysiological characteristics independently predicted the outcome after re-do. CONCLUSIONS: In patients undergoing reablation, we could show that reconduction over previous substrate ablation as well as the development of new low voltage areas are frequent findings besides classical PV reconnection-without a clear leading cause for recurrences. These findings impact reablation strategies as well as the strategic focus during index procedures.

Dynamic Atrial Substrate During High-Density Mapping of Paroxysmal and Persistent AF: Implications for Substrate Ablation.

OBJECTIVES: This study sought to determine the impact of rate and direction on left atrial (LA) substrate. BACKGROUND: The extent to which substrate mapped in sinus rhythm varies according to cycle length and direction of wave front propagation is unknown. METHODS: A total of 73 consecutive patients with atrial fibrillation (AF) underwent electroanatomic LA mapping before pulmonary vein isolation using multipolar catheter during distal coronary sinus (CS) pacing at 600 ms and 300 ms. Additional maps were created during left superior pulmonary vein pacing at 300 ms. Bipolar voltage, conduction velocity (CV), and complex signals were determined. RESULTS: Mean age was 61 ± 9 years, 67% were men, and 53% had persistent AF. Global mean voltage was lower with CS pacing at 300 ms compared with 600 ms (1.56 ± 0.47 mV vs. 1.74 ± 0.48 mV; p < 0.001). This was seen in all LA segments. Global CV was reduced (30.4 ± 13.0 cm/s vs. 38.6 ± 14.0 cm/s; p < 0.001) with greater complex signals at 300 ms (8.9% vs. 5.3%; p < 0.005). Compared with CS pacing, left superior pulmonary vein pacing demonstrated highly regional changes with decreased voltage (1.04 ± 0.43 mV vs. 1.47 ± 0.53 mV; p = 0.01) and CV (24.4 ± 13.0 cm/s vs. 39.9 ± 16.6 cm/s; p = 0.008), and greater complex signals posteriorly. Longer AF duration in paroxysmal AF (p = 0.02) and shorter duration in persistent AF (p = 0.015) and left ventricular ejection fraction (p = 0.016) were independent predictors of voltage change. CONCLUSIONS: In patients with AF, variation in cycle length and direction of wave front activation produce both generalized and regional changes in voltage, CV, and complex fractionation, resulting in significant changes in substrate maps. This study highlights the potential limitations of static low-voltage maps to identify the AF ablation target zone.

Impact of low-voltage zones on the left atrial anterior wall on the reduction in the left atrial appendage flow velocity in persistent atrial fibrillation patients.

BACKGROUND: The reduction in the left atrial appendage (LAA) flow velocity is related to the presence of emboli in atrial fibrillation (AF) patients. The LAA is located on the left superior side of the left atrial (LA) anterior wall, and we investigated the relationship between the reduction in the LAA flow velocity (LAAFV) and low voltage zones (LVZs < 0.5 mV) on the LA anterior wall. METHODS: In 146 persistent AF patients, LAAFV measurements, by transesophageal echocardiography, and catheter ablation were performed. LA mapping was performed before ablation during sinus rhythm, and the locations of any anterior-LVZs were documented. RESULTS: Eighty-one patients had a documented LVZ on the LA anterior wall, and those with an LVZ had a significantly lower LAAFV compared to those without (anterior-LVZ(+) vs. anterior-LVZ(-) = 26 ± 11 vs. 34 ± 10 cm/s, p < 0.001), while no significant difference was observed when compared to the other LVZ regions. A low-LAAFV (≦ 20 cm/s) was observed in 36 patients, and the CHADS2-vasc score and existence of an anterior-LVZ were associated with a low-LAAFV. In patients with anterior-LVZs, the distance between the anterior-LVZ and LAA orifice correlated with a low LAAFV (r = 0.534, p < 0.001) as compared to the surface area of the anterior-LVZ (r = - 0.288, p = 0.009). CONCLUSIONS: In persistent AF patients, an LVZ on the LA anterior wall was associated with a low LAAFV. In addition, an anterior-LVZ located near the LAA orifice was further related to a reduction in the LAAFV.

