Impact of thrombophilia on treatment duration
Among the 36 patients with IT abnormalities, we could evaluate the decisions regarding therapeutic management in only 31 patients. Sixteen (51.6 %) patients pursuit anticoagulation (1 AT deficiency, 2 PC deficiency, 1 protein S deficiency and 11 patients with aPCR). Neither thrombophilia nor clinical characteristics were associated to the decision to pursuit or to stop anticoagulation. Besides, treatment duration was not longer in patients with IT than in those without (12.3 vs 13.3 months; p=0.76). Moreover patients with both idiopathic index VTE and IT were anticoagulated during a period longer than those with both provoked thrombosis and IT (14.6 vs 6 months; p=0.04). Among 5 patients with IT and VTE at unusual site, 3 patients received a prolonged anticoagulation.
Outcomes and recurrences: Among 124 patients followed up, recurrent thrombotic events were reported in 26 patients (21%) (fig 1a). The mean time between Index VTE and the first recurrence was 38.5 months (2.5-144). The mean time between treatment withdrawal and recurrence was 11.7 months (±16.9). Recurrences were reported in 8 patients while on indefinite treatment duration. Analysis of predictors of recurrent VTE showed that recurrences were significantly associated to male gender, smoking, history of previous VTE or cardiovascular events, proximal localization, presence of a persistent risk factor, idiopathic thrombosis and post phlebitic syndrome (Table 2).
Association of thrombophilia with the risk of recurrence: Among patients who were followed up, 29 had IT and 16 developed recurrent events (figure 1b). A recurrent thrombotic event was reported in 6 patients (20.7%) with IT (fig 1b). Three patients with IT and recurrent VTE were on indefinite treatment duration. The cumulative incidence of recurrence associated to IT was 4% and 12% at both 12 and 24 months of follow up; p=0.48. The hazard ratio of recurrent event was 1.45 IC (0.51-4.07) after index VTE and 1.31 IC (0.47-3.63) after treatment withdrawal (table 3). When adjusting for gender, smoking, history of previous thrombotic or cardiovascular events, proximal localization, persistent risk factor/idiopathic thrombosis and post phlebitic syndrome, thrombophilia did not increase the risk of recurrence. Similarly, neither the presence of aPCR nor the deficiencies of natural inhibitors had significantly increased the risk of recurrence compared to patients with a normal IT testing results.