several studies suggest that postoperative atrial fibrillation ( poaf ) is associated with an increased duration of hospitalization , early and long term morbidity and mortality [ 2 , 3 ] . off - pump coronary artery by - pass ( cabg ) grafting ( op - cabg ) has been hypothesized to decrease incidence of poaf [ 4 , 5 ] ; however contrasting results has been reported . aim of present prospective investigation was to evaluate the incidence of poaf in patients undergoing isolated surgical revascularization in a tertiary heart surgery centre . patients with poaf were followed for an average period of 2 years to assess the recurrence rate of the arrhythmia and its prognostic role on early and late risk of stroke and mortality . finally , the role of cardiopulmonary by - pass ( cpb ) surgical revascularization ( cpb - cabg ) and op - cabg on poaf was evaluated . study population . among 822 patients who underwent heart surgery between jan 1 2009 and dec 31 2009 in a tertiary heart surgery centre , 229 patients in sinus rhythm on hospital admission ( 179 males , 50 females ) underwent isolated cabg ( 138 - op - cabg , 91 - cpb - cabg ) . patients with atrial fibrillation , hyperthyroidism or scheduled for maze procedure were excluded from the study . in patients undergoing isolated cabg , bipolar maze procedure was usually planned for subjects with persistent or frequent episodes of paroxysmal atrial fibrillation . finally , patients with more than mild valvular disease and creatinine clearace < 30 ml / min were excluded . echocardiographic evaluation was performed within 48 hours before surgery using a sequoia acuson instrument ( siemens medical solution , mount view , ca , usa ) . clinical and echocardiographic characteristics of patients included in the study mean ( standard deviation ) . * bleeding requiring transfusion at least 2 units of packed red blood cells or surgical revision . * * hemodynamic deterioration with the need to infuse amines . op = off pump ; cpb = cardipulonary - by pass ; cabg = coronary artery by - pass ; sd= standard deviation . in table 2 clinical diagnosis , indications for surgery ( elective , urgency / emergency ) , the number of diseased vessels and graft performed in the groups under investigation are reported . op = off pump ; cabg = coronary artery by - pass ; cad = coronary artery disease ; acs = acute coronary syndrome ; stemi = elevated st acute myocardial infarction ; lmc = left main coronary ; lima = left internal mammary artery ; rima = right internal mammary artery ; saph = saphene vein . thirty clinical and echocardiographic variables were considered to evaluate a relationship with occurrence of poaf . after surgery all patients were continuously monitored electrocardiography ( ecg ) , blood pressure , non - invasive oxygen saturation for at least the first 48 hours . transient electric stimulation through epicardic wires was used for severe bradycardia or atrio - ventricular ( av ) block until restoration of heart rhythm . all symptomatic arrhythmic episodes or asymptomatic atrial fibrillation lasting more than 15 minutes at ecg monitoring were considered as poaf and included in the analysis . patients who did not recover sinus rhythm ( sr ) within 30 minutes were usually treated with intravenous amiodarone ( 300 mg in 1 hour followed by 900 mg/24 h e.v . electrical cardioversion was considered when sinus rhythm was not restored within 24 hours after the beginning of pharmacological treatment . perioperative complications including bleeding needing transfusion of at least 2 units of packed red blood cells and/or surgical revision , severe hypotension requiring amines ( norepinephrine , epinephrine , dobutamine or dopamine ) , and new onset av block or severe bradycardia requiring electrical stimulation were recorded . postoperative pericardial inflammation was diagnosed in the presence of pericardial rubs and/or ecg or echocardiogram signs of pericardial involvement . in the end , the study was approved by the ethic committee of our institution and all participants gave their informed consent . holter monitoring was performed every 3 months during the first year and thereafter every 6 months . primary end point of the study was the evaluation of recurrence of atrial fibrillation and related hospitalization ; secondary end points were all cause hospitalization and mortality . finally we evaluated the role of surgical technique ( cpb - cabg vs op - cabg ) on poaf . statistical analysis . data were described as mean and standard deviation ( sd ) for continuous variables and as number and percent for categorical variables . preoperative and operative patient characteristics were compared according to the occurrence of postoperative af by means of the student t test or fisher exact test for continuous and categorical variables , respectively , or finally by anova . in - hospital outcomes . overall incidence of poaf during hospitalization was 24.4% ( 56 of 229 patients ) , 38 males and 18 females . patients who developed af after surgery were older than ones in stable sinus rhythm ( 70.5 vs 64.9 years , p=0.005 ) . poaf was not related to clinical indication to surgery ( elective vs urgency / emergency ) , number of diseased vessels or graft performed ( table 3 ) . comparison of clinical , echocardiographic characteristics and conduits used for grafting between patients with and without poaf according to surgical technique . * bleeding requiring transfusion at least 2 units of packed red blood cells or surgical revision . * * hemodynamic deterioration with the need to infuse amines . poaf = postoperative atrial