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Echocardiography

Key Points

• Echocardiography has largely supplanted invasive cardiology techniques such as cardiac catheterization; however, its accuracy
is dependent on a complete study and the interpreter’s having a good understanding of basic cardiovascular anatomy and
physiology.
• Thoracic radiographs are complementary to echocardiography; echocardiography does not give direct information regarding
the respiratory system such as the presence of congestive heart failure.
• An echocardiogram should never be performed prior to a thorough history and physical examination. The echocardiogram
should be used to rule in or out differential diagnoses that were based on the initial history and physical examination findings.

INTRODUCTION Thus, interpretation of feline physical examination
results, even with the benefit of an echocardiogram, can
Echocardiography has become the most important diag- be complicated. Echocardiographic results are one piece
nostic tool for feline heart disease, allowing the clinician in the puzzle.
to assess cardiac size, structure, function, and blood flow
within the heart. Echocardiography has largely replaced ECHOCARDIOGRAPHY BASICS
invasive diagnostic techniques such as cardiac catheter-
ization for most patients; however, it does not replace An echocardiogram is simply an ultrasound examina-
survey thoracic radiographs for assessment of the lungs tion of the heart. Ultrasound waves emitted from the
and pleura and for widespread availability. Moreover, echocardiograph (echo machine) are reflected by the
accurate interpretation of echocardiographic informa- interfaces of tissue and blood within the patient’s thorax,
tion requires the background provided by signalment and the echocardiograph computer processes the data to
and a good physical examination. For example, altered produce a two-dimensional (2D) cross-sectional image.
hydration status in normal cats can produce changes in M-mode echocardiography is obtained according to
the echocardiographic measurements of the left ventri- the same principles, but with only a narrow beam of
cle (LV) and left atrium (LA) (Campbell et al. 2007). ultrasound that displays the reflected signals on a
Pseudohypertrophy has been noted with hypovolemia, distance-time graph. Because the frame rate in M-mode
whereas intravenous fluid administration can result in is higher than the frame rate achieved using 2D echo-
increased LV and LA diastolic dimensions (Campbell cardiography, resolution is better and M-mode echocar-
et al. 2007). Some cats with cardiomyopathy are clini- diography is therefore used for most time-dependent
cally normal and, conversely, a large percentage (25– cardiac measurements.
69%) of cats with heart murmurs on physical examination Doppler echocardiography uses the Doppler principle
have echocardiographic studies that are within normal to determine the direction and velocity of blood flow.
limits (Bonagura 2000; Paige 2009; Wagner et al. 2010). The Doppler principle states that the frequency of a

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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