Abnormal microvascular response is localized to the digits in patients with systemic sclerosis

To investigate the hypothesis that cutaneous microvascular perfusion of the dorsum of the hand (in response to local heating) and distal phalanx (in response to occlusion) is impaired in patients with systemic sclerosis (SSc) compared with healthy controls.

Twenty-nine patients with SSc and 29 control subjects were recruited. Perfusion was monitored using novel dual-wavelength laser Doppler imaging, allowing measurement of both smaller (capillaries) and larger (thermoregulatory) vessels. Postacclimatization, a baseline dorsum scan (red or green wavelength) was performed. A heating pad was placed on the dorsum (total stimulus time 6 minutes at 34-40 degrees C), and following removal of the pad, baseline wavelength scans were performed until perfusion returned to baseline values. This was then repeated for the second wavelength. The maximum perfusion increase due to heating (PEAK1) and area under the perfusion-time curve (AUC) were determined. In addition, scans (both wavelengths) of the index finger were performed prior to and during 2 minutes of suprasystolic occlusion, and the response upon occlusion release was monitored with single-point laser Doppler. The decrease in perfusion due to occlusion (from preocclusion baseline values) (%DECREASE) and the maximum increase (from baseline perfusion values under occlusion) in hyperemic perfusion upon removal of occlusion (PEAK/OCC) were calculated.

PEAK1 and AUC values were not significantly different between patients and controls, as assessed with either wavelength. A significant difference between groups was found in the %DECREASE values with the green, but not the red, wavelength. A significant between-group difference was also found in PEAK/OCC values, using both wavelengths.

This study suggests that SSc has no effect on microvascular perfusion in the dorsum of the hand, and that the abnormal microvascular response is localized to the digits, affecting both smaller and larger vessels.