Dataset Information

Modulated Calcium Homeostasis and Release Events Under Atrial Fibrillation and Its Risk Factors: A Meta-Analysis.

ABSTRACT: Background: Atrial fibrillation (AF) is associated with calcium (Ca²⁺) handling remodeling and increased spontaneous calcium release events (SCaEs). Nevertheless, its exact mechanism remains unclear, resulting in suboptimal primary and secondary preventative strategies. Methods: We searched the PubMed database for studies that investigated the relationship between SCaEs and AF and/or its risk factors. Meta-analysis was used to examine the Ca²⁺ mechanisms involved in the primary and secondary AF preventative groups. Results: We included a total of 74 studies, out of the identified 446 publications from inception (1982) until March 31, 2020. Forty-five were primary and 29 were secondary prevention studies for AF. The main Ca²⁺ release events, calcium transient (standardized mean difference (SMD) = 0.49; I ² = 35%; confidence interval (CI) = 0.33-0.66; p < 0.0001), and spark amplitude (SMD = 0.48; I ² = 0%; CI = -0.98-1.93; p = 0.054) were enhanced in the primary diseased group, while calcium transient frequency was increased in the secondary group. Calcium spark frequency was elevated in both the primary diseased and secondary AF groups. One of the key cardiac currents, the L-type calcium current (I_CaL) was significantly downregulated in primary diseased (SMD = -1.07; I ² = 88%; CI = -1.94 to -0.20; p < 0.0001) and secondary AF groups (SMD = -1.28; I ² = 91%; CI = -2.04 to -0.52; p < 0.0001). Furthermore, the sodium-calcium exchanger (I_NCX) and NCX1 protein expression were significantly enhanced in the primary diseased group, while only NCX1 protein expression was shown to increase in the secondary AF studies. The phosphorylation of the ryanodine receptor at S2808 (pRyR-S2808) was significantly elevated in both the primary and secondary groups. It was increased in the primary diseased and proarrhythmic subgroups (SMD = 0.95; I ² = 64%; CI = 0.12-1.79; p = 0.074) and secondary AF group (SMD = 0.66; I ² = 63%; CI = 0.01-1.31; p < 0.0001). Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) expression was elevated in the primary diseased and proarrhythmic drug subgroups but substantially reduced in the secondary paroxysmal AF subgroup. Conclusions: Our study identified that I_CaL is reduced in both the primary and secondary diseased groups. Furthermore, pRyR-S2808 and NCX1 protein expression are enhanced. The remodeling leads to elevated Ca²⁺ functional activities, such as increased frequencies or amplitude of Ca²⁺ spark and Ca²⁺ transient. The main difference identified between the primary and secondary diseased groups is SERCA expression, which is elevated in the primary diseased group and substantially reduced in the secondary paroxysmal AF subgroup. We believe our study will add new evidence to AF mechanisms and treatment targets.

SUBMITTER: Fong SPT

PROVIDER: S-EPMC8329373 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Atrial fibrillation (AF) is the most common cardiac arrhythmia, but our knowledge of the arrhythmogenic substrate is incomplete. Alternans, the beat-to-beat alternation in the shape of cardiac electrical signals, typically occurs at fast heart rates and leads to arrhythmia. However, atrial alternans have been observed at slower pacing rates in AF patients than in controls, suggesting that increased vulnerability to arrhythmia in AF patients may be due to the proarrythmic influence of alternans at these slower rates. As such, alternans may present a useful therapeutic target for the treatment and prevention of AF, but the mechanism underlying alternans occurrence in AF patients at heart rates near rest is unknown. The goal of this study was to determine how cellular changes that occur in human AF affect the appearance of alternans at heart rates near rest. To achieve this, we developed a computational model of human atrial tissue incorporating electrophysiological remodeling associated with chronic AF (cAF) and performed parameter sensitivity analysis of ionic model parameters to determine which cellular changes led to alternans. Of the 20 parameters tested, only decreasing the ryanodine receptor (RyR) inactivation rate constant (kiCa) produced action potential duration (APD) alternans seen clinically at slower pacing rates. Using single-cell clamps of voltage, fluxes, and state variables, we determined that alternans onset was Ca2+-driven rather than voltage-driven and occurred as a result of decreased RyR inactivation which led to increased steepness of the sarcoplasmic reticulum (SR) Ca2+ release slope. Iterated map analysis revealed that because SR Ca2+ uptake efficiency was much higher in control atrial cells than in cAF cells, drastic reductions in kiCa were required to produce alternans at comparable pacing rates in control atrial cells. These findings suggest that RyR kinetics may play a critical role in altered Ca2+ homeostasis which drives proarrhythmic APD alternans in patients with AF.

