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[1–4] [PREPRINTER stage]
Original Article
Premature atrial contraction as a predictor of postoperative atrial fibrillation
Asian Cardiovascular & Thoracic Annals 0(0) 1–4 ß The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492314534845 aan.sagepub.com
Makoto Hashimoto1,2, Akihiko Yamauchi1 and Satomi Inoue2
Abstract Background: Postoperative atrial fibrillation occurs in 20%–60% of patients after cardiac surgery. Recently, premature atrial contraction has been considered an initiator of atrial fibrillation. This study evaluated whether the frequency of premature atrial contractions predicts the occurrence of postoperative atrial fibrillation. Methods: The subjects of this study were 70 patients with no history of atrial fibrillation who had undergone a 24-h Holter electrocardiogram before off-pump coronary artery bypass. Their records were reviewed and postoperative electrocardiograms and telemetry strips were analyzed for postoperative atrial fibrillation. Results: Postoperative atrial fibrillation was documented in 22 (31.4%) patients. The frequency of preoperative premature atrial contractions was significantly higher in the postoperative atrial fibrillation group (4128 7186 vs. 69 221 beats/24 h, p < 0.001). The incidence of postoperative atrial fibrillation increased with the frequency of preoperative premature atrial contractions which occurred in 60% of patients in the upper 50th percentile group of preoperative premature atrial contractions. Multivariate logistic regression analysis revealed the upper 50th percentile group of preoperative premature atrial contractions (odds ratio ¼ 67; 95% confidence interval: 5.51–838; p ¼ 0.001) to be an independent predictor of postoperative atrial fibrillation. Conclusion: A high frequency of preoperative premature atrial contractions is a strong independent predictor of postoperative atrial fibrillation in off-pump coronary artery bypass.
Keywords Atrial fibrillation, atrial premature complexes, coronary artery bypass, off-pump, risk factors
Introduction After cardiac surgery, atrial fibrillation (AF) is rather common, occurring in up to 60% of patients.1,2 The mechanism is considered to be a reversible trigger in patients with susceptible underlying electrophysiological substrates such as abnormal automaticity and conduction delay due to atrial incisions, minor ischemia or inflammation caused by the surgery, or a preexisting disease. Postoperative AF adversely affects hemodynamics and increases the risk of stroke and the cost of care.1,3,4 Numerous studies have identified predictors of postoperative AF, such as older age, elevated plasma B-type natriuretic peptide (BNP) levels, use of cardiopulmonary bypass, and venting via the pulmonary vein.1,3,5–7 Premature atrial contraction (PAC), especially an ectopic beat from the pulmonary veins, has
been shown in some studies to be an initiator of AF.8,9 However, no report has suggested the frequency of preoperative PAC as a predictor of postoperative AF in off-pump coronary artery bypass (OPCAB). The aim of this study was to evaluate whether the frequency of preoperative PAC is associated with the occurrence of postoperative AF.
