Severe Short-Term Hypothyroidism Is Not Associated with an Increased Incidence of Myocardial Ischemia as Assessed by Thallium-201 Stress/Rest Myocardial Scintigraphy

Abstract

Reversible silent myocardial ischemia associated with treatment of long-standing hypothyroidism has recently been reported using thallium-201 (201Tl) myocardial single photon emission tomography (SPET). The aim of the present study was to evaluate whether patients with short-term hypothyroidism (serum thyrotropin [TSH] levels above 30 mU/L) have an increased risk of silent myocardial ischemia. We studied 20 patients with differentiated thyroid carcinoma that had undergone thyroidectomy and ablative (131)I therapy. None of the patients had a known history of atherosclerotic cardiovascular disease. In the course of a planned follow-up examination, suppressive levothyroxine (LT4) therapy was discontinued 7 weeks prior to scintigraphy and replaced by triiodothyronine (T3) therapy for 4 weeks. No thyroid hormone medication was given during the 3 weeks preceding the diagnostic procedures. All patients were hypothyroid (TSH 87.2 +/- 30.8 mU/L, mean +/- SD) at the time of the examination. 20lTl-SPET was performed immediately after bicycle exercise stress test and again after a delay of 4 hours. In case of abnormal results, (n = 3) the examination was repeated after patients were euthyroid. Two patients showed effects of soft-tissue attenuation (breast attenuation in a female and diaphragmatic attenuation in a male subject). Myocardial ischemia was revealed in 1 patient but was seen in both hypothyroid and euthyroid examinations. The results of the present study show that short-term severe hypothyroidism as encountered in athyreotic patients after cessation of thyroxine medication for several weeks, is not associated with an impairment of myocardial perfusion.

How to Manage Treatment of Hypothyroidism in Patients with Cardiac Disease

“…Even very severe shortterm hypothyroidism is not associated with an increased incidence of myocardial ischaemia. 15 On the other hand, most hypothyroid patientsparticularly the elderly who may also have concomitant heart disease -have developed the hypothyroidism over years, and it is therefore most often advised to initiate replacement very slowly and to carry out titration at long intervals. In patients with ischaemic heart disease it may even be necessary to perform a stress test and/or coronary angiography before starting treatment.…”