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Ann Thorac Surg 2006;81:815-819
© 2006 The Society of Thoracic Surgeons

Original article: Cardiovascular

Early Administration of Clopidogrel Is Safe After Off-Pump Coronary Artery Bypass Surgery

Michael E. Halkos, MD, William A. Cooper, MD, Rebecca Petersen, RN, John D. Puskas, MD, Omar M. Lattouf, MD, Joseph M. Craver, MD, Robert A. Guyton, MD *

Division of Cardiothoracic Surgery, Joseph B. Whitehead Department of Surgery, Emory University and Emory Crawford Long Hospitals, Emory University School of Medicine, Atlanta, Georgia

Accepted for publication August 29, 2005.

* Address correspondence to Dr Guyton, Division of Cardiothoracic Surgery, Medical Office Tower, 6th Floor, Emory Crawford Long Hospital, 550 Peachtree St, NE, Atlanta, GA 30308 (Email: rguyton{at}emoryhealthcare.org).


Drs Guyton, Craver, and Puskas disclose that they have a financial relationship with Medtronic DLP.

 

   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
 References
 
BACKGROUND: Patients who undergo off-pump coronary artery bypass graft surgery (OPCAB) may be hypercoagulable with an increased risk of graft thrombosis due to the lack of platelet dysfunction that accompanies "on-pump" surgery. Clopidogrel may be indicated in these patients to prevent recurrent ischemic events. The purpose of this observational study was to determine the safety of early clopidogrel administration after OPCAB.

METHODS: Thirty-day follow-up of 364 consecutive OPCAB patients (January to June, 2002) was determined from a computerized database. One hundred ninety-three patients received clopidogrel 4 hours postoperatively if chest tube output was less than 100 cc/h for 4 hours, then daily for 4 weeks. Aspirin was administered preoperatively and postoperatively to all patients. Telephone follow-up was made 6 to 12 months after OPCAB.

RESULTS: None of the patients who received clopidogrel in the early postoperative period required reoperation for mediastinal hemorrhage. Mean chest tube drainage at 24 hours was 1,024 ± 563 mL in patients who received clopidogrel and 942 ± 501 mL in patients who did not receive clopidogrel. The total number of blood units transfused and the number of patients receiving blood transfusions were similar between groups. In-hospital mortality was 1.6% in patients who received clopidogrel and 3.5% in patients who did not receive clopidogrel. No group differences in mortality or adverse cardiac events were observed at 6 months. Gastrointestinal bleeding occurred in 2.2% clopidogrel patients versus 0.7% of patients who did not receive clopidogrel.

CONCLUSIONS: When administered according to our postoperative protocol, OPCAB patients can safely receive clopidogrel in the early postoperative period without increased risk for mediastinal hemorrhage.

Off-pump coronary artery bypass graft surgery (OPCAB) has been shown to reduce the morbidity and potentially deleterious effects of cardiopulmonary bypass [1]. In OPCAB, platelet and fibrinolytic defects as well as systemic anticoagulation associated with extracorporeal circulation are avoided, resulting in improved hemostasis. However, recent reports have raised concerns about the existence of a relative hypercoagulable or prothrombotic state after OPCAB and its possible consequences on graft patency [2, 3].

Clopidogrel is a potent platelet aggregation inhibitor that has gained widespread acceptance for the treatment of acute coronary syndromes and as an adjunct to percutaneous coronary intervention [4]. In patients with a history of cardiac surgery, clopidogrel demonstrated superiority over aspirin in preventing vascular death [5]. In the Clopidogrel in Unstable Angina to Prevent Recurrent Events (CURE) trial, patients with a history of revascularization who presented with unstable angina derived greater risk reduction with the addition of clopidogrel to aspirin compared with patients who did not have a history of revascularization [6]. Furthermore, this trial demonstrated improved outcomes when clopidogrel therapy was initiated within 24 hours of the ischemic event [7]. The major limitation of clopidogrel therapy is the occurrence of bleeding events associated with sustained platelet inhibition.

Because of the controversy surrounding a potential procoagulant state after OPCAB, more aggressive postoperative antithrombotic therapy may be warranted. However, this benefit must be weighed against the risk of postoperative hemorrhage in the surgical patient. Therefore, the purpose of this observational analysis was to examine the safety and efficacy of clopidogrel administration early in the postoperative period.


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 Acknowledgments
 References
 
Three-hundred sixty-four consecutive patients who underwent isolated OPCAB from January 1 to June 30, 2002, were retrospectively reviewed. At the time of data collection, Institutional Review Board approval was not required by our institution for retrospective studies, and therefore was not obtained. All operations were performed by five surgeons at Emory University Hospital and Emory Crawford Long Hospital. Of these 364 patients, 193 were prescribed clopidogrel after OPCAB according to surgeon discretion.

Owing to the absence of established protocols documenting the safety of early administration of postoperative clopidogrel, only those patients considered at high risk for recurrent ischemic events, according to the attending surgeon's assessment, received clopidogrel. Factors that led surgeons to prescribe clopidogrel included technically difficult anastomoses, calcified or small (< 2.0 mm) distal target vessels, severe diffuse atherosclerosis, a history of peripheral or cerebrovascular disease, a history of percutaneous coronary revascularization, and diabetes mellitus. However, these were not standardized criteria, and the decision to prescribe clopidogrel was ultimately made according to each surgeon's perception of risk. A history of gastrointestinal bleeding disorders or peptic ulcer disease was considered an absolute contraindication to clopidogrel administration. Similarly, those patients with chest tube output greater than 100 cc/h were not considered for postoperative clopidogrel administration.

An intensive care unit (ICU) protocol based on chest tube output over the first 4 hours after surgery was established for patients who were prescribed clopidogrel. In all patients prescribed clopidogrel (clopidogrel group), ICU nurses administered 150 mg of clopidogrel either orally or by nasogastric tube 4 hours after surgery if chest tube output was less than 100 cc/h for the first 4 postoperative hours. After the initial loading dose, these patients received clopidogrel at 75 mg daily for 4 weeks. Patients who were initially prescribed clopidogrel who had chest tube drainage more than 100 cc/h for any of the first 4 postoperative hours had their dose withheld and did not receive postoperative clopidogrel. Patients who did not receive the loading dose (150 mg) or received clopidogrel at a later time point in the postoperative period were not included in this analysis. All patients received aspirin in the operating room before incision, on the first postoperative day, and then daily and as part of their discharge medication regimen.

In-hospital morbidity and mortality data and 30-day follow-up data were determined retrospectively from a computerized database. In-hospital deaths included deaths within the immediate postoperative period and the initial 30 days after surgery. Chest tube drainage was assessed hourly in the ICU, and the decision for mediastinal reexploration was determined by the attending surgeon based on persistent or high-output chest tube drainage. The number of blood transfusions (units) per patients was also recorded for the first 24 hours and for the entire hospitalization.

Thirty-day follow-up data were obtained for all patients (100%) and were corroborated from clinic and hospital records and with information obtained from telephone follow-up interviews. Telephone interviews were conducted 265 ± 63.3 days after OPCAB in 179 clopidogrel patients (93%) and 227 ± 78.2 days after OPCAB in 151 patients (88%) who did not receive clopidogrel. All interviews were conducted by physicians or trained nursing personnel. Adverse cardiac events were defined as new-onset or unstable angina, ST-elevation or non–ST-elevation myocardial infarction, and the need for revascularization. Data collected from telephone interviews were used to determine 6-month mortality, need for revascularization, myocardial infarction, the presence of unstable angina, stroke and transient ischemic attack, and bleeding events. Death from cardiovascular causes was defined as any death from myocardial infarction, stroke, or any other vascular cause contributing to death. In-hospital deaths were excluded from the 6-month analysis.

Surgical Technique
Exposure was obtained through a standard median sternotomy incision in all cases. Incisions and closure techniques were the same in both groups. Intraoperative anticoagulation and reversal with protamine varied among individual surgeons. Aprotinin was not routinely used. A cell-saving reservoir (COBE Cardiovascular, Arvada, Colorado) was utilized for all patients in both groups. Fine monofilament suture (7-0 or 8-0 Surgipro; United States Surgical Corporation, Norwalk, Connecticut) was used for all distal anastomosis. Proximal anastomoses were constructed with 5-0 or 6-0 Surgipro suture for venous anastomoses and 6-0 or 7-0 Surgipro suture for arterial anastomoses to the aorta. The OPCAB was performed with a Medtronic Octopus (Medtronic DLP, Minneapolis, Minnesota) stabilizing device for coronary stabilization and deep pericardial traction sutures for cardiac displacement and presentation. Care was taken to maintain hemodynamic stability (mean arterial blood pressure ≥ 65 mm Hg) throughout the operation [8].


