New drugs for atrial fibrillation

Oxidative stress and inflammation as central mediators of atrial fibrillation in obesity and diabetes

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans. Several risk factors promote AF, among which diabetes mellitus has emerged as one of the most important. The growing recognition that obesity, diabetes and AF are closely intertwined disorders has spurred major interest in uncovering their mechanistic links. In this article we provide an update on the growing evidence linking oxidative stress and inflammation to adverse atrial structural and electrical remodeling that leads to the onset and maintenance of AF in the diabetic heart. We then discuss several therapeutic strategies to improve atrial excitability by targeting pathways that control oxidative stress and inflammation.

Perioperative ascorbic acid supplementation does not reduce the incidence of postoperative atrial fibrillation in on-pump coronary artery bypass graft patients

BACKGROUND

Atrial fibrillation is the most common arrhythmia following cardiac surgery. It is associated with increased hemodynamic instability, systemic embolization, and complications linked to anticoagulant therapy. Oxidative stress and consequent electrophysiological remodeling have been proposed as a cause of postoperative atrial fibrillation. Ascorbic acid supplementation was suggested as a novel and effective preventive agent. The aim of this study was to evaluate the capability of ascorbic acid to reduce the incidence of postoperative atrial fibrillation in coronary artery bypass grafting (CABG) patients.

METHODS

A prospective randomized single-center trial was conducted in patients scheduled for an elective on-pump CABG surgery. Subjects in the ascorbic acid group received 2g of ascorbic acid 24h and 2h before the surgery and 1g twice a day for five days after the surgery. Postoperatively, the patients were monitored for atrial fibrillation and other complications.

RESULTS

The ascorbic acid group consisted of 52 patients and the control group included 53 patients. The groups were well matched for baseline demographics, preoperative medications, comorbidities, and had similar intraoperative characteristics. The incidence of atrial fibrillation in the ascorbic acid group was 13.5% and 18.9% in the control group (p=0.314). No difference was found between groups in the time of occurrence of atrial fibrillation (3.71±1.89 vs. 2.91±1.58 days after the surgery; p=0.342). There was also no difference in the other observed postoperative complications.

CONCLUSIONS

The results of this study do not support the effectiveness of ascorbic acid supplementation in reducing the incidence of postoperative atrial fibrillation in elective on-pump CABG patients.

Biomarkers of structural remodelling and endothelial dysfunction for prediction of cardiovascular events or death in patients with atrial fibrillation

INTRODUCTION

Atrial fibrillation (AF) is associated not only with inflammation but also with structural remodelling and altered endothelial activation which may contribute to clot formation, embolization and mortality. We aimed to determine the predictive value of single-time biomarker analysis for prediction of outcome in patients with AF.

METHODS AND RESULTS

We conducted a prospective study to evaluate if biomarkers of structural, electrical or endothelial remodelling are predictive of cardiovascular events (composite primary endpoint of myocardial infarction, stroke, peripheral embolism or death). Secondary endpoint was all-cause mortality. Patients with any type of AF and without active inflammatory conditions were eligible. Plasma samples were collected for ELISA analysis of biomarkers (inflammation [hsCRP, sCD40L], structural [MMP-2] and endothelial remodelling [vWF, sVCAM-1]) at enrolment. Patients (n = 278) were followed for 28 ± 12 (median 32) months. Eighty-eight individuals (32%) experienced a primary outcome event, including 8 (2.9%) with myocardial infarction, 13 (4.8%) with stroke and 4 (1.5%) with peripheral embolism. Predictors of the primary endpoint were age >75 years, CHADS(2)-score >2, LVEF <35%, diabetes, presence of an ICD/pacemaker, elevated vWF, sVCAM-1 and MMP-2 levels. On multivariate regression analysis, only age >75 years, sVCAM-1 and MMP-2 levels remained independently associated with the endpoint. There were 75 deaths during follow-up. Age >75 years, reduced LVEF, elevated sVCAM-1 and MMP-2 levels were predictors of all-cause mortality.

