Implication of ventricular pacing burden and atrial pacing therapies on the progression of atrial fibrillation: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Atrial fibrillation (AF) is common after pacemaker implantation. However, the impact of pacemaker algorithms in AF prevention is not well understood.

OBJECTIVE

The purpose of this study was to evaluate the role of pacing algorithms in preventing AF progression.

METHODS

A systematic search of articles using the PubMed and Embase databases resulted in a total of 754 references. After exclusions, 21 randomized controlled trials (8336 patients) were analyzed, comprising studies reporting ventricular pacing percentage (VP%) (AAI vs DDD, n = 1; reducing ventricular pacing [RedVP] algorithms, n = 2); and atrial pacing therapies (atrial preference pacing [APP], n = 14; atrial antitachycardia pacing [aATP]+APP, n = 3; RedVP+APP+aATP, n = 1).

RESULTS

Low VP% (<10%) lead to a nonsignificant reduction in the progression of AF (hazard ratio [HR] 0.80; 95% confidence interval [CI] 0.57-1.13; P = .21; I² = 67%) compared to high VP% (>10%). APP algorithm reduced premature atrial complexes (PAC) burden (mean difference [MD] -1117.74; 95% CI -1852.36 to -383.11; P = .003; I² = 67%) but did not decrease AF burden (MD 8.20; 95% CI -5.39 to 21.80; P = .24; I² = 17%) or AF episodes (MD 0.00; 95% CI -0.24 to 0.25; P = .98; I² = 0%). Similarly, aATP+APP programming showed no significant difference in AF progression (odds ratio 0.65; 95% CI 0.36-1.14; P = .13; I² = 61%). No serious adverse events related to algorithm were reported.

CONCLUSION

This meta-analysis of randomized controlled trials demonstrated that algorithms to reduce VP% can be considered safe. Low burden VP% did not significantly suppress AF progression. The atrial pacing therapy algorithms could suppress PAC burden but did not prevent AF progression.

Contact force and ablation assessment of surgical bipolar radiofrequency clamps in the treatment of atrial fibrillation

OBJECTIVES

Atrial fibrillation is treated surgically by creating conduction block lesions. Radiofrequency (RF) lesions have reduced efficacy compared to 'cut-and-sew'. Catheter ablation studies demonstrate a relationship between lesion depth and contact force. We hypothesized that contact force and lesion depth are dependent on design of the bipolar surgical RF clamps.

METHODS

Hinged and parallel jaw style RF clamps were studied. Muscle samples were clamped with pressure-sensitive film at increasing tissue thicknesses. Films were analysed determining clamp pressure profiles. A sheep model was utilized for ablation testing using each clamp style until the device indicated transmurality. Separate muscle areas had 1, 2 or 3 burns applied. The muscle was excised, sectioned every 1 cm and stained for lesion depth and fat thickness analysis.

RESULTS

Pressure profiling comparing the proximal and distal segments of each clamp style demonstrated only one statistically significant difference in the parallel clamp; the hinged clamp had statistically significant differences (P ≤ 0.03) for all tissue thicknesses. There was no evidence for differences in the proximal lesion depth of both clamps (P = 0.13) but deeper distally in the parallel clamp (10.17 mm vs 8.02 mm, P = 0.003). The logistic regression analysis demonstrated increased odds of transmurality with parallel clamps at 1, 2 or 3 burns (P = 0.03, P = 0.003 and P = 0.002). Every 1 mm increase in overlying fat decreased likelihood of transmurality by 11% (P < 0.05).

CONCLUSIONS

The parallel and hinged clamps have different pressure profiles with higher likelihood of transmurality using the parallel clamp. Fat reduces the ability of RF to deliver a transmural lesion. These findings have implications for optimal surgical RF ablation technique.

Role of autonomic nervous system in atrial fibrillation

Atrial fibrillation is the most common sustained arrhythmia and is associated with significant morbidity and mortality. The autonomic nervous system has a significant role in the milieu predisposing to the triggers, perpetuators and substrate for atrial fibrillation. It has direct electrophysiological effects and causes alterations in atrial structure. In a significant portion of patients with atrial fibrillation, the autonomic nervous system activity is likely a composite of reflex excitation due to atrial fibrillation itself and contribution of concomitant risk factors such as hypertension, obesity and sleep-disordered breathing. We review the role of autonomic nervous system activation, with focus on changes in reflex control during atrial fibrillation and the role of combined sympatho-vagal activation for atrial fibrillation initiation, maintenance and progression. Finally, we discuss the potential impact of combined aggressive risk factor management as a strategy to modify the autonomic nervous system in patients with atrial fibrillation and to reverse the arrhythmogenic substrate.

