Kazuki Iso

Relation Between Left Atrial Wall Thickness in Patients with Atrial Fibrillation and Intracardiac Electrogram Characteristics and ATP-Provoked Dormant Pulmonary Vein Conduction

Atrial remodeling plays a key role in development of the substrate for atrial fibrillation (AF). Whether the wall thicknesses of the left atrium (LA) and pulmonary vein (PV)–LA junction affect remodeling and AF ablation is unknown. We investigated the relationship between wall thicknesses, electrogram characteristics, and adenosine triphosphate (ATP)‐provoked dormant PV conduction as they pertain to AF.

Relations between contact force, bipolar voltage amplitude, and mapping point distance from the left atrial surfaces of 3D ultrasound- and merged 3D CT-derived images: Implication for atrial fibrillation mapping and ablation.

BACKGROUND Catheter tip-derived contact force (CF) and 3-dimensional (3D) maps are key to mapping and ablation of atrial fibrillation. OBJECTIVE This study sought to determine the relation between CF and 3D map surfaces. METHODS We conducted a validation study of Carto-based 3D ultrasound (3D-US) and 3D-US merged with computed tomography (3D-Merge-CT) left atrium/pulmonary vein images. Under fluoroscopic guidance, 1361 mapping points (20 patients) with CFs and electrogram information were randomly acquired around the PVs. RESULTS CF correlated weakly with the distance of mapping points from the 3D-Merge-CT (r = 0.27; P < .001) and 3D-US (r = 0.22; P < .001) surfaces but not with bipolar voltage (r = -0.01; P = .2400). Low CF (0-4 g) yielded points close to the 3D-US surface; moderate (5-9 g) and high CFs (10-20 g) generated points beyond the surface (0.1 ± 3.9, 1.4 ± 3.4, and 2.3 ± 3.4 mm; P < .05 for each). Low, moderate, and high CFs yielded points below, close to, and beyond the 3D-Merge-CT surface (-1.2 ± 3.7, 0.4 ± 3.0, and 1.0 ± 2.9 mm; P < .05 for each). CONCLUSION Poor correlation between CF and the distance of mapping points from the 3D map surfaces and electrogram information shows the limitation of 3D mapping and electrogram information for predicting good contact. In addition, mapping seems to require far less CF than ablation requires.

Effect of cryoballoon inflation at the right superior pulmonary vein orifice on phrenic nerve location

BACKGROUND Cryoballoon catheter ablation was developed to simplify ablation for atrial fibrillation (AF). Initial enthusiasm for its widespread use has been dampened by phrenic nerve (PN) injury (PNI). OBJECTIVE The purpose of this study was to assess the effect of cryoballoon inflation at the right superior pulmonary vein (RSPV) orifice on PN location and to elucidate the potential mechanism of PNI. METHODS Twenty patients with paroxysmal atrial fibrillation underwent ablation performed with a second-generation 28-mm cryoballoon catheter. Before ablation, the pacing-determined PN course was delineated along the right atrium. PN location and its relation to the RSPV as well as RSPV surface distortions after balloon inflation were established with a NavX mapping system. RESULTS During RSPV ablation, the inflated balloon surface extended anteriorly 6.3 ± 1.8 mm outside the RSPV. This narrowed the distance between the PN capture points in the RSPV vs PN location from 11.4 ± 5.0 mm to 7.5 ± 5.0 mm (P = .0002) and increased the PN capture area from 1.9 ± 1.3 cm(2) to 3.2 ± 1.8 cm(2) (P = .0004). Furthermore, the PN capture points shifted toward the orifice within the RSPV and after balloon inflation were located significantly closer to the orifice in the 3 patients with transient PNI than in those without PNI. CONCLUSION Cryoballoon inflation at the RSPV orifice alters PV/left atrial surface geometry, reducing the distance between the energy delivery source and the PN and increasing PN area, possibly explaining the mechanism of PNI. PN pacing within the RSPV after balloon inflation may be useful for preventing PNI.

Pulmonary vein distention explaining cryoballoon lesion efficacy

A 37-year-old man underwent cryoballoon ablation (CBA) for atrial fibrillation. After inflating a 28-mm cryoballoon, we maneuvered a decapolar mapping catheter …

Mechanistic Insights Into Durable Pulmonary Vein Isolation Achieved by Second-Generation Cryoballoon Ablation

Background The mechanism explaining the efficacy of cryoballoon ablation (CBA) for atrial fibrillation has not been clarified. Methods and Results We compared lesion characteristics between patients in whom pulmonary vein isolation (PVI) was performed by CBA (n=56) and those by contact force (CF)-based RF ablation (n=56). We evaluated the 3-dimensional PV morphology before and after cryoballoon inflation. After PVI, a 3D left atrial voltage map was created. Pacing (10 mA and 2 ms) was performed within the low voltage area from the ablation line, and electrically unexcitable ablated tissue was identified. ATP-provoked dormant conduction after PVI occurred in 9 of the 224 (4%) PVs in the CBA group and in 13 of the 224 (6%) PVs in the CF group (P=0.3935). The inflated balloon stretched the PV from the original PV ostial surface by 7.1±3.5 mm, but at sites with (vs, sites without) residual PV potential/dormant conduction, the extent of the PV distension was reduced (4.0±4.0 mm vs. 7.2±3.4 mm, P<0.0001). The unexcitable ablated tissue around the PVs was significantly wider in CB patients than in CF patients (16.7±5.1 mm vs. 5.3±2.3 mm, P<0.0001). Conclusions Use of the cryoballoon significantly distends the PV. Without this extensive distention, PVI may not be successful. CBA seems to yield wide unexcitable ablation zones. These factors seem to explain the durability of CBA lesions.

