Prognostic impact of calf muscle near-infrared spectroscopy in patients with a first episode of deep vein thrombosis

Unraveling the pathophysiology of lower-limb postthrombotic syndrome in adolescents: a proof-of-concept study

A better understanding of the pathophysiology of pediatric postthrombotic syndrome (PTS) is needed to develop strategies to treat this condition. We investigated calf pump function, exercise capacity, balance in power output, and changes in limb muscle oxygen saturation (SmO2) and fluid content during exercise in 10 pediatric patients with unilateral lower-limb PTS, and in age- and sex-matched controls (1:1-1:2 ratio). Outcomes were investigated using bioimpedance spectroscopy, torque-sensing pedals, and near-infrared spectroscopy during incremental- and constant-load cycling tests. The median age at participation was 17 years (25th-75th percentile, 15-18 years); 68% of participants were females. The median CAPTSure score in the affected leg of affected participants was 35 points (25th-75th percentile, 24-46 points), indicating moderate/severe PTS; 20% of patients had a history of central venous catheter-related thrombosis. Increasing PTS severity was associated with higher calf pump venous volume and higher ejection volume, leading to compensated calf pump performance. We found no evidence of PTS impact on exercise capacity. Leg contribution to power output was similar in affected and unaffected legs. However, the PTS-affected legs showed lower SmO2 during active cycling and recovery with increasing PTS severity, indicating impaired microvascular function in the muscle. These findings suggest that PTS severity is associated with impaired blood flow, presumably from elevated venous pressure during and after exercise. The fact that microvascular function is impaired in young patients with PTS underscores the relevance of developing strategies to mitigate the effects of this chronic vascular disease to minimize its deleterious effects as children grow older.

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.

Measurements of calf muscle oxygenation during standing and exercise in patients with primary valvular insufficiency

OBJECTIVE

Despite the established role of the calf muscle pump for preventing chronic venous disorders, hemoglobin flow in the calf muscle is poorly understood. Near-infrared spectroscopy (NIRS) provides continuous noninvasive monitoring of changes in tissue-oxygenated hemoglobin (O2Hb) and deoxygenated hemoglobin (HHb) levels. The purpose of this study was to investigate the changes in calf muscle O2Hb and HHb levels during standing and exercise in patients with primary valvular insufficiency (PVI).

METHODS

Eighty-three limbs in 81 patients with PVI were enrolled. The clinical manifestations of these patients were categorized according to the CEAP (Clinical, Etiologic, Anatomical, and Pathophysiologic) classification, and patients were divided into group I (C1-3S,Ep,As,d,p,Pr) and group II (C4-6S,Ep,As,d,p,Pr). Moreover, to assess the severity of PVI, the revised Venous Clinical Severity Score (VCSS) was employed. NIRS was used to measure changes in the calf muscle O2Hb and HHb levels. On standing, increases in O2Hb and HHb were calculated by subtracting the baseline value from the maximum value (ΔO2Hbst and ΔHHbst). The time elapsed until the maximum increases in O2Hb and HHb concentrations (TO2Hbst, and THHbst) were also measured. During 10 tiptoe movements, the relative change in O2Hb was calculated by subtracting the value measured at the end of exercise from the value measured at the beginning of exercise (ΔO2Hbex). On the other hand, 10 tiptoe movements produced venous expulsion (ΔHHbEex) and a subsequent retention (ΔHHbRex). The oxygenation index (HbD; HbD = O2Hb - HHb) was also calculated at the end of standing and 10 tiptoe movements (ΔHbDst and ΔHbDex).

RESULTS

Among the 83 limbs evaluated, 48 were classified as group I and 35 as group II. Standing caused increases in the levels of both ΔO2Hbst and ΔHHbst. However, there were no significant differences in these increases between the two groups. In contrast, the TO2Hbst was significantly reduced in group II in comparison with group I (55 ± 29 vs 36 ± 30 seconds; P = .007). During 10 tiptoe movements, a decrease in O2Hb concentration was observed, and there was no significant difference in ΔO2Hbex between group I and group II. In contrast, the ΔHHbRex was significantly increased in group II compared with group I (6 ± 7 vs 9 ± 6 μmol/L; P = .013). Furthermore, falls in ΔHbDex were more pronounced in group II (7 ± 16 vs -7 ± 16 μmol/L; P = .001). A statistically significant correlation was found between C of CEAP and the VCSS (r = 0.778; P < .001). Moreover, NIRS-derived TO2Hbst (r = -0.312; P < .01) and ΔHbDex (r = -0.332; P < .01) showed moderate inverse correlations with C of CEAP. Similarly, NIRS-derived ΔHbDex (r = -0.501; P < .001) had a strong inverse correlation, and ΔHbDst (r = -0.383; P < .001) and TO2Hbst (r = -0.378; P < .001) had moderate inverse correlations with VCSS.

CONCLUSIONS

Changes in O2Hb and HHb concentrations differ according to CEAP manifestation and VCSS. These data offer new insights into calf muscle hemodynamics at the microcirculation level in patients with PVI.

Scoring systems for the post-thrombotic syndrome

OBJECTIVE

To assess each of the scoring systems used to diagnose and classify post-thrombotic syndrome, a common chronic complication of deep vein thrombosis. The design of the study was a systematic review of the literature pertaining to post-thrombotic syndrome.

