High HDL reduces the risk of recurrent venous thromboembolism

Patients who have previously suffered a venous thromboembolism (VTE) but have high levels of HDL and apolipoprotein A-I (apoA-I), the main lipoprotein in HDL, have a lower risk of recurrent episodes, according to the results of a study published in Circulation, March 2007.1

VTE is a frequent and potentially fatal condition. While dyslipidaemia and dyslipoproteinaemia are well-established risk factors for arterial atherothombosis, little is known about dyslipoproteinaemia in VTE.

In this study, 772 patients (332 men and 400 women, mean age 47 years) were followed-up after their initial VTE for a median of 48 months. Blood samples were taken at intervals throughout the follow-up period to evaluate plasma levels of apoA-I and B, and nuclear magnetic resonance was used to measure levels of lipoprotein subclasses and HDL cholesterol.

Recurrent VTE was reported in 100 of these 772 patients. Patients with a recurrent VTE had lower mean levels of apoA-I (p<0.001) although similar levels of apoB compared with patients who did not have a recurrent episode. Compared with patients with apoA-I levels in the lowest tertile (<1.07 mg/mL), the relative risk of VTE recurrence was 0.46 (95%CI 0.27-0.77) for patients in the highest tertile (>1.30 mg/mL).

Using a Cox proportional hazard model, the relative risk of recurrence was 0.87 (95%CI 0.80 to 0.94) for each 0.1 mg/mL increase in plasma levels of apoA-I, and this was unchanged even after adjustment for age and sex. Kaplan-Meier analysis showed that the cumulative probability of recurrence after 4 years was 8.8% (95%CI 4.6% to 12.9%) in patients with apoA-I levels > 1.3 mg/mL compared with 18.7% (95%CI 13.1% to 24.3%) in patients with apoA-I levels <1.07 mg/mL.

In a subset of 71 patients with a recurrent VTE episode and 142 matched patients without recurrence, there was evidence of a strong trend for association between recurrence and low levels of large HDL particles (p=0.07) and HDL cholesterol (p=0.04). The researchers concluded that evidence from the study showing that patients with high levels of apoA-I, HDL cholesterol and large HDL particles have a lower risk of recurrent VTE, justifies study of the effect of different strategies for raising HDL on VTE risk.

Reference

1. Eichinger S, Pecheniuk NM, Hron G et al. High-density lipoprotein and the risk of recurrent venous thromboembolism. Circulation 2007;115:1609-14.

Commentary

Venous thromboembolism (VTE) is a growing public health problem. In this context, it is of special relevance that low levels of apo AI are associated with a twofold increase in the risk of recurrence of VTE after 4 years. Monitoring circulating apoAI levels in VTE patients is clearly of major significance for evaluation of risk and of their response to potential therapeutic intervention to raise HDL levels.