EFFECTS OF HOSTILITY ON PLATELET REACTIVITY TO PSYCHOLOGICAL STRESS IN CORONARY HEART-DISEASE PATIENTS AND IN HEALTHY CONTROLS

Previous studies have demonstrated a potential relationship between ps ychological stress and platelet activation, which may serve as a link between stress and myocardial infarction (MI). However, the possibilit y that personality traits associated with coronary heart disease may a ffect platelet activation has not been adequately investigated. The ef fect of a laboratory stressor (Type A Structured Interview (SI) and sp eech task) on platelet activation was assessed in 14 stable post-MI pa tients and 15 age-matched healthy men, using a standardized method of measuring plasma beta-thromboglobulin (BTG) levels. BTG levels were in creased after the stressor (average change = 2.0 ng/ml, p = .005). Inc reases in BTG with stress were related to higher SI ratings of Potenti al for Hostility (r = .53, p = .004) and Type A behavior (r = .43, p = .02) but not to Cook-Medley-rated hostility scores. Increases in nore pinephrine levels and in diastolic blood pressure were nonsignificantl y related to increases in BTG levels (ps < .10), whereas increases in epinephrine levels were unrelated. Despite ceasing aspirin and other p latelet inhibitors for 10 days before testing, individuals taking plat elet inhibitors before the study had less change in BTG with stress (p = .05). However, after statistical adjustment for this factor, SI rat ings of Potential for Hostility were still strongly related to increas es in BTG with stress (adjusted r = .56, p = .002). Contrary to expect ations, healthy men tended to have greater change in BTG with stress t han post-MI patients (p = .06). These results indicate that acute stre ss increases BTG levels and that hostility is related to greater plate let reactivity, independent of any long term effects of platelet inhib ition.