Pathophysiology and Natural History Raynaud's Syndrome

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 pressures 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 (300 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 pressure 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. Circulation 77, No. 5, 988-996, 1988. ELUCIDATION of the mechanisms responsible for the vasospasm accompanying Raynaud's syndrome and the management of patients have been hampered by the lack of a reliable, quantitative laboratory method for the study of the vasospastic phenomena, for the follow-up of the patients, and for the evaluation of therapeutic procedures. Typical color changes associated with digital vasospasm allow a definite diagnosis. Vasospastic phenomena, however, are elusive and cannot be reproduced consistently at home, in the clinic, or in the laboratory.' Measurements of changes in blood flow in response to a cold challenge or measurements of some index of blood flow, e.g., skin temperature, have been used extensively. They have not proven to be reliable, however, probably because various factors From the Departments of Physiology and Medicine, University of Manitoba, and St. Boniface General Hospital, Winnipeg, Manitoba, Canada. Supported by a grant-in-aid from the Manitoba Heart Foundation. Address for correspondence: Stefan A. Carter, M.D., Vascular Laboratory, St. Boniface General Hospital, 409 Tache Ave., Winnipeg, Manitoba, Canada, R2H 2A6. Received Feb. 20, 1987; revision accepted Jan, 14, 1988. 988 that influence the occurrence ofvasospasm are difficult to control." 2 Also, since Raynaud's attacks are thought to be associated with critical closure of the main digital arteries,3-5 measurements of blood flow, which depend mainly on the degree of vasoconstriction in the peripheral vessels of the microcirculation, may not provide information relevant to the larger digital vessels implicated in Raynaud's syndrome. Noninvasive measurements of local systolic pressure represent an established and valuable method for assessment of obstruction in the arteries supplying the extremities and digital pressures have been used for that purpose in the upper and lower limbs.6-9 It is known that in normal subjects and patients with a certain degree of obstruction, digital pressures are affected by the vasomotor tone.9' 10Vasodilatation, such as may be induced by body heating, increases blood flow and results in lower systolic pressure because pressure energy is lost to a greater extent with high flow through the vessels proximal to the digits. Conversely, with vasoconstriction and low blood flow the distal pressures increase. However, Krahenbiihl et al.4 and NielCIRCULATION by gest on A ril 9, 2017 http://ciajournals.org/ D ow nladed from PATHOPHYSIOLOGY AND NATURAL HISTORY-RAYNAUD'S SYNDROME sen and Lassen11 have reported that in certain individuals, especially those with Raynaud's syndrome, finger pressures recorded during local cooling of the digits fell precipitously. There was often loss of measurable pressure, indicating the occurrence of critical closure in the main arteries of the fingers. Since this technique provides information concerning the response of the digital arteries to cold, it represents a potentiallyvaluable method for the study ofvasospastic phenomena and for the evaluation of treatments. Although several reports using the above approach have appeared, there are considerable differences in the methods and reported results.12-14 Also, although vasospastic Raynaud's attacks are known to be precipitated by cooling, the relative importance of the effect of local temperature and of sympathetic vasoconstriction induced by cold on the digital blood vessels has not been elucidated.1' 3' 5 The present study demonstrates the importance of sympathetic vasoconstriction in producing the spasm of the digital arteries and of its interaction with the local temperature. The effect of cold on the opening of digital arteries and of arterial obstruction on the measurements in patients with Raynaud's syndrome were examined. Also, it was demonstrated that when a controlled state of vasoconstriction was maintained during the measurements, the method provided a useful tool for the diagnosis of Raynaud's phenomena of various causes.