Atrial fibrillation after minimally invasive coronary artery bypass grafting: A retrospective, matched study

Preoperative Antihypertensive Medication in Relation to Postoperative Atrial Fibrillation in Patients Undergoing Cardiac Surgery: A Meta-Analysis

Background. We undertake a systematic review and meta-analysis to evaluate the effect of preoperative hypertension and preoperative antihypertensive medication to postoperative atrial fibrillation (POAF) in patients undergoing cardiac surgery. Methods. We searched PubMed, Embase, and Cochrane Library (from inception to March 2016) for eligible studies. The outcomes were the effects of preoperative hypertension, preoperative calcium antagonists regimen, preoperative ACE inhibitors regimen, and preoperative beta blocking agents regimen with POAF. We calculated pooled risk ratios (OR) and 95% CIs using random- or fixed-effects models. Results. Twenty-five trials involving 130087 patients were listed. Meta-analysis showed that the number of preoperative hypertension patients in POAF group was significantly higher (P < 0.05), while we found that there are no significant differences between two groups in Asia patients by subgroup analysis, which is in contrast to other outcomes. Compared with the Non-POAF group, the number of patients who used calcium antagonists and ACE inhibitors preoperatively in POAF group was significantly higher (P < 0.05). And we found that there were no significant differences between two groups of preoperative beta blocking agents used (P = 0.08). Conclusions. Preoperative hypertension and preoperative antihypertensive medication in patients undergoing cardiac operations seem to be associated with higher risk of POAF.

Does Off-pump Coronary Artery Bypass Reduce the Prevalence ofAtrial Fibrillation?

INTRODUCTION

To examine whether or not off-pump CABG (Coronary Artery Bypass Reduce) reduces the incidence of AF after cardiac surgery.

METHODS

The study was carried out in 939 consecutive coronary artery disease patients with sinus rhythm from which 383 patients underwent off-pump CABG, and 556 patients were operated through on-pump CABG. All patients were monitored postoperatively during intensive care unit (ICU) stay. Then, the incidence and predictive risk factors of post operative AF (POAF) in two groups were determined and compared with each other.

RESULTS

Overall, the mean age of the patients was 56.0±12.8 years with 234 patients (24.9%) being older than 65 years. POAF developed in 38 patients (9.9%) of the off-pump and in 93 patients (16.7%) of the on-pump CABG. There was significant difference between two groups when considering the incidence of POAF (P=0.002). Among preoperative risk factors, age>65 years had a significant association with the incidence of AF in both groups. This study also showed that most of the POAF cases converted to sinus rhythm after treatment. Moreover, these finding demonstrated that conversion to sinus rhythm is significantly more probable in off-pump group (P=0.006).

CONCLUSION

A reduced prevalence of POAF could be observed in patients with off-pump as compared with on-pump techniques. Furthermore, conversion to sinus rhythm in off-pump group was significantly more probable than on-pump group.

Current state of surgical myocardial revascularization

Despite increasing competition from percutaneous interventions and other novel methods of non-surgical coronary revascularization, coronary artery bypass grafting (CABG) remains one of the most definitive and durable treatments for coronary artery disease, especially for those patients with extensive and diffuse disease. In recent years the CABG procedure itself has undergone innovation and evolution. This review article provides a brief historical perspective on the procedure, and examines the current state of modern variations including off-pump, limited-access, and robotic-assisted CABG.

Impact of high thoracic epidural anesthesia on incidence of perioperative atrial fibrillation in off-pump coronary bypass grafting: A prospective randomized study

OBJECTIVE

Atrial fibrillation is one of the most common complications in patients undergoing coronary artery bypass grafting. The goal of this study was to investigate the impact of high thoracic epidural anesthesia on reduction of perioperative arrhythmia in patients undergoing off-pump coronary artery bypass grafting.

METHODS

We prospectively randomized 132 patients undergoing elective off-pump coronary bypass grafting using either general anesthesia (GA) (n = 66) or combined general and high thoracic epidural anesthesia (GA+TEA) (n = 66). Incidence of perioperative arrhythmias such as atrial fibrillation, serum epinephrine levels, heart rate variability, and hemodynamic parameters were compared between groups.

RESULTS

The incidence of perioperative dysarrhythmias was significantly lower (P < .01) in the GA+TEA group (3%) than in the GA group (23.7%). Intraoperative sinus bradycardia occurred in 91% of the patients in the GA+TEA group versus 5.3% in the GA group. After induction of anesthesia, the mean systolic arterial pressure decreased significantly from 128 +/- 5 to 92 +/- 4 mm Hg and the heart rate from 74 +/- 9 to 52 +/- 8 beats . min(-1) in the GA+TEA group, whereas in the GA group no significant hemodynamic changes were observed (P < .001). Serum epinephrine levels were significantly lower in the GA+TEA group (69 +/- 11 to 35 +/- 7 ng/dL) than in the GA group (72 +/- 9 to 70 +/- 9 ng/dL).

CONCLUSIONS

In our study cohort, high thoracic epidural anesthesia in combination with general anesthesia reduced significantly the incidence of perioperative arrhythmias such as atrial fibrillation. Furthermore, we observed a significant reduction of epinephrine serum levels in this patient group. The results of this study support a combination of general anesthesia with thoracic epidural anesthesia as a multidisciplinary approach, which may lead to a better patient outcome, improvement of early analgesia, and reduction of perioperative complications in off-pump coronary artery bypass procedures. The potential risks of thoracic epidural anesthesia during off-pump coronary artery bypass procedures should not be underestimated.

Intravenous and oral amiodarone for the prevention of postoperative atrial fibrillation in patients undergoing off-pump coronary artery bypass surgery

BACKGROUND

Atrial fibrillation is still a frequent complication that increases morbidity after coronary artery bypass grafting. This prospective randomized study is designed to define efficacy of postoperative amiodarone prophylaxis in preventing atrial fibrillation after off-pump coronary artery bypass grafting.

METHODS

One hundred forty-four patients who underwent elective off-pump coronary artery bypass grafting were enrolled for the study. Seventy-six patients (amiodarone group) received 5 mg/kg loading amiodarone infusion in the first postoperative hour, followed by 10 mg/kg for the first 24 hours. After 24 hours, patients received 600 mg/day amiodarone orally for 7 days and 200 mg/day until the end of the postoperative first month. Sixty-eight patients received placebo (control group).