1 Department of Cardiovascular Surgery, Tomishiro Central Hospital, Okinawa, Japan 2 Department of Cardiovascular Surgery, Hokkaido Prefectural Kitami Hospital, Hokkaido, Japan
Corresponding author: Makoto Hashimoto, Department of Cardiovascular Surgery, Tomishiro Central Hospital, 25 Ueta, Tomigusuku City, Okinawa, 901-0243, Japan. Email: [email protected]
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2
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Patients and methods
Results
We reviewed the data of all patients who underwent isolated OPCAB in our institutions from April 2010 to December 2012. Because this study was retrospective and individuals were not identified, the institutional review board of Tomishiro Central Hospital approved this study. Patients who had a history of AF, defined as previous detection of AF on an electrocardiogram (ECG), were excluded from the analysis. In addition, patients with implanted pacemakers were excluded due to the difficulty in 24-h Holter ECG analysis. Seventy consecutive patients formed the study population. Preoperative echocardiography was carried out in all patients, which revealed no concomitant significant valvular disease nor any obvious cardiomyopathy. Beta blockers were used preoperatively in 77% of patients, however, no patient took Naþ or Kþ channel blockers for prevention of arrhythmia preoperatively. Surgery was undertaken with general anesthesia by an anesthesiologist. The left internal thoracic artery was used in all cases, and other bypass grafts included right internal thoracic artery, right gastroepiploic artery, radial artery, and saphenous vein. There was no use of assisted circulation. All patients received beta blockers in appropriate doses postoperatively. A preoperative 24-h Holter ECG (FM-180 s; Fukuda Denshi) was routinely carried out within 1 month before surgery, and analyzed by an examiner and a cardiologist. In our facility, preoperative examination includes a routine 24-h Holter ECG to detect any curable arrhythmias or command cardiac rhythms. Patients were continuously monitored by a telemetry strip to detect the occurrence of AF during hospital stay. When AF was suspected on the telemetry strip, a 12-lead ECG was performed to confirm the diagnosis. In this study, the definition of AF was the absence of a P-wave and an irregular narrow QRS complex on a 12-lead ECG. AF lasting 1 h or more was defined as postoperative AF. The basic management of postoperative AF was immediate defibrillation, electrically or using antiarrhythmic drugs. Unless noted otherwise, all data are presented as mean standard deviation. A p value less than 0.05 was considered significant for all of the following statistical tests. For univariate analysis, continuous variables were analyzed using Student’s t test or the MannWhitney rank sum test, as appropriate, and the chisquare test was used for categorical variables. For multivariate analysis, a stepwise logistic regression model was used to identify independent predictors of postoperative AF. All variables with a p value 0.05 0.05 0.039 0.023 >0.05 0.104 0.105 >0.05 >0.05
BNP: B-type natriuretic peptide; LDL: low-density cholesterol; Postop AF: postoperative atrial fibrillation.
lipoprotein
Table 2. Preoperative 24-h Holter electrocardiogram data in patients with and without postoperative atrial fibrillation. Variable
Postop AF (n ¼ 22)
No postop AF (n ¼ 48)
p value
PAC (beats/24 h) 4128 7186 69 221 0.05 >0.05
AF: atrial fibrillation; BNP: B-type natriuretic peptide; Preop PAC: preoperative premature atrial contractions.
PAC (PAC >47 beats/24 h) was the only independent predictor of postoperative AF (odds ratio ¼ 67; 95% confidence interval: 5.5–838; p ¼ 0.001).
