ABSTRACT
Hypothyroidism is not infrequently associated with an abnormally long QTc interval (> or = 450 msec). Rarely, marked prolongation of the QTc interval and malignant ventricular arrhythmias have been reported. In this study, QTc intervals on resting electrocardiograms (ECGs) were compared in 10 patients before and after treatment of hypothyroidism. The QTc interval increased in seven patients during euthyroidism compared with hypothyroidism, and decreased in three patients. During hypothyroidism, the QTc interval was mildly prolonged in 2 of the 14 patients; both had mild decreases in triiodothyronine (T3) or thyroxine (T4). The 24-hour ambulatory ECGs measured during hypothyroidism and after restoration of biochemical euthyroidism also were compared in 9 patients. There was no significant difference in ventricular ectopy. None of the 13 patients assessed during hypothyroidism had > or = 4 beats of ventricular tachycardia. There was no relationship between thyroid-stimulating hormone (TSH) or T3 levels and QTc intervals during hypothyroidism. A moderate correlation between lesser degrees of T4 depression and increasing QTc interval was present. Mild QTc prolongations are relatively common in patients with hypothyroidism and are usually associated with milder degrees of thyroid underactivity, but are not associated with clinically significant ventricular tachyarrhythmias.
Subject(s)
Electrocardiography , Hypothyroidism/physiopathology , Long QT Syndrome/physiopathology , Adult , Aged , Female , Humans , Hypothyroidism/blood , Hypothyroidism/complications , Long QT Syndrome/blood , Long QT Syndrome/complications , Male , Middle Aged , Statistics, Nonparametric , Thyrotropin/blood , Thyroxine/blood , Triiodothyronine/bloodSubject(s)
Myxedema/complications , Shock, Cardiogenic/drug therapy , Shock, Cardiogenic/etiology , Triiodothyronine/therapeutic use , Administration, Oral , Drug Therapy, Combination , Female , Humans , Injections, Intravenous , Middle Aged , Myxedema/drug therapy , Thyroxine/therapeutic use , Triiodothyronine/administration & dosageABSTRACT
Synthetic amino acid medium for fungi (SAAMF) is a totally defined, nutritionally adequate, macromolecule-free culture medium for fungi that is buffered with an organic weak acid-weak base pair: 2-(N-morpholino)-propanesulfonic acid (MOPS) and 2-amino-2-(hydroxymethyl)-1,3-propanediol (Tris). In 1984, it was reported that MOPS-Tris in SAAMF antagonized the activity of flucytosine against Candida albicans (D. L. Calhoun and J. N. Galgiani, Antimicrob. Agents Chemother. 26:364-367, 1984). Accordingly, we evaluated the buffering capacity of seven synthetic organic buffers and monobasic potassium phosphate, both singly and in pairs, over the pH range 7.4 to 6.0. Of these buffers, MOPS, BES [N,N-bis(2-hydroxyethyl)-2-aminomethanesulfonic acid], a BES-MOPS combination, and KH2PO4 provided the best buffering. Growth of C. albicans, in unbuffered SAAMF was equivalent overall to that in SAAMF containing buffers, singly or in pairs. Twelve strains of C. albicans and five strains of Candida lusitaniae were tested for susceptibility to flucytosine in SAAMF, with and without buffers. In the presence of Tris, the geometric mean MICs were 6.5- and 3.6-fold higher, respectively, for C. albicans and C. lusitaniae. We recommend replacing Tris with the nonantagonistic MOPS.