Project description:BackgroundThe mechanisms underlying spontaneous atrial fibrillation (AF) associated with atrial ischemia/infarction are incompletely elucidated. Here, we investigate the mechanisms underlying spontaneous AF in an ovine model of left atrial myocardial infarction (LAMI).Methods and resultsLAMI was created by ligating the atrial branch of the left anterior descending coronary artery. ECG loop recorders were implanted to monitor AF episodes. In 7 sheep, dantrolene-a ryanodine receptor blocker-was administered in vivo during the 8-day observation period (LAMI-D, 2.5 mg/kg, IV, BID). LAMI animals experienced numerous spontaneous AF episodes during the 8-day monitoring period that were suppressed by dantrolene (LAMI, 26.1±5.1; sham, 4.3±1.1; LAMI-D, 2.8±0.8; mean±SEM episodes per sheep, P<0.01). Optical mapping showed spontaneous focal discharges (SFDs) originating from the ischemic/normal-zone border. SFDs were calcium driven, rate dependent, and enhanced by isoproterenol (0.03 µmol/L, from 210±87 to 3816±1450, SFDs per sheep) but suppressed by dantrolene (to 55.8±32.8, SFDs per sheep, mean±SEM). SFDs initiated AF-maintaining reentrant rotors anchored by marked conduction delays at the ischemic/normal-zone border. NOS1 (NO synthase-1) protein expression decreased in ischemic zone myocytes, whereas NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) oxidase and xanthine oxidase enzyme activities and reactive oxygen species (DCF [6-carboxy-2',7'-dichlorodihydrofluorescein diacetate]-fluorescence) increased. CaM (calmodulin) aberrantly increased [3H]ryanodine binding to cardiac RyR2 (ryanodine receptors) in the ischemic zone. Dantrolene restored the physiological binding of CaM to RyR2.ConclusionsAtrial ischemia causes spontaneous AF episodes in sheep, caused by SFDs that initiate reentry. Nitroso-redox imbalance in the ischemic zone is associated with intense reactive oxygen species production and altered RyR2 responses to CaM. Dantrolene administration normalizes the CaM response, prevents LAMI-related SFDs, and AF initiation. These findings provide novel insights into the mechanisms underlying ischemia-related atrial arrhythmias.

Project description:ObjectivesWe identified factors associated with thromboembolic and bleeding events in two contemporary cohorts of anticoagulated patients with atrial fibrillation (AF), treated with either vitamin K antagonists (VKA) or non-VKA oral anticoagulants (NOACs).DesignProspective, multicentre observational study.Setting461 centres in seven European countries.Participants5310 patients receiving a VKA (PREvention oF thromboembolic events - European Registry in Atrial Fibrillation (PREFER in AF), derivation cohort) and 3156 patients receiving a NOAC (PREFER in AF Prolongation, validation cohort) for stroke prevention in AF.Outcome measuresRisk factors for thromboembolic events (ischaemic stroke, systemic embolism) and major bleeding (gastrointestinal bleeding, intracerebral haemorrhage and other life-threatening bleeding).ResultsThe mean age of patients enrolled in the PREFER in AF registry was 72±10 years, 40% were female and the mean CHA2DS2-VASc Score was 3.5±1.7. The incidence of thromboembolic and major bleeding events was 2.34% (95% CI 1.93% to 2.74%) and 2.84% (95% CI 2.41% to 3.33%) after 1-year of follow-up, respectively.Abnormal liver function, prior stroke or transient ischaemic attack, labile international normalised ratio (INR), concomitant therapy with antiplatelet or non-steroidal anti-inflammatory drugs, heart failure and older age (≥75 years) were independently associated with both thromboembolic and major bleeding events.With the exception of unstable INR values, these risk factors were validated in patients treated with NOACs (PREFER in AF Prolongation Study, 72±9 years, 40% female, CHA2DS2-VASc 3.3±1.6). For each single point decrease on a modifiable bleeding risk scale we observed a 30% lower risk for major bleeding events (OR 0.70, 95% CI 0.64 to 0.76, p<0.01) and a 28% lower rate of thromboembolic events (OR 0.72, 95% CI 0.66 to 0.82, p<0.01).ConclusionAttending to modifiable risk factors is an important treatment target in anticoagulated AF patients to reduce thromboembolic and bleeding events. Initiation of anticoagulation in those at risk of stroke should not be prevented by elevated bleeding risk scores.

Dataset Information

Modulated Calcium Homeostasis and Release Events Under Atrial Fibrillation and Its Risk Factors: A Meta-Analysis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets