Results from a nationwide atrial fibrillation screening effort in Belgium

Introduction

Atrial Fibrillation (AF) is associated with an increased risk of stroke that can be mitigated with anticoagulation therapy. Opportunistic screening for AF for primary stroke prevention is recommended in subjects above 65. However, the paroxysmal and asymptomatic nature of AF hampers early detection with a single time point screening. Multiple time point measurements are superior to single time point measurements for the detection of AF. New technologies such as photoplethysmography (PPG) enable large scale AF screening with repetitive measurements at low-cost using only a smartphone.

Purpose

To explore an entirely online AF screening program in subjects with an elevated stroke risk.

Methods

The Belgian Heart Rhythm Association launched a digital marketing campaign, to promote AF screening during “The Belgian Week of the Heart Rhythm”. Candidates were referred to an online questionnaire to calculate their CHADS-VASC score. Subjects older than 18 with a CHADS-VASC score of 2 or more were allowed to enter the screening program. AF screening was performed with a PPG-based smartphone application. A 60-second PPG trace is captured by placing a fingertip on the smartphone's camera. The smartphone application analyses the PPG trace with an artificial intelligence software. Subjects were instructed to perform measurement twice daily and while experiencing symptoms over the course of 7 days. Measurements were classified as AF or non-AF by the algorithm and were reviewed by medical technicians.

Results

Of the 12.602 candidates who completed the questionnaire, 6.020 subjects met the inclusion criteria and were offered screening. However, only 2.111 (35%) participated in the screening program. The mean age of participants was 63±11 years, 37.3% was male, median CHADS-VASC was 2 (2–3). 257 participants (12.2%) were previously known with AF. In total 25.362 PPG recordings of 60 seconds were performed of which 258 demonstrated AF. AF was detected in 56 participants (2.7%). This was a new finding in 36 participants (1.7%) meaning that 64.3% of participants demonstrating AF were not previously known with AF. The number needed to screen was 58.6 to detect AF in a population without a history of AF and the number needed to invite was 167.2. Only 20 participants (7.8%) with a history of AF demonstrated AF during the screening program.

Conclusions

AF screening in subjects with an elevated stroke risk is feasible with an entirely online screening program without the need for medical hardware or medical personnel with an acceptable number needed to screen. However, this approach failed to target subjects in the highest age groups and since almost two thirds of the subjects interested in the screening program failed to commence screening, approaches to increase this response (specifically in high-risk groups) needs to be explored.

Funding Acknowledgement

Type of funding sources: None.

Predictors of successful cardioversion of recent-onset atrial fibrillation to sinus rhythm with orally inhaled flecainide

Background

Height, weight, and body mass index (BMI) are well established risk factors for atrial fibrillation (AF) but whether they are also predictors of successful pharmacological cardioversion of AF is unknown. Data from the open-label INSTANT study of flecainide acetate oral inhalation solution (FlecIH) for acute cardioversion of recent-onset symptomatic AF were examined to determine if these anthropometric measures are predictors of successful cardioversion of AF to sinus rhythm (SR) with FlecIH.

Methods

Logistic regression was performed on a broad array of patient and disease characteristics to identify predictors of cardioversion success at 90 minutes post-dose, and potential interactions were examined by boundary restriction analysis. Data are presented for patients receiving 120 mg FlecIH.

Results

Data from 81 patients (32.1% female) with a mean age of 59.8 years (range: 26.0, 84.0) were included in the analysis. This cohort had a mean weight of 87 kg (range: 57, 150), a mean height of 180 cm (range: 156, 199), and a mean BMI of 26.8 kg/m2 (range: 17.2, 37.9). A logistic regression model identified height, weight, and BMI as significant predictors of cardioversion success (p<0.01) and a boundary restriction analysis revealed a negative correlation between BMI and conversion rate across the entire dataset (see Figure 1). Clinically significant conversion rates were observed for patients with BMI values that were considered normal (BMI <25 kg/m2 = 53%; 95% CI: 36, 70), overweight (BMI ≥25 and <30 kg/m2 = 47%; 95% CI: 29, 64), and obese (BMI ≥30 and <35 kg/m2 = 43%; 95% CI: 17, 69); however, none of the severely obese patients (BMI ≥35 mg/m2) had their AF successfully converted to sinus rhythm (see Figure 2).

Conclusions

Successful cardioversion of recent onset AF with 120 mg FlecIH was observed in normal, overweight, and obese patients with BMI values <35 kg/m2; however, conversion rate decreases with increasing BMI. Further evaluation of FlecIH dosing in severely obese patients is warranted.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): InCarda Therapeutics

Reduced Penetrance and Variable Expression of SCN5A Mutations and the Importance of Co-inherited Genetic Variants: Case Report and Review of the Literature

Mutations in the SCN5A gene are responsible for multiple phenotypical presentations including Brugada syndrome, long QT syndrome, progressive familial heart block, sick sinus syndrome, dilated cardiomyopathy, lone atrial fibrillation and multiple overlap syndromes. These different phenotypic expressions of a mutation in a single gene can be explained by variable expression and reduced penetrance. One of the possible explanations of these phenomena is the co-inheritance of genetic variants. We describe a family where the individuals exhibit a compound heterozygosity in the SCN5A gene including a mutation (R1632H) and a new variant (M858L). Individuals with both the mutation and new variant present with a more severe phenotype including spontaneous atrial tachyarrhythmia at young age. We give an overview of the different phenotypes of "SCN5A disease" and discuss the importance of co-inherited genetic variants in the expression of SCN5A disease.

Lower than expected desmosomal gene mutation prevalence in endurance athletes with complex ventricular arrhythmias of right ventricular origin

OBJECTIVE

To determine the prevalence of desmosomal gene mutations in athletes with complex arrhythmias (VA) of right ventricular (RV) origin and structural RV abnormalities to evaluate whether there is sufficient genetic overlap with arrhythmogenic right ventricular cardiomyopathy (ARVC) to consider them the same or different entities.

DESIGN

Observational cohort

SETTING

Tertiary hospital referrals

PATIENTS

Forty-seven consecutive athletes (age 42 (11) years) with complex VA of RV morphology (excluding idiopathic right ventricular outflow tract ventricular tachycardia), who performed 14 (9) h/week of moderate to intense sport practise for 19 (9) years.

INTERVENTIONS

Clinical evaluation (detailed sports history, multi-modality imaging, electrophysiological study) and sequencing of five candidate desmosomal genes.

RESULTS

A clinical diagnosis of definite or suspected ARVC by task force criteria (TFC) was met in 24 (51%) and 17 (36%), respectively. ARVC classification was not related to the rate of major arrhythmic events (p=0.28). Pathogenic mutations (four novel) were identified in six athletes (12.8%), which is below published rates for familial ARVC (27-52%). Moreover, only two athletes had a suggestive family history. Severe RV dysfunction was more frequent in mutation carriers (33% vs 2%, p=0.04), but otherwise TFC features were similar to those without mutations. No mutations were found in the 20 athletes performing more than average weekly exercise, yet all met the criteria for definite or suspected ARVC.

CONCLUSIONS

In this athletic cohort, we found lower than expected rates of desmosomal gene mutations, particularly among those performing the most exercise. This adds further weight to the hypothesis that an ARVC-like phenotype may be acquired through intense exercise without an identifiable genetic predisposition.

Abrupt rate accelerations or premature beats cause life-threatening arrhythmias in mice with long-QT3 syndrome

Deletion of amino-acid residues 1505-1507 (KPQ) in the cardiac SCN5A Na(+) channel causes autosomal dominant prolongation of the electrocardiographic QT interval (long-QT syndrome type 3 or LQT3). Excessive prolongation of the action potential at low heart rates predisposes individuals with LQT3 to fatal arrhythmias, typically at rest or during sleep. Here we report that mice heterozygous for a knock-in KPQ-deletion (SCN5A(Delta/+)) show the essential LQT3 features and spontaneously develop life-threatening polymorphous ventricular arrhythmias. Unexpectedly, sudden accelerations in heart rate or premature beats caused lengthening of the action potential with early afterdepolarization and triggered arrhythmias in Scn5a(Delta/+) mice. Adrenergic agonists normalized the response to rate acceleration in vitro and suppressed arrhythmias upon premature stimulation in vivo. These results show the possible risk of sudden heart-rate accelerations. The Scn5a(Delta/+) mouse with its predisposition for pacing-induced arrhythmia might be useful for the development of new treatments for the LQT3 syndrome.

Deletion of the hypoxia-response element in the vascular endothelial growth factor promoter causes motor neuron degeneration

Hypoxia stimulates angiogenesis through the binding of hypoxia-inducible factors to the hypoxia-response element in the vascular endothelial growth factor (Vegf) promotor. Here, we report that deletion of the hypoxia-response element in the Vegf promotor reduced hypoxic Vegf expression in the spinal cord and caused adult-onset progressive motor neuron degeneration, reminiscent of amyotrophic lateral sclerosis. The neurodegeneration seemed to be due to reduced neural vascular perfusion. In addition, Vegf165 promoted survival of motor neurons during hypoxia through binding to Vegf receptor 2 and neuropilin 1. Acute ischemia is known to cause nonselective neuronal death. Our results indicate that chronic vascular insufficiency and, possibly, insufficient Vegf-dependent neuroprotection lead to the select degeneration of motor neurons.

Inhibition of plasminogen activators or matrix metalloproteinases prevents cardiac rupture but impairs therapeutic angiogenesis and causes cardiac failure

Cardiac rupture is a fatal complication of acute myocardial infarction lacking treatment. Here, acute myocardial infarction resulted in rupture in wild-type mice and in mice lacking tissue-type plasminogen activator, urokinase receptor, matrix metalloproteinase stromelysin-1 or metalloelastase. Instead, deficiency of urokinase-type plasminogen activator (u-PA-/-) completely protected against rupture, whereas lack of gelatinase-B partially protected against rupture. However, u-PA-/- mice showed impaired scar formation and infarct revascularization, even after treatment with vascular endothelial growth factor, and died of cardiac failure due to depressed contractility, arrhythmias and ischemia. Temporary administration of PA inhibitor-1 or the matrix metalloproteinase-inhibitor TIMP-1 completely protected wild-type mice against rupture but did not abort infarct healing, thus constituting a new approach to prevent cardiac rupture after acute myocardial infarction.

Targeted deficiency or cytosolic truncation of the VE-cadherin gene in mice impairs VEGF-mediated endothelial survival and angiogenesis

Vascular endothelial cadherin, VE-cadherin, mediates adhesion between endothelial cells and may affect vascular morphogenesis via intracellular signaling, but the nature of these signals remains unknown. Here, targeted inactivation (VEC-/-) or truncation of the beta-catenin-binding cytosolic domain (VECdeltaC/deltaC) of the VE-cadherin gene was found not to affect assembly of endothelial cells in vascular plexi, but to impair their subsequent remodeling and maturation, causing lethality at 9.5 days of gestation. Deficiency or truncation of VE-cadherin induced endothelial apoptosis and abolished transmission of the endothelial survival signal by VEGF-A to Akt kinase and Bcl2 via reduced complex formation with VEGF receptor-2, beta-catenin, and phosphoinositide 3 (PI3)-kinase. Thus, VE-cadherin/ beta-catenin signaling controls endothelial survival.