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Hyperglycemia Predicts AF in STEMIs Original Article Acta Cardiol Sin 2012;28:279-285 Arrhythmia and Electrophysiology Hyperglycemia Increases New-Onset Atrial Fibrillation in Patients with Acute ST-Elevation Myocardial Infarction Hong-Pin Hsu,1 Yu-Lan Jou,1 Tao-Cheng Wu,2,3 Ying-Hwa Chen,2,3 Shao-Song Huang,2,3 Yenn-Jiang Lin,2,3 Li-Wei Lo,2,3 Yu-Feng Hu,2,3 Ta-Chuan Tuan,3 Shih-Lin Chang2,3 and Shih-Ann Chen2,3 Background: Atrial fibrillation (AF) is a frequent complication of acute myocardial infarction, and is often accompanied by an increased morbidity and mortality. The aim of this study was to investigate the predictors and outcome of new-onset AF occurring after acute ST-elevation myocardial infarction (STEMI). Methods: A total of 307 patients with acute STEMI from May 2007 to June 2009 were included in our study. Of those patients, 57 patients experienced new-onset AF during their hospitalization in the coronary care unit with continuous ECG monitoring. The primary endpoint was the occurrence of AF during the hospitalization. The secondary endpoint was the all-cause mortality during a 12-month follow-up period. Results: Two hundred eighty three patients (92.2%) received revascularization during the hospitalization. The patients with new-onset AF after the acute STEMI were older, with lower diastolic blood pressure, higher initial fasting glucose, lower lipid level, and a higher incidence of coronary artery disease history when compared to those without new-onset AF. In a multivariable analysis, the initial fasting glucose level (p = 0.025, OR = 1.007, 95% CI = 1.001~1.012) was an independent predictor of the occurrence of new-onset AF after acute STEMI. New-onset AF was associated with a higher all-cause mortality rate during the follow-up (p = 0.001). Conclusion: A higher initial fasting glucose level was an independent predictor of the occurrence of AF in patients with acute STEMI, which may be associated with a poor prognosis. Key Words: Atrial fibrillation · Hyperglycemia · Myocardial infarction INTRODUCTION and associated with an increased mortality and morbidity.1,2 Those patients with AMI who developed AF were at a greater risk for an acute stroke and mortality during their hospitalization than those without it.3 On the other hand, ventricular tachyarrhythmias are also an important cause of sudden cardiac death in patients with AMI. The patients with ventricular tachyarrhythmias had higher low-density lipoprotein cholesterol (LDL-C) levels and a lower blood pressure on their initial arrival, suggesting that dyslipidemia may impose a higher risk of developing tachyarrhythmias in the acute phase of ST-segment elevation myocardial infarction (STEMI).4 However, the relationship of new-onset AF to the clinical biochemical markers and outcome in the patients with acute STEMI is still not fully clarified. The purpose of this study was Atrial fibrillation (AF) is the most frequently occurring supraventricular tachycardia during an acute myocardial infarction (AMI), with an incidence of 6-21%, Received: June 9, 2011 Accepted: July 13, 2012 1 Division of Cardiology, Department of Internal Medicine, Taipei City Hospital; 2Division of Cardiology, Taipei Veterans General Hospital; 3Department of Medicine and Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine, Taipei, Taiwan. Address correspondence and reprint requests to: Dr. Shih-Lin Chang, Division of Cardiology, Taipei Veterans General Hospital, No. 201, Sec. 2, Shih-Pai Road, Taipei, Taiwan. Tel: 886-2-2875-7156; Fax: 886-2-2873-5656; E-mail: [email protected] 279 Acta Cardiol Sin 2012;28:279-285 Hong-Pin Hsu et al. total creatine kinase (CK) level was < 200 IU/L. AF was detected by the 12-lead ECGs recorded during the entire hospital course and the 24 hour continuous ECG monitoring in the CCU. The ECG monitor automatically detected and recorded any non-sustained or sustained supraventricular and ventricular arrhythmias after the myocardial infarction, and the recording