ISCHEMIC, HEMODYNAMIC, AND NEUROHORMONAL RESPONSES TO MENTAL AND EXERCISE STRESS - EXPERIENCE FROM THE PSYCHOPHYSIOLOGICAL INVESTIGATIONS OF MYOCARDIAL-ISCHEMIA STUDY (PIMI)

Background The pathophysiology of mental stress-induced myocardial isc hemia, which occurs at lower heart rates than during physical stress, is not well understood. Methods and Results The Psychophysiological In vestigations of Myocardial Ischemia Study (PIMI) evaluated the physiol ogical and neuroendocrine functioning in unmedicated patients with sta ble coronary artery disease and exercise-induced ischemia. Hemodynamic and neurohormonal responses to bicycle exercise, public speaking, and the Stroop test were measured by radionuclide ventriculography, ECG, and blood pressure and catecholamine monitoring. With mental stress, t here were increases in heart rate, systolic blood pressure, cardiac ou tput, and systemic vascular resistance that were correlated with incre ases in plasma epinephrine. During exercise, systemic vascular resista nce fell, and there was no relationship between the hemodynamic change s and epinephrine levels. The fall in ejection fraction was greater wi th mental stress than exercise. During mental stress, the changes in e jection fraction were inversely correlated with the changes in systemi c vascular resistance. Evidence for myocardial ischemia was present in 92% of patients during bicycle exercise and in 58% of patients during mental stress. Greater increases in plasma epinephrine and norepineph rine occurred with ischemia during exercise, and greater increases in systemic vascular resistance occurred with ischemia during mental stre ss. Conclusions Mental stress-induced myocardial ischemia is associate d with a significant increase in systemic vascular resistance and a re latively minor increase in heart rate and rate-pressure product compar ed with ischemia induced by exercise. These hemodynamic responses to m ental stress can be mediated by the adrenal secretion of epinephrine. The pathophysiological mechanisms involved are important in the unders tanding of the etiology of myocardial ischemia and perhaps in the sele ction of appropriate anti-ischemic therapy.