Myocardial and peripheral vascular responses to behavioral challenges and their stability in black and white Americans.

The purpose of this study was to assess the short term stability of myocardial and peripheral vascular responses to behavioral challenges, and to compare the response patterns of Black and White men. Blood pressure and heart rate, as well as stroke volume, cardiac output, total peripheral resistance, and systolic time interval measures derived from the impedance cardiogram were obtained in 12 Black and 12 White men. These measures were taken prior to and during an evaluative speech stressor, a mirror star tracing task, and a forehead cold pressor test presented during two laboratory sessions scheduled two weeks apart. In general, total peripheral resistance and impedance-derived baseline measures showed acceptable reproducibility (G greater than .85). With a few exceptions, adequate reliability was also demonstrated for change (delta) scores. All tasks raised blood pressure responses above resting levels. Blacks demonstrated significantly greater increases in total peripheral resistance responses across tasks. Whites but not Blacks also revealed increases above baseline in cardiac output and contractility as estimated by the Heather Index. These findings are consistent with the view that Blacks show greater vascular responsiveness than Whites across a variety of tasks, but reveal less myocardial responsiveness.