Experimental and Clinical Use of a Variable Parameter Cardiac Pacer

Modifications in the structure and function of a variable parameter cardiac pacer are described in which: 1.A switch is added in the output circuit, providing a tenfold increase in sensitivity in experimental and clinical measurement of ventricular stimulating thresholds.2.A transparent panel overlay is used during clinical pacing to neutralize experimental controls.3.An indirect overdrive system is described in which the rate of a synchronous or standby pacer can be temporarily increased for either diagnostic or therapeutic purposes.