Atrial nitroso-redox balance and refractoriness following on-pump cardiac surgery: a randomized trial of atorvastatin

Association Between Serum Levels of Nicotinamide-Adenine Dinucleotide Phosphate Oxidase 2 and the Development of Atrial Fibrillation After Isolated Coronary Artery Bypass Grafting: A Prospective Pilot Study

INTRODUCTION

To investigate the levels of nicotinamide-adenine dinucleotide phosphate oxidase 2 (NOX2) in serum and pericardial drainage samples in the early stage after coronary artery bypass grafting (CABG) and determine whether NOX2 is predictive of postoperative atrial fibrillation (POAF).

MATERIALS AND METHODS

This prospective pilot study involved 152 adults without history of atrial fibrillation who underwent first-time elective isolated CABG. Serum and pericardial fluid samples were simultaneously obtained from patients at baseline and 4, 12, and 24 h post operation. NOX2 levels were determined using enzyme-linked immunosorbent assays. The heart rhythm of patients was continuously monitored through a Holter monitor until discharge. Logistic regression and receiver-operating characteristic (ROC) curve analyses were performed, as appropriate.

RESULTS

Fifty-one patients (33.6%) experienced in-hospital POAF. NOX2 concentration in serum and pericardial drainage samples was increased after surgery, reached its peak at 12 h, and gradually declined thereafter toward the baseline levels by 24 h. At 12 h, patients with POAF had higher levels of serum NOX2 than those without (3.96 ± 0.35 vs. 3.70 ± 0.75 μg/mL, respectively, p = 0.004). There were no discernible differences in pericardial NOX2 between the 2 groups. Multivariate analysis revealed that serum NOX2 at 12 h post operation was the strongest independent predictor of POAF (odds ratio: 2.179, 95% confidence interval: 1.084-4.377). The area under the ROC curve of the POAF predictive model was 0.732 (95% confidence interval: 0.654-0.801).

CONCLUSION

Serum NOX2 may be useful in the identification of POAF. Larger studies are warranted to substantiate these findings.

Validation of a new species for studying postoperative atrial fibrillation: Swine sterile pericarditis model

BACKGROUND

The canine sterile pericarditis model associated with atrial inflammation is an experimental counterpart of postoperative atrial fibrillation (POAF). However, the use of canines for research is restricted by ethics committees in many countries, and social acceptance is declining.

OBJECTIVE

To validate the feasibility of the swine sterile pericarditis model as an experimental counterpart to study POAF.

METHODS

Seven domestic pigs (35-60 kg) underwent initial pericarditis surgery. On two or more postoperative days in the closed-chest state, we performed electrophysiological measurements of pacing threshold and atrial effective refractory period (AERP) while pacing from the right atrial appendage (RAA) and the posterior left atrium (PLA). The inducibility of POAF (>5 min) by burst pacing was determined in both the conscious and anesthetized closed-chest state. These data were compared to previously published canine sterile pericarditis data for validation.

RESULTS

The pacing threshold increased from day 1 to day 3 (2 ± 0.1 to 3.3 ± 0.6 mA in the RAA, 2.5 ± 0.1 to 4.8 ± 0.2 mA in the PLA). Also, the AERP increased from day 1 to day 3 (118 ± 8 to 157 ± 16 ms in the RAA; 98 ± 4 to 124 ± 2 ms in the PLA, both p < .05). Induction of sustained POAF occurred in 43% (POAF CL range 74-124 ms). All electrophysiologic data from the swine model were consistent with the canine model with respect to (1) the range of both pacing threshold and AERP; (2) the progressive increase in threshold and AERP over time; (3) a 40%-50% incidence of POAF.

CONCLUSION

A newly developed swine sterile pericarditis model demonstrated electrophysiologic properties consistent with the canine model and patients after open heart surgery.

