Concurrent Aortic and Mitral Valve Echocardiography Permits Measurement of Systolic Time Intervals as an Index of Peripheral Tissue Thyroid Functional Status*

Abstract

Systolic time intervals (STI) were measured directly from concurrent aortic and mitral valve echocardiographic tracings in 127 subjects to assess their utility as an index of peripheral tissue thyroid functional status. The subjects were categorized according to clinical symptoms and the results of thyroid function tests into the following 7 study groups: normal subjects (n = 34), overt hyperthyroid subgroup I (n = 12), overt hyperthyroid subgroup II (n = 28), subclinical hyperthyroid (n = 15), subclinical hypothyroid (n = 22), overt hypothyroid subgroup II (n = 6), and overt hypothyroidism subgroup I (n = 10). Compared with normal subjects, overt hyperthyroid subgroup I patients had a significantly shortened mean isovolumetric contraction time (ICT), preejection period (PEP), and PEP/LVET (LVET = left ventricular ejection time; P less than or equal to 0.0005); the overt hypothyroid subgroup I patients also had significantly lengthened mean ICT (P less than or equal to 0.005), PEP, and PEP/LVET (P less than or equal to 0.0005). Compared with normal subjects, overt hyperthyroidism subgroup II patients also had a very significant shortening of ICT (P less than 0.0005) as well as a significantly shortened PEP and PEP/LVET (P less than or equal to 0.005), whereas subclinical hyperthyroid patients (with normal serum free T4 index and total T3, and suppressed TSH by immunoradiometric assay) also had ICT, PEP, and PEP/LVET STI values which were significantly shortened (P less than 0.05) values. Compared to normal subjects, the overt hypothyroid subgroup II patients (who were clinically asymptomatic with reduced serum free T4 index and elevated TSH) had a prolongation of ICT, PEP, and PEP/LVET (P less than or equal to 0.05), whereas the values in subclinical hypothyroid patients were similar to those in normal subjects. From these observations we conclude that in the absence of underlying heart disease, the echocardiographic method used is a rapid, reliable, and sensitive technique for determining STI and provides direct information on peripheral tissue thyroid functional status.