Discussion AF occurs frequently after cardiac operations, thus various situations caused by cardiac surgery have been highlighted as etiologic factors. Major known etiologies include: direct surgical trauma to the heart, causing minor ischemia or postoperative pericarditis; unequal or inadequate cardioplegia during the surgery; sympathetic nervous system disturbance; and electrolyte imbalances.10–14 Well-known predictors of postoperative AF include older age, elevated plasma BNP levels, right coronary artery disease, and venting via the pulmonary veins.1,3,5–7 However, older age seems to be a constant predictor of postoperative AF. Interestingly, despite adjustment for those known predictors of postoperative AF, a high frequency of preoperative PAC, especially in the upper 50th percentile group of preoperative PAC occurrence (PAC >47 beats/24 h), was the strongest independent predictor of postoperative AF in this study. Moreover, the risk of postoperative AF increased with increasing frequency of preoperative PAC. According to the results of this study, the 24-h Holter ECG is certainly a meaningful preoperative measure to predict postoperative AF. PAC is known to be an initiator of AF.8,9 The variation in the refractory period and repolarization timing of each atrial myocardium is thought to be associated with the initiation of PAC-related AF.15 Thus the hypothesis of this study: the higher the frequency of PAC, the greater the incidence of postoperative AF, seems to be reasonable. However, previous studies have not demonstrated preoperative PAC frequency to be a predictor of postoperative AF. Thus this study is meaningful because it identifies a new reasonable predictor of postoperative AF in OPCAB. According to our univariate analysis, smokers and diabetic patients were less likely to develop postoperative AF. The criterion of a smoker in this study was a smoking habit within 1 month before the operation. In our study population, smokers were significantly younger than nonsmokers, which may have affected the result. The reason why diabetic patients developed postoperative AF less often in this study is unclear. However, we assume that the impaired sympathovagal balance in diabetic patients due to diabetic autonomic neuropathy may have affected the result, because autonomic nervous system disturbance is a clue to the development of postoperative AF.12 Numerous studies have revealed adverse outcomes of postoperative AF in cardiac surgeries; most highlight the risks of stroke and renal dysfunction, and increased
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cost of care.1,3,4 Moreover, internal thoracic artery graft flow after coronary artery bypass grafting was shown to deteriorate with postoperative AF, which may severely affect the outcome of surgery.16,17 If there was a highly sensitive and specific way to predict postoperative AF, it would be possible to minimize any adverse outcome by meticulous care. Patients at high risk of postoperative AF should receive, if possible, sufficient prophylactic statins preoperatively and sufficient anticoagulant therapy and beta blocker administration postoperatively, to avoid postoperative AF.18 Moreover, surgical intervention may be the choice of treatment in high-risk patients. Surgical interventions may include left atrial appendage closure to avoid strokes, a maze procedure, or pulmonary vein isolation to prevent the occurrence of postoperative AF. We concluded that the high frequency of preoperative PAC, especially PAC >47 beats/24 h, is a strong predictor of AF after OPCAB. High-risk patients should have meticulous perioperative care to avoid any adverse outcomes related to postoperative AF. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflict of interest statement None declared.
References 1. Almassi GH, Schowalter T, Nicolosi AC, et al. Atrial fibrillation after cardiac surgery: a major morbid event? Ann Surg 1997; 226: 501–513. 2. Creswell LL, Schuessler RB, Rosenbloom M and Cox JL. Hazards of postoperative atrial arrhythmias. Ann Thorac Surg 1993; 56: 539–549. 3. Aranki SF, Shaw DP, Adams DH, et al. Predictors of atrial fibrillation after coronary artery surgery. Current trends and impact on hospital resources. Circulation 1996; 94: 390–397. 4. Lahtinen J, Biancari F, Salmela E, et al. Postoperative atrial fibrillation is a major cause of stroke after onpump coronary artery bypass surgery. Ann Thorac Surg 2004; 77: 1241–1244. 5. Wazni OM, Martin DO, Marrouche NF, et al. Plasma Btype natriuretic peptide levels predict postoperative atrial fibrillation in patients undergoing cardiac surgery [Review]. Circulation 2004; 110: 124–127.
