Page 266 - Feline Cardiology

Chapter 19: Congestive Heart Failure 273

DIAGNOSTIC TESTING
• Measurement of systolic blood pressure is important and
may identify systemic hypertension or hypotension.
• Elevated central venous pressure (CVP) greater than
Key Points 10 mm Hg is consistent with right heart failure.
Measurement of CVP should be done after removal of
pleural effusion, since significant pleural effusion may
• A minimum data base including complete blood
increase central venous pressure in the absence of right
count, chemistry, urinalysis, and thyroxine level (if age
appropriate) should be done as a baseline evaluation of heart failure.
• Pleural effusion analysis and cytology results often
overall organ function and metabolic status.
• Routine cardiovascular tests include thoracic are nonspecific and cardiogenic pleural effusion is
characterized as a transudate, modified transudate,
radiographs, electrocardiogram, systemic blood pressure
measurement, and an echocardiogram. chylous, or pseudochylous fluid.
• Thoracic radiographs are essential for diagnosis of
congestive heart failure. Pulmonary edema and/or
pleural effusion develop secondary to left heart failure, General Diagnostic Tests
and pleural effusion and/or ascites develop secondary to
right heart failure. Comprehensive blood work including a complete blood
• Cardiogenic pulmonary edema has a variable count (CBC), serum chemistry, urinalysis, and total thy-
appearance in cats, without a classic distribution roxine level (if age appropriate) should be done on all
pattern. Common radiographic characteristics include cats if clinically feasible. It may be necessary to emer-
patchy to diffuse, interstitial to alveolar pulmonary gency triage and stabilize overtly dyspneic cats prior to Congestive Heart Failure
infiltrates that are often asymmetrical and almost obtaining the minimum database, because these patients
always involve more than one lung lobe. are very fragile. The CBC may reveal mild leukocytosis
Cardiomegaly and atrial dilation are often, but not with a stress leukogram or may be unremarkable. Serum
always, identified, and pulmonary vascular distension chemistry may reveal mild azotemia (prerenal or renal),
may be present. mild hyperglycemia (likely stress-induced), and mildly
• Radiographic appearance of pleural effusion includes
radiopaque fluid accumulation outside the pulmonary elevated liver enzymes. In a large study of 260 cats with
parenchyma, pleural fissure lines, scalloping (rounding) HCM including 120 cats with CHF, 68% of cats had
of the lung lobes, retraction of the lung lobes from the elevated liver enzymes (alanine aminotransferase or
thoracic wall, and obscured diaphragmatic and cardiac aspartate aminotransferase) (Rush et al. 2002). Urinalysis
silhouettes. A dilated caudal vena cava is often present may identify hyposthenuria in cats with concurrent
in cats with right heart failure. Dorsal deviation of the renal insufficiency or urinary tract infection/
trachea in the presence of significant pleural effusion is pyelonephritis in azotemic cats. It is important to iden-
not specific for cardiomegaly. tify cats with underlying renal insufficiency or renal
• An electrocardiogram is the test of choice for evaluation failure, because these cats may be less tolerant of aggres-
of an arrhythmia. The most common arrhythmias sive diuretic therapy and may require more frequent
diagnosed in cats with heart failure are: supraventricular monitoring of renal values during treatment. Total thy-
tachycardia, atrial fibrillation, ventricular premature roxine level is important to evaluate for concurrent
complexes, and ventricular tachycardia. A left axis hyperthyroidism, because this provides a target for
deviation (or left anterior fascicular block pattern) is
often seen in cats with hypertrophic cardiomyopathy but treatment. Free thyroxine concentration by equilibrium
it is nonspecific and may also occur in normal cats. dialysis may be done in cats with a thyroxine level
• A “triage” echocardiogram is a valuable tool to in the equivocal range to confirm whether there is
determine initially whether there is significant enough early hyperthyroidism, which may be a complicating
cardiac disease to cause congestive heart failure in the factor in heart failure. Overall, the minimum database
dyspneic cat. Goals of the “triage” echocardiogram is not useful to confirm heart failure, but it is essential
include evaluation of presence and severity of pleural to assess the metabolic status of the cat and to determine
effusion or pericardial effusion, assessment of atrial size, baseline renal and electrolyte values prior to diuretic
and assessment of myocardial function. therapy.
• A comprehensive echocardiogram should follow the
triage echocardiogram once the patient is stable. The Routine Cardiovascular Diagnostic Tests
comprehensive echocardiogram provides detailed
evaluation of cardiac structure and function to help Thoracic radiography
guide optimal treatment and prognosis. Thoracic radiographs are an essential diagnostic tool for
confirmation of congestive heart failure. Along with