METHODS

A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines by a search of PubMed (1948 to September 2011) using the search terms "post-thrombotic syndrome," "postthrombotic syndrome," "post-phlebitic syndrome," and "postphlebitic syndrome." A manual reference list search was also carried out to identify further studies that would be appropriate for inclusion. The various scoring systems in use were identified and assessed against a list of criteria to determine their validity for use. For outcome measures, each scoring system was assessed for specific criteria, including interobserver reliability, association with ambulatory venous pressures, ability to assess severity of post-thrombotic syndrome, ability to assess change in condition over time, and association with patient-reported symptom severity.

RESULTS

The Villalta, Ginsberg, Brandjes, Widmer, CEAP, and Venous Clinical Severity Score systems all were assessed for the stated outcome measures. From their use in the literature, only the Villalta score was able to fulfill all the criteria described. The main criticism of the Villalta score in the literature appears to be its use of subjective measures. To that end, we propose that use of a venous disease-specific quality-of-life questionnaire in combination with the Villalta score may help standardize the subjective criteria.

CONCLUSIONS

The Villalta score, combined with a venous disease-specific quality-of-life questionnaire, should be considered the "gold standard" for the diagnosis and classification of post-thrombotic syndrome.

Changes in calf muscle deoxygenation after foam sclerotherapy in patients with superficial venous insufficiency

OBJECTIVE

This study assessed changes in the calf muscle deoxygenated hemoglobin (HHb) level during light-intensity exercise after ultrasound-guided foam sclerotherapy (UGFS) for superficial venous insufficiency.

METHODS

UGFS with 1% or 3% polidocanol foam (POL-F) was used to treat unilateral great saphenous vein reflux in 84 patients. Near-infrared spectroscopy (NIRS) was used to measure calf muscle HHb levels before and 3 months after UGFS. The calf venous HHb blood-filling index was calculated on standing, the calf venous HHb ejection index was obtained after one tiptoe movement, and the venous HHb retention index was obtained after 10 tiptoe movements. The primary end point was an evident improvement in calf muscle deoxygenation after UGFS. The secondary end point was obliteration of the great saphenous vein.

RESULTS

Treatment consisted of 1% POL-F in 48 limbs and 3% POL-F in the remaining 36. Ultrasound imaging at the 3-month follow-up demonstrated complete occlusion in 56.3% of the patients who received injections of 1% POL-F and in 66.7% of those who received injections of 3% POL-F. The difference in treatment outcome between the groups was not significant (P=.333). Reflux was absent in 39 limbs (81.3%) treated with 1% POL-F and in 34 limbs (94.4%) treated with 3% POL-F, and no significant difference was observed between the two groups (P=.076). Postsclerotherapy NIRS demonstrated significant reductions in the levels of the HHb filling index in both treatment groups (P=.039, P=.0001, respectively) and significant reductions in the levels of the HHb retention index (P<.0001, P=.008, respectively). However, the differences in the levels of the HHb ejection index before and after UGFS were not significant (P=.250, P=.084, respectively).

CONCLUSIONS

Our present findings suggest that changes in the values of these parameters may be of potential use for assessing the effects of foam sclerotherapy in patients with superficial venous insufficiency.

Factors predicting development of post-thrombotic syndrome in patients with a first episode of deep vein thrombosis: preliminary report

OBJECTIVE

To investigate the indicative parameters reflecting the progression of post-thrombotic syndrome (PTS) in patients with a first episode of deep vein thrombosis (DVT).

DESIGN AND METHODS

The patients' initial risk factors were assessed at presentation. Venous occlusion, and reflux and reflux parameters were evaluated at 6 months using venous duplex scanning. Near-infrared spectroscopy (NIRS) was also used to measure calf muscle deoxygenated haemoglobin levels at 6 months. Clinical manifestations were categorised using the clinical, etiologic, anatomic and pathophysiologic (CEAP) classification for chronic venous insufficiency (CVI), and the patients were divided into those having no PTS (C(0-3S),E(s),A(s,d,p),P(r,o)) and those having PTS (C(4-6S),E(s),A(s,d,p),P(r,o)).

RESULTS

Of the 121 patients evaluated, 25 (21%) developed PTS with a mean follow-up period of 66 months. At initial presentation, ilio-femoral DVT (odds ratio (OR) 3.4, 95% confidence interval (CI) 1.4-8.6) was associated with development of PTS. At 6 months, venous occlusion combined with reflux (OR 4.4, 95% CI 2.9-20.7), peak reflux velocity >29.7 cm s(-1) (OR 13.7, 95% CI 4.1-45.7) and mean reflux velocity >8.6 cm s(-1) (OR 4.4, 95% CI 1.5-12.9) in the popliteal vein detected by duplex scanning were strong predictors of PTS. NIRS-derived retention index >3.5 was the strongest predictor of PTS at 6 months (OR 67.4, 95% CI 14.3-318.1).

CONCLUSIONS

Ilio-femoral DVT is associated with the development of PTS at initial presentation. By contrast, occlusion and reflux, high reflux velocity in the popliteal vein and increased NIRS-derived retention index are important time-course predictors of PTS progression.