A patient with dizziness, tachycardia and a DDDR pacemaker.

An 84-year-old female patient presented to the coronary care unit with dizziness. A DDD-R minute ventilation sensor pacemaker had been implanted eight years previously. The ECG showed an atrial and ventricular paced rhythm of 140 beats/min. After disconnecting the patient from the cardiac monitor the pacemaker rate dropped gradually to 90 beats/min. The cardiac rhythm monitoring system applies low-amplitude electrical pulses in order to measure respiration rate by transthoracic impedance (TTI) measurement. The minute ventilation pacemaker sensor is driven by the same TTI measurement for rate response. Inappropriate interference between these two systems caused a sensor-driven high pacemaker rate. The dizziness was not related to the sensor-driven high rate.