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J Thorac Cardiovasc Surg 2005;129:401-406
© 2005 The American Association for Thoracic Surgery
Cardiopulmonary Support and Physiology |
Department of Cardiothoracic Surgery, Hadassah University Hospital, Jerusalem, Israel
Received for publication March 17, 2004; revisions received June 10, 2004; accepted for publication June 28, 2004. * Address for reprints: Uzi Izhar, MD, Cardiothoracic Surgery Department, Hadassah University Hospital, Jerusalem 91120, Israel (E-mail: izharu{at}bezeqint.net).
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Abstract |
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METHODS: One hundred twenty-nine patients in whom new atrial fibrillation after coronary artery bypass grafting developed and successfully reverted to sinus rhythm were prospectively randomized at dismissal to receive antiarrhythmic therapy for 1 week (group A; n = 44), 3 weeks (group B; n = 42), or 6 weeks (group C; n = 43). Patients were followed up for an additional 4 weeks after discontinuation of antiarrhythmic therapy for detection of recurrent atrial fibrillation.
RESULTS: The incidence of new atrial fibrillation during the study period was 21.2% (256/1206). Among the 129 patients who consented to the study, conversion to sinus rhythm was accomplished with the following medications: amiodarone (group A, 82%; group B, 93%; group C, 88%; P = .29), digoxin (group A, 16%; group B, 7%; group C, 7%; P = .29), ß-blockers (group A, 27%; group B, 19%; group C, 14%; P = .30), calcium channel blockers (group A, 2%; group B, 2%; group C, 0%; P = .60), quinidine (group A, 2%; group B, 2%; group C, 7%; P = .44), and procainamide (group A, 4.5%; group B, 2%; group C, 0%; P = .37). Follow-up was completed in 128 patients (99.2%). There was no significant difference in the recurrence of atrial fibrillation among groups (0%, 2%, and 0% for groups A, B, and C, respectively).
CONCLUSIONS: Patients with new atrial fibrillation after coronary artery bypass grafting, converted to normal sinus rhythm before hospital discharge, have a benign course. Antiarrhythmic therapy as short as 1 week may be appropriate in these patients.
Medical therapy includes various drugs, such as ß-blockers, calcium channel blockers, digoxin, sotalol, amiodarone, quinidine, ibutilide, and procainamide, among others, to control heart rate and restore sinus rhythm.3 When postoperative AF is successfully converted to sinus rhythm, it is unlikely to recur, and nearly all of these patients are discharged from the hospital in sinus rhythm.1 Most of the antiarrhythmic agents have significant cardiac and noncardiac adverse effects.6 It is not clear how soon these patients may discontinue antiarrhythmic therapy to avoid these side effects without risking recurrence of AF. Current recommendations of the American Heart Association and the American College of Cardiology for the management of postoperative AF do not address the duration of antiarrhythmic therapy.7 We hypothesized that the course of antiarrhythmic therapy after CABG should be short and that there should be no difference in the recurrence of AF among groups of patients treated for different times. Therefore, we conducted this prospective randomized study among patients undergoing CABG in whom new-onset postoperative AF developed.
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Methods |
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Patients who received preoperative ß-blockers, providing that these drugs were not prescribed as an antiarrhythmic therapy, were included in the study, and there was no statistical difference in the number of these patients among the 3 groups (group A, 56.8%; group B, 59.5%; group C, 62.7%). Patients continued to receive ß-blockers after surgery as well. If postoperative AF occurred, they were treated with additional antiarrhythmic drugs. When these patients were included in the study, they were discharged with ß-blockers plus the additional antiarrhythmic therapy. By the end of the randomized study duration (1, 3, or 6 weeks), they discontinued only the additional antiarrhythmic drug.
Operative technique
All operations were performed through a median sternotomy. A standard cardiopulmonary bypass technique was instituted in 106 (82%) patients (35 in group A, 37 in group B, and 34 in group C; P = .46) by using aortoatrial cannulation with a roller pump at moderate hypothermia (28°C-32°C). Myocardial protection was based on intermittent antegrade and retrograde tepid blood cardioplegia. Distal anastomoses were performed during a single period of aortic crossclamping, and proximal anastomoses were performed with partial aortic clamping during rewarming. Conduits for bypass included internal thoracic and radial arteries and saphenous veins. Twenty-three patients (9 in group A, 5 in group B, and 9 in group C; P = .6) underwent CABG with an off-pump technique (surgeon's preference).
