Bieganowska K, Kubicka K, Stopczyk M, Oficjalska B. Pediatr Pol 1989 May;64(5):295-303. The conduction system of the heart was studied in 41 patients with cardiac arrhythmias by oesophageal stimulation of the left atrium. 31 children had a history of paroxysmal supraventricular tachycardia, 5 supraventricular or/and ventricular premature beats and 5 were studied because of suspected bradycardia-tachycardia syndrome. In all patients stimulation of the left atrium was well tolerated. There were no side effects or complications. The results showed that oesophageal stimulation of the left atrium was a faithful noninvasive method in diagnostic studies of the conduction system of the heart. This method was effective in studying the mechanism of supraventricular arrhythmias.