Page 80 - Feline Cardiology

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Electrocardiography

Key Points

• Electrocardiography is most useful in cats for the following indications, in decreasing order of diagnostic yield: cardiac
arrhythmias, metabolic abnormalities, and structural heart disease.
• The position of the limbs can affect the ECG results substantially in cats.
• Recording multiple leads helps the clinician choose the clearest tracing and makes ECG interpretation easier and more
accurate.
• Normal values for the feline ECG are listed on the inside covers of this book.

INTRODUCTION numerous potential artifacts, make many interpreta-
tions challenging, and a poor quality tracing may not be
The first feline electrocardiogram (ECG) was performed interpretable by even the most skilled cardiologist. Using
on a kitten by Augustus Waller in 1887 (Waller 1887, multiple ECG leads provides additional information
1888, 1889). Today, the main clinical indication for elec- that may be missed on a single-lead strip, and by con-
trocardiography in cats is to assess the rhythm of the vention a complete ECG in the cat displays 10 leads (see
heartbeat, commonly when an irregular or otherwise Figure 9.1). Recording multiple leads provides addi-
abnormal rhythm (arrhythmia) is detected during phys- tional information where lead II, or any other single
ical exam, a patient is being monitored in the intensive lead, may be inadequate (see Figure 9.2).
care unit, or during general anesthesia. Additional appli- A cat’s ECG may be obtained with the patient in any
cations include assessment of cardiac dimensions, for position, but the standard technique requires the cat to
which an ECG is a poor substitute for an echocardio- be in right lateral recumbency. Left lateral and sternal
gram, and monitoring of such extracardiac disturbances recumbencies have been evaluated in feline ECGs
as hyperkalemia and hypoxemia (Tilley 1992; Côté 2010; (Harvey et al. 2005; Gompf and Tilley 1979; Calvert and
Côté and Harpster 2009; Fox and Harpster 1999). The Coulter 1981), with conflicting results. Some studies
abbreviations ECG and EKG are used interchangeably; identified little difference between recumbencies
EKG was the original Dutch spelling (elektrokardio- (Gompf and Tilley 1979; Calvert and Coulter 1981),
gramm) put forth by the father of electrocardiography, whereas a more recent study demonstrated significantly
Willem Einthoven, and this has been replaced only par- smaller R waves when the ECG is recorded with cats in
tially by ECG in English.
left lateral or sternal recumbency compared to right
lateral recumbency and a mean electrical axis that is
significantly different in left versus right lateral recum-
TECHNIQUE
bency (Harvey et al. 2005). At least part of the explana-
A great deal of the interpretation of a feline ECG depends tion for this discrepancy likely relates to the position of
on ECG quality. The small amplitude of deflections, and the electrodes on the limbs. As demonstrated in an

Feline Cardiology, First Edition. Etienne Côté, Kristin A. MacDonald, Kathryn M. Meurs, Meg M. Sleeper.
© 2011 John Wiley & Sons, Inc. Published 2011 by John Wiley & Sons, Inc.

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