The QS2/QT ratio as an index of appropriate left ventricular response to autonomic and inotropic stimuli.

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Dissociation between duration of electrical and mechanical systole has been seen with increase of myocardial shortening velocity or adrenergic activity. We found a decrease of the QS2/QT ratio after exercise in 10 pts with semisitting bicycle maximal exercise test and a normal radionuclide angiogram. No change was seen in 9 patients with a normal study with beta blockade, and in pts with a abnormal radionuclide test, without beta blockade (11 pts). In 19 normal active individuals, a significant QS2/QT decrease (p less than 0.001) was seen after a submaximal exercise treadmill test, which was inhibited by beta blockade. We believe that QS2/QT diminution is suggestive of an increase of the inotropic state of the left ventricle with exercise, produced through adrenergic stimulation. It is not seen either when an ischemic left ventricle cannot adequately respond to exercise or after beta blockade.

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