Electrocardiographic changes in induced hypothermia in man.

Numerous papers have been published in the past few years describing the changes in the electro-cardiogram of animals submitted to hypothermia (Prec et al. and the pattern is now fairly well established. Information regarding changes in the human cardiogram, however, is scanty and has been derived from various sources. Electrocardiograms of patients suffering from severe exposure to cold have been reported from time to time by Tomaszewski (1938), who was the first to report the " injury potential " at the described the cardiograms of nine patients submitted to hypothermia for advanced malignant disease and was the first to describe the progression of the abnormalities with fall in temperature and to comment on the high incidence of atrial fibrillation The results of the horrible experiments at Dachau, in which prisoners were submitted to hypothermia, have been described in detail by Alexander (1949). Finally, two series of cardiograms of patients operated on under hypothermia have been published by Capretti et al. (1953) and Hicks et al. (1956). In view of the relatively small number of cases reported so far, less than 50 having been found, we wish to present a series of 29 records of patients submitted to hypothermia for cardiac surgery and to compare them with other published records and with the changes observed in animals. During the early experimental work on dogs under hypothermia at Guy's Hospital, described by Ross (1954), electrocardiograms were frequently recorded. The changes seen in these records are essentially similar to those described by other workers and will be briefly summarized. It is proposed to refer to experimental work on animals further during the discussion of the human cases, but it should be emphasized at the outset that the changes in the cardiogram during hypo-thermia in man are not identical with those in animals and conclusions drawn from work on the latter cannot be applied to man uncritically. In animals, the ventricular rate falls progressively with fall in temperature, and impairment of conduction is manifested early by prolongation of the P-R and QRS intervals; the S-T interval also becomes prolonged (Fig. 1). Nodal rhythm or atrial standstill may occur. At lower temperatures (below 280 C.) ectopic beats and heart block become more frequent and ventricular fibrillation occurs in a proportion of animals, although some workers have succeeded in cooling dogs until asystole occurred at 10°-12° C. (Tysinger et al., 1955). A deformity of the QRS-ST …