Kocot E, Jonderko G, Marcisz C. Z Gesamte Inn Med 1983 Jan 1;38(1):12-5. Electrophysiologic investigations of the heart with the aid of transoesophageal atrium stimulation (extra-stimulus technique and overdriving stimulation) have been performed in 19 patients with primary hypothyroidism and a normal electrocardiogram in standard linkages. The control group comprised 34 healthy persons. In 68% of patients with hypothyroidism there have been stated a prolonged refraction time of the atrium-ventricular and intraventricular conductivity system while in the case of healthy persons an analogic type of changes has been observed only in 12%. Atrium overdriving stimulation has shown a decrease of the atrium-ventricular conductibility at a frequency below 130/min and in 74% of the patients with hypothyroidism the blocking assumed a shape of Wenckebach's periodic.