Prospective 12-year follow-up study of clinical and hemodynamic sequelae after deep vein thrombosis in low-risk patients (Zürich study)

BACKGROUND

No prospective study of the long-term sequelae of more than 10 years after acute deep vein thrombosis exists so far. Therefore, 58 low-risk patients with DVT were included in a prospective study to evaluate the natural history of postthrombotic syndrome.

METHODS AND RESULTS

Clinical and hemodynamic examinations were performed at the time of admission; after 3, 6, and 12 months; after the 2nd, 3rd, 4th, 5th years; and finally after the 12th year. All patients received heparin initially and oral anticoagulants subsequently. After 12 years, 64% of the patients exhibited normal findings. Mild skin changes were found in 28%, marked trophic changes in 5%, and only one venous ulcer occurred. Regular use of compression stockings was reported by 54% of the patients with multilevel thrombosis. Although mean maximum venous outflow was significantly reduced from the acute event to 12 years later (P<.003) compared with the contralateral leg, a significant (P<.05) improvement was observed 6 months later. Recanalization of calf vein thrombosis was detected by Doppler sonography after 3 months. Sixty-four percent of the multilevel thromboses were recanalized completely or in part after 1 year; in 69%, valvular incompetence was found.

CONCLUSIONS

In contrast to earlier reports, this prospective study up to 12 years after deep vein thrombosis demonstrates a low incidence of postthrombotic syndrome by administration of oral anticoagulants and regular compression therapy. However, the adverse clinical event rate (mortality 14%) and a recurrence rate of 24% show that the prognosis after deep vein thrombosis does not appear favorable even in low-risk patients.

[Rhythmic lymph extravasation from a lymph fistula]

A 66-year-old woman with a chronic traumatic lymph fistula is described. Using the almost atraumatic fluorescence micro-lymphography the fistula could be precisely localized within the ulcer. Lymph flow from deep channels was rhythmic. This previously unknown phenomenon of rhythmic retrograde flow in a lymphatic fistula is probably due to the activity of contractile segments of lymph collectors and an important factor for the non-healing of ulcers.

Flow velocity of single lymphatic capillaries in human skin

The purpose of this study was to investigate the previously unknown flow velocity in single lymphatic capillaries of humans in the supine position. Fifteen healthy subjects (10 women and 5 men; mean age 35.8 +/- 13.1 yr) were studied. Ten microliters of fluorescein isothiocyanate-dextran (150,000 mol wt) were injected into the subepidermal layer of the foot dorsum. The filling of the microlymphatics from the resulting depot was visualized by fluorescence video microscopy and stored on videotape. Flow velocity in the microlymphatics was determined on the video screen by direct measurement of the advancement of dyed lymph during a given time. The following median velocities were obtained: 0.51 mm/s (0.27 and 0.61 mm/s for lower and upper quartiles, respectively) for velocity during initial network filling and 9.7 microns/s (6.9 and 14.2 microns/s for lower and upper quartiles, respectively) for resting velocity at the end of the filling period. Mean lymphatic capillary diameter was 54.8 +/- 8.2 microns, and mean network extension was 8.3 +/- 3.2 mm. The high filling velocities are probably due to increased interstitial pressure and volume caused by dye microinjection, whereas the values measured during the end of network filling seem to approach resting flow velocities.

Simultaneous measurement of digital artery and skin perfusion pressure by the laser Doppler technique in healthy controls and patients with peripheral arterial occlusive disease

OBJECTIVE

To assess feasibility of a new technique for simultaneous measurement of digital artery and skin perfusion pressure at the same digit using the laser Doppler method and to measure the pressure gradient between the two vessel compartments in controls and patients with peripheral arterial occlusive disease.

DESIGN

A pressure cuff wrapped around the basis of the toe and connected to a Statham transducer is covered by a special plastic capsule. A hole at the distal end of the capsule permits positioning of a laser Doppler probe at the pulp. A second laser Doppler probe is placed on the skin beneath the pressure cuff. Reappearance of pulsatile flux during cuff pressure release detected by the two laser Doppler probes indicated digital artery pressure and skin perfusion pressure on the corresponding pressure curve. Results in patients with intermittent claudication were compared to results of a group of normal controls.

SETTING

University Hospital, Zürich, Switzerland.

MATERIALS

Eleven healthy volunteers and 14 patients with intermittent claudication due to peripheral arterial occlusive disease were studied.

CHIEF OUTCOME MEASURES

Digital artery pressure (DAP), skin perfusion pressure (SPP) and pressure gradient between DAP and SPP.

MAIN RESULTS

Significantly lower mean DAP (95.8 +/- 23.2 mmHg vs. 49.8 +/- 20.4 mmHg; p < 0.01) and mean SPP (81.4 +/- 18.8 mmHg vs. 38.4 +/- 21.7 mmHg; p < 0.01) were observed in the patients. Mean pressure gradients and ratios between DAP and SPP did not differ significantly between the two groups. There was a linear correlation between DAP and SPP (r = 0.82, p < 0.01).

CONCLUSION

The laser Doppler method provides the possibility to measure digital artery and skin perfusion pressure simultaneously at the same digit in an easy and non-invasive way. Pressure gradients between DAP and SPP are similar in controls and patients with claudication.

Effects of monoionic and nonionic radiographic contrast media on cutaneous microcirculation in patients with peripheral arterial occlusive disease

The purpose of the study was to compare the in vivo effects of two low-osmolar radiographic contrast media, a monoionic (sodium/-meglumine ioxaglate, Hexabrix) and a non-ionic one (iopromide, Ultravist 300) on the cutaneous microcirculation in patients with peripheral arterial occlusive disease in a prospective randomised double-blind study. In 20 patients with peripheral arterial occlusive disease scheduled for percutaneous transluminal angioplasty skin microcirculation was assessed by laser Doppler fluxmetry and transcutaneous oxygen tension measurements at the foot dorsum for continuous recordings of the cutaneous microvascular perfusion and skin oxygenation. Before angioplasty 10 ml nondiluted contrast medium was injected intraarterially and the acute effect on transcutaneous oxygen tension and laser Doppler flux was registered. Mean laser Doppler flux and oxygen tension were evaluated initially, after arterial puncture and after contrast medium injection. In addition, flux motion was analysed with respect to frequency and amplitudes changes. No significant changes in laser Doppler flux and fluxmotion patterns were found between both groups after contrast medium injection. However, mean transcutaneous oxygen tension of the patients receiving monoionic ioxaglate dropped significantly (P = 0.01). The differences of both contrast media on red blood cell aggregation shown in vitro do not correlate to intravital microcirculatory measurements in patients with arterial occlusive disease of the lower limb. Microvascular skin blood flow and flux motion at the foot in these patients do not change significantly after intraarterial injection of ioxaglate and iopromide. However, oxygen supply of the skin is transient impaired after interarterial injection of the anionic contrast agent ioxaglate, which was not associated with clinical symptoms.

Skin capillary aneurysms detected by indocyanine green in type I diabetes with and without retinal microaneurysms

Functional diabetic microangiopathy of skin vessels is well known (decreased reactivity of arterioles to various stimuli, increased capillary pressure and permeability). In contrast to conventional capillaroscopy, recently introduced infrared fluorescence videomicroscopy with indocyanine green allows one to depict capillary aneurysms, even when filled with plasma alone. Seventeen healthy volunteers (mean age 37.7 years), 14 patients with type I diabetes without (31.3 years) and 17 with retinal microaneurysms (46.8 years) were studied. The mean duration of diabetes in patients without retinal microaneurysms was 14.2 years (4-36 years) and in those with retinal microaneurysms 21.5 years (8-49 years). Nailfold capillary aneurysms were present in 3 of 17 healthy controls, in 7 of 14 patients without and in 10 of 17 patients with retinopathy. Patients with type I diabetes with and without retinopathy exhibited significantly more skin microaneurysms (p < 0.05 and < 0.005, respectively) than the controls. The prevalence in the patients with retinal microaneurysms tended to be even higher. Skin capillary aneurysms, which may be depicted in vivo by sophisticated infrared fluorescence videomicroscopy, even when filled by plasma alone, are an important morphological feature of diabetic microangiopathy.

Microvascular changes in chronic venous insufficiency--a review

Chronic venous insufficiency is the result of an impairment of the main venous conduits, causing microvascular changes. The driving force responsible for the alterations in the microcirculation is probably the intermittently raised pressure propagated from the deep system into the capillaries. The capillaries are dilated, elongated and tortuous and their endothelium is injured (irregular luminal surface, increased cytopempsis, dilated interendothelial spaces). Through the latter an increased extravasation can be observed, leading to an enlarged pericapillary space, oedema in the interstitial tissue and to the clinical finding of swelling. Haemoglobin from extravasated erythrocytes and erythrocyte fragments in the pericapillary space is degraded to haemosiderin which is responsible for hyperpigmentation. Microthrombosis in the capillaries causes microinfarction and micronecrosis. Skin areas with severe microangiopathy have reduced numbers of perfused nutritional capillaries and are characterized by a low transcutaneous (tc) PO2. The increased blood flow in the deeper skin layers does not contribute to nutrition of the superficial skin layers. The microvascular ischaemia is patchy and appears to be the main factor determining trophic changes and venous ulceration. The process of microinfarction and micronecrosis is followed by the formation of a granulation tissue, proliferation of capillaries and fibroblasts and finally wound healing by formation of scar tissue destroying the microlymphatic network. Clinically this process leads to lipodermatosclerosis, atrophy and in its most extreme form to ulceration where the compensating mechanisms are no longer able to repair the damage.

Pulmonary oedema in healthy persons during scuba-diving and swimming

The prevalence of pulmonary oedema during scuba-diving is unknown. In our referral centre for diving accidents we have observed several episodes of pulmonary oedema in four previously healthy persons while scuba-diving or swimming. Four events were documented by physical findings, typical chest radiographic changes, and arterial hypoxaemia. Four additional episodes were identified in one of the individuals by a suggestive history. No technical problems with the diving equipment were detectable and none of the individuals reported aspiration of water. In order to gather information about the incidence of pulmonary oedema, we carried out a survey among 1,250 divers. To elucidate possible underlying mechanisms of this complication we investigated forearm vascular resistance, levels of vasoreactive hormones, and left ventricular function by Doppler echocardiography, at room temperature and during cold exposure, in four patients and in healthy control subjects. We found only one additional person with a history suggestive of pulmonary oedema among 460 responders to the survey. We found no differences in forearm vascular resistance, left ventricular systolic and diastolic function, and plasma levels of epinephrine, norepinephrine, cortisol, aldosterone, renin and atrial natriuretic peptide between the patients with a history of pulmonary oedema and the control subjects. We conclude that the occurrence of pulmonary oedema during scuba-diving or swimming is an extremely rare event in healthy individuals. The mechanisms responsible remain unclear.

Pulmonary oedema in healthy persons during scuba-diving and swimming

The prevalence of pulmonary oedema during scuba-diving is unknown. In our referral centre for diving accidents we have observed several episodes of pulmonary oedema in four previously healthy persons while scuba-diving or swimming. Four events were documented by physical findings, typical chest radiographic changes, and arterial hypoxaemia. Four additional episodes were identified in one of the individuals by a suggestive history. No technical problems with the diving equipment were detectable and none of the individuals reported aspiration of water. In order to gather information about the incidence of pulmonary oedema, we carried out a survey among 1,250 divers. To elucidate possible underlying mechanisms of this complication we investigated forearm vascular resistance, levels of vasoreactive hormones, and left ventricular function by Doppler echocardiography, at room temperature and during cold exposure, in four patients and in healthy control subjects. We found only one additional person with a history suggestive of pulmonary oedema among 460 responders to the survey. We found no differences in forearm vascular resistance, left ventricular systolic and diastolic function, and plasma levels of epinephrine, norepinephrine, cortisol, aldosterone, renin and atrial natriuretic peptide between the patients with a history of pulmonary oedema and the control subjects. We conclude that the occurrence of pulmonary oedema during scuba-diving or swimming is an extremely rare event in healthy individuals. The mechanisms responsible remain unclear.

Simultaneous assessment of muscle and skin blood fluxes with the laser-Doppler technique

The laser-Doppler technique was used to assess local muscle and skin blood fluxes at the lower limb in 20 healthy volunteers. After puncturing the anterior tibial muscle with a steel cannula, a single-fibre probe with a diameter of 0.5 mm was inserted into the muscle. Simultaneously, the skin blood flux was measured at calf and foot. The muscle blood flux at rest was 3.5 to 4 times higher than the skin blood flux at calf or foot. The spatial variability of the muscle blood flux at three different sites of measurement was considerable and tended to be higher than in the skin of the calf. After an arterial occlusion lasting 3 min, peak flux was reached in the muscle after 18.7 +/- 9.8 s, in the skin of the calf after 16.8 +/- 9.3 s, and in the skin of the foot after 22.9 +/- 14.6 s (NS). The relative flux increase during reactive hyperaemia was significantly lower in the muscle (2.7 +/- 1.3) than in the skin of the calf (3.9 +/- 1.9; p<0.05) or the foot (5.1 +/- 3.5; p<0.005). The reproducibility of reactive hyperaemia response in muscle was excellent with unchanged probe position, but exhibited a marked variability on different days. The laser-Doppler technique provides the possibility for simultaneous measurement of flow dynamics in muscle and skin with a high temporal resolution. Methodological problems include differences in probe geometry of the single-fibre compared to standard probes and differences in optical properties of the tissues. Direct comparison of flux values may, therefore, be subject to criticism, but not the comparative analysis of relative flux changes. The influence of tissue trauma on muscle blood flux has to be considered for the analysis of flux data.

