[Low T3 syndrome and left ventricular diastolic function].

Background: Recent data suggest that low triiodothyronine (T3) syndrome may contribute to the pathophysiology of cardiac diseases. Because the development of diastolic dysfunction occurs early in a failing heart, we evaluated whether patients with low T3 syndrome show abnormalities in diastolic function, also in absence of overt cardiovascular disease.

Methods: Thirty-four patients with low T3 syndrome and 34 controls with normal levels of free T3 (FT3) underwent a complete Doppler echocardiographic examination. Criteria of exclusion from the study were the presence of cardiovascular disease or traditional cardiovascular risk factors, a primitive thyroid disease, cachexia, and the use of drugs affecting the thyroid function.

Results: Patients with low T3 syndrome, if compared with controls, show evidence of left ventricular diastolic dysfunction, documented by prolongation of the isovolumic relaxation time (120 vs 75 ms, p < 0.0001) and a reduction in the early diastolic mitral flow velocity/late diastolic mitral flow velocity ratio (0.66 vs 2.05, p < 0.0001), mainly due to the increased A-wave (0.96 vs 0.40 m/s, p < 0.0001). These alterations increase proportionally with FT3 reduction.

Conclusions: Patients with low T3 syndrome show evidence of impaired left ventricular relaxation. Doppler echocardiography may be a useful non-invasive technique for the assessment of diastolic performance in these patients.