Time taken to the maximum increase in the oxygenated hemoglobin level in calf muscle as a predictor of mild and moderate post-thrombotic syndrome.

BACKGROUND: Near-infrared spectroscopy (NIRS) allows continuous noninvasive monitoring of changes in the tissue levels of oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) and can identify the severity of chronic venous diseases. Here we investigated the predictors of post-thrombotic syndrome (PTS) using NIRS in patients with a first episode of deep venous thrombosis (DVT).

METHODS: The study enrolled 129 patients with DVT. Risk factors in each patient were assessed at presentation. Venous abnormalities confirmed by ultrasound and parameters derived from NIRS were evaluated at 6 months after DVT. On standing, increases in O2Hb and HHb (ΔO2Hbst and ΔHHbst) and the times taken for each concentration to become maximal (TO2Hbst, and THHbst) were measured. During 10 tiptoe movements, O2Hb showed a continuous decrease (ΔO2Hbex), whereas venous expulsion (ΔHHbEex) and subsequent retention (ΔHHbRex) were observed. The oxygenation index (HbD; HbD = O2Hb - HHb) was also calculated at the end of standing and at the end of 10 tiptoe movements (ΔHbDst and ΔHbDex). Final clinical manifestations were evaluated at 6 years, and PTS was considered to be present if the Villalta score was ≥5.

RESULTS: Thirteen patients were excluded and 116 patients were finally included. Of these, 19 (16%) developed PTS. Among various NIRS-derived parameters, TO2Hbst had the highest area under the curve (0.88; 95% confidence interval [CI], 0.80-0.93; P < .01) with the best cutoff value (TO2Hbst ≤48 seconds). On univariate analysis, variables associated with greater risk for development of PTS were stroke (odds ratio [OR], 5.59; 95% CI, 0.74-42.41; P = .06), idiopathic DVT (OR, 4.13; 95% CI, 1.36-12.55; P < .01) and iliofemoral DVT (OR, 4.31; 95% CI, 1.48-12.60; P < .01) at initial presentation, venous occlusion combined with reflux (OR, 4.24; 95% CI, 1.50-12.00; P < .01), and NIRS-derived TO2Hbst ≤48 seconds (OR, 43.03; 95% CI, 9.04-204.81; P < .01) at 6 months. Multivariate logistic regression analysis finally revealed venous occlusion combined with reflux (OR, 4.80; 95% CI, 1.03-22.36; P < .05) and NIRS-derived TO2Hbst ≤48 seconds (OR, 53.73; 95% CI, 8.43-342.41; P < .01) to be independently associated with PTS progression.

CONCLUSIONS: NIRS-derived TO2Hbst ≤48 seconds is a promising time-course predictor of PTS progression.