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Background: The impact of using direct-to-consumer wearable devices as a means to timely detect atrial fibrillation (AF) and to improve clinical outcomes is unknown., Methods: Heartline is a pragmatic, randomized, and decentralized application-based trial of US participants aged ≥65 years. Two randomized cohorts include adults with possession of an iPhone and without a history of AF and those with a diagnosis of AF taking a direct oral anticoagulant (DOAC) for ≥30 days. Participants within each cohort are randomized (3:1) to either a core digital engagement program (CDEP) via iPhone application (Heartline application) and an Apple Watch (Apple Watch Group) or CDEP alone (iPhone-only Group). The Apple Watch Group has the watch irregular rhythm notification (IRN) feature enabled and access to the ECG application on the Apple Watch. If an IRN notification is issued for suspected AF then the study application instructs participants in the Apple Watch Group to seek medical care. All participants were "watch-naïve" at time of enrollment and have an option to either buy or loan an Apple Watch as part of this study. The primary end point is time from randomization to clinical diagnosis of AF, with confirmation by health care claims. Key secondary endpoint are claims-based incidence of a 6-component composite cardiovascular/systemic embolism/mortality event, DOAC medication use and adherence, costs/health resource utilization, and frequency of hospitalizations for bleeding. All study assessments, including patient-reported outcomes, are conducted through the study application. The target study enrollment is approximately 28,000 participants in total; at time of manuscript submission, a total of 26,485 participants have been enrolled into the study., Conclusion: The Heartline Study will assess if an Apple Watch with the IRN and ECG application, along with application-facilitated digital health engagement modules, improves time to AF diagnosis and cardiovascular outcomes in a real-world environment., Trial Registration: ClinicalTrials.gov Identifier: NCT04276441., Competing Interests: Conflict of Interest CMG: Research grant support from Johnson & Johnson and Apple. SS: Research grant from Janssen Pharmaceuticals; Employment with PhysIQ, Inc. DL: Research grant from AtriCure and Biosense Webster. Speakers engagement and advisory boards with Medtronic, Abbott, Boston Scientific, Biosense Webster. MPT: Related to the submitted work: Consulting fees from Johnson & Johnson. Outside of the submitted work: consulting fees from Medtronic Inc, Abbott, Pfizer, Sanofi, InCarda, 100Plus, AliveCor, Acutus, Sanofi, Bristol Myers Squibb, Medtronic; grants from Bristol Myers Squibb, American Heart Association, Sanofi, Apple, Bayer, Gilead, US Food and Drug Administration, employment from iRhythm Technologies. RP: Advisory boards for Johnson & Johnson, Abbott, Medtronic; research support Abbott and American Heart Association. WSJ: Research grants from Bayer, Boehringer Ingelheim, Janssen, Merck, Novartis, National Institute on Aging, Patient-Centered Outcomes Research Institute. TJB: Research grant support from Boehringer Ingelheim, Altathera, Boston Scientific. ABC: Advisory board for Janssen Pharmaceuticals, Medtronic Inc., Abbott, Sanofi Aventis, Milestone Pharmaceuticals, Eagle Pharmaceuticals; honoraria for speaking from Medtronic Inc., Abbott, Sanofi Aventis, Milestone Pharmaceuticals. EP: Research support from Janssen, Bristol-Myers Squibb, Amgen, Esperion; Advisory boards for Novartis, Novo Nordisk, Cerner. JR: Advisory boards for Acesion Pharma and InCarda; consultant for Advanced Medical Education, Element Science, GV, Inc.; steering committee for Janssen; stock options for AblaCor, Element Science, InfoBionic, LuxCath, NewPace, Celero Systems. LS: consultant for Abbott and executive committee member for Johnson & Johnson Heartline trial. MT: Employee of Tiltas Solutions; no other competing interests to disclose. KGT: Full-time employee of Medtronic. NM: Consultant for AtriCure Biosense Webster, Sanofi, Pfizer; honoraria for speaking: Biotronik, Bristol Myers Squibb, Sanofi; research grants from Biosense Webster, St. Jude Medical, Johnson & Johnson, Medtronic, Boston Scientific. MP: Employee of and may hold stock in Apple. AH, SK, JN, SJ, KW, and CVD: employees of Janssen and may hold stock in Johnson & Johnson. JAS: Principal investigator of grants from NIH, Abbott Vascular, and the American College of Cardiology Foundation; consultant to Janssen, Novartis, Amgen, Bristol Myers Squibb, AstraZeneca, Bayer, Terumo, Merck; Scientific Advisory Board of UnitedHealthcare and Board of Directors for Blue Cross and Blue Shield of Kansas City; Copyright owner of the KCCQ, SAQ, and PAQ., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Data regarding the use of high-power short-duration (HPSD) radiofrequency (RF) in combination with half-normal saline irrigation for catheter irrigation are limited., Objectives: This study investigated the safety and efficacy of using HPSD RF ablation in combination with half-normal saline irrigation for the treatment of AF., Methods: One hundred consecutive patients with AF underwent RF ablation using HPSD combined with half-normal saline for catheter irrigation. In addition, the following ablation strategies were used: 1 mm tags for the display of ablation lesions on the mapping system, high-frequency jet ventilation (HFJV), low contact force, pacing after ablation to verify areas of noncapture, atrial/ventricular pacing at 500 to 700 ms to aid in catheter stability, use of two skin electrodes to reduce impedance, and postablation adenosine infusion. Power was started at 40 to 45 W and was modulated manually based on impedance changes., Results: The average age of patients was 65.2 years and 70% were male. Forty seven percent had paroxysmal AF and the average CHA 2 DS 2 -VASc score was 2.1 ± 1.6. The average power and lesion duration were 38.1 ± 3.3 W and 8.1 ± 2.3 s, respectively. During a median follow-up period of 321 ± 139 days, 89% of the patients remained free from any atrial arrhythmias after a single RF ablation procedure. No procedure-related death, stroke, pericardial effusion, or atrioesophageal fistula occurred during follow-up., Conclusions: Catheter ablation using HPSD RF lesions in combination with half-normal saline irrigation and is safe and effective, and results in high rate of freedom from AF., (© 2021 Wiley Periodicals LLC.)

Purpose: Use of oral anticoagulation (OAC) in patients with a history of intracranial hemorrhage (ICH) is often considered high risk as OAC-related ICH is associated with high mortality rates. Left atrial appendage closure with a WATCHMAN device is an alternative management strategy to OAC to decrease thrombotic risk in atrial fibrillation patients; however use of OAC followed by dual antiplatelet therapy (DAPT) or DAPT therapy alone is required for 6 months post-procedurally. In this study, we examined the safety of WATCHMAN implantation followed by 6 months of anti-thrombotic therapy in patients with a history of ICH., Methods: This is a retrospective analysis of 63 patients with a history of ICH prior to WATCHMAN implantation (Group I) and 95 patients without a history of ICH who underwent WATCHMAN placement (Group II). The primary outcome was death, stroke, or major bleeding within 6 months of WATCHMAN placement., Results: The average CHA 2 DS 2 -VASc of Group I was 4.9 ± 1.7 vs 4.7 ± 1.4 for Group II (p = 0.34). The most common type of ICH in Group I was an intracerebral hemorrhage (57%). The median time between ICH and WATCHMAN implantation in Group I patients was 212 days. A total of 19% of Group I patients were managed with DAPT alone post-procedurally vs. 3% in Group II (p < 0.001). Similar to 89% of Group II (p = 0.19), 95% of Group I patients were free of the primary outcome at 6 months. No Group I patients had recurrent ICH within 6 months after WATCHMAN implantation., Conclusion: In a retrospective, multicenter series of patients with a history of ICH prior to WATCHMAN implantation, WATCHMAN placement was performed safely with 6-month outcomes that were similar to patients without a history of ICH, encompassing the time during which a patient with a history of ICH would need antithrombotic therapy to facilitate WATCHMAN placement.

Background: Left atrial appendage closure (LAAC) is an alternative to long-term anticoagulation for thromboembolic protection in patients with atrial fibrillation (AF) and high bleeding risk. Short-term Warfarin use following LAAC is well-studied, while data pertaining to novel oral anticoagulant (NOAC) use in this setting is less robust. Specifically, data regarding the safety and efficacy of postprocedural NOAC use in high-risk patients is lacking., Objective: To compare the safety and efficacy of Warfarin and NOAC use in a high-risk patient population undergoing LAAC with the WATCHMAN device., Methods: From November 2015 to October 2017, 97 patients underwent LAAC with the WATCHMAN device. All patients were discussed at a multidisciplinary meeting prior to device implantation. Longitudinal data were collected and analyzed for a composite endpoint of stroke and death at 8 months, and major bleeding at 3 and 6 months., Results: Among the 90 patients included in the safety and efficacy analysis, 43 were prescribed Warfarin and 47 were prescribed NOACs. Baseline characteristics were comparable between study groups. There were no procedural complications and no significant differences in the incidence of death and stroke at 8 months or major bleeding at 3 and 6 months., Conclusion: For patients with AF at high risk of both thromboembolic and hemorrhagic events, NOACs as compared to Warfarin, seem to be safe and effective for short-term anticoagulation following LAAC with the WATCHMAN device. Further validation in large randomized controlled trials is required., (© 2019 Wiley Periodicals, Inc.)

Background: Currently, little is known about the onset, natural progression, and management of esophageal injuries after atrial fibrillation (AF) ablation., Objectives: We sought to provide a systematic review on esophageal injury after AF ablation and identify temporal relationships between various types of esophageal lesions, their progression, and clinical outcomes., Methods: A comprehensive search of PubMed and Web of Science was conducted until September 21, 2017. All AF ablation patients who underwent upper gastrointestinal endoscopy within 1 week of the procedure were included. Patients with esophageal lesions were classified into 3 types by using our novel Kansas City classification: type 1: erythema; type 2a: superficial ulcers; type 2b: deep ulcers; type 3a: perforation without communication with the atria; and type 3b: perforation with atrioesophageal fistula., Results: Thirty studies met our inclusion criteria. Of the 4473 patients, 3921 underwent upper gastrointestinal evaluation. The overall incidence of esophageal injuries was 15% (570). There were 206 type 1 lesions (36%), 222 type 2a lesions (39%), and 142 type 2b lesions (25%). Six of 142 type 2b lesions (4.2%) progressed further to type 3, of which, 5 were type 3a and 1 was type 3b. All type 1 and type 2a and most type 2b lesions resolved with conservative management. One type 3a and 1 type 3b lesions were fatal., Conclusion: Based on our classification, all type 1 and most type 2 lesions resolved with conservative management. A small percentage (4.2% [6 of 142]) of type 2b lesions progressed to perforation and/or fistula formation, and these patients need to be followed closely., (Copyright © 2018. Published by Elsevier Inc.)

Background: During atrial fibrillation (AF), a high rate of myocyte activation causes cellular stress and initiates the process of atrial remodeling, which further promotes persistence of AF. Although heat shock proteins (HSPs) have been shown to prevent atrial remodeling and suppress the occurrence of AF in cellular and animal experimental models, increased levels of HSP-60 have been observed in patients with postoperative AF, likely reflecting a response to cellular stress. To better understand the role of HSP-60 in relation to AF, we examined the association of HSP-60 levels in relation to the future development of AF in the Multi-Ethnic Study of Atherosclerosis (MESA)., Methods: MESA is a cohort study that recruited 6,814 participants aged 45-84 years and free of known cardiovascular disease at baseline (2000-2002) from six field centers. We investigated 983 participants, selected at random from the total cohort, who had HSP-60 measured and were free of AF at baseline. We tested the association of HSP-60 levels with the incidence of AF using multivariate Cox models after adjustment for demographics, clinical characteristics, and biomarkers., Results: During an average of 10.6 years of follow-up, 77 participants developed AF. We did not observe a significant association between the log-transformed HSP-60 levels and development of AF on either unadjusted or multivariate analysis (adjusted hazard ratio: 1.02 per unit difference on natural log scale, 95% confidence interval: 0.77-1.34 ln (ng/mL)., Conclusion: Contrary to the findings from the preclinical studies, which demonstrated an important role of HSP-60 in the pathogenesis of AF, we did not observe a significant association between HSP-60 and occurrence of AF., (© 2016 Wiley Periodicals, Inc.)

