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SUMMARY

provide views at 900 angles to one another. No hemiaxial views were taken. A stratified random sampling scheme was used to ensure selection of a representative spectrum of coronary disease groups, as categorized by the number of major vessels with at least 70% stenosis and by normal or abnormal left ventricular function. Only films estimated to be of adequate technical quality were eligible for this study. Eleven physicians, representing the Seattle Heart Watch cooperating facilities, individually reviewed these ten films in a pre-assigned random order and completed the standard Heart Watch arteriography forms. Three of the eleven subsequently met to resolve differences of opinion and provide a joint reading which could serve as a standard from an "expert panel."Raw observations collected were: the estimated amount of stenosis (percent narrowing in the diameters) of each of ten vessel segments, the presence or absence of collaterals, the degree of left ventricular contraction according to a qualitative five-division grading, as well as a film quality rating, and an overall assessment of the presence of coronary artery disease.The statistical approach taken for all entirely numerical variables was to use the standard deviation of the responses as a measure of the amount of variability and thus of the amount of agreement. When considering the amount of agreement on variables that were at least partially nominal in nature, standard deviations were not always applicable. For example, each reader was asked to estimate the amount of narrowing (to the nearest 10%) in the diameters of each of ten vessel segments from each patient. However, when the vessel segment was not sufficiently visible to allow an assess-324 CIRCULATION by guest on

In 11 normal men, central circulatory responses were measured while skin temperature was changed in a square-wave pattern during uninterrupted exercise (26% to 64% maximal oxygen consumption). Skin temperature was changed at 30-minute intervals, beginning at 32°C. On raising it to 38.2°C at low oxygen consumption (Vo 2 ), cardiac output increased 2.5 liters/min, and central blood volume, aortic mean pressure, and stroke volume fell (7%, 7%, and 11%, respectively). Right atrial mean pressure fell 2.2 and 2.3 mm Hg during control and heating periods, respectively. All variables returned to control levels when skin temperature was reduced toward 26.9°C. Raising it to 40°C reproduced these changes with a more clear-cut drop in right atrial mean pressure. Results indicated reduced peripheral venous tone and cutaneous pooling of blood during heating and rapid reversal on cooling. On raising skin temperature to 38.7°C at high Vo 2 , cardiac output increased 19% (3.1 liters/min), stroke volume decreased 14%, and central blood volume rose slightly. Aortic mean pressure fell during the control period and was maintained or rose during heating periods. On cooling, central blood volume and stroke volume rose, cardiac output remained elevated, and aortic mean pressure fell. Increases in cardiac output during heating were related to skin temperature and not to Vo 2 or body temperature. At high Vo 2 , circulatory adjustments favor metabolic rather than thermoregulatory demands. This work was supported in part by U. S. Public Health Service Grant HE-09773 from the National Heart Institute. A part of this study was conducted through the Clinical Research facility of the University of Washington, supported by the National Institutes of Health (Grant FR-37). ADDITIONALDr. Rowell was an Established Investigator of the American Heart Association and was supported by the Washington State Heart Association.A preliminary report of this work was presented at the annual meeting of the American Heart Association, November 23, 1968, Miami, Florida. Received August 19, 1968. Accepted for publication March 25, 1969. thermal and metabolic stresses have depended upon manipulation of environmental temperature rather than skin temperature. But, where natural conditions are simulated, skin temperature may vary throughout the exposure (1). It will also vary over the body surface and may well be reduced, the more severe the exercise, due to an increased sweating response (1). In short, skin temperature is not tightly controlled by exposing subjects to controlled environments, but it is important in both direct local control and reflex control of the vasoactive state of the skin (2). Accordingly, it is important to control this variable when attempting to understand the mechanisms governing human cardiovascular responses to metabolic and thermal stresses. Our experimental design was based on controlling skin temperature as closely as possible and manipulating it in a square-wave pattern between extremes during uninterrupted exercise. It ...

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