RESULTS

Preoperative characteristics and operative variables of the patients were similar in both groups. Incidence of new-onset atrial fibrillation and maximal ventricular rate response were recorded. The incidence of new-onset atrial fibrillation (11.8% versus 26.5%) (P = .025) and maximal ventricular rate response (109 +/- 13.8 beats/min versus 124.5 +/- 13.9 beats/min) (P = .011) were significantly lower in the amiodarone group. Duration of atrial fibrillation was 17.5 +/- 8.1 hours for the amiodarone group compared with 32.7 +/- 12 hours for the control group (P = .002).

CONCLUSION

Postoperative intravenous amiodarone prophylaxis followed by oral amiodarone significantly reduces the incidence of atrial fibrillation after off-pump coronary artery bypass grafting and the ventricular rate during atrial fibrillation.

Preoperative beta-blocker use reduces atrial fibrillation in off-pump coronary bypass surgery

BACKGROUND

Atrial fibrillation (AF) after coronary artery bypass graft surgery constitutes the most common sustained arrhythmia and results in many complications. The purpose of this study was to assess the effects of prophylactic use of beta-blockers against atrial fibrillation in off-pump surgery patients in the early postoperative period.

METHODS

From 2002 to 2005, 78 patients were enrolled and 41 patients received 50 mg metoprolol succinate daily, which was initiated minimum four days before surgery. Preoperative beta-blocking therapy was continued until the morning of surgery. Thirty-seven patients were free of beta-blocker therapy. Esmolol was used within same range of doses in both groups during operations. Both groups received metoprolol succinate following operations. The frequency of AF occurrence was analysed from the operation time to the sixth postoperative day.

RESULTS

Sixteen patients developed AF with an overall incidence of 22.5%. Four patients from the study group and three patients from the control group were excluded from the study because of transfer to on-pump surgery. There was no difference with regard to the number of grafts carried out, duration of operations and ventilation, intensive care unit stay and inotropic need among groups. Length of hospital stay did not differ among groups either. There was a higher incidence of postoperative AF in patients without beta-blocker prophylaxis (11.7-32.4% P=0.049).

CONCLUSION

Low-dose postoperative beta-adrenergic blockade is valuable for patients who receive these medications before off-pump coronary artery bypass grafting procedures and may be beneficial against AF in all patients.

Atrial fibrillation after off-pump coronary artery surgery: a prospective, matched study

The effect of cardiopulmonary bypass and myocardial ischaemia on the occurrence of atrial fibrillation (AF) after coronary artery bypass graft (CABG) was studied in 136 patients undergoing off-pump CABG who were matched for age and number of distal anastomoses with 136 patients undergoing on-pump CABG. Possible risk factors for post-operative new-onset AF were recorded. AF occurred in 64 (24%) of the 267 patients for whom data could be analysed. AF occurred in 29 patients (22%) in the off-pump group versus 35 (26%) in the on-pump group, but this difference was not statistically significant. On univariate analysis, age and length of hospital stay were significant risk factors for the occurrence of AF. In a multivariate analysis that included operative technique, age was found to be the only significant risk factor. In conclusion, the occurrence of AF after CABG does not depend on the type of operation.

Atrial fibrillation following cardiac surgery: a retrospective cohort series

Atrial fibrillation (AF) is a common postoperative complication of cardiac surgery, yet the prevention and treatment of postoperative AF remains controversial and varies among practitioners. The purpose of this study was to document the incidence and time of onset of postoperative AF in a cardiac surgical cohort, examine risk factors implicated in the occurrence of postoperative AF, and assess effectiveness of current treatment strategies implemented for postoperative AF. A retrospective health record review was conducted on 1078 adults following cardiac surgery. Data on demographic, preoperative, perioperative, and postoperative risk factors for postoperative AF, documented episodes of AF, and clinical outcomes were recorded. Overall incidence of postoperative AF was 39.6%: 57.6% after cardiac valve surgery, 69.3% after combined coronary artery bypass graft and valve surgery, and 33% after bypass graft surgery alone. The peak onset of postoperative AF occurred on the second postoperative day. Advancing age, history of AF, combined cardiac valve and coronary artery bypass graft surgery, and high Mg+2 levels on the third postoperative day were significant predictors of postoperative AF in this cohort. Length of hospitalization increased with the presence of postoperative AF. Findings corroborate that multiple factors play a role in the development of AF following cardiac surgery.

Atrial arrhythmias after cardiac surgery in patients with diabetes mellitus

BACKGROUND

Postoperative atrial fibrillation (AF) is a common complication of cardiac surgery and has been associated with increased incidence of other complications and increased hospital length of stay (LOS). Prevention of AF is a reasonable clinical goal, and, consequently, many randomized trials have evaluated the effectiveness of pharmacological and non-pharmacological interventions for prevention of AF. To better understand the role of various prophylactic therapies against postoperative AF, a systematic review of evidence from randomized trials was performed.

METHODS

MEDLINE search of English-language reports published between 1966 and July 2005 and a search of references of relevant papers were conducted. Clinical studies on AF after cardiac surgery were selected for this analysis. Relevant clinical information was extracted from selected articles.

RESULTS

Postoperative AF is associated with increased morbidity and mortality and longer, more expensive hospital stays. Prophylactic use of beta-adrenergic blockers reduces the incidence of postoperative AF and should be administered before and after cardiac surgery to all patients without contraindication. Prophylactic amiodarone and atrial overdrive pacing should be considered in patients at high risk for postoperative AF (for example, patients with previous AF or mitral valve surgery). For patients who develop AF after cardiac surgery, a strategy of rhythm management or rate management should be selected. For patients who are hemodynamically unstable or highly symptomatic or who have a contraindication to anticoagulation, rhythm management with electrical cardioversion, amiodarone, or both is preferred. Treatment of the remaining patients should focus on rate control because most will spontaneously revert to sinus rhythm within 6 weeks after discharge. All patients with AF persisting for more than 24 to 48 hours and without contraindication should receive anticoagulation.

CONCLUSIONS

AF frequently complicates cardiac surgery. Many cases can be prevented with appropriate prophylactic therapy. A strategy of rhythm management for symptomatic patients and rate management for all other patients usually results in reversion to sinus rhythm within 6 weeks of discharge.

