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.

Influence of the left atrial contact areas on fixed low-voltage zones during atrial fibrillation and sinus rhythm in persistent atrial fibrillation.

BACKGROUND: Atrial low-voltage zones (LVZ) are suggested as important factors for maintaining persistent atrial fibrillation (PsAF). The relationship between LVZs and left atrial (LA) contact areas (CoAs) is still unclear. OBJECTIVE: To assess whether CoA regions were involved in atrial substrate properties maintaining PsAF. METHODS: A total of 50 patients with PsAF (36 long-lasting) were analyzed. Three representative CoA detection areas (ascending aorta-anterior-LA, descending aorta-left pulmonary vein antrum, and vertebrae-posterior-LA) were registered on the mapping geometry. Electrograms during AF and sinus rhythm (SR) were acquired, and the fractionated electrograms (CFE; < 80milliseconds) and voltages were analyzed regarding the CoAs. RESULTS: After SR conversion, 76% (38/50) had a significant LVZ (>5% of the total LA surface area). Patients with long-lasting PsAF versus PsAF had larger CoA areas (7.7 ± 3.0 vs. 4.5 ± 2.5cm2 , P < 0.05) and overlapped-LVZs (8.2 [3.2-11.0] vs. 2.1 [0.7-3.7] cm2 , P = 0.0126) between the SR-LVZs (<0.5 mV) and AF-LVZs (<0.2 mV). Overlapped-LVZs were frequently observed in CoA regions (anterior 76.4%; LIPV antrum 78.8%, and vertebrae 39.2%), and those LVZs had smaller unipolar voltages than those distant from the CoA regions (0.64 ± 0.16 vs. 2.5 ± 1.5 mV, P < 0.0001). SR-LVZ targeted ablation, including of CoA regions, rendered AF termination (n = 8, 21%), and 88% of the sites were not located immediately above, but adjacent to, the overlapped-LVZs. Significant AF slowing (6.0 ± 0.6 to 5.6 ± 0.6 Hz; P < 0.05) accompanied by unintentional CFE elimination (9.8-1.8 cm2 ; P < .0001) was achieved in patients without termination. CONCLUSION: Our data suggested that external structures in contact with the LA are involved in the creation of localized diseased myocardium necessary for PsAF maintenance.

Impact of catheter tip-tissue contact on three-dimensional left atrial geometries: Relationship between the external structures and anatomic distortion of 3D fast anatomical mapping and high contact force guided images.

BACKGROUND: A high catheter tip-tissue contact force (CF) with the myocardium may cause 3-dimensional (3D) map distortion, however, the influence of external structures surrounding the left atrium (LA) on that distortion remains unknown. This study characterized the impact of high CF mapping on the local LA geometry distortion. METHODS: Thirty AF patients underwent 3D-ultrasound merged with CT images (3D-Merge-CT). The LA area in contact with external structures was identified by enhanced CT. Fast-electroanatomical-mapping (FAM) geometries were created by two methods, point-by-point mapping with high (>10g) CFs (high-CF guided-FAM), followed by that with multielectrode-mapping catheters (conventional-FAM). The resulting geometries were compared with the 3D-Merge-CT images. RESULTS: Three representative anatomical contact areas (ascending aorta-vs.-anterior wall, descending aorta-vs.-left pulmonary vein [PV], and vertebrae-vs.-posterior wall) were identified. The PV antrum distorted distance on the 3D-Merge-CT was significantly longer for high-CF guided-FAMs than conventional-FAMs (1.7[0-3.6] vs. 0[0-1.8]mm, P<0.0001). In high-CF maps, the distorted distance significantly differed between regions with and without contact areas in both the PV antrum (0[0-0.17] vs. 1.7[0-3.9]mm, P=0.0201) and LA body region (0[0-1.5] vs. 1.7[0.7-2.2]mm, P<0.005). The catheter tip-tissue CF did not correlate with the distorted distance (r=0.08, P=0.46), and a multivariate analysis revealed that the absence of anatomical contact areas was strongly associated with significant local distortion, independent of the CF. CONCLUSIONS: High-CF guided mapping yields greater 3D-image anatomical distortion than conventional-FAM methods. That distortion was attenuated by regions with anatomical contact areas, suggesting that regional anatomic distortion is involved in the existence of external structures surrounding the LA.