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 Acknowledgments
 References
 
Patient Characteristics
Clopidogrel administration was comparable among individual surgeons. Preoperative risk data and patient characteristics can be seen in Table 1. Three-vessel coronary artery disease (CAD), prior percutaneous intervention, and Canadian Cardiovascular Society III to IV angina were more common in the clopidogrel patients compared with the no-clopidogrel patients. New York Heart Association III to IV heart failure was more common in the clopidogrel group, but left ventricular ejection fraction was similar between groups.


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  		Table 1. Preoperative Characteristics
 
Outcomes
Patients who were not prescribed clopidogrel or patients who were prescribed clopidogrel but never received it owing to high chest tube output comprised the no-clopidogrel group. Because this may have unfavorably biased this group of patients toward adverse outcomes, a statistical comparison between groups (clopidogrel versus no-clopidogrel) was not performed.

None of the patients in the clopidogrel group required reexploration for bleeding in contrast to the 3 patients who did not receive clopidogrel. Time to discharge (clopidogrel 5.5 ± 4.5 days versus no-clopidogrel 6.0 ± 4.3 days), ICU stay (clopidogrel 42.5 ± 100 hours versus no-clopidogrel 43.9 ± 78.5 hours), and ventilation time (clopidogrel 20.1 ± 90 hours versus no-clopidogrel 18.4 ± 63 hours) were similar for both groups. Chest tube drainage at 8 and 24 hours was comparable between groups. In the clopidogrel group, 79 patients (41%) received blood transfusions, and the mean number of packed red blood cells transfused during hospitalization was 1.8 ± 2.2 units (Table 2). In the no-clopidogrel group, 73 patients (43%) received blood transfusions, and the mean number of packed red blood cells transfused was 1.8 ± 2.6 units. Moreover, no significant differences were noted in the development of postoperative (within 30 days) pleural effusions requiring thoracentesis (clopidogrel 1.6% versus no clopidogrel 3.4%).


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  		Table 2. Postoperative Blood Loss, Reexploration, and Blood Transfusions
 
In-hospital (30-day) deaths occurred in 1.6% of clopidogrel patients and 3.5% of no-clopidogrel patients. However, none of the in-hospital deaths were directly attributed to clopidogrel administration. One patient in the clopidogrel group died from complications of a nonhemorrhagic stroke suffered within 30 days of surgery. In the no-clopidogrel group, 1 patient who required reexploration for mediastinal hemorrhage ultimately succumbed to multiorgan system failure. Six-month mortality was 3.4% in the clopidogrel group and 0.6% in the no-clopidogrel group. None of the 6-month deaths in either group were directly attributed to cardiovascular causes. Data for 30-day and 6-month adverse cardiac and cerebrovascular events are described in Table 3 and Table 4.


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  		Table 3. Total 30-Day and 6-Month Adverse Cardiac Events
 

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  		Table 4. Total 30-Day and 6-Month Adverse Cerebrovascular Events
 
Bleeding events were defined according to previously established criteria set forth by the CURE trial investigators [6]. Two patients in the clopidogrel group suffered major but nonfatal gastrointestinal bleeding episodes that required surgical intervention for control (Table 5). Both events occurred within 6 weeks of surgery during clopidogrel treatment. The minor bleeding events were due to epistaxis that did not require hospitalization but did lead to cessation of clopidogrel. No major bleeding events and 1 minor bleeding event occurred in patients who did not receive clopidogrel.


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  		Table 5. Bleeding Complications
 

   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
Acknowledgments
 References
 
Off-pump coronary revascularization has emerged as a popular alternative to conventional coronary artery surgery using cardiopulmonary bypass. Advantages of this approach include improved hemostasis, lower transfusion requirements, and attenuated systemic inflammatory activation [9–11]. However, these hematologic derangements that are common with cardiopulmonary bypass may offer some benefit by inhibiting the initiating physiologic events that ultimately contribute to graft occlusion.

Clopidogrel, when used in combination with aspirin, has been proven in large randomized trials to decrease the risk of recurrent ischemic events in acute coronary syndromes and to reduce the incidence of stent thrombosis in patients undergoing percutaneous coronary interventions [4, 7]. Although clopidogrel has been adopted by cardiologists to further reduce these risks, surgeons have been reluctant to implement this therapy because of the potential increased risk for bleeding in the postoperative period [12]. Therefore, the purpose of this study was to evaluate the safety and efficacy of early administration of clopidogrel after OPCAB.