Rehospitalizations for complications and mortality following pacemaker implantation: A retrospective cohort study in an older population

INTRODUCTION

A large number of older people receive pacemakers each year but broad population-based studies that describe complications following pacemaker implantation in this population are lacking.

METHODS

We conducted a retrospective cohort study using data from the Australian Government Department of Veterans' Affairs database. The cohort consisted of patients who received a pacemaker from 2005 to 2014. The outcomes were subsequent rehospitalizations for infections, procedure-related complications, thromboembolism, cardiovascular events (heart failure, myocardial infarction, and atrial fibrillation), and reoperation of pacemaker, and mortality.

RESULTS

There were 10 883 pacemakers recipients, the median age was 86 years (interquartile range 83-89), 61% were males, and 74% received a dual-chamber pacemaker. Within 90 days postdischarge, rehospitalizations were occasioned by pacemaker infection in 0.5%, device-related complications in 1.5%, cerebral infarction in 0.7%, and heart failure in 6% of single-chamber pacemaker recipients. In dual-chamber pacemaker recipients rehospitalizations were occasioned by pacemaker infection in 0.4%, septicemia in 0.4%, device-related complications in 1.2%, cerebral infarction in 0.3%, and heart failure in 3%. Rehospitalizations for pacemaker adjustment occurred in 1.5% of patients. The 90-day postdischarge mortality was 5% and 3% in patients with single- and dual-chamber pacemaker, respectively.

CONCLUSION

Rehospitalizations for infection, procedure-related complications, or thromboembolism occurred in 1% to 2% of patients within 90 days postdischarge, while 10% of single chamber and 7% of dual-chamber recipients experienced a rehospitalization for a cardiovascular event.

Mitral valve prolapse and sudden cardiac death: a systematic review and meta-analysis

OBJECTIVES

Mitral valve prolapse (MVP) is commonly observed as a benign finding. However, the literature suggests that it may be associated with sudden cardiac death (SCD). We performed a meta-analysis and systematic review to determine the: (1) prevalence of MVP in the general population; (2) prevalence of MVP in all SCD and unexplained SCD; (3) incidence of SCD in MVP and (4) risk factors for SCD.

METHODS

The English medical literature was searched for: (1) MVP community prevalence; (2) MVP prevalence in SCD cohorts; (3) incidence SCD in MVP and (4) SCD risk factors in MVP. Thirty-four studies were identified for inclusion. This study was registered with PROSPERO (CRD42018089502).

RESULTS

The prevalence of MVP was 1.2% (95% CI 0.5 to 2.0) in community populations. Among SCD victims, the cause of death remained undetermined in 22.1% (95% CI 13.4 to 30.7); of these, MVP was observed in 11.7% (95% CI 5.8 to 19.1). The incidence of SCD in the MVP population was 0.14% (95% CI 0.1 to 0.3) per year. Potential risk factors for SCD include bileaflet prolapse, ventricular fibrosis complex ventricular ectopy and ST-T wave abnormalities.

CONCLUSION

The high prevalence of MVP in cohorts of unexplained SCD despite low population prevalence provides indirect evidence of an association of MVP with SCD. The absolute number of people exposed to the risk of SCD is significant, although the incidence of life-threatening arrhythmic events in the general MVP population remains low. High-risk features include bileaflet prolapse, ventricular fibrosis, ST-T wave abnormalities and frequent complex ventricular ectopy.

TRIAL REGISTRATION

PROSPERO (CRD42018089502).

Targeting the Substrate in Ablation of Persistent Atrial Fibrillation: Recent Lessons and Future Directions

While isolation of the pulmonary veins is firmly established as effective treatment for the majority of paroxysmal atrial fibrillation (AF) patients, there is recognition that patients with persistent AF have substrate for perpetuation of arrhythmia existing outside of the pulmonary veins. Various computational approaches have been used to identify targets for effective ablation of persistent AF. This paper aims to discuss the clinical aspects of computational approaches that aim to identify critical sites for treatment. Various analyses of electrogram characteristics have been performed with this aim. Leading techniques for electrogram analysis are Complex Fractionated Atrial Electrograms (CFAE) and Dominant Frequency (DF). These techniques have been the subject of clinical trials of which the results are discussed. Evaluation of the activation patterns of atria in AF has been another avenue of research. Focal Impulse and Rotor Modulation (FIRM) mapping and forms of Body Surface Mapping aim to characterize multiple atrial wavelets, macro-reentry and focal sources which have been proposed as basic mechanisms perpetuating AF. Both invasive and non-invasive activation mapping techniques are reviewed. The presence of atrial fibrosis causes non-uniform anisotropic impulse propagation. Therefore, identification of fibrosis by imaging techniques is an avenue of potential research. The leading contender for imaging-based techniques is Cardiac Magnetic Resonance (CMR). As this technology advances, improvements in resolution and scar identification have positioned CMR as the mode of choice for analysis of atrial structure. AF has been demonstrated to be associated with obesity, inactivity and diseases of modern life. An opportunity exists for detailed computational analysis of the impact of risk factor modification on atrial substrate. This ranges from microstructural investigation through to examination at a population level via registries and public health interventions. Computational analysis of atrial substrate has moved from basic science toward clinical application. Future directions and potential limitations of such analyses are examined in this review.

