Atrial fibrillation and conduction system disease: the roles of catheter ablation and permanent pacing

Three-year incidence of pacemaker implantation in patients with atrial fibrillation and sinus node dysfunction receiving ablation versus antiarrhythmic drugs

BACKGROUND

Sinus node dysfunction (SND) is commonly seen in patients with atrial fibrillation (AF). The purpose of this study was to compare the incidence of pacemaker implantation among patients with SND and AF treated with catheter ablation (CA) versus anti-arrhythmic drugs (AADs).

METHODS

The 2013-2022 Optum Clinformatics database, an administrative claims database for commercially insured individuals in the United States (US), was used for this study. Patients with AF and SND and a history of at least one AAD prescription were identified and classified into CA or AAD cohorts based on subsequent treatment received. Inverse probability treatment weighting was applied to balance socio-demographic and clinical characteristics between the cohorts. Weighted Cox regression modeling was used to evaluate the differential risk of incident permanent pacemaker (PPM) implantation. Sub-analyses were performed by AF type (paroxysmal versus persistent).

RESULTS

A total of 1206 patients in the AAD cohort and 1624 patients in the CA cohort were included. Study cohorts were well-balanced post-weighting. The incidence rate of PPM implantation (per 1000 person-year) was 55.8 for the CA cohort and 117.8 for the AAD cohort. Regression analysis demonstrated that the CA cohort had 42% lower risk of incident PPM implantation than those treated with AADs (hazard ratio [HR], 0.58; 95% CI, 0.46-0.72, p < 0.001). CA-treated patients had lower risks of PPM implantation versus AAD-treated patients among those with paroxysmal AF (HR, 0.48; 95% CI, 0.34-0.69, p < 0.001) and persistent AF (HR, 0.57; 95% CI, 0.40-0.81, p = 0.002).

CONCLUSIONS

Patients with AF and SND treated with CA have significantly lower risks of incident PPM implantation compared with those treated with an AAD.

Association of right bundle branch block or intraventricular conduction delay with recurrence of atrial fibrillation after catheter ablation

BACKGROUND

The association between bundle branch block (BBB) and recurrence of atrial fibrillation (AF) after catheter ablation is unclear. The aim of this study was to determine whether AF combined with BBB is associated with AF recurrence after catheter ablation.

METHODS

A total of 477 consecutive AF patients who underwent catheter ablation were included. The AF patients were divided into three groups according to BBB: AF without BBB (n = 427), AF with right bundle branch block (AF with RBBB) (n = 16), and AF with intraventricular conduction delay (AF with IVCD) (n = 34).

RESULTS

Of the 477 AF patients (mean age 57 years, 81% men, median CHA2 DS2 -VASc score of 1), 16 (3.4%) patients had RBBB, and 34 (7.1%) patients had IVCD. During a mean follow-up of 15.2 ± 6.7 months, 119 patients (24.9%) had recurrence of AF. Of these, 111 (26%) patients were in the AF without BBB group, with 2 (12.5%) and 6 (17.6%) patients in the RBBB and IVCD groups, respectively. The Kaplan-Meier estimate of the rate of recurrent AF was not significantly different among the three groups (p = .39). Multivariable analysis showed that persistent AF (HR 1.7, 95% CI 1.15-2.50, p = .007), chronic kidney disease (HR 2.94, 95% CI 1.20-7.17, p = .01), and left atrial diameter (HR 1.04, 95% CI 1.009-1.082, p = .01) were significantly associated with AF recurrence.

CONCLUSION

AF with BBB was not significantly associated with the recurrence of AF after catheter ablation in middle-aged patients with low-risk cardiovascular profile.

Histopathological changes in the electrical conduction of cardiac nodes after acute myocardial infarction in dogs and horses, compared with findings in humans: A histological, morphometrical, and immunohistochemical study

Background and Aim

The heart conduction system is responsible for the occurrence of various types of cardiac arrhythmia. This study aimed to histologically and morphometrically describe damaged cardiac nodes during acute myocardial infarction and to compare them with normal tissues in dogs and horses.

