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An Urban Experience
I. Ljungvall1 1 Sweden
Ingrid Ljungvall
Associate Professor, DVM, PhD
Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science,
Swedish University of Agricultural Sciences, Uppsala, Sweden
Heart murmurs in cats can be associated with structural heart disease (pathological heart murmus), but a high percentage of cats with murmurs appear to have no evidence of structural heart disease (non-pathological heart murmurs). A systematic evaluation of murmur characteristics is indicated when a heart murmur is detected in a cat.
Auscultation technique
An exact cardiac diagnosis can seldom be established based solely on cardiac auscultation, but an optimal auscultation technique can substantially narrow down the list of differential diagnoses. Auscultation should
be performed in a quiet environment, and the patient should preferably be standing on all four limbs during cardiac auscultation as abnormal sounds, which easily can be mistaken for heart murmurs, can arise in a recumbent animal due to rubbing of the heart against the chest wall. Furthermore, localization of area of origin of different cardiac sounds is more easily achieved in
a standing animal. Breathing sounds can be mistaken
for sounds originating from the heart, and differentiating heart sounds from breath sounds can be facilitated by watching the cat’s breathing pattern while simultaneously auscultating the heart.
Murmurs are auditory vibrations caused by high-velocity and turbulent blood flow through the heart and vessels. A systematic evaluation of murmur characteristics is indicated when a heart murmur is detected in a cat. The murmur’s auscultatory features can be characterized
by timing within the cardiac cycle, anatomic location, radiation area, intensity (loudness), frequency (pitch), and shape of vibration pattern (which is most easily achieved
by recording murmurs by phonocardiography). Point
of maximum intensity (PMI) of a murmur is the location over the thorax where the murmur is loudest, and can serve as a guide to the origin of the murmur. The PMI is commonly associated with a particular valve region (i.e., pulmonic, aortic, mitral, tricuspid). However, the small size of the feline heart makes it difficult to distinguish the different valve areas on the thorax. Accordingly, localization of murmurs in cats is often described as sternal versus parasternal, base versus apex, and left versus right. The area of the ventral thorax/sternum should always be auscultated in cats, as murmurs often are heard best at this location. Lateralization can narrow the differential diagnosis list in some patients.
Most cardiovascular diseases in cats result in systolic murmurs, which most commonly start immediately after the first heart sound, S1, but they can also start later
in systole. Systolic murmurs can last for only a portion
of the systole (early, mid or late systolic murmurs), throughout systole from the end of S1 to the beginning or the second heart sound, S2, (holosystolic murmur), or extremely rarely; throughout systole from the beginning of S1 to the end of S2 (pansystolic murmur). Diastolic turbulent blood flow is rare in cats and can be relatively difficult to detect. Continuous murmurs last throughout systole and diastole.
For some cardiac diseases, grading of the murmur intensity serves as a rough estimate disease severity, whereas a lack of agreement exists between severity of cardiac disease and murmur grade for other diseases. The intensity of murmurs is most commonly graded on
a 1 to 6 scale, where a grade 1 murmur is regarded as the softest and a grade 6 the loudest. A precordial thrill is palpated in animals with a grade 5 or grade 6 murmur.
Etiologies of murmurs
Murmurs in cats frequently develop in conjunction
with structural heart disease (pathological murmurs). However, presence of a heart murmur does not always signal presence of structural cardiac disease as murmurs can also arise due to various physiologic processes (non- pathological murmurs).
The most common underlying structural heart disease causing a heart murmur in adult cats is hypertrophic cardiomyopathy (HCM). Also young cats may have structural heart diseases commonly recognized in
adult cats (such as HCM). The PMI of the murmur in HCM cats is usually heard over or just to the left of the sternum. Dynamic subvalvular aortic stenosis and mitral regurgitation associated with systolic anterior motion of the mitral valve are the most common sources of systolic murmurs heard in cats with HCM. However, dynamic subvalvular aortic stenosis can also be observed in

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