[Sick sinus node syndrome].

The clinical and ECG findings of four cases with sinuatrial nodal disease are reported. The first case is characterized by sharply manifested rhythm bradycardia, the second--be a considerable heterotropic rhythm from the atrioventricular combination, the third--sinu-atrial block and the fourth--typical example of Tachycardisa-Bradycardia syndrome. In all four cases, episodes of syncopes are present, due to an extreme sinus bradycardia, conductivity block in sinu-atrial zone and possible re-entry mechanism of tachycardia paroxysms in case with Tychycardia-Bradycardia syndrome.