Blood rheology in deep venous thrombosis - relation to persistent and transient risk factors

Introduction: The risk of recurrence in patients with symptomatic deep venous thrombosis (DVT) is higher in patients with persistent risk factors than in patients with transient risk factors. The purpose of this prospective study was to investigate the course of rheological variables in patients with DVT up to I year after the acute event in relation to risk factors. Patients and methods: In 37 patients with proven DVT plasma fibrinogen, plasma viscosity, red cell aggregation, whole blood viscosity, hematocrit and platelet aggregation were studied in the acute phase, at 6 weeks and at 12 months. Results: In the acute phase, patients had higher fibrinogen (medians and ranges; 450 [270-611] vs. 247 [170-340] mg/dl, p < 0.01), plasma viscosity (1.67 [1.48-1.96] vs. 1.60 [1.50-1.70] mPa s, p < 0.01), red cell aggregation (9.76 [5.87-12.66] vs. 5.66 [3.67-8.46] arbitrary units; p < 0.01) and whole blood viscosity (5.78 [5.61-5.87] vs. 5.59 [5.27-5.9] mPa s, p < 0.01), but lower hematocrit (40 [32-46] vs. 45 [38-50]%, p < 0.01) and platelet aggregation (by epinephrine: 41 [13-85] vs. 79 [29-91]%, (p < 0.01) than controls. During the I-year follow-up, fibrinogen, plasma viscosity, red cell aggregation and whole blood viscosity constantly decreased, whereas hematocrit and platelet aggregation increased in the total of patients (all p < 0.01). Subgroup analysis according to risk factors showed that at 12 months patients with persistent risk factors (N = 21) had higher plasma fibrinogen (357 [235-450] vs. 247 [214-335] mg/dl, p < 0.01), plasma viscosity (1.65 [1.50-1.80] vs. 1.59 [1.42-1.77] mPa s, p < 0.05) and red cell aggregation (7.82 [6.0-11.3] vs. 6.3 [5.2-7.1] arb. units, p < 0.01) than patients with transient risk factors (N = 16). Compared with controls, these variables were increased in patients with persistent risk factors (all p < 0.01), but not in patients with transient risk factors (all n.s.). Conclusion: In patients with persistent risk factors rheological changes are still present I year after acute DVT, whereas in patients with transient risk factors blood rheology returns to normal. Further studies are needed to clarify whether blood rheology might be helpful to identify patients at high risk of recurrence. (C) 2002 Elsevier Science Ltd. All rights reserved.