Intraoperative Interventions

A comprehensive evidence review was conducted of the medical literature regarding the relationship between intraoperative interventions and the incidence of postoperative atrial arrhythmias, including, most commonly, atrial fibrillation (AF). Fifteen randomized, controlled studies and one large-scale concurrent cohort study were identified that reported on the following issues: systemic temperature during surgery (one report); "beating heart" surgery vs conventional bypass surgery (three reports); type of myocardial protection (five reports); the use of adjunctive posterior pericardiotomy (one report); the use of thoracic epidural anesthesia (TEA) [two reports]; the use of glucose-insulin-potassium (GIK) solutions (two reports); and the use of heparin-coated circuits for cardiopulmonary bypass (CPB) [two reports]. Based on a systematic review of the reported data and an analysis of the quality of the reported data, we recommend the following: (1) that mild hypothermia, rather than moderate hypothermia, may be effective in reducing the frequency of postoperative AF; (2) the use of posterior pericardiotomy may be a useful adjunct to reduce the frequency of postoperative AF; and (3) the use of heparin-coated CPB circuits is associated with less postoperative AF. Because of conflicting or inadequate data, we cannot conclude that the frequency of postoperative AF is affected by (1) the use of beating-heart techniques, (2) the type of myocardial protection strategy used, (3) the use of TEA, or (4) the use of GIK solutions perioperatively.

Predictors of atrial fibrillation after off-pump coronary artery bypass graft surgery

OBJECTIVE

Atrial fibrillation is the most common complication after coronary artery bypass graft surgery. This arrhythmia may lead to hemodynamic compromise, prolonged hospitalization, and increased risk for cerebral thromboembolism. Older age is the only variable consistently associated with the development of postoperative atrial fibrillation; however, no strong predictive model exists. The purpose of this study was to identify perioperative characteristics associated with new-onset atrial fibrillation in patients undergoing off-pump coronary artery bypass grafting.

DESIGN

Prospective, observational.

SETTING

University tertiary care hospital.

PARTICIPANTS

One hundred sixty consecutive patients undergoing off-pump coronary artery bypass grafting.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Incidence of postoperative atrial fibrillation was the major outcome. Atrial fibrillation occurred in 33 patients (20.6%). Multivariate analysis identified reintervention (odds ratio 26.8), revascularization of the ramus medianus (odds ratio 3.9), and age (odds ratio 1.069 per year) as the only independent predictors of postoperative atrial fibrillation. All patients were in sinus rhythm at hospital discharge. One hospital death was noted.

CONCLUSIONS

Despite the less invasive approach, the incidence of postoperative atrial fibrillation is high after off-pump coronary artery bypass grafting. Older age, grafting of the ramus medianus, and a redo operation were predictors of new-onset postoperative atrial fibrillation. It is possible that left atrial stretching with heart dislocation during revascularization of the lateral wall could lead to postoperative atrial fibrillation.

Atrial fibrillation and cardiac surgery

PURPOSE OF REVIEW

To discuss the pathophysiology, risk factors, and treatments for atrial fibrillation occurring after cardiac surgery.

RECENT FINDINGS

Atrial fibrillation occurs frequently after cardiac surgery and it may lead to patient morbidity. Many variables have been suggested to be associated with this arrhythmia, but only advanced patient age can consistently identify risk for this complication. Immediate electrical cardioversion is indicated when the arrhythmia leads to hemodynamic instability or myocardial ischemia. Otherwise treatment is aimed at heart rate control, elective cardioversion with drugs or electrical means, and anticoagulation when the arrhythmia persists. Multiple investigations have evaluated methods for preventing postoperative atrial fibrillation, but only beta-adrenergic receptor blocking drugs have been consistently shown to be effective, and then not in all patients. Surgical treatments are increasingly being considered as a therapeutic means for ameliorating chronic atrial fibrillation. The use of these procedures has been simplified with the development of devices that can generate linear scars in the atrium and around the pulmonary vein orifices. These simplifications will allow for broader application of these techniques to patients undergoing other cardiac surgery (e.g. mitral valvular surgery).

SUMMARY

Atrial fibrillation is one of the most common complications of cardiac surgery. There are three major aims for treating atrial fibrillation: conversion to sinus rhythm, heart rate control, and anticoagulation. Only beta-blockers can be recommended for prophylaxis against postoperative atrial fibrillation. Further refinements in surgical treatments for atrial fibrillation may allow for wider applications of this therapy with lower rates of complications.

Fibrillation in patients subjected to coronary artery bypass grafting

OBJECTIVE

Atrial fibrillation is the most frequently encountered postoperative arrhythmic complication after coronary artery bypass grafting. Ischemic preconditioning has proved a potent endogenous factor in suppressing ischemia-reperfusion-induced arrhythmias. The protective effect of ischemic preconditioning on atrial fibrillation after coronary artery bypass grafting has not been studied. The purpose of the present study was to investigate whether ischemic preconditioning had an effect on postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting.

METHODS

Eighty-five patients undergoing coronary artery bypass grafting were randomized into ischemic preconditioning and control groups. Holter data from 24-hour electrocardiography were collected 1 day before the operation to the second postoperative day. Atrial fibrillation was registered as positive if any atrial fibrillation event occurred.

RESULTS

The overall incidence of postoperative atrial fibrillation and sustained atrial fibrillation was 34.1% and 27.1%, respectively. The occurrence of atrial fibrillation was significantly lower in the ischemic preconditioning group (21.4% in patients undergoing ischemic preconditioning and 46.5% in control subjects, P =.015). Preoperative recent unstable angina did not influence the incidence of atrial fibrillation. Patients with atrial fibrillation had longer intensive care unit stays and compromised postoperative hemodynamic outcomes. Binary logistic regression analysis showed that ischemic preconditioning, preoperative mean heart rate, and postoperative pulmonary capillary wedge pressure were the independent predictors of atrial fibrillation.

CONCLUSIONS

Postcoronary artery bypass grafting atrial fibrillation is associated with more complicated postoperative outcome. Higher preoperative heart rate and postoperative pulmonary capillary wedge pressure were the independent predictors of atrial fibrillation. Recent unstable angina is not related to the occurrence of postcoronary artery bypass grafting atrial fibrillation. Ischemic preconditioning significantly suppresses postcoronary artery bypass grafting atrial fibrillation, suggesting that ischemic preconditioning can be used as an effective prophylactic method for postoperative atrial fibrillation.