CONCLUSION

In this cohort of AF patients, old age, elevated sVCAM-1 and MMP-2 levels were associated with cardiovascular events. Our data indicate that single-time biomarker assessment may be a useful tool to improve risk stratification schemes.

The antiarrhythmic properties of quifenadine, H1-histamine receptor blocker in children with premature beats: a randomized controlled pilot trial

Despite evolving success of mini-invasive techniques in treating cardiac arrhythmias in children, pharmaceuticals remain the cornerstone therapeutic option. Beyond conventional antiarrhythmic agents such as amiodarone, local anesthetics, tranquilizers, anticonvulsants, and neuroleptics exhibit antiarrhythmic properties. H(1)-histamine receptor blockers are widely used in treating allergies in children. Observational studies suggest efficacy of these agents for treating or preventing tachyarrhythmias, although prolongation of QT interval, and ventricular arrhythmias occur. We determined safety and efficacy of antihistamine, quifenadine, versus conventional amiodarone on cardiac rhythm in children with frequent premature beats (PB). One hundred and four patients (mean age 10.8 +/- 3.2 years) with ventricular (n = 65), supraventricular (n = 39) PB were randomized 1:1 to quifenadine (2 mg kg(-1) day(-1); n = 54), or amiodarone (9 mg kg(-1) day(-1), n = 50) arms. Both groups were treated for 2 weeks. All patients underwent 24-hour Holter monitoring 3 times: before at 14-28 days after randomization, and during the follow up at 2-3 months. The mean frequency of PB in quifenadine group was 562 +/- 61 per hour and 597 +/- 78 per hour in the amiodarone-treated children. Full antiarrhythmic efficacy (PB < 75% from baseline) has been achieved in 23/54 (43%) of quifenadine-treated patients, which was less than after amiodarone treatment (37/50, 74%, P = 0.02). Quifenadine was mostly beneficial in children with supraventricular PB and/or bradycardia than in those with ventricular PB; it was associated with a trend toward increased heart rate during day (88.5 +/- 8.4 beats/min) and night (67.3 +/- 6.2) compared with amiodarone (79.6 +/- 7.8 and 56.1 +/- 5.7 beats/min, respectively; P = 0.04). The incidence of side effects in quifenadine group (drowsiness and headache) was low (2%) in contrast to the alarming 40% risk associated with amiodarone therapy. Quifanidine exhibits antiarrhythmic activity in children with frequent PB, without significant QT prolongation, or sinus node depression. Although, H(1)-histamine receptor blocker is less potent than amiodarone, much better safety profile of quifenadine is advantageous, especially in children. Future large trials with proving novel antihistamines pleiotropy are warranted.

Use of vitamins C and E as a prophylactic therapy to prevent postoperative atrial fibrillation

Oxidative stress has been strongly involved in the underlying mechanism of atrial fibrillation, particularly in the arrhythmia occurring in patients undergoing cardiac surgery with extracorporeal circulation (postoperative atrial fibrillation). The ischemia/reperfusion injury thus occurring in the myocardial tissue contributes to the development of tissue remodeling, thought to be responsible for the functional heart impairment. Consequently, structural changes due to the cardiac tissue biomolecules attack by reactive oxygen and/or nitrogen species could account for functional changes in ion channels, transporters, membrane conductance, cytosolic transduction signals, and other events, all associated with the occurrence of arrhythmic consequences. The lack of success and significant side effects of anti-arrhythmic drugs have given rise to attempts aimed to develop alternative novel pharmacologic treatments. On this line, the biological properties of the antioxidant vitamins C and E suggest that they could decrease the vulnerability of the heart to the oxidative damage. Nevertheless, very few studies to assess their anti-arrhythmic effects have been reported in humans. The clinical and experimental evidence supporting the view that the pharmacological use of antioxidant vitamins could contribute to prevent postoperative atrial fibrillation is presented.