fibrillation ; op = off pump ; cpb = cardipulonary - by pas ; copd = chronic obstructive pulmonary disease ; cad = coronary artery disease ; acs = acute coronary syndrome ; stemi = elevated st acute myocardial infarction ; lmc= left main coronary ; lima = left internal mammary artery , rima = right internal mammary artery , saph = saphen vein ; sd = stabdard deviation . poaf left ventricular ejection fraction was not significantly lower than in sinus rhythm group ( 49% vs 51% ) . the use of beta - blockers , angiotensin converting enzyme ( ace ) inhibitors / angiotensin a1 receptor ( at1 ) blockers and statins did not influence the prevalence of postoperative af . patients with af did not show a different prevalence of intra - aortic balloon pump use or treatment with vasopressors or inotropic drugs after surgery . transient electric stimulation after surgery was needed in 2 patients with poaf and in 3 who did not develop arrhythmias . multivariate analysis revealed that only antero - posterior left atrium diameter was associated with an increased risk of poaf ( odds ratio = 1.15 ; 95% confidence interval ( ci ) [ 1.02 , 1.30 ] , p<0.001 ) ( table 4 ) . od = odds ratio ; ci = confidence interval ; la = left atrium ; ace = angiotensin - converting - enzyme ; lv = left ventricle ; bp = blood pressure . the frequency of poaf was not statistically different between patients undergoing op - cabg and those undergoing cardiopulmonary by - pass ( 24.6% for op - cabg vs 24.1% for cpb - cabg . ) table 3 reports the relative number of elective in comparison to urgency / emergency procedures , and the number of grafts conduits employed in the two groups . patients with poaf undergoing op - cabg were on average 7 years older than cbp - cabg ( 74.3 vs 67 years , p<0.001 ) . length of hospitalization was on average 2 days longer in patients with poaf after cpb - cabg . the 56 patients with postoperative atrial fibrillation were followed - up for a median of 685 days . age was not significant different in those patients ( average age 72.5 vs 71.3 years ) . among those patients , preoperative left ventricular ejection fraction was not different in patients with af in comparison to patients without recurrence ( 48% vs 49% ) , while mean left atrium anterior - posterior diameter was respectively 42 mm and 40 mm . on average ultimately , in the last patient sinus rhythm could not be restored . at the end of follow up incidence of atrial arrhythmias after cardiac surgery has been reported to range from 10 to 65% . according to a large multi - centre study , poaf after cabg occurs in near 30% . several factors , including type of surgical procedure , patient demographics , criteria used for diagnosis and methods of ecg monitoring , may account for the wide range of poaf incidence reported in literature . dispersion in atrial refractoriness induces multiple local re - entry wavelets ; therefore , atrial fibrillation may be induced by several factors . among these : trauma from surgical dissection and manipulation , myocardial ischemic damage , an exaggerated local inflammatory response with or without pericarditis , an elevation in atrial pressure from post operative ventricular stunning a chemical stimulation due to postoperative support with catecholamine and other inotropic agents , a reflex sympathetic activation from volume loss , anemia or pain , parasympathetic activation , fever from atelectasis or infection , hypoglycaemia , metabolic and electrolyte imbalance , fluid overload , prolonged post operative electrical stimulation . cardiopulmonary by - pass related hemodynamic changes may induce intraoperative atrial ischemia that has been hypothesized to play a role in the development of poaf . .   reported at 6 months after surgery a significantly higher mortality in af patients compared with patients without af ( 9.4% vs 4.2% ) . .   showed in 6475 patients undergoing first isolated cabg that poaf was associated with at increased risk of death ( odds ratio = 1.5 ; 95% ci [ 1.3 , 1.8 ] ) . in this study , cumulative survival rate at 1 and 4 years was 87% and 74% in poaf patients versus 94% and 87% for non - af population . in more than 8500 isolated cabg patients a significantly increased risk of death was observed among those who developed postoperative af compared with those who did not ( odds ratio = 1.2 ; 95% ci , 1.1 to 1.3 ) . patients affected by postoperative af had an increased 1-year mortality ( 4.6% versus 2.0% ) , and af was confirmed to independently predict late mortality ( hazard ratio , 1.7 ; 95% ci [ 1.2 , 2.5 ] ) . results from present investigation do not support an association of poaf with an increase of late mortality in patients undergoing surgical revascularization . only one patient died at 2 years follow - up and not for cardiovascular cause . restoration of sinus rhythm in all patients during hospitalization and low recurrence rate may have significantly decreased the risk of mortality , in particular due to stroke or complications of oral anticoagulant treatment . decreased risk of ischemic damage in beating heart cabg initial favourable results [ 6 , 7 ] has not been confirmed by other authors [ 4 , 12 ] . siebert et al   during the postoperative intensive care unit stay reported a 9.8% rate of poaf in patients after cpb - cabg , 10.2% after op - cabg , and 21% after cabg combined with valve replacement . a recent meta - analysis suggested a decreased incidence of af in op - cabg although overall mortality was not affected . a not significant difference in the incidence of poaf between the two techniques was reported by several other