Idio-ventricular periodicity

When the excised heart of the frog is perfused under certain conditions, the beats lose their normal regularity, and occur in periodic groups with a long pause between every two groups this phenomenon was first investigated systematically by Luciani in 1872, and in consquence, the groups are often referred to as “Luciani groups.” They are not infrequently seen in experiments in which a Symes cannula, inserted into the heart through the inferior vena cava or sinus venosus, is kept in place by a ligature tied between the sinus venosus and the auricles, in the position of the first Stannius ligature. When the ligature is tied, the auricles and ventricles cease to beat, but if the heart is excised and then perfused through the cannula by Symes’s method, the whole heart usually beats again, and the beats may show periodic grouping before settling down to a normal regularity. Sometimes, too, groups occur in hearts in which the perfusion by Symes's method has been going on for some time and the heart has been beating regularly. The condition of occurrence of the groups have been studied by several physiologists, and the general opinion seems to be, like that of Gaskell, that they are due to an asphyxial state of the heart, that the pauses indicate a complete heart block, and that the groups of beats occur when the block has become only partial, so that some beats are able to get through from sinus venosus to auricles and ventricles.