Non-invasive evaluation of autonomic tone changes during isometric exercise in normal subjects and in patients with coronary artery disease.
In order to evaluate the clinical implications of QT/QS2 ratio during manoeuvres of sympathetic stimulation we studied the effects of handgrip (75% of maximal voluntary contraction) in 18 middle-aged normal subjects and in 16 patients with previous myocardial infarction. We also evaluated the effects of propranolol (0.1 mg/kg i.v.) in all normal subjects and in 10 of the 16 patients with coronary artery disease. At rest the two groups had similar heart rate, blood pressure, QT, QS2 and QT/QS2 ratio values. A significant increase in heart rate and systolic blood pressure was recorded during handgrip both in normal subjects and in patients with coronary artery disease; QT/QS2 significantly increased in normal subjects but did not show significant variations in patients with coronary artery disease, with significant differences between the two groups at peak exercise. Handgrip-induced QT/QS2 changes showed a marked variability both in normal and diseased subjects. After propranolol, QT/QS2 showed no significant difference at peak exercise in the two groups. The variability of ratio changes was nullified by the administration of the drug. These findings suggest that handgrip-induced QT/QS2 changes might be an expression of beta-adrenergic discharge. The clinical value of handgrip-induced QT/QS2 changes in detecting patients with coronary artery disease is limited by the variability of the response of the ratio observed in the two groups.
D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001794:Blood Pressure / Q000187:drug effects; D003327:Coronary Disease / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D009129:Muscle Tonus; D009203:Myocardial Infarction / Q000503:physiopathology; D011433:Propranolol / Q000494:pharmacology
D011433:Propranolol