Atrial fibrillation in the elderly: the potential contribution of reactive oxygen species

A Study of R-R Interval Transition Matrix Features for Machine Learning Algorithms in AFib Detection

Atrial Fibrillation (AFib) is a heart condition that occurs when electrophysiological malformations within heart tissues cause the atria to lose coordination with the ventricles, resulting in "irregularly irregular" heartbeats. Because symptoms are subtle and unpredictable, AFib diagnosis is often difficult or delayed. One possible solution is to build a system which predicts AFib based on the variability of R-R intervals (the distances between two R-peaks). This research aims to incorporate the transition matrix as a novel measure of R-R variability, while combining three segmentation schemes and two feature importance measures to systematically analyze the significance of individual features. The MIT-BIH dataset was first divided into three segmentation schemes, consisting of 5-s, 10-s, and 25-s subsets. In total, 21 various features, including the transition matrix features, were extracted from these subsets and used for the training of 11 machine learning classifiers. Next, permutation importance and tree-based feature importance calculations determined the most predictive features for each model. In summary, with Leave-One-Person-Out Cross Validation, classifiers under the 25-s segmentation scheme produced the best accuracies; specifically, Gradient Boosting (96.08%), Light Gradient Boosting (96.11%), and Extreme Gradient Boosting (96.30%). Among eleven classifiers, the three gradient boosting models and Random Forest exhibited the highest overall performance across all segmentation schemes. Moreover, the permutation and tree-based importance results demonstrated that the transition matrix features were most significant with longer subset lengths.

Relationship Between Radiation Exposure and Incident Atrial Fibrillation Among Atomic Bomb Survivors

Background: Atrial fibrillation (AF) is a common arrhythmia. Although radiation exposure is associated with an elevated risk of cardiovascular disease, the effects of radiation on arrhythmia, especially AF, are unclear. We evaluated the relationship between radiation and AF in a cohort of atomic bomb survivors. Methods and Results: From a baseline enrollment period (1967-1969) to 2009, 7,379 Hiroshima and Nagasaki atomic bomb survivors (mean baseline age 50.6 years, 65.8% women, 72.9% from Hiroshima) without AF and who had been exposed to estimated radiation doses between 0 and 3.614 Gy were followed-up once every 2 years. AF was identified by 12-lead electrocardiograms and medical records. Treating age as the time scale, AF incidence was modeled with Cox proportional hazards models adjusting for demographics, AF risk factors, and radiation. We modeled radiation as both a continuous variable and categorized according to radiation dose (Control [<0.005 Gy] and 5 equal-sized groups based on radiation dose quintiles in the cohort). Over 4 decades of follow-up, we identified 276 AF cases in 176,687 person-years, for an incidence rate of 1.56 per 1,000 person-years. After adjusting for sex and city, neither categorized, linear, nor linear-quadratic models showed substantive evidence of radiation effects. Similar results were obtained after adjusting for AF risk factors. Conclusions: There were no clear positive associations between radiation dose and AF risk, rather null or non-significant inverse associations.

Melatonin to Rescue the Aged Heart: Antiarrhythmic and Antioxidant Benefits

Aging comes with gradual loss of functions that increase the vulnerability to disease, senescence, and death. The mechanisms underlying these processes are linked to a prolonged imbalance between damage and repair. Damaging mechanisms include oxidative stress, mitochondrial dysfunction, chronodisruption, inflammation, and telomere attrition, as well as genetic and epigenetic alterations. Several endogenous tissue repairing mechanisms also decrease. These alterations associated with aging affect the entire organism. The most devastating manifestations involve the cardiovascular system and may lead to lethal cardiac arrhythmias. Together with structural remodeling, electrophysiological and intercellular communication alterations during aging predispose to arrhythmic events. Despite the knowledge on repairing mechanisms in the cardiovascular system, effective antiaging strategies able to reduce the risk of arrhythmias are still missing. Melatonin is a promising therapeutic candidate due to its pleiotropic actions. This indoleamine regulates chronobiology and endocrine physiology. Of relevance, melatonin is an antiaging, antioxidant, antiapoptotic, antiarrhythmic, immunomodulatory, and antiproliferative molecule. This review focuses on the protective effects of melatonin on age-induced cardiac functional and structural alterations, potentially becoming a new fountain of youth for the heart.

