Background:HRI is a new Doppler index of vascular resistance – HRI=D/S.The aim of the study is to evaluate diagnostic significance of HRI calculated from the Doppler spectrum of popliteal arteries in patients with systemic lupus erythematosus (SLE) with and without secondary antiphospholipid syndrome (SAPS) compared with healthy controls.Material/Methods: During 9-month period (May 2003 –January 2004), 93 patients (81 women and 12 men) with SLE (including 24 patients with SAPS) and 30 healthy controls (24 women and 6 men) underwent bilateral duplex Doppler examinations of lower limb arteries. The examinations were performed using HDI 3500 (ATL) with 5 –12 MHz linear transducer under standardized conditions: correct insonation angle and sample volume size, with the patient in a supine position, after 10 minutes rest.Results: Mean HRI value obtained in the control group was 0.415 (range 0.305 –0.555; median 0.402). In the group of SLE patients without SAPS, mean HRI value was decreased to 0.320 (range 0 –0.584;median 0.334) and even lower –0.283 in SLE patients with SAPS (range 0.106 –0.545; median 0.291).Conclusions: Small arteries, arterioles and capillaries are the main affected vessels in SLE. This chronic process stimulates circulation through lower resistance collaterals, decreasing HRI value. The Doppler HRI calculation can be valuable in early diagnosis and monitoring of lower extremity vascular changes in patients suffering from SLE with and without SAPS.

Keywords: Vascular Resistance, Doppler ultrasound, systemic lupus erythematosus, Antiphospholipid Syndrome