Page 135 - Problem-Based Feline Medicine

9 – THE CAT WITH ABNORMAL HEART SOUNDS AND/OR AN ENLARGED HEART 127

● Restrictive and unclassified cardiomyopathies** (p 135)
A systolic heart murmur, gallop rhythm and/or arrhythmia may be heard. Abnormal heart sounds
are not always heard on auscultation. The heart is usually enlarged.
● Dilated cardiomyopathy (p 151)
A systolic murmur, gallop rhythm and/or arrhythmia may be heard. The heart shows generalized
enlargement. Dilated cardiomyopathy can occur in cats eating taurine-deficient diets.
● Chylous effusion* (p 139)
Displaced or muffled heart sounds may be heard. Etiologies are trauma, infection, cardiomyopathy,
neoplasia and idiopathic. In most cases, the cause is idiopathic.
TRAUMATIC
● Diaphragmatic hernia (p 154)
Displaced and/or muffled heart sounds may be heard. Dyspnea may or may not occur.

(neoplasia) and/or effusions (cardiomyopathy, neoplasia
INTRODUCTION
or infection) or rarely structural changes (hernias or pec-
tus excavatum).
MECHANISM?
Cardiac enlargement most commonly results from
Abnormal heart sounds are defined as follows: cardiomyopathy secondary to hypertrophy.

Systolic murmurs are common and are caused by tur-
bulent blood flow secondary to a valvular stenosis or WHERE?
insufficiency. Systolic murmurs are the most common
Abnormal heart sounds and/or cardiac enlargement
and account for >95% of murmurs.
result from problems in any of the following sites:
Diastolic and continuous murmurs are rare.
Heart, mediastinum, diaphragm, thoracic skeleton, lungs.
Continuous murmurs occur during diastole and sys-
tole and most commonly occur from a patent ductus
WHAT?
arteriosus.
The most common cause of cardiac disease is hyper-
In thin cats, murmurs may be caused by mechanical
trophic cardiomyopathy. It is usually acquired and
compression of the chest during auscultation.
idiopathic.
Gallop rhythms are extra heart sounds due to abnor-
Congenital heart disease is rare and a murmur is usu-
malities in relaxation. The gallop rhythm is classified as
ally heard at a young age.
either S or S but it is difficult to distinguish between
4 3
these in cats. The most common congenital defect in cats is ventral
septal defect followed by mitral valve dysplasia.
Arrhythmias are disturbances in rate and rhythm and
are noted by an irregular rhythm. Most cats with heart murmurs are asymptomatic.
Tachycardia is defined as a heart rate greater than 220 Abnormal heart sounds in asymptomatic cats
bpm. always warrants a cardiovascular work-up.
Loud heart sounds are usually normal in thin cats and Cats with abnormal heart sounds may or may not
during tachycardia. have cardiac enlargement.

Displaced heart sounds and muffled heart sounds are Lack of cardiac enlargement on radiographs in cats with
most commonly caused by masses within the thorax abnormal heart sounds does not exclude heart disease.