Amorim Ds

Effect of parasympathetic impairment on the haemodynamic response to handgrip in Chagas's heart disease.

Haemodynamic responses to sustained isometric exercise (handgrip at 30% of maximum voluntary capacity) were studied in 10 patients with Chagass cardiopathy without previous or current heart failure. Five of the patients (group 1) had profound impairment of parasympathetic control of heart rate. They had no tachycardia in response to intravenous administration of atropine and no bradycardia during phase IV of the Valsalva manoeuvre. The other five (group 2) showed normal vagal regulation of heart rate, as judged by chronotropic responses to these tests. The heart rate change (mean (SD] elicited by the handgrip test was significantly lower in group 1 (from 93.0 (14.1) to 95.0 (16.7) beats/min) than in group 2 (from 78.2 (15.8) to 92.8 (18.1) beats/min). Pressor responses to handgrip were of similar magnitude (from 91.6 (7.8) to 109.0 (8.0) mm Hg in group 1 and from 88.6 (11.9) to 106.8 (20.9) mm Hg in group 2). In both groups no significant change in stroke index was detected during handgrip. Cardiac index increased during handgrip from 4.0 (1.2) to 4.8 (1.3) 1/min/m2 in group 2, but there was no significant change in group 1 (from 4.9 (0.7) to 4.8 (1.1) 1/min/m2). Changes in calculated systemic vascular resistance were significantly higher in group 1 (from 934 (175) to 1176 (383) dyn s cm-5) than in group 2 (from 1109 (404) to 1112 (424). This study shows that parasympathetic impairment adversely influences the haemodynamic pattern of response to isometric exercise in patients with Chagass heart disease. In such conditions, the pressor response to handgrip is predominantly mediated by an increase in systemic vascular resistance rather than an increase in cardiac output.

Intraoperative Measurement of the Orifice Area in Patients with Mitral Valve Stenosis

This study was carried out in ten patients in order to compare results of mitral valve area evaluated by a new intraoperative technique and those provided by conventional hemodynamic methods. The results obtained correlated very well (r = 0.95) with values calculated by the Gorlin formula. Paired data checking were closer than 0.3 cm2 in all but one of patients with moderately severe mitral stenosis. It is concluded that the method for intraoperative measurement of the mitral valve area is simple, safe and reliable.