Preparing for an examination – PACEMAKER CHECK

A follow-up examination should be performed 2-4 weeks after implantation, i.e. after the patient has been discharged from hospital, to detect any complications or procedural failures. It includes taking a medical history, a physical examination (including the implantation site), and an assessment of whether the pacing system is functioning correctly (ECG).

EARLY FOLLOW-UP EXAMINATIONS
The next follow-up examination should take place 2-3 months after pacemaker implantation. This is the period during which both the pacing threshold and the sensing of spontaneous cardiac electrical signals stabilise. In addition to a physical examination and an ECG, the pacing and sensing thresholds should be measured, and the values obtained should be used to programme the pulse energy (amplitude and width) and the sensitivity of the atrial and/or ventricular channel.

Programming the pulse energy conservatively (usually 200-300% of the pacing threshold) can extend the pacemaker’s battery life, sometimes by several years beyond the average operating life predicted by the manufacturer. Appropriate sensitivity programming (within 1/2–2/3 of the absolute sensing threshold
values) prevents undersensing (failure to sense) and the associated sensing disturbances on the one hand, while counteracting all effects caused by oversensing on the other. In ventricular systems (VVI), T-wave oversensing involves incorrectly interpreting the T wave as a QRS complex, while in atrial or dual-chamber systems, far-field
sensing means incorrectly interpreting the R wave as another P wave. In ventricular or atrial unipolar systems, muscle potentials can temporarily inhibit pacing; in dual-chamber systems, myopotentials detected in the atrial channel cause ventricular pacing at the upper tracking rate (UTR).

LONG-TERM FOLLOW-UP EXAMINATIONS
Patients with an AAI(R) pacemaker implanted for sinus node dysfunction or chronotropic incompetence may have checks every 6 months;
patients with bradycardia–tachycardia syndrome require much more frequent checks.
Patients with a dual-chamber pacemaker (DDD//DDDR) implanted for acquired or congenital atrioventricular (AV) block may have checks every 6 months. However, the same type of pacemaker implanted for bradycardia–tachycardia syndrome, or for other less typical indications (such as vasovagal syndrome, long QT syndrome or carotid sinus hypersensitivity syndrome), requires frequent follow-up examinations.
Particularly frequent checks (every 2-3 months, sometimes even every month) are required for patients with a dual-chamber pacemaker implanted for bradycardia–tachycardia syndrome, because they experience supraventricular arrhythmias that present certain diagnostic (ECG interpretation) and therapeutic difficulties.
More frequent follow-up examinations are required when taking
antiarrhythmic medicines (class Ia, Ic), which modify the pacing and sensing thresholds and AV conduction, and when it is necessary to assess the effectiveness of the relevant antiarrhythmic programmes in DDD pacemakers.

During the final year of the pacemaker battery’s expected life (which also depends on any previous reduction in pacing pulse energy), follow-up examinations should be more frequent, on average every 2-3 months.

We can assess the condition of the pacemaker battery either directly, using a telemetry reading from the programmer, or indirectly, by analysing the pulse rate on an ECG recording or using an oscillosynchroscope. In the early stages of pacemaker battery depletion, the elective replacement indicator is activated, initially as a reduction in the test
(magnet) rate, followed by a reduction in the pacemaker’s basic pulse rate.
A sign of substantial battery depletion is an automatic change in pacing mode from dual-chamber to single-chamber (e.g. from DDD to VDD or VVI), or from demand pacing to a fixed-rate mode (e.g. from VVI to VOO). In most pacemakers, 6-12 months elapse between activation and display of the ERI indicator and complete battery depletion (end of life, EOL; end of service, EOS). In people who are completely dependent on their pacemaker
(patients with third-degree AV block, IIIo, without an intrinsic escape rhythm), elective replacement should be carried out as soon as the signs of battery depletion described above appear (elective replacement time, ERT). In other patients with a satisfactory escape rhythm, follow-up examinations should be performed more frequently between ERT and EOL (EOS), e.g. every month, and replacement should take place before the battery is depleted. Another sign that may prompt an earlier decision on possible
pacemaker replacement is an unexpected change in its battery impedance.