Comparison of propafenone versus procainamide for the acute treatment of atrial fibrillation after cardiac surgery

Update on Management of Postoperative Atrial Fibrillation After Cardiac Surgery

Postoperative atrial fibrillation (POAF) after cardiac surgery remarkably remains the most prevalent event in perioperative cardiac surgery, having great clinical and economic implications. The purpose of this study is to present recommendations based on international evidence and adapted to our clinical practice for the perioperative management of POAF. This update is based on the latest current literature derived from articles and guidelines regarding atrial fibrillation.

Postoperative arrhythmias after cardiac surgery: incidence, risk factors, and therapeutic management

Arrhythmias are a known complication after cardiac surgery and represent a major cause of morbidity, increased length of hospital stay, and economic costs. However, little is known about incidence, risk factors, and treatment of early postoperative arrhythmias. Both tachyarrhythmias and bradyarrhythmias can present in the postoperative period. In this setting, atrial fibrillation is the most common heart rhythm disorder. Postoperative atrial fibrillation is often self-limiting, but it may require anticoagulation therapy and either a rate or rhythm control strategy. However, ventricular arrhythmias and conduction disturbances can also occur. Sustained ventricular arrhythmias in the recovery period after cardiac surgery may warrant acute treatment and long-term preventive strategy in the absence of reversible causes. Transient bradyarrhythmias may be managed with temporary pacing wires placed at surgery, but significant and persistent atrioventricular block or sinus node dysfunction can occur with the need for permanent pacing. We provide a complete and updated review about mechanisms, risk factors, and treatment strategies for the main postoperative arrhythmias.

Postoperative atrial fibrillation

Atrial fibrillation is a common arrhythmia that occurs after cardiac surgery. It is associated with an increase in morbidity, length of hospital stay and mortality. Patients who are at higher risk of postoperative atrial fibrillation should receive prophylactic treatment. Atrial fibrillation usually resolves spontaneously after heart rate is controlled; however, if patients are highly symptomatic or hemodynamically unstable, sinus rhythm should be restored by electrical or pharmacologic cardioversion.

Postoperative atrial fibrillation

Atrial fibrillation is a common arrhythmia after cardiac surgery. It is associated with an increase in morbidity, length of hospital stay, and mortality. Patients who are at higher risk of postoperative atrial fibrillation should receive prophylactic treatment. Atrial fibrillation usually resolves spontaneously after heart rate is controlled; however, if patients are highly symptomatic or hemodynamically unstable, sinus rhythm should be restored by electrical or pharmacologic cardioversion. Patients with atrial fibrillation of more than 48 hours should receive antithrombotic therapy for thromboembolism prevention.

The Quebec Heart Institute: 50 years of excellence in cardiology

The Quebec Heart Institute was established in 1957 at the Laval Hospital in Sainte-Foy, Quebec. Since then, clinical and research activities have made this Institute one of the largest tertiary care cardiology centres in Canada. With its vast catchment area of more than 3,000,000 people, the Institute has developed a strong collaboration with referral physicians centred on clinical, teaching and research interests. The Institute pioneered several aspects of cardiac surgery, invasive cardiology, echocardiography, basic research and, more recently, a network of researchers and clinicians working in the field of 'metabolic cardiology'. The first 50 years of the Quebec Heart Institute are depicted in this overview, which will also introduce this special supplement to The Canadian Journal of Cardiology.

Comparison of intravenous ibutilide vs. propafenone for rapid termination of recent onset atrial fibrillation

This study was to evaluate the efficacy and safety of ibutilide and propafenone given intravenously in converting recent onset atrial fibrillation (AF). Eighty-two consecutive patients with AF (onset in 2 h to 90 days) were randomly assigned to receive two 10-min infusions, 10 min apart, of either ibutilide (1 mg) or propafenone (70 mg). The treatment was considered successful if sinus rhythm occurred within 90 min after the beginning of infusion. Ibutilide had a significantly higher rate of cardioversion than propafenone (70.73 vs. 48.78%, p = 0.043). The patients with shorter AF duration or smaller left atrium diameter had a higher success rate. Nonsustained monomorphic ventricular tachycardia was the most serious adverse effect of ibutilide in 9.76% of patients, and hypotension and heart pause were the major serious adverse events in 17.07% of patients treated with propafenone. Ibutilide is more effective than intravenous propafenone for the cardioversion of recent onset AF, and the adverse effects are rare and transient.

