Apparent finger systolic pressures during cooling in patients with Raynaud's syndrome.

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Abstract
Despite considerable research, the mechanisms responsible for the vasospasm associated with Raynaud''s syndrome are not well understood and there is no reliable diagnostic test. In the present studies, measurements of systolic pressure in locally cooled fingers were used to address these issues. We found that local cooling produced a marked decrease or loss of the apparent finger systolic pressure in patients with Raynaud''s syndrome in whom a standardized vasoconstriction had been induced by body cooling. Abnormal responses were encountered in 109 of 125 patients with secondary Raynaud''s syndrome, in 21 of 37 patients with primary Raynaud''s disease or the syndrome of uncertain cause, and in two of 63 subjects without symptoms of Raynaud''s. These data suggest a high accuracy of the test in patients with secondary Raynaud''s syndrome and lower accuracy in those with disease of primary or uncertain cause. We studied responses of systolic pressure to alterations in body and local temperatures in fingers with and without low pressures secondary to proximal arterial obstruction. Our data show that although local cooling has a small independent effect that increases vascular tone: (1) sympathetic vasoconstriction induced by body cooling is necessary to produce vasospasm and often produces it without local cooling, (2) high local temperature (30.degree.C) protects from vasospasm, and (3) low finger blood pressure predisposes to it. Delayed opening of the vessels observed after sudden deflation of blood pressure cuffs suggests that abnormal responses of finger systolic pressures to cold represent combined effects of high vascular tone, delayed opening, and local blood pressure. We conclude that measurements of local systolic pressures in response to cold provide a valuable method for the study of the mechanisms of Raynaud''s syndrome, a useful diagnostic test, and may have an application to the evaluation of therapeutic interventions.