Radiology of Cardiac Disease

Question 1

Answer 1

• Overexposure
• This radiograph is very dark and it is very difficult to see anything in the pulmonary parenchyma. Thus, pulmonary oedema could be easily overlooked.

Question 2

Answer 2

• Poor Positioning and Underinflation
• The dog is poorly positioned - notice how the ribs on one side of the thorax are malaligned with those on the other side. Basically, the dog looks twisted, probably because it is trying to get up. Also lungs are poorly inflated, so look small with increased opacity. This could be incorrectly interpreted as a sign of pulmonary oedema.
• Repeat radiographs under general anaesthesia with the dog well positioned and the lungs inflated show no evidence of pulmonary oedema. Better quality radiographs are much easier to interpret.

Question 3

Answer 3

• The thoracic limbs have not been extended cranially and there is quite marked rotation of the thorax.
• Unfortunately this appearance is quite common in unsedated cats.

Question 4

Answer 4

• Underexposure
• Due to underexposure the film is very white.
• This can lead to overinterpretation of normal lung opacities as oedema

Question 5

Answer 5

• Underinflation
• There is partial collapse of the right lung, causing increased opacity and an apparent right-sided cardiac bulge. This effect is most likely to be caused by right lateral recumbency prior to taking this film.
• Repeat radiography without lateral recumbency resulted in a much better quality film with no evidence of pulmonary oedema and normal heart shape and size for the breed. The final diagnosis in this case was laryngeal paralysis.

Question 6

Answer 6

• Underinflation
• The lungs are underinflated, resulting in increased opacity which has been incorrectly interpreted as pulmonary oedema.
• Repeat radiographs taken with the lungs inflated showed cardiomegaly but no pulmonary oedema

Question 7

Improving Radiographic Quality

Answer 7

• A radiographic exposure is a combination of the energy of the beam (kVp), the number of x-ray photons per unit time (mA) and the duration of the exposure (s).
• Using a low kVp results in a high contrast image (good for the abdomen), while using a high kVp results in more shades of grey (good for the thorax where there is already much inherent contrast).
• You will see more structure in the lung (mainly vessels) when using a high kVp technique.

Question 8

Answer 8

• Normal Feline Thoracic Radiographs
• There is relatively little variation between cat breeds, compared with dogs.
• The main variation is age-related: in older cats, the long axis of the heart becomes progressively more horizontal, eventually becoming parallel to the sternum

Question 9

Answer 9

• Left Ventricle
• The left ventricle is highlighted. It occupies the left side of the heart on the dorsoventral projection and the caudal aspect of the cardiac silhouette on the lateral projection

Question 10

Answer 10

• Caudal Vena Cava
• The caudal vena cava emerges through the caval hiatus of the diaphragm to the right of midline and enters the right atrium

Question 11

Answer 11

• Normal Canine Radiographs
• This is a more complex area than the normal feline heart as there is wide variation between breed and type of dog.
• Deep-chested breeds (e.g. Dobermann) have narrow, upright, tall hearts, whereas barrel-chested breeds (e.g. Springer spaniel) have wide, globular, quite short hearts.
• It is important to be aware of breed variation in order to avoid overinterpreting radiographs

Question 12

Answer 12

• Right Atrium

Question 13

Answer 13

• Aorta
• The aorta exits the dorsal aspect of the cardiac silhouette and courses caudally in the dorsal mediastinum.

Question 14

Answer 14

• Enlarged LV
• The most marked abnormality is that cardiac silhouette is increased in height with marked dorsal displacement of the trachea.
• Debatably, the cardiac silhouette is also slightly widened, with increased sternal contact, but this is not convincing.
• Also, the caudal cardiac border is still fairly curved, so there is no sign of left atrial enlargement. The final diagnosis in this dog was dilated cardiomyopathy.

Question 15

Answer 15

• Enlarged LA
• There is a bulge in the caudal cardiac border typical of left atrial enlargement. There is also elevation of the trachea indicating overall increased height to the heart, hence probably left ventricular enlargement too.

Question 16

1yo cat with muffled heart sounds found at a pre-anaesthetic check. Clinically normal. HR 190bpm, VHS 13.5, heart measures 6 rib spaces in width.

What is the chamber abnormality?

Answer 16

• none
• The cardiac silhouette is not clearly visible. There is confluence between the pericardium and the diaphragm and the pericardial contents are inhomogeneous. There are coiled tubular soft tissue opacities which appear similar to small intestinal loops. The transverse colon can be seen in the cranial abdomen and is cranially displaced. The stomach cannot be seen cranial to this, suggesting that it is displaced. The final diagnosis was congenital peritoneopericardial diaphragmatic hernia

Question 17

8 year old Australian Cattle dog with a grade 2/6 systolic heart murmur, cough and HR 140bpm. VHS 9.5, heart measures 3.5 rib spaces in width.

What is the chamber abnormality?

Answer 17

• Enlarged RV
• Variation in the shape of the heart between dogs makes it difficult to judge right ventricular enlargement.
• In this case, you might be suspicious because there is increased sternal contact and rounding of the cranial cardiac border on the lateral view and rounding of the right lateral border on the DV view.
• However, there are a couple of other important findings that fit with right ventricular enlargement: enlargement of the pulmonary artery (1-2 o’clock on the DV projection, yellow arrow) and dilation of the caudal lobar arteries (red arrows).
• This combination of findings is characteristic of heartworm (Dirofilaria) infestation.

Question 18

7 year old female Standard Poodle, collapsed, pale mucous membranes, HR 50bpm. VHS 9.5, heart measures 2 rib spaces in width.

What is the chamber abnormality?

enlarged LV, LA, RV or RA?

Answer 18

• none above (not a chamber abnormality) - microcardia due to hyperadrenocorticism
• The cardiac silhouette is reduced in size (even though the VHS is within the normal range) and there is reduced sternal contact.
• The radiological diagnosis is microcardia, differentials include shock, blood loss, hypoadrenocorticism, iatrogenic and pulmonary emphysema.
• The final diagnosis was hypoadrenocorticism (Addison’s disease)

Question 19

6 year old British Shorthaired cat, depