[Arrhythmogenic implications of non-iatrogenic thyroid dysfunction]

We studied all patients with hyperkinetic and hypokinetic arrhythmias, who were recovered in the Cardiology Department and Arrhythmologic Centre of S. Chiara Hospital in Trento between 1983 and 1987. From these we selected all the patients who, on admission, had clinical and biochemical symptoms of dysthyroidism. Of the 2465 patients with cardiac arrhythmias, 93 (3.8%) had an evident thyroid pathology which was due to chronic amiodarone treatment in 42 (44.6%) and was primary and non-iatrogenic in 51 (55.4%). In the latter the thyroid pathology consisted of hyperthyroidism in 43 cases (toxic nodular goitre or Graves' disease), and of hypothyroidism in 8. As regard the types of arrhythmias, hyperthyroidism is predominant in patients with atrial fibrillation (70%) and in those with paroxysmal supra-ventricular reciprocating tachycardia (11.5%), but it is also present in patients with hyperkinetic ventricular arrhythmias (14%). Hypothyroidism is found in patients with hyperkinetic ventricular arrhythmias (25%), atrial fibrillation (37.5%) and atrio-ventricular block (37.5%). The average age of the hyperthyroid population with atrial fibrillation is higher than that of patients with paroxysmal supraventricular reciprocating tachycardia. The control of the thyroid pattern, especially as regards atrial fibrillation and paroxysmal supraventricular reciprocating tachycardia results in absence of arrhythmic episodes even without treatment in 40% of cases, and in an easier drug control in the other cases. Our study indicates that it is necessary to carry out systematic research of a thyroid dysfunction in all patients with cardiac arrhythmias, especially as regards women, atrial fibrillation and paroxysmal supraventricular reciprocating tachycardia. It is also evident that in order to achieve long-term control over hyperkinetic arrhythmia it is very important to overcome hyperthyroidism.