BAROREFLEX SENSITIVITY IN THE ELDERLY WITH SILENT-MYOCARDIAL-ISCHEMIA

In order to assess high-pressure barocepture sensitivity and parasympa thetic function in elderly patients with silent myocardial ischemia, w e selected 45 inpatients in our geriatric unit for a prospective cohor t study of patients with coronary heart disease. All patients were ove r 65 years of age (37 men and 8 women) and had coronary heart disease, documented by an angiographic study and electrocardiographic evidence of myocardial ischemia during exercise stress testing, performed acco rding to the Bruce protocol. The subjects were divided in three subgro ups: group 1 (22 patients) with electrocardiographic and echocardiogra phic history of myocardial infarction but no angina chest pain during exercise testing; group 2 (13 patients) with no exercise induced chest pain; and group 3 (10 patients) with exercise-induced chest pain. Bar oceptor sensitivity was assessed in all subjects, by evaluating heart rate changes expressed in RR interval on the basis of changes in the m ean arterial pressure during intra venous infusion of stepwise doses ( 50-100 and 150 mu g) of phenylephrine hydrochloride. Heart rate change s were also evaluated during overshoot of the Valsalva maneuver (Valsa lva max.), providing an index of parasympathetic activity. Our results showed that group two patients (only silent ischemia) had significant ly (P> 0.001) greater baroceptor sensitivity than the other two groups (group 2; 15.2 +/- 1.9 ms/mmHg; group 1: 10.0 +/- 1.7 ms/mmHg; and gr oup 3: 9.8 +/- 1.7 ms/mmHg). Group two also showed a significant posit ive correlation (r = 0.58: P < 0,05) between baroceptor sensitivity an d end-diastolic pressure and a significant inverse correlation (r= -0. 672; P<0.05) between baroceptor sensitivity and the ejection fraction. Group 2 patients had a significantly longer RR interval than group 1 (P < 0.05) and group 3 (P < 0.05): a significant positive correlation (r = 0.620; P < 0.05) between Valsalva max. and end-diastolic pressure ; and a significant inverse correlation (I = 0.694; P < 0.05) between Valsalva max. and the ejection fraction. Valsalva max. and baroceptor sensitivity correlated significantly in all three groups (group 1, r = 0.707; P < 0.001; group 2, r = 0.94; P < 0.001; and group 3; r = 0.83 3; P < 0.05). In conclusion our data suggest that elderly patients wit h silent ischemia appear to have an increased capacity for evoking par asympathetic reflexes that could inhibit pain perception. (C) 1997 Els evier Science Ireland Ltd.