The hematologic alterations that occur with cardiopulmonary bypass are relatively reduced in off-pump surgery. Casati and colleagues documented increased platelet counts and decreased fibrinolysis in patients undergoing off-pump compared with on-pump surgery [13]. Furthermore, others have shown increased procoagulant activity in off-pump coronary procedures, similar to that observed after major general surgical procedures [14]. Therefore, a higher incidence of graft thrombosis may be anticipated in OPCAB where platelet dysfunction, activation of fibrinolysis, and coagulopathy associated with cardiopulmonary bypass are attenuated. The absence of the detrimental effects of the heart-lung machine on hemostasis and systemic inflammatory activation, combined with the activation of acute phase reactants and local tissue injury associated with major surgical procedures shifts the balance toward more postoperative thromboembolic complications instead of surgical bleeding after OPCAB. However, prospective studies consistently linking these hematologic variables with clinical outcomes have yielded inconclusive results [15]. In addition, other investigators have not reported an increase in procoagulant activity [16].

In the present study, clopidogrel therapy was initiated in the ICU after OPCAB if chest tube drainage was less than 100 cc/h for 4 hours. Patients who received clopidogrel did not have an increased risk for reexploration and had 24-hour chest tube drainage and blood transfusion requirements comparable to those of patients who did not receive clopidogrel.

Other investigators have evaluated mediastinal drainage and blood transfusion requirements after OPCAB and have documented comparable results. Srinivasan and colleagues [17] reported median postoperative blood loss in the ICU of 845 mL. A study by Nuttall and colleagues [18] reported median chest tube drainage of 950 mL in the first 24 postoperative hours. However, direct comparison of these studies and others [9, 19] with the present study must be done with caution because of the differences in the preoperative use of aspirin, variations in intraoperative anticoagulation and anticoagulation reversal regimens, utilization of intraoperative blood loss salvage techniques, and the lack of standardized criteria for postoperative blood transfusion.

Clopidogrel has been shown to reduce recurrent ischemic events in coronary artery bypass patients. Bhatt and colleagues [5] reported a substantial risk reduction of recurrent ischemic events in patients with a history of cardiac surgery treated with clopidogrel instead of aspirin, even though treatment was delayed. In the CURE trial, the benefits of clopidogrel therapy emerged when treatment was started within 24 hours of the ensuing ischemic event [7]. Because the initial physiologic events that contribute to graft occlusion (platelet activation, intimal injury, inflammatory cell activation) occur in the immediate postoperative period, further reductions in recurrent ischemic events may be possible. Although extended treatment may play a role in secondary prevention by preventing ischemic events in nongrafted vessels, early treatment may augment protection in the grafts as well as at the anastomosis. Therefore, instead of delaying treatment for days or weeks after surgery to avoid the potential bleeding risks related to surgery, we started clopidogrel treatment in the early postoperative period.

In 2 patients who received postoperative clopidogrel, however, gastrointestinal bleeding developed that required surgical intervention for control. Neither of these patients had a history of ulcer disease or a history of gastrointestinal bleeding, and they were not treated with other anticoagulants such as warfarin. Furthermore, these events occurred after discharge but during clopidogrel treatment. That underscores the importance of weighing the risks of bleeding diatheses against the benefits of optimal antithrombotic therapy.

This study has several important limitations. This was an observational analysis in which patients were prescribed clopidogrel based on the surgeon's perception of risk for recurrent ischemic events. Although none of the patients who were administered clopidogrel required reexploration, that should not imply that clopidogrel therapy after OPCAB is without risk, but it does suggest that these risks can be minimized when administered according to a defined protocol. Moreover, because patients with chest tube output greater than 100 cc/h for the first 4 hours were not administered clopidogrel, reexploration for bleeding would be expected to occur more often in patients who did not receive clopidogrel. Furthermore, this study was underpowered to detect significant differences in recurrent ischemic events in contrast to the CURE trial (12,562 patients) [6].

In conclusion, this study documents the safety of early clopidogrel administration after off-pump coronary revascularization when administered according to a defined postoperative protocol. However, the risk of major gastrointestinal bleeding needs to be considered. Larger prospective studies would be needed to examine the effects of early clopidogrel administration in reducing short- and long-term adverse cardiovascular events after off-pump coronary artery surgery. In the absence of such a trial, however, this study provides insight into the risk, or lack thereof, of administering clopidogrel in the early postoperative period. Therefore, we routinely initiate clopidogrel administration, according to our ICU protocol, in the early postoperative period for patients undergoing OPCAB.