6. Fuller JA, Adams GG and Buxton B. Atrial fibrillation after coronary artery bypass grafting Is it a disorder of the elderly? J Thorac Cardiovasc Surg 1989; 97: 821–825. 7. Mendes LA, Connelly GP, McKenney PA, et al. Right coronary artery stenosis: an independent predictor of atrial fibrillation after coronary artery bypass surgery. J Am Coll Cardiol 1995; 25: 198–202. 8. Haı¨ ssaguerre M, Jaı¨ s P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998; 339: 659–666. 9. Jaı¨ s P, Weerasooriya R, Shah DC, et al. Ablation therapy for atrial fibrillation (AF): past, present and future [Review]. Cardiovasc Res 2002; 54: 337–346. 10. Ishii Y, Schuessler RB, Gaynor SL, et al. Inflammation of atrium after cardiac surgery is associated with inhomogeneity of atrial conduction and atrial fibrillation. Circulation 2005; 111: 2881–2888. 11. Tchervenkov CI, Wynands JE, Symes JF, Malcolm ID, Dobell AR and Morin JE. Persistent atrial activity during cardioplegic arrest: a possible factor in the etiology of postoperative supraventricular tachyarrhythmias. Ann Thorac Surg 1983; 36: 437–443. 12. Kalman JM, Munawar M, Howes LG, et al. Atrial fibrillation after coronary artery bypass grafting is associated with sympathetic activation. Ann Thorac Surg 1995; 60: 1709–1715. 13. Hazelrigg SR, Boley TM, Cetindag IB, et al. The efficacy of supplemental magnesium in reducing atrial fibrillation after coronary artery bypass grafting. Ann Thorac Surg 2004; 77: 824–830. 14. Wahr JA, Parks R, Boisvert D, et al. Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. Multicenter Study of Perioperative Ischemia Research Group. JAMA 1999; 281: 2203–2210. 15. Fan K, Lee K and Lau CP. Mechanisms of biatrial pacing for prevention of postoperative atrial fibrillation—insights from a clinical trial [Review]. Card Electrophysiol Rev 2003; 7: 147–153. 16. Shin H, Hashizume K, Iino Y, Koizumi K, Matayoshi T and Yozu R. Effects of atrial fibrillation on coronary artery bypass graft flow. Eur J Cardiothorac Surg 2003; 23: 175–178. 17. Marazzi G, Iellamo F, Volterrani M, et al. Comparison of effectiveness of carvedilol versus bisoprolol for prevention of postdischarge atrial fibrillation after coronary artery bypass grafting in patients with heart failure. Am J Cardiol 2011; 107: 215–219. 18. Sezai A, Minami K, Nakai T, et al. Landiolol hydrochloride for prevention of atrial fibrillation after coronary artery bypass grafting: new evidence from the PASCAL trial. J Thorac Cardiovasc Surg 2011; 141: 1478–1487.
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(AAN)
[1–4] [PREPRINTER stage]
Original Article
Premature atrial contraction as a predictor of postoperative atrial fibrillation
Asian Cardiovascular & Thoracic Annals 0(0) 1–4 ß The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492314534845 aan.sagepub.com
Makoto Hashimoto1,2, Akihiko Yamauchi1 and Satomi Inoue2
Abstract Background: Postoperative atrial fibrillation occurs in 20%–60% of patients after cardiac surgery. Recently, premature atrial contraction has been considered an initiator of atrial fibrillation. This study evaluated whether the frequency of premature atrial contractions predicts the occurrence of postoperative atrial fibrillation. Methods: The subjects of this study were 70 patients with no history of atrial fibrillation who had undergone a 24-h Holter electrocardiogram before off-pump coronary artery bypass. Their records were reviewed and postoperative electrocardiograms and telemetry strips were analyzed for postoperative atrial fibrillation. Results: Postoperative atrial fibrillation was documented in 22 (31.4%) patients. The frequency of preoperative premature atrial contractions was significantly higher in the postoperative atrial fibrillation group (4128 7186 vs. 69 221 beats/24 h, p < 0.001). The incidence of postoperative atrial fibrillation increased with the frequency of preoperative premature atrial contractions which occurred in 60% of patients in the upper 50th percentile group of preoperative premature atrial contractions. Multivariate logistic regression analysis revealed the upper 50th percentile group of preoperative premature atrial contractions (odds ratio ¼ 67; 95% confidence interval: 5.51–838; p ¼ 0.001) to be an independent predictor of postoperative atrial fibrillation. Conclusion: A high frequency of preoperative premature atrial contractions is a strong independent predictor of postoperative atrial fibrillation in off-pump coronary artery bypass.
