methimazole and Arrhythmias--Cardiac

Hypothyroidism is associated with an increased risk of cardiovascular disease and enhanced susceptibility to arrhythmias. In our investigation, we evaluated the potential involvement of late sodium current (I. Male Swiss mice were treated with methimazole (0.1 % w/vol, during 21 days) to induce experimental hypothyroidism before ECG, action potential (AP) and intracellular Ca. The results revealed that hypothyroid animals presented ECG alterations (e.g. increased QTc) with the presence of spontaneous sustained ventricular tachycardia. These changes were associated with depolarized resting membrane potential in isolated cardiomyocytes and increased AP duration and dispersion at 90 % of the repolarization. Aberrant AP waveforms were related to increased Ca. We concluded that animals with hypothyroidism have increased susceptibility to developing arrhythmias and ranolazine, a clinically used blocker of I

Topics: Action Potentials; Animals; Arrhythmias, Cardiac; Caffeine; Dobutamine; Hypothyroidism; Male; Methimazole; Mice; Myocytes, Cardiac; Phenotype; Ranolazine; Sodium

Amiodarone-induced hyperthyroidism is a known side effect of amiodarone treatment. In the pediatric population, long-term amiodarone treatment is rarely indicated because of its severe side effects including thyroid function impairment. Treatment is therefore restricted to therapy-resistant arrhythmias. In the literature, scarce data are available on the management and therapy of amiodarone-induced thyroid dysfunction at a young age. We present three adolescent patients developing amiodarone-induced thyrotoxicosis in the months after amiodarone therapy. A latency period for thyroid dysfunction has been described in adulthood but was not previously reported in pediatric patients. The gap between amiodarone treatment and the development of symptoms and the diagnosis of hyperthyroidism was between 3 and 10 months. In two patients, hyperthyroidism was transient and resolved without treatment. These two patients, one boy and on girl, were almost asymptomatic. In contrast, in one male patient overt and severe hyperthyroidism developed. We began treatment with thiamazole without benefit. Control of hyperthyroidism was achieved under prednisone treatment, which was continued for 9 months. Clinical evaluation proved an amiodarone-induced destructive thyroiditis in this patient. Amiodarone-induced thyroid dysfunction is frequent also in pediatric patients with long-term amiodarone treatment. Patients and clinicians should be aware of the impact of amiodarone on thyroid function during and also in the months and maybe years after treatment. Careful follow-up is needed, as symptoms might be associated with the underlying cardiac disease in these patients. Amiodarone-induced thyrotoxicosis often resolves without treatment but can be challenging in some cases.

Topics: Adolescent; Amiodarone; Anti-Arrhythmia Agents; Antithyroid Agents; Arrhythmias, Cardiac; Female; Glucocorticoids; Humans; Hyperthyroidism; Male; Methimazole; Prednisolone; Thyroid Function Tests; Thyroid Gland

Dome-and-dart T waves (or bifid T waves) are a rare phenomenon in the surface electrocardiogram. These wave forms are mainly observed in patients with congenital heart disease such as atrial septal defect and ventricular septal defect. And hyperthyroidism who presented with an electrocardiogram that had dome-and-dart T waves in a precordial lead is never been reported.. The patient presented with continuous tachycardia, palpitations, chest tightness, and headache for 4 days, and aggravated for 1 day.. Hyperthyroidism.. Methimazole.. All symptoms were alleviated.. Dome-and-dart or bifid T waves have been reported in the conventional 12-lead electrocardiograms in some patients with congenital heart disease. The case illustrated here, to the best of our knowledge, dome-and-dart or bifid T waves may associate with hyperthyroidism patients.

Topics: Adolescent; Antithyroid Agents; Arrhythmias, Cardiac; Electrocardiography; Humans; Hyperthyroidism; Male; Methimazole

Topics: Animals; Antithyroid Agents; Arrhythmias, Cardiac; Cat Diseases; Cats; Electrocardiography; Female; Hyperthyroidism; Methimazole; Pacemaker, Artificial

Topics: Animals; Antithyroid Agents; Arrhythmias, Cardiac; Cat Diseases; Cats; Electrocardiography; Hyperthyroidism; Methimazole

Topics: Animals; Antithyroid Agents; Arrhythmias, Cardiac; Cat Diseases; Cats; Electrocardiography; Female; Hyperthyroidism; Methimazole

Topics: Adult; Anti-Arrhythmia Agents; Antithyroid Agents; Anxiety; Arrhythmias, Cardiac; Dyspnea; Graves Disease; Humans; Hypokalemic Periodic Paralysis; Malaysia; Male; Methimazole; Muscle Weakness; Neurologic Examination; Potassium; Propranolol; Propylthiouracil; Sleep Initiation and Maintenance Disorders; Tremor; Weight Loss

We report the treatment of four thyrotoxic patients. Two were cases of type I amiodarone-induced thyrotoxicosis (AIT) treated with methimazole. The third Graves' disease patient, who became hypothyroid 25 years after subtotal thyroidectomy, developed type II AIT. Furthermore, one case with heart failure and ventricular tachycardia, who developed an adverse reaction to antithyroid agents and was prescribed amiodarone, underwent total thyroidectomy. The clinical course was uneventful, and the patient is doing well. Since amiodarone contains a large amount of iodine, it is frequently difficult to make a differential diagnosis. Surgical treatment of Graves' disease patients is recommended when immediate control of hyperthyroidism and heart failure is required.