was further confirmed by the CCU doctor. All of the 12-lead ECGs acquired during the hospitalization were confirmed by the cardiologists. Patients who had AF episodes in the past were excluded from the study. The serum lipids, including the total cholesterol (TC), LDL-C, high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), and fasting glucose level were sampled on the morning after the day of admission, and all patients generally should fast for at least 8 hours before checking those biochemical data. The C-reactive protein (CRP) level was checked immediately upon the patient’s arrival at our emergency room. Hypertension was defined as a systolic blood pressure (SBP) of ³ 140 mmHg and/or diastolic pressure (DBP) of ³ 90 mmHg with more than two readings during a resting state, according to the criteria of the Joint National Committee-VII (JNC-VII),6 or those who had taken antihypertensive medications during their daily life. Diabetes mellitus (DM) was defined according to the American Diabetes Association criteria,7 or as those who used oral hypoglycemic agents or insulin for blood sugar control. A past history of coronary artery disease (CAD) was defined according to the results of the previous coronary angiography (CAG) or non-invasive stress imaging. The left atrial (LA) diameter and left ventricular ejection fraction (LVEF) were determined by echocardiography during the hospitalization. The culprit lesion was identified by correlating the coronary angiography with the ST-segment elevation on the admission ECG, and the regional wall motion abnormality in the left ventriculography. Coronary artery stenosis of > 50% in diameter was regarded as significant. The number of diseased arteries was determined accordingly. The hemodynamic status included the SBP, DBP, and heart rate, which were recorded immediately after arrival at the emergency room. to determine the predictors of the risk of developing new-onset AF in the clinical setting of acute STEMI, and to try to elucidate the relationship between new-onset AF and the clinical outcome. PATIENTS AND METHODS A retrospective study was designed and we enrolled those patients admitted to Taipei Veterans General Hospital of Taiwan due to acute STEMI from May 2007 to June 2009. A total of 307 consecutive patients without any documented AF prior to admission were included in this study based on the registration of the coronary care unit (CCU) of Taipei Veterans General Hospital. The outcome within 12 months after discharge was acquired by the medical records of the hospital and telephone communication with family members. The patients included in this study met the following criteria for acute STEMI: (1) chest pain of ³ 30 minutes in duration; (2) electrocardiograph (ECG) showing ST-segment elevation of ³ 0.1 mV in two or more leads; and (3) elevated creatine kinase-MB (CK-MB) isoenzymes or troponin-I within 24 hours of the chest pain. Most of these patients were treated with a primary percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) surgery, or medical control and then an elective PCI according to the guidelines published by the American College of Cardiology/American Heart Association (ACC/AHA).5 All the patients were initially admitted to the CCU, with follow-up cardiac enzyme tests and 12 lead ECGs taken every 6 hours to trace the ST-T change after the acute STEMI. Continuous ECG, blood pressure and oximetry monitoring were performed in all the study patients when they were in the CCU. The medications used during the hospital course, such as aspirin, clopidogrel, anticoagulants, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers, beta-antagonists, lipid-lowering agents, and intravenous or sublingual nitroglycerin were all administered as recommended by the ACC/ AHA guidelines and were continued after discharge from the hospital unless there was any contraindication for the patients. The patients were transferred to an ordinary ward if they became hemodynamically stable, no symptoms of ongoing ischemia were observed, and the Acta Cardiol Sin 2012;28:279-285 Statistical analyses Data are expressed as the mean ± standard deviation. 