Page 43 - Feline Cardiology

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Radiography

Key Points

• In the early stages of feline heart diseases that cause concentric left ventricular (LV) hypertrophy, LV chamber diameter
may decrease but radiographic heart size remains normal. With progression of such diseases, the left atrium enlarges and
cardiomegaly is therefore usually recognizable on radiographs of cats with moderate or severe concentric left ventricular
hypertrophy.
• Thoracic radiographs provide useful, but limited, information regarding cardiac structure in asymptomatic cats but greatly
assist in narrowing the differential diagnosis in cats with overt respiratory clinical signs. In this clinical scenario they are the
diagnostic test of choice.
• The vertebral heart size as measured on the lateral radiographic projection is a useful technique to objectively assess heart
enlargement in cats (normal <8 V).
• Left-sided heart disease is much more common in cats than biventricular or right-sided heart disease.

Thoracic radiography is an essential part of the cardio- tions are required for a correct cardiac assessment, but it
vascular examination. This modality, which is more is critical to astutely monitor the patient. Some animals
widely available than echocardiography, provides direct may be too dyspneic to allow two radiographic views (or
information about the heart and lungs and may confirm even one) before therapy is initiated.
or exclude a particular clinical diagnosis suspected from Radiographic artifacts include any alteration in the
the history and physical examination. It is also useful for image that leads to hindered visualization of the region
assessing severity of known heart disease and evaluation of interest. Malpositioning, patient motion, incorrect
of therapeutic effect. Also essential in the interpretation patient identification, double exposure, and many other
is prior development of differential diagnoses derived artifacts are possible. Digital radiography is increasingly
from a thorough history and physical examination. available in veterinary radiography, and with its devel-
Although many cardiorespiratory diseases manifest with opment, in addition to these traditional issues, a new set
similar clinical signs (i.e., cough, dyspnea, etc.), heart of artifacts has been introduced. Excellent reviews
failure can usually be differentiated from primary respi- describe the possible artifacts and how to avoid them
ratory disease using thoracic radiographs. In fact, radi- (Drost et al. 2008; Jimenez et al. 2008).
ography is superior to echocardiography for initial Adequate radiographic exposure is achieved when it
evaluation of most coughing or dyspneic feline patients is possible to define the dorsal spinous processes of the
because radiography can provide information regarding cranial thoracic vertebrae superimposed on the scapula.
pulmonary congestion and the respiratory system, unlike The forelimbs should be drawn forward so they are
the echocardiogram. Patient positioning and adequate not superimposed on the cranial thorax (Figure 6.1);
radiographic exposure are important for accurate radio- failure to do so is one of the most common errors in
graphic interpretation, however. A normal heart can feline thoracic radiographic technique, the repercus-
appear abnormal when positioning is incorrect, and the sions of which can be serious (missed lesion, incorrect
reverse is also true. Two orthogonal radiographic projec- diagnosis, overdiagnosis). Timing of the exposure should

Feline Cardiology, First Edition. Etienne Côté, Kristin A. MacDonald, Kathryn M. Meurs, Meg M. Sleeper.
© 2011 John Wiley & Sons, Inc. Published 2011 by John Wiley & Sons, Inc.

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