Topics: Adult; Amiodarone; Anti-Arrhythmia Agents; Antithyroid Agents; Arrhythmias, Cardiac; Diagnosis, Differential; Graves Disease; Humans; Male; Methimazole; Middle Aged; Thyroidectomy; Thyrotoxicosis

Subclinical hyperthyroidism has been associated with harmful cardiac effects, but its treatment remains controversial. This study was designed to assess the cardiac effects of the normalization of serum TSH concentration in patients with endogenous subclinical hyperthyroidism. Ten patients (median age, 59 yr; range, 16-72 yr) with normal serum free T(4) and free T(3) concentration and a stable suppression of serum TSH levels were evaluated by Doppler-echocardiography, by standard and 24-h electrocardiography monitoring (Holter), and by the clinical Wayne index. Ten subjects, matched for age and sex, were used as controls. Patients were reevaluated 6 months after achieving stabilized euthyroidism by using methimazole with a median initial dose of 20 mg daily (10-30 mg daily). After reaching euthyroidism, we found a significant decrease in the heart rate (P = 0.008), the total number of beats during 24 h (P = 0.004), and the number of atrial (P = 0.002) and ventricular (P = 0.003) premature beats. Echocardiographical data resulted in a reduction of the left ventricular mass index (P = 0.009), interventricular septum thickness (P = 0.008), and left ventricular posterior wall thickness (P = 0.004) at diastole. Furthermore, the early diastolic peak flow velocity deceleration rate was significantly higher (P = 0.02) in the untreated patients compared with controls. The Wayne clinical index was higher in patients than in controls (P = 0.001) and decreased after treatment (P = 0.004). Serum TSH concentration returned to normal values after 2.5 months (range, 1.0-7.0 months) on methimazole therapy (0.05 vs. 1.42 mU/liter; P = 0.002). Serum free T(4) values were normal in patients before treatment but significantly decreased after reaching the euthyroidism (16.9 vs. 11.5 pmol/liter; P = 0.002). In contrast, serum free T(3) concentration did not differ among the groups. In conclusion, our findings support that early antithyroid therapy should be considered in patients with endogenous subclinical hyperthyroidism, where it is needed to prevent potential progression to a more advanced heart disease.

Topics: Adolescent; Adult; Aged; Antithyroid Agents; Arrhythmias, Cardiac; Diastole; Echocardiography; Electrocardiography; Female; Heart Diseases; Heart Rate; Heart Ventricles; Humans; Hyperthyroidism; Male; Methimazole; Middle Aged; Systole; Thyroid Gland; Thyrotropin; Thyroxine; Triiodothyronine

We examined the contribution of hypothyroidism to streptozotocin diabetes-induced alterations in the arrhythmia susceptibility of ex vivo hearts to regional zero-flow ischaemia. Diabetic rats received either protamine zinc insulin (10 IU/kg/day, s.c.) or triiodothyronine (10 microg/kg/day, s.c.) for 8 weeks commencing 72 h after injection of streptozotocin (60 mg/kg, i.p.). Arrhythmias were determined in ex vivo Langendorff-perfused hearts, subjected to a 30-min main left coronary artery occlusion, followed by 30-min reperfusion. Serum free thyroxine concentrations, rectal temperature and ex vivo heart rate were significantly decreased in the 8-week diabetic group (P<0.001). These changes were prevented by administration of triiodothyronine or insulin. Ventricular fibrillation during reperfusion was abolished in hearts from diabetic rats. This protection was prevented by treatment with either triiodothyronine or insulin. Hearts from methimazole-hypothyroid rats also showed no ventricular fibrillation during reperfusion. The protection against ischaemia-reperfusion-arrhythmias observed in hearts from streptozotocin-diabetic rats may be due to diabetes-induced hypothyroidism.