280 Hyperglycemia Predicts AF in STEMIs CAD into the multivariable analysis, the initial fasting glucose level [odds ratio (OR) = 1.007, confidence interval (CI) = 1.001~1.012, p = 0.025] was an independent predictor of the occurrence of new-onset AF after acute STEMI (Table 2). After a follow-up of 12 months, the patients with new-onset AF had a higher all-cause mortality rate (39.1% vs. 16.0%, p = 0.001) (Figure 1) and a higher rate of cardiovascular death (28.1% vs. 13.6%, p = 0.01) than those without AF. The causes of cardiovascular death included recurrent myocardial infarction (2 patients), decompensated heart failure (35 patients), and ventricular arrhythmias (13 patients). The non-cardiovascular deaths included septic shock (5 patients) and malignant neoplasms (2 patients). Because there was a significant difference in the age between new-onset AF and non-AF, the age was adjusted in a Cox regression model to compare the mortality of these two groups. The all-cause mortality rate of new-onset AF during 12 months was still higher than that for non-AF (Hazard ratio = 1.851, 95% CI = 1.062~3.227, p = 0.03). Chi-square and Fisher’s exact tests were used for categorical data. Student’s t tests were used for continuous data. A univariate analysis of the various clinical variables was performed to determine the predictors of new-onset AF occurring after acute STEMI. The variables selected to be tested in the multivariate analysis (logistic regression) were those with p values of < 0.1 in the univariate models. The survival rate and cumulative survival curve between the two groups were analyzed by a Kaplan-Meier method and log-rank test. The comparison of the all-cause mortality between the sinus rhythm and AF groups was further adjusted by age with a Cox regression analysis. A p value of < 0.05 was considered statistically significant. RESULTS Among the 307 patients admitted due to an acute STEMI, 83% were male and 17% were female. A total of 283 patients (92.2%) received revascularization (either a primary PCI, elective PCI, or CABG), including a primary PCI in 250 patients (81%) during the hospitalization. Nearly half (45.3%) of the patients had a culprit lesion in the left anterior descending coronary artery, 12.1% in the left circumflex coronary artery, 33.2% in the right coronary artery, and 4.9% of those patients had left main coronary disease. Fourteen patients had no definite culprit lesion due to coronary spasms. There were 57 patients (18.6%) that suffered from new-onset AF during the hospital course, and all of them had paroxysmal AF. The comparison of the clinical characteristics in the patients with and without new-onset AF after acute STEMI is shown in Table 1. Patients with new-onset AF had a higher incidence of a CAD history than those without new-onset AF. There was no significant difference in the culprit arteries between the patients with and without new-onset AF. Patients with new-onset AF had a higher mean fasting glucose level. There was a trend for the patients with a history of DM to be associated with a higher occurrence of new-onset AF compared with those without it. The patients with new-onset AF had a lower incidence of a history of hyperlipidemia with a lower triglyceride level and total cholesterol level compared to those without AF. After taking the fasting glucose, TG, and LDL-C levels, age, diastolic BP, TIMI score, history of DM and DISCUSSION New onset of AF after an acute STEMI A variant incidence of AF after an AMI has been reported in previous studies. Goldberg et al. reported that the incidence of new-onset AF after AMI increased from 11.3% to 14.4% during the period 1999 to 2005.2 The development of new-onset AF after AMI was associated with an increase in the mortality and risk of stroke during the hospitalization. A discordant incidence of AF after AMI has been demonstrated in previous studies. Pederson et al. found that the