995-19 The Impact of Mental Stress and α-Adrenergic Activation on the Microcirculation of Patients with Coronary Artery Disease

Mental stress results in sympathetic activation and provokes constriction of diseased epicardial coronary artery segments, which may decrease coronary blood flow. We investigated the effect of mental stress (10 min. video game) on the coronary microcirculation by measuring cardiac norepinephrine spillover (NESP) and left anterior descending (LAD) coronary artery blood flow (intracoronary Doppler flow velocity and quantitative angiography) in non-significantly diseased (<40% stenosis) LAD arteries of 7 patients with significant coronary artery disease (CAD; >50% stenosis) of other vessels. These responses were compared to those in 5 patients with normal coronary angiograms (NCA). Coronary vascular resistance (CVR) was calculated by dividing mean blood pressure (MBP) by coronary blood flow. Measurements during mental stress were compared to pre-mental stress measurements. Data=mean±S.D. during mental stress.%Change in:MBPNESPLAD diameterCVRNCA+13±8+123±130+4±10–26±9CAD+19±10+90±64+1±6–4±18**p<0.05 vs NCAMental stress resulted in significant coronary microvascular dilation in patients with NCA (p<0.05 vs pre-mental stress) in contrast to no vasodilation in patients with CAD (p=NS). 5 CAD patients underwent repeat mental stress (MS), following intracoronary phentolamine (P) 0.02mg/kg.%Change in:MSPNESPLAD diameterCVRControl MS+26±13+87±40+1±6–9±14P+MS+18±9+254±117**+3±7**–28±19****p<0.01 vs Control MSEven though phentolamine increased NESP substantially due to presynaptic α2;-adrenergic blockade, microvascular dilation was greater during repeat mental stress in CAD patients than during their initial mental stress, and similar in magnitude to the response of NCA patients. Thus, coronary atherosclerosis is associated with absence of a microvascular vasodilator response to mental stress, due to α-adrenergic constrictor effects on the coronary microcirculation