Pathological autopsy of a patient that underwent a successful ablation of an electrical storm from the left ventricular summit.

A 65-year-old man with non-ischemic cardiomyopathy, underwent an autopsy 2 months after the successful ablation of a sustained left ventricular (LV) summit ventricular tachycardia (VT). The patient died due to interstitial pneumonia from amiodarone use. The earliest activation sites of the VT were documented from both inside the anterior interventricular vein (AIV) and epicardial surface. The diameter of the AIV was 3-4 mm, and the radiofrequency (RF) lesion inside the AIV was a slight lesion due to high impedance with a high temperature. The lesion from the epicardial surface was also superficial and insufficient due to neighboring coronary arteries and the existence of epicardial fat. A successful application was performed from the LV endocardium, and diffuse myocardial fibrosis was observed in the mid-myocardium including inside the RF lesions. The actual relationship between the myocardial fibrosis and LV summit VT remains unclear, but this case showed the difficulty of achieving a successful ablation from the epicardial side, when the focus exists in the mid-myocardium around the LV summit.

Spatial Relation Between Left Atrial Anatomical Contact Areas and Circular Activation in Persistent Atrial Fibrillation.

INTRODUCTION: Atrial low-voltage zones (LVZs) may be related to maintenance of atrial fibrillation (AF). The influence of left atrial (LA) contact areas (CoAs) on reentrant or rotor-like sources maintaining AF has not been investigated. METHODS AND RESULTS: Forty patients with persistent AF (PsAF) were analyzed. Three representative CoA regions in the LA (ascending aorta: anterior wall; descending aorta: left inferior pulmonary vein; and vertebrae: posterior wall) were visualized by enhanced CT. Using circular catheters, the LVZs (<0.5 mV) were assessed after restoration of SR, and local activation mapping and frequency domain analyses were performed after induction of AF. Circular activation during AF was visually defined as sites with ≥2 rotations by serial electrograms encompassing >80% of the mean AF cycle length. A pivot was defined as the core of the localized circular activation. Anterior (39/40 patients, 98%), left pulmonary vein antrum (27/40, 68%), and posterior (19/40, 48%) CoAs were identified, and 80% (68/85) of those sites were overlapped by or close (<3 mm) to LVZs. Thirty-six (90%) patients demonstrated circular activation (3.1±1.7 sites/patients) along with significantly higher organized dominant frequencies (6.3 ± 0.5 Hz, regularity-index: 0.26 [0.23-0.41]) within the LA, and the average electrogram amplitude of those pivots was 0.30 mV (0.18-0.52). Of those sites, 55% (66/120) were located at or close to CoA regions. Catheter ablation including of LVZs neighboring CoAs terminated AF in 9 (23%) patients. CONCLUSIONS: External anatomical structures contacting the LA may be related to unique conduction properties in diseased myocardium necessary for PsAF maintenance.

The influence of the external structures in atrial fibrillation patients: Relationship to focal low voltage areas in the left atrium.

INTRODUCTION: Left atrial (LA) low voltage areas (LVAs) are suggested as an important factor for maintaining atrial fibrillation (AF). The relationship between focal LVAs and anatomical contact is still unclear. METHODS: Thirty paroxysmal AF (PAF) and 30 persistent AF (PsAF) patients underwent high density voltage mapping during sinus rhythm before any radiofrequency applications were performed. The relationship between the LVA (<0.5mV) and contact area (CoA) demonstrated by enhanced CT and the distance to near external structures were investigated. RESULTS: The anterior region, posterior wall and left pulmonary vein (LPV) antrum were the three most frequent LVA sites that corresponded to CoA sites, and LVAs mostly overlapped with CoAs (PAF 47/61: 77%, PsAF 63/74: 85%). In the PAF group, patients with posterior-LVAs had a shorter distance to the vertebrae than those without (2.8 ± 1.1 vs. 4.4 ± 1.9 mm; P=0.0086). The distance to the vertebrae was the only predictive factor of the existence of a posterior-LVA and the cut-off value was ≤2.9 mm (P<0.0001). Similarly, an LPV-LVA also had the same results (2.0 ± 0.5 vs. 2.7 ± 0.8mm, P=0.0127) and the cut-off value was ≤2.6mm (P=0.0391). In contrast, the PsAF patients had no difference in the distance when compared to the existence of an LVA. CONCLUSIONS: Anatomical CoAs demonstrated a spatial relationship to the LVAs in AF patients. In PAF patients, the distance to near external structures in the posterior region was a predictive factor for the existence of an LVA and may have had some influence on maintaining AF, while in PsAF patients no relationship was suggested.

