Transcranial Doppler (TCD) Assessment During Early Anti-thrombotic Therapy After Bioprosthetic Aortic Valve Replacement
Summary
The purpose of this study is to determine if there is any difference in the counts of cerebral emboli and platelet function between two prophylactic treatments of thrombosis currently used at University of Ottawa Heart Institute for the first three months after surgery in low-risk patients undergoing aortic valve replacement with a bioprosthetic valve: 1) daily use of high-dose aspirin [325 mgs], and 2) the combination of oral Warfarin [target INR 2.0 to 3.0] and low-dose aspirin [81 mg].
Description
Background:
There are several medications used to prevent blood clotting in patients undergoing surgical replacement of their aortic valves with tissue valves. One of these medications is called warfarin (Coumadin ®) which prevents blood clotting by making the blood "thinner." Another medication is aspirin which prevents the aggregation (clustering) of cells in the blood called platelets. Some clinicians consider that using only aspirin should be enough to protect the patients against the presence of clots in the blood, but others consider that aspirin should be combined with warfarin for better protection. Moreover, physicians express concern over the use of oral anticoagulation due to the possibility of an increased risk of bleeding. The effects of these medications for preventing blood clots traveling to the brain after the surgery are currently unknown. Transcranial doppler ultrasound will be used in these patients to evaluate non-invasively the quantity of fragments of clots circulating in the arteries of the brain. In addition, platelet function will be measured to determine how effective these treatments are for preventing the aggregation of the blood cells called platelets, which may be involved in clot formation.
Objective:
Our purpose is to determine if there is any difference in the counts of cerebral emboli and platelet function between two prophylactic treatments of thrombosis currently used in our institution for the first three months after surgery in these patients: 1) daily use of high-dose aspirin [325 mgs], and 2) the combination of oral Warfarin [target INR 2.0 to 3.0] and low-dose aspirin [81 mg].
Methods:
Patients with low risk profile undergoing primary aortic valve replacement with a bioprosthetic (tissue) valve will be eligible for the study. Patients will receive one of the two prophylactic treatments of thrombosis (1 or 2) depending on the surgeon's preference. Platelet function will be measured before surgery and transcranial doppler within the first 24 hours immediately after the surgery. At the end of one month following surgery, all patients will undergo transcranial doppler and platelet function assessment. The study will be powered on demonstrating the hypothesis of substantial equivalence between the two treatments as regarding the primary outcome (cerebral emboli).
Outcome measures:
1. Primary outcome:
Bilateral counts of cerebral emboli in the middle cerebral arteries with transcranial doppler ultrasound at one month after surgery
2. Secondary outcomes:
Platelet function, incidence of major adverse neurologic and bleeding events at one month following surgery
Study Design
Observational Model: Case Control, Time Perspective: Prospective
Conditions
Aortic Valve Disease
Intervention
Prophylaxis of Thrombosis after aortic valve replacement
Location
University of Ottawa Heart Institute
Ottawa
Ontario
Canada
K1Y 4W7
Status
Active, not recruiting
Source
University of Ottawa Heart Institute
Results (where available)
Links
- Source: http://clinicaltrials.gov/show/NCT00465218
- Information obtained from ClinicalTrials.gov on July 15, 2010
Medical and Biotech [MESH] Definitions
Aortic Valve Prolapse
The downward displacement of the cuspal or pointed end of the trileaflet AORTIC VALVE causing misalignment of the cusps. Severe valve distortion can cause leakage and allow the backflow of blood from the ASCENDING AORTA back into the LEFT VENTRICLE, leading to aortic regurgitation.
Aortic Valve Insufficiency
Pathological condition characterized by the backflow of blood from the ASCENDING AORTA back into the LEFT VENTRICLE, leading to regurgitation. It is caused by diseases of the AORTIC VALVE or its surrounding tissue (aortic root).
Discrete Subaortic Stenosis
A type of constriction that is caused by the presence of a fibrous ring (discrete type) below the AORTIC VALVE, anywhere between the aortic valve and the MITRAL VALVE. It is characterized by restricted outflow from the LEFT VENTRICLE into the AORTA.
Aortic Valve Stenosis
A pathological constriction that can occur above (supravalvular stenosis), below (subvalvular stenosis), or at the AORTIC VALVE. It is characterized by restricted outflow from the LEFT VENTRICLE into the AORTA.
Sinus Of Valsalva
The dilatation of the aortic wall behind each of the cusps of the aortic valve.
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