The cause of death from a small pulmonary embolism is not clearly understood. There is reason to believe that deleterious cardiac reflexes may occur, but their appearance has not been verified experimentally.1-3 However, the investigators cited have used heart-lung preparations or anesthetized animals in which reflexes would probably be abolished, and their results, therefore, are of questionable value. It is obvious that a method must be used whereby these studies can be performed on unanesthetized animals.
This laboratory has previously studied pulmonary vasoconstriction associated with pulmonary embolism in unanesthetized rabbits, and we feel that a correlation of such studies with the electrocardiographic pattern may throw some light on the problem. We should also like to report on some preliminary hemodynamic studies concerning a possible terminal mechanism of death in pulmonary embolism.
Our method of study has been the injection of a standard dose (1 cc/lb. of a