The influence of the electrodes spacing of a mapping catheter on the atrial voltage substrate map.

BACKGROUND: Detailed substrate mapping is important for catheter ablation. However, the influence of the electrode spacing of the mapping catheter on the substrate map has not been well clarified. The aim of this study was to investigate the influence of the electrode spacing of the mapping catheter on the voltage of the substrate map. METHODS: Protocol 1: We recorded the local atrial potentials of the left atrium (LA) using the ablation catheter during sinus rhythm in six atrial fibrillation (AF) patients. The voltage of each atrial potential was compared between a close-bipolar (1-2 electrode) recording and wide-bipolar (1-4 electrode) recording. Protocol 2: Two voltage-maps of the LA were constructed separately using a 20-pole circular catheter and 10-pole circular catheter during sinus rhythm in 42 AF patients. The low voltage zone (LVZ) (<0.5mV) areas obtained by 2 voltage maps using the 10-pole and 20-pole circular catheters were compared. RESULTS: Protocol 1: The close-bipolar voltage of the local potentials was significantly smaller than that of the wide-bipolar voltages (0.76±0.39mV vs. 0.63±0.41mV, p<0.0001). Protocol 2: The size of the LVZ areas identified by the 10-pole and 20-pole catheters was 1.12±1.92cm2 (1.47±2.78%) and 8.30±7.80cm2 (8.83±8.32%), respectively (p<0.0001). CONCLUSIONS: The voltage of the local atrial potential using the close-bipolar catheter was significantly smaller than that using the wide-bipolar catheter. Care should be given to the electrode spacing of mapping catheters when analyzing the voltage of the atrial myocardial potentials.

Impact of the extent of low-voltage zone on outcomes after voltage-based catheter ablation for persistent atrial fibrillation.

BACKGROUND: Low-voltage zones (LVZs), as measured by electroanatomic mapping, are thought to be associated with fibrosis. We reported the efficacy of atrial fibrillation (AF) ablation aiming to homogenize left atrial (LA) LVZ. The purpose of this study was to evaluate the impact of LVZ extension outcomes after LVZ homogenization in patients with nonparoxysmal AF. METHODS: This prospective observational cohort study included 172 patients with nonparoxysmal AF undergoing their initial ablation. LVZ was defined as an area with bipolar electrograms <0.5mV during sinus rhythm. LVZ extent was calculated as the percentage of LA surface area, and subsequently, LVZ was categorized into stages I (<5%), II (≥5% to <20%), III (≥20% to <30%), and IV (≥30%). Patients with LVZs underwent LVZ ablation aimed at homogenization of ≥80% of LVZs following pulmonary vein isolation. The primary endpoint was atrial tachyarrhythmia recurrence-free survival after a single procedure at 18 months off antiarrhythmic drugs. The association of %LVZ with recurrence-free survival was examined using Cox proportional hazard models. RESULTS: The survival rates were 76%, 74%, 57%, and 28% in patients with stages I, II, III, and IV LVZ, respectively. The difference was significant between stages I and IV (log-rank, p<0.001), while not significant between stages I vs. II and I vs. III (p=0.843, p=0.073, respectively). Cox proportional hazard model revealed that %LVZ was an independent predictor of recurrence-free survival (hazard ratio, 1.025 per 1% increase, p<0.001; unadjusted model). The results were similar after demographic and clinical covariate adjustments and after excluding 12 patients who did not achieve homogenization of ≥80% of LVZ. CONCLUSIONS: The extent of LVZ is an independent predictor for recurrence even after LVZ homogenization.

A Novel Mapping System for Panoramic Mapping of the Left Atrium: Application to Detect and Characterize Localized Sources Maintaining Atrial Fibrillation.

