The results of clinical trials of a dual-sensor diagnostic pacemaker are described. The system monitors and records intraventricular electrical and pressure waveforms using a special lead incorporating bipolar electrodes together with a piezoelectric pressure transducer. The recorded waveforms, which are shown in conjunction with Holter recordings made simultaneously, demonstrate the value of pressure measurements and illustrate several cardiac events, including an ECG pause, bradycardia, a pressure pause, ectopic beats and tachycardia. The pacing function of the device is shown and capture is demonstrated.