Dual mode sensing by a variable cycle ventricular synchronous pulse generator.

When the Intermedics Cyberlith pulse generator is operating in its R-wave synchronous (VVT) mode, sensed events may trigger stimulus pulses or inhibit the output circuit. This dual mode response to sensed signals is the result of a variable timing cycle which includes an inhibit alert period (IAP) as well as a synchronous alert period (SAP). Sensed events occurring during the IAP result in inhibition of stimulus pulse output and resetting of the timing circuit. Consequently, during a continuous ECG rhythm strip one may observe synchronous and inhibited sensing responses and slowing of the pacing rate below the programmed rate of the pulse generator.