Microangiopathy in severe chronic venous insufficiency evaluated by fluorescence video-microscopy

Fluorescence video microscopy after intravenous injection of Na-fluorescein was used to study capillary morphology, pericapillary halo diameters, microvascular flow distribution and transcapillary diffusion of the dye in 15 healthy controls and 15 patients with severe chronic venous insufficiency (CVI). The recordings were made in the medial ankle region. Transcapillary diffusion was monitored within a densitometer window encompassing 3.2 mm2 of skin surface. Microangiopathy known from previous studies was documented in the patients with severe CVI. The number of skin capillaries within the field of observation was not reduced. In some cases inhomogeneous microvascular flow distribution and probable microthrombosis were detected. Mean halo size averaged 81 — 15 µm in the controls and 146 ± 47 µm in the patients (P < 0.001). Unexpectedly, transcapillary diffusion of Na-fluorescein was not significantly increased in the field of measurement. Possible explanations include asynchronous inflow of the dye, the presence of thrombosed and therefore not perfused capillaries, a pericapillary fibrin layer limiting diffusion and redistribution of flow in favour of the subcutaneous tissue.