Coronary dynamics and mental arithmetic stress in humans. Incidence and mechanisms of psychological stress-induced myocardial ischemia were investigated in a population of 63 patients using mental arithmetic. Fifty subjects (group 1) were selected as a consecutive population of ischemic patients with electrocardiographic documentation of ischemia at rest, on effort, or both. Mental arithmetic induced increases in heart rate, blood pressure, and rate-pressure product in all patients. Transient ischemic electrocardiographic changes occurred in 22 patients (44%; positive mental arithmetic), the majority of whom had both resting and exercise angina. In negative mental arithmetic tests, peak rate-pressure product was always lower than that achieved during exercise (mean +/- SD, 11.9 +/- 3 versus 21.3 +/- 5, p less than 0.01). Of the 22 patients with positive mental arithmetic tests, ischemia occurred in only six, at a rate-pressure product equal to or more than the one achieved during exercise (21.1 +/- 5 versus 19.4 +/- 4, p less than 0.01), suggesting an increase in myocardial O2 demand exceeding the limited increase in flow; in the remaining 16 patients, rate-pressure product values were significantly lower (14.8 +/- 3 versus 22.7 +/- 6, p less than 0.01), suggesting a primary reduction in coronary blood flow that is probably related to an increase in coronary tone. To assess the possible site of such a vasoconstriction, the effect of mental arithmetic on large coronary artery diameter was tested in 13 additional unselected patients (group 2) undergoing coronary angiography for a chest pain syndrome. 