MRI Mode Programming for Safe Magnetic Resonance Imaging in Patients With a Magnetic Resonance Conditional Cardiac Device

Although diagnostically indispensable, magnetic resonance imaging (MRI) has been, until recently, contraindicated in patients with an implantable cardiac device. MR conditional cardiac devices are now widely used, but the mode programming needed for safe MRI has yet to be established. We reviewed the details of 41 MRI examinations of patients with a MR conditional device. There were no associated adverse events. However, in 3 cases, paced beats competed with the patients own beats during the MRI examination. We describe 2 of the 3 specific cases because they illustrate these potentially risky situations: a case in which the intrinsic heart rate increased and another in which atrial fibrillation occurred. Safe MRI in patients with an MR conditional device necessitates detailed MRI mode programming. The MRI pacing mode should be carefully and individually selected.

Frequency analysis of atrial fibrillation from the specific ECG leads V7-V9: A lower DF in lead V9 is a marker of potential atrial remodeling

INTRODUCTION High dominant frequency (DF) sites during atrial fibrillation (AF) play an important role in the perpetuation of AF. We investigated the relationship between the DFs from intracardiac electrograms (iEGM) and the surface electrocardiogram (ECG) during AF, and the relationship between the surface ECG DF and atrial remodeling. METHODS In 48 patients (57±11 years, 47 males, 20 paroxysmal), the V1-6 precordial leads and specific V7-9 ECG leads were recorded for 8s for an off-line analysis before AF ablation. The QRS-T complex was canceled by a template subtraction algorithm using the CEPAS™ system (Cuoretech Pty Ltd, Sydney, Australia). The iEGM DF maps, reconstructed using the Ensite NavX (St. Jude Medical, Inc., St. Paul, MN, USA) system, were simultaneously created for the right atrium and left atrium (LA) during AF. RESULTS The DF in leads V8 and V9 correlated well with the DF in the LA floor (R=0.55, p<0.01; R=0.68, p<0.01, respectively), and that in V1 with the right inferior pulmonary vein (R=0.45, p=0.01). Persistent AF patients had a significantly lower DF in lead V9 (5.7±1.0Hz vs. 6.7±1.5Hz, p=0.02) than paroxysmal AF patients. CONCLUSIONS A frequency analysis from lead V9 reflects the LA electrical activity.

Impact of Sinus Node Recovery Time after Long-Standing Atrial Fibrillation Termination on the Long-Term Outcome of Catheter Ablation

Atrial electrical and structural remodeling is related to the perpetuation of atrial fibrillation (AF) subsequent to sinus node dysfunction. We investigated the relationship between AF recurrence after catheter ablation and sinus node dysfunction in long-standing persistent AF patients using the sinus node recovery time (SNRT) after defibrillation.Fifty-one consecutive patients who underwent a first ablation for long-standing persistent AF were enrolled. Intracardiac cardioversion was applied before ablation in the absence of any antiarrhythmic drugs, and the power required to defibrillate, number, and SNRT after defibrillation were measured. All patients underwent the same designed radiofrequency catheter ablation procedure.No patient required permanent pacemaker implantation due to sinus dysfunction after the ablation. During the follow-up period of 28.4 months (3.6-43.7), 35 out of 51 patients (69%) experienced an AF recurrence. The AF recurrence was significantly associated with an older age (60 ± 11 versus 52 ± 12 years in the non-recurrence group, P = 0.0196), longer SNRT after defibrillation (1722 [1410-2656] versus 1295 [676-1651] msec, P = 0.0125), and larger left atrial (LA) volume (59 ± 25 versus 41 ± 15 mL, P = 0.0119). There were no significant differences in the AF duration, AF cycle length, and right and total atrial conduction times between the 2 groups. A longer SNRT after defibrillation (adjusted HR 2.13, 95%CI 1.16-3.71, P = 0.0152) and larger LA volume (adjusted HR 1.03, 95%CI 1.01-1.04, P = 0.0054) were independent predictors of AF recurrence after ablation.Assessment of the SNRT after defibrillation may help to predict a successful ablation in patients with long-standing persistent AF.

Left atrial remodeling: Regional differences between paroxysmal and persistent atrial fibrillation

The mechanisms underlying self‐perpetuation of persistent atrial fibrillation (AF) are not well understood. To gain insight into these mechanisms, we conducted a study comparing left atrial (LA) electroanatomic maps obtained during sinus rhythm between patients with paroxysmal AF (PAF) and patients with persistent AF (PerAF).

Complex fractionated atrial electrograms, high dominant frequency regions, and left atrial voltages during sinus rhythm and atrial fibrillation

Ablation targeting complex fractionated atrial electrograms (CFAEs) or high dominant frequency (DF) sites is generally effective for persistent atrial fibrillation (AF). CFAEs and/or high DF sites may exist in low‐voltage regions, which theoretically represent abnormal substrates. However, whether CFAEs or high DF sites reflect low voltage substrates during sinus rhythm (SR) is unknown.