Cardiac performance in hyperthyroidism assessed by systolic time intervals and radionuclide ventriculography

Systolic time intervals (STI) and radionuclide ventriculography (RNV) were used in the assessment of cardiac performance in 22 patients with hyperthyroidism before and after antithyroid treatment. STI as well as RNV showed enhanced myocardial contractility which was normalized after antithyroid treatment. Beta-blocker treatment did not influence the hypercontractility in hyperthyroidism. This implies that beta-blockers alone cannot be regarded as satisfactory long-term treatment and that mechanisms other than increased sympathoadrenal drive are involved in the hypercontractility in hyperthyroidism. RNV suggested valvular regurgitation, probably of the mitral valve, in 11 patients. Possible hemodynamic consequences are discussed.