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

Atrial fibrillation (AF) and diseases of the cardiac conduction system frequently co-exist, and interactions between these rhythm disturbances can adversely impact patient outcomes. Concurrent AF and sinus node disease often manifests as the tachy-brady syndrome wherein the underlying sinus node dysfunction can pose a challenge to AF management. Similarly, the combination of AF and left bundle branch block increases mortality in individuals with co-existent heart failure and hampers effective delivery of cardiac resynchronization therapy. A thorough understanding of the therapeutic interventions available for these conditions, including the role of catheter ablation and permanent pacemaker programming, is crucial for optimal management in affected patients.

Efficacy of Therapies for Postural Tachycardia Syndrome: A Systematic Review and Meta-analysis

OBJECTIVE

To identify the evidence base and evaluate the efficacy of each treatment for postural tachycardia syndrome (POTS) in light of a recent consensus statement highlighting the lack of treatment options with clear benefit to risk ratios for this debilitating condition.

METHODS

The CENTRAL (Cochrane Central Register of Controlled Trials), PubMed, and Embase databases from inception to May 2017 were searched using the terms postural AND tachycardia AND syndrome. A total of 135 full-text publications were screened after excluding duplicates (n=681), conference abstracts (n=467), and records that did not relate to POTS therapy (n=876). We included 28 studies with at least 4 patients with POTS in which symptomatic response was reported after more than 4 weeks of therapy. This review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. Two investigators independently performed the data extraction and evaluated the quality of evidence.

RESULTS

This study comprised 25 case series and 3 small randomized controlled trials that evaluated 755 and 103 patients with POTS, respectively. Interventions directed at increasing intravascular volume, increasing peripheral or splanchnic vascular tone, controlling heart rate, and increasing exercise tolerance demonstrate moderate efficacy (range, 51%-72%). Few data exist on their comparative effectiveness. Significant heterogeneities were seen in terms of patient age, symptom severity, and the measures used to evaluate treatment efficacy.

CONCLUSION

The current evidence base to guide optimal management of patients with POTS is extremely limited. More high-quality collaborative research with standardized reporting of symptom response and treatment tolerability is urgently needed.

Predicted longevity of contemporary cardiac implantable electronic devices: A call for industry-wide "standardized" reporting

BACKGROUND

Battery longevity is an important factor that may influence the selection of cardiac implantable electronic devices (CIEDs). However, there remains a lack of industry-wide standardized reporting of predicted CIED longevity to facilitate informed decision-making for implanting physicians and payers.

OBJECTIVE

The purpose of this study was to compare the predicted longevity of current generation CIEDs using best-matched CIEDs settings to assess differences between brands and models.

METHODS

Data were extracted for current model pacemakers, implantable cardioverter-defibrillators (ICDs), and cardiac resynchronization therapy-defibrillators (CRT-Ds) from product manuals and, where absent, by communication with the manufacturers. Pacemaker longevity estimations were based on standardized pacing outputs (2.5V, 0.40-ms pulse width, 500-Ω impedance) and pacing loads of 50% or 100% at 60 bpm. ICD and CRT-D longevity were estimated at 0% pacing and 15% atrial plus 100% biventricular pacing, with essential capacitor reforms and zero clinical shocks.

RESULTS

Mean maximum predicted longevity of single- and dual-chamber pacemakers was 12.0 ± 2.1 and 9.8 ± 1.9 years, respectively. Use of advanced features such as remote monitoring, prearrhythmia electrogram storage, and rate response can result in ∼1.4 years of reduction in longevity. Mean maximum predicted longevity of ICDs and CRT-Ds was 12.4 ± 3.0 and 8.8 ± 2.1 years, respectively. Of note, there were significant variations in predicted CIED longevity according to device manufacturers, with up to 44%, 42%, and 44% difference for pacemakers, ICDs, and CRT-Ds, respectively.

CONCLUSION

Contemporary CIEDs demonstrate highly variable predicted longevity according to device manufacturers. This may impact on health care costs and long-term clinical outcomes.

Atrial remodeling and ectopic burden in recreational athletes: Implications for risk of atrial fibrillation

BACKGROUND

Atrial remodeling, vagal tone, and atrial ectopic triggers are suggested to contribute to increased incidence of atrial fibrillation (AF) in endurance athletes. How these parameters change with increased lifetime training hours is debated.

HYPOTHESIS

Atrial remodeling occurs in proportion to total training history, thus contributing to elevated risk of AF.

METHODS

We recruited 99 recreational endurance athletes, subsequently grouped according to lifetime training hours, to undergo evaluation of atrial size, autonomic modulation, and atrial ectopy. Athletes were grouped by self-reported lifetime training hours: low (<3000 h), medium (3000-6000 h), and high (>6000 h). Left atrial (LA) volume, left ventricular (LV) dimensions, and LV systolic and diastolic function were assessed by echocardiography. We used 48-hour ambulatory electrocardiographic monitoring to determine heart rate, heart rate variability, premature atrial contractions, and premature ventricular contractions.

RESULTS

LA volume was significantly greater in the high (+5.1 mL/m² , 95% CI: 1.3-8.9) and medium (+4.2 mL/m² , 95% CI: 0.2-8.1) groups, compared with the low group. LA dilation was observed in 19.4%, 12.9%, and 0% of the high, medium, and low groups, respectively (P = 0.05). No differences were observed between groups for measures of LV dimensions or function. Minimum heart rate, parasympathetic tone expressed using heart rate variability indices, and premature atrial contraction and premature ventricular contraction frequencies did not differ between groups.

CONCLUSIONS

In recreational endurance athletes, increased lifetime training is associated with LA dilation in the absence of increased vagal parameters or atrial ectopy, which may promote incidence of AF in this cohort.

Alcohol and incident atrial fibrillation - A systematic review and meta-analysis

BACKGROUND

Whilst high levels of alcohol consumption are known to be associated with atrial fibrillation (AF), it is unclear if any level of alcohol consumption can be recommended to prevent the onset of the condition. The aim of this review is to characterise the association between chronic alcohol intake and incident AF.

METHODS AND RESULTS

Electronic literature searches were undertaken using PubMed and Embase databases up to 1 February 2016 to identify studies examining the impact of alcohol on the risk of incident AF. Prospective studies reporting on at least three levels of alcohol intake and published in English were eligible for inclusion. Studies of a retrospective or case control design were excluded. The primary study outcome was development of incident AF. Consistent with previous studies, high levels of alcohol intake were associated with an increased incident AF risk (HR 1.34, 95% CI 1.20-1.49, p<0.001). Moderate levels of alcohol intake were associated with a heightened AF risk in males (HR 1.26, 95% CI 1.04-1.54, p=0.02) but not females (HR 1.03, 95% CI 0.86-1.25, p=0.74). Low alcohol intake, of up to 1 standard drink (SD) per day, was not associated with AF development (HR 0.95, 95% CI 0.85-1.06, p=0.37).

CONCLUSIONS

Low levels of alcohol intake are not associated with the development of AF. Gender differences exist in the association between moderate alcohol intake and AF with males demonstrating greater increases in risk, whilst high alcohol intake is associated with a heightened AF risk across both genders.

Oral Anticoagulation Therapy in Atrial Fibrillation Patients Managed in the Emergency Department Compared to Cardiology Outpatient: Opportunities for Improved Outcomes

INTRODUCTION

Recent registry data suggests oral anticoagulation (OAC) usage remains suboptimal in atrial fibrillation (AF) patients. The aim of our study was to determine if rates of appropriate use of OAC in individuals with AF differs between the emergency department (ED) and cardiac outpatient clinic (CO).

METHODS

This was a retrospective study of consecutive AF patients over a 12-month period. Data from clinical records, discharge summaries and outpatient letters were independently reviewed by two investigators. Appropriateness of OAC was assessed according to the CHA₂DS₂-VASc score.

RESULTS

Of 455 unique ED presentations with AF as a primary diagnosis, 115 patients who were treated and discharged from the ED were included. These were compared to 259 consecutively managed AF patients from the CO. Inappropriate OAC was significantly higher in the ED compared to the CO group (65 vs. 18%, p<0.001). Treatment in the ED was a significant multivariate predictor of inappropriate OAC (odds ratio 8.2 [4.8-17.7], p<0.001).

CONCLUSIONS

This patient level data highlights that significant opportunity exists to improve disparities in the use of guideline adherent therapy in the ED compared to CO. There is an urgent need for protocol-driven treatment in the ED or streamlined early follow-up in a specialised AF clinic to address this treatment gap.