Keywords Atrial fibrillation, atrial premature complexes, coronary artery bypass, off-pump, risk factors
Introduction After cardiac surgery, atrial fibrillation (AF) is rather common, occurring in up to 60% of patients.1,2 The mechanism is considered to be a reversible trigger in patients with susceptible underlying electrophysiological substrates such as abnormal automaticity and conduction delay due to atrial incisions, minor ischemia or inflammation caused by the surgery, or a preexisting disease. Postoperative AF adversely affects hemodynamics and increases the risk of stroke and the cost of care.1,3,4 Numerous studies have identified predictors of postoperative AF, such as older age, elevated plasma B-type natriuretic peptide (BNP) levels, use of cardiopulmonary bypass, and venting via the pulmonary vein.1,3,5–7 Premature atrial contraction (PAC), especially an ectopic beat from the pulmonary veins, has
been shown in some studies to be an initiator of AF.8,9 However, no report has suggested the frequency of preoperative PAC as a predictor of postoperative AF in off-pump coronary artery bypass (OPCAB). The aim of this study was to evaluate whether the frequency of preoperative PAC is associated with the occurrence of postoperative AF.
1 Department of Cardiovascular Surgery, Tomishiro Central Hospital, Okinawa, Japan 2 Department of Cardiovascular Surgery, Hokkaido Prefectural Kitami Hospital, Hokkaido, Japan
Corresponding author: Makoto Hashimoto, Department of Cardiovascular Surgery, Tomishiro Central Hospital, 25 Ueta, Tomigusuku City, Okinawa, 901-0243, Japan. Email: [email protected]
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(AAN)
[1–4] [PREPRINTER stage]
2
Asian Cardiovascular & Thoracic Annals 0(0)
Patients and methods
Results
We reviewed the data of all patients who underwent isolated OPCAB in our institutions from April 2010 to December 2012. Because this study was retrospective and individuals were not identified, the institutional review board of Tomishiro Central Hospital approved this study. Patients who had a history of AF, defined as previous detection of AF on an electrocardiogram (ECG), were excluded from the analysis. In addition, patients with implanted pacemakers were excluded due to the difficulty in 24-h Holter ECG analysis. Seventy consecutive patients formed the study population. Preoperative echocardiography was carried out in all patients, which revealed no concomitant significant valvular disease nor any obvious cardiomyopathy. Beta blockers were used preoperatively in 77% of patients, however, no patient took Naþ or Kþ channel blockers for prevention of arrhythmia preoperatively. Surgery was undertaken with general anesthesia by an anesthesiologist. The left internal thoracic artery was used in all cases, and other bypass grafts included right internal thoracic artery, right gastroepiploic artery, radial artery, and saphenous vein. There was no use of assisted circulation. All patients received beta blockers in appropriate doses postoperatively. A preoperative 24-h Holter ECG (FM-180 s; Fukuda Denshi) was routinely carried out within 1 month before surgery, and analyzed by an examiner and a cardiologist. In our facility, preoperative examination includes a routine 24-h Holter ECG to detect any curable arrhythmias or command cardiac rhythms. Patients were continuously monitored by a telemetry strip to detect the occurrence of AF during hospital stay. When AF was suspected on the telemetry strip, a 12-lead ECG was performed to confirm the diagnosis. In this study, the definition of AF was the absence of a P-wave and an irregular narrow QRS complex on a 12-lead ECG. AF lasting 1 h or more was defined as postoperative AF. The basic management of postoperative AF was immediate defibrillation, electrically or using antiarrhythmic drugs. Unless noted otherwise, all data are presented as mean standard deviation. A p value less than 0.05 was considered significant for all of the following statistical tests. For univariate analysis, continuous variables were analyzed using Student’s t test or the MannWhitney rank sum test, as appropriate, and the chisquare test was used for categorical variables. For multivariate analysis, a stepwise logistic regression model was used to identify independent predictors of postoperative AF. All variables with a p value 0.05 0.05 0.039 0.023 >0.05 0.104 0.105 >0.05 >0.05
BNP: B-type natriuretic peptide; LDL: low-density cholesterol; Postop AF: postoperative atrial fibrillation.
lipoprotein
Table 2. Preoperative 24-h Holter electrocardiogram data in patients with and without postoperative atrial fibrillation. Variable
Postop AF (n ¼ 22)
No postop AF (n ¼ 48)
p value
PAC (beats/24 h) 4128 7186 69 221 0.05 >0.05
AF: atrial fibrillation; BNP: B-type natriuretic peptide; Preop PAC: preoperative premature atrial contractions.