Influence of left atrium anatomical contact area in persistent atrial fibrillation-relationship between low-voltage area and fractionated electrogram.

BACKGROUND: Atrial low-voltage areas are suggested to be related to maintenance of atrial fibrillation (AF). The influence of the left atrium (LA) contact area (CoA) has not been investigated. METHODS AND RESULTS: Twenty-two persistent AF patients underwent high-density mapping during AF and sinus rhythm (SR). Three representative CoA regions in the LA (ascending aorta: anterior wall; descending aorta: left inferior pulmonary vein [LIPV]; and vertebrae: posterior wall) were identified. Electrogram analysis of both high dominant frequency (high-DF; >8 Hz) and complex fractionated atrial electrogram (con-CFAE; <50 ms) regions during SR was done. The anatomical relationship between CoA and both the very low-voltage areas (vLVA; <0.2 mV) and high-frequency sources was determined. Forty-seven vLVA (194.4 cm(2)) and 60 CoA (337.0 cm(2)) were documented, and 32 vLVA directly overlapped CoA. The vLVA were preferentially found in the anterior (45%) and posterior (13%) walls of the LA, and in the LIPV (13%), and corresponded to CoA sites. The mean voltage during SR at high-DF sites was significantly lower than that at con-CFAE sites (0.62 vs.1.54 mV; P<0.0001). Seventy-two percent of high-DF sites overlapped CoA, while 54% of con-CFAE did. Furthermore, 44% of high-DF surface area directly overlapped CoA, while only 19% of con-CFAE did. CONCLUSIONS: Very low-voltage regions had a strong association with CoA. Sites with CoA had a higher incidence of fractionated electrograms both during SR and AF.

Epicardial adipose tissue-based defragmentation approach to persistent atrial fibrillation: its impact on complex fractionated electrograms and ablation outcome.

BACKGROUND: Increased epicardial adipose tissue (EAT) volume is associated with atrial fibrillation (AF). However, the efficacy of EAT-based left atrial (LA) ablation for persistent AF (PsAF) is unclear. OBJECTIVE: The purpose of this study was to assess whether EAT-based LA ablation is effective for PsAF. METHODS: In 60 PsAF patients (group I), 3-dimensional reconstructed computed tomography images depicting EAT were merged with NavX-based dominant-frequency (DF) and complex fractionated electrogram (CFE) maps obtained during AF. Pulmonary vein antrum isolation (PVAI) was followed by map-guided EAT-based ablation. Results were compared to those in a historical control group (group II, case-matched patients who underwent generalized stepwise ablation including linear plus CFE-targeted ablation). RESULTS: In 70% (n = 42) of group I patients, the LA-EAT was located at the pulmonary vein antra; anterior and inferior surfaces, roof, septum, and mitral annulus; and left atrial appendage. EAT was at or near (<3 mm) 71% (390/550) of high-DF (> -8 Hz) sites. In 41 patients with persistent AF despite EAT-targeted ablation, CFE burden decreased significantly (from 96% to 13%, P < .0001), and DF decreased within the coronary sinus (6.9 ± 0.7 Hz vs 5.9 ± 0.7 Hz, P < .0001). Radiofrequency energy duration was significantly less in group I than in group II (25 ± 6 minutes vs 31 ± 12 minutes, P < .05). During 16-month follow-up, freedom from AF on antiarrhythmic drugs was 78% vs 60% (P < .05). CONCLUSION: PVAI plus EAT-based ablation efficiently eliminates high-frequency sources and yields relatively high success. EAT-based LA ablation is a simple, clinically feasible PsAF ablation strategy.