The Electrocardiogram of a Beluga Whale

In the course of our study of the comparative anatomy and physiology of the mammalian heart, it became necessary to develop a technic to obtain the electrocardiogram of the largest mammal of all. Because of its availability, the small white Beluga whale in northern waters was the first object of this research, prior to obtaining the record of a large whale, which is our ultimate aim. This article describes the process of obtaining the electrocardiogram and presents the electro-cardiogram itself. T HE relationship of heart size to heart rate and to the time intervals of the electrocardiogram, in particular to the P-R interval and the QRS duration, plays an important role in the interpretation of normal and abnormal human tracings. Having be-come interested years ago in comparative anatomic studies of the auriculoventricular conduction systems of the hearts of the largest mammals, the whale ' and the elephant,2 we took electrocardiograms of several circus ele-phants in 19383 and shortly thereafter, in 1939, conceived of the possibility of obtaining such records of the whale. Our plans for this project were partly made in 1940, but they had to be abandoned temporarily because of the advent of the Second World War. In 1952 when we were at last presented with an opportunity to take an electrocardiogram of a whale, we already possessed certain data concerning the relationship of the size of the heart to its rate and to various time intervals in normal mammals of very different sizes4 as shown in table 1. It remained for us to dis-cover whether or not the largest mammal of all would fit the pattern. Moreover it was necessary to develop the technic to obtain by the use of harpoon electrodes such a record in the case of the whale, an animal which had not previously been electrocardiographed; it was for that reason that we made our first attempt on a small whale, the white Beluga, in Alaskan waters. It is of this procedure that we are writing in the present paper. This experiment was made possible by a gran