To determine circulating endothelin-1 levels (ET-1) in patients with primary or secondary associated Raynaud's phenomenon (RP) under resting conditions and in response to cold provocation.
Patients were categorised as primary RP (18) or scleroderma associated RP (14). Finger blood flow was measured by venous occlusion plethysmography at finger temperatures of 32 degrees C and 24 degrees C. Vasospasm was detected as a finger systolic pressure of 0 mm Hg after standardised provocative cooling. Severity of vasospasm was assessed by the level of cooling required to provoke spasm. Plasma ET-1 levels were measured in antecubital blood withdrawn under baseline conditions (finger 32 degrees C) and at the point of vasospasm. Measurements were also made in 19 matched control subjects.
Finger blood flow was lower in patients with RP than in controls, with no difference between the two RP groups. Vasospasm occurred in all patients with RP but not in any control subjects and a grading system of severity was established. Baseline plasma ET-1 levels were similar in patients with RP and controls. Increases in ET-1 levels at the point of vasospasm in patients or corresponding timepoint in controls were also similar. There was no significant difference between the ET-1 levels in the two RP subgroups when the fingers were warm or when vasospasm was present.
These results do not support the hypothesis that ET-1 plays a part in the pathogenesis of RP. Objective testing is a useful adjunct to the clinical diagnosis of RP and allows assignment of a severity grade.