Off-pump coronary artery bypass graft surgery: the incidence of postoperative atrial fibrillation

Atrial fibrillation (AF) occurs in one quarter to one third of patients after coronary artery bypass graft surgery (CABG). Conventional CABG uses cardiopulmonary bypass, a process that is itself associated with a systemic vascular inflammatory response that contributes to postoperative morbidity. The avoidance of cardiopulmonary bypass is associated with a significant reduction in the inflammatory response and in the release of markers of myocardial necrosis when compared with conventional CABG. There is speculation that off-pump CABG may reduce the incidence of postoperative AF through reduced trauma, ischaemia, and inflammation. Current data, however, do not emphatically answer the question of whether the incidence of post-CABG AF is reduced by off-pump surgery. The evidence from both observational and randomised studies is conflicting and many studies have weaknesses in design, conduct, or interpretation. It remains an attractive hypothesis that postoperative AF is reduced by off-pump CABG but more robust data are required.

The -174G/C interleukin-6 polymorphism influences postoperative interleukin-6 levels and postoperative atrial fibrillation. Is atrial fibrillation an inflammatory complication?

BACKGROUND

It has been suggested that inflammation can have a role in the development of atrial arrhythmias after cardiac surgery and that a genetic predisposition to develop postoperative complications exists. This study was conceived to verify if a potential genetic modulator of the systemic inflammatory reaction to cardiopulmonary bypass (the -174 G/C polymorphism of the promoter of the Interleukin-6 gene) has a role in the pathogenesis of postoperative atrial fibrillation (AF). Patients and Results- In 110 primary isolated coronary artery bypass patients the -174G/C Interleukin-6 promoter gene variant was determined. Interleukin-6, fibrinogen and C-reactive protein plasma levels were determined preoperatively, 24, 48, and 72 hours after surgery and at discharge. Heart rate and rhythm were continuously monitored for the first 36 to 48 hours; daily 12-lead electrocardiograms were performed thereafter until discharge. GG, CT, and CC genotypes were found in 62, 38, and 10 patients, respectively. Multivariate analysis (which included genotype, age, sex, and classical risk factors for AF) identified the GG genotype as the only independent predictor of postoperative AF. The latter occurred in 33.9% of GG versus 10.4% of non-GG patients (hazard ratio 3.25, 95%CI 1.23 to 8.62). AF patients had higher blood levels of Interleukin-6 and fibrinogen after surgery (P<0.001 for difference between the area under the curve).

CONCLUSIONS

The -174G/C Interleukin-6 promoter gene variant appears to modulate the inflammatory response to surgery and to influence the development of postoperative AF. These data suggest an inflammatory component of postoperative atrial arrhythmias and a genetic predisposition to this complication.

Arrhythmias in off-pump coronary artery bypass grafting and the antiarrhythmic effect of regional ischemic preconditioning

OBJECTIVE

The authors sought to establish whether regional ischemic preconditioning (IP) reduces ischemic reperfusion arrhythmias in patients who undergo off-pump coronary artery bypass grafting (OPCAB).

DESIGN

A controlled, randomized, prospective study.

SETTING

A university hospital.

PARTICIPANTS

Thirty-two patients with left anterior descending coronary artery (LAD) or 2-vessel heart disease (including LAD) who were to undergo OPCAB were randomized into an IP and a control group.

INTERVENTIONS

IP was induced by occluding the LAD twice for a 2-minute period followed by 3-minute LAD reperfusion before bypass grafting of the first coronary vessel.

MEASUREMENTS AND MAIN RESULTS

Twenty-four-hour electrocardiography was recorded from the preoperative day to the second postoperative day. The heart rate (HR) was significantly elevated after surgery. Supraventricular extrasystole (SVES) events were similar before and after surgery. The incidence of patients with ventricular extrasystole (VES), supraventricular tachycardia (SVT), atrial fibrillation (AF), and ventricular tachycardia (VT) was significantly increased after the operation. Ventricular arrhythmias occurred mostly during anastomosis and the early reperfusion period and recovered 2 hours after reperfusion. Supraventricular tachyarrhythmias were mostly encountered 24 hours after reperfusion. IP significantly suppressed HR elevation, SVT, and VT after surgery. SVES, VES, and AF episodes were similar between the groups.

CONCLUSIONS

Arrhythmia was a common phenomenon during and after an OPCAB procedure. The present IP protocol significantly suppressed HR elevation, the episodes of SVT, and the incidence of VT after surgery.

Off-pump coronary artery bypass grafting does not decrease the incidence of atrial fibrillation

BACKGROUND

Postoperative atrial fibrillation remains a significant source of morbidity after coronary artery bypass grafting. We reviewed the data on 2,569 patients to determine if the absence of cardiopulmonary bypass resulted in a lower incidence of atrial fibrillation.

METHODS

All patients undergoing coronary artery bypass grafting without cardiopulmonary bypass from January 1, 1997 through June 30, 2001 were evaluated for postoperative atrial fibrillation. The data of 252 patients with no cardiopulmonary bypass (group 1) were reviewed and compared with three other patient groups. Group 2 consisted of 1,470 patients using cardiopulmonary bypass during the same study period. Group 3 consisted of 841 patients with a similar number of grafts as the study group but using cardiopulmonary bypass. Group 4 consisted of historical data for 847 patients operated on using cardiopulmonary bypass collected from January 1995 through December 1996. Prophylactic beta-blockade was instituted in January 1997. Groups 1 to 3 received this treatment, but group 4 did not.

RESULTS

Group 1 had an incidence of atrial fibrillation of 8.8%. Groups 2, 3, and 4 had incidences of atrial fibrillation of 11.6%, 9.4%, and 28.0%, respectively. When compared with group 1, the incidence of atrial fibrillation in group 4 was statistically different (p <. 0001).

CONCLUSIONS

Avoiding cardiopulmonary bypass did not aid the reduction of atrial fibrillation at our institution.

Off-pump coronary artery bypass with complete avoidance of aortic manipulation

BACKGROUND

Off-pump coronary artery bypass (OPCAB) with complete avoidance of aortic manipulation may further reduce perioperative morbidity in addition to the benefits achieved by avoiding cardiopulmonary bypass and cardioplegic arrest.

