Lisette van Dam

Chapter 2 22 MRDTI results Of the 305 study patients, 189 patients (62%) had a MRDTI negative for DVT ( Figure 2 ). Of the 189 patients, 122 patients (65%) had a MRDTI negative for both DVT and thrombophlebitis and were off anticoagulant treatment at inclusion. These patients were left untreated. The MRDTI was negative for DVT but positive for superficial thrombophlebitis in 14 patients (7.4%). Twelve of these were treated with a short course of half- therapeutic dosed anticoagulants, while one patient was treated with short course of therapeutic dosed anticoagulants. One patient diagnosed with superficial thrombophlebitis was on anticoagulant treatment at time of inclusion and treatment was modified. The remaining 53 patients (28%) were on anticoagulants at inclusion and continued with unmodified treatment as per previous indication. Two of the 305 patients (0.66%) had an inconclusive MRDTI; one patient due to imaging artefacts secondary to a knee prosthesis and one patient with a venous iliac stent in whom the stent could not be visualized. Both patients were considered to have recurrent DVT based on elevated D-dimer and ultrasound results. MRDTI could not be performed in two additional patients: one due to extreme pain and one due to claustrophobia. These two patients were also judged to have recurrent DVT based on available diagnostic tests. One patient was incorrectly included and had both suspected recurrent DVT and acute PE at baseline; CTPA confirmed acute PE and treatment was started before MRDTI of the leg could be performed (which was considered as a protocol deviation). A total of 111 patients (36%) had a MRDTI positive for DVT, of whom 99 patients were off anticoagulant treatment at the time of inclusion into the study and started anticoagulant treatment ( Figure 2 ). Twelve patients were on anticoagulants at the time of study inclusion and their treatment was modified after diagnosis. Thus, the overall prevalence of recurrent DVT at baseline, including 111 patients with a MRDTI positive for DVT and the abovementioned 5 patients with recurrent VTE diagnosed otherwise, was 38% (116/305). The baseline prevalence of recurrent DVT in patients on anticoagulants at inclusion was 21% (14/68; Figure 2 ). Figure 3 shows examples of MRDTI images of three individual patients in which a clear high signal intensity is seen in case of an acute thrombus and a symmetrical low signal intensity in the absence of an acute thrombus.