BACKGROUND Although low voltage zones (LVZs) in the left atrium (LA) are seen as arrhythmogenic substrate in some patients with atrial fibrillation (AF), pathophysiologic factors responsible for LVZ formation remain unclear. OBJECTIVE To elucidate the anatomical relation between the LA and ascending aorta responsible for remodeling of the anterior LA wall. METHODS We assessed the relation between existence of LVZs on the anterior LA wall and measurements taken on 3-dimensional computed tomography images obtained from 102 patients who underwent AF ablation. RESULTS Twenty-nine patients (28%) had LVZs >1.0 cm2 on the LA wall at the LA-ascending aorta contact area (LVZ Group); no LVZs were seen in the other 73 patients (No LVZ Group). In the LVZ Group (vs. No LVZ Group), the aorta-LA angle was smaller (21.0±7.7° vs. 24.9±7.1°, P = 0.015), the aorta-left ventricle (LV) angle was greater (131.3±8.8° vs. 126.0±7.9°; P = 0.005), non-coronary cusp (NCC) diameter was greater (20.4±2.2 mm vs. 19.3±2.5 mm; P = 0.036), and the NCC was closer to the anterior LA wall (2.29±0.68 mm vs. 2.76±0.79 mm; P = 0.006). The aorta-LA angle correlated positively with patients’ body mass index (BMI) and negatively with body weight and BMI. CONCLUSION Deviation of the ascending aorta course and distention of the NCC appear to be related to the development of LA anterior wall LVZs at the LA-ascending aorta contact area. Mechanical pressure exerted by extracardiac structures on the LA along with limited thoracic space may contribute to the development of LVZs associated with AF.

Introduction: Presence of preferential pathway conduction is mostly detected as fractionated presystolic potentials preceding the QRS onset during premature ventricular contractions (PVCs) and late potentials during sinus rhythm (SR), but the electrophysiologic mechanisms and significance of these potentials have not been fully clarified. We describe a PVC case series in which the preferential pathway conduction was 3-dimensionaly visualized by coherent mapping with the conduction velocity vector. Methods: Five PVCs (2 from the left coronary cusp, 2 from the commissure of the left and right coronary cusps, and 1 from the pulmonary artery) in 4 patients for which a fractionated presystolic potential during the PVCs and late potential during SR were recorded at the successful ablation site were reviewed, and 3-dimensional coherent activation maps with the conduction velocity vector during the PVCs and SR were reconstructed. Results: At the successful ablation site, an “M”-shaped discrete presystolic-potential and “W”-shaped discrete late-potential were recorded in all patients. The configuration of the flipped electrogram of the presystolic-potential nearly matched that of the electrogram exhibiting the late-potential. We created coherent activation maps annotating the onset of the presystolic potentials during the PVCs, and the offset of the late potentials during SR, which suggested bidirectional conduction of the preferential pathway connecting the PVC origin to the myocardium. Conclusion: In this case series, the M-shaped presystolic potential and W-shaped late potential were reversely matched. These reverse potentials, and the coherent activation vector maps during PVCs and SR suggested bidirectional conduction of the preferential pathway in opposite directions.

One Electrogram-Tracing Tells All: what is the mechanism of this supraventricular tachycardia?Moyuru Hirata, MD*, Yuji Wakamatsu, MD*, Koichi Nagashima, MD, PhD*, Sayaka Kurokawa, MD, PhD*, Naoto Otsuka, MD*, Seina Yagyu, MD*, Shu Hirata, MD*, Toshiko Nakai, MD, PhD*, Yasuo Okumura, MD, PhD*.*Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, JapanCorrespondenceKoichi Nagashima, MD, PhD; Division of Cardiology, Department of Medicine, Nihon University School of Medicine, 30-1 Ohyaguchi-kamicho, Itabashi-ku, Tokyo 173-8610, JapanTel: +81-3-3972-8111Fax: +81-3-3972-1098E-mail: cocakochan@gmail.comTotal word count: 1036 words, 2 FiguresFunding: (None)Disclosures: (None)The work described was supported by departmental resources only.Keywords: narrow QRS tachycardia, atrioventricular nodal reentrant tachycardia, accessary pathway.

In dual loop reentrant ATs, the differentiation of the active circuit from the passive circuit in a dual loop reentry is still challenging. In such complicated AT cases, entrainment pacing is useful for determining the dominant circuit. However, we differentiated the active circuit by an AT activation map with an adjustment of the lower threshold value in the early meets late module. We also detected the gap of the previous PVI line by the same map with a further adjustment of the lower threshold value. The adjustment of the lower threshold might be advantageous for differentiating an active circuit of a dual loop reentry as well as gaps along the PVI line.

Introduction Although left atrial posterior wall isolation (LAPWI) in addition to pulmonary vein isolation is a well-accepted option for persistent atrial fibrillation (AF), complete isolation can be challenging. To evaluate performance of a modified ablation index (AI) (AI/bipolar voltage along the ablation line) for predicting durable LAPWI. Methods The study involved 55 consecutive patients, aged 65 ± 11 years, who underwent electroanatomic mapping-guided LAPWI for AF. Association between gaps (first-pass LAPWI failure and/or acute LAPW reconnections), voltage amplitude along the roof and floor lines, and thickness of the LAPW was investigated. Results Gaps occurred in 22 patients (40%) and in 26 (8%) of the 330 line segments assessed—11 in the center roof line segment, 6 in the center floor line segment, 4 in the right roof line segment, 4 in the right floor line segment, and 1 in the left floor line segment. Gaps were associated with relatively high bipolar voltage (3.38 ± 1.83 vs. 1.70 ± 1.12 mV, P < 0.0001) and a thick LA wall (2.52 ± 1.15 vs. 1.42 ± 0.44 mm, P < 0.0001). A modified AI ≤ 199 AU/mV, bipolar voltage ≥ 2.64 mV, wall thickness ≥ 2.04 mm, and roof ablation line ≥ 43.4 mm well predicted gaps (AUCs: 0.783, 0.787, 0.858, and 0.752, respectively). Conclusions High voltage zones, a thick LAPW, and a long roof ablation line appear to be determinants of gaps, and a modified AI ≥ 199 AU/mV along the ablation lines appears to predict acute durable LAPWI.

Introduction: The clinical efficacy and safety of hot balloon ablation (HBA) for treatment of persistent AF (PerAF) remain unclear. We aimed to evaluate the clinical efficacy and safety of HBA vs. cryoballoon ablation (CBA) as treatment for PerAF. Methods: Of 195 consecutive patients who underwent initial catheter ablation for PerAF (AF lasting >7 days but <12 months), 158 propensity score-matched (79 HBA and 79 CBA) patients were included in our study. All patients who underwent HBA received applications of energy to the upper posterior LA wall with a larger balloon in addition to single shots to each pulmonary vein (PV) ostium, whereas those who underwent CBA received simple single-shot applications. The electrically isolated surface area (ISA), including the PV antrum and part of the posterior LA wall, was assessed by high-resolution mapping. Results: Success of the PV isolation with balloon shots alone did not differ between HBA and CBA (81% vs. 85%; P = 0.52). The ISA was generally wide in both groups and significantly larger in the HBA group than in the CBA group (61 ± 16% vs. 51 ± 12%, P < 0.001). The incidence of procedure-related complications did not differ significantly (HBA 4% vs. CBA 1%; P = 0.62) nor did the arrhythmia recurrence rate (HBA 11% vs. CBA 18% at 18 months; P = 0.26). Conclusion: Despite the difference in protocols, HBA and CBA performed for PerAF appear comparable in terms of wide antral lesion creation, clinical efficacy, and safety.