Materials and Methods

This study describes the morphometry of cardiac nodes in five dogs and five elderly horses that succumbed to sudden cardiac death (SCD). A computerized morphometric study was conducted to determine the number of cells composing the nodes, different shape and size parameters of nodes, and their relationship with degenerative changes due to cardiac conditions.

Results

In both species, the sinoatrial node (SAN) was ovoid in shape whereas the atrioventricular node (AVN) was pyramidal in shape. The percentage of collagen fibers inside the SAN of dogs (47%) and horses (50%) was found to be higher than that of cells. In contrast, the percentage of cells in the AVN of dogs (24%) and horses (16%) was higher than that of connective tissues. In the SAN, the area (p = 0.09), maximum diameter (<0.001), and mean diameter (0.003) of P cells were larger in dogs than in horses.

Conclusion

Overall, the SAN cells and surrounding cardiomyocytes in dogs and horses as well as the AVN cells in dogs that succumbed to SCD decreased in size compared with those in normal hearts.

Cardiac Magnetic Resonance Imaging-Derived Left Atrial Characteristics in Relation to Atrial Fibrillation Detection in Patients With an Implantable Cardioverter-Defibrillator

Background Among patients with an implantable cardioverter-defibrillator, a high prevalence of atrial fibrillation (AF) is present. Identification of AF predictors in this patient group is of clinical importance to initiate appropriate preventive therapeutic measures to reduce the risk of AF-related complications. This study assesses whether cardiac magnetic resonance imaging-derived atrial characteristics are associated with AF development in patients with a dual-chamber implantable cardioverter-defibrillator or cardiac resynchronization therapy defibrillator, as detected by the cardiac implantable electronic device. Methods and Results This single-center retrospective study included 233 patients without documented AF history at the moment of device implantation (dual-chamber implantable cardioverter-defibrillator [63.5%] or cardiac resynchronization therapy defibrillator [36.5%]). All patients underwent cardiac magnetic resonance imaging before device implantation. Cardiac magnetic resonance-derived features of left atrial (LA) remodeling were evaluated in all patients. Detection of AF episodes was based on cardiac implantable electronic device interrogation. During a median follow-up of 6.1 years, a newly diagnosed AF episode was detected in 88 of the 233 (37.8%) patients with an ICD. In these patients, increased LA volumes and impaired LA function (LA emptying fraction and LA strain) were found as compared with patients without AF during follow-up. However, a significant association was only found in patients with dilated cardiomyopathy and not in patients with ischemic cardiomyopathy. Conclusions LA remodeling characteristics were associated with development of AF in patients with dilated cardiomyopathy but not patients with ischemic cardiomyopathy, suggesting different mechanisms of AF development in ischemic cardiomyopathy and dilated cardiomyopathy. Assessment of LA remodeling before device implantation might identify high-risk patients for AF.

Reduction of mapping time in pulmonary vein isolation using atrial pacing during left atrial voltage map acquisition

INTRODUCTION

3D mapping systems are used during radiofrequency (RF) pulmonary vein isolation (PVI) to facilitate catheter navigation and to provide additional electroanatomical information as a surrogate marker for the presence and location of fibrotic atrial myocardium. Electric voltage information can only be measured when the myocardium is depolarized. Low heart rates or frequent premature atrial beats can significantly prolong creation of detailed left atrial voltage maps. This study was designed to evaluate the potential advantage of voltage information collection during atrial pacing instead of acquisition during sinus rhythm.

METHODS AND RESULTS

A total of 40 patients were included in the study, in 20 consecutive patients voltage mapping was performed during sinus rhythm, and in the following 20 patients during atrial pacing. The average age of the included patients was 69.5 ± 9.4, 17 of 40 patients (43%) were male. All procedures were performed using the Carto 3D Mapping system. For LA voltage mapping, a multipolar circular mapping catheter was used. The atrium was paced via the proximal coronary sinus catheter electrodes with a fixed cycle length of 600 ms. By mapping during atrial pacing mapping time was reduced by 35% (441 s. (±141) vs. 683 s. (±203) p = 0.029) while a higher number of total mapping points were acquired (908 ± 560 vs. 581 ± 150, p = 0.008).