Atrial fibrillation: risk factors and comorbidities in a tertiary center in Jeddah, Saudi Arabia

Introduction

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia worldwide and carries significant risk of morbidity and mortality. The prevalence of AF is high in significant parts of the world, but not much is known from countries, such as Saudi Arabia.

Aims

To study the risk factors, etiologies, comorbidities, and outcome of AF in Saudi Arabia.

Patients and methods

A retrospective study was conducted in King Abdul-Aziz Hospital in Jeddah during the period 2010–2017. Data were collected from both the electronic-and paper-based medical records of patients with AF. The data included the demographic information, adverse lifestyle (smoking and obesity), cardiothoracic surgery, and comorbidities.

Results

A total of 167 patients were included in the analysis (43% were males). The mean age was 63.3±35 years and the mean body mass index was 28.8±83. Hypertension (HTN) was the most prevalent risk factor encountered (73.1%). This was followed by valvular heart disease, and type 2 diabetes mellitus (T2DM), which occurred in 58.7% and 53.3% of patients, respectively. Valvular heart disease was significantly associated with older age (P=0.002) and coronary artery disease (CAD) (P=0.001). Heart failure (HF) was associated with HTN (P=0.005), coronary heart disease (P=0.001), and chronic kidney disease (CKD) (P=0.003).

Conclusion

AF was more prevalent among females in Saudi Arabia. HTN, valvular heart disease, and T2DM were the most prevalent risk factors of AF in Saudi Arabia. Valvular heart disease was more prevalent among older patients and significantly associated with CAD. HTN, CAD, and CKD were the most significant risk factors for HF in patients with AF.

Enhanced basal late sodium current appears to underlie the age-related prolongation of action potential duration in guinea pig ventricular myocytes

Aging hearts have prolonged QT interval and are vulnerable to oxidative stress. Because the QT interval indirectly reflects the action potential duration (APD), we examined the hypotheses that 1) the APD of ventricular myocytes increases with age; 2) the age-related prolongation of APD is due to an enhancement of basal late Na⁺ current (I_NaL); 3) inhibition of I_NaL may protect aging hearts from arrhythmogenic effects of hydrogen peroxide (H₂O₂). Experiments were performed on ventricular myocytes isolated from one-month (young) and one-year (old) guinea pigs (GPs). The APD of myocytes from old GPs was significantly longer than that from young GPs and was shortened by the I_NaL inhibitors GS967 and tetrodotoxin. The magnitude of I_NaL was significantly larger in myocytes from old than from young GPs. The CaMKII inhibitors KN-93 and AIP and the Na_V1.5-channel blocker MTSEA blocked the I_NaL. There were no significant differences between myocytes from young and old GPs in L-type Ca²⁺ current and the rapidly- and slowly-activating delayed rectifier K⁺ currents, although the inward rectifier K⁺ current was slightly decreased in myocytes from old GPs. H₂O₂ induced more early afterdepolarizations in myocytes from old than from young GPs. The effect of H₂O₂ was attenuated by GS967. The results suggest that 1) the APD of myocytes from old GPs is prolonged, 2) a CaMKII-mediated increase in Na_V1.5-channel I_NaL is responsible for the prolongation of APD, and 3) Inhibition of I_NaL may be beneficial for maintaining electrical stability under oxidative stress in myocytes of old GPs.

Red Wine, Resveratrol and Atrial Fibrillation

Atrial fibrillation (AF) is a common cardiac arrhythmia that is associated with increased risk for cardiovascular disease and overall mortality. Excessive alcohol intake is a well-known risk factor for AF, but this correlation is less clear with light and moderate drinking. Besides, low doses of red wine may acutely prolong repolarization and slow cardiac conduction. Resveratrol, a bioactive polyphenol found in grapes and red wine, has been linked to antiarrhythmic properties and may act as an inhibitor of both intracellular calcium release and pathological signaling cascades in AF, eliminating calcium overload and preserving the cardiomyocyte contractile function. However, there are still no clinical trials at all that prove that resveratrol supplementation leads to improved outcomes. Besides, no observational study supports a beneficial effect of light or moderate alcohol intake and a lower risk of AF. The purpose of this review is to briefly describe possible beneficial effects of red wine and resveratrol in AF, and also present studies conducted in humans regarding chronic red wine consumption, resveratrol, and AF.