incidence of paroxysmal AF/atrial flutter after AMI was 21%.8 In the GUSTO-I trial, the incidence of AF after AMI was 2.5% on admission and 7.9% after enrollment. In the GRACE trial, the incidence of new-onset AF was 6.2%. In our study, the incidence of new-onset AF after acute STEMI was about 18%, which was higher than that of some other studies (5% to 15%).9-13 The different methodology in the AF detection and varied severity of the disease may account for the discrepancy in results. Continuous ECG monitoring was performed in all of our patients with acute STEMI during the CCU admission, which differed from 281 Acta Cardiol Sin 2012;28:279-285 Hong-Pin Hsu et al. Table 1. Clinical characteristics of the patients with/without AF Age (years) Male gender (%) Heart rate (bpm) Systolic pressure (mmHg) Diastolic pressure (mmHg) Killip Class Class I, n (%) Class II, n (%) Class III, n (%) Class IV, n (%) TIMI score Left atrial diameter (mm) LV ejection fraction (%) Body mass index (Kg/m2) Smoking (%) HbA1C (%) Triglyceride (mg/dl) Total cholesterol (mg/dl) Fasting glucose (mg/dl) HDL-cholesterol (mg/dl) LDL-cholesterol (mg/dl) C-reactive protein (mg/dl) Primary PCI, n (%) Revascularization, n (%) Culprit lesion LAD, n (%) LCX, n (%) RCA, n (%) LM, n (%) Hypertension, n (%) Hyperlipidemia, n (%) Diabetes mellitus, n (%) Coronary artery disease history, n (%) Cerebral vascular disease, n (%) All-cause mortality, n (%) CV death, n (%) Sinus rhythm (n = 250) AF (n = 57) p value 067.3 ± 14.3 83.2 082.2 ± 21.0 130.9 ± 33.0 075.8 ± 18.0 75.2 ± 10.2 80.7 083.7 ± 32.0 121.9 ± 39.8 069.6 ± 19.7 < 0.001 0.80 0.77 0.11 0.04 0.11 107 (42.8%)0 57 (22.8%) 33 (13.2%) 53 (21.2%) 06 ± 3 39.2 ± 6.1 044.6 ± 12.7 25.0 ± 3.5 90 (36.0%) 07.0 ± 1.8 112.5 ± 96.7 164.3 ± 42.2 150.5 ± 80.4 040.4 ± 12.4 105.6 ± 35.6 01.9 ± 0.2 205 (82.0%)0 233 (93.2%)0 18 (31.6%) 11 (19.3%) 07 (12.3%) 21 (36.8%) 08 ± 3 41.1 ± 6.1 042.9 ± 16.3 24.1 ± 4.2 18 (31.6%) 06.9 ± 1.4 081.0 ± 55.7 146.3 ± 40.9 0197.6 ± 111.4 042.5 ± 13.3 093.0 ± 35.3 02.6 ± 0.7 45 (78.9%) 49 (86.0%) 118 (47.6%)0 33 (13.3%) 76 (30.6%) 13 (5.2%)0 161 (64.4%)0 86 (34.4%) 93 (37.2%) 44 (17.6%) 35 (14.4%) 36 (14.4%) 34 (13.6%) 21 (36.8%) 4 (7.0%) 26 (45.6%) 2 (3.5%) 42 (73.7%) 09 (15.8%) 29 (50.9%) 19 (33.3%) 4 (7.0%) 21 (36.8%) 16 (28.1%) < 0.001 0.27 0.63 0.41 0.78 0.83 0.02 0.01 0.01 0.29 0.03 0.21 0.73 0.13 0.10 0.24 0.01 0.08 0.01 0.23 00.001 0.01 AF, atrial fibrillation; CV death, cardiovascular death; HDL, high-density lipoprotein; LAD, left anterior descending artery; LCX, left circumflex artery; LDL, low-density lipoprotein; LM, left main coronary artery; LV, left ventricle; PCI, percutaneous coronary intervention; RCA, right coronary artery. low HDL-C, which are considered to be independent risk factors of AMI, are not independent risk factors of new-onset AF after AMI in our study.14 Previous studies found an increased risk of AF in patients with DM.15-17 Koracevic et al. showed that hyperglycemia is associated with an increased prevalence of AF and higher inhospital mortality in patients after AMI (either STelevation or non-ST elevation). 18 Our study further the other studies, using only one episode of an ECG recording. Moreover, the exclusion of the patients at high risk for AF (acute STEMI) may result in the lower incidence of AF observed in some clinical trials. Metabolic disturbance leads to a new onset of AF Many risk factors, such as hypertension, DM, and Acta Cardiol Sin 2012;28:279-285 282 Hyperglycemia Predicts AF in STEMIs Table 2. Univariate and multivariate analyses of the risk factors for AF Risk factor Age* TIMI score* Diastolic BP* Fasting glucose* LDL-cholesterol* Total triglyceride* Previous CAD history Diabetes mellitus Univariate p value Multivariate p value Odds ratio 95% CI < 0.001 < 0.001 0.04 0.01 0.03 0.02 0.01 0.08 0.206 0.383 0.749 0.025 0.789 0.060 0.709 0.646 1.034 1.117 0.995 1.007 0.998 0.989 0.812 1.295 0.982~1.088 0.871~1.432 0.968~1.023 1.001~1.012 0.983~1.013 0.979~1.000 0.272~2.424 0.430~3.894 * Continuous variable. BP, blood