Page 21 - Feline Cardiology

Chapter 1: Heart Murmurs and Gallop Heart Sounds 11

In small animals, gallop sounds (S 3 and S 4 ) are gener- gallops being more prominent during light application
ally reflective of abnormal diastolic function. As blood of the bell of the stethoscope to the chest surface (low-
from the atria fills the ventricles during diastole, rapid frequency sounds). Systolic clicks are most often associ-
deceleration of the blood column in a stiff, noncompli- ated with abnormalities of the atrioventricular valves,
ant ventricle (such as occurs with hypertrophic or such as mitral valve prolapse. In general, systolic clicks,
restrictive cardiomyopathy) results in auscultable vibra- and specifically, mitral valve prolapse, are rare in the Clinical Entities
tions. S 3 sounds are generated by rapid ventricular feline population, although anecdotally such clicks may
filling during early diastole (see Figure 1.1). When be noted in cats with hypertrophic cardiomyopathy.
present in a cat, they imply ventricular dilation and/or Split heart sounds can also produce a triple cadence
systolic dysfunction. Other possible causes include as already described and thus constitute another differ-
hyperthyroidism and anemia. The S 4 sound is associated ential diagnosis for gallop sounds. Asynchronous closure
with active ventricular filling caused by atrial contrac- of the atrioventricular valves (S 1 ) or the semilunar valves
tion and occurs late in diastole (see Figure 1.1). S 4 (S 2 ) can result in split heart sounds. Split first heart
sounds are most commonly ausculted in cats with sounds and split second heart sounds are very rare in
hypertrophic cardiomyopathy. However, it is often dif- cats. In humans and dogs, split second heart sounds can
ficult to differentiate between S 3 or S 4 when the heart occur with pulmonary hypertension and delay of pul-
rate is fast, and when they merge, the result can be a monic valve closure, but this finding has not been rec-
single auscultable extra sound, called a summation ognized in cats with pulmonary hypertension (see
gallop. Summation gallop sounds occasionally can occur Chapter 25, “Pulmonary Thromboembolism and
in some normal cats when their heart rates are fast Pulmonary Hypertension”).
enough that S 3 and S 4 become audible and are super-
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