Prophylaxis and management of postoperative atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia seen after cardiac surgery. It is associated with prolongation of hospital stay, postoperative complications, stroke, mortality, and increased hospital cost. Several prevention strategies have been proven effective in reducing postoperative AF; in addition, active prevention of postoperative AF is associated with a decrease in the length of hospital stay and a reduction trend in hospital costs. In patients with postoperative AF, restoration and maintenance of sinus rhythm and rate control are adequate treatment alternatives in the majority of cases. In severely symptomatic or hemodynamically compromised patients urgent cardioversion is needed. Adequate oral anticoagulation may be indicated for a limited period of time.

Pharmacologic Control of Rhythm

Of the 128 articles evaluated on the overall topic of atrial fibrillation (AF) after cardiac surgery, only 19 studies dealing with pharmacologic heart rhythm control were relevant for inclusion in this analysis, indicating the relative paucity of evidence-based studies addressing this topic. We found limited data on guiding treatment for the rhythm control of AF following cardiac surgery in patients who do not require urgent cardioversion; therefore, the choice of an antiarrhythmic drug needs to be guided by patient characteristics. Based on limited available evidence, amiodarone is recommended for pharmacologic conversion of postoperative AF and AFL in patients with depressed left ventricular function who do not need urgent electrical cardioversion. This recommendation is made largely because of the effectiveness of amiodarone and also because of its relatively favorable side-effects profile. Sotalol and class 1A antiarrhythmic drugs are reasonable choices for patients with coronary artery disease who do not have congestive heart failure. There are currently no definitive data to guide the decision about the duration of antiarrhythmic drug therapy for patients with AF following cardiac surgery. Most protocols continue therapy with the antiarrhythmic drug for 4 to 6 weeks following surgery, but evidence from randomized studies is lacking.

Acute ventricular rate control in atrial fibrillation and atrial flutter

Atrioventricular node blocking agents including beta-adrenergic blockers, non-dihydropyridine calcium channel blockers and digoxin are usually effective in controlling ventricular rate in atrial fibrillation and flutter. Intravenous beta-blockers and non-dihydropyridine calcium channel blockers are equally effective in rapidly controlling the ventricular rate. The addition of digoxin to the regimen causes a favorable outcome but digoxin as a single agent is generally less effective in slowing the ventricular rate in acute setting. Clonidine, magnesium, and amiodarone have also been used for acute ventricular rate control in atrial fibrillation. Limited data suggest that combination regimens provide better ventricular rate control than any agent alone. The agent of first choice is usually individualized depending upon the clinical situation. Beta-blockers are preferable in patients with myocardial ischemia, myocardial infarction and hyperthyroidism and in post-operative state, but should be avoided in patients with bronchial asthma and chronic obstructive pulmonary disease where non-dihydropyridine calcium channel blockers are preferred. Beta-blockers are preferred drugs used for acute ventricular rate control in atrial fibrillation during pregnancy. In atrial fibrillation with Wolff-Parkinson-White syndrome, beta-blockers, calcium channel blockers and digoxin should be avoided, as these drugs are selective atrioventricular node blockers without slowing conduction through the accessory pathway, which can lead to increased transmission of impulses preferentially through the accessory pathway and precipitate ventricular fibrillation. The drug of choice for atrial fibrillation in pre-excitation syndrome is procainamide but propafenone, flecainide and disopyramide have also been used. When clinical condition is unstable or patient is hemodynamically compromised, immediate electrical cardioversion is the treatment of choice, as the best measure to control ventricular rate is by conversion to sinus rhythm. Factors precipitating rapid ventricular rate should be treated as well.

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.

Impact of informed consent requirements on cardiac arrest research in the United States: exception from consent or from research?

INTRODUCTION

Research in patients with life-threatening illness such as cardiac arrest is challenging since they can not consent. The Food and Drug Administration addressed research under emergency conditions by publishing new criteria for exception from informed consent in 1996. We systematically reviewed randomized trials over a 10-year period to assess the impact of these regulations.

