Hypothyroidism arrhythmia with

Thyroxine is used in hypothyroidism, a condition that may well present in elderly patients. Side-effects of thyroxine usually occur at excessive doses and include gastrointestinal disturbances (nausea, vomiting) as well as cardiac symptoms such as angina pain, arrhythmias, palpitation and tachycardia. Thyroxine should be used with caution in elderly patients as they are more prone to side-effects. A lower initial dose (25-50 pg daily) is recommended for patients who are over 50 years. Dose adjustments should take place at intervals of at least 4 weeks. A pretreatment electrocardiogram is recommended because changes induced by hypothyroidism (that would be present at baseline) may be confused with ischaemia. 

In patients with longstanding hypothyroidism and those with ischemic heart disease, rapid correction of hypothyroidism may precipitate angina, cardiac arrhythmias, or other adverse effects. For these patients, replacement therapy should be started at low initial doses, followed by slow titration to full replacement as tolerated over several months. If hypothyroidism and some degree of adrenal insufficiency coexist, an appropriate adjustment of the corticosteroid replacement must be initiated prior to thyroid hormone replacement therapy. This prevents acute adrenocortical insufficiency that could otherwise arise from a thyroid hormone-induced increase in the metabolic clearance rate of adrenocortical hormones. 

However, torsades de pointes does not occur in every patient who is treated with these drugs. Large intraindividual variations in QT prolongation are common. Other factors that may predispose to this arrhythmia include hypokalemia, hypomagnesmia, hypothyroidism, renal failure, and congestive heart failure (95, 97, 101, 102). 

Chronic therapy with amiodarone has been associated with pulmonary interstitial pneumonitis/alveolitis, hypersensitivity pneumonitis, and pulmonary fibrosis fatalities have resulted. Other side effects include elevated liver function tests, worsening of arrhythmias, onset of new arrhythmias, fatigue, tremor, involuntary movements, dizziness, paresthesias, difficulty in walking, hypothyroidism, hyperthyroidism, nausea, vomiting, constipation, anorexia, corneal... 

With chronic use, amiodarone may cause ventricular arrhythmias (mono-morphic or polymorphic ventricular tachycardia see p 14) or bradyanhyth-mias (sinus arrest, AV block). Amiodarone may cause pneumonitis or pulmonary fibrosis, hepatitis, photosensitivity dermatitis, comeal deposits, hypothyroidism or hyperthyroidism, tremor, ataxia, and peripheral neuropathy. 

A number of other reports describe very significant reductions in endogenous markers of thyroid function in subjects and patients taking phenytoin or carbamazepine, " but not sodium valproate. However, there seems to be only two cases in which reversible hypothyroidism was seen, one with carbamazepine and phenytoin, and the other with carbamazepine alone. There is also a report of an arrhythmia in a patient with hypothyroidism and rheumatic heart disease given phenytoin this was attributed to the displacement of protein bound levothyroxine by phenytoin leading to an increase in free levothyroxine in the plasma. This report was later criticised by others, who suggested that the arrhythmia, if indeed there was one, was caused directly by the cardiac actions of... 

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