Prevention of atrial fibrillation after cardiac surgery: the significance of postoperative oral amiodarone

Navigating the Incidence of Postoperative Arrhythmia and Hospitalization Length: The Role of Amiodarone and Other Antiarrhythmics in Prophylaxis

Antiarrhythmic drugs play a pivotal role in managing and preventing arrhythmias. Amiodarone, classified as a class III antiarrhythmic, has been used prophylactically to effectively prevent atrial fibrillation postoperatively in cardiac surgeries. However, there is a lack of consensus on the use of amiodarone and other antiarrhythmic drugs as prophylaxis to reduce the occurrence of all types of postoperative arrhythmias in cardiac and non-cardiac surgeries. A comprehensive PubMed query yielded 614 relevant papers, of which 52 clinical trials were analyzed. The data collection included the class of antiarrhythmics, timing or method of drug administration, surgery type, type of arrhythmia and its incidence, and hospitalization length. Statistical analyses focused on prophylactic antiarrhythmics and their respective reductions in postoperative arrhythmias and hospitalization length. Prophylactic amiodarone alone compared to placebo demonstrated a significant reduction in postoperative arrhythmia incidence in cardiac and non-cardiac surgeries (24.01%, p<0.0001), and it was the only treatment group to significantly reduce hospitalization length versus placebo (p = 0.0441). Prophylactic use of class 4 antiarrhythmics versus placebo also demonstrated a significant reduction in postoperative arrhythmia incidence (28.01%, p<0.0001), and while there was no significant statistical reduction compared to amiodarone (4%, p=0.9941), a lack of abundant data provides a case for further research on the prophylactic use of class 4 antiarrhythmics for this indication. Amiodarone prophylaxis remains a prime cornerstone of therapy in reducing postoperative arrhythmia incidence and hospitalization length. Emerging data suggests a need for a broader exploration of alternative antiarrhythmic agents and combination therapies, particularly class 4 antiarrhythmics, in both cardiac and non-cardiac surgeries. This meta-analysis depicts the effectiveness of amiodarone, among other antiarrhythmics, in postoperative arrhythmia incidence and hospitalization length reduction in cardiac and non-cardiac surgeries.

Effect of ColchiciNe on the InciDence of Atrial Fibrillation in Open Heart Surgery Patients: END-AF Trial

BACKGROUND

Atrial fibrillation (AF) is a common arrhythmia in patients undergoing cardiac surgery and may result in significant morbidity and increased hospital stay. This study was conducted to determine if colchicine administered preoperatively to patients undergoing cardiac surgery and continued during hospitalization is effective in reducing the incidence of postoperative AF.

METHODS

In this multicenter prospective randomized open-label study, consecutive patients with no history of AF and scheduled to undergo elective cardiac surgery (n = 360) were randomized to colchicine (n = 179) or no-colchicine (n = 181). Main exclusion criteria were history of AF or supraventricular arrhythmias or absence of sinus rhythm at enrolment, and contraindications to colchicine. Colchicine was orally administered 12 to 24 hours preoperatively and continued until hospital discharge. The primary efficacy end point was documented AF lasting more than 5 minutes. Safety end point was colchicine adverse effects.

RESULTS

In-hospital mortality was 3.3%. The primary end point of AF occurred in 63 patients (17.5%): 26 (14.5%) in the colchicine group and 37 (20.5%) in the no-colchicine group (relative risk reduction 29.3% [P = .14]). Diarrhea occurred in 54 patients, 44 (24.6%) on colchicine and 10 (5.5%) on no-colchicine (P < .001). Diarrhea led to discontinuation of colchicine in 23 (52%) of the 44 patients.

CONCLUSION

Colchicine administered preoperatively to patients undergoing cardiac surgery and continued until hospital discharge failed to significantly reduce the incidence of early postoperative AF. Diarrhea was the most common adverse effect of colchicine leading to its discontinuation in more than half of the patients with this adverse effect.

Prevention and management of perioperative arrhythmias in the thoracic surgical population

Although bradyarrhythmias or malignant ventricular tachyarrhythmias have been reported in less than 1% of patients following noncardiac surgery, rapid atrial arrhythmias more frequently affect the elderly who undergo thoracic operations. This article focuses on new issues leading to the improved understanding of the pathophysiology and mechanisms of postoperative atrial arrhythmias. It discusses new risk factors and a prediction rule for postthoracotomy atrial fibrillation (AF), reviews prophylaxis and acute therapeutic interventions for postthoracotomy AF, and highlights the most recent recommendations of the American Heart Association Task Force on the management of patients who have AF with emphasis on preventing thromboembolic events.

