Page 369 - Feline Cardiology

Chapter 25: Pulmonary Thromboembolism and Hypertension 385

ties (22/50, 44%), nonspecific signs of ill thrift such as nary thromboembolism. Loud breath sounds (Sottiaux
lethargy (19/50, 38%), and loss of appetite (16/50 [32%]) and Franck 1999), a rapid heart rate, and soft heart
( Norris et al. 1999; Schermerhorn et al. 2004; Davidson sounds may mask such a finding in the cat with pulmo-
et al. 2006; Dvorak et al. 2000; Pouchelon et al. 1997; nary thromboembolism.
Sottiaux and Franck 1999; Schwartz et al. 2001; Whitley
and Stepien 2001). The combination of lethargy, Differential Diagnosis
anorexia, and respiratory distress appears to be common. The main differential diagnoses to consider are primary
Unfortunately, such signs also are nonspecific and intrathoracic disorders and systemic diseases, depending
overlap in clinical presentation exists with congestive on whether clinical abnormalities are mainly respiratory
heart failure, systemic disease causing metabolic acidosis or nonspecific, respectively. Pulmonary edema, pneu-
and compensatory efforts that trigger tachypnea or monia, pulmonary contusions due to trauma, heart-
dyspnea and primary pulmonary parenchymal diseases. worm disease, malignancy or other pulmonary
In specific contexts, such as fat embolism due to intra- infiltrative processes, pneumothorax, and pleural effu-
medullar bone pinning under general anesthesia in one sion of any cause are important differential diagnoses
cat or acute increases in abdominal pressure in a cat with for respiratory signs, and many may cause systemic signs
heart disease and pancreatic malignancy, embolism of illness such as lethargy and anorexia. Lethargy and
appears to be so fulminant as to produce no premonitory anorexia alone may be caused by virtually any severe
signs (Schwartz et al. 2001; Whitley and Stepien 2001). illness in cats. Therefore, these retrospectively identified
chief complaints of cats with pulmonary thromboem-
bolism confirmed at necropsy illustrate the lack of speci-
Physical Examination ficity of such signs and the diagnostic challenge presented
Respiratory abnormalities are the most commonly noted by many cases of pulmonary thromboembolism in cats.
physical abnormality during examination, but pulmo-
nary thromboembolism rarely is considered as the cause. Diagnostic Testing
For example, of 46 cats with necropsy-confirmed pul- Given the frequency of overlooking this diagnosis, diag-
monary thromboembolism, this diagnosis was suspected nostic testing may occur as a general investigation
only during the antemortem period in 4 (9%) (Norris assessing nonspecific signs, or on occasion, to specifi-
et al. 1999; Schermerhorn et al. 2004). This fact substan- cally evaluate for pulmonary thromboembolism.
tiates the claim that pulmonary thromboembolism in Confirming the diagnosis revolves around diagnostic
general, and in the feline species specifically, is an under- imaging, and even so, pulmonary thromboembolism in
diagnosed disorder. cats is reasonably described as a diagnosis of exclusion
Physical examination may reveal respiratory abnor- in most cases.
malities, and/or signs that are related to the concurrent
disorder rather than to pulmonary thromboembolism. Initial Tests
For example, in 29 cats examined while suffering from All cats with suspected pulmonary thromboembolism
pulmonary thromboembolism, 21 (72%) were lethargic, should undergo routine heartworm testing including a Pulmonary Arterial Disorders
16 (55%) were tachypneic or dyspneic, 13 (45%) were heartworm antigen test and a heartworm antibody test
felt to show signs of dehydration, 8 (28%) were hypo- if geographically relevant (see Chapter 23). A minimum
thermic, and 5 (17%) were icteric (Norris et al. 1999). database including complete blood count, serum chem-
Findings potentially associated with critical or near- istry, urinalysis, and, if clinically applicable, thyroxine
moribund states (bradycardia, weak or absent pulse) are level should be done. If proteinuria is present, a urine
described in a few cases, but specific cardiac abnormali- protein creatinine ratio should be done to further evalu-
ties are conspicuously absent from most reports. Such ate the presence and severity of proteinuria, as protein-
abnormalities either are not mentioned (Norris et al. losing nephropathy may lead to a hypercoagulable state
1999; Schermerhorn et al. 2004; Dvorak 2000) or specifi- via loss of antithrombin III. Antithrombin III level may
cally are described as having been absent (Davidson be measured in cats with significant proteinuria (Cornell
et al. 2006). One cat with pulmonary thromboembolism University), to further evaluate for the potential of pro-
associated with hypertrophic cardiomyopathy had a left thrombotic state as a precipitating factor for develop-
apical systolic murmur (Pouchelon et al. 1997). A split ment of pulmonary thromboembolism.
second heart sound, which could emerge as a physical As in the dog, cats that have pulmonary thromboem-
manifestation of delayed pulmonic valve closure as a bolism are disadvantaged by the absence of specific
result of thromboembolism-induced pulmonary hyper- diagnostic tests that may reasonably be performed on a
tension, has not been described in any cat with pulmo- distressed animal while also being sufficiently sensitive