[Effect of somatostatin on the conduction system of the heart]

Somatostatin (S), a naturally occurring peptide, was first discovered more than 20 years ago. This peptide was later found in many tissues, including human cardiac tissue. High concentration of S was found in the sinus and atrioventricular (AV) nodes. Negative chronotropic activity of S and depressive effects of this substance on AF junction have also been described. The purpose of the present study was to determine the effect of S on the cardiac conduction system in man during antegrade and retrograde conduction. The study group consisted of 12 pts (5 women and 7 men, mean age 43 years). They were subjected to invasive electrophysiologic testing because of sudden unexplained heart palpitations. After measuring all electrophysiologic variables in the control state, each patient was given S (preparation Stilamin, Serono) intravenously with a syringe pump at a dose of 8.5 micrograms/min, for about 30 min. All the electrophysiologic measurements were repeated in the same order, beginning from the 6th min after the start of S injection. S prolonged mean sinus cycle length by 13%, sinoatrial, intraatrial and AV nodal conduction times by 15, 9 and 10%, respectively. Effective refractory periods of the atrium, AV node and right ventricle were prolonged by 7, 8 and 8%, respectively (all p values less than 0.01). Antegrade AV nodal Wenckebach cycle length, as well as retrograde, increased significantly (by 9 and 10% respectively). There were no significant changes of the mean HV interval, corrected QT interval, ventriculoatrial conduction time and corrected sinus node recovery time during S infusion.(ABSTRACT TRUNCATED AT 250 WORDS)