Circulating small extracellular vesicle-encapsulated SEMA5A-IT1 attenuates myocardial ischemia-reperfusion injury after cardiac surgery with cardiopulmonary bypass

Cardiomyocyte injury is a common complication during cardiac surgery with cardiopulmonary bypass (CPB). Studies have shown that circulating small extracellular vesicles (sEVs) are involved in the pathological process of cardiovascular diseases via delivering signaling molecules. This study aims to investigate the relationship between circulating sEV-encapsulated long noncoding RNAs (lncRNAs) and cardiac injury after CPB. Here, we found that the expression of sEV SEMA5A-IT1 in serum samples of patients after CPB was higher than that of pre-CPB serum samples. Moreover, serum-derived sEV SEMA5A-IT1 levels were negatively correlated with creatine kinase-MB (CK-MB) levels in patients who underwent CPB operation. Notably, circulating sEVs packaged with SEMA5A-IT1 could be uptaken by cardiomyocyte-like cells AC16 and increased SEMA5A-IT1 expression in AC16 cells. Upregulated SEMA5A-IT1 protected cardiomyocytes against hypoxia/reoxygenation injury, confirmed by increased cell viability, reduced cell apoptosis, and inhibited ferroptosis in AC16 cells. Mechanistically, SEMA5A-IT1 regulated the expression of B-cell CLL/lymphoma 2 (BCL2) and solute carrier family 7 member 11 (SLC7A11) through sponging miR-143-3p. Transfection of miR-143-3p mimics, BCL2, or SLC7A11 knockdown could attenuate the protective effect of SEMA5A-IT1 on cardiomyocytes. In conclusion, we propose that SEMA5A-IT1, which is transported to cardiomyocytes through circulating sEVs, is an important regulatory molecule that protects cardiomyocytes from ischemia–reperfusion injury, providing a target for the prevention and treatment of myocardial ischemia–reperfusion injury.

Antioxidants in Arrhythmia Treatment—Still a Controversy? A Review of Selected Clinical and Laboratory Research

Antioxidants are substances that can prevent damage to cells caused by free radicals. Production of reactive oxygen species and the presence of oxidative stress play an important role in cardiac arrhythmias. Currently used antiarrhythmic drugs have many side effects. The research on animals and humans using antioxidants (such as vitamins C and E, resveratrol and synthetic substances) yields many interesting but inconclusive results. Natural antioxidants, such as vitamins C and E, can reduce the recurrence of atrial fibrillation (AF) after successful electrical cardioversion and protect against AF after cardiac surgery, but do not affect the incidence of atrial arrhythmias in critically ill patients with trauma. Vitamins C and E may also effectively treat ventricular tachycardia, ventricular fibrillation and long QT-related arrhythmias. Another natural antioxidant—resveratrol—may effectively treat AF and ventricular arrhythmias caused by ischaemia–reperfusion injury. It reduces the mortality associated with life-threatening ventricular arrhythmias and can be used to prevent myocardial remodelling. Statins also show antioxidant activity. Their action is related to the reduction of oxidative stress and anti-inflammatory effect. Therefore, statins can reduce the post-operative risk of AF and may be useful in lowering its recurrence rate after successful cardioversion. Promising results also apply to polyphenols, nitric oxide synthase inhibitors and MitoTEMPO. Although few clinical trials have been conducted, the use of antioxidants in treating arrhythmias is an interesting prospect.

Mechanisms Underlying Antiarrhythmic Properties of Cardioprotective Agents Impacting Inflammation and Oxidative Stress

The prevention of cardiac life-threatening ventricular fibrillation and stroke-provoking atrial fibrillation remains a serious global clinical issue, with ongoing need for novel approaches. Numerous experimental and clinical studies suggest that oxidative stress and inflammation are deleterious to cardiovascular health, and can increase heart susceptibility to arrhythmias. It is quite interesting, however, that various cardio-protective compounds with antiarrhythmic properties are potent anti-oxidative and anti-inflammatory agents. These most likely target the pro-arrhythmia primary mechanisms. This review and literature-based analysis presents a realistic view of antiarrhythmic efficacy and the molecular mechanisms of current pharmaceuticals in clinical use. These include the sodium-glucose cotransporter-2 inhibitors used in diabetes treatment, statins in dyslipidemia and naturally protective omega-3 fatty acids. This approach supports the hypothesis that prevention or attenuation of oxidative and inflammatory stress can abolish pro-arrhythmic factors and the development of an arrhythmia substrate. This could prove a powerful tool of reducing cardiac arrhythmia burden.