Inflammation is associated with the development of atrial fibrillation (AF). Activity in hematopoietic tissues, which produce inflammatory leukocytes, is closely related to systemic inflammation, arterial inflammation and cardiovascular events, but its relationship to AF is unknown. Using 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging, we examined the relationships between AF, splenic metabolic activity and vascular inflammation. We conducted a cross sectional study of 70 participants: 35 with AF, who were matched (by age, sex and history of active cancer) to 35 controls without AF. Splenic metabolic activity and vascular aortic inflammation were measured by the mean FDG maximum standard uptake values (SUV Max) by PET. We examined (1) the association between AF and splenic activity, and (2) AF and aortic inflammation. The mean age of the population was 68.13 (standard deviation (SD) 8.98) years and 46 (65 %) participants were male. Splenic activity was higher in AF participants [2.31 (SD 0.45) vs. 2.07 (SD 0.37), p = 0.024], and remained significant after adjusting for demographic and clinical covariates. Aortic inflammation was also higher in AF participants [2.22 (SD 0.44) vs. 1.91 (SD 0.44), p = 0.004], and remained significant on multivariable analysis. Aortic inflammation and splenic activity were highly correlated (Pearson R = 0.61, p < 0.001). Atrial fibrillation is associated with higher hematopoietic tissue activation and arterial inflammation. Further studies are needed to clarify the mechanisms by which this cardio-splenic axis is implicated in AF.

Introduction: Phrenic nerve (PN) injury is one of the major complications of pulmonary vein isolation (PVI). Pace mapping for PN capture is routinely used to identify areas with high risk for injury along the anterior border of the right pulmonary veins (PVs). Our aim was to evaluate the feasibility of using preprocedural imaging to identify areas where no PN capture is possible along the anterior border of the right PVs, thus avoiding the need for pace mapping during PVI., Methods and Results: It was hypothesized that PN capture along the anterior border of the right PVs does not occur in the area where the right and left atria overlap. Three-dimensional segmentation of both atria was performed on preprocedural magnetic resonance and computed tomography angiograms in 40 patients before undergoing PVI. The area of overlap between the right and left atria was delineated. Image registration was performed during the procedure. Using pacing, regions with and without PN capture were marked along the anterior border of the right PVs. A total of 361 points were tested for PN stimulation (9 ± 4 points/patient). PN capture occurred in 97 out of the 189 points (51%) in the area with no overlap between the right and left atria. No PN capture occurred in the area of overlap (172 points, P< 0.001)., Conclusion: Delineation of the area of overlap between the right and left atria derived from preprocedural imaging reliably identifies regions where PN pace capture does not occur. Testing for PN stimulation before ablation may not be necessary in these regions., (© 2015 Wiley Periodicals, Inc.)

Background: Radiation exposure in the electrophysiology lab is a major occupational hazard to the electrophysiologists. A catheter localization system (MediGuide Technology, St. Jude Medical Inc., St. Paul, MN, USA) allows the integration of electroanatomical mapping and x-ray imaging, and has been shown to be effective in reducing radiation exposure during several electrophysiological procedures. We intended to evaluate the feasibility of this catheter tracking system to guide transseptal (TS) access., Methods: The feasibility of performing TS puncture with MediGuide (MDG) was assessed in a prospective observational study in 16 patients undergoing radiofrequency ablation for atrial fibrillation. These patients were compared to 16 matched patients undergoing similar procedures during the same time frame using conventional approach. There were no differences in mean age, gender distribution, and body mass index between the two groups. Total duration of fluoroscopic exposure during TS puncture was compared between the two groups., Results: All patients underwent successful TS puncture. Fluoroscopy time for double TS puncture using the MDG system was significantly lower than the control group (0.48 ± 0.17 minutes vs. 5.9 ± 0.65 minutes; P < 0.0001). No major complications occurred during the procedures in either group., Conclusions: TS puncture can be successfully performed using MDG, and results in significant reduction in radiation exposure., (©2015 Wiley Periodicals, Inc.)

Atrial fibrillation (AF) is generally considered a progressive disease, typically evolving from paroxysmal through persistent to 'permanent' forms, a process attributed to electrical and structural remodelling related to both the underlying disease and AF itself. Medical treatment has yet to demonstrate clinical efficacy in preventing progression. Large clinical trials performed to date have failed to show benefit of rhythm control compared with rate control, but these trials primarily included patients at late stages in the disease process. One possible explanation is that intervention at only an early stage of progression may improve prognosis. Evolving observations about the progressive nature of AF, along with the occurrences of major complications such as strokes upon AF presentation, led to the notion that earlier and more active approaches to AF detection, rhythm-reversion, and maintenance of sinus rhythm may be a useful strategy in AF management. Approaches to early and sustained rhythm control include measures that prevent development of the AF substrate, earlier catheter ablation, and novel antiarrhythmic drugs. Improved classifications of AF mechanism, pathogenesis, and remodelling may be helpful to enable patient-specific pathophysiological diagnosis and therapy. Potential novel therapeutic options under development include microRNA-modulation, heatshock protein inducers, agents that influence Ca(2+) handling, vagal stimulators, and more aggressive mechanism-based ablation strategies. In this review, of research into the basis and management of AF in acute and early settings, it is proposed that progression from paroxysmal to persistent AF can be interrupted, with potentially favourable prognostic impact., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.)

Objectives: The purpose of this study was to evaluate the feasibility and safety of uninterrupted rivaroxaban therapy during atrial fibrillation (AF) ablation., Background: Optimal periprocedural anticoagulation strategy is essential for minimizing bleeding and thromboembolic complications during and after AF ablation. The safety and efficacy of uninterrupted rivaroxaban therapy as a periprocedural anticoagulant for AF ablation are unknown., Methods: We performed a multicenter, observational, prospective study of a registry of patients undergoing AF ablation in 8 centers in North America. Patients taking uninterrupted periprocedural rivaroxaban were matched by age, sex, and type of AF with an equal number of patients taking uninterrupted warfarin therapy who were undergoing AF ablation during the same period., Results: A total of 642 patients were included in the study, with 321 in each group. Mean age was 63 ± 10 years, with 442 (69%) males and 328 (51%) patients with paroxysmal AF equally distributed between the 2 groups. Patients in the warfarin group had a slightly higher mean HAS- BLED (hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly, drugs/alcohol concomitantly) score (1.70 ± 1.0 vs. 1.47 ± 0.9, respectively; p = 0.032). Bleeding and embolic complications occurred in 47 (7.3%) and 2 (0.3%) patients (both had transient ischemic attacks) respectively. There were no differences in the number of major bleeding complications (5 [1.6%] vs. 7 [1.9%], respectively; p = 0.772), minor bleeding complications (16 [5.0%] vs. 19 [5.9%], respectively; p = 0.602), or embolic complications (1 [0.3%] vs. 1 [0.3%], respectively; p = 1.0) between the rivaroxaban and warfarin groups in the first 30 days., Conclusions: Uninterrupted rivaroxaban therapy appears to be as safe and efficacious in preventing bleeding and thromboembolic events in patients undergoing AF ablation as uninterrupted warfarin therapy., (Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Current 3D mapping systems have difficulty rendering complex cardiac structures. Different electroanatomical mapping software has been recently developed which uses a mathematical algorithm to improve interpolation between mapped points and delineation of closely spaced structures. This study tested the feasibility and accuracy of this software in comparison to traditional software., Methods: In vivo 3D impedance-based mapping using a multielectrode catheter with a single geometry point cloud was performed in the left atria and pulmonary veins (PV) in 23 patients undergoing catheter ablation for atrial fibrillation. The maps were analyzed with traditional (NavX, St. Jude Medical, Minnetonka, MN, USA), either with or without multichamber mapping versus St. Jude OneModel™ software and dimensions of cardiac chambers in human studies were compared to preprocedural computed tomographic (CT) or magnetic resonance (MR) scans to determine the relative accuracy of the maps., Results: Maps created by the OneModel software provided greater detail of complex cardiac structures compared to traditional software. Comparison of the left atrial/pulmonary vein electroanatomical maps with the CT and MR scans as reference standard demonstrated significantly less error in measurement of all PV ostial long- and short-axis dimensions, inter-PV distance, and ridge width (left PV to left atrial appendage) with the OneModel versus traditional software (P < 0.001 for all dimensions measured)., Conclusions: The OneModel software produces maps that are more accurate in rendering complex cardiac structures compared to traditional software., (©2013, The Authors. Journal compilation ©2013 Wiley Periodicals, Inc.)

