Ungulates heart model: a study of the Purkinje network using India ink injection, transparent specimens and computer tomography

The Purkinje network is not macroscopically visible in human hearts. Sunao Tawara found himself in trouble in the early 1900s, when studying the human heart network. He gained a much better understanding of the net after starting to work with ungulates’ hearts. The ungulate heart is proposed as an auxiliary didactic model for the study of the human conduction system. This work provides a detailed description of the India ink injection technique to allow a naked eye visualization of the Purkinje network. The heart muscle was made diaphanous for direct visualization of the ungulate heart intramyocardial network, and computer tomography was employed for visualization of the three dimensional structure of the whole network. The intramyocardial network in the interventricular septum was identified. The pattern of the Purkinje network is described as a connected noneulerian graph, and its possible implications on the mechanism of arrhythmias is discussed. The main differences between the ungulate and human heart conduction systems are stressed.