Clinical Trial of the On-X Valve Using Low Dose Anticoagulation
Subjects who have valvular heart disease and require replacement of their heart valve are being invited to participate in this study. Their treatment will be similar to that provided to patients who have their heart valves replaced with any other commercially available prosthetic heart valve.
Before surgery, the patient will have routine diagnostic tests to assess the status of their heart valves. Then surgery with implantation of the Prosthesis. The patient and #146;s progress will be closely monitored and recorded at a total of 7 visits over 5 years.
At the 3 month visit they will be randomly assigned to one of two anticoagulation drug therapies depending upon the type of implant they receive and their general health apart from the valve. These two therapies are the standard anticoagulant therapy now used based on the recommendations of the American Heart Association or a therapy with a reduced dose of anticoagulation. Laboratory blood samples will be drawn and other diagnostic tests will be done during the appropriate preoperative and follow-up visits. The diagnostic tests will be an INR(International Normalized Ratio), which is a laboratiory test that measures the time it takes for blood to clot and compares it to an average. To find the INR a small sample of blood is taken from a fingertip or vein. The time it takes the blood to clot is measured. Then a ratio-an INR-is established. The higher the INR, the longer it takes the blood to clot. This can help prevent clots that may lead to strokes. and echocardiograms at 1, 3 and 5 years following surgery to assess valve function. The drug therapy may require additional laboratory blood tests as ordered by your physician.The anticoagulant therapies include three treatment groups for patients with: 1.) low risk of clotting having an aortic valve replacement, 2.) higher risk of clotting having an aortic valve replacement, enrollment ceased in this arm, and 3.) either a mitral valve replacement or replacement of both (double) valves. Each treatment group will have a control group that uses the presently recommended antithrombotic drug therapy of the American Heart Association, Coumadin(TM) and aspirin. Each patient will be randomly assigned to the treatment or the control group indicated by the criteria above.
The treatment drug therapy for the low risk aortic valve replacement group is a combination of two presently used drugs – aspirin and Plavix(TM). The treatment drug therapy for the high risk aortic valve replacement group, the mitral or double valve replacement is a reduced dose of Coumadin and aspirin.
1. Patients requiring isolated aortic valve replacement (AVR), or isolated mitral valve replacement (MVR).
2. AVR patients receiving low dose or antiplatelet only anticoagulation will be divided into groups at low risk and high risk for thromboembolism with all patients being in the low risk group except for patients with the following conditions which place a patient in the high risk group:
Chronic atrial fibrillation (see definition below)
Left ventricular ejection fraction < 30 %
Enlarged left atrium >50mm diameter
Spontaneous echo contrasts in the left atrium
Neurological events (see definition below)
Hypercoagulability (see definition below)
Left or right ventricular aneurysm
Lack of platelet response to aspirin or clopidogrel
Women receiving estrogen replacement therapy
3. Concomitant cardiac surgery is allowed
4. Adult patients