Effect of Statins on the Incidence of Postoperative Atrial Fibrillation after Cardiac Valve Surgery

Identification of new-onset atrial fibrillation after cardiac surgery in Vietnam. A feasibility study of a novel screening strategy in a limited-resource setting: study protocol

INTRODUCTION

Atrial fibrillation (AF) developing after cardiac surgery is the most common postoperative complication with an incidence up to 50%. The presence of postoperative AF is associated with significant morbidity, mortality and economic burden. However, in Vietnam, data on AF postcardiac surgery are limited, in part due to a shortage of screening equipment. This project aims to identify the incidence, risk factors and postoperative complications of new-onset postoperative AF after cardiac surgery, and the feasibility of introducing a novel screening strategy using the combination of two portable devices to detect AF.

METHODS AND ANALYSIS

This is a feasibility study examining patients who are (1) ≥18 years old; (2) undergoing coronary artery bypass graft and/or valve surgery and (3) in normal sinus rhythm prior to their operation. Patients with congenital heart disease, a prior history of AF or those who require a pacemaker after surgery will be excluded. All patients will be followed up for the duration of their hospitalisation. The screening strategy will include monitoring the continuous ECG tracing in the intensive care unit, and if AF is suspected, a 30 s lead-1 ECG will be recorded using the smartphone-based AliveCor Kardia Mobile. On the postoperative wards, blood pressure will be measured three times daily using a modified blood pressure device (Microlife BP200 Afib): and if AF is suspected a 30 s ECG will be recorded using the AliveCor Kardia Mobile. A 12-lead ECG may be ordered subsequently if clinically indicated. The primary outcome is the incidence of postoperative AF. Secondary outcomes include establishing the risk factors and complications associated with postoperative AF; and the barriers and facilitators of the screening strategy.

ETHICS AND DISSEMINATION

Ethics approval was granted by Scientific Board of Cardiovascular Centre, E Hospital on 28 September, 2017. Study results will be disseminated through local and international conferences and peer-reviewed publications.

Clinical Risk Factors for Postoperative Atrial Fibrillation among Patients after Cardiac Surgery

BACKGROUND

Postoperative atrial fibrillation (POAF) is a common arrhythmia following cardiac surgery and is associated with increased health-care costs, complications, and mortality. The etiology of POAF is incompletely understood and its prediction remains suboptimal. Using data from published studies, we performed a systemic review and meta-analysis to identify preoperative clinical risk factors associated with patients at increased risk of POAF.

METHODS

A systematic search of PubMed, MEDLINE, and EMBASE databases was performed.

RESULTS

Twenty-four studies that reported univariate analysis results regarding POAF risk factors, published from 2001 to May 2017, were included in this meta-analysis with a total number of 36,834 subjects. Eighteen studies were performed in the United States and Europe and 16 studies were prospective cohort studies. The standardized mean difference (SMD) between POAF and non-POAF groups was significantly different (reported as [SMD: 95% confidence interval, CI]) for age (0.55: 0.47-0.63), left atrial diameter (0.45: 0.15-0.75), and left ventricular ejection fraction (0.30: 0.14-0.47). The pooled odds ratios (ORs) (reported as [OR: 95% CI]) demonstrated that heart failure (1.56: 1.31-1.96), chronic obstructive pulmonary disease (1.36: 1.13-1.64), hypertension (1.29: 1.12-1.48), and myocardial infarction (1.18: 1.05-1.34) were significant predictors of POAF incidence, while diabetes was marginally significant (1.06: 1.00-1.13).

CONCLUSION

The present analysis suggested that older age and history of heart failure were significant risk factors for POAF consistently whether the included studies were prospective or retrospective datasets.

Postoperative atrial fibrillation following cardiac surgery: a persistent complication

Postoperative atrial fibrillation (POAF) is a common, expensive and potentially morbid complication following cardiac surgery. POAF occurs in around 35% of cardiac surgery cases and has a peak incidence on postoperative day 2. Patients who develop POAF incur on average $10 000-$20 000 in additional hospital treatment costs, 12-24 h of prolonged ICU time, and an additional 2 to 5 days in the hospital. POAF has been identified as an independent predictor of numerous adverse outcomes, including a 2- to 4-fold increased risk of stroke, reoperation for bleeding, infection, renal or respiratory failure, cardiac arrest, cerebral complications, need for permanent pacemaker placement, and a 2-fold increase in all-cause 30-day and 6-month mortality. The pathogenesis of POAF is incompletely understood but likely involves interplay between pre-existing physiological components and local and systemic inflammation. POAF is associated with numerous risk factors including advanced age, pre-existing conditions that cause cardiac remodelling and certain non-cardiovascular conditions. Clinical management of POAF includes both prophylactic and therapeutic measures, although the efficacy of many interventions remains in question. This review provides a comprehensive and up-to-date summary of the pathogenesis of POAF, outlines current clinical guidelines for POAF prophylaxis and management, and discusses new avenues for further investigation.

Mitochondrial Dysfunction in Atrial Tissue of Patients Developing Postoperative Atrial Fibrillation

BACKGROUND

Mitochondria are the major site of cellular oxidation. Metabolism and oxidative stress have been implicated as possible mechanisms for postoperative atrial fibrillation (POAF) after cardiac operations. Establishing the precise nature of mitochondrial dysfunction as an etiologic factor for oxidative stress-related cell death and apoptosis could further the understanding of POAF. To establish this relationship, mitochondrial function was studied in patients undergoing cardiac operations that developed POAF and compared it with patients without POAF.

METHODS

Right atrial tissue and serum samples were collected from 85 patients before and after cardiopulmonary bypass. Microarray analysis (36 patients) and RNA sequencing (5 patients) were performed on serum and atrial tissues, respectively, for identifying significantly altered genes in patients who developed POAF. On the basis of these results, Western blot was performed in 52 patients for the genes that were most altered, and functional pathways were established.

RESULTS

POAF developed in 30.6% (n = 26) of patients. Serum microarray showed significant fold changes in the expression of 49 genes involved in inflammatory response, oxidative stress, apoptosis, and amyloidosis (p < 0.05) in the POAF group. Similarly, RNA sequencing demonstrated an increased expression of genes associated with inflammatory response, fatty acid metabolism, and apoptosis in the POAF group (false discovery rate > 0.05). Immunoblotting showed a significant increase in TNFAIP6 (tumor necrosis factor, α-induced protein 6; p = 0.02) and transforming growth factor-β (p = 0.04) after cardiopulmonary bypass in the POAF group. There was a significant decrease in PGC-1α (peroxisome proliferator-activated receptor-γ coactivator-1α; p = 0.002) and CPT1 (carnitine palmitoyltransferase I; p < 0.0005) in the POAF group after cardiopulmonary bypass.

CONCLUSIONS

Compared with patients without POAF, those with POAF demonstrated mitochondrial dysfunction at various levels that are suitable for potential pharmacotherapy.

Perspectives and challenges of antioxidant therapy for atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia associated with significant morbidity and mortality. The mechanisms underlying the pathogenesis of AF are poorly understood, although electrophysiological remodeling has been described as an important initiating step. There is growing evidence that oxidative stress is involved in the pathogenesis of AF. Many known triggers of oxidative stress, such as age, diabetes, smoking, and inflammation, are linked with an increased risk of arrhythmia. Numerous preclinical studies and clinical trials reported the importance of antioxidant therapy in the prevention of AF, using vitamins C and E, polyunsaturated fatty acids, statins, or nitric oxide donors. The aim of our work is to give a current overview and analysis of opportunities, challenges, and benefits of antioxidant therapy in AF.