Effects of low dose aspirin (50 mg/day), low dose aspirin plus dipyridamole, and oral anticoagulant agents after internal mammary artery bypass grafting: patency and clinical outcome at 1 year. CABADAS Research Group of the Interuniversity Cardiology Institute of The Netherlands. Prevention of Coronary Artery Bypass Graft Occlusion by Aspirin, Dipyridamole and Acenocoumarol/Phenprocoumon Study.
OBJECTIVE
This study was performed to compare the efficacy and safety of aspirin, aspirin plus dipyridamole, and oral anticoagulant agents in the prevention of internal mammary artery graft occlusion.


BACKGROUND
Antithrombotic drugs increase vein graft patency after coronary artery bypass surgery. Their benefit after internal mammary artery grafting has not been established.


METHODS
Angiographic internal mammary artery graft patency at 1 year was assessed in 494 patients who received both internal mammary artery and vein grafts. These patients were a subgroup of a prospective, randomized vein graft patency study in 948 patients assigned to treatment with aspirin, aspirin plus dipyridamole, or oral anticoagulant agents. The design was double-blind for both aspirin groups and open for oral anticoagulant treatment. Dipyridamole (5 mg/kg body weight per 24 h intravenously, followed by 200 mg twice daily) and oral anticoagulant agents (prothrombin time target range 2.8 to 4.8 international normalized ratio) were started before operation, and low dose aspirin (50 mg/day) after operation. Clinical outcome was assessed by the incidence of myocardial infarction, thrombosis, major bleeding or death.


RESULTS
Occlusion rates of distal anastomoses were 4.6% in the aspirin plus dipyridamole group and 6.8% in the oral anticoagulant group versus 5.3% in the aspirin group (p = NS). Overall clinical event rates were 23.3% and 13.3% in the aspirin plus dipyridamole group and the aspirin group, respectively (relative risk 1.75, 95% confidence interval 1.09 to 2.81, p = 0.025), and 17.1% in the oral anticoagulant group.


CONCLUSIONS
Internal mammary artery graft patency at 1 year is not improved by aspirin plus dipyridamole or oral anticoagulant agents over that obtained with low dose aspirin alone. However, there is evidence that the overall clinical event rate increases if dipyridamole is added to aspirin.
van der Meer
J
J
Department of Cardiology, University Hospital, Groningen, The Netherlands.
Brutel de la Rivière
A
A
van Gilst
W H
WH
Hillege
H L
HL
Pfisterer
M
M
Kootstra
G J
GJ
Dunselman
P H
PH
Mulder
B J
BJ
Lie
K I
KI
D000074:Acenocoumarol / Q000008:administration & dosage / Q000627:therapeutic use; D000925:Anticoagulants / Q000008:administration & dosage* / Q000627:therapeutic use; D001241:Aspirin / Q000008:administration & dosage* / Q000627:therapeutic use; D004176:Dipyridamole / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D005260:Female; D006083:Graft Occlusion, Vascular / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D007387:Internal Mammary-Coronary Artery Anastomosis; D008297:Male; D008875:Middle Aged; D010644:Phenprocoumon / Q000008:administration & dosage / Q000627:therapeutic use; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D014654:Vascular Patency / Q000187:drug effects
D000925:Anticoagulants; D004176:Dipyridamole; D000074:Acenocoumarol; D010644:Phenprocoumon; D001241:Aspirin