Biomedical Engineering Reference
In-Depth Information
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Patient Follow-Up
Throughout the longevity of a device, both the technical
condition of the implanted system and clinical indicators
recorded in the device memory in the period between two
follow-ups must be monitored on a regular basis. It is an
established practice that the initial system check is carried
out immediately after implantation; the next follow-up
should precede a hospital discharge. Further follow-up
should be performed as required by the implantation center
either in a month and then in 6-month intervals, or in 3-6
months. Some manufacturers may recommend conducting
follow-ups at an interval of 3 months, in particular during the
period after implantation. As a rule, a patient is supposed to
have the system follow-up after a defibrillation shock occurs,
sound signals are emitted by the device, or in other unex-
pected circumstances.
During implantable system follow-ups, at a minimum an
external defibrillator and an electrocardiogram (ECG)
recorder or a monitor should be available. For the purpose of
optimizing medical personnel, commissioning by a medical
care provider or a medical device supplier of a qualified bio-
medical or clinical engineer to perform routine follow-ups
has proved to be convenient. These engineers are greatly
experienced in the control of programmers and applications,
which shortens the follow-ups and enhances safety. Provided
that an electrogram analysis is required, physician/techni-
cian consultation is recommended.
At the follow-up preceding hospital discharge (usually
within 72 h after implantation), the device should be inter-
rogated using a programmer, and a simplified follow-up
should be carried out using a summary screen, which is avail-
able in most applications. The patient must be checked for
lead dislodgement or other postoperative complications. All
leads must be tested for pacing thresholds and lead imped-
ance, and the intrinsic signal amplitude must be measured. In
addition, final setup of the system parameters must be per-
formed according to the actual state, and therapy counters
must be reset so that only data relating to the latest episodes
are displayed at the next follow-up. Then, a record is printed
from the programmer and included in the patient's file.
In addition to routine measurement of electrical parame-
ters (pacing thresholds, intrinsic signal amplitudes, and
impedances) in all leads and check battery status and stored
electrograms, at the first follow-up after discharge it is neces-
sary to verify the appropriateness of the parameters set dur-
ing the postimplantation phase for patient's daily life and the
condition of the implantation wound. To optimize the set-
tings, information concerning the patient's feelings during
the postimplantation period (quality of sleep, palpitation) is
important. With pacemakers, this primarily involves setting
the lower rate limit and parameters of atrioventricular (AV)
delay or the sensor. Pacing of the right ventricle (dysfunction
prevention) and the right atrium should be minimized to pre-
vent unnecessarily fast pacing. To support the intrinsic heart
rate, it is always helpful to set pace hysteresis and AV delay
hysteresis, if possible. An AV delay that is too short results in
excessive right ventricular pacing and insufficient ventricu-
lar filling phase time. In implanted cardioverter-defibrillators
(ICDs), the detection zone setting must be rechecked, prefer-
ably based on histograms of the intrinsic heart rate, so that
the zone lower limit is not close to the possible normal intrin-
sic rhythm. In addition, any electrograms stored in the device
memory must be evaluated.
At further follow-up, electrical parameters of all leads
must be measured, the battery status has to be checked, and
stored tachycardia electrograms should be evaluated. In
patients with a chronic condition, attention must be given to
sudden variations in system parameters, such as pacing or a
decrease or increase in the shock circuit impedance. Specific
diagnostic tools depend then on the respective device fea-
tures. For the sake of clarity, it is recommended that brady-
cardia counters and stored tachycardia episodes be reset at
every follow-up; the memory is divided into short-term