Effects of subcutaneous insulin-like growth factor-I infusion on skin microcirculation

When healthy volunteers were treated with human insulin-like growth factor-I (IGF-I), mild generalized edema often developed. In the present study, the effect of IGF-I on cutaneous capillary permeability and microvascular skin blood flow was investigated using fluorescence videomicroscopy and laser Doppler fluxmetry. Transcapillary diffusion of intravenously injected sodium fluorescein (NaF) was quantitated by videodensitometry in terms of fluorescent light intensities (FLIs) 5, 10, 20, 30, 60, 120, 180 and 300 s after the first appearance of the dye. Laser Doppler fluxmetry was performed at rest (LDFrest) and during postocclusive reactive hyperemia (LDFpeak). Eight healthy subjects (3 women, 5 men; mean age 28 years, range 24-30 years) were investigated. The sensing site was the skin on the right dorsal wrist. Measurements were performed after 4 days of subcutaneous infusion of 0.9% saline (control) and of IGF-I. Mean values for the FLI were significantly higher after IGF-I than after saline infusion (p < 0.05), when the FLIs were expressed in arbitrary units. As percentages of their individual maxima, the differences were significant (p = 0.05) after 60 s (23.6 +/- 6.6% with NaCl and 31.9 +/- 7.6% with IGF-I). LDFrest and LDFpeak tended to be higher after IGF-I treatment without achieving statistical significance (p = 0.176). The mean appearance time of the dye after injection was significantly shorter (p = 0.016) in the IGF-I group than in the control group (32.0 +/- 8.4 s with IGF-I, 42.4 +/- 8.3 s with NaCl).(ABSTRACT TRUNCATED AT 250 WORDS)

Intravital capillaroscopy in patients with chronic venous insufficiency and lymphoedema: relevance to Daflon 500 mg

Microangiopathy of chronic venous insufficiency is characterized by elongated, dilated and coiled skin capillaries, which are surrounded by an enlarged pericapillary space (halo). Reduction of capillary number and even areas devoid of microvessels (atrophie blanche) are common in severe chronic venous insufficiency associated with focal microvascular ischaemia (decreased transcutaneous oxygen tension). The superficial network of skin lymphatic capillaries is obliterated in part. Oedema formation results from increased permeability of blood capillaries (enhanced transcapillary diffusion of sodium fluorescein) and deficient lymphatic drainage of interstitial fluid.

A triple electrode for simultaneous investigations of transcutaneous oxygen tension, laser-Doppler flowmetry and dynamic fluorescence video microscopy

A newly designed triple probe is introduced for measurements of transcutaneous oxygen tension, laser Doppler flowmetry (LDF) and microangiodynamics of skin capillaries by dynamic video microscopy with and without fluorochromes. The performance of the triple probe was checked in 9 healthy volunteers (6 women, 3 men; mean age: 34 years) and 9 patients (5 women, 4 men; mean age: 67 years) with peripheral arterial occlusive disease (PAOD). The mean Doppler ankle/arm pressure ratio was 0.54 +/- 0.30. Six patients suffered from severe claudication, 2 from rest pain and 1 patient had toe and forefoot necrosis. The foot dorsum was selected as measuring site. After recording baseline values of skin surface PO2 (ssPO2) at 37 degrees C, LDF and capillary images, a suprasystolic compression at the ankle level was performed for 4 min. Thirty seconds before cuff opening 0.2 ml/1 l blood volume of 20% sodium fluorescein was injected in an antecubital vein. Sodium fluorescein arrival times, filling times and maximum fluorescent light intensity times were measured, and ssPO2 and LDF were recorded continuously during postocclusive reactive hyperemia (PORH). The results indicate an adequate function of the triple probe. The mean resting ssPO2 was 2.0 +/- 1.9 mm Hg in PAOD patients and 4.0 +/- 3.9 mm Hg in controls (p = 0.185). Maximum ssPO2 during PORH was significantly reduced (p = 0.008) in patients (3.1 +/- 2.1 mm Hg) compared to healthy subjects (11.8 +/- 7.7 mm Hg). Resting LDF values were 6.5 +/- 6.4 perfusion units (PU) in PAOD patients versus 10.3 +/- 8.2 AU in controls (p = 0.295). Peak LDF during PORH was significantly reduced (p = 0.005) in patients (19.5 +/- 6.4 PU) versus healthy subjects (33.8 +/- 11.5 PU.(ABSTRACT TRUNCATED AT 250 WORDS)

