An electronically monitored angioplasty system (10) is provided with a verifier circuit (60, 72) to verify the operation of conversion circuitry (28, 28', 28'') for converting an electrical pressure signal from a pressure transducer (22) to a displayed numerical value on a digital read-out (32). 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 (16). 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 (140) sounds a pleasant signal that the balloon is fully deflated so the doctor need not divert attention from the patient.