Atrial Threshold Challenge during a routine pacemaker follow up
Senior Cardiac Physiologist, Barnet Hospital, Royal Free NHS Trust
Disclosure: The author has no conflict of interests to declare.
A 69-year-old gentleman with a history of type 2 diabetes, hypercholesterolemia and hypertension, under investigation by the TIA team was admitted to hospital due to symptoms of dizziness and light-headedness. He was found to be in complete heart block and underwent implantation of a dual chamber pacemaker system, consisting of an Abbott Assurity PM2272 pulse generator and two active fixation Abbott 2088TC tendril leads. Medications at the time included, Atorvastatin, Clopidogrel, Metformin.
He attended the pacing clinic for his routine 6-week post implant check. His presenting rhythm showed an atrial sense ventricular paced (AS/VP) rhythm at a rate of approximately 100 bpm. Counters showed that he was 1% AP and 99% VP. There was no underlying rhythm at 40 bpm. The device settings are displayed below.
Mode: DDD Base rate: 60 bpm
Upper tracking and sensor rate: 130 bpm
Paced AVD: 200ms Sensed AVD: 150ms
During the check, an atrial threshold test was attempted at a rate of 100 BPM in DDD mode. The EGM recorded during the test is displayed in figure 1.
Figure 1: Electrogram recorded during an atrial threshold test in DDD mode at 100BPM. Channels top to bottom, 1. ECG channel aVR, 2. Ventricular sense amplitude EGM, 3. Atrial sense amplitude EGM, 4. Marker channel.