Objectives: This study sought to use a novel panoramic mapping system (CARTOFINDER) to detect and characterize drivers in persistent atrial fibrillation (AF). Background: Mechanisms sustaining persistent AF remain uncertain. Methods: Patients undergoing catheter ablation for persistent AF were included. A 64-pole basket catheter was used to acquire unipolar signals, which were processed by the mapping system to generate wavefront propagation maps. The system was used to identify and characterize potential drivers in AF pre- and post-pulmonary vein (PV) isolation. The effect of ablation on drivers identified post-PV isolation was assessed. Results: Twenty patients were included in the study with 112 CARTOFINDER maps created. Potential drivers were mapped in 19 of 20 patients with AF (damage to the basket and noise on electrograms was present in 1 patient). Thirty potential drivers were identified all of which were transient but repetitive; 19 were rotational and 11 focal. Twenty-six drivers were ablated with a predefined response in 22 of 26 drivers: AF terminated with 12 and cycle length slowed (≥30 ms) with 10. Drivers with rotational activation were predominantly mapped to sites of low-voltage zones (81.8%). PV isolation had no remarkable impact on the cycle length at the driver sites (138.4 ± 14.3 ms pre-PV isolation vs. 137.2 ± 15.2 ms post-PV isolation) and drivers that had also been identified on pre-PV isolation maps were more commonly associated with AF termination. Conclusions: Drivers were identified in almost all patients in the form of intermittent but repetitive focal or rotational activation patterns. The mechanistic importance of these phenomena was confirmed by the response to ablation.

Efficacy of Left Atrial Voltage-Based Catheter Ablation of Persistent Atrial Fibrillation.

BACKGROUND: Low-voltage zones (LVZs) represent fibrotic tissue and are substrates for atrial fibrillation (AF). We hypothesized that LVZ-based substrate modification along with pulmonary vein isolation (PVI) would improve outcomes in persistent AF (PeAF) patients with LVZs, whereas PVI alone would work in patients without LVZs. METHODS AND RESULTS: Voltage mapping of the left atrium (LA) was performed during sinus rhythm in 101 PeAF patients in whom LVZ was defined as an area with bipolar electrograms <0.5 mV. Thirty-nine patients had LVZs and underwent ablation of the entire LVZ area after PVI (LVZabl group). In the remaining 62 patients without LVZs, PVI alone was performed with no further substrate modifications (PVI group). An additional group of 16 consecutive PeAF patients with LVZ did not undergo any substrate modification after PVI and were used as a comparison group (LVZnon-abl group) despite having similar size of LVZs to that in the LVZabl group. After a single session, 28 (72%) patients in the LVZabl group had no recurrence, whereas 49 (79%) patients in the PVI group had no recurrence during 18 ± 7 months of follow-up (log-rank, P = 0.400). In the LVZnon-abl group, only 6 patients (38%) had no recurrence during 32 ± 7 months of follow-up, even after a mean number of sessions of 1.8 (log-rank, P < 0.001, compared with the LVZabl group). CONCLUSIONS: Additional LVZ-based substrate modification after PVI improved the outcome in PeAF patients with LVZs, whereas PVI alone worked in patients without LVZs, even in those with PeAF.

Larger low voltage zone in endocardial unipolar map compared with that in epicardial bipolar map indicates difficulty in eliminating ventricular tachycardia by catheter ablation.