Inflammatory aneurysm of the splenic artery

The case of a middle-aged man is described, who was admitted because of intermittent back pain and a high sedimentation rate. Abdominal sonography and arteriography showed a large aneurysm of the splenic artery, but failed to recognize the aneurysm as of inflammatory origin. However, the inflammatory nature of the aneurysm was evident on computer tomography scan. Intraoperatively the inflammatory origin of the aneurysm was confirmed. A saphenous vein graft was implanted and marsupialization of the aneurysm performed. Histology could clearly verify the diagnosis of an inflammatory aneurysm. This report indicates the possibility of inflammatory changes occurring in connection with a visceral artery rather than solely with the abdominal aorta.

Fluctuation of skin lymphatic capillary pressure in controls and in patients with primary lymphedema

The microlymphatic pressure was monitored by using the servo-nulling technique at the forefoot skin in 24 healthy volunteers (number of capillaries studied: 97) and in 27 patients with primary lymphedema (capillary number: 67). The lymphatic capillaries were stained by fluorescence microlymphography with fluorescein isothiocyanate-dextran 150 and cannulated using glass needles with a diameter between 7 and 9 microns. The lymphatic capillary hypertension described recently in primary lymphedema was confirmed in this series (mean pressure of controls 6.7 +/- 3.8 and, of patients 12.8 +/- 5.9 mm Hg; p < 0.001). Two patterns of pressure fluctuation were observed: rhythmic low-amplitude (mean value 3.7 mm Hg) waves with a frequency identical to respiration (respiratory movements of the thorax recorded simultaneously by a photo cell) and spontaneous nonrhythmic, low-frequency waves with a higher amplitude (mean value 5.5 mm Hg). The prevalence of waves synchronous with respiration was identical in patients and controls, whereas the low-frequency waves exhibited a significantly (p < 0.05) higher prevalence in the patients (41.7%) than in the controls (70.4%). The hypothesis is advanced that in primary lymphedema a considerable amount of lymphatic fluid is removed by lymphatic pathways with small calibre and high resistance, resulting in microvascular hypertension, and that contractions of the few preserved large proximal lymphatic collectors are enhanced. The latter mechanism could explain the increased prevalence of spontaneous microlymphatic pressure fluctuations with high amplitude and low frequency.

Lymphatic capillary pressure in patients with primary lymphedema

Flow and pressure dynamics in minute human lymphatics are unexplored. Lymphatic capillary pressure was measured by the servo-nulling technique at the foot dorsum of 14 patients with primary lymphedema and 15 healthy controls. Glass micropipettes (7-9 microns) were inserted under microscopic control into lymphatic microvessels previously stained by fluorescence microlymphography (FITC-Dextran 150,000). Mean lymphatic capillary pressure was 7.9 +/- 3.4 mm Hg in the controls and 15.0 +/- 5.1 mm Hg in the patients. The difference was significant at the P < 0.001 level. In about half of the patients and control subjects studied pressure fluctuated by more than 3 mm Hg. The mean intralymphatic pressure of lymphedema patients was slightly below mean interstitial pressure measured by J. T. Christensen, N. J. Shaw, M. M. Hamas and H. K. Al Hassan (1985, Microcirc., Endothelium, Lymphatics 2, 267-384) (17.9 mm Hg) in lower leg lymphedema. Microlymphatic hypertension present in patients with primary lymphedema is probably an important factor for edema formation.