Atrial fibrillation (AF) represents a growing public health burden. It is a complex condition, involving a number of etiologic factors and arrhythmia mechanisms associated with atrial remodeling. Greater understanding of these mechanisms may improve therapy. Current AF classification schemes are limited by simplicity. A number of risk factors predict AF onset, and additional factors are being evaluated in registry studies. Doppler imaging and Holter monitoring in high-risk patients to predict the onset of AF and progression from paroxysmal to permanent AF are promising. There is a need for a novel multifactorial classification model encompassing AF duration, symptoms, markers of atrial remodeling, and a risk score for AF onset, persistence, progression, and complications to guide treatment and prognostication. Preventing AF onset with upstream therapy is of great interest, but current data are conflicting. More study is needed to optimize rhythm control with antiarrhythmic drugs and targeted ablation to specific patient populations at an earlier stage. There is little consensus on optimal rate control and no information relating to optimum rate control in specific populations. This article highlights new concepts in AF and directions for future research., (Copyright © 2012 Mosby, Inc. All rights reserved.)

Aims: Previous studies have suggested that upstream medical therapy to modulate the renin-angiotensin axis may facilitate left atrial remodelling and thereby prevent new-onset atrial fibrillation (AF). The purpose of this study was to evaluate the association between angiotensin converting enzyme inhibitor (ACEI) and angiotensin receptor blockers (ARB) on new-onset AF in a large cohort of patients with coronary artery disease (CAD)., Methods and Results: This was a population-based study of 28 620 patients, from community-dwelling Medicare beneficiaries who had been hospitalized for acute myocardial infarction or coronary revascularization (1995-2004). All patients, 65 years and older, had a mean follow-up period of upto 3.8 ± 3.0 years. Patients with a history of AF before and during hospitalization were excluded. We compared the incidence of new-onset AF between patients who were (N= 10 918) and were not (N= 17 702) prescribed ACEI and/or ARB within 1 month of hospital discharge following cardiac event. New-onset AF within 5 and 10 years was 39.1 and 61.1%, respectively, in patients who received ACEI/ARB, compared 34.9 and 53.6% in patients who did not receive them [unadjusted hazard ratio (HR): 1.16; 95% confidence interval (CI): 1.11, 1.21]. Multivariable analysis adjusting for patient- and hospital-related characteristics indicated that ACEI/ARB use independently had no impact on the risk of developing new-onset AF compared with non-users (adjusted HR: 0.99; 95% CI: 0.94, 1.04). Adjustment for propensity-score and health-seeking behaviours yielded nearly identical results., Conclusion: Angiotensin converting enzyme inhibitor/ARB therapy initiated within 1 month after hospital discharge is not associated with a reduction in the risk of new-onset AF after myocardial infarction or coronary revascularization.

Objectives: The purpose of this study was to evaluate the feasibility and safety of periprocedural dabigatran during atrial fibrillation (AF) ablation., Background: AF ablation requires optimal periprocedural anticoagulation for minimizing bleeding and thromboembolic complications. The safety and efficacy of dabigatran as a periprocedural anticoagulant for AF ablation are unknown., Methods: We performed a multicenter, observational study from a prospective registry including all consecutive patients undergoing AF ablation in 8 high-volume centers in the United States. All patients receiving dabigatran therapy who underwent AF ablation on periprocedural dabigatran, with the dose held on the morning of the procedure, were matched by age, sex, and type of AF with an equal number of patients undergoing AF ablation with uninterrupted warfarin therapy over the same period., Results: A total of 290 patients, including 145 taking periprocedural dabigatran and an equal number of matched patients taking uninterrupted periprocedural warfarin, were included in the study. The mean age was 60 years with 79% being male and 57% having paroxysmal AF. Both groups had a similar CHADS(2) score, left atrial size, and left ventricular ejection fraction. Three thromboembolic complications (2.1%) occurred in the dabigatran group compared with none in the warfarin group (p = 0.25). The dabigatran group had a significantly higher major bleeding rate (6% vs. 1%; p = 0.019), total bleeding rate (14% vs. 6%; p = 0.031), and composite of bleeding and thromboembolic complications (16% vs. 6%; p = 0.009) compared with the warfarin group. Dabigatran use was confirmed as an independent predictor of bleeding or thromboembolic complications (odds ratio: 2.76, 95% confidence interval: 1.22 to 6.25; p = 0.01) on multivariate regression analysis., Conclusions: In patients undergoing AF ablation, periprocedural dabigatran use significantly increases the risk of bleeding or thromboembolic complications compared with uninterrupted warfarin therapy., (Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Introduction: Successful catheter ablation of atrial fibrillation (AF) requires the creation of transmural lesions in the left atrium (LA). In addition, cardiac perforation is more likely to occur in areas of thin walls. The LA wall thickness is thus relevant both for procedural efficacy and safety. This study sought to evaluate the regional LA wall thickness in patients with AF., Methods: The LA muscular wall thickness (excluding fat) was measured by 64 slice cardiac computed tomography (CT) in 60 patients with persistent AF prior to catheter ablation procedures. Measurements were performed in all patients at 12 distinct LA locations, including 3 at the roof (right, middle left), 3 at the floor (right, middle, left), 4 at the posterior wall (right, middle, middle-superior, left), 1 at the left lateral ridge (LLR), and 1 at the mitral isthmus., Results: There was a large range of LA wall thickness (average thickness 1.89 ± 0.48 mm, range 0.5-3.5 mm). In addition, there were significant regional differences in LA wall thickness. In particular, the LA roof was significantly thicker than the posterior wall and floor (P < 0.001), the LLR was significantly thicker than most regions (P < 0.04), and the mitral isthmus was also significantly thicker than the posterior wall (P < 0.001) and floor (P < 0.001)., Conclusions: In patients with persistent AF, there is inter- and intra-patient variability in the thickness of the LA muscular wall. In most patients, however, the roof, mitral isthmus, and the ridge between the pulmonary veins and appendage are thicker compared to the posterior wall and floor., (© 2011 Wiley Periodicals, Inc.)

