Cardiac manifestations of primary hypothyroidism. Determinant factors and treatment response

Objective: Previous studies have not fully established the magnitude and determinant factors of cardiac manifestations of primary hypothyroidism. This study was aimed to assess the effects of thyroid deficiency on cardiac performance and structure.

Methods: We studied by echocardiography 19 patients with overt and 23 with subclinical hypothyroidism, and 21 control subjects. Patients were restudied one year after L-thyroxine therapy. Systolic function was assessed by the observed/predicted fractional shortening ratio. The predicted fractional shortening was calculated from the inverse relation of fractional shortening to end-systolic stress (p < 0.0001) in normal subjects.

Results: The observed/predicted fractional shortening ratio was lower (p = 0.043) and left ventricular mass was higher (p = 0.028) in overt hypothyroidism than in subclinical hypothyroidism and control subjects. By multivariate analysis, fractional shortening ratio was related to thyroxine levels (p = 0.0002), systemic vascular resistance (p = 0.0001) and age (p = 0.0009), and left ventricular mass was related to thyroxine levels (p = 0.0004) and weight (p = 0.0001). Pericardial effusion was observed in 37% of patients with overt hypothyroidism and 9% of patients with subclinical hypothyroidism (p = 0.03), and was mainly related to TSH levels (p = 0.0098). Hormone replacement therapy increased systolic function in overt hypothyroidism. Left ventricular mass did not change after therapy. Pericardial effusion disappeared in all patients.

Conclusions: Primary hypothyroidism produces a decrease in myocardial contractility and an increase in left ventricular mass, both related to the severity of hormone deficiency. Pericardial effusion is mainly related to thyrotrophin plasma levels. Most of cardiac manifestations of hypothyroidism reverse with L-thyroxine therapy.