PAC (PAC >47 beats/24 h) was the only independent predictor of postoperative AF (odds ratio ¼ 67; 95% confidence interval: 5.5–838; p ¼ 0.001).
Discussion AF occurs frequently after cardiac operations, thus various situations caused by cardiac surgery have been highlighted as etiologic factors. Major known etiologies include: direct surgical trauma to the heart, causing minor ischemia or postoperative pericarditis; unequal or inadequate cardioplegia during the surgery; sympathetic nervous system disturbance; and electrolyte imbalances.10–14 Well-known predictors of postoperative AF include older age, elevated plasma BNP levels, right coronary artery disease, and venting via the pulmonary veins.1,3,5–7 However, older age seems to be a constant predictor of postoperative AF. Interestingly, despite adjustment for those known predictors of postoperative AF, a high frequency of preoperative PAC, especially in the upper 50th percentile group of preoperative PAC occurrence (PAC >47 beats/24 h), was the strongest independent predictor of postoperative AF in this study. Moreover, the risk of postoperative AF increased with increasing frequency of preoperative PAC. According to the results of this study, the 24-h Holter ECG is certainly a meaningful preoperative measure to predict postoperative AF. PAC is known to be an initiator of AF.8,9 The variation in the refractory period and repolarization timing of each atrial myocardium is thought to be associated with the initiation of PAC-related AF.15 Thus the hypothesis of this study: the higher the frequency of PAC, the greater the incidence of postoperative AF, seems to be reasonable. However, previous studies have not demonstrated preoperative PAC frequency to be a predictor of postoperative AF. Thus this study is meaningful because it identifies a new reasonable predictor of postoperative AF in OPCAB. According to our univariate analysis, smokers and diabetic patients were less likely to develop postoperative AF. The criterion of a smoker in this study was a smoking habit within 1 month before the operation. In our study population, smokers were significantly younger than nonsmokers, which may have affected the result. The reason why diabetic patients developed postoperative AF less often in this study is unclear. However, we assume that the impaired sympathovagal balance in diabetic patients due to diabetic autonomic neuropathy may have affected the result, because autonomic nervous system disturbance is a clue to the development of postoperative AF.12 Numerous studies have revealed adverse outcomes of postoperative AF in cardiac surgeries; most highlight the risks of stroke and renal dysfunction, and increased
Downloaded from aan.sagepub.com at KAI NAN UNIV on January 30, 2015
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[1–4] [PREPRINTER stage]
4
Asian Cardiovascular & Thoracic Annals 0(0)
cost of care.1,3,4 Moreover, internal thoracic artery graft flow after coronary artery bypass grafting was shown to deteriorate with postoperative AF, which may severely affect the outcome of surgery.16,17 If there was a highly sensitive and specific way to predict postoperative AF, it would be possible to minimize any adverse outcome by meticulous care. Patients at high risk of postoperative AF should receive, if possible, sufficient prophylactic statins preoperatively and sufficient anticoagulant therapy and beta blocker administration postoperatively, to avoid postoperative AF.18 Moreover, surgical intervention may be the choice of treatment in high-risk patients. Surgical interventions may include left atrial appendage closure to avoid strokes, a maze procedure, or pulmonary vein isolation to prevent the occurrence of postoperative AF. We concluded that the high frequency of preoperative PAC, especially PAC >47 beats/24 h, is a strong predictor of AF after OPCAB. High-risk patients should have meticulous perioperative care to avoid any adverse outcomes related to postoperative AF. Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflict of interest statement None declared.