Management of postoperative AF
Patients did not receive prophylactic antiarrhythmic therapy during the preoperative or postoperative period. Management of postoperative AF consisted of (1) immediate heart rate control by intravenous calcium channel blockers; (2) conversion to sinus rhythm by using an intravenous loading dose of amiodarone (5-7 mg/kg over 30-60 minutes, then 1 g/24 h followed by oral maintenance [200 mg daily]); (3) using alternative antiarrhythmic therapy (ß-blockers, calcium channel blockers, digoxin, quinidine, and procainamide) for patients who were not responsive to amiodarone or had contraindications to its use (bradycardia or atrioventricular block); (4) direct current cardioversion for hemodynamically unstable patients or patients who were not responding to medical therapy; and (5) anticoagulation with intravenous heparin (monitored by partial thromboplastin time twice laboratory control values or higher) for patients who were not converted to sinus rhythm within 48 hours. Patients in whom sinus rhythm was restored were discharged without anticoagulation. All patients received daily aspirin 100 mg for life.
Follow-up
A closed follow-up was designed for the patients included in this study. (1) They were telephoned during the time they were randomized (1, 3, or 6 weeks) for confirmation that they were taking the antiarrhythmic therapy. (2) They received a second call by the day they discontinued therapy for confirmation that ECG recording would be obtained. (3) They received a third call after an additional 4 weeks for confirmation that a second ECG would be obtained. (4) They participated in an outpatient visit by the end of the follow-up period. (5) They were asked to inform us about any readmission or emergency department visits during the duration of the study. All medical records of readmission were collected. (6) A letter covering all the study details was sent to all family physicians caring for these patients.
Statistical analysis
Data are expressed as absolute numbers or percentages and, where appropriate, as mean ± SD. Continuous variables were compared between groups by means of 1-way analysis of variance. Categorical variables were compared by means of 
2 or Fisher exact tests.
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Results |
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Follow-up and recurrence of AF
All patients were followed up for 4 weeks after discontinuation of medical therapy. Follow-up was completed in 128 patients (99.2%): group A, 100%; group B, 100%; and group C, 98% (P = .82).
Recurrence of AF during the follow-up period was 0% in group A, 2% in group B, and 0% in group C (P = .38). Only 1 patient in group B was readmitted for recurrent asymptomatic AF 1 week after he discontinued the treatment with amiodarone. He was successfully converted to sinus rhythm after resuming amiodarone therapy for another 4 weeks. None of the patients had stroke or episodes of transient ischemic attack during the follow-up period.
Eight patients were readmitted for various reasons: pneumonia, 1 patient; congestive heart failure, 2 patients; pleural effusion, 2 patients; and chest pain, arm wound infection, and AF, 1 patient each (group A, 4.8%; group B, 9.5%; group C, 5%; P = .62).
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Discussion |
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The precise cause and mechanism of the development of postoperative AF has yet to be established. It involves reentry, resulting from dissimilar refractoriness between adjacent atrial areas, without a known reason.10 Risk factors associated with the development of postoperative AF include advanced age, prolonged preoperative atrial conduction, atrial myolysis, chronic obstructive pulmonary disease, excess circulating catecholamines, electrolyte imbalance, atrial myocardial ischemia, ß-blocker withdrawal, prolonged aortic crossclamping time, and right atrial manipulations.1-3
The principles of treatment for new-onset postoperative AF are similar to those for atrial tachyarrhythmias in other clinical circumstances.11 Mainly, 2 management strategies are available to treat patients with persistent AF: rate control and rhythm control.12 Although the rate-control strategy is preferred for patients in whom restoration of sinus rhythm is less important, most patients with new-onset postoperative AF are treated with antiarrhythmic therapy.13 A recent prospective randomized study comparing primary rate control with conversion strategy in postoperative AF showed little difference in time to conversion between the 2 groups of patients.9 This study also did not show a statistically significant reduction in the total length of stay through the conversion strategy, although the time from operation to discharge was significantly decreased.9 The control of ventricular rate, conversion to sinus rhythm, maintenance of regular rhythm, and anticoagulation to protect against thromboembolic complications are the goals of therapy.11
When should we discontinue antiarrhythmic therapy in patients undergoing CABG in whom new-onset postoperative AF develops? The treatment of patients with postoperative AF has not been standardized despite large clinical experience and research.14 There are few data regarding the post–hospital discharge course of patients with this complication.15,16 It is generally believed that there is no need for long-term suppressive therapy because in patients without a history of atrial tachyarrhythmia, once AF is converted to sinus rhythm, it is unlikely to recur.6 However, one of the fundamental questions regarding antiarrhythmic therapy for postoperative AF is whether any therapy should be given at all, once patients are discharged home already in sinus rhythm. We searched the medical literature for guidelines or studies addressing no additional antiarrhythmic therapy at discharge, but we could not find this practice as evidence based. We have demonstrated in this study that the duration of antiarrhythmic therapy in these patients may be very short, from 1 to 3 weeks, no matter what antiarrhythmic drugs have been used. There was no significant difference in the recurrence of AF during the follow-up period among the different therapy groups.
