Noninvasive Evaluation of Cardiac Function in Hypothyroidism

Abstract

Left ventricular performance was studied in 15 patients with severe, primary hypothyroidism (mean serum total thyroxine of 0.8 mug per 100 ml and serum thyrotropin of 160 muU per milliliter). Pretreatment systolic-time intervals were characterized by prolongation of the pre-ejection period (delta PEP = +30) and reduction of the left ventricular ejection period (delta LVET = -23) with a resultant increase in the PEP/LVET ratio (0.47). Nine of 14 patients demonstrated pericardial effusions. These abnormalities were reversed with physiologic thyroxine replacement. Further reductions of the delta PEP and PEP/LVET ratio occurred with supraphysiologic doses (200 to 300 mug per day). During therapy, delta PEP was inversely correlated with serum thyroxine (P less than 0.001) and directly correlated with serum thyrotropin (P less than 0.001). Thus physiologic thyroid hormone replacement, appropriately adjusted to need, appears necessary in hypothyroidism for optimal left ventricular function.

Thyroid Disease and the Heart

“…3 It is important to recognize, however, that the restoration of normal cardiovascular hemodynamics can occur without a significant increase in resting heart rate in the treatment of hypothyroidism. 28 Whereas the effects of T 3 on the heart are well recognized, the ability of thyroid hormone to alter VSM and endothelial cell function are also important. In the VSM cell, thyroid hormone-mediated effects are the result of both genomic and nongenomic actions.…”

“…10,28 Overt hypothyroidism affects Ϸ3% of the adult female population and is associated with increased SVR, decreased cardiac contractility, decreased cardiac output, and accelerated atherosclerosis and coronary artery disease. 6,28,95 These findings may be the result of increased hypercholesterolemia and diastolic hypertension in these patients. 96 Hypothyroid patients have other atherosclerotic cardiovascular disease risk factors and an apparent increase in risk of stroke as well (Table 4).…”

“…10,101 Most, if not all, of the changes in cardiac structure and function associated with hypothyroidism are responsive to T 4 replacement. 28,101 The treatment of hypothyroidism in the setting of known or suspected cardiac disease poses some challenges. In young, otherwise healthy patients with overt hypothyroidism, treatment with a full replacement dose of L-thyroxine (Levoxyl, Synthroid) of Ϸ1.6 g/kg per d can be initiated at the outset.…”

“…When so treated, a predictable improvement occurs in thyroid and cardiovascular functional measures. 28 Concerns that restoration of the heart to a euthyroid state might adversely affect underlying ischemic heart disease are largely unfounded. As reported by Keating, 102 patients with …”

Hypothyroidism Presenting as Dilated Cardiomyopathy

“…Most consistent cardiac abnormality recognized in patients with overt hypothyroidism is impairment of LV diastolic function which is characterized by slowed myocardial relaxation and impaired early ventricular filling [8,9]. LV systolic function is only marginally subnormal.…”