References 1. Almassi GH, Schowalter T, Nicolosi AC, et al. Atrial fibrillation after cardiac surgery: a major morbid event? Ann Surg 1997; 226: 501–513. 2. Creswell LL, Schuessler RB, Rosenbloom M and Cox JL. Hazards of postoperative atrial arrhythmias. Ann Thorac Surg 1993; 56: 539–549. 3. Aranki SF, Shaw DP, Adams DH, et al. Predictors of atrial fibrillation after coronary artery surgery. Current trends and impact on hospital resources. Circulation 1996; 94: 390–397. 4. Lahtinen J, Biancari F, Salmela E, et al. Postoperative atrial fibrillation is a major cause of stroke after onpump coronary artery bypass surgery. Ann Thorac Surg 2004; 77: 1241–1244. 5. Wazni OM, Martin DO, Marrouche NF, et al. Plasma Btype natriuretic peptide levels predict postoperative atrial fibrillation in patients undergoing cardiac surgery [Review]. Circulation 2004; 110: 124–127.
6. Fuller JA, Adams GG and Buxton B. Atrial fibrillation after coronary artery bypass grafting Is it a disorder of the elderly? J Thorac Cardiovasc Surg 1989; 97: 821–825. 7. Mendes LA, Connelly GP, McKenney PA, et al. Right coronary artery stenosis: an independent predictor of atrial fibrillation after coronary artery bypass surgery. J Am Coll Cardiol 1995; 25: 198–202. 8. Haı¨ ssaguerre M, Jaı¨ s P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998; 339: 659–666. 9. Jaı¨ s P, Weerasooriya R, Shah DC, et al. Ablation therapy for atrial fibrillation (AF): past, present and future [Review]. Cardiovasc Res 2002; 54: 337–346. 10. Ishii Y, Schuessler RB, Gaynor SL, et al. Inflammation of atrium after cardiac surgery is associated with inhomogeneity of atrial conduction and atrial fibrillation. Circulation 2005; 111: 2881–2888. 11. Tchervenkov CI, Wynands JE, Symes JF, Malcolm ID, Dobell AR and Morin JE. Persistent atrial activity during cardioplegic arrest: a possible factor in the etiology of postoperative supraventricular tachyarrhythmias. Ann Thorac Surg 1983; 36: 437–443. 12. Kalman JM, Munawar M, Howes LG, et al. Atrial fibrillation after coronary artery bypass grafting is associated with sympathetic activation. Ann Thorac Surg 1995; 60: 1709–1715. 13. Hazelrigg SR, Boley TM, Cetindag IB, et al. The efficacy of supplemental magnesium in reducing atrial fibrillation after coronary artery bypass grafting. Ann Thorac Surg 2004; 77: 824–830. 14. Wahr JA, Parks R, Boisvert D, et al. Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. Multicenter Study of Perioperative Ischemia Research Group. JAMA 1999; 281: 2203–2210. 15. Fan K, Lee K and Lau CP. Mechanisms of biatrial pacing for prevention of postoperative atrial fibrillation—insights from a clinical trial [Review]. Card Electrophysiol Rev 2003; 7: 147–153. 16. Shin H, Hashizume K, Iino Y, Koizumi K, Matayoshi T and Yozu R. Effects of atrial fibrillation on coronary artery bypass graft flow. Eur J Cardiothorac Surg 2003; 23: 175–178. 17. Marazzi G, Iellamo F, Volterrani M, et al. Comparison of effectiveness of carvedilol versus bisoprolol for prevention of postdischarge atrial fibrillation after coronary artery bypass grafting in patients with heart failure. Am J Cardiol 2011; 107: 215–219. 18. Sezai A, Minami K, Nakai T, et al. Landiolol hydrochloride for prevention of atrial fibrillation after coronary artery bypass grafting: new evidence from the PASCAL trial. J Thorac Cardiovasc Surg 2011; 141: 1478–1487.
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