METHODS

Case-control study of published trials for cardiac arrest (cases) and atrial fibrillation (controls.) Studies were identified by using structured searches of MEDLINE and EMBASE from 1992 to 2002. Included were studies using random allocation in humans with cardiac arrest or atrial fibrillation prior to enrollment. Excluded were duplicate publications. Number of American trials, foreign trials and proportion of trials of American origin were compared by using regression analysis. Changes in cardiac arrest versus atrial fibrillation trials were calculated as risk differences.

RESULTS

Of 4982 identified cardiac arrest studies, 57 (1.1%) were randomized trials. The number of American cardiac arrest trials decreased by 15% (95% CI: 8, 22%) annually (P = 0.05). The proportion of cardiac arrest trials of American origin decreased by 16% (95% CI: 10, 22%) annually (P = 0.006). Of 5596 identified atrial fibrillation studies, 197 trials (3.5%) were randomized trials. The risk difference between cardiac arrest versus atrial fibrillation trials being of American origin decreased significantly (annual difference -5.8% (95% CI: -10, -0.1%), P = 0.03).

INTERPRETATION

Fewer American cardiac arrest trials were published during the last decade, when federal consent requirements changed. Regulatory requirements for clinical trials may inhibit improvements in care and threaten public health.

Management of atrial fibrillation in the post-cardiac surgery setting

New onset postcardiac surgery AF is a prevalent problem associated with increased morbidity, hospital expense, and length of stay. Those agents that inhibit beta-adrenergic receptors (class II beta-blockers, sotalol, and amiodarone) have been demonstrated to be successful prophylaxis against postoperative AF. Furthermore, those therapies that do not inhibit beta-receptors are not effective prophylactic agents. Until comparative trials demonstrate a significant reduction in postoperative AF without additional adverse effects for sotalol or amiodarone compared with beta-blockers, class II beta-blockers are the preferred prophylactic therapy. If patients are deemed unable to take beta-blockers, amiodarone is likely the best alternative. Although prophylaxis against postoperative AF seems prudent, the impact of prophylactic therapy on length of stay and hospital costs has not been a primary objective of any randomized trial. Furthermore, no studies have compared prophylactic therapy for every patient versus therapy only for those patients who experience AF after heart surgery. In the absence of data from randomized clinical trials, postoperative AF should be managed in a similar fashion to clinical AF with attention to rate control, anticoagulation, and restoration of sinus rhythm.

Comparison of the effect of class IA antiarrhythmic drugs on transmembrane potassium currents in rabbit ventricular myocytes

BACKGROUND

The blockade of cardiac transmembrane potassium channels, which is commonly seen with various antiarrhythmic drugs, plays an important role in their mechanism of action. We studied and compared the less-explored effects of three Class IA antiarrhythmics on the transient outward current (I(to)) and on the inward rectifier (I(kl)), ATP sensitive (I(KATP)), and delayed rectifier (I(K)) potassium currents in rabbit ventricular myocytes.

METHODS AND RESULTS

Transmembrane currents were measured by applying the whole-cell configuration of the patch-clamp technique at 37 degrees C in myocytes enzymatically isolated from rabbit ventricular preparations. Quinidine (10 microM), disopyramide (10 microM), and procainamide (50 microM) were studied at concentrations close to or exceeding the therapeutic plasma level. All studied drugs significantly decreased the amplitude of I(KATP) (activated by 50 microM pinacidil) and I(K) currents. None of them influenced significantly I(kl). The amplitude of I(to) was decreased by quinidine and disopyramide but was not considerably altered by procainamide. The fast inactivation of I(to) was not changed by procainamide and was significantly accelerated by quinidine and disopyramide.

CONCLUSION

Although quinidine, disopyramide, and procainamide are all classified as Class IA antiarrhythmics, these drugs had different effects on various potassium currents, which may partially explain their distinct effect on repolarization in various cardiac tissues and on cardiac arrhythmias in clinical settings.

Meta-analysis of randomised controlled trials of the effectiveness of antiarrhythmic agents at promoting sinus rhythm in patients with atrial fibrillation

OBJECTIVE

To conduct a meta-analysis of randomised controlled trials to estimate the effectiveness of antiarrhythmic drugs at promoting sinus rhythm in patients with atrial fibrillation.

