Suppression of ventricular output by noise in the atrial channel in a dual chamber pacemaker.

In a pacemaker dependent, 60-year-old man with complete heart block, programming high (5.0 V and 1.0 ms) atrial output and 5.0 volt and 0.5 ms ventricular output while in the DDD mode of a pulse generator, resulted in loss of ventricular channel output with resulting asystole, while the simultaneous, pulse generator produced ECG interpretation channel falsely indicated continuing ventricular channel output. Ventricular pacing was promptly restored by programming to the emergency VVI mode. At later operation the atrial lead was determined to be defective, with a low impedance, while the ventricular lead was intact (lead impedance telemetry was not available). The manufacturer has acknowledged a pulse generator design anomaly that may occur in the setting of a low atrial impedance and issued a Health Safety Alert.