pressure; CAD, coronary artery disease; LDL, low-density lipoprotein; TIMI, Thrombolysis in Myocardial Infarction. animal study, an increased diffuse fibrotic deposition was revealed on histologic examination of diabetic rats.20 Fibrosis in the left atrium plays an important role in determining the dynamics of AF, which could present as an anchor for reentrant circuits and alter the wavefront propagation, causing fractionated electrograms, wave breaks, and conduction delays and thus promoting AF perpetuation.21,22 In the present study, both the TC and TG levels exhibited a negative association with new-onset AF after myocardial infarction. Although the real mechanism underlying this phenomenon remains unclear, it has been suggested that hypolipidemia may cause electrophysiological changes that could increase the occurrence of AF. Annoura et al. found that the TC, TG, and HDL-C were inversely and linearly associated with the incidence of AF in patients. 23 In an animal model study, a cholesterol-fed state led to a longer effective refractory period and shortened the conduction time of the atrium, which resulted in an antiarrhythmic state in rabbits. 23 This could suggest that hypolipidemia may be associated with the occurrence of AF. Although Dublin reported that hyperlipidemia seemed to be more common among new-onset AF,24 Funk found that hyperlipidemia was a negative independent predictor of AF after cardiac surgery.25 Because lipid-lowering medications were often prescribed to patients with hyperlipidemia or CAD at other hospitals, even though they did not have elevated lipid levels, this lipid profile obtained after admission may not truly represent a condition of hyperlipidemia. No previous studies have well defined the presence or absence of hyperlipidemia as an independent predictor of AF, and the real mechanism for the negative association between hyperlipidemia and AF remains unclear. Figure 1. Cumulative survival (all-cause mortality) in patients with and without new-onset atrial fibrillation (AF) during the 12 months after an acute ST elevation myocardial infarction (STEMI). demonstrated that hyperglycemia can predict the occurrence of new-onset AF following STEMI, with a 0.7% increased risk of AF for an elevation in the blood glucose level of 1 mg/dl. The reason why hyperglycemia correlates independently with AF after myocardial infarction is still unclear. Chao et al. have found that patients with abnormal glucose metabolism, including those with DM and those with an impaired fasting glucose, had a lower atrial voltage and longer atrial activation time than those with normal glucose metabolism. The AF recurrence rate after catheter ablation was greater in the abnormal glucose metabolism group than in the normal glucose metabolism group.19 The study supports the hypothesis that hyperglycemia results in damage to the atrial tissue, with subsequent changes in the electrophysiologic properties, which could lead to the genesis of AF. Oxidative stress-related atrial fibrosis in patients with hyperglycemia was a possible mechanism. In an 283 Acta Cardiol Sin 2012;28:279-285 Hong-Pin Hsu et al. 2. Saczynski JS, McManus D, Zhou Z, et al. Trends in atrial fibrillation complicating acute myocardial infarction. Am J Cardiol 2009;104:169-74. 3. Bhatia GS, Lip GY. Atrial fibrillation post-myocardial infarction: frequency, consequences, and management. Curr Heart Fail Rep 2004;1:149-55. 4. Liu YB, Wu CC, Lee CM, et al. Dyslipidemia is associated with ventricular tachyarrhythmia in patients with acute ST-segment elevation myocardial infarction. J Formos Med Assoc 2006; 105:17-24. 5. Krumholz HM, Anderson JL, Bachelder BL, et al. ACCAHA 2008 performance measures for adults with ST-elevation and non-ST-elevation myocardial infarction. Circulation 2008;118: 2596-648. 6. Chobanian AV, Bakris GL, Black HR, et al. and The National High Blood Pressure Education Program Coordinating Committee. The seventh report of the Joint National Committee on prevention, detection, evaluation, and treatment of high blood pressure. JAMA 2003;289:2560-72. 