Summary
Postoperative venous thromboembolic complications are commonly seen after total replacement
of the hip or knee. Recently, an inherited defect with resistance to the anticoagulant
activity of activated protein C (APC-resistance) has been detected. APC-resistance
seems to be a common risk factor, especially in Sweden, and it increases the propensity
for venous thrombosis. This study assesses the prevalence of APC-resistance in a general
population and its clinical significance for patients undergoing surgery associated
with a high risk of thromboembolic complications. In a prospective cohort study, we
analysed for APC-resistance in 645 consecutive patients before elective replacement
of the hip or knee at 3 hospitals in southern Sweden. Thromboprophylaxis with LMWH-heparin
was given to all patients throughout the hospitalisation period. We recorded events
of clinical thromboembolism for 3 months postoperatively. Venography, ultrasonography
or pulmonary scintigraphy was requested by the clinicians according to the existing
routines, i.e. only patients with symptoms of thromboembolism were examined. A thromboembolic
complication was registered in 20 (3.1%) patients. Fifty per cent of the venous thrombi
had a proximal location. Only 0.3% of the patients had verified pulmonary embolism.
APC-resistance was found in 14.1% of the patients, of whom 9.9% had experienced postoperative
thromboembolism compared with 2.0% of the patients without APC-resistance (p <0.0007).
We conclude that APC-resistance is a frequent risk factor for symptomatic postoperative
deep venous thrombosis with an estimated relative risk of 5.0 (95% confidence interval:
from 1.9 to 12.9) in elective replacement of the hip or knee.