An electronically monitored angioplasty system is provided with a verifier circuit to verify the operation of conversion circuitry for converting an electrical pressure signal from a pressure transducer to a displayed numerical value on a digital read-out. The verifier circuit is selectively activated to offset the displayed numerical value by a predetermined amount and upon deactivation the displayed numerical value returns to the pressure sensed by the pressure transducer in the balloon. In one embodiment, a reference signal to the conversion circuitry is selectively offset by a signal corresponding to the predetermined amount and in another embodiment the electrical pressure signal itself is selectively offset by a reference signal corresponding to the predetermined amount. In another aspect of the system, an audible balloon deflation indicator circuit sounds a pleasant signal that the pressure within the balloon has fallen below a threshold pressure so the doctor need not divert attention from the patient.