The Changing Face of Postoperative Atrial Fibrillation Prevention

Atrial fibrillation is the most common postoperative arrhythmia with significant consequences on patient health. Postoperative atrial fibrillation (POAF) complicates up to 8% of all noncardiac surgeries, between 3% and 30% of noncardiac thoracic surgeries, and between 16% and 46% of cardiac surgeries. POAF has been associated with increased morbidity, mortality, and longer, more costly hospital stays. The risk of POAF after cardiac and noncardiac surgery may be affected by several epidemiologic and intraoperative factors, as well as by the presence of preexisting cardiovascular and pulmonary disorders. POAF is typically a transient, reversible phenomenon that may develop in patients who possess an electrophysiologic substrate for the arrhythmia that is present before or as a result of surgery. Numerous studies support the efficacy of beta-blockers in POAF prevention; they are currently the most common medication used in POAF prophylaxis. Perioperative amiodarone, sotalol, nondihydropyridine calcium channel blockers, and magnesium sulfate have been associated with a reduction in the occurrence of POAF. Biatrial pacing is a nonpharmacologic method that has been associated with a reduced risk of POAF. Additionally, recent studies have demonstrated that hydroxymethylglutaryl-CoA reductase inhibitors may decrease the risk of POAF. Finally, based on recent evidence that angiotensin converting enzyme inhibitors and angiotensin receptor blockers reduce the risk of permanent atrial fibrillation, these medications may also hold promise in POAF prophylaxis. However, there is a need for further large-scale investigations that incorporate standard methodologies and diagnostic criteria, which have been lacking in past trials.

Amiodarone Prophylaxis for Atrial Fibrillation After Cardiac Surgery: Meta-Analysis of Dose Response and Timing of Initiation

STUDY OBJECTIVE

To investigate a possible dose-response relationship between amiodarone and reduction in incidence of postoperative atrial fibrillation, and to determine whether pre- or postoperative initiation of amiodarone is superior.

DESIGN

Meta-analysis of randomized controlled trials.

DATA SOURCE

MEDLINE and EMBASE databases and the Cochrane Central Register of Controlled Trials for English-language reports published between 1966 and December 2005.

MEASUREMENTS AND MAIN RESULTS

Of 23 identified randomized controlled trials of amiodarone prophylaxis of postoperative atrial fibrillation, 14 were included in the final analysis. These studies enrolled a total of 2864 patients. For each study, the total administered amiodarone dose--categorized as low (< 3000 mg), medium (3000-5000 mg), or high (> 5000 mg)--and preoperative versus postoperative initiation were aggregated by using meta-analytic techniques. The incidence of postoperative atrial fibrillation was significantly reduced by amiodarone compared with placebo (p<0.001). Although the odds of developing atrial fibrillation appeared to be somewhat higher in the low-dose group, no significant differences were noted in the odds ratios (ORs) of developing atrial fibrillation among the low-, medium-, and high-dose groups: OR 0.58, 95% confidence interval (CI) 0.44-0.77; OR 0.45, 95% CI 0.30-0.69; and OR 0.44, 95% CI 0.33-0.58; respectively (p=0.238). In addition, the ORs for atrial fibrillation development associated with preoperative and postoperative initiation of amiodarone were not significantly different (OR 0.50, 95% CI 0.39-0.63; and OR 0.48, 95% CI 0.37-0.63; respectively, p=0.862).

CONCLUSION

Total amiodarone doses of 3000 mg or higher may be more effective than lower doses in reducing the rate of postoperative atrial fibrillation after cardiac surgery. Preoperative initiation of amiodarone appears to be unnecessary. These findings require confirmation in prospective, randomized trials.