Patients with ischemic and non-ischemic cardiomyopathy often have substrate for ventricular tachycardia (VT) in the endocardium (ENDO), epicardium (EPI), and/or intramural. Although it has been reported that the ENDO unipolar (UNI) voltage map is useful in detecting EPI substrate, its feasibility to detect intramural scarring and its usefulness in radiofrequency catheter ablation (RFCA) remain unclear. To assess the relationship between the left ventricle (LV) ENDO UNI voltage map and the LV EPI bipolar (BIP) voltage map, and to determine the usefulness of the ENDO UNI voltage map to guide RFCA for VT in patients with cardiomyopathy undergoing combined ENDO- and EPI RFCA. Eleven patients with VT undergoing detailed ENDO and EPI electroanatomical mapping of the LV were included (mean age 59 ± 11 years, 9 men). We assessed the value of the LV ENDO UNI voltage map in identifying EPI and/or intramural substrate in these 11 patients with non-ischemic or ischemic cardiomyopathy. The underlying heart disease was dilated cardiomyopathy in 4 patients, cardiac sarcoidosis in 3, hypertrophic cardiomyopathy in 2, and ischemic heart disease in 2 patients. The mean LV ejection fraction was 24 ± 7 %. The low voltage zone (LVZ) was defined as <1.5 mV for LV ENDO BIP electrograms (EGMs), <8.3 mV for LV ENDO UNI EGMs, and <1.0 mV for LV EPI BIP EGMs. The surface area of each LVZ was measured. We also measured the LVZ of the spatial overlap between ENDO UNI and EPI BIP voltage maps using the transparency mode on CARTO software. We performed RFCA at the ENDO and EPI based on activation and/or substrate maps, targeting the LVZ and/or abnormal EGMs. The LVZ was present in the LV ENDO BIP voltage map in 10 of 11 patients (42 ± 33 cm(2)), and in the LV ENDO UNI voltage map in 10 of 11 patients (72 ± 45 cm(2)). The LVZ was present in the EPI BIP voltage map in 9 of 11 patients (70 ± 61 cm(2)), and the LVZ in the ENDO UNI voltage map was also seen in all 9 patients. The location of the LVZ in the EPI BIP map matched that in 45 ± 28 % of ENDO UNI voltage maps. The LVZ in the ENDO UNI voltage map was larger than that in the EPI BIP voltage map in 6 of 11 patients, and RFCA failed in 5 of these 6 patients. In the remaining 5 patients with a smaller LVZ in the ENDO UNI voltage map compared with the EPI BIP voltage map or no LVZ both at ENDO UNI and EPI BIP voltage map, VT was successfully eliminated in 4 of 5 patients. The LV ENDO UNI voltage map is useful in detecting EPI substrate in patients with cardiomyopathy. A larger LVZ in the ENDO UNI voltage map compared to that in the EPI BIP voltage map may indicate the presence of intramural substrate, which leads to difficulty in eliminating VT, even with combined ENDO- and EPI RFCA.

Right atrial tachycardias related to regions of low-voltage myocardium in patients without prior cardiac surgery: catheter ablation and follow-up results.

AIMS: There are only few descriptions of patients without prior cardiac surgery in whom a large low-voltage zone (LVZ) or scar is the electrophysiological substrate for various atrial tachycardias. We describe the electrophysiological and electroanatomic characteristics of unusual macroreentrant atrial tachycardias (MRATs) in seven patients with spontaneous right atrial (RA) scarring and present long-term follow-up results. METHODS AND RESULTS: In 7 of 326 patients with MRAT treated with radiofrequency ablation we detected regions of RA spontaneous LVZ or scarring during conventional mapping of the arrhythmia. They underwent electroanatomic mapping and catheter ablation of the spontaneous and further induced arrhythmias with a long-term follow-up. A total of 17 different atrial tachycardias were observed with typical atrial flutter in four patients. In five patients a LVZ was found in the RA free wall and two patients had a septal scar. Stable circuits were around the scar or LVZ in four patients and through a 'channel' within the scar in two. Radiofrequency ablation sites included the cavotricuspid isthmus for typical atrial flutter, between the inferior vena cava and scar, a channel in the scar or the left atrial (LA) mitral isthmus. During follow-up of 34 ± 5 months, four patients were free from atrial tachycardias. Both patients with a septal RA scar developed LA tachycardias, requiring further catheter ablation. One patient presented with a novel type of atypical scar-related RA flutter. CONCLUSION: Mapping and ablation of scar-related RA tachycardias is an effective treatment but does not preclude the development of further tachycardias, some of them arising from the LA during long-term follow-up.