Circulating ceruloplasmin, ceruloplasmin-associated genes, and the incidence of atrial fibrillation in the atherosclerosis risk in communities study

BACKGROUND

Ceruloplasmin (CP) may promote structural changes in the atrium making it more arrhythmogenic. We assessed the associations between CP, CP-associated genetic variants, and incident atrial fibrillation (AF) in the Atherosclerosis Risk in Communities (ARIC) study.

METHODS AND RESULTS

We studied 10,059 men and women without prevalent AF aged 53 to 75years in 1996-1998 and followed through 2012. Circulating CP was measured in stored blood samples obtained in 1996-1998. Polymorphisms rs11708215 and rs13072552, previously associated with CP concentrations, were measured in 10,059 and 8829 participants respectively. AF was ascertained from study electrocardiograms, hospital discharge codes, and death certificates. Multivariable Cox models were run to study the association between circulating CP, CP-associated polymorphisms, and the incidence of AF. Over 10.5years of mean follow-up, 1357 cases of AF were identified. After adjusting for traditional risk factors and biomarkers, higher levels of circulating CP were associated with incident AF (hazard ratio [HR] 1.33, 95% confidence interval [CI] 1.11, 1.61 comparing top to bottom quartiles). Both rs11708215 and rs13072552 were significantly associated with CP levels. Presence of the CP-increasing alleles in rs11708215 and rs13072552, however, were significantly associated with lower risk of AF in whites (HR 0.84, 95%CI 0.76, 0.94, p=0.002 and HR 0.83; 95%CI 0.69, 0.99, p=0.043 respectively per CP-increasing allele in the final adjusted model) but not in African Americans.

CONCLUSIONS

Even though higher CP concentrations were associated with increased AF risk, genetic variants associated with higher CP decreased the risk of AF in whites. Our results suggest that circulating CP levels may not be causally related to risk of incident AF.

Mitochondrial DNA 4977bp deletion mutation in peripheral blood reflects atrial remodeling in patients with non-valvular atrial fibrillation

PURPOSE

Recently, mitochondrial DNA 4977bp deletion (mtDNA4977-mut), a somatic mutation related to oxidative stress, has been shown to be associated with atrial fibrillation (AF). We hypothesized that patient age, as well as electroanatomical characteristics of fibrillating left atrial (LA), vary depending on the presence of mtDNA4977-mut in peripheral blood among patients with non-valvular AF.

MATERIALS AND METHODS

Analyzing clinical and electroanatomical characteristics, we investigated the presence of the mtDNA4977-mut in peripheral blood of 212 patients (51.1±13.2 years old, 83.5% male) undergoing catheter ablation for non-valvular AF, as well as 212 age-matched control subjects.

RESULTS

The overall frequency of peripheral blood mtDNA4977-mut in patients with AF and controls was not significantly different (24.5% vs. 19.3%, p=0.197). When the AF patient group was stratified according to age, mtDNA4977-mut was more common (47.4% vs. 20.0%, p=0.019) in AF patients older than 65 years than their age-matched controls. Among AF patients, those with mtDNA4977-mut were older (58.1±11.9 years old vs. 48.8±11.9 years old, p<0.001). AF patients positive for the mtDNA mutation had greater LA dimension (p=0.014), higher mitral inflow peak velocity (E)/diastolic mitral annular velocity (Em) ratio (p<0.001), as well as lower endocardial voltage (p=0.035), and slower conduction velocity (p=0.048) in the posterior LA than those without the mutation. In multivariate analysis, E/Em ratio was found to be significantly associated with the presence of mtDNA4977-mut in peripheral blood.

CONCLUSION

mtDNA4977-mut, an age-related somatic mutation detected in the peripheral blood, is associated with advanced age and electro-anatomical remodeling of the atrium in non-valvular AF.