José J. Reyna

Effective risk stratification of surgical and nonsurgical patients for venous thromboembolic disease.

Effective and safe methods of preventing venous thromboembolism (VTE) are now widely available, but a significant proportion of patients develop VTE either because thromboprophylaxis has not been used or because the intensity of thromboprophylaxis is not matched to the level of risk. Thromboembolic risk varies widely according to the clinical setting and presence of underlying risk factors, but VTE may not be suspected even in high-risk patients. Clinical risk factors for VTE include recent surgery, cancer, stroke, previous VTE, immobilization, and advanced age. Recent attention has focused on the role of inherited and acquired molecular factors in determining overall thromboembolic risk. These factors include the classic thrombophilias-deficiencies of antithrombin III, protein C, and protein S-and several newly described molecular risk factors: factor V Leiden, the prothrombin 20210A gene mutation, and hyperhomocysteinemia. Based on emerging knowledge of risk factors, several risk assessment models (RAMs) have been devised that stratify patients according to overall VTE risk, allowing thromboprophylaxis to be tailored appropriately. Compared with older risk assessment formulas, current RAMs are simpler and include specific recommendations for thromboprophylaxis based on the available scientific evidence. Consensus documents on VTE prevention classify patients into low-, moderate-, and high-risk categories. More recently, a new risk group, very high risk, has been described. Very-high-risk patients are especially prone to thromboembolic complications and need intensive and in some cases prolonged thromboprophylaxis.

A guide to venous thromboembolism risk factor assessment

Venous thromboembolism (VTE) remains a widespread clinical problem associated with signi~cant morbidity and mortality. It is estimated that VTE results in 300,000 to 600,000 hospitalizations each year in the United States [1]. Of these patients, 50,000 to 100,000 will die of a pulmonary embolism, which is presently the leading cause of preventable death in hospitalized patients [1,2]. Untreated deep vein thrombosis (DVT) predisposes patients to episodes of recurrent VTE and the development of the postphlebitic syndrome (PTS), which can involve a constellation of symptoms ranging from leg edema, pain, aching and tiredness, to the development of skin discoloration, scarring, and even open ulceration [3–7]. VTE and its post-thrombotic sequelae have a staggering impact on healthcare expenses, costing the United States over one billion dollars annually [8,9]. Surgical patients in particular are at a high risk for DVT since the surgical procedure itself is very traumatic and often accompanied by bed rest that increases venous stasis. Without appropriate prophylaxis, DVT rates range from 45–70% and 15–30% in orthopedic and general surgery patients respectively [2]. For this reason, surgeons should be aware of current guidelines that detail how to appropriately protect their patients from the development of DVT. The rationale for VTE prophylaxis is based on the fact that two-thirds of DVT cases are asymptomatic, and PE is most often clinically silent [3]. In addition, the clinical diagnosis of a DVT or PE is insensitive and unreliable since few of their signs and symptoms are speci~c. Implementation of treatment must be done before the complete clinical picture has developed, since the ~rst manifestation of the disease may be a fatal PE. Unrecognized and untreated DVT may also lead to long-term morbidity related to the development of the post-thrombotic syndrome and future episodes of recurrent VTE. Consequently, prevention is the key to reducing death and morbidity from VTE, and the key to appropriate prophylaxis is risk factor analysis (RFA). Even though the importance of preventing the development of VTE has been emphasized by a number of consensus conference guidelines over the past 20 years, the speci~c recommendations in the guidelines have not been universally adopted into clinical practice [1,10–13]. Various surveys over the past few years have reported wide practice variations in the prevention of VTE, including an under-utilization of prophylaxis and a lack of awareness among physicians of VTE as a problem. In a recent 1998 survey of 1,145 Fellows of the American College of Surgeons, Caprini showed that only 47% and 31% of the responding surgeons were familiar with the 1986 NIH Consensus Conference and the American College of Chest Physicians guidelines respectively [14]. An alarming 90% of the surgeons were not familiar with the 1992 THRIFT Conference or the 1992 European Consensus Conference Guidelines [14]. Some investigators feel that the availability and reinforcement of written protocols, particularly in non-teaching hospitals where VTE prophylaxis is signi~cantly underutilized, may improve the utilization of VTE prophylaxis [15]. It has already been shown that continual medical education (CME) programs and protocol implementation can signi~cantly increase the frequency with which physicians prescribe appropriate methods of VTE prophylaxis [16]. The 1998 Chest Consensus Guidelines emphasized the need for continuing educational programs to increase the use of appropriate prophylactic measures and the importance of risk factor assessment in diagnosing and treating DVT [17]. RFA is essential in surgical patients because prophylaxis is encumbered with risks (e.g., bleeding com-

Venous duplex imaging follow-up of acute symptomatic deep vein thrombosis of the leg

