Thermography in the Diagnosis of DVT

The duration of oral anticoagulation after deep vein thrombosis. A randomized study

Eighty patients with deep vein thrombosis (DVT) were randomized between our routine duration of oral anticoagulation and 50% reduction thereof, in order to evaluate whether shorter therapy could be given without increased risks. The study was stratified, so that 20 patients with the 1st episode of DVT caused by a temporary risk factor were treated for 1.5 or 3 months, 40 patients with the 1st episode of DVT caused by a permanent risk factor for 3 or 6 months, and 20 patients with the 2nd episode of DVT for 6 or 12 months. When warfarin therapy was discontinued, the patients were followed by means of venous occlusion plethysmography every 3 months for 1 year, and clinically for 15-27 months in the different subgroups. Thromboembolic complications were registered and verified by venography and perfusion lung scan. We could not detect any difference between the groups. The rate of rethrombosis and embolism during 12 and 24 months after cessation of anticoagulant therapy was 8 and 10%, respectively, among the patients with reduced duration of treatment and 8 and 14%, respectively, among those with regular duration. One fatal, warfarin-induced hemorrhage occurred. It is important to reduce unnecessary extension of oral anticoagulation after DVT in order to minimize the negative side-effects without increasing the recurrence rate. More extensive trials should be performed to confirm our results and define the optimal duration of treatment.

One-year sequential follow-up of venous emptying rate and leg temperature profiles after acute deep vein thrombosis

In order to study the natural course of venous flow and temperature reaction in the legs after symptomatic first episode of deep vein thrombosis (DVT), 65 patients (57 with proximal DVT) without further thromboembolic complications during the observation period were followed for 1 year by repeated plethysmography (PG) and thermography (TG). Regarding the non-invasive parameters substantial individual variations was observed during the observation period. After 1 year pathologic PG and TG were still demonstrated in 39% (I mu (95%) = /0.43 +/- 0.05/) and 65% (I mu (95%) = /1.18 +/- 0.11/), respectively, of the patients after proximal DVT. Only a minority of the patients were normalized permanently in both PG and TG during the first year. The high frequency of remaining venous obstruction and especially, persistent thermoactivity is notable and may be of clinical importance.

Thermography and plethysmography, a non-invasive alternative to venography in the diagnosis of deep vein thrombosis

One plethysmographic and two thermographic methods were evaluated against venography in 102 patients with suspected deep vein thrombosis (DVT). Seventy-one patients had venographically verified DVT, which in 21 cases was restricted to the calf. Plethysmography (PG) gave a sensitivity and specificity of 63% and 94%, respectively. The former was influenced by a limited sensitivity of 14% in the sub-group with distal DVT. The sensitivity and specificity of temperature profiles (TP) were 87% and 39%, respectively, while the corresponding values for thermo-camera (TC) were 83% and 55%, respectively. Using a combined diagnostic approach of PG and TP, additional evaluation of posterior and lateral profiles and pattern recognition, 96% sensitivity and 81% specificity were reached. The combination of PG and TP will be an essential diagnostic complement when venography is not possible or inconclusive, as well as having a role in diagnostic screening in a large number of patients.