[Three-dimensional imaging of the pelvic veins using magnetic resonance angiography]

The veins in the pelvis and lower limbs have been demonstrated by means of magnetic resonance angiography (MRA) in 11 normals and in 20 patients, using a "time-of-flight" technique (TOF). Using normals, changes in the measurement parameters were used in order to optimise the examination protocol; consequently, the internal and external iliac veins and the superior and inferior gluteal veins could be identified in all cases and the internal pudendal veins in 6 out of 11 cases. This examination protocol was then used in patients with clinical suspicion of lower limb or pelvic vein thrombosis. Comparison of the MRA findings with those of phlebography (7 cases), duplex sonography (6 cases) and colour Doppler examinations (11 cases) showed that MRA was better for diagnosing thrombosis of the internal iliac veins (10 cases) than the other methods. In two patients thromboses of the common iliac veins and the inferior vena cava were demonstrated which were missed by colour Doppler examination. On the basis of our present experiences, MRA, using a two-dimensional TOF technique, appears to be a reliable non-invasive technique for demonstrating the veins of the pelvis and thigh.

Variability of different patterns of skin oscillatory flux in healthy controls and patients with peripheral arterial occlusive disease

Variability of patterns of laser Doppler flux motion was analysed at 5 different sites at the foot of 12 healthy controls and 24 patients with different degrees of ischemia due to peripheral arterial occlusive disease. Patterns were evaluated by means of the frequency histogram method. Three main flux motion components were detected at mean frequencies of 3.5 +/- 1.1 min-1 (low frequency waves, LF), 17.2 +/- 2.7 min-1 (high frequency waves, HF) and at 62.6 +/- 8.5 min-1 (pulsatile waves, PF). The characteristic pattern in normals consisted of LF and PF waves. In severe ischemia oscillatory flux was predominantly characterized by the combination of LF and HF waves and loss of pulsatile flux, or by the absence of any flux motion. Claudicants covered the entire spectrum of the flux motion patterns. In controls spatial variations were mainly due to the occasional presence of HF waves at one of the 5 sites. With increasing ischemia spatial variability of HF waves decreased due to more homogeneous presence. Loss of pulsatile flux was inhomogeneous in claudicants but almost complete in severe ischemia. Whereas LF waves were almost always observed at all sites of controls and claudicants there was considerable spatial variability in severe ischemia due to inhomogeneous loss of LF waves. Prevalence of the distinct flux motion patterns was well reproducible in controls and patients. Patterns showed a marked day to day variability when sites of measurement were compared.

[Round shadows in the thoracic roentgen picture, nicotine abuse]

A 69 year old male patient was seen at our outpatient clinic because of a paravertebral mass in the routine x-ray-film of the chest. The patient was in good health, showed no loss of weight and complained only of slight cough probably due to his smoking habits. In view of these findings a benign lung tumor was suspected. However, the computed tomography of the chest revealed an aneurysm of the descending aorta which was successfully operated.

Microangiopathy of cutaneous blood and lymphatic capillaries in chronic venous insufficiency (CVI)

The severity of microangiopathy in patients with chronic venous insufficiency (CVI) determines the extent of the trophic disturbances of the skin. Resulting from valvular incompetence of deep and/or perforating veins and the accompanying venous outflow obstruction caused by deep venous thrombosis (DVT), the increased ambulatory venous pressure heads are transmitted retrograde into the microvasculature of the skin at the ankle region. In the present study, we have assessed the changes in the cutaneous microvasculature by dynamic fluorescence video microscopy, fluorescence microlymphography, and transcutaneous oxygen tension (tcPO2) measurements. In mild forms of CVI, capillary density, morphologic characteristics, and tcPO2 are still normal. Fluorescent light intensity is, however, significantly increased, indicating an increased transcapillary diffusion of sodium fluorescein (NaF) as a marker for enhanced leakage of the capillaries in the early stage of the disease. The pericapillary halo diameters are significantly enlarged, compared to controls (p < 0.01). In the severe stages of CVI and in patients with venous ulcers, capillary thromboses, probably caused by endothelium-blood cell interactions, may lead to a reduced capillary density. In order to enlarge the exchange surface area, the remaining skin capillaries become tortuous (capillary tufts). Parallel to the reduced capillary number, tcPO2 decreases and can be extremely low at the ulcer rim or at white atrophy spots. Fibrin cuffs are not a specific finding for venous ulceration and do not significantly impair oxygen diffusion. Fluorescence microlymphography permits visualization of the lymphatic capillaries of the superficial skin. In severe stages of CVI, the lymphatic capillary network at the medial ankle area is destroyed, and the remaining lymphatic capillary fragments have an increased permeability to FITC-dextran with a molecular weight of 150,000. These findings demonstrate a special lymphatic microangiopathy in CVI, suggesting an additional lymphatic component in the edema formation.