Monitoring equipment induced tachycardia in patients with minute ventilation rate-responsive pacemakers

Minute ventilation-sensing pacemakers enable the paced heart to respond toan increased workload. Two patients with such a pacemaker developedpacemaker-driven tachycardia when connected to an electrocardiogram (ECG)monitor also capable of documenting ventilatory frequency and ECG leaddisconnection. This tachycardia stopped when the ECG leads were removed.These pacemakers and monitors emit a low-amplitude electrical current andmeasure the resultant impedence signal across the chest. When patients areconnected to the monitor the pacemaker sensor summates both impedencesignals and the paced heart rate is increased as a result.