Page 15 - Feline Cardiology

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Heart Murmurs and Gallop Heart Sounds

Key Points

• Cardiac murmurs can be present due to primary heart disease (for example, hypertrophic obstructive cardiomyopathy with
systolic anterior motion of the mitral valve), high-output heart disease (for example, anemia), or they can be innocent. It is
usually impossible to differentiate between these possible underlying etiologies on physical examination alone. However,
higher-intensity murmurs, such as those that produce a precordial thrill, are more likely to be associated with underlying
structural heart disease.
• Although early heart disease can be present in cats without cardiac enlargement on thoracic radiographs, over time the left
(most commonly) atrium typically enlarges due to elevated ventricular filling pressures associated with cardiomyopathy.
Usually left atrial enlargement is present prior to the development of congestive heart failure. Therefore, thoracic radiographs
are a reasonable screening tool when a murmur or gallop sound is detected on physical examination.
• Because early disease can be missed radiographically, echocardiography is the most appropriate screening tool for breeding
stock of high-risk breeds (such as Maine coon cats), and in clinical situations where definitive ruling in or ruling out of heart
disease is desirable (e.g., preanesthetic evaluation, owner’s desire to know, etc.) because cardiomyopathy may be clinically
silent.
• Echocardiography is the best diagnostic modality to define underlying cardiac disease and identify the cause of the murmur. It
is the only diagnostic tool that allows the clinician to definitively identify the cause of a cardiac murmur that has been noted
on physical examination.
• A gallop sound is said to be present when S 3 or S 4 (the diastolic filling sounds) are auscultable. A summation gallop can be
ausculted in normal cats when the heart rate is fast enough to allow superimposition of early and late ventricular filling (S 3
and S 4 ). However, auscultable gallop sounds most often indicate cardiac disease in cats.

INTRODUCTION 1.1). The most important part of becoming adept with
a stethoscope is experience; however, its proper use is
A thorough clinical examination is of critical impor- essential (Box 1.1).
tance for complete investigation of the heart no matter
how many advanced diagnostic tests are available. It can Approach to Auscultation
provide valuable information about cardiac functional Prior to auscultation, the chest should be palpated for
status, circulatory physiology, and the likely etiology of the apex beat (the palpable heart beat on the chest
heart disease. History taking and a complete physical surface). The examiner’s palpation identifies the loca-
examination are always the essential first steps that tion of the strongest apex beat—which is a useful place
should guide the choice of diagnostic tests. It is optimal to begin auscultatation—and, without compressing the
to measure the respiratory rate in the cage or carrier chest, characterizes its strength and position. With expe-
before the patient is stressed by removal for physical rience, the astute clinician will come to appreciate the
examination (Bond 2005). The auscultatory examina- difference between an increased apex beat caused by
tion of the heart and lungs should include the identifica- excitement (which will decrease as the patient calms)
tion of auscultable normal heart sounds (S 1 and S 2 ) and and an increased apex beat due to cardiac enlargement
the identification of any abnormal heart sounds (Figure (which will be present in a calm patient).

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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