METHODS

We prospectively analyzed 222 consecutive patients with multivessel disease who underwent OPCAB without aortic manipulation (group I), and compared them with 123 consecutive patients who underwent OPCAB using additional free arterial or saphenous vein grafts that were anastomosed on the ascending aorta (group II) and 76 consecutive patients who underwent on-pump conventional coronary artery bypass grafting (group III).

RESULTS

No significant differences were noted in operative mortalities among the three groups (2/222, 3/123, and 2/76 in groups I, II, and III, respectively; p = NS). Fewer distal anastomoses were done in group I compared with groups II and III (3.2 +/- 0.9, 3.5 +/- 0.8, and 3.7 +/- 0.9 in groups I, II, and III, respectively; p < 0.001). No differences were noted in the incidences of postoperative morbidities such as mediastinitis, pulmonary complication, and reoperation for bleeding. The incidences of stroke, atrial fibrillation, and acute renal failure were significantly lower in group I than in group III (p < 0.05), although there were no significant differences between groups II and III. The incidence of perioperative myocardial infarction was significantly lower in group I than in groups II and III (p < 0.05), although there was no significant difference between groups II and III.

CONCLUSIONS

Our results demonstrate that OPCAB with complete avoidance of aortic manipulation may further reduce the incidence of perioperative morbidities such as stroke, atrial fibrillation, acute renal failure, and perioperative myocardial infarction.

Atrial fibrillation and minimally invasive coronary artery bypass grafting: risk factor analysis

Atrial fibrillation (AF) is a frequent arrhythmia after conventional coronary artery bypass grafting. With the advent of minimally invasive technique for left internal mammary artery-left anterior descending coronary artery (LIMA-LAD) grafting, we analyzed the incidence and the risk factors of postoperative AF in this patient population. This prospective study involves all patients undergoing isolated LIMA-LAD grafting with minimally invasive technique between January 1994 and June 2000. Twenty-four possible risk factors for postoperative AF were entered into univariate and multivariate logistic regression analyses. Postoperative AF occurred in 21 of the 90 patients (23.3%) analyzed. Double- or triple-vessel disease was present in 12/90 patients (13.3%). On univariate analysis, right coronary artery disease (p <0.01), age (p = 0.01), and diabetes (p = 0.04) were found to be risk factors for AF. On multivariate analysis, right coronary artery disease was identified as the sole significant risk factor (p = 0.02). In this patient population, the incidence of AF after minimally invasive coronary artery bypass is in the range of that reported for conventional coronary artery bypass grafting. Right coronary artery disease was found to be an independent predictor, and this may be related to the fact that in this patient population the diseased right coronary artery was not revascularized at the time of the surgical procedure. For the same reason, this risk factor may find a broader application to noncardiac thoracic surgery.

Predictors and impact of atrial fibrillation after isolated coronary artery bypass grafting

OBJECTIVE

Although an extensive number of studies have attempted to identify predictors of new-onset atrial fibrillation (AFIB) after coronary artery bypass grafting (CABG), a strong predictive model does not exist. Prior studies have included patients recruited from multiple centers with variant AFIB prevalence rates and those who underwent CABG in combination with other surgical procedures. Also, most studies have focused on pre- and perioperative characteristics, with less attention given to the initial postoperative period. The purpose of this study was to comprehensively examine pre-, peri-, and postoperative characteristics that might predict new-onset AFIB in a large sample of patients undergoing isolated CABG in a single medical center, utilizing data readily available to clinicians in electronic data repositories. In addition, length of stay and selected postoperative complications and disposition were compared in patients with AFIB and no AFIB.

DESIGN

Retrospective, comparative survey.

SETTING

University-affiliated tertiary care hospital.

PATIENTS

Patients with new-onset AFIB who underwent isolated standard CABG or minimally invasive direct vision coronary artery bypass were identified from an electronic clinical data repository.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The prevalence of AFIB in the total sample (n = 814) was 31.9%. Predictors of AFIB included age (p =.0004), number of vessels bypassed (p =.013), vessel location (diagonal [p <.003] or posterior descending artery [p <.001]), and net fluid balance on the operative day (p =.015). Forward stepwise regression analysis produced a model that correctly predicted AFIB in only 24% of cases, with age (14%) and body surface area (9%) providing the most prediction. The incidence of embolic stroke was higher in AFIB (n = 8) vs. no AFIB (n = 4) patients, but stroke preceded AFIB onset in seven of eight cases. Subjects with AFIB had a longer stay (p =.0004), more intensive care unit readmissions (p =.0004), and required more assistance at hospital discharge (p =.017).

CONCLUSIONS

Despite attempts to examine comprehensively predictors of new-onset AFIB, we were unable to identify a robust predictive model. Our findings, in combination with prior work, imply that it may not be feasible to predict the development of new-onset AFIB after CABG using data readily available to the bedside clinician. In this sample, stroke was uncommon and, when it occurred, preceded AFIB in all but one case. As anticipated, AFIB increased length of stay, and patients with this complication required more assistance at discharge.

Off-Pump Coronary Artery Bypass Surgery: Revival of an Old Technique

The ability to perform surgical procedures on the heart was one of the greatest accomplishments of the 20th century. What was once considered an impossible task has become a routine in daily clinical activity. The in troduction of extracorporeal circulation and myocardial protection strategies opened the doors to what was considered by most an insurmountable barrier— unhin dered access to the coronary circulation and intracar diac structures. In the United States, approximately 85% of coronary artery bypass graft procedures are performed with the use of cardiopulmonary bypass (CPB). CPB was and remains the gold standard for this type of cardiac surgical intervention. Over the years, investigators have struggled to find ways of lessening or eliminating the adverse physiologic effects of CPB. These efforts have focused on pharmacologic interven tion, monitoring procedures, blood gas management, and temperature management. Another way of avoid ing these effects is inherently obvious — eliminate the main source of the problem.

Magnesium infusion dramatically decreases the incidence of atrial fibrillation after coronary artery bypass grafting

BACKGROUND

Atrial fibrillation (AF) is one of the most common complications of cardiac surgery. Magnesium, like several other pharmacologic agents, has been used in the prophylaxis of postoperative AF with varying degrees of success. However, the dose and the timing of magnesium prophylaxis need to be clarified. The purpose of this study was to assess the effect of intermittent magnesium infusion on postoperative AF.