Inflammation effects on the electrical properties of atrial tissue and inducibility of postoperative atrial fibrillation

BACKGROUND

Atrial fibrillation is the most common complication after cardiac surgery. Postoperative atrial fibrillation (PAF) has been shown to increase length of stay, morbidity, and mortality. Because the clinical behavior of PAF parallels that of inflammation following surgery, we investigated the effect of the inflammatory mediator arachidonic acid on the electrical behavior of normal atrial tissue in vitro and assessed the efficacy of the topical application of anti-inflammatory drugs at suppressing PAF in an animal model.

METHODS

To study changes in electrical behavior from inflammation, the conduction properties of six normal canine right atrial appendages were quantified as a function of the direction of impulse propagation with and without 80 mum arachidonic acid. To study the effect of topical anti-inflammatory drugs, 24 adult mongrel dogs were prepared according to the model of sterile talc pericarditis. Nine dogs received talc alone (T), seven received talc combined with 600 mg ibuprofen (T + I), and eight received talc combined with 10 mg methylprednisolone (T + M). Three days following preparation, programmed electrical stimulation was performed to quantify conduction characteristics and to attempt the induction of atrial fibrillation (AF).

RESULTS

In vitro, arachidonic acid produced an anisotropic and rapidly reversible 36.1 +/- 3.4% (P = 0.01) decrease in conduction velocity transverse to the long axis only. In vivo, both ibuprofen and methylprednisolone significantly reduced the incidence of sustained AF (from 56 to 0% T + I and 12% T + M, respectively, P = 0.02). No differences in conduction velocities or refractory periods were seen during sinus rhythm among the groups.

CONCLUSIONS

Acute inflammation as mimicked by arachidonic acid slows conduction anisotropically, mainly transverse to the long axis of the atrial myocardial fibers. This may set the stage for reentry. Preventing inflammation in vivo by the topical application of anti-inflammatory drugs supports this hypothesis, suggesting a possible role for inflammation in the genesis of postoperative atrial fibrillation and shedding light on the mechanism underlying PAF.

Effects of amiodarone and thoracic epidural analgesia on atrial fibrillation after coronary artery bypass grafting

OBJECTIVE

This study was designed to assess the effects of a perioperative dosing regimen of amiodarone administration, high thoracic epidural anesthesia (TEA), or a combination of the 2 regimens on atrial fibrillation (AF) after coronary artery bypass grafting (CABG).

DESIGN AND SETTING

The study was prospective, controlled, and randomized and was performed in a tertiary health care center associated with a university.

PARTICIPANTS

One hundred sixty-three patients scheduled for coronary artery bypass graft surgery.

INTERVENTIONS

In this 2 x 2 factorial-designed study the patients were randomized to 1 of 4 regimens in which group E had perioperative TEA, group E+A had TEA and amiodarone, group A had amiodarone, and group C served as control. The epidural catheter was inserted at T1-3 the day before surgery. TEA groups received TEA for 96 hours. The amiodarone regimen consisted of a single loading dose of 1,800 mg of amiodarone orally. Intravenous infusion of amiodarone was started after induction of anesthesia and was administered at 900 mg over 24 hours for the subsequent 3 days.

MEASUREMENTS AND MAIN RESULTS

AF was documented using Holter monitoring. In group E 22 of 44 (50%), in group E+A 10 of 35 (28.6%), in group A 10 of 36 (27.8%), and in the control group 20 of 48 (41.7%) patients developed AF (odds ratio amiodarone/nonamiodarone 0.47 [0.24-0.90]; P = 0.02).

CONCLUSIONS

The perioperative amiodarone regimen used in this study was effective in reducing the incidence of AF after CABG while TEA was not.

Strategies for perioperative arrhythmias

Rapid atrial arrhythmias affect close to one million elderly Americans who undergo cardiac or non-cardiac operations annually and have been associated with prolonged hospital stays. In contrast, bradyarrhythmias or ventricular arrhythmias severe enough to require treatment occur in less than 1% of patients who undergo all types of surgery, including cardiac. This article focuses on new issues leading to the improved understanding of the pathophysiology and mechanisms of post-operative atrial arrhythmias. New approaches directed at prophylaxis and acute therapy of atrial arrhythmias are discussed, as are recommendations to prevent thromboembolic events. Practice and research agenda are proposed.