Topics: Animals; Arrhythmias, Cardiac; Blood Glucose; Body Temperature; Body Weight; Diabetes Mellitus, Experimental; Disease Models, Animal; Heart; Heart Rate; Hypothyroidism; Insulin; Long QT Syndrome; Male; Methimazole; Myocardial Ischemia; Myocardial Reperfusion Injury; Organ Size; Protein Kinase C; Rats; Rats, Sprague-Dawley; Streptozocin; Thyroid Hormones; Triiodothyronine; Ventricular Fibrillation

A 58-year-old woman was admitted because of jaundice, ascites and marked oedema. For three years she had suffered from nervousness, decreasing fitness and weight loss, which had been assumed as due to chronic alcoholism. Liver biopsy revealed extensive fibrosis, in part with early cirrhotic transformation. This was followed by cardiac failure with atrial fibrillation (ventricular rate 140/min) and marked pleural effusions. The thyroid was diffusely enlarged and there were signs of exophthalmos.. Bilirubin concentration was 3 mg/dl, lactate dehydrogenase activity was 310 U/l, cholesterase 1.3 kU/l and the prothrombin test was 21%. The TSH level was 0.01 microU/ml while the free thyroxine level was 4.7 ng/dl and that of free triiodothyronine 13.5 pg/ml. Chest radiograph revealed cardiomegaly, bilateral peripheral pulmonary congestion and pleural effusions to midfield. Right heart catheterization excluded pulmonary hypertension; cardiac output was 10l/min. The thyroid was enlarged on ultrasound and diffusely echopoor, as in immune thyroid disease.. Cardiac failure regressed and thyroid function normalized within ten days on propranolol, 4 x 40 mg and thiamazole 3 x 40 mg daily intravenously. Subtotal thyroidectomy was performed three weeks later with subsequent thyroid hormone substitution. Liver functions were normal six months later and ultrasound showed no signs of cirrhotic change and the ascites had resolved.. Hyperthyroidism is frequently associated with changes in liver functions. In extreme cases, high-output cardiac failure may occur, with liver congestion and clinical as well as histological changes like those in liver cirrhosis.

Topics: Adrenergic beta-Antagonists; Anti-Arrhythmia Agents; Antithyroid Agents; Arrhythmias, Cardiac; Autoimmune Diseases; Female; Heart Failure; Humans; Hyperthyroidism; Liver Cirrhosis; Methimazole; Middle Aged; Propranolol; Thyroid Hormones; Thyroidectomy; Ultrasonography

To exploit the antiarrhythmic effect of amiodarone when patients develop the side effect of thyrotoxicosis three patients with hyperthyroidism induced by amiodarone were given simultaneously 1 g potassium perchlorate a day for 40 days and a starting dose of 40 mg methimazole a day while they continued to take amiodarone. As hyperthyroidism might have recurred after potassium perchlorate treatment was stopped the dose of methimazole was not reduced until biochemical hypothyroidism (raised thyroid stimulating hormone concentrations) was achieved. The patients became euthyroid (free triiodothyronine concentration returned to normal values) in two to five weeks and hypothyroid in 10 to 14 weeks. One patient became euthyroid while taking 5 mg methimazole a day and 600 mg amiodarone weekly; the two others required substitution treatment with thyroxine sodium while taking 5 mg methimazole or 50 mg propylthiouracil (because of an allergic reaction to methimazole) and 2100 or 1400 mg amiodarone weekly. Hyperthyroidism induced by amiodarone may be treated with potassium perchlorate and methimazole given simultaneously while treatment with amiodarone is continued.

Topics: Aged; Amiodarone; Arrhythmias, Cardiac; Drug Evaluation; Drug Therapy, Combination; Humans; Hyperthyroidism; Methimazole; Middle Aged; Perchlorates; Potassium; Potassium Compounds; Thyroid Gland

Investigations of the heart automatism were carried out in 10 patients with hyperthyreoidism before thiamazol therapy and after restoration of the euthyroid status. A control group was comprised of 34 healthy subjects. In order to determine the electrophysiologic parameters the transoesophageal atrium extrastimulus technique and the over-driving stimulation were applied. Restoration of the euthyroid status was accompanied by a significant prolongation of the atrial refraction, the border interval, the border conductivity and the sinus rhythm recurrence time. In a half of the patients were atrioventricular and intraventricular conductibility disturbances observed. The authors conclude, that in the early period of the euthyroid status restoration after thiamazole therapy there still exists a risk of cardiologic complications.

Topics: Adult; Arrhythmias, Cardiac; Cardiac Pacing, Artificial; Dose-Response Relationship, Drug; Electrocardiography; Female; Heart Conduction System; Heart Rate; Humans; Hyperthyroidism; Male; Methimazole; Thyroid Function Tests

Topics: Adult; Arrhythmias, Cardiac; Back; Chronic Disease; Electromyography; Extremities; Female; Graves Disease; Humans; Hyperthyroidism; Male; Methimazole; Methylthiouracil; Middle Aged; Muscular Diseases; Paralyses, Familial Periodic; Sex Factors