Regulation of myocardial blood flow response to mental stress in healthy individuals

Mental stress testing has been proposed as a noninvasive tool to evaluate e ndothelium-dependent coronary vasomotion. In patients with coronary artery disease, mental stress can induce myocardial ischemia. However, even the de terminants of the physiological myocardial blood flow (MBF) response to men tal stress are poorly understood. Twenty-four individuals (12 males/12 fema les, mean age 49 +/- 13 yr, range 31-74 yr) with a low likelihood for coron ary artery disease were studied. Serum catecholamines, cardiac work, and MB F (measured quantitatively with N-13 ammonia and positron emission tomograp hy) were assessed. During mental stress (arithmetic calculation) MBF increa sed significantly from 0.70 +/- 0.14 to 0.92 +/- 0.21 ml.min(-1).g(-1) (P < 0.01). Mental stress caused significant increases (P < 0.01) in serum epin ephrine (26 +/- 16 vs. 42 +/- 17 pg/ml), norepinephrine (272 +/- 139 vs. 32 2 +/- 136 pg/ml), and cardiac work [rate-pressure product (RPP) 8,011 +/- 1 ,884 vs. 10,416 +/- 2,711]. Stress-induced changes in cardiac work were cor related with changes in MBF (r = 0.72; P < 0.01). Multiple-regression analy sis revealed stress-induced changes in the RPP as the only significant (P = 0.0001) predictor for the magnitude of mental stress-induced increases in MBF in healthy individuals. Data from this group of healthy individuals sho uld prove useful to investigate coronary vasomotion in individuals at risk for or with documented coronary artery disease.