The optimal therapeutic range for oral anticoagulant treatment as suggested by fibrinopeptide A (FpA) levels in patients with heart valve prostheses

Early postoperative anticoagulation after mechanical valve replacement: a systematic review

The optimal approach to early postoperative anticoagulation after mechanical valve implantation remains controversial. This review article examines the pathogenesis of thrombus formation and the different strategies for early postoperative anticoagulation. The most commonly reported anticoagulation regimens had the after estimates of early postoperative thromboembolism and hemorrhage: oral anticoagulation alone (0.9%, 3.3%); oral anticoagulation with intravenous unfractionated heparin (1.1%, 7.2%); and oral anticoagulation with low molecular weight heparin (0.6%, 4.8%). Although intravenous heparin may be associated with a higher incidence of hemorrhage, a randomized trial is needed to provide the best evidence regarding early postoperative anticoagulation after mechanical valve implantation. Nearly four decades have passed since the first mechanical prosthetic valves were implanted. Frequent thromboembolic complications with the first mechanical valves led to recommendations of universal anticoagulation for these patients. Since then, several design changes and modifications have been made to improve the longevity, hemodynamics, and thrombogenicity of newer generation mechanical valves. With improved blood flow, less stasis, and less thrombogenic materials, lower rates of thromboembolism have been reported. Despite these advances however, thromboembolism and anticoagulant-related bleeding continue to account for 75% of all complications after mechanical valve replacement. Occurring most commonly within six months after implantation, these complications can adversely affect mortality and quality of life. Furthermore, the threat of their occurrence creates a psychological burden for each patient with a mechanical valve. The need for life-long anticoagulation in patients with mechanical valves is not in dispute, and the perioperative management of anticoagulation during non-cardiac surgery has been reviewed extensively. However, the approach to early postoperative anticoagulation after mechanical valve implantation is still a matter of debate. The optimal intensity and timing of anticoagulation to prevent early thromboembolism after valve replacement surgery without postoperative bleeding complications is unknown. Hence, many anticoagulation protocols have been proposed, but a lack of consensus remains. The objectives of this study were (1) to reexamine the pathogenesis of thrombus formation and the need for anticoagulation; (2) to critically review the literature on early postoperative anticoagulation strategies; and (3) provide an estimate of the incidence of bleeding and thromboembolism for each approach to early postoperative anticoagulation.

Hypercoagulable state under low-intensity warfarin anticoagulation assessed with hemostatic markers in cardiac disorders

The hemostatic condition under low-intensity anticoagulation in cardiac disorders is not fully elucidated. The aim of this study was to ascertain whether hemostatic molecular markers are a useful assessment for anticoagulation to detect the hypercoagulable state. A hematologic study was performed in 75 outpatients, without thromboembolic episodes, treated with low-intensity anticoagulation (average international normalized ratio [INR] 1.72) because of potential cardiac sources of arterial emboli, and in 40 age-matched control subjects. The average level of thrombin-antithrombin III complex (TAT) was significantly lower in patients than in control subjects (p = 0.005), and the mean value of D-dimer was not statistically different between patients and control subjects. Although TAT correlated moderately with D-dimer (r = 0.45, p = 0.0001), INR did not correlate with TAT or D-dimer. Elevated TAT > 3.0 ng/ml and/or D-dimer S 150 ng/ml were observed in 15 patients (20.0%), whereas the remaining 60 patients (80.0%) had no obvious increase in the level of TAT or D-dimer at overall INR. Antithrombin III activity did not correlate significantly with INR, but protein C activity and free protein S antigen showed a significant negative relation to INR (r = 0.82, r = 0.62, respectively, p = 0.0001). Low-intensity anticoagulation was sufficient to reduce coagulation and subsequent fibrinolytic activation in cardiac disorders, but may not be sufficient in some patients with elevated TAT or D-dimer concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Regression of intracardiac thrombus after embolic stroke

Using two-dimensional echocardiography, we studied the pathophysiology of intracardiac thrombus regression accompanied by anticoagulant therapy in 82 consecutive patients with acute cardiogenic cerebral embolism. We noted intracardiac thrombus in 15 patients; nine of the 15 were started on anticoagulant therapy with warfarin potassium to maintain the prothrombin time between 2.5 and 3.5 (international normalized ratio). Serial two-dimensional echocardiograms were obtained for these nine patients before and after anticoagulation, with the plasma levels of fibrinopeptide A, fibrinopeptide B beta 15-42, and D-dimer measured at the same time. In eight of the nine patients the intracardiac thrombi gradually decreased in size while the plasma level of fibrinopeptide A fell to within the normal range and the plasma levels of fibrinopeptide B beta 15-42 and D-dimer remained above the normal ranges. In the other patient the thrombus disappeared, with embolization to the right arm immediately after starting anticoagulant therapy. Mobile or small thrombi regressed earlier than nonmobile or large ones. We conclude that regression of intracardiac thrombi after anticoagulation may be based on the relative predominance of plasma fibrinolytic activity over anticoagulation-inhibited thrombin activity.