7. James RG, Alberti KGMM, Mayer BD, et al. Report of the expert committee on the diagnosis and classification of diabetes mellitus. Diabetes Care 2003;26:S5-20. 8. Pedersen OD, Bagger H, Kober L, et al. The occurrence and prognostic significance of atrial fibrillation/-flutter following acute myocardial infarction. TRACE Study group. Trandolapril cardiac evalution. Eur Heart J 1999;20:748-54. 9. Crenshaw BS, Ward SR, Granger CB, et al. Atrial fibrillation in the setting of acute myocardial infarction: the GUSTO-I experience. Global utilization of streptokinase and TPA for occluded coronary arteries. J Am Coll Cardiol 1997;30:406-13. 10. Wong CK, White HD, Wilcox RG, et al. Significance of atrial fibrillation during acute myocardial infarction, and its current management: insights from the GUSTO-3 trial. Card Electrophysiol Rev 2003;7:201-7. 11. Mehta RH, Dabbous OH, Granger CB, et al. Comparison of outcomes of patients with acute coronary syndromes with and without atrial fibrillation. Am J Cardiol 2003;92:1031-6. 12. Eldar M, Canetti M, Rotstein Z, et al. Significance of paroxysmal atrial fibrillation complicating acute myocardial infarction in the thrombolytic era. SPRINT and thrombolytic survey groups. Circulation 1998;97:965-70. 13. Goldberg RJ, Yarzebski J, Lessard D, et al. Recent trends in the incidence rates of and death rates from atrial fibrillation complicating initial acute myocardial infarction: a community-wide perspective. Am Heart J 2002;143:519-27. 14. Lin YC, Hsu LA, Ko YS, et al. Impact of conventional cardiovascular risk factors on acute myocardial infarction in young adult Taiwanese. Acta Cardiol Sin 2010;26:228-34. 15. Barriales Alvarez V, Morís de la Tassa C, Sánchez Posada I, et al. The etiology and associated risk factors in a sample of 300 patients with atrial fibrillation. Rev Esp Cardiol 1999;52:403-14. 16. Kalus JS, White CM, Caron MF, et al. Indicators of atrial fibrillation risk in cardiac surgery patients on prophylactic amiodarone. Poor outcome in patients with new-onset AF AF leads to progressive electrical and structural changes to the atria, contributing to the initiation and perpetuation of AF.26 Patients with AMI could have a reduced mortality rate after receiving primary PCI,27 but patients with new-onset AF after an acute STEMI had a higher all cause-mortality after 12 months of follow-up in our study, similar to the findings of other studies.28-30 A new-onset AF can predict the occurrence of a stroke, CHF, and mortality after acute STEMI.31-33 The optimal prevention of AF is to terminate it as soon as possible and interrupt the remodeling of AF.26 Aggressive rhythm control of AF after an acute STEMI may reduce the occurrence of AF after discharge. As shown in this study, a higher initial fasting glucose level could predict the occurrence of AF. Therefore, tight blood sugar control may prevent the occurrence of AF and decrease the recurrence of AF during follow-up. More prospective studies are necessary to prove this hypothesis. LIMITATION In our study, the AF was acquired by both continuous ECG monitoring and the 12-lead ECG. Because continuous ECG monitoring was not routinely used in the ordinary wards, some asymptomatic new-onset AF cases occurring on the ordinary wards may have been undetected. Besides, the LA volume was not routinely measured in this study, which may provide more precise information than the LA diameter. CONCLUSION A higher initial fasting glucose level was an independent predictor of new-onset AF after acute STEMI. In addition, patients with new-onset AF are associated with a poor prognosis. REFERENCES 1. Schmitt J, Duray G, Gersch BJ, et al. Atrial fibrillation in acute myocardial infarction: a systematic review of the incidence, clinical features and prognostic implications. Eur Heart J 2009; 30:1038-45. Acta Cardiol Sin 2012;28:279-285 284 Hyperglycemia Predicts AF in STEMIs Ann Thorac Surg 2004;77:1288-92. 17. 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