Page 54 - Rapid Review of ECG Interpretation in Small Animal Practice, 2nd Edition

Holter Monitoring

to application of sticky electrodes. Sometimes the
patch glue is reinforced with a few dabs of tissue
VetBooks.ir glue to ensure electrodes remain in place for the
duration of the recording. The required number of
electrodes (varies from 3 to 7 between systems) are
then attached. On very active dogs, a small 2*2-
inch strip of elastic tape can also be applied over
the electrodes on each side of the chest (Fig. 5.5) to
keep electrodes and patches securely on the chest,
before covering up the entire system and wires with
a wearable vest or dog “shirt” (Fig. 5.6). Elasticated
materials are generally more comfortable for the
patients than adhesive bandage material.
Due to their small size, it is challenging to fit
cats with Holter monitors and have them pursue
their normal activity in the home environment, Fig. 5.6 Dog shirts (“Surgi-Sox” [DogLeggs, LLC]),
as recommended in dogs. This likely results in modified by adding a small pouch to house the monitors,
under-diagnosis and under-treatment of feline are very well tolerated by dogs as a Holter vest.
arrhythmias. Newer Holter systems are smaller and
lighter, yet most cats are highly uncooperative when ANALYSIS OF HOLTER RECORDINGS
it comes to wearing any confining jacket required A variety of companies are available to perform
to carry even small monitors on their body. Even Holter interpretation using proprietary commercial
if tolerated, cats might restrict their activity, which software to perform automated ECG analyses,
likely diminishes the clinical value of the recording. aided by a manual review to ensure that artefacts
As an alternative, Holter monitors can be placed on are excluded and QRS complexes are accurately
cats during a hospital overnight stay during which identified and correctly designated as being either
time the monitor might be placed alongside them in narrow or wide QRS complexes to categorize as
the cage; however, this also fails to record the ECG supraventricular or ventricular.
during normal activity in the home environment. Typical Holter reports include the following
For these reasons, Holter monitoring in cats is information (Fig. 5.7):
challenging and rarely performed.
• A total beat count (number of QRS complexes
over entire recording): The total beat count per
minute (mean heart rate during each minute of the
recording) may be graphically displayed against
time to provide a rate histogram (Fig. 5.8). This
allows for interpretation of heart rate trends over
the recording period that can be associated with
dog activity (i.e., travel to and from the vet office,
exercise, sleep vs. wake periods, etc.).
• Mean heart rate (average heart rate over the
entire 24–48-hour period): In dogs, the 24-hour
mean heart rate is typically in the range of
65–85 bpm. Maximum heart rate and minimum
heart rate are usually provided based on short
periods, ranging from an 8-second to a 1-minute
average. Table 5.1 provides normal heart rates
Fig. 5.5 Patch electrodes for a 24-hour Holter derived from Holter recordings in dogs. The
recording are placed on the dog’s left hemithorax, mean difference in heart rate between dogs
after the hair has been clipped and the skin cleaned weighing 5 and 55 kg is only 10.5 bpm and
with alcohol. The electrodes are additionally taped to unlikely to be clinically significant.
the dog’s chest with a small strip of elasticon, before • Abnormal beat counts summarizing ventricular
covering the system up with a vest or Surgi-Sox. arrhythmias and supraventricular arrhythmias:
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