studies [ 14 , 15 ] . two randomized , controlled trials and one large scale concurrent cohort study addressed the issue of beating - heart cabg . ascione et al   found a significantly lower rate of postoperative af in the op - cabg group ( 11.0% ) than in the cbp - pump cabg group ( 45.0% ) in 200 patients who had been randomized to undergo cabg either with or without cpb . a significant difference in postoperative af favouring the op - cabg group ( 21.2% ) compared to the on - pump cabg group ( 6.3% ) in contrast , in 281 patients randomized to cabg with or without cpb , van dijk et al   reported no difference in the rate of postoperative af . in patients undergoing emergency revascularization for acute coronary syndromes off - pump surgery vs cpb surgery was performed in patients with more severe clinical conditions : op - cabg patients were more frequently in cardiogenic shock , had an impaired renal function , a log euroscore > 20 or a left ventricular ejection fraction < 30% . overall survival and event rate , however , were similar at 5 five year follow - up . postoperative af occurred in 30.2% patients undergoing cpb - cabg vs 29.3% in op - cabg surgery while the incidence of stroke was two - fold in the former group ( 6.7 vs 2.5% , p < 0.035 ) . noteworthy the incidence of af was two folds in patients with cardiogenic shock undergoing cpb versus op surgery ( 62.5 vs 39.8% ) , with a significant increase in the number of stroke ( 33.3 vs 9.6% , p<0.009 ) . 0.901 ng / ml at icu admission has been identified as cut - off value for prediction of af in patients undergoing elective cabg . patients with serum tni   > of 0.901 ng / ml showed an 11.5 times increased risk for the onset of af after elective cabg . in present investigation no significant relation was found between tni serum concentration after surgery and the risk of af ( odds ratio = 0,96 - 95% ci [ 0,85 , 1,08 ] , p=0.17 ) . in our experience , the incidence of poaf resulted not significantly different in patients undergoing op - cabg in comparison to cpb - cabg . the two groups were comparable for severity of coronary disease , number of grafts performed and clinical presentation ( urgent versus elective surgery ) . however , mean age of patients undergoing op - cabg was on average 7 years older in comparison to patients treated with cpb - cabg . the present study was limited by its observational nature , by a relative short follow - up period ( 2 years ) , and by the low number of patients investigated . otherwise the short time of enrolment ( 1 year ) , the similar characteristics of the two groups , with the cited exception of age , and the limited number of operators decreased the risk of non homogeneity of the population under investigation . the low number of recurrences occurred , similarly to other studies , may be related to potential bias due to the reliance on self - reporting for follow - up cardiac rhythm data . although scheduled holter monitoring in our investigation did not reveal paroxysmal episodes of atrial fibrillation , only continuous monitoring systems may provide definitive data . similarly , the use of questionnaires and clinical examination during follow - up may not accurately identify paroxysmal episodes of af and may potentially have underestimated the incidence of the arrhythmia recurrences . despite the reported limitations , our study does not support the hypothesis that postoperative af is associated with an increased late mortality , rate of stroke or rehospitalization . restoration of sinus rhythm before hospital discharge may have significantly limited the negative prognostic effects of post operative atrial fibrillation . at present , the guidelines of the american college of chest physician state that op - cabg can not be recommended to decrease post operative af because of conflicting results resulted from randomized controlled trials or large - scale concurrent cohort studies .
introductionpostoperative atrial fibrillation after isolated coronary revascularization has been associated with increased morbidity and mortality . 
 aim of present investigation was to evaluate incidence of postoperative atrial fibrillation and its prognostic role in patients undergoing isolated coronary artery by - pass and disclose possible differences between off - pump and cardiopulmonary assisted revascularization.methodsprospective cohort study of 229 patients undergoing isolated coronary artery by - pass at a tertiary heart surgery centre . 
 off - pump treated patients were significantly older ( 70.5 vs 64.9 years , p<0.001 ) . 
 no other baseline differences were found . 
 patients who developed postoperative atrial fibrillation were followed up for an average period of 2 years.resultspost-operative occurred in 56/229 ( 24.1% after cardiopulmonary and 24.6% after off - pump coronary artery by - pass ) . left atrium diameter was the only independent predictive factor ( odds ratio = 1.15 , 95% confidence interval 1.02 - 1.30 , p<0.001 ) . 
 all patients with postoperative atrial fibrillation were treated and discharged in sinus rhythm , in 6/56 recurred , only in one persisted . 
 one patient died during follow up . 
 no stroke was recorded.conclusionsafter isolated surgical revascularization , atrial fibrillation occurred in 24% without differences related to operative technique . 
 recurrence of atrial fibrillation occurred in 6/56 patients ( 10.7% ) however only in 1 persisted . 
 early and late mortality did not show relation with post - operative atrial fibrillation probably due to immediate treatment with recovery of sinus rhythm before discharge .