Interventions for preventing post-operative atrial fibrillation in patients undergoing heart surgery

BACKGROUND

Post-operative atrial fibrillation is a common complication of cardiac surgery and has been associated with increased incidence of other complications including post-operative stroke, increased hospital length of stay and increased cost of hospitalisation. Prevention of atrial fibrillation is a reasonable clinical goal and, consequently, many randomised trials have evaluated the effectiveness of pharmacological and non-pharmacological interventions. We systematically reviewed the literature and prepared meta-analyses to better understand the role and effects of various prophylactic therapies against post-operative atrial fibrillation.

OBJECTIVES

To assess the effects of pharmacological and non-pharmacological interventions for preventing post-cardiac surgery atrial fibrillation.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE and CINAHL from earliest achievable date to June 2003. We hand searched references from reports and earlier reviews. We searched abstract books and CD-ROMs from annual scientific meetings of American College of Cardiology, American Heart Association, North American Society of Pacing and Electrophysiology and European Heart Organization between 1997-2003. No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials comparing pharmacological interventions or non-pharmacological interventions with control treatment, placebo or usual care for the prevention of post-operative atrial fibrillation in post-coronary artery bypass grafting or combined CABG and valvular surgery.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trial quality and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Fifty eight studies were included with a total of 8565 participants. Interventions included were amiodarone, beta blockers, solatol and pacing. Results favoured treatment for post-operative atrial fibrillation. The data for stroke favoured treatment by a non-significant effect size of 0.81, 95% confidence interval 0.51 to 1.28. Similarly, a positive indication for length of stay was derived but it too was not significant with a weighted mean difference of -0.66, 95% confidence interval -0.95 to -0.37. A positive result for cost of hospitalisation in favour of treatment was achieved, but the statistic is not significant due to low power and large standard deviations: a weighted mean difference of -2717, 95% confidence interval 7518 to 2084. Beta-blockers had the greatest magnitude of effect across 28 trials (4074 patients) with an odds ratio (random) of 0.35, 95% confidence interval 0.26 to 0.49. Across all treatment, the odds ratio favoured treatment with a ratio (random) of 0.43, 95% confidence interval 0.37 to 0.51.

REVIEWERS' CONCLUSIONS

Intervention is favoured across the three pharmacological interventions studied and the one non-pharmacological intervention, pacing. The length of stay data favoured treatment (-0.66, 95% confidence interval -0.95 to -0.37).

Postbypass arrhythmias: pathophysiology, prevention, and therapy

PURPOSE OF REVIEW

To review the medical literature on new-onset arrhythmias after cardiac bypass surgery in adults, focusing on the most recent advances on this topic.

RECENT FINDINGS

Main attention is focused on possible predictors and prevention of postoperative atrial fibrillation, because this arrhythmia is the most common type encountered with cardiac surgery and is associated with increased morbidity and mortality and longer, more expensive hospital stays. Therapeutic management of atrial fibrillation favors class III antiarrhythmic agents like amiodarone and sotalol. Direct-current cardioversion proved to be an ineffective method for treatment of supraventricular tachyarrhythmias. In patients with persistent atrioventricular block or sinus node dysfunction after cardiac valve surgery, a risk score to predict the need for permanent pacing after cardiac valve surgery was developed. This scoring system may be useful for pre- and perioperative management of patients undergoing cardiac valve surgery.

SUMMARY

Recent studies demonstrate a continued effort to improve our knowledge about postbypass arrhythmias. New insights in the pathophysiology of postoperative cardiac arrhythmias and advances in prevention and therapy are rapid and results are heterogeneous, so it is difficult for the clinician to keep abreast with these new findings.

Epicardial atrial defibrillation: successful treatment of postoperative atrial fibrillation

BACKGROUND

Atrial fibrillation is the most common complication after cardiac surgery. Current medical treatment using antiarrhythmics and anticoagulants has a significant morbidity. The goal of this study was to determine if epicardial atrial defibrillation can be safely performed and return patients to sinus rhythm.

METHODS

A prospective analysis of patients undergoing cardiac surgery was performed. Patients with a prior pacemaker/defibrillator, history of arrhythmia, preoperative antiarrhythmic, age greater than 85 years, history of stroke, or intraaortic balloon pump were excluded. Temporary epicardial atrial cardioversion wires were placed on the right and left atrium. Bipolar atrial and ventricular pacing wires were also placed. The wires were tested in the operating room. Patients who went into postoperative arial fibrillation were cardioverted with 3 J, 6 J, or 9 J.

