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Ann Thorac Surg 2001;71:1748
© 2001 The Society of Thoracic Surgeons
a Department of Thoracic and Cardiovascular Surgery, University Hospital, SE-751 85 Uppsala, Sweden
b Department of Cardiology, University Hospital, SE-751 85 Uppsala, Sweden
e-mail: elisabeth.stahle{at}thorax.uas.lul.se
To the Editor
Clark and colleagues [1] raise an interesting issue with their study, which they reported recently in The Annals: patients who receive therapeutic doses of low–molecular-weight heparin (LMWH) in close proximity to coronary artery bypass surgery are likely to bleed more than are patients in whom LMWH is stopped at least 12 hours before surgery.
In practice only a minority of surgical patients experience recurrent ischemia within 12 hours of stopping treatment, necessitating treatment with LMWH or unfractionated heparin (UFH) in close proximity to surgery. However, we need to learn how to manage this situation and, moreover, how to manage patients on effective antithrombotic treatment when such situations arise.
As investigators involved in the FRISC II (Fragmin and Fast Revascularisation during Instability in Coronary artery disease) study [2, 3], we can refer Clark and colleagues to our experience. In FRISC II, the policy of early revascularization in conjunction with aggressive medical therapy (all patients received acute treatment with dalteparin for 5–7 days in addition to aspirin, ß-blockers, calcium antagonists, and nitrates as indicated), was associated with improved outcomes in comparison with a noninvasive approach. The protocol stipulated that the last injection of dalteparin be given no later than 12 hours before revascularization. Only 26 patients received LMWH within 12 hours of surgery at the investigators’ discretion. This represents only 2% of the total invasive population and 6% of the coronary artery bypass grafting (CABG) population in FRISC II. Looking at the raw data, bleeding was reported for 3 of the 26 patients: there were 2 cases in which bleeding after coronary artery bypass graft surgery led to reoperation. Although there are no data comparing the bleeding risk of LMWH and UFH, we would agree with Gravlee, in his commentary on the study by Clark and colleagues [1], that currently the easier reversibility of UFH could make it a possible option for treatment for patients with recurrent angina who are to undergo surgery. However, if LMWH is stopped 12 hours before elective/planned surgery, very few patients will have angina or silent ischemia during that period. As patients have adequate antithrombotic cover for at least 12 hours after a subcutaneous injection of LMWH, initiation of UFH could seriously increase the bleeding risk without any potential advantage. Preferably patients experiencing breakthrough angina should proceed to urgent surgery if appropriate or alternatively should receive short-acting fibrinogen receptor inhibitors.
Clark and colleagues point out in their conclusion that the risk of bleeding with LMWH must be weighed against the risks of acute ischemic events if LMWH is stopped before surgery. Reassuringly, the low event rate in the invasive arm of FRISC II indicate no compromise in outcomes for the great majority of patients if dalteparin is stopped 12 hours before surgery (30-day mortality after CABG was only 2%, whereas death/myocardial infarction at 6 months was 9.4% in the invasive group as a whole) [3]. In the study by Clark and colleagues, patients who received LMWH no less than 12 hours before surgery did not have an increased risk for bleeding as compared with those treated with UFH. This finding and the results of FRISC II do not lend any support to advice to stop LMWH earlier than 12 hours or to switch to UFH before surgery in patients with unstable angina.
In patients with unstable angina there is a high prevalence of intracoronary thrombus. It has been proved that patients with unstable angina benefit from antiplatelet and antithrombotic treatment and possibly also from additional treatment with short-acting fibrinogen receptor inhibitors [4]. Indeed, the recent recommendations from the Task Force of the European Society of Cardiology suggest that in a relatively stable patient, in the face of important intracoronary thrombus, it may be appropriate to postpone the procedure and to prepare the patient with aggressive anticoagulation and intensive antiplatelet treatment [4]. If surgery is indicated such patients will inevitably have an impaired coagulation and an increased risk for bleeding. Surgeons and anesthesiologists need to learn how to deal with these patients to provide safe surgery despite impaired hemostasis. A meticulous surgical technique is a prerequisite for optimal hemostasis in patients with unstable angina.
References
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  S.E. Husted, L. Wallentin, B. Lagerqvist, F. Kontny, E. Stahle, and E. Swahn Benefits of extended treatment with dalteparin in patients with unstable coronary artery disease eligible for revascularization Eur. Heart J., August 1, 2002; 23(15): 1213 - 1218. [Abstract] [Full Text] [PDF]
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