METHODS

A total of 200 consecutive patients who had elective, isolated, first-time coronary artery bypass grafting were prospectively randomized to two groups. Patients in the magnesium group (n = 100) received 6 mmol MgSO4 infusion in 100 mL 0.9% NaCl solution (25 mL/h) the day before surgery, just after cardiopulmonary bypass, and once daily for 4 days after surgery. Patients in the control group (n = 100) received only 100 mL 0.9% NaCl solution (25 mL/h) at the same time points.

RESULTS

Postoperative AF occurred in 2 (2%) patients in the magnesium group and in 21 (21%) patients in the control group (p < 0.001). Atrial fibrillation started, on average, 49.4 +/- 16.8 hours postoperatively. The postoperative length of hospital stay was not significantly different in patients with AF (7.4 +/- 8.0 days) compared with patients without AF (5.4 +/- 1.1 days; p = 0.236).

CONCLUSIONS

The use of magnesium in the preoperative and early postoperative periods is highly effective in reducing the incidence of AF after coronary artery bypass grafting.

Systemic inflammation and cardiac surgery: an update

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with the development of a systemic inflammatory response that can often lead to dysfunction of major organs. The systemic inflammation can be assessed intra- and postoperatively by measuring concentrations of inflammatory mediators in plasma and tissues. These concentrations, however, do not always correlate with the degree of observed organ dysfunction. Various strategies have been used to reduce inflammatory phenomena in patients undergoing CPB. Cardiac surgery without CPB has been performed increasingly with satisfactory results over the past few years. Attenuation of systemic inflammation and improved outcome in high risk patients are potential benefits of this technique. The emergence and expanding performance of cardiac surgical procedures without the use of CPB has given us an excellent tool to investigate the relative importance of CPB as a cause of systemic inflammation. Aprotinin is a protease inhibitor which is used in cardiac surgical patients for its haemostatic effects. Aprotinin has anti-inflammatory properties, the nature of which have not been completely clarified. This article presents a summary of the published literature investigating inflammatory response and organ dysfunction in patients who have cardiac surgery without CPB. It also presents an overview of recent data on the anti-inflammatory action mechanisms of aprotinin.

Atrial fibrillation: prevalence after minimally invasive direct and standard coronary artery bypass

BACKGROUND

This study identified and compared the prevalence of new-onset atrial fibrillation (AFIB) following standard coronary artery bypass grafting (SCABG) with cardiopulmonary bypass (CPB) and minimally invasive direct vision coronary artery bypass grafting (MIDCAB) without CPB. A further comparison was made between AFIB prevalence in SCABG and MIDCAB subjects with two or fewer bypasses.

METHODS

This is a retrospective, comparative survey. Patients with new-onset AFIB who underwent SCABG or MIDCAB alone were identified electronically using a triangulated method (International Classification of Diseases, 9th revision, Clinical Modification [ICD-9 CM] code; clinical database word search; and pharmacy database drug search).

RESULTS

The total sample (n = 814; 94 MIDCAB, 720 SCABG) exhibited a trend toward lower AFIB prevalence in MIDCAB (23.4%) versus SCABG (33.1%) subjects (p = 0.059). AFIB prevalence in the SCABG subset with two or less vessel bypasses (n = 98; n = 18 single vessel, n = 80 double vessels) and MIDCAB subjects (n = 94; n = 90 single vessels, n = 4 double vessels) was almost identical (SCABG subset 24.5% versus MIDCAB 23.4%, p = 0.860). Slightly more than half (56.9%) of new-onset AFIB subjects were identified by ICD-9 CM codes, with the remainder by word search (37.7%) or procainamide query (5.4%).

CONCLUSIONS

In this sample, the number of vessels bypassed seemed to have a greater influence on AFIB prevalence than the application of CPB or the surgical approach. Retrospective identification of AFIB cases by ICD-9 CM code grossly underestimated AFIB prevalence.

Did the introduction of a minimally invasive technique change the incidence of atrial fibrillation after single internal thoracic artery-left anterior descending artery grafting?

OBJECTIVE

Atrial fibrillation after coronary artery bypass operations remains frequent and increases morbidity, as well as resource use. Its cause remains unclear. The introduction of a minimally invasive technique provides an opportunity to evaluate the effect of intraoperative factors, such as cardiopulmonary bypass, global myocardial ischemia, and myocardial protection technique, on the occurrence of this arrhythmia.

METHODS

All the patients undergoing isolated left internal thoracic artery-left anterior descending artery grafting between January 1994 and December 1999 were reviewed. Twenty possible risk factors for postoperative atrial fibrillation, including the choice of operative technique--minimally invasive technique was introduced in January 1997--were entered into univariate and multivariable logistic regression analysis.

RESULTS

Postoperative atrial fibrillation occurred in 36 (20%) of 183 patients. On univariate analysis, age (P <.001) and a history of supraventricular arrhythmia (P <.001) were found to be risk factors. In particular, 15 (22%) of 69 patients operated on with the minimally invasive technique had postoperative atrial fibrillation versus 21 (18%) of 114 in the standard group (P =.58). On multivariable analysis, including the operative technique, the same variables (P =.001 and.01, respectively) were identified as independent risk factors.

CONCLUSIONS

The introduction of a minimally invasive technique for coronary artery bypass operations did not reduce the occurrence of postoperative atrial fibrillation in this study population. This suggests that prophylactic measures to reduce this arrhythmia should be focused on factors unrelated to cardiopulmonary bypass or myocardial preservation technique.

Reduced incidence of atrial fibrillation with minimally invasive direct coronary artery bypass

BACKGROUND

Atrial fibrillation (AF) is a frequent complication after coronary artery bypass graft (CABG) surgery. The purpose of this study was to determine the incidence of postoperative AF after minimally invasive direct coronary artery bypass (MIDCAB) in comparison with CABG.

METHODS

Between November 1995 and May 1997, 96 MIDCAB procedures were performed. During the same period, 42 patients underwent traditional single CABG using the left internal mammary artery graft (S-CABG). The incidence of in-hospital AF, defined as a sustained episode requiring treatment, was compared between the two groups.

RESULTS

There was no difference in age, ejection fraction, or preoperative risk score between the groups. The use of beta-blockers before or after surgery was not different. The incidence of postoperative AF in the first 6 weeks after surgery was 4% (4 of 96) for MIDCAB and 28% (12 of 42) for S-CABG (p = 0.003). Patients with postoperati

Atrial fibrillation after minimally invasive direct coronary artery bypass surgery

OBJECTIVES

The study compared the adjusted risk for developing atrial fibrillation (AF) after minimally invasive direct coronary artery bypass surgery (MIDCAB) and coronary artery bypass graft surgery (CABG).

