[Somatostatin and the cardiovascular system: experiences and prospective use]

The recent demonstration that intravenous administration of somatostatin, an ubiquitous peptide-like substance, may interrupt paroxysmal supraventricular tachycardia in man has disclosed new perspectives in the assessment of the mechanisms of neuro-humoral cardiac regulation in normal and pathologic conditions. Prospective studies on normal subjects and diabetics with and without autonomic cardiac neuropathy, helped in giving an outlook on the mechanism by which somatostatin acts on the human heart. This substance exerts in vivo a powerful chronotropic and dromotropic influence on sinoatrial and A-V node cells both in normals and diabetics with and without autonomic cardiac neuropathy. This influence is blocked by preventive administration of atropine or atropine plus metoprolol (intrinsic heart rate). Since somatostatin-like-substances have been found in cholinergic postganglionic neurons of the cardiac vagus of some animals, the demonstrated "vagomimetic" action of somatostatin on human cardiac cells seems to support the hypothesis that also the human heart may contain vagal somatostatinergic neurons with modulatory function on the heart rate and rhythm. Present observations disclose new perspectives in the pathophysiology and therapy of cardiac arrhythmias.