In the seventies thyrotoxic heart accounted for 3% of all hospitalized cardiac patients and was found on average in 30 % of all cases of hyperthyroidism.It presented most frequently by tachyfibrillation and resistant cardiac decompensation. It affected men four times as frequently as women. The incidence correlated with age, toxic nodose goitre, but its development did not correlate with concurrent thyrotoxic rhizomyelic myopathy nor with the extent of deviation of thyroid laboratory parameters (T4, T3, indexes FT4). At present the incidence of thyrotoxic heart declined due to early detection and more adequate diagnosis and treatment of hyperthyroidism, as well as due to the decline of oligosymptomatic toxic nodose goitres even in old age due to preventive iodization of table salt. However, there was an increase of hyperthyroidism induced by amiodarone and other iodine preparations (X-ray contrast materials) associated with primary heart disease and arrhytmias.(Up to 2% of amiodarone treated patients). The ratio of so-called real subclinical thyrotoxicoses in the development of thyrotoxic heart is negligible. Isolated reduction of TSH in hospital screening is a frequnt finding but is conditioned most frequently by: a) the 1st stage of the low thyroxin syndrome, b) the 1st stage of subacute thyroiditis, c) the influence of various drugs (iodine preparations, overdosage of T4 substitution, pharmacotherapy with glucocorticoids, dopamine etc.), d) methodical artefacts, e) natural pulsed secretion of TSH etc. Hospital scree- ning of hyperthyroidism and thyrotoxic heart even in older people above 60 years by T4 and/orTSH (2nd generation equipment) is not effective because it is detected in 20% of current hospital admissions and in 60% of those admitted to intensive care unitpathologic values of T4 and/or TSH most frequently without non-thyroid causes (stages of the low thyroxin syndrome) are recorded. This hospital screening has a satisfactory sensitivity but low specificity and in a large number of people calls for further diagnostic steps. Therefore it is more suitable only after clinical examination of the patient to confirm suspected hyperthyroidism to examine FT4 and TSH (IRMA 3rd generation ) or possibly supplement FT3 and other aimed tests.

        Key words: Thyrotoxic heart - Incidence - Pathogenesis - Arrythmia - Diagnosis