Page 277 - Feline Cardiology

284 Section G: Congestive Heart Failure

in symptomatic cats with heart failure (Herndon et al. TREATMENT
2002). Normal reference ranges are not interchangeable
between the different cTnI sandwich assays. A positive Outpatient Treatment of Mild to Moderate
cTnI value obligates the clinician to better identify pres- Congestive Heart Failure
ence of heart disease and possibly heart failure by echo- Outpatient treatment includes the following:
cardiography and thoracic radiographs.
• Furosemide is the drug of choice for treatment of
Conclusive Diagnosis congestive heart failure.
Congestive heart failure may be conclusively diagnosed • Furosemide is a powerful loop diuretic that can be
based on radiographic abnormalities of pulmonary given orally at doses ranging from 1 mg/kg PO q 24 hr
edema and/or pleural effusion, cardiomegaly with or for mild congestive heart failure to a maximal dose of
without pulmonary venous distension, and echocardio- 4 mg/kg PO q 8 h for severe refractory heart failure.
graphic evidence of left and/or right atrial dilation. • Because furosemide activates the RAAS, it is recom-
Echocardiography is essential to confirm that there is mended to combine furosemide and an ACE inhibitor
moderate to severe heart disease, since congestive heart for treatment of heart failure.
failure is a consequence of severe heart disease. • ACE inhibitors (enalapril 0.5 mg/kg PO q 12–24 hr,
ramipril 0.5 mg/kg PO q 24 hr, or benazepril 0.5 mg/
Congestive heart failure occurs when there is signifi-
Congestive Heart Failure stolic filling pressure, which leads to left or right atrial • ACE inhibitors may cause functional azotemia by
kg PO q 24 hr) may provide adjunctive benefit for
cantly elevated left ventricular or right ventricular dia-
treatment of heart failure.
dilation, respectively. Therefore, if atrial size is normal,
reducing angiotensin II and dilating the efferent glo-
it can be assumed that the diastolic filling pressure is not
merular arterioles. Azotemia is typically mild, but
significantly increased, and the cat is unlikely to have
may be severe and is usually reversible. Monitoring
congestive heart failure. The only exceptions include a
recent, acute inciting cause such as subcutaneous or
medical therapy is therefore recommended.
intravenous fluid administration, anesthesia, or reposi- renal function at baseline and 1 week after starting
tol glucocorticoid administration, which may lead to • Prophylactic anticoagulant therapy is recommended
heart failure in the face of less substantial left atrial dila- for cats with spontaneous contrast (i.e., smoke) or a
tion or uncommonly normal left atrial size. Other rare thrombus seen on echocardiography, and also may be
exceptions are significant pericardial effusion causing indicated for cats with moderate to severe atrial dila-
cardiac tamponade or constrictive pericarditis (a rare tion. Choices include clopidogrel (18.75 mg PO q 24 hr
disease in cats). The second criterion for conclusive with food), baby aspirin (5–81 mg PO q 3 days), enoxa-
diagnosis of congestive heart failure is the reduction or parin (1.5 mg/kg SC q 8–12 h), or warfarin (0.1–0.2 mg/
resolution of fluid accumulation following appropriate kg PO q 24 hr titrated based on prothrombin time).
diuretic therapy, thus proving that the infiltrates or
pleural effusion were actually due to congestive heart The approach to treating congestive heart failure is
failure and not other systemic disease. Pleural effusion chosen according to severity of signs (dyspnea) and
characteristics that are consistent with heart failure anticipated timeline of improvement (Table 19.1). In the
range from a transudate, modified transudate, pseudo- acute setting, cats may have mild signs for which outpa-
chylous, or chylous effusions. If pleural effusion is clas- tient treatment is acceptable, and these are presented
sified as exudative or hemorrhagic, then the diagnosis is here first. Patients that are candidates for outpatient
not congestive heart failure. In cats with pleural effusion home treatment are those that have mild tachypnea or
and/or ascites, measurement of an elevated central dyspnea, mild pleural effusion or pulmonary edema
venous pressure (≥10 mm, after removal of pleural effu- evident on radiographs, or those having a large volume
sion) supports the diagnosis of right heart failure. A of pleural effusion removed by thoracocentesis with
supportive diagnosis (not definitive) may be based on subsequent normalization or near normalization of
radiographic abnormalities including cardiomegaly and respiratory rate and effort. Patients with acute signs that
pulmonary edema and/or pleural effusion, with resolu- are severe and considered possibly to be life-threatening
tion of the fluid accumulation after diuretic therapy. are discussed second in the section “Treatment of
Since radiographic appearance of heart failure in cats is Hospitalized Cats with Acute Congestive Heart Failure.”
highly variable without a pathognomonic pattern, the Finally, treatment of chronic or refractory heart failure
clinician is encouraged to obtain an echocardiogram to is discussed in the section “Treatment of Refractory
definitively diagnose the etiology and severity of the Congestive Heart Failure.” These cats continue to display
heart disease. clinical signs of dyspnea due to confirmed congestive