Haemodynamic and clinical effects of paired stimulation of the heart.

In 1963, Lopez, Edelist, and Katz demonstrated that electrical stimulation could be used for slowing the heart below its spontaneous rate. These workers noted when pacing the heart of a dog that sudden slowing could consistently be produced when the impulse persisted for about 150 m.sec. They were able to show that this effect was due to stimulation at the "make" and the "break" of the impulse, and that it could also be produced by two short electrical impulses separated by about 150 m.sec. This method has been extensively investigated at several centres in the United States (Chardack, Gage, and Dean, 1964; Braunwald et al., 1964; Ross et al., 1965). In this communication we present the results of htmodynamic studies in dogs using the technique of paired stimulation of the heart and describe our early experience in the clinical application of the method in four patients.