Atrial Fibrillation in the Wolff-Parkinson-White Syndrome

Association of Atrial Fibrillation and/or Flutter With Adverse Cardiac Outcomes and Mortality in Patients With Wolff-Parkinson-White Syndrome

Background

Wolff-Parkinson-White (WPW) syndrome is characterized by the presence of accessory pathways and development of potentially malignant arrhythmias that can lead to sudden cardiac death. We aimed to determine the impact of atrial fibrillation and/or flutter (AF/AFL) on adverse cardiac outcomes and mortality in patients with WPW syndrome.

Methods

This study identified a cohort of Military Health System patients with WPW syndrome from January 1, 2014, to December 31, 2019. The cohort was divided into 2 subgroups by the presence or absence of AF/AFL. Cardiac composite outcome and mortality were assessed. Kaplan-Meier curves were constructed to assess the bivariate association between exposure and these 2 study outcomes. Cox proportional models were used to estimate the hazard ratios and 95% CIs associated with the cardiac composite outcome and mortality.

Results

Of 35,539 patients included in the study, 19,961 were female (56.2%), the mean (SD) age was 62.9 (18.0) years, and 5291 patients (14.9%) had AF/AFL. The cardiac composite outcome and mortality incidence rates per 100 person-years in the AF/AFL vs non-AF/AFL subgroups were 8.18 vs 4.90, and 4.09 vs 2.13, respectively (P < .001). There were 3130 (8.8%) deaths. After adjusting for confounding variables, the AF/AFL subgroup maintained a 12% and 16% higher association with the composite outcome and mortality, respectively.

Conclusions

Patients with WPW syndrome and AF/AFL have a higher association with adverse cardiac outcomes and death. Consideration for more aggressive electrophysiology screening and ablation strategies may be warranted in this population.

Human Atrial Cardiac Microtissues for Chamber-Specific Arrhythmic Risk Assessment

Introduction

Although atrial fibrillation is the most prevalent disorder of electrical conduction, the mechanisms behind atrial arrhythmias remain elusive. To address this challenge, we developed a robust in vitro model of 3D atrial microtissue from human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and evaluated chamber-specific chemical responses experimentally and computationally.

Methods

We differentiated atrial and ventricular cardiomyocytes (aCMs/vCMs) from GCaMP6f-expressing hiPSCs and assessed spontaneous AP activity using fluorescence imaging. Self-assembling 3D microtissues were formed with lactate purified CMs and 5% human cardiac fibroblasts and electrically stimulated for one week before high resolution action potential (AP) optical mapping. AP responses to the atrial-specific potassium repolarizing current I _Kur-blocker 4-Aminopyridine (4-AP) and funny current I _f-blocker Ivabradine were characterized within their therapeutic window. Finally, we expanded upon a published hiPSC-CM computational model by incorporating the atrial-specific I _Kur current, modifying ion channel conductances to match the AP waveforms of our microtissues, and employing the updated model to reinforce our experimental findings.

Results

High purity CMs (> 75% cTnT⁺) demonstrated subtype specification by MLC2v expression. Spontaneous beating rates significantly decreased following 3D microtissue formation, with atrial microtissues characterized by their faster spontaneous beating rate, slower AP rise time, and shorter AP duration (APD) compared to ventricular microtissues. We measured atrial-specific responses, including dose-dependent APD prolongation with 4-AP treatment and dose-dependent reduction in spontaneous activity post-Ivabradine treatment.

Conclusion

The presented in vitro platform for screening atrial-specific responses is both robust and sensitive, with high throughput, enabling studies focused at elucidating the mechanisms underlying atrial arrhythmias.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-021-00703-x.

Wolff-Parkinson-White syndrome: De novo variants and evidence for mutational burden in genes associated with atrial fibrillation

BACKGROUND

Wolff-Parkinson-White (WPW) syndrome is a relatively common arrhythmia affecting ~1-3/1,000 individuals. Mutations in PRKAG2 have been described in rare patients in association with cardiomyopathy. However, the genetic basis of WPW in individuals with a structurally normal heart remains poorly understood. Sudden death due to atrial fibrillation (AF) can also occur in these individuals. Several studies have indicated that despite ablation of an accessory pathway, the risk of AF remains high in patients compared to general population.

METHODS

We applied exome sequencing in 305 subjects, including 65 trios, 80 singletons, and 6 multiple affected families. We used de novo analysis, candidate gene approach, and burden testing to explore the genetic contributions to WPW.

RESULTS

A heterozygous deleterious variant in PRKAG2 was identified in one subject, accounting for 0.6% (1/151) of the genetic basis of WPW in this study. Another individual with WPW and left ventricular hypertrophy carried a known pathogenic variant in MYH7. We found rare de novo variants in genes associated with arrhythmia and cardiomyopathy (ANK2, NEBL, PITX2, and PRDM16) in this cohort. There was an increased burden of rare deleterious variants (MAF ≤ 0.005) with CADD score ≥ 25 in genes linked to AF in cases compared to controls (P = .0023).

CONCLUSIONS

Our findings show an increased burden of rare deleterious variants in genes linked to AF in WPW syndrome, suggesting that genetic factors that determine the development of accessory pathways may be linked to an increased susceptibility of atrial muscle to AF in a subset of patients.

High prevalence of hyperlipidaemia in patients with AV re-entry tachycardia and AV nodal re-entry tachycardia

Diet rich in lipids and hyperlipidaemia increases incidence of atrial premature beats and all supraventricular arrhythmias. The aim of the study was to investigate the prevalence of hyperlipidaemia in patients with AV re-entry tachycardia (AVRT) and AV nodal re-entry tachycardia (AVNRT). We conducted a retrospective, cross-sectional, case-control study that included all consecutive patients for whom AVRT or AVNRT was confirmed during electrophysiology study. Age and gender-matched patients admitted to hospital or outpatient clinic for various reasons were randomly included and served as a control group. Hyperlipidaemia was defined according to 2016 European Society of Cardiology guidelines. A total of 1448 subjects were included: 725 patients with AVRT/AVNRT and 723 controls. AVRT/AVNRT patients had high hyperlipidaemia prevalence, which was significantly higher when compared to the control group (50.1 vs. 35.8%, p < 0.001). AVRT patients, with median age of 37.5 years, had hyperlipidaemia prevalence of 45.7%. In a multivariate analysis, hyperlipidaemia was independently associated with AVRT/AVNRT (OR 2.128, p < 0.001), both with AVNRT (OR 1.878, p < 0.001) and AVRT (OR 2.786, p < 0.001). Hypercholesterolemia was significantly more prevalent in patients with AVNRT and AVRT, while this was not the case for hypertriglyceridemia. There were no differences between the AVRT and AVNRT patients regarding hyperlipidaemia prevalence (51.9 vs. 45.7%, p = 0.801), even though AVRT patients were significantly younger (37.5 vs. 48.5, p < 0.001). In conclusion, this is the first study that investigated hyperlipidaemia prevalence in patients with AVRT or AVNRT. AVRT/AVNRT patients had higher prevalence of hyperlipidaemia and higher total and LDL cholesterol levels.