Measurement of different human microvascular dimensions by combination of videomicroscopy with Na-fluorescein (NaF) and indocyanine green (ICG) in normals and patients with systemic sclerosis.

Using a double tracer technique with the two dyes indocyanine green (ICG) and Na-fluorescein (NaF) it becomes possible to measure diameters of the capillary, red blood cell column plasma layer and pericapillary halo. 12 healthy controls and 12 patients with systemic sclerosis were studied. The first three mentioned diameters were significantly enlarged in the patient group on the arteriolar, venular and apical side of the nailfold capillaries (p less than 0.03-0.001). Halo diameter was only significantly increased at the apex and not at the two capillary limbs. This finding confirms the visual impression of "dwarf hat formation" or "apical capping" after NaF injection as an important sign for microangiopathy due to collagen vascular disease. It corresponds to preferential halo enlargement at the loop apex. Since ICG couples almost completely to plasma proteins it permits delineation of the inner capillary contours and visualization of capillary aneurysms even when they are completely filled by plasma.