Page 288 - Feline Cardiology

Chapter 19: Congestive Heart Failure 295

mide (0.1–0.3 mg/kg PO q 12 h) to an existing drug complications that may occur in chronic heart failure
regimen of high dose furosemide (3–4 mg/kg PO q 8–12 h) include cardiac cachexia, arterial thromboembolism,
and an ACE inhibitor when pulmonary edema or cardio- or tachyarrhythmias.
genic pleural effusion continue to rapidly recur and cause • The mainstays of therapeutic monitoring of cats with
dyspnea (i.e., refractory heart failure patients). Typically, heart failure include serum chemistry profile, thoracic
a dosage of 0.1–0.3 mg/kg PO q 12 h is used, with the radiographs, and systemic blood pressure.
lower dosage selected first when the patient is already • Echocardiograms may be helpful to identify myocar-
receiving furosemide, and some cardiologists recom- dial failure, spontaneous contrast or intracardiac
mend reducing the furosemide dose by 30–50%. Long- thrombus, and assess the severity of atrial dilation
term efficacy and safety are unknown in the cat. during chronic therapy.
Ototoxicity occurs in 50% of cats treated with 20 mg/kg
torsemide, similar to the ototoxic furosemide dose The most common complications that occur with heart
(18 mg/kg) (Klinke and Mertens 1988). Adverse effects failure treatment are dehydration and azotemia.
such as ulcerative facial dermatitis seen in cats receiving Progressive weight loss and loss of muscle mass (i.e.,
spironolactone have not been reported to date with torse- cardiac cachexia) often occurs with end-stage chronic
mide, making it a superior choice to this drug pending heart failure and may be due to decreased caloric intake
further data. Torsemide is available as 5, 10, 20, or 100 mg as well as a catabolic state caused by increased proin-
tablets (brand name: Demadex), such that compounding flammatory cytokines (tumor necrosis factor-α, inter-
may be necessary for accurate dosing in cats. The supe- leukin 1, interleukin 2, interleukin 6) or neurohormonal
rior diuretic effect may likewise cause greater electrolyte imbalance including resistance to insulin, growth
disturbances and/or volume depletion, and routine hormone, and ghrelin (von Haehling et al. 2009; Pajak Congestive Heart Failure
monitoring, as for furosemide, is necessary. et al. 2008). Arterial thromboembolism may occur in
cats with heart failure. A left atrial thrombus may form
Treatment of Anemia secondary to one or more alterations in Virchow’s triad,
Anemia is an independent risk factor for mortality in including blood stasis within a severely dilated left
people with systolic or diastolic heart failure (Groenveld atrium, left atrial endothelial disruption, and a proco-
et al. 2008; Silverberg et al. 2008; Klapholz et al. 2009; agulable state. Development of tachyarrhythmias such
Besarab et al. 1998). Anemia decreases the oxygen- as atrial fibrillation, supraventricular tachycardia, or
carrying capacity of blood, and induces a high output ventricular tachycardia may lead to further decompen-
cardiac state that worsens volume overload to the heart. sation of heart failure, because tachycardia increases
Correction of anemia using erythropoietin has been diastolic filling pressure.
studied in people with heart failure, and is associated The most common diagnostic tests used for monitor-
with 90% reduction in heart failure hospitalizations, ing cats with heart failure are radiographs, blood
decreased furosemide dose, increased exercise capacity, chemistry, and systemic blood pressure. Cats treated for
decreased functional heart failure class, and slower acute heart failure require frequent in-hospital monitor-
decline in glomerular filtration rate (Silverberg 2001, ing including, at minimum, renal panels every 12–24
2008). The incidence of anemia in cats with heart failure hours and radiographs every 24–36 hours. Once dis-
has not been studied, but it may be common. Correction charged from the hospital, a recheck should be planned
of underlying or precipitating causes of anemia is neces- in 5–7 days for assessment of hydration status, degree of
sary. In cats with a nonregenerative anemia, use of azotemia, radiographs for assessment of heart failure
erythropoietin may be helpful to normalize the hema- status, and systemic blood pressure measurement.
tocrit, and intermittent doses may be needed to main- Nonhospitalized cats treated for mild heart failure
tain a normal hematocrit. Correction of anemia may be should be seen 1–2 weeks after initiation of therapy, for
particularly important in cats with progressive or refrac- radiographs, serum chemistry, and systemic blood pres-
tory heart failure (see Chapter 24). sure measurement. A recheck echocardiogram may be
performed after several weeks to months to assess myo-
cardial function, degree of atrial dilation, and presence
COMPLICATIONS AND MONITORING
of spontaneous contrast or an intracardiac thrombus.
Possible complications, and monitoring instituted to iden-
tify them early should they occur, include the following: Azotemia
Progressive azotemia is not uncommon in patients
• Dehydration and azotemia are the most common treated with loop diuretics and vasodilators (ACE inhib-
complications in cats treated for heart failure. Other itors) for heart failure (see Chapter 24). Azotemia in