SERIAL IMPEDANCE PLETHYSMOGRAPHY IN PREGNANT PATIENTS WITH CLINICALLY SUSPECTED DEEP-VEIN THROMBOSIS - CLINICAL VALIDITY OF NEGATIVE FINDINGS

Study objective: To determine the safety of withholding anticoagulant therapy in pregnant patients with clinically suspected deep-vein thrombosis who have negative results by serial impedance plethysmography. Design: Prospective study evaluating prognosis by long-term follow-up to 3 months postpartum in all patients. Setting: University-affiliated community hospital and referral center. Patients: One hundred fifty-two consecutive pregnant patients referred with clinically suspected deep-vein thrombosis. All patients completed the study. Interventions: Anticoagulant therapy was withheld in 139 patients negative by serial impedance plethysmography, and the patients were followed long term. Measurements and Main Results: None of the 139 patients (0%; 95% CI, 0% to 2.6%) had symptomatic pulmonary embolism or recurrent venous thrombosis. Conclusions: The findings establish the safety of withholding anticoagulant therapy in pregnant patients who have negative results after serial impedance plethysmography. Sufficient patients were entered to provide narrow confidence intervals on the outcomes observed in patients with negative findings by impedance plethysmography. These findings are similar to those seen after venography in symptomatic patients. These data extend the role of non-invasive testing in patients with clinically suspected deep-vein thrombosis to the pregnant symptomatic patient.