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Figure 2 Cardiomotor function and response to isoproterenol between control subjects and isoproterenol-positive patients. (A) Percentage change in heart rate, stroke volume and cardiac output during isoproterenol infusion (0.05 µg/kg per min) in the supine position compared with baseline supine position. (B) Percentage change in heart rate, stroke volume and cardiac output during isoproterenol infusion from supine to tilt position.