BACKGROUND

Atrial fibrillation results in increased morbidity and delays hospital discharge after CABG. Recently, MIDCAB has been explored as an alternative to CABG. Because of differences in surgical approach between the two procedures, the incidence of AF may differ.

METHODS

Randomly selected patients undergoing CABG and MIDCAB were examined. Baseline variables and postoperative course were recorded through review of medical record data.

RESULTS

The MIDCAB patients were younger than CABG patients (64+/-12 vs. 67+/-10, p<0.04) and had less extensive coronary artery disease (53% of MIDCAB vs. 3% of CABG had single-vessel disease, while 15% of MIDCAB vs. 69% of CABG had triple-vessel disease, p<0.001 for overall group comparisons). No other differences in clinical or treatment data were noted. Postoperative AF occurred less often after MIDCAB (23% vs. 39%, p = 0.02). Other significant factors associated with postoperative AF included age (p = 0.0024), prior AF (p = 0.0007), left main disease (p = 0.01), number of vessels bypassed (p = 0.009), absence of postoperative beta-blocker therapy (p = 0.0001), and a serious postoperative complication (p = 0.0018). Because of differences between CABG and MIDCAB patients, multivariate logistic analysis was performed to determine independent predictors of postoperative AF. The type of surgery (CABG vs. MIDCAB) was no longer a significant predictor of postoperative AF (estimated relative risk for AF in CABG vs. MIDCAB patients: 1.57, 95% confidence interval (0.82-2.52).

CONCLUSIONS

Although AF appears to be less common after MIDCAB than after CABG, the lower incidence is due to different clinical characteristics of patients undergoing these procedures.

Postoperative atrial tachyarrhythmias in patients undergoing coronary artery bypass graft surgery without cardiopulmonary bypass: a role for intraoperative magnesium supplementation

OBJECTIVE

To determine if intraoperative magnesium supplementation would be associated with a reduction in postoperative atrial tachyarrhythmias (POAT) in patients undergoing coronary artery bypass grafting (CABG) surgery without cardiopulmonary bypass (off-pump CABG surgery).

DESIGN

Retrospective study.

SETTING

University Medical Center.

PARTICIPANTS

Patients who had undergone off-pump CABG surgery (n = 124).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The charts of 124 patients who had undergone off-pump CABG surgery (64 by anterior thoracotomy and 60 by median sternotomy) were retrospectively reviewed. Demographic data and perioperative care were recorded and compared among patients who did and did not experience POAT and among patients who did and did not receive intraoperative magnesium supplementation. Logistic regression analysis was used to assess the association between magnesium supplementation and incidence of POAT, controlling for other covariables. Of the 124 patients, 16 had a prior history of atrial or ventricular arrhythmias and/or were receiving antiarrhythmic medications. Medical records of the remaining 108 patients were reviewed. Twenty-four patients (22%) had POAT. Forty-two patients (39%) received intraoperative magnesium. In patients receiving intraoperative magnesium, the incidence of POAT was significantly decreased (12% v 29%; p = 0.03). In these patients, initial postoperative serum magnesium was significantly higher (2.37 mEq/L v 1.86 mEq/L; p < 0.01). In patients not receiving intraoperative magnesium, 35% had hypomagnesemia (serum magnesium < 1.8 mEq/L) compared with 9% of patients receiving magnesium (p < 0.01). Patients who received intraoperative magnesium and beta-adrenergic blockers had a lower incidence of POAT (5%) than patients who received only one (19%) or neither (33%) (p < 0.05).

CONCLUSIONS

Intraoperative magnesium supplementation is associated with a decrease in POAT after off-pump CABG surgery. The combination of a beta-blocker and magnesium may reduce POAT further. It is recommended that intraoperative magnesium supplementation be part of the care of patients undergoing off-pump CABG surgery.

Predictors of atrial fibrillation after conventional and beating heart coronary surgery: A prospective, randomized study

BACKGROUND

Atrial fibrillation (AF) increases the morbidity of CABG. The pathophysiology is uncertain, and its prevention remains suboptimal. This prospective, randomized study was designed to define the role of cardiopulmonary bypass (CPB) and cardioplegic arrest in the pathogenesis of this complication.

METHODS AND RESULTS

Two hundred patients were prospectively randomized to (1) on-pump conventional surgery [(100 patients, 79 men, mean age 63 (40 to 77) years)] with normothermic CPB and cardioplegic arrest of the heart or (2) off-pump surgery [(100 patients, 82 men, mean age 63 (38 to 86) years)] on the beating heart. Heart rate and rhythm were continuously monitored with an automated arrhythmia detector during the first 72 hours after surgery. Thereafter, routine clinical observation was performed and continuous monitoring restarted in the case of arrhythmia. The association of perioperative factors with AF was investigated by univariate analysis. Significant variables were then included into a stepwise logistic regression model to ascertain their independent influence on the occurrence of AF. There were no significant baseline differences between groups. Thirty-nine patients in the on-pump group and 8 patients in the off-pump group had postoperative sustained AF (P:=0.001). Univariate analysis showed that CPB inclusive of cardioplegic arrest, postoperative inotropic support, intubation time, chest infection, and hospital length of stay were predictors of AF (all P:<0.05). However, stepwise multivariate regression analysis identified CPB inclusive of cardioplegic arrest as the only independent predictor of postoperative AF (OR 7.4; CI 3.4 to 17.9).

CONCLUSIONS

CPB inclusive of cardioplegic arrest is the main independent predictor of postoperative AF in patients undergoing coronary revascularization.