DESIGN

Articles were identified by using a comprehensive search of English language papers indexed in Medline from 1966 to August 2001. For the outcomes of sinus rhythm and death, a random effects model was used to model repeated assessments within a study at different time points.

SETTING

Emergency departments and ambulatory clinics.

PATIENTS

Patients with atrial fibrillation.

INTERVENTIONS

Antiarrhythmic agents grouped according to their Vaughan-Williams class.

MAIN OUTCOME MEASURES

Sinus rhythm and mortality.

RESULTS

91 articles met a priori criteria for inclusion in the analysis. Median duration of follow up was one day (range 0.04-1096, mean (SD) 46 (136) days). The median proportion of patients in sinus rhythm at follow up was 55% (range 0-100%) and 32% (range 0-90%) receiving active treatment and placebo, respectively. Median survival was 99% (range 55-100%) and 99% (range 55-100%). Compared with placebo, the following drug classes were associated with increased sinus rhythm at follow up: IA (treatment difference 21.5%, 95% confidence interval (CI) 16.3% to 26.8%); IC (treatment difference 33.1%, 95% CI 23.3% to 42.9%); and III (treatment difference 17.4%, 95% CI 11.5% to 23.3%). Class IC drugs were associated with increased sinus rhythm at follow up compared with class IV drugs (treatment difference 43.2%, 95% CI 11.5% to 75.0%). There was no significant difference in mortality between any drug classes.

CONCLUSIONS

Class IA, IC, and III drugs are associated with increased sinus rhythm at follow up compared with placebo. It is unclear whether any antiarrhythmic drug class is associated with increased or decreased mortality.

Assessment of new onset postcoronary artery bypass surgery atrial fibrillation: current practice pattern review and the development of treatment guidelines

BACKGROUND

The incidence of postcoronary artery bypass graft (CABG) atrial fibrillation (AF) is 22.5% at the QEII Health Sciences Centre and the mean length of stay is 5.5 days greater than for those patients who do not experience this complication. Appropriate pharmacological management is important to prevent the potential morbidity from AF, such as thromboembolism, congestive heart failure, cardiogenic shock and coronary ischemia. This project compared current practice patterns in the management of post-CABG AF with local practice pattern beliefs and evidence from the primary literature. Subsequently, treatment guidelines were designed to help guide a rationale treatment approach.

OBJECTIVE

To promote appropriate treatment strategies for post-CABG AF and increase local practitioner awareness of drug-use outcomes by developing consensus treatment guidelines.

DESIGN

There were three phases. In phase 1, a retrospective chart analysis of 35 post-CABG AF patients over three consecutive months was conducted to assess current practice patterns. All published studies on this subject were also collected and analysed. A survey of pharmacological treatment preferences was distributed to local stakeholders during phase 2. The third phase involved the development and implementation of treatment guidelines.

RESULTS

This study identified a highly variable approach to the treatment of post-CABG AF. The mean number of agents used to treat AF post-CABG was two (range 1-4); all patients (100%) were prescribed rate-controlling agents and 37% were prescribed an antiarrhythmic drug. There was also a mismatch between practice pattern beliefs and actual practice.

CONCLUSIONS

This reinforced the need for a consistent treatment approach that was facilitated with the development and implementation of local guidelines.

Intravenous antiarrhythmic agents

Intravenous antiarrhythmic drugs can be used as diagnostic tools; for example, adenosine can be used to reveal the underlying rhythm in narrow QRS tachycardia. Newer class III antiarrhythmic agents, like ibutilide and dofetilide, are effective at the conversion of acute atrial fibrillation; however, electrical cardioversion is still the most effective method for restoration of sinus rhythm in persistent atrial fibrillation. Lidocaine and bretylium in the treatment and prevention of ventricular tachyarrhythmia are de-emphasized because of inefficacy, safety concerns (lidocaine), or shortage of drug (bretylium). Procainamide is effective for stable ventricular tachycardia, and amiodarone is effective in the treatment of shock-refractory ventricular fibrillation. Adrenergic blockade is likely important in the management of tachyarrhythmias, particularly in electrical storm, but more data will be necessary to establish its role.