Page 165 - Feline Cardiology

164 Section D: Cardiomyopathies

discharged with furosemide 12.5 mg PO q 12 h for a few ommended. Aldactazide is a combination of hydrochlo-
days, if mild dyspnea is still present at the time of dis- rothiazide and spironolactone, which is used in dogs
charge, and then the furosemide can be decreased to the with refractory heart failure, but it may not be as attrac-
minimal tolerated dose to achieve RR <40 and normal tive for use in cats given the possibility of an adverse
effort (6.25 mg PO q 12 h is a typical maintenance dose). reaction to spironolactone.
In cats with significant azotemia (BUN 70 mg/dl A low salt diet may be implemented, if palatable, in
(25 mmol/l) or higher, creatinine 3 mg/dl (264 mmol/l) cats receiving moderate furosemide doses and an ACE
or higher) and resolved heart failure, a lower starting dose inhibitor. Low salt cardiovascular diets contain 0.15–
of furosemide of 6.25 mg PO q 12–24 h may be more 0.2 g sodium/1000 kcal, and help limit sodium and water
appropriate. The owner should be taught how to count retention. The nutritional priority in cats is to maintain
Cardiomyopathies ratory effort at home and instructed to keep a daily atable low-salt diet to a cat that remains anorexic. Low-
an adequate caloric intake, rather than forcing an unpal-
the resting respiratory rate and qualitatively assess respi-
salt diets are available as prescription commercial diets
written log. This is highly beneficial for making decisions
(Purina CV or Hills H/D) or one can be formulated by
regarding dosage adjustment in individual patients.
a nutrition service. Owner-formulated home-cooked
Refractory congestive heart failure
erinary nutritionist (useful resources include balanceit.
Refractory heart failure is present when clinical signs of diets are discouraged unless they are balanced by a vet-
dyspnea continue occur due to persistent pulmonary com; Home-prepared Dog and Cat Diets, The Healthful
edema and/or pleural effusion despite increasing doses Alternative, DR Strombeck, 1999.) Low-salt diets also
or maximal dose of furosemide (3–4 mg/kg PO q 8–12 h) activate RAAS, so cats should also be given an ACE
in a compliant patient that is reliably receiving the medi- inhibitor. Renal diets are protein restricted, which may
cation. Cats commonly have progressive heart failure hasten development of cachexia in heart failure patients.
over time, requiring up-titration of the furosemide dose, They may be indicated in patients with concurrent mod-
yet refractory heart failure requiring 4 mg/kg PO q 8 h is erate to severe renal disease and heart failure.
unusual. In cats requiring maximal furosemide doses,
the issue of owner and patient compliance with medica- Prophylactic anticoagulant therapy
tion administration should be investigated, and com- Prophylactic anticoagulant therapy is indicated in cats
pounding the furosemide may be an option in cats that that have had a history of ATE or have echocardio-
resent the pill form. Mild to moderate prerenal azotemia graphic evidence of spontaneous contrast (i.e., red blood
and dehydration are expected in cats receiving high cell aggregation) or intracardiac thrombus. Some cardi-
doses of furosemide but are a necessary evil compared ologists, including the authors, use prophylactic antico-
to life-threatening dyspnea from progressive heart agulant therapy in cats with moderate or severe left atrial
failure. Some cats are intolerant to high furosemide dilation, who are likely at greater risk of developing ATE.
doses and develop symptoms referable to dehydration The incidence of ATE in cats with HCM is 16–18%
and azotemia. The furosemide dose may be decreased in (Rush et al. 2002; Atkins et al. 1992). Anticoagulant
these cases, and if there is a lack of improvement in choices include low-dose aspirin (5–81 mg PO q 3 days),
symptoms of dehydration, one or two subcutaneous clopidogrel (18.75 mg PO q 24 hr with food), low molec-
fluid administrations with low volumes (50–60 ml) may ular weight heparin (Lovenox 1.5 mg/kg SC BID-TID),
be given temporarily but not on an ongoing basis. In cats or warfarin. There are no controlled studies comparing
with concurrent symptoms from severe dehydration and effects of the most commonly used anticoagulants
azotemia as well as severe dyspnea from congestive heart (aspirin, clopidogrel, and enoxaparin) on development
failure, no effective therapy exists and euthanasia may of arterial thromboembolism in cats, although a large
be a feasible option. multicenter study in cats suffering from ATE that were
Cats with significant heart failure despite maximal treated with aspirin versus clopidogrel has been con-
furosemide doses may benefit from addition of hydro- ducted and results are pending. In cats with spontane-
chlorothiazide (1–2 mg/kg PO q 12–24 h) starting at the ous contrast seen by echocardiography, repeat
low end of the dose and increasing as necessary. echocardiographic assessment of spontaneous contrast
Spironolactone is not a very effective diuretic but may should be done after anticoagulant therapy is started,
provide adjunctive treatment to reduce hypokalemia and combination therapy may be needed for cats with
and reduce some of the deleterious effects of aldoste- persistent spontaneous contrast.
rone. In a study of 26 cats with asymptomatic HCM, 1/3
of cats treated with spironolactone developed severe Medications Not Indicated or Contraindicated
ulcerative facial dermatitis 2.5 months after treatment, Because taurine and carnitine deficiencies do not cause
so careful monitoring for adverse skin reactions is rec- or contribute to development of HCM, their supple-