[Low T3 syndrome and left ventricular diastolic function]

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.

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.

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.

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.