Reversible Abnormalities of Myocardial Relaxation in Hypothyroidism

Abstract

Fifteen selected hypothyroid patients without symptoms or signs of cardiovascular disease and an equal number of matched control subjects underwent simultaneous recording of electrocardiogram and phono-, apex-, and echocardiography to assess dynamic systolic and diastolic left ventricular function. Both the systolic preejection period and the isovolumic relaxation period were significantly increased in the hypothyroid group. However, whereas the rate of myocardial contraction, assessed from the echocardiograph of the left ventricular posterior wall, was identical in patients and control subjects, the diastolic thinning rate of the muscle was markedly slowed in the hypothyroid individuals. The abnormalities demonstrated were in the main completely reversed after 3 months of T4 therapy. These results demonstrate a relatively selective and readily reversible disturbance of the rate of myocardial relaxation in hypothyroidism, suggesting an intrinsic abnormality of cardiac muscle. This allows an intriguing parallel to be drawn with the delayed relaxation phase of voluntary muscle contraction, long recognized as a direct measure of tissue thyroid function in hypothyroidism. The abnormality of diastolic function we have described is of similar character to that found in patients with other cardiomyopathies and which has been shown to be a major cause of disturbance of global cardiac action.

The Spectrum of Echocardiographic Abnormalities in Hypothyroidism and the Effect of Hormonal Treatment

“…Abnormal left ventricular dimensions and asymmetrical septal thickening also abated. Such resolution of cardiac abnormalities after hormone therapy has been previously documented [8,10,12,18]. However, one notable exception in our patients was regional wall motion abnormality.…”

“…Pericardial effusion has long been known to be a feature of so-called myxedema heart [3]. However, it was the use of echocardiography that established the presence of not previously suspected lesions, indicated by such characteristics as thickening of the interventricular septum [9] and other abnormalities of cardiac muscle [12][13][14][15][16][17][18]. In our study, a wide variety of lesions were found in hypothyroid patients (Tables 1-3).…”

“…Subsequently, there have been several publications on the echocardiographic findings in adults with hypothyroid [10,12], as well as children [13,14] and even neonates [15] with the condition. However, some of these studies had a relatively small number of patients [10,12], relied only on M-mode echocardiography [10,11], or focused primarily on pericardial effusion [9][10][11].…”

“…However, some of these studies had a relatively small number of patients [10,12], relied only on M-mode echocardiography [10,11], or focused primarily on pericardial effusion [9][10][11].…”

Thyroid Hormone Substitution Therapy Rapidly Enhances Left-Ventricular Diastolic Function in Hypothyroid Patients

“…Cardiac output, stroke volume and plasma volume are reduced in hypothyroidism [6, 7], and myocardial contraction and relaxation rates are slowed [7, 8]. Thyroid hormone has been shown to affect calcium uptake by the sarcoplasmic reticulum, to stimulate plasma membrane Ca-ATPase activity and to increase voltage-dependent calcium channels in chick ventricular cells [3, 9].…”