Capillary blood flow: Videodensitometry in the atherosclerotic patient

Abstract

Recently the noninvasive technique of videomicroscopy has demonstrated qualitative morphologic changes in the nutritional skin capillaries in atherosclerotic (ATS) patients. The purpose of this study is to quantitatively examine the ATS microcirculation and effects induced by reconstructive surgery. Capillary blood flow velocity (CBV) of single vessels within the nail fold of the large toe was measured by dual-sensor videodensitometry in 14 ATS patients (age 45 to 80 years) and 11 age-matched controls. In addition to CBV, capillary diameter (CD) and the number of flow-active capillaries (FC) were also measured at constant temperature. Of the 14 patients, eight had measurements repeated 1 week after reconstructive surgery. The measurements were obtained at rest and then periodically after a 45-second period of pedal inflow occlusion. Respective group averages at rest for CBV, CD, and FC for the 14 ATS patients were as follows: 0.16 mm/sec, 10.5 μm, and 6.8 capillaries per field. Corresponding values for the control subjects were 0.10 mm/sec, 8.7 μm, and 5.3 capillaries per field. Combining CBV, CD, and FC into a measurement of volume capillary flow yielded a value of 281 pl/sec/mm2 for the patients and only 85 pl/sec/mm2 for the controls (p < 0.02). Peak postocclusion CBV significantly increased, whereas FC significantly decreased relative to rest in the control group; however, the only patient group that responded to occlusion-induced ischemia was the postoperative group. In these patients there was a decrease in CBV and an increase in FC relative to rest. These responses are exactly opposite to those in the agematched controls. Furthermore, the operative group showed no significant differences between pre- and postoperative values. These data indicate that (1) ATS lesions elicit a chronic hyperemic response in the distal capillary network, (2) the ATS hyperemic microcirculation is unresponsive to acute ischemia, (3) operation increases arterial inflow but does not increase capillary volumetric flow 1 week after reconstruction, and (4) capillary blood flow autoregulatory mechanisms, present in the age-matched controls, were absent in the ATS group and were not restored 1 week after reconstruction. These findings may be implicated as pathophysiologic causes of dependent rubor and postreconstructive pedal edema.