- Research article
- Open Access
- Open Peer Review
Does prophylactic sotalol and magnesium decrease the incidence of atrial fibrillation following coronary artery bypass surgery: a propensity-matched analysis
© Aerra et al; licensee BioMed Central Ltd. 2006
- Received: 23 January 2006
- Accepted: 03 March 2006
- Published: 03 March 2006
Atrial fibrillation can occur in up to 40% of patients undergoing coronary surgery.
We retrospectively analysed 103 consecutive coronary surgery patients under the care of one surgeon between April 2003 and September 2003. These patients received 40 mg of sotalol orally twice daily from the first post-operative day for 6 weeks and 2 g of magnesium intravenously immediately post surgery and on the first post-operative day. We developed a propensity score for the probability of receiving sotalol and magnesium after coronary surgery. 89 patients from the sotalol and magnesium group were successfully matched with 89 unique coronary surgery patients who did not receive either sotalol or magnesium with an identical propensity score.
Preoperative characteristics were well matched between groups. There was no significant difference with respect to in-hospital mortality between groups (sotalol and magnesium 1.1% versus control 4.5%; p = 0.17). The incidence of atrial fibrillation in the sotalol and magnesium group was 13.5% compared to 27.0% in the controls (p = 0.025).
The combination of sotalol and magnesium can significantly reduce the incidence of post-operative atrial fibrillation following coronary surgery.
- Atrial Fibrillation
- Coronary Artery Bypass Graft
- Propensity Score
- Coronary Artery Bypass Surgery
Atrial Fibrillation is the most common complication following cardiac surgery with a reported incidence between 20% and 40% [1, 2]. It usually occurs between the second and fourth post-operative day. However, although this complication occurs frequently, the mechanism behind its development is less understood.
Numerous studies have identified and enumerated a variety of risk factors for the development of atrial fibrillation. These include increased age, male gender, history of atrial fibrillation, discontinuation of preoperative βeta-blocker therapy, congestive heart failure, electrolyte depletion (low potassium and magnesium), cardiopulmonary bypass, left atrial dysfunction, severity of coronary artery disease, respiratory disease, and pulmonary vein venting [1–7].
In an effort to prevent the occurrence of atrial fibrillation in the post-operative period, various treatment modalities have been implemented indicating its unclear pathophysiology. The key role of βeta blockers in prevention of atrial fibrillation is well recognised in many randomised control trials [8, 9]. Sotalol has an acceptable safety profile and is emerging as a key drug in the prevention of this complication [9, 10]. The role of magnesium supplements is less clear [11–17].
The present study was done to examine the beneficial role of sotalol and magnesium prophylaxis in the prevention of atrial fibrillation in routine coronary artery bypass graft (CABG) surgery.
Between 1st April 2003 and 30th September 2003, 103 consecutive patients undergoing first time isolated CABG surgery under the care of one surgeon (AYO) were routinely administered sotalol and magnesium (see sotalol and magnesium). These patients were matched to a control group taken from the remaining 487 consecutive patients who received first time isolated CABG surgery performed during the same time period by other surgeons at our institution (see statistical methods).
Patients undergoing CABG that was in addition to heart valve repair or replacement, resection of a ventricular aneurysm or other surgical procedure were not included. Also excluded were patients who had received previous cardiac surgery or patients with a history of atrial arrhythmias.
Propensity-matched patient and disease characteristics
SM (n = 89)
Control (n = 89)
65.9 (59.2 – 70.1)
66.4 (59.2 – 71.9)
Body mass index (kg/m2)
27.1 (24.9 – 30.7)
27.1 (24.7 – 30.2)
Ejection fraction <30%
Triple-vessel disease (%)
Left main stem disease (%)
Angina class IV (%)
Respiratory disease (%)
Renal dysfunction (%)
Peripheral vascular disease (%)
Current smoker (%)
Previous myocardial infarction (%)
Emergent procedure (%)
Preoperative β-blockers (%)
Preoperative diuretics (%)
Preoperative heart rate (bpm)
69.1 (61.8 – 81.9)
70.3 (60.6 – 83.2)
4 (2 – 5)
3 (2 – 5)
Number of grafts (n/patient)
3 (2 – 4)
3 (3 – 4)
CPB not used (%)
Sotalol and Magnesium
Patients received 40 mg of sotalol orally twice daily from the first post-operative day for 6 weeks and 2 g of magnesium intravenously immediately post-coronary surgery and on the first post-operative day. No patients from the control group received sotalol and/or magnesium.
Post-operative atrial fibrillation was defined as the occurrence of new atrial fibrillation in the absence of pre-operative persistent or paroxysmal atrial fibrillation prior to hospital discharge. In-hospital mortality was defined as death within the same hospital admission regardless of cause.
In order to assess the effect of sotalol and magnesium, we performed a propensity-matched cohort analysis . To do this, logistic regression was used to develop a propensity score for sotalol and magnesium group membership. The propensity score included the following variables: age, sex, body mass index, respiratory disease, renal dysfunction, peripheral vascular disease, diabetes, severity of angina and dysponea, hypertension, hypercholesterolaemia, smoking status, extent of disease, ejection fraction, priority and use of cardiopulmonary bypass. The C statistic, which is equivalent to the receiver-operating characteristic curve, for the propensity model was 0.85. Sotalol and magnesium patients were matched with control patients who had an identical 5-digit propensity score. If this could not be done, we then proceeded to a 4-, 3-, 2-, or 1-digit match .
Continuous variables are shown as median with 25th and 75th percentiles and comparisons were made with Wilcoxon rank-sum tests. Categorical variables are shown as a percentage and comparisons were made with Chi-square tests. A forward stepwise logistic regression analysis was performed to identify risk factors for atrial fibrillation, which was adjusted for the propensity score. In all cases a P value < 0.05 was considered significant. All statistical analysis was performed retrospectively with SAS for Windows Version 8.2 (SAS Institute, Cary, NC).
Of the 590 patients who underwent first time isolated CABG at our institution during the study period, 28.0% developed post-operative atrial fibrillation. Of the 103 patients who received sotalol and magnesium, 13.6% developed atrial fibrillation compared to 31.0% in the other patients (p < 0.001).
We were able to successfully match 89 patients who received sotalol and magnesium to unique control patients who did not. Of these, 5 (5.6%) were 5-digit matches, 11 (12.4%) were 4-digit matches, 40 (44.9%) were 3-digit matches, 24 (27.0%) were 2-digit matches, and 9 (10.1%) were a 1-digit match. The patient and disease characteristics of the propensity-matched patients are shown in Table 1.
There was no significant difference with respect to in-hospital mortality between groups (sotalol and magnesium 1.1% versus control 4.5%; p = 0.17). The median length of hospital stay in the sotalol and magnesium group and control group were both 7 days [(25th and 75th percentiles: 6 to 9); p = 0.38].
Independent risk factors for post-operative atrial fibrillation
Odds Ratio †
95% Confidence Interval
0.05 – 0.61
0.18 – 0.89
Body mass index #
0.81 – 0.99
We would like to acknowledge the co-operation given to us by all the Consultant Cardiac Surgeons at the Cardiothoracic Centre-Liverpool.
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