An equilibrium radionuclide technique to assess the effect of propranolol on left ventricular function in thyrotoxicosis.

Radionuclide imaging of the left ventricular blood pool provides a convenient non-invasive method of monitoring left ventricular function. Left ventricular function is characterised by the left ventricular curve which represents all phases of the cardiac cycle and is obtained by a multiple gated equilibrium method (MUGA). Volume curves were obtained over a minimum 1 1/2 h period in 15 normal subjects and in 20 thyrotoxic patients. Changes in left ventricular ejection fraction (LVEF), maximum ejection fraction rate and total electromechanical time interval were recorded from volume curve data. To assess the effect of pharmacological intervention, serial measurements of LVEF were made before and after 40 mg oral propranolol. In thyrotoxic patients, LVEF decreased by 17% of the initial value and in normal subjects by less than 10% following propranolol. This method can be extended to assess the effects of physiological or pharmacological intervention on left ventricular function in other disease states.