PURPOSE The purpose of this study was to evaluate the rate of resolution of deep vein thrombosis (DVT) in the leg, by means of duplex imaging, in patients with symptoms during a 6-month period after initial diagnosis. METHODS Seventy-three limbs in 69 patients with acute DVT diagnosed by duplex imaging received conventional heparin and warfarin treatment and underwent subsequent duplex studies 1, 4, 12, and 24 weeks after the initial diagnosis. The objectives of the study were to document (1) the rate or complete resolution of DVT, (2) the proportion of unstable, floating thrombi, and (3) the development of chronic damage as a result of vessel wall scarring. RESULTS The rate of normalization of DVT 6 months after diagnosis was 78% in the common femoral vein, 70% in the superficial femoral vein, 75% in the popliteal vein, and 70% in the calf veins examined at the scheduled intervals. Twenty-six percent of thrombi were considered unstable on the baseline examination. The average number of days necessary for these thrombi to become stable was 10.7 days. Damage to the vessel wall or valves was documented in 44% of the patients. CONCLUSIONS Rates of resolution of DVT were similar for the different veins of the leg studied. There was a high proportion of unstable thrombi, which present a high potential risk of embolization. Serial duplex scanning after DVT renders important information with regard to thrombus resolution, propagation, and attachment to the vein wall.

The influence of oral anticoagulation therapy on deep vein thrombosis rates four weeks after total hip replacement

PURPOSE The purpose of this study was to assess the rate of postoperative deep vein thrombosis (DVT) as a function of oral anticoagulation therapy after total hip replacement surgery. METHODS A total of 125 patients completed the study. All the patients received sequential gradient pneumatic compression over elastic stockings until hospital discharge. In addition, all the patients underwent postoperative heparin therapy followed by oral warfarin therapy, adjusted in dose to maintain a goal international normalized ratio (INR) level of 2.0 to 3.0. Warfarin therapy and compression stockings were continued for 1 month after surgery. Bilateral duplex scanning was performed 1 and 4 weeks after surgery to assess the rate of DVT. RESULTS Nineteen of the 125 patients had DVT develop (15.2%). Of those thromboses, six (31.6%) and 13 (68%) were detected 1 week and 1 month after surgery, respectively. The rate of proximal DVT was 2.4% (3 of 125) 1 week after surgery and rose to 8.2% (10 of 122) 1 month after surgery. Most DVT cases (64%; 12 of 19) were asymptomatic. The patients in whom DVT developed had significantly lower INR values during the second to fourth postoperative weeks than did those patients without thrombosis, and no differences in INR values were found during the first postoperative week. CONCLUSION The risk of the development of DVT extends beyond hospital discharge in patients who undergo total hip replacement, despite a regimen of prolonged oral anticoagulation therapy. This is particularly true in patients whose INR values did not reach therapeutic range during the first postoperative month. Therefore, thrombosis prophylaxis regimens on the basis of the administration of warfarin should try to maintain INR values within therapeutic range during the entire first postoperative month to minimize the incidence of DVT.

Deep vein thrombosis outcome and the level of oral anticoagulation therapy

OBJECTIVE The purpose of this study was to assess the rate of deep vein thrombosis (DVT) resolution and DVT outcomes as functions of the level of oral anticoagulation therapy achieved with warfarin. METHODS In 33 consecutive patients, a series of 35 limbs with acute symptomatic DVT was followed throughout 1 year of anticoagulation therapy. All the patients underwent 5 days of intravenous unfractionated sodium heparin therapy that was adjusted in dose to prolong the activated thromboplastin time to 2.0 to 2.5 times the control. In addition, warfarin was administered for a period of 6 months, with a target international normalized ratio (INR) between 2.0 and 3.0. All the patients underwent venous duplex scanning and physical examination at the time of diagnosis and at 1 week, 1 month, 3 months, 6 months, and 1 year. RESULTS At the end of the 1-year study period, the rate of complete DVT resolution was 68%. The median INR values in patients with complete DVT resolution were significantly higher than those of patients with incomplete DVT resolution after 1, 3, and 6 months of treatment with warfarin. In addition, the proportion of patients with INR values below therapeutic range was significantly higher in patients with incomplete DVT resolution than in patients with complete DVT resolution after 1, 3, and 6 months of treatment with warfarin. The presence of occlusive thrombi was associated with incomplete DVT resolution. Of the patients with occlusive thrombi, 62% had chronic venous insufficiency symptoms develop, whereas only 11% of the patients with nonocclusive thrombi (P =.003) had these symptoms develop. CONCLUSION Despite 6 months of oral anticoagulant therapy, almost one third of thrombi did not resolve completely. The INR values were significantly higher in those patients with complete DVT resolution. These results suggest that the maintenance of an INR level between 2.0 and 3.0 throughout oral anticoagulation therapy will minimize the rate of incomplete DVT resolution.