Introduction: Left atrial geometry provided by preprocedural MRI/CT imaging studies is often used to guide pulmonary vein isolation. Rapid 3D reconstruction of the left atrium (LA) can be obtained using multielectrode catheters in conjunction with electro-anatomical mapping (EAM) and can also be used to guide ablation. The objective of this study is to assess the accuracy of electro-anatomical left atrial maps acquired with the multispine catheter by comparing them to CT and MRI images., Methods: Forty patients undergoing ablation for atrial fibrillation were studied. All patients underwent preprocedural CT/MRI imaging. 3D reconstructions of the LA were obtained using a multispine catheter with the Ensite/NavX mapping system. The operator was blinded to the results of the preprocedural imaging studies while acquiring the LA maps., Results: Mean map acquisition time was 10.3 ± 3.0 min. There was a strong correlation between maximum pulmonary vein (PV) ostial length and intervein distances measured on the electro-anatomical maps and on the CT/MRI images. Moreover, 11 patients had right middle PVs which were detected during map acquisition. Six out of nine (67%) early branches of the right inferior PV and three out of three (100%) early branches of right superior PV were also identified. In two patients, one branch of the left superior PV and one branch of the left inferior PV were not detected during mapping., Conclusion: Left atrial anatomical maps acquired using multielectrode catheters in conjunction with EAM are accurate and provide information regarding pulmonary vein dimensions and geometry which is similar to that obtained with CT/MR imaging.

Introduction: pulmonary veins (PV) play an important role in the arrhythmogenesis of atrial fibrillation (AF). Catheter-based PV isolation is one of the primary treatments for symptomatic drug refractory AF. Following electrical isolation, isolated rhythms in the PV are encountered. The aim of this study was to assess the frequency of postisolation PV activity and classify the different rhythms observed., Methods and Results: this single center prospective study sought to assess the dissociated activity in the PVs following their isolation during AF ablation. In 100 consecutive patients (60 paroxysmal, 40 persistent) undergoing AF ablation, dissociated PV activity was recorded using a multielectrode mapping catheter following antral PV isolation. The dissociated PV activity was classified as (1) silent, (2) isolated ectopic beats, (3) ectopic rhythm, and (4) PV fibrillation. All the PVs were successfully isolated in all the patients. In 91 of 100 patients, there was dissociated activity in at least 1 isolated ipsilateral PV group. There was no significant difference in spontaneous PV activity between patients with paroxysmal and persistent AF (91.7% vs 90%, P = 1.0). Among the 200 isolated ipsilateral PV groups, 64 of 200 (32%) were silent, 86 of 200 (43%) demonstrated isolated ectopic beats, 41 of 200 (20.5%) had ectopic rhythms and 9 of 200 (4.5%) had PV fibrillation. The average cycle length of the PV ectopic rhythm was 2594 ± 966 ms (range 1193-4750 ms)., Conclusions: following PV isolation, a majority of patients demonstrate dissociated activity in at least 1 PV. This finding was evident in patients with both paroxysmal and persistent AF.

Objectives: This study is a meta-analysis of prospective cohort studies comparing the impact of cardiac resynchronization therapy (CRT) for patients in atrial fibrillation (AF) and sinus rhythm (SR)., Background: Although close to one-third of advanced heart failure patients exhibit AF, the impact of CRT in this group remains unclear., Methods: Prospective cohort studies comparing patients in normal SR and chronic AF treated with CRT were included. All studies reported death, New York Heart Association functional class, ejection fraction, 6-min walk test, and the Minnesota score or its equivalent as outcomes. Data sources included Ovid MEDLINE In-Process & Other Non-Indexed Citations, the Cochrane Central Register of Controlled Trials, the Database of Abstracts of Reviews of Effects, and the American College of Physicians Journal Club., Results: Of 2,487 reports identified, 5 studies following a total of 1,164 patients were included. Both AF and SR patients benefited significantly from CRT. Mortality was not significantly different at 1 year (relative risk ratio: 1.57, 95% confidence interval [CI]: 0.87 to 2.81). The New York Heart Association functional class improved similarly for both groups (-0.90 for SR patients, -0.84 for AF patients). SR patients showed greater relative improvement in the 6-min walk test (11.6 m greater, 95% CI: 10.4 to 12.8 m) and the Minnesota score (3.9 points less, 95% CI: 3.4 to 4.5 points) than AF patients. AF patients, however, achieved a small but statistically significant greater change in ejection fraction (0.39% greater change in ejection fraction, 95% CI: 0.22% to 0.55%)., Conclusions: Patients in AF show significant improvement after CRT, with similar or improved ejection fraction as SR patients, but smaller benefits in regard to functional outcomes.

Introduction: With the increasing use of pre-procedural imaging techniques such as magnetic resonance imaging (MRI) and their integration with electroanatomic mapping systems in catheter ablation for atrial fibrillation (AF), atypical anatomy of the pulmonary veins (PV), left atrium (LA) and their relationship to the thoracic aorta is increasingly recognized., Objective: To characterize atypical LA-PV anatomies revealed by pre-procedural MRI and their impact on the safety and efficacy of AF ablation procedures., Materials and Methods: We reported four patients who underwent AF ablation in our electrophysiology laboratory within the last year who had atypical LA-PV anatomy due to aorta compression recognized by pre-procedural three-dimensional (3D) MRI and anatomic segmentation. Twelve matched control cases without aorta compression were selected for comparison of LA-PV measurements., Results: All four patients in this study had a normal-sized descending thoracic aorta that compressed the left atrium, and all patients had evidence of left inferior PV narrowing secondary to external compression. Two patients also had anterior LA compression leading to posteriorly displaced interatrial septum. Isolation was not achieved in some PVs due to anatomic restraints, concern regarding risks of aortic injury and worsening pulmonary vein stenosis. There were no immediate or short-term complications., Conclusions: Extrinsic compression by the descending aorta on the LA and PV leading to LA compression and/or preexisting PV stenosis is uncommon but has potentially important implications on the overall safety and efficacy of AF ablation procedures. Pre-procedural imaging plays an important role in assessing such anatomic variations and planning of the procedures in order to minimize the risk of PV stenosis and aortic injury.

