A blood clot, or thrombus, that forms in a blood vessel or heart chamber may be either venous or arterial in origin. Venous thrombi develop in areas of slow blood flow, e.g., in a lower extremity. The clot forms rapidly and lacks organization. Although venous occlusion does occur, a far greater concern is the tendency of small emboli to detach from venous thrombi.9 These emboli tend to travel to and wedge into pulmonary arteries, preventing deoxygenated blood from entering the lungs.9
An arterial thrombus forms when platelets aggregate and become surrounded by fibrin and erythrocytes.9 Arterial thrombi cause coronary artery thrombosis, coronary artery rethrombosis after thrombolysis, occlusion of coronary artery grafts and lead to unstable angina pectoris, MI, recurrent MI, and sudden cardiac death. Arterial thrombi also contribute to systemic embolization in patients with atrial fibrillation or prosthetic heart valves and cause transient ischemic attacks and stroke.9
To prevent and/or treat thromboembolic complications patients are prescribed antiplatelet agents and/or anticoagulants.9 It is of note that antithrombotic therapy should not be interrupted for most dental procedures.24,25 The risk of perioperative and postoperative bleeding complications in patients in whom antiplatelet and anticoagulation therapy is continued is exceedingly small and is outweighed by the small risk of serious and sometimes fatal embolic events when antithrombotic therapy is interrupted.