Page 368 - Feline Cardiology

384 Section M: Pulmonary Arterial Disorders

edema from overperfusion of the nonthrombosed lung, Table 25.1. Conditions identified in association with naturally
atelectasis and decreased lung compliance due to reduced occurring pulmonary thromboembolism in 52 cats*
surfactant, and humoral factors causing bronchocon-
striction and increased airway resistance. Intravenous catheters 21
The concept of Virchow’s triad, consisting of sluggish Peripheral venous 17
blood flow, endothelial disruption, and hypercoagula- Jugular venous 2
bility of the blood, evolved specifically from a search for Hemodialysis (both with clot 2
understanding the origin of pulmonary thromboembo- sonographically apparent at tip)
lism (Dickson 2004). It describes the three mechanisms Neoplasia 17
by which thrombus formation may occur. In cats, an Lymphoma 3
underlying disorder almost invariably seems to be Bronchiolar carcinoma 2
present when pulmonary thromboembolism occurs (see Metastatic carcinoma (pancreatic 2
Table 25.1). For example, in the two largest case series, [n = 1])
45/46 cats had identifiable concurrent illness associated Type of neoplasm not specified 10
with pulmonary thromboembolism (Norris et al. 1999; Heart disease 16
Schermerhorn et al. 2004). Cause-and-effect relation-
ships have not been formally established, but if concur- Hypertrophic cardiomyopathy 5
rent disorders contribute to thromboembolism, the Endocarditis 3
exact mechanism by which the original thrombus forms Restrictive cardiomyopathy 2
is likely dependent on the trigger. For example, neo- Heartworm disease ** 2
plasms have been documented to cause platelet hyperag- Infiltrative lymphoma 1
gregability (Thomas and Rogers, 1999), and heart disease Dilated cardiomyopathy 1
associated with cardiac chamber enlargement can cause Toxoplasma myocarditis 1
blood flow stasis, as evidenced by spontaneous echo- Tricuspid regurgitation 1
genic contrast seen in cats with enlarged atria (Schober Corticosteroid administration 9
and Maerz 2006). Of 29 cats with pulmonary thrombo- Disseminated intravascular coagulation 5
embolism in one series, 21 (72%) had intravenous cath- Protein-losing nephropathy 4
eters, potentially providing a surface for platelet Protein-losing enteropathy 4
aggregation within the venous system where thrombi Pancreatitis 2
could form and embolize to the pulmonary arteries Nonhemolytic anemia 2 2 2
(Norris et al. 1999). A case of defecation-associated
Pulmonary Arterial Disorders lodgement of a thrombus by changes in abdominal pres- Other 7 1 1 1 1
Immune-mediated hemolytic anemia
syncope was speculated to have been fatal due to dis-
Sepsis
sure (Valsalva maneuver), resulting in massive pulmonary
Glomerulonephritis
thromboembolism documented at necropsy (Whitley
and Stepien 2001).
Bacterial pneumonia
Hepatic lipidosis
Signalment
Feline infectious peritonitis
Cats of any age may suffer from pulmonary thrombo-
embolism. Affected cats have ranged in age from 10
Humeral fracture repair (fat embolism)
months to 16 years (Schermerhorn et al. 2004; Norris Encephalitis 1 1 1
Dorsolumbar abscess and feline
et al. 1999), with a bimodal age distribution noted in leukemia infection
one group (6 cases in cats aged 4 years or less;
none between 4 and 8 years; and 11 cases in cats aged
>8 years) (Schermerhorn et al. 2004). There is no appar- * numbers exceed a total of 52 because 1 case series (Norris)
described multiple associated conditions for each case, as
ent gender (23 male, 23 female in 2 large case series) applicable, totaling 68 associated conditions in 29 cats
(Schermerhorn et al. 2004; et al.; Norris et al. 1999) or ** and numerous additional cases of pulmonary
breed predilection. thromboembolism described in experimental feline heartworm
infections
History and Chief Complaint Refs: Norris et al. 1999; Schermerhorn et al. 2004; Davidson
et al. 2006; Dvorak et al. 2000; Pouchelon et al. 1997; Sottiaux
Historical findings and presenting complaints of cats and Franck 1999; Schwartz et al. 2001; Whitley and Stepien
later found to have pulmonary thromboembolism 2001.
appear to fall into two categories: respiratory abnormali-