RESULTS

There were 45 patients enrolled. Sixteen patients (35%) went into postoperative arial fibrillation during their hospital stay. Mean time to onset of arial fibrillation was 2.6 +/- 1.4 days after surgery. Fifteen patients were successfully cardioverted to sinus rhythm on the primary cardioversion, with mean of 5.7 +/- 2.4 J. One patient was cardioverted at 6 hours after onset of arial fibrillation, at 6 J. Recurrent arial fibrillation occurred in 4 patients during their hospital stay. All 4 of these patients were cardioverted with a mean of 6.4 +/- 2.6 J. All wires were removed the day before patients were discharged. There were no complications with wire insertion or removal. There were no adverse neurologic events. The mean hospital stay was 5.1 +/- 2.2 days. All patients were in sinus rhythm at 1 month follow-up.

CONCLUSIONS

The use of a temporary atrial defibrillator to resynchronize patients in postoperative arial fibrillation is safe and effective.

Perioperative stroke: evaluation, management, and possible preventive measures

Mechanisms of perioperative ischemic stroke include: hypotension, hypercoagulability, arrhythmias with embolism, or direct vascular insult. Mechanisms of perioperative hemorrhagic stroke include: use of antithrombotics, hypertension, or direct vascular insult.

Cardioembolic stroke: an update

Cardioembolic stroke accounts for approximately 15% of all strokes and is thought to be one of the more preventable types of strokes. Features that have been reported to support cardioembolism as a mechanism for ischemic stroke have included documented cardiac source of embolism, maximal neurologic deficit at onset, multiple cerebrovascular territories involved, enhanced tendency toward hemorrhagic transformation, enhanced risk of syncope or seizure associated with presentation, and lower likelihood of premonitory transient ischemic attacks. Features that tend to make cardioembolic stroke less likely include significant cerebral atherosclerosis, step-wise progression of the neurologic deficit within a finite period of time, vascular distribution such as entire internal carotid artery territory with combined middle cerebral artery and anterior cerebral artery involvement or watershed distribution, and premonitory transient ischemic attacks. A number of cardiac conditions can promote thromboembolism, and there is risk stratification reflective of the specific condition or coexistent conditions. Anticoagulant therapy generally has been found to be the most effective means of preventing cardiogenic brain embolism, but the intensity of anticoagulation needs to be optimized to reflect the risk-to-benefit ratio for the particular patient.

The incidence and outcome of ventricular arrhythmias after noncardiac thoracic surgery

Atrial arrhythmias are common after thoracic surgery, but the incidence and significance of ventricular arrhythmias early after such surgery are not well established. Our goal was to determine the incidence and outcome of this complication from a continuing prospective database in 412 patients who had lobectomy (n = 243) or pneumonectomy (n = 169) and were continuously monitored with Holter recorders for 72-96 h postoperatively. The primary end point of the study was the occurrence of ventricular tachycardia (VT) defined as three or more consecutive wide complexes. Sixty-one of 412 patients (15%) developed 1 or more episode of VT. There were no episodes of sustained (>30 s) VT and no patient required treatment for hemodynamic compromise associated with any VT episode. Patients with VT had a more frequent incidence of a preoperative left bundle branch block (P = 0.01) but did not differ in other clinical characteristics, operative data, or core temperature on arrival to the postanesthesia care unit, when compared with those without VT. Patients who developed VT had significantly more atrial premature contractions (P < 0.001), ventricular premature contractions (P < 0.001), ventricular couplets (P < 0.001), and postoperative atrial fibrillation, 21 of 61 (34%) versus 58 of 351 (17%), P = 0.001, than those without VT, respectively. Multivariate logistic regression analysis revealed that only postoperative atrial fibrillation occurrence was independently associated with VT (relative risk 2.6, 95% confidence intervals 1.4 to 4.8, P = 0.002). We conclude that nonsustained VT after noncardiac thoracic surgery occurs frequently but is not associated with poor outcome. The strong association of atrial and ventricular arrhythmogenesis with VT suggests that vagal withdrawal and/or adrenergic hyperactivity may have a role in precipitating these events in the early postoperative period.

IMPLICATIONS

In 412 patients, we determined that the incidence of nonsustained ventricular tachycardia after major thoracic surgery is 15% and is not associated with poor outcome.