Atrial fibrillation after beating heart surgery

Postoperative atrial fibrillation (AF) is a frequent adverse event after coronary artery bypass grafting (CABG) and may negatively affect the early clinical outcome. We sought to investigate the risk factors, prevalence, and prognostic implications of postoperative AF in patients submitted to CABG without cardiopulmonary bypass (off-pump). The study population comprised 969 patients, 645 men (67%) and 324 women (33%) who had off-pump CABG at the Washington Hospital Center from January 1987 to May 1999. Preoperative AF patients were excluded (n = 15). Two hundred six patients (age 69 +/- 10 years, 137 men [66%]) developed AF, whereas 763 patients (age 61 +/- 12 years, 508 men [67%]) did not. Predictors of AF included age >75 years (odds ratio [OR] 3.0, 95% confidence interval [CI] 1.9 to 4.5; p <0.001), history of stroke (OR 2.1, CI 1.2 to 3.7; p = 0. 007), postoperative pleural effusion requiring thoracentesis (OR 3.2, CI 1.0 to 9.4; p = 0.03), and postoperative pulmonary edema (OR 5.1, CI 1.2 to 21; p = 0.02). Minimally invasive direct CABG was associated with a lower incidence of AF (OR 0.4, CI 0.3 to 0.7; p <0. 001). AF was associated with a prolonged postoperative hospital stay (9 +/- 6 days AF vs 6 +/- 5 days no AF, p <0.001). In-hospital mortality was significantly higher in AF patients (3% AF vs 1% no AF, p = 0.009). Patients with persistent AF had a higher postoperative in-hospital stroke rate than patients without persistent AF (9% vs 0. 6%, p <0.001). AF after beating heart surgery is associated with a higher in-hospital morbidity, mortality, and prolonged hospital stay. A minimally invasive surgical approach (minimally invasive direct CABG) is associated with a lower risk of AF.

Adenosine preconditioning reduces both pre and postischemic arrhythmias in human myocardium

INTRODUCTION

Consistently, clinical series record supraventricular tachyarrhythmias in approximately 30% of patients following coronary artery bypass surgery (CABG). Ischemic preconditioning and adenosine preconditioning (Ado-PC) decrease postischemia/reperfusion (I/R) myocardial stunning, infarct size, and pharmacologically induced arrhythmias in all species including man. We hypothesized that adenosine preconditioning would decrease spontaneous pre- and postischemic atrial arrhythmias in human myocardium. The purposes of this study were to determine the effect of in vivo and in vitro Ado-PC on atrial arrhythmias.

METHODS

Human atrial trabeculae were harvested from CABG patients, placed in organ baths, and paced (1 Hz). Developed force (DF) was recorded during simulated I/R (30/45 min). Prior to I/R, trabeculae were treated with Ado (125 microM) for 5 min (in vitro), or patients were treated with Ado (12 mg iv) 5 min (in vivo) prior to harvest of trabeculae. Contraction frequency >4 Hz (defined as atrial tachyarrhythmias) was recorded in all groups pre- and postischemia.

RESULTS

Control trabeculae exhibited increased tachyarrhythmias pre- and postischemia. In vivo and in vitro Ado-PC suppressed both pre- and postischemic arrhythmias.

CONCLUSIONS

Adenosine preconditioning suppresses the frequency of pre- and postischemic tachyarrhythmias against an ischemia/reperfusion insult in human myocardium. This antiarrhythmic effect occurs with both in vitro and in vivo administration of adenosine. Preconditioning with adenosine prior to elective ischemia/reperfusion is a promising strategy of reducing spontaneous atrial arrhythmias in patients undergoing myocardial revascularization.

Tachyarrhythmias and triggering factors for atrial fibrillation after coronary artery bypass operations

BACKGROUND

We evaluated the role of supraventricular arrhythmias and assessed clinical predictors of atrial fibrillation (AF) that developed after coronary artery bypass operations.

METHODS

Eighty patients, with a mean age of 65.8 years, underwent 24-hour Holter monitoring preoperatively and for 4 consecutive days postoperatively, or until clinically documented AF, for analysis of the number of premature beats and tachyarrhythmias. Atrial areas and atrial peptides were measured preoperatively and postoperatively.

RESULTS

Twenty-nine of 80 (36.3%) patients had postoperative AF. Preoperatively, the maximal supraventricular premature beats per minute were higher in the AF group (p = 0.02). The body mass index and total amount of cardioplegia were lower (p = 0.02 and p = 0.006, respectively), and withdrawal of beta-blockers postoperatively more frequent (p = 0.001) in the AF group, but atrial areas and atrial peptides did not differ.

CONCLUSIONS

Frequent supraventricular premature beats preoperatively may indicate a propensity for AF. A larger amount of cardioplegia during the cross-clamp period may reduce the risk of postoperative AF. Further studies are mandatory to clarify why patients with lower body mass index were more prone to AF.

Systematic off-pump coronary artery revascularization in multivessel disease: experience of three hundred cases

OBJECTIVE

We sought to report our recent experience with off-pump coronary artery revascularization in multivessel disease.

METHODS

Between October 1996 and December 1998, 300 off-pump beating heart operations were performed at the Montreal Heart Institute by a single surgeon, representing 94% of all procedures undertaken during this same time frame (97% for 1998). This cohort of patients was compared with 1870 patients operated on with cardiopulmonary bypass from 1995 to 1996.

RESULTS

Mean age, sex distribution, and preoperative risk factors were comparable for the two groups. On average, 2.92 +/- 0.8 and 2.84 +/- 0.6 grafts per patient were completed in the beating heart and cardiopulmonary bypass groups, respectively. A majority of patients (70%) had either a triple or quadruple bypass. Coronary anastomoses were achieved with myocardial mechanical stabilization and heart "verticalization." Ischemic time was shorter in the beating heart group (29.8 +/- 0.9 vs 45 +/- 0.4 minutes, P <.05). Similarly, the need for transfusion was significantly less in the beating heart group (beating heart operations, 34%; cardiopulmonary bypass, 66%; P <.005). Reduced use of postoperative intra-aortic counterpulsation, as well as a lower rise in creatine kinase MB isoenzyme, was observed in the beating heart group. Operative mortality rates (beating heart operations, 1. 3%; cardiopulmonary bypass, 2%) and perioperative myocardial infarction (beating heart operations, 3.6%; cardiopulmonary bypass, 4.2%) were comparable for the two groups.

CONCLUSION

In a majority of patients, off-pump complete coronary artery revascularization is an acceptable alternative to conventional operations, yielding good results given progressive experience, rigorous technique, and adequate coronary artery stabilization.

Treatment of postoperative atrial fibrillation

Postoperative atrial fibrillation can occur in approximately 30% of patients. Although often a benign complication, it can result in significant morbidity and prolong hospitalization with attendant increased expenditure of health care resources. A rigid approach for prophylaxis and treatment is illogical, but with separate focus on rate control and cardioversion, a sinus mechanism can be safely and reliably achieved with minimal patient discomfort.