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SUMMARY Haemodynamic responses to. sustained isometric exercise (handgrip at 30% of maximum voluntary capacity) were studied in 10 patients with Chagas's 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)

Thus, regions with moderately reduced 18F-fluorodeoxyglucose uptake with normal flow occur commonly in patients with ischemic left ventricular dysfunction. The majority of these regions show impaired systolic function at rest and exercise-induced thallium abnormalities that are only partially reversible. These observations suggest that such regions represent an admixture of fibrotic and reversibly ischemic myocardium.

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