CONCLUSION

Acquiring left atrial low voltage maps during atrial pacing significantly reduces mapping time. As pacing also improves comparability of left atrial electroanatomical maps we suggest that this approach may be considered as a standard during these procedures.

Atrial Fibrillation Is Associated With Syncope and Falls in Older Adults: A Systematic Review and Meta-analysis

OBJECTIVE

To examine the potential association of atrial fibrillation (AF) to syncope and falls, we undertook a systematic review and meta-analysis given the increasing prevalence of AF in older adults as well as emerging data that it is a risk factor for dementia.

PATIENTS AND METHODS

CENTRAL, PubMed, and EMBASE databases were searched from inception to January 31, 2019, to retrieve relevant studies. Search terms consisted of MeSH, tree headings, and keywords relating patients with "AF," "falls," "syncope," and "postural hypotension." When possible; results were pooled using a random-effects model.

RESULTS

A total of 10 studies were included, with 7 studies (36,444 patients; mean ± SD age, 72±10 years) reporting an association between AF and falls and 3 studies (6769 patients; mean ± SD age, 65±3 years) reporting an association between AF and syncope. Pooled analyses demonstrate that AF is independently associated with falls (odds ratio, 1.19; 95% CI, 1.07-1.33; P=.001) and syncope (odds ratio, 1.88; 95% CI, 1.20-2.94; P=.006). There was overall moderate bias and low-moderate heterogeneity (I²=37%; P=.11) for falls and moderate bias with low statistical heterogeneity (I²=0%; P=.44) for syncope. Persistent AF, but not paroxysmal AF, was associated with orthostatic intolerance in 1 study (4408 patients; mean ± SD age, 66±6 years).

CONCLUSION

AF is independently associated with syncope and falls in older adults. Further studies are needed to delineate mechanistic links and to guide management to improve outcomes in these patients.

TRIAL REGISTRATION

PROSPERO: trial identifier: CRD4201810721.

Canine and human sinoatrial node: differences and similarities in the structure, function, molecular profiles, and arrhythmia

The sinoatrial node (SAN) is the primary pacemaker in canine and human hearts. The SAN in both species has a unique three-dimensional heterogeneous structure characterized by small pacemaker myocytes enmeshed within fibrotic strands, which partially insulate the cells from aberrant atrial activation. The SAN pacemaker tissue expresses a unique signature of proteins and receptors that mediate SAN automaticity, ion channel currents, and cell-to-cell communication, which are predominantly similar in both species. Recent intramural optical mapping, integrated with structural and molecular studies, has revealed the existence of up to five specialized SAN conduction pathways that preferentially conduct electrical activation to atrial tissues. The intrinsic heart rate, intranodal leading pacemaker shifts, and changes in conduction in response to physiological and pathophysiological stimuli are similar. Structural and/or functional impairments due to cardiac diseases including heart failure cause SAN dysfunctions (SNDs) in both species. These dysfunctions are usually manifested as severe bradycardia, tachy-brady arrhythmias, and conduction abnormalities including exit block and SAN reentry, which could lead to atrial tachycardia and fibrillation, cardiac arrest, and heart failure. Pharmaceutical drugs and implantable pacemakers are only partially successful in managing SNDs, emphasizing a critical need to develop targeted mechanism-based therapies to treat SNDs. Because several structural and functional characteristics are similar between the canine and human SAN, research in these species may be mutually beneficial for developing novel treatment approaches. This review describes structural, functional, and molecular similarities and differences between the canine and human SAN, with special emphasis on arrhythmias and unique causal mechanisms of SND in diseased hearts.