Objective: This study assesses the direct (medical and drugs) and indirect (work loss) annual costs associated with Atrial Fibrillation (AFIB) in a privately insured population., Background: AFIB is the most common sustained rhythm disturbance, affecting 2.3 million people in the United States., Methods: Cost and co-morbidity measures for AFIB patients were compared to matched controls using a privately insured administrative database (including medical, drug, and disability claims) for 2 million enrollees, 1999-2002 from 16 employers across the United States. Patients with an AFIB diagnosis on at least two occasions were included in the co-morbidity analysis (n = 3944). A non-AFIB control sample was randomly selected with a 1:1 ratio, with characteristics (i.e., age, gender, health plan) matched to AFIB patients. Excess medical costs (i.e., employer payments) were estimated for AFIB patients, defined as the difference in average annual costs between AFIB and control patients (n = 3944); excess work-loss costs were defined similarly for employees with available work-loss data (n = 603). Statistical significance in the descriptive analysis was measured by paired t-tests for cost, or Chi-square tests for co-morbidity comparisons. A two-part multivariate model of excess cost was further estimated to control for co-existing conditions and other patient characteristics. The excess costs of AFIB patients were estimated as the difference between the observed costs of AFIB patients and their estimated costs, assuming they did not have AFIB., Results: The multivariate analysis found that the excess annual direct cost of AFIB was $12,349 (p < 0.01), with AFIB patients approximately 5 times as costly as non-AFIB individuals ($15,553 versus $3204, respectively). The excess annual total cost was $14,875 (p < 0.01), with AFIB patients again approximately 5 times as costly as non-AFIB individuals ($18,454 versus $3,579, respectively). AFIB was associated with increased incidence of atrial flutter (p < 0.01), heart failure (Relative Risk (RR) = 29, p < 0.01), other arrhythmias/conduction disorders (RR = 16, p < 0.01), heart attack (RR = 8, p < 0.01), and stroke (RR = 6, p < 0.01)., Conclusions: AFIB is a costly disease and one for which more definitive therapies might offer some potential for reducing, not only the clinical impact, but also the economic burden of the disease.

Objectives: The purpose of this study was to demonstrate a method for successful and safe release of an entrapped circular catheter., Background: Segmental pulmonary vein (PV) isolation is widely practiced for patients with symptomatic drug-refractory atrial fibrillation. A circular mapping catheter is sometimes used with this technique to map the electrical connection between the left atrium (LA) and the PVs. This catheter reportedly can become entrapped in the mitral valve apparatus. Attempts to free the entrapped catheter can result in serious complications, including damage to the mitral valve chordae tendineae or fracture of the catheter itself., Methods: Three patients were referred for PV isolation for atrial fibrillation. A circular mapping catheter was used to map the sites of LA-PV electrical connections., Results: During the procedure, the circular mapping catheter became entrapped in the mitral valve apparatus in two patients and in the PV in one patient. A series of maneuvers, which included use of another catheter and guiding sheaths as well as pushing forward rather than pulling back on the entrapped catheter, allowed safe and successful release of the entrapped catheter in all patients., Conclusions: Entrapment of the circular mapping in the mitral valve apparatus or the PVs during PV isolation is a rare complication associated with use this catheter. We describe a series of maneuvers that may allow safe and successful release of the entrapped catheter.

Introduction: Pulmonary vein (PV) isolation for atrial fibrillation (AF) can be performed using a segmental ostial or a circumferential extra-ostial approach. The relative merits and potential limitations of each approach are currently debated. Here we report our early experience with each of these approaches, including their relative efficacy and safety., Methods and Results: Forty patients with drug-refractory AF underwent segmental ostial PV isolation and were compared to 40 consecutive patients who underwent PV isolation using a circumferential extra-ostial approach. The latter approach described here is novel in two aspects: (1) the endpoint for ablation was PV isolation and not only delay in left atrial to PV conduction time, and (2) isolation of the right and left PVs was achieved by a single encirclement of ipsilateral veins. At follow-up, 60% of the patients in the segmental group were free of AF compared to 75% of the patients in the circumferential group. There was one thromboembolic cerebrovascular complication during the ablation procedure in each group., Conclusion: PV isolation using a circumferential extra-ostial approach, where the ipsilateral PVs are isolated together by one encircling line of block using electroanatomic mapping, is a technically feasible procedure. This approach is at least as effective and safe as the more established segmental ostial approach for AF ablation.

Introduction: Pulmonary vein (PV) isolation for atrial fibrillation (AF) currently is performed using either an ostial or an extra-ostial approach. The objective of this study was to analyze by three-dimensional (3D) magnetic resonance angiography (MRA) the anatomy of the PVs in order to detect structural variability that would impact the choice of ablation approach., Methods and Results: Three-dimensional MRA was performed in 105 patients undergoing PV isolation. The ostial diameter, branching pattern, and PV angulation were analyzed. Fifty-nine (56%) patients had the typical pattern of 4 PVs with 4 separate ostia, 30 (29%) patients had an additional PV, and 18 (17%) patients had a left common PV trunk. In two patients, there were three right-sided veins and a common left-sided trunk, giving rise to four ostia: three on the right and one on the left. Two different populations of right middle PVs were noted: one where the additional vein projected anteriorly to drain the right middle lobe and one posterior to drain the superior portion of the right lower lobe. The average intrapatient variability in PV diameter was 7.9 +/- 4.2 mm. The PV ostium was <10 mm in 26 (25%) patients and >25 mm in 15 (14%) patients. The first branch originated 6.7 +/- 2.3 mm from the ostium. The left superior, right superior, right inferior, and left inferior PVs were found to enter the left atrium at the following angles: 32 +/- 13 degrees, 131 +/- 11 degrees, 206 +/- 16 degrees, and 329 +/- 14 degrees, respectively. Forty-nine patients (47%) had at least one funnel shaped PV., Conclusion: This largest PV imaging study to date demonstrates that MRA is a valuable tool that allows detection of marked intrapatient and interpatient anatomic variability of the PVs. These findings suggest that, at least in some patients, circumferential extra-ostial left atrial encirclement of the PVs may be preferable to ostial PV isolation. These findings also may have significant implications on the future development of coil- and balloon-based catheter ablation designs for AF ablation.

