Survey of cardiac surgeons' perceptions of the addition of ASA to warfarin for patients with mechanical heart valves.

Evidence suggests that the addition of acetylsalicylic acid (ASA) to warfarin therapy among patients with mechanical heart valves may reduce mortality, at a slightly higher bleeding risk. A survey was conducted of North American cardiac surgeons to assess whether they routinely use ASA in conjunction with anticoagulants among such patients. From a list of 142 cardiac surgeons and centres, questionnaires were successfully transmitted by fax to 137. Respondents were surveyed about their prescribing habits of both warfarin and ASA among patients with mechanical heart valves. Information collected included the target international normalized ratio (INR) and reasons for not routinely prescribing ASA, when applicable. One hundred and eighteen cardiac surgeons (86%) returned the questionnaire: 75% were American and 25% Canadian. All surgeons (100%) stated that they use warfarin for patients with mechanical valves, but there was little consensus about the target INR. Only 25 respondents (21%) routinely used ASA in conjunction with anticoagulants, while 90 (76%) said they would not. The most common reason cited for withholding ASA was the perceived increased risk of bleeding (49% of nonusers), while another 23% felt that there is no benefit. Of the 90 surgeons who would not routinely prescribe ASA, 50 (55%) would on occasion. The most commonly used dose of ASA was 80 to 100 mg daily (79%). Low dose ASA, in conjunction with warfarin, is underused by North American cardiac surgeons for the prevention of systemic thromboembolism among patients with mechanical heart valves. Most surgeons avoid ASA out of concern for the increased risk of hemorrhage and a belief that there is no benefit. These perceptions are not supported by recent scientific data, however.