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P7. POSTOPERATIVE ASPIRIN RESISTANCE IS ASSOCIATED WITH THE STERNOTOMY REQUIRED FOR CABG
Robert S. Poston, Jr., Junyan Gu, James Brown, James Gammie, Bartley P. Griffith.
Surgery, University of Maryland, Baltimore, MD, USA.

OBJECTIVE: The sternotomy required for CABG creates bleeding and platelet turnover. Generation of new, aspirin naive platelets increases the fraction able to form thromboxane within the daily dosing interval of aspirin. Therefore, we hypothesized that avoiding a sternotomy for multivessel CABG would reduce the incidence of platelet activation despite aspirin use (i.e. aspirin resistance).
METHODS: Consecutive patients with stable multivessel CAD underwent off-pump CABG via sternotomy (n=20) or mini-thoracotomy using a LIMA-radial composite graft (n=12). All patients received aspirin as the only antiplatelet therapy. Aspirin resistance was determined preoperatively, immediately after surgery, and on postoperative days 1 and 3 and defined by agreement of 3 out of 4 assays: modified thrombelastograpy (using arachidonic acid), whole blood aggregometry (using low vs. high dose collagen), flow cytometry and by serum 11-dehydro TXB2 levels. Bleeding was quantified the volume collected by the cellsaver device (intraop) and chest tubes (postop).
RESULTS: Patients in both groups had comparable age, co-morbidities, ejection fraction and number of distal anastomoses (2.3±0.5 vs. 2.6±0.9). Intraoperative (225±35 vs. 733±69ml) and postoperative (317±42 vs. 893±81ml) bleeding were significantly reduced by a thoracotomy. Aspirin resistance was diagnosed postoperatively in 9 patients in the sternotomy group and 1 patient in the thoracotomy group (p<0.05, Fisher's exact test).
CONCLUSIONS: Coronary surgery via small thoracotomy avoids the risk of sternal infection and provides improved cosmesis. In addition, our preliminary data suggests that patients who require multivessel revascularization demonstrate improved aspirin responsiveness early postop, potentially mediated by significantly reduced rates of bleeding vs. a sternotomy.


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