Dual Antiplatelet Therapy in Patients With Aspirin Resistance Following Coronary Artery Bypass Grafting
Status:
Completed
Trial end date:
2013-02-01
Target enrollment:
Participant gender:
Summary
Reactive platelet hyperactivity following coronary artery bypass grafting (CABG) might lead
to thrombotic complications and major ischemic cardiac events. The aim of this study is to
evaluate the changes in platelet reactivity following CABG and to clarify a potentially
beneficial effect of dual antiplatelet therapy in the group of patients with documented
aspirin resistance following CABG. Platelet function will be assessed by multiple electrode
aggregometry. Aortocoronary vein graft disease is comprised of three distinct but
interrelated pathological processes: thrombosis, intimal hyperplasia and atherosclerosis.
Early vein thrombosis is a major cause of vein graft attrition during the first month after
CABG.
Bypass patency can be improved with antiplatelet therapy which is the mainstay of treatment
for patients after CABG. A beneficial effect of acetylsalicylic acid (ASA) on vein graft
patency has been previously shown. Some patients experience thrombotic events despite
continuous aspirin administration after CABG. The investigators hypothesized that low
responsiveness to aspirin might be a precipitating factor for adverse thrombotic events
following CABG.
Low responsiveness to ASA, as assessed by platelet function tests, varies widely among
patients. The etiology of postoperative platelet hyperactivity remains to be elucidated.
In this study a new point-of-care assay named multiple electrode aggregometry (MEA) using a
device called Multiplate analyzer (Dynabyte, Munich, Germany) has been utilized. It allows
for rapid and standardized assessment of platelet function parameters.
This is a prospective randomized trial. The aim of the study is to document whether
introduction of dual antiplatelet therapy in patients with ASA resistance will lead to a
lower incidence of major adverse cardiac events (MACE) at a six month follow up. The
composite endpoint will include death, non-fatal myocardial infarction, stroke and cardiac
rehospitalization. All patients will receive 300 mg of ASA starting 6 hours after surgery,
provided that the chest tube output is minimal. On postoperative day 4 their platelet
function will be assessed using the above mentioned MEA. The patients found to be aspirin
resistant will then undergo the process of randomization. The first arm will include patients
with ASA resistance in whom no additional antiaggregation will be administered. In the second
arm the investigators will include patients who were randomized to receive 75 mg of
clopidogrel in addition to the standard antiplatelet regimen of 300 mg of ASA.
Platelet function monitoring allows for individual tailoring of the antiplatelet therapy. The
goal of this study is to define whether this strategy will lead to improved patient outcomes.
Both major and minor bleeding complications will be strictly monitored and reported.