Objectives: We report an in-depth postmortem morphologic analysis of atrial myocardium in human pulmonary veins (PVs) from patients with and without atrial fibrillation (AF)., Background: Electrophysiologic studies established the critical role of PVs in the initiation of AF. To date, a paucity of data exists about PV morphology as an arrhythmogenic substrate., Methods: Longitudinal tissue-strips of PVs were excised and histologically analyzed from the distal part to just beyond the atriovenous junction in the left atrium from 20 patients, obtained at autopsy. Anatomical measurements, including diameters, lengths, and wall-thicknesses of PVs, obtained at autopsy, were made., Results: Histological analysis revealed extension of atrial myocardium into 89% of all PVs. Prevalence of myocardial extension was significantly higher in veins of 6 patients with compared with 14 patients without AF. Other significant differences in the histology of PVs between the two groups were a higher frequency of discontinuity and hypertrophy and a higher degree of fibrosis of the atrial myocardium in the PVs of patients with AF. A marked variation existed in anatomical dimensions of PVs, although no differences were observed between patients with or without AF., Conclusions: Atrial myocardium was more often present in the PVs of patients with compared with patients without AF. In the first group, the atrial myocardium in the PVs was characterized by more severe discontinuity, hypertrophy, and fibrosis. A marked variation in anatomical dimensions of the PVs existed.

It has been reported that conduction over the fast and slow pathways of the AV node can occur simultaneously, leading to a double ventricular response from each atrial beat. We report the cases of two patients referred to us for evaluation of symptomatic, incessant, and irregular narrow-complex tachycardia, misdiagnosed as atrial fibrillation, for consideration of pulmonary vein isolation. At presentation, careful evaluation of the electrograms revealed the presence of two ventricular activations for each atrial beat. At electrophysiologic study, both patients were found to have nonreentrant tachycardias arising from simultaneous conduction over the fast and slow pathways of the AV node. In one patient, the tachycardia had resulted in cardiomyopathy. Slow AV nodal pathway ablation performed in both patients resulted in cure of their tachycardias and recovery of ventricular function in the patient with cardiomyopathy.

Ectopic beats triggering atrial fibrillation may arise from atrial myocardial extensions in the pulmonary veins, superior vena cava, coronary sinus, and vein of Marshall. We report two patients with paroxysmal atrial fibrillation initiated by ectopic beats originating from the inferior vena cava. The foci responsible for the ectopic beats were located and ablated, resulting in elimination of atrial fibrillation. Ectopic beats originating from the os of the inferior vena cava can result in atrial fibrillation. This finding may explain the recurrence of atrial fibrillation in some patients after pulmonary vein isolation.

Nonpharmacological treatment for atrial fibrillation (AF) has evolved dramatically over the past 20 years. Pulmonary vein isolation, a catheter ablation technique developed in the last decade, prevents focal triggers in the pulmonary veins from initiating episodes of AF. Although the procedure initially involved focal ablation with a catheter directly in the pulmonary veins, investigators subsequently found that isolating the pulmonary veins by applying ablation energy at their junction with the left atrium is more effective. After the procedure is performed once or twice, it is 70% to 80% successful in preventing recurrence of AF episodes in the first year of follow-up. The pulmonary vein isolation procedure is most suitable for patients whose recurring symptomatic episodes of AF have not been suppressed by antiarrhythmic drugs or who do not wish to take long-term antiarrhythmic or anticoagulation medications. The procedure is more successful in patients with intermittent (paroxysmal) AF than in those with long-standing, continuous (chronic) AF.

Background: Little is known about national patterns of pharmacological treatment of atrial fibrillation, in particular, use of medications for ventricular rate control and for restoration and maintenance of sinus rhythm., Methods: We analyzed 1555 visits by patients with atrial fibrillation to randomly selected office-based US physicians included in National Ambulatory Medical Care surveys conducted in 1980, 1981, 1985, and 1989 through 1996. To determine national trends, we evaluated the proportion of atrial fibrillation visits with reported use of rate control medications (digoxin and antiarrhythmics in classes II and IV) and sinus rhythm medications (classes IA, IC, and III)., Results: The use of rate control agents decreased from 79% of atrial fibrillation visits in 1980-1981 to 62% in 1994-1996. Declining use was noted for both digoxin (76% in 1980-1981 to 53% in 1994-1996) and beta-blockers (19%-13%). After their introduction, the use of verapamil hydrochloride and diltiazem hydrochloride increased to 15% of atrial fibrillation visits in 1994-1996. Sinus rhythm agent use decreased from 18% of visits in 1980-1981 to 4% in 1992-1993 and then rose to 13% in 1994-1996. The use of class IA agents declined from 18% in 1980-1981 to 3.5% in 1992-1993 and then increased to 8% in 1994-1996. Quinidine remained the most widely used sinus rhythm medication, despite its declining share of this category. Newly available sotalol hydrochloride and amiodarone hydrochloride were used in 3.6% of visits in 1994-1996., Conclusions: Despite changes in the treatment of atrial fibrillation, digoxin remains the dominant rate control medication. Medications for sinus rhythm maintenance are not widely used. Quinidine use declined prominently in the 1980s, possibly because of concerns about proarrhythmic effects. The use of sinus rhythm agents, however, is now rising.

The limited efficacy and proarrhythmic risks of antiarrhythmic drug therapies for atrial fibrillation have led to the exploration of a wide spectrum of alternative therapeutic approaches. The diversity of the approaches is warranted by the current absence of a single procedure that can safely and effectively cure atrial fibrillation. The interventional therapies that are currently under most active development include implantable atrial defibrillator therapy, prophylactic atrial pacing in combination with drug therapy, multisite regional pace-entrainment of atrial fibrillation by rapid pacing, atrial surgery, and catheter ablation for atrial fibrillation. The current limitations of these procedures include: (1) for the implantable atrial defibrillator--patient tolerance of low energy shocks and early recurrence of atrial fibrillation; (2) for prophylactic pacing-limited efficacy in a small proportion of the total atrial fibrillation population; (3) for multisite regional pace-entrainment--lack of proved efficacy and difficulty in the expansion and merging of the entrained regions; (4) for atrial surgery--highly invasive as a stand-alone procedure; and (5) for catheter ablation-lack of proved long-term efficacy, shortcomings of currently available technology, and risk of thromboembolic stroke. It is evident that more basic and clinical research as well as technologic innovation are needed. However, it is likely that some of these new therapies, possibly in combination with antiarrhythmic drug therapy, will offer considerable clinical benefit to selected patients with symptomatic atrial fibrillation.

