Can normal pacemaker behavior near battery depletion cause alarming symptoms and clinical diagnostic difficultly?
To put the topic in context we need to describe normal PM functioning as the battery nears depletion.
My PM is a Consulta CRT-P model and according to the Medtronic manual, here is the sequence, which we can use as an example.
When the battery reading reaches equal to or less than 2.77 volts a replacement indicator named RRT or Recommended Replacement time is displayed on the interrogation. A "clock" is set to run for 3months and when it is timed out ,another replacement indicator named ERI or Elective Replacement Indicator is displayed. At this point the PM is switched to a VVI Mode at 65bpm. If a magnet is paced on the PM ,the rate will read 65 indicating that the unit is in the RRI mode.If battery life is adequate this power saving mode will continue for three months and then the unit reaches EOS or end of service.
VVI mode works in the following way.The ventricles are paced unless a spontaneous ventricular activation occurs first and then the lower limit for ventricular activation is reset.If a spontaneous ventricular activation does not occur first then the ventricle is paced.Atrial activity and ventricular activity are independent and competeting.
According to reference 1 and 2 (see below ) only Medtronic PMs exhibit this near end of service behavior.
A PM in the VVI mode is in an asynchronous mode meaning that there is loss of synchrony between the atrium and ventricle possibly resulting in a clinical scenario called pacemaker syndrome .Symptoms can include chest pain,shortness of breath, fatigue.palpitations and neck pulsation among others.
A 2020 case report (which seems to be very similar to a case referenced in 2010 (ref 2)) of a 70 year old man with an Adapta PM presented to ER with palpitations and dyspnea. Physicians were unable to do a PM interrogation ( another feature of the ERI mode in some . ( but not all) Medtronic models is that the interrogation feature is disabled ) . The clinical problem was solved and a replacement PM was implanted with resolution all symptoms .
It should be noted the the device was not malfunctioning. At manufacture it was programmed to shift into an asynchronous mode when it reached ERI condition. To the manufactures of the PM this was a feature not a bug.
The authors of both referenced articles were critical of ERI management in Medtronic PMs. Dr. John Mandrola (ref 2) stated in 2010 he has personally seen 4 cases in which this type of syndrome occurred in a patient with a PM whose unit shifted into a VVI mode with resultant pacemaker syndrome, a situation in which the diagnosis may not be apparent potentially leading to further further diagnostic tests with missed diagnosis even by cardiologists.Mandrola mentions two patients who were subjected to coronary angiograms before the diagnosis was finally made. Siroky made his criticism obvious in the title to the case report ,"bad device behavior or malfunction".
An obvious comment is -should not EP cardiologists and PM manufacturers inform patients of the untoward events that may as their battery approaches depletion. In my limited experience patient education before and after the PM implantation has much room for improvement .
1)Siroky,GP et al Shortness of breath and palpitation in an elderly man:Bad device behavior or malfunction .Journal of Arrhythmia,2010:36,1109 -1111
2) Madrola, J. https://www.drjohn.org/2010/09/answer-to-this-weeks-clinical-vignette/