Page 346 - Feline Cardiology

Chapter 23: Heartworm Disease 359

graphically in 40% of heartworm positive cats, including
5 (of the 43 cats included) in which the Ag was negative
(DeFrancesco et al. 2001). However, the sensitivity of
echocardiography in these patients is highly operator-
dependent and false positives are possible (Atwell et al.
2001; Atkins et al. 2008). Two-dimensional echocardiog- RV
raphy allows interrogation of the right heart, the main
pulmonary artery, and segments of the right and left
pulmonary arteries. Methodical examination is impor- LV
tant since cats have light infections and detection may
be difficult. The worm cuticle is strongly echogenic and
produces short segments of echogenic parallel lines on
ultrasound imaging (Figure 23.5). From the right para-
sternal short-axis view at the heart base, the main pul- A
monary and central portions of the left and right main
pulmonary arteries should be carefully evaluated for
heartworms.
Eosinophilia and basophilia noted in the complete
blood count are supportive findings, with eosinophilia
being more common (in 63% and 10% of Ab-positive
cats, respectively) (Dillon et al. 2000). However, in AO
another study the eosiniphil and baosphil counts were PA
not significantly different between cats with heartworm LA
infection and cats unlikely to have disease (Atkins et al.
1998). Hyperglobulinemia may also occur in cats with
chronic heartworm disease. Fecal testing for lungworms
is useful to screen for lung parasites and to rule out this
differential in the list of differential diagnoses for a cat
presenting with clinical signs of lower airway disease B
(i.e., heartworm infection, feline-asthma, cardiomyopa-
thy, bronchitis, pulmonary fibrosis, and lung parasites). Heartworm Disease
A tracheal or bronchial wash may be useful for detecting
lung parasitic lesions such as those produced by Filaroides
spp. In heartworm-infected dogs, renal lesions associ-
ated with antigen-antibody glomerular deposition often AO
lead to urine protein loss. Similarly, proteinuria occurs
in experimental feline heartworm disease. However, it PA
was detected only in cats with mature infections (1–10
adult worms) whereas none of the cats that resisted
mature infection were microalbuminuric. Moreover it
was more common in heavily infected, antigen-positive
cats (Atkins et al. 2010).
The bottom line is that diagnosis of feline heartworm C
disease often requires multiple tests. The diagnosis is
particularly difficult to confirm in the subset of cats that Figure 23.5. Right parasternal echocardiographic images
have mild disease. In these cats, immature worms may obtained from a cat with heartworm disease. At least one worm
result in severe pulmonary damage, and yet be nearly is visible on echocardiography. (A) Image obtained at the ven-
impossible to diagnose because they are cleared prior to tricular level. (B) Image obtained at the heart base. (C) Image
maturation (Browne et al. 2005). Since the antibody obtained at the bifurcation of the main pulmonary artery. In all
images, the red arrowheads identify segments of adult heart-
disappears quickly, the only remaining evidence of their worms, which appear as echogenic parallel lines. RV = right
presence may be pulmonary lesions which are virtually ventricle; LV = left ventricle; Ao = aorta; LA = left atrium; PA =
impossible to diagnose as having been caused by heart- pulmonary artery.
worm disease. The syndrome of vascular, airway, and