Transvenous atrial defibrillation with multiple atrial lead systems has been shown to be effective in models without the potential for ventricular arrhythmias. The specific aim of this study was to evaluate the efficacy and safety of transvenous single lead atrial defibrillation in a canine model of ischemic cardiomyopathy. Ten dogs had ischemic cardiomyopathy induced by repeated intracoronary microsphere injections. The mean LV ejection fraction decreased from 71% +/- 9% to 38% +/- 14% (P = 0.003). Spontaneous atrial fibrillation (AF) developed in four dogs, and in six AF was induced electrically. Atrial defibrillation thresholds (ADFTs) were determined with synchronous low energy shocks using a transvenous tripolar lead with two defibrillation coils (right ventricle, superior vena cava) and an integrated sensing lead (RV coil vs electrode tip). The ADFTs derived by logistic regression were compared at 50% and 90% probability of success (ED50, ED90): ED50 was 2.4 +/- 1.7 J and 2.9 +/- 2.1 J, respectively, for 5- and 10-ms monophasic shocks, and 1.8 +/- 0.9 J, respectively, for 5- and 10-ms biphasic shocks. Immediately after 3 of 2,179 (0.1%) synchronized shocks, ventricular fibrillation (VF) developed. VF was induced in 3 of 1,062 (0.3%) shocks with integrated sensing (RV coil vs electrode tip) compared to 0 of 1,117 shocks when a separate bipolar RV sensing electrode was used for synchronization. In our canine model of ischemic cardiomyopathy, low energy atrial defibrillation via a transvenous single lead system was highly effective. However, there was a small but definite risk of VF induction, which seemed to be greater when an integrated as opposed to a true bipolar RV sensing was used.

Catheter ablation for atrial fibrillation is based upon the critical mass of fibrillation hypothesis and aims to compartmentalize the atria by the creation of linear lesions, thereby reducing the amount of contiguous myocardium available for the propagation of multiple activation wavefronts. Early attempts at creating right atrial linear lesions with conventional catheter tip technology to treat patients with chronic and paroxysmal atrial fibrillation yielded disappointing results. Although more efficacious, the creation of extensive left atrial lesions has been associated with a high rate of thromboembolic stroke despite the administration of heparin and use of temperature feedback to control radiofrequency energy. Approaches to reduce the risk of stroke include: the creation of more continuous and effective right atrial lesions with linear array catheter technology and thereby reduce the requirement for left atrial ablation; the assessment of adjuvant pharmacological agents to inhibit platelet aggregation; guidance of radiofrequency energy delivery by intracardiac echo; assessment of transvenous cryotherapy as an alternative to radiofrequency energy in order to reduce endocardial disruption; and development of minimally invasive surgical approaches to left atrial epicardial ablation.

Objectives: We studied the duration and prognostic significance of atrial arrhythmias in the denervated transplanted heart, specifically the occurrence of atrial fibrillation in the absence of vagal modulation., Background: Substantial animal data indicate that vagally induced dispersion of atrial refractoriness plays a central role in the induction and maintenance of atrial fibrillation., Methods: We studied the occurrence of atrial arrhythmias in the denervated hearts of 88 consecutive orthotopic transplantations in 85 patients by means of continuous telemetry and all available electrocardiographic tracings., Results: Fifty percent of recipients (44 of 88) developed at least one atrial arrhythmia. Atrial fibrillation occurred 23 times (21 recipients), atrial flutter 39 times (26 recipients), ectopic atrial tachycardia 3 times (3 recipients) and supraventricular tachycardia 18 times (11 recipients). The number of atrial fibrillation and atrial flutter episodes did not differ (23 vs. 39, p = 0.072), but the mean duration of atrial flutter was longer than that of atrial fibrillation (37.0 +/- 10 vs. 6.6 +/- 3.6 h, p = 0.014). Atrial fibrillation was associated with an increased risk of subsequent death (10 of 21 recipients with vs. 15 of 67 without atrial fibrillation, risk ratio 3.15 +/- 0.18, p = 0.005 by Cox proportional hazards model). All 5 recipients who developed "late" atrial fibrillation (> 2 weeks after transplantation) died versus 5 of 16 who developed atrial fibrillation within the first 2 weeks (p = 0.007). Causes of death included rejection (three recipients), allograft failure (two recipients), infection (three recipients) and multiorgan failure (two recipients). Atrial fibrillation was not associated with age, gender, ischemic time, reason for transplantation, echocardiographic variables, invasive hemodynamic variables or biopsy grade. Mean time from atrial arrhythmia to echocardiography was 2.7 +/- 3.3 days; that to biopsy was 4.8 +/- 6.3 days. Atrial flutter was not associated with subsequent death. Only 7 (15.9%) of 44 recipients demonstrated moderate or severe allograft rejection at the time of the arrhythmia., Conclusions: Atrial arrhythmias occur frequently in the denervated transplanted heart, often in the absence of significant rejection. Late atrial fibrillation may be associated with an increased all-cause mortality.

Objectives: In this study, the feasibility, efficacy and safety of low energy internal atrial cardioversion were investigated in a sheep model. The relation between the level of energy used for atrial defibrillation and the probability of successful cardioversion was examined., Background: Atrial fibrillation is a common clinical arrhythmia that frequently recurs after termination with high energy external cardioversion. In some patients with drug-refractory and poorly tolerated atrial fibrillation, an automatic implantable cardioverter may prove useful by providing rapid restoration of sinus rhythm., Methods: In 16 pentobarbital-anesthetized sheep, a right atrial spring electrode was implanted percutaneously and a left thoracic cutaneous patch electrode was placed on the thorax. Sustained atrial fibrillation was induced by rapid atrial pacing and terminated by biphasic cathodal shocks synchronized to the R wave of the surface electrocardiogram (ECG)., Results: During 768 defibrillation attempts in 16 sheep, the percent of successful cardioversion attempts increased in a dose-response manner, reaching a plateau at the average energy level of 5 J. With greater than or equal to 1.5 and greater than or equal to 2.5 J energy levels, cardioversion was achieved, respectively, in greater than 50% and greater than 80% of attempts. Ventricular fibrillation occurred in 18 (2.4%) of 768 cardioversion attempts; in all 18 cases, the shock was poorly synchronized with the ECG R wave., Conclusions: Low energy cardioversion of atrial fibrillation to sinus rhythm is feasible with use of a right atrial spring/cutaneous patch electrode configuration. The percent of successful cardioversion attempts depends on the level of energy output, and there is a risk of ventricular fibrillation if cardioversion is poorly synchronized with ventricular depolarization.