Page 193 - Small Animal Internal Medicine, 6th Edition

CHAPTER 8 Myocardial Diseases of the Cat 165

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A

B C

FIG 8.6
(A) Color flow Doppler image taken in systole from a male domestic longhair cat with
hypertrophic obstructive cardiomyopathy. Note the turbulent flow just above where the
thickened interventricular septum protrudes into the LV outflow tract and a small mitral
insufficiency jet, typical with systolic anterior motion (SAM) of the anterior mitral leaflet.
(B) and (C) show two-dimensional and corresponding color Doppler images from a male
domestic shorthair cat with hypertrophic obstructive cardiomyopathy. There is hypertrophy
of the basilar interventricular septum and severe left atrial enlargement. The anterior mitral
leaflet’s SAM (arrow, B) contributes to dynamic LV outflow obstruction. (C) Color Doppler
imaging in midsystole reveals turbulent, high-velocity flow in the LV outflow tract and, in
this cat, severe mitral regurgitation. Right parasternal long-axis view. Ao, Aorta; LA, left
atrium; LV, left ventricle.

Cats with severe pulmonary edema are given supplemen- The use of pimobendan in cats with CHF is the subject of
tal oxygen and parenteral furosemide, usually intramuscular ongoing study. In theory, positive inotropes such as pimo-
(IM) initially (2 mg/kg q1-4h; see Box 3.1, p. 62 and p. 65), bendan are not indicated in cats with HCM, because systolic
until an intravenous (IV) catheter can be placed without function generally is well preserved and increased force of
excessive stress to the cat. Butorphanol can be helpful to contraction could worsen dynamic outflow tract obstruc-
reduce anxiety that accompanies dyspnea and hospitaliza- tion. However, pimobendan could improve cardiac output
tion (see Box 3.1). Nitroglycerin ointment can be used without increasing myocardial oxygen demand, and its bal-
(q4-6h), although no studies of its efficacy in this situation anced vasodilatory properties might be beneficial in both
have been done. Once initial medications have been given, acute and chronic CHF regardless of underlying structural
the cat should be allowed to rest. The respiratory rate is noted disease. Nevertheless, great caution is advised when HOCM
initially and then every 15 to 30 minutes or so without dis- is suspected or confirmed, because vasodilation, especially
turbing the cat. Respiratory rate and effort are used to guide combined with increased contractility, could worsen the
ongoing diuretic therapy. Catheter placement, blood sam- dynamic LV outflow obstruction and promote hypotension.
pling, radiographs, and other tests and therapies should be If pimobendan is used in a cat with HOCM, blood pressure
delayed until the cat’s condition is more stable. Airway suc- measurement and close monitoring for signs of hypotension
tioning and mechanical ventilation with positive end- are advised. Pimobendan is clearly indicated in cats with sys-
expiratory pressure can be considered in extreme cases. tolic dysfunction or cardiogenic shock, and several studies