Our results are consistent with the very few studies reporting the frequency of recurrent AF after reversion or conversion to sinus rhythm after surgery. Kowey and associates15 recently reported a retrospective analysis of the intermediate prognosis of patients undergoing CABG who had been treated with different strategies for postoperative AF. They concluded that the rate of recurrence of AF after discharge was similar in patients receiving class I or class III antiarrhythmic drugs together with rate-control agents and in those receiving rate-control drugs alone. Landymore and Howell16 reported on the recurrence of postoperative atrial arrhythmia in patients who had been treated with digoxin for 3 to 8 weeks after CABG. Their data indicated that AF rarely recurred after hospital discharge and was never symptomatic. They concluded that patients in whom new-onset postoperative AF developed should be treated with digoxin for 3 weeks after operation and that drug therapy should then be discontinued indefinitely. Yilmaz and associates17 have found that placebo was comparable to any medication in preventing the recurrence of AF after CABG: the relapse rate within 90 days of operation was 1 of 30 taking placebo, 2 of 30 taking quinidine, 2 of 30 taking verapamil, and 2 of 30 taking amiodarone.
Most of the patients in our study were successfully treated with amiodarone to control AF and maintain sinus rhythm in the postoperative period. Amiodarone, a class III antiarrhythmic agent, increases the refractory period of atrial and ventricular muscle as well as the atrioventricular node. In addition, it has mild ß-blocker and calcium channel blocker activity. It has been reported that the drug is moderately effective for pharmacologic cardioversion of recent-onset AF.18 The conversion rate in patients with AF longer than 7 days is limited. Amiodarone also has been proven effective for conversion of persistent AF.19 A meta-analysis of 91 trials not specifically related to surgery concluded that the relative efficacy of the most commonly used antiarrhythmic drugs seems similar.20 Class IA (quinidine, procainamide, and disopyramide), class IC (flecainide and propafenone), and class III (amiodarone, sotalol, ibutilide, and dofetilide) drugs were all more effective than placebo, converting 40% to 60% of the patients compared with 30% with placebo. Comparisons of class IA or class IC with class III drugs revealed no significant differences. In deciding the nature and duration of drug therapy for postoperative AF, we should consider not only the efficacy of the various antiarrhythmic drugs, but also their undesirable effects. Many previous studies have addressed the increased risk for proarrhythmias—specifically ventricular tachycardia and ventricular fibrillation—when using class I drugs to prevent recurrence of AF.6 Among the other serious side effects of this class of drugs are allergic/immune reactions (lupus-like syndrome), thrombocytopenia, myocardial depression, and gastrointestinal disturbance. Amiodarone, a class III antiarrhythmic drug, has been reported to be effective in preventing and treating postoperative AF.21,22 The dose regimen used in our patients did not result in important side effects, and no-drug related complications were reported during the follow-up period. The half-life of amiodarone is prolonged, ranging from 26 to 107 days.23 Therefore, it is likely that once the patient with postoperative AF is loaded with amiodarone and converted to sinus rhythm, he or she may gain its persistent antiarrhythmic effect for several weeks.22,23 This strengthens our conclusion that the antiarrhythmic therapy after postoperative AF should be brief.
Twenty-four patients from the study population were operated on with the off-pump technique. Recent data indicate that these patients have a similar or lower incidence of postoperative AF than patients with the on-pump technique.24-26 Our incidence of postoperative AF for both groups was not statistically different. Therefore, the off-pump patients who met the criteria of this study were eligible to be included in this trial, and both groups were analyzed together.
Limitations of the study
Holter monitoring was not performed to screen for postoperative AF or other arrhythmia during the postoperative follow-up period. Instead, patients were asked to obtain a 12-lead ECG at the day therapy was discontinued and 4 weeks later. All readmission records were also evaluated for recurrent arrhythmia. The primary goal of the study was to determine when to discontinue the antiarrhythmic therapy for postoperative AF. We believe that failure to detect brief asymptomatic episodes of AF is unlikely to affect patient care or affect it adversely and that this does not detract from the clinical implication of this study.
Conclusions
Postoperative atrial arrhythmia remains a vexing clinical problem, the therapy of which has not yet been standardized. We conclude from our prospective randomized study that antiarrhythmic therapy for postoperative AF in patients undergoing CABG should be brief. A 1- to 3-week period is safe and sufficient in most patients.
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This article has been cited by other articles:
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  G. Buckberg Editorial comment: Left ventricular reconstruction for dilated ischemic cardiomyopathy: biology, registry, randomization, and credibility Eur. J. Cardiothorac. Surg., November 1, 2006; 30(5): 759 - 761. [Full Text] [PDF]
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 R. H. Jones The Year in Cardiovascular Surgery J. Am. Coll. Cardiol., May 16, 2006; 47(10): 2094 - 2107. [Full Text] [PDF]
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