   Acknowledgments
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
References
 
The authors would like to thank Rebecca Petersen, Katherine Egan, and Susan McCall for their assistance in data collection and analysis, and for their assistance in the preparation of this manuscript.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Acknowledgments
 References
 

  1. Cleveland JC, Shroyer ALW, Chen AY, Peterson E, Grover FL. Off-pump coronary artery bypass grafting decreases risk-adjusted mortality and morbidity Ann Thorac Surg 2001;72:1282-1289.[Abstract/Free Full Text]
  2. Kim KB, Lim C, Lee C. Off-pump coronary artery bypass may decrease the patency of saphenous vein grafts Ann Thorac Surg 2001;72(Suppl):1033-1037.
  3. Mariani AM, Gu J, Boonstra PW. Procoagulant activity after off-pump coronary operationis the current anticoagulation adequate?. Ann Thorac Surg 1999;67:1370-1375.[Abstract/Free Full Text]
  4. Steinhubl SR, Berger PB, Mann III JT, et al. Early and sustained dual oral antiplatelet therapy following percutaneous coronary interventiona randomized controlled trial. JAMA 2002;288:2411-2420.[Abstract/Free Full Text]
  5. Bhatt DL, Chew DP, Hirsch AT, et al. Superiority of clopidogrel versus aspirin in patients with prior cardiac surgery Circulation 2001;103:363-368.[Abstract/Free Full Text]
  6. Yusuf S, Zhao F, Mehta SR, et al. Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation N Engl J Med 2001;345:494-502.[Abstract/Free Full Text]
  7. Yusuf S, Mehta SR, Zhao F, et al. Early and late effects of clopidogrel in patients with acute coronary syndromes Circulation 2003;107:966-972.[Abstract/Free Full Text]
  8. Puskas JD, Vinten-Johansen J, Muraki S, Guyton RA. Myocardial protection for off-pump coronary artery bypass surgery Thorac Cardiovascular Surg 2001;13:82-88.
  9. Puskas JD, Williams WH, Duke PG, et al. Off-pump coronary artery bypass grafting provides complete revascularization with reduced myocardial injury, transfusion requirements, and length of staya prospective randomized comparison of two hundred unselected patients undergoing off-pump versus conventional coronary artery bypass grafting. J Thorac Cardiovasc Surg 2003;125:797-808.[Abstract/Free Full Text]
  10. Menasche P. The systemic factorthe comparative roles of cardiopulmonary bypass and off-pump surgery in the genesis of patient injury during and following cardiac surgery. Ann Thorac Surg 2001;72(Suppl):2260-2265.
  11. Schulze C, Conrad N, Schutz A, et al. Reduced expression of systemic proinflammatory cytokines after off-pump versus conventional coronary artery bypass grafting Thorac Cardiovascular Surg 2000;48:364-369.[Medline]
  12. D'Ancona G, Donias HW, Karamanoukian RL. OPCAB therapy surveyoff-pump clopidogrel, aspirin, or both therapy survey. Heart Surg Forum 2001;4:354-358.[Medline]
  13. Casati V, Gerli C, Franco A. Activation of coagulation and fibrinolysis during coronary surgeryon-pump versus off-pump techniques. Anesthesiology 2001;95:1103-1109.[Medline]
  14. Mariani MA, Gu YJ, Boonstra PW, et al. Procoagulant activity after off-pump coronary operationis the current anticoagulation adequate?. Ann Thorac Surg 1999;67:1370-1375.[Abstract/Free Full Text]
  15. Kurlansky PA. Is there a hypercoagulable state after off-pump coronary artery bypass surgery? What do we know and what can we do? J Thorac Cardiovasc Surg 2003;126:7-10.[Free Full Text]
  16. Englberger L, Immer FF, Eckstein FS, et al. Off-pump coronary artery bypass operation does not increase procoagulant and fibrinolytic activitypreliminary results. Ann Thorac Surg 2004;77:1560-1566.[Abstract/Free Full Text]
  17. Srinivasan AK, Grayson AD, Pullan DM, Fabri BM, Dihmis WC. Effect of preoperative aspirin use in off-pump coronary artery bypass operations Ann Thorac Surg 2003;76:41-45.[Abstract/Free Full Text]
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