Mechanisms underlying overdrive suppression and overdrive excitation in guinea pig sino-atrial node

Evaluation of sino-atrial node function in man by overdrive suppression.

The relationship between overdrive suppression and overdrive excitation in ventricular pacemakers in dogs.

We studied the excitatory and inhibitory effects of overdrive on idioventricular pacemakers in anesthetized dogs with recently induced complete atrioventricular block. The following results were obtained: (1) a slow driving rate may induce a temporary rhythm which may be reinstituted with additional stimuli; (2) the induced rhythm may appear as coupled extrasystoles which, on interruption of th...

Overdrive Suppression

THE RELATIONSHIP among cardiac pacemakers is characterized by the fact that usually one pacemaker is dominant and all the others are subsidiary. The sinoatrial node acts as the dominant pacemaker and all other pacemaker tissues are discharged by a conducted impulse before their diastolic depolarization can attain threshold. These pacemakers are called subsidiary to emphasize the fact that under...

Role of adenosine on ventricular overdrive suppression in isolated guinea pig hearts and Purkinje fibers.

The present study was undertaken to demonstrate and characterize potentiation of ventricular overdrive suppression by adenosine. To substantiate that adenosine has an enhanced effect on overdrive suppression, it would be necessary to demonstrate that adenosine increases pause duration independent of slowing spontaneous pre-drive rate. In isolated perfused guinea pig hearts with surgically induc...

Distinguishing between overdrive excited and suppressed ventricular beats in guinea pig ventricular myocardium

Rapid ventricular pacing rates induces two types of beats following pacing cessation: recovery cycle length (RCL) prolongation (overdrive suppression) and RCL shortening (overdrive excitation). The goals of this study were to compare common experimental protocols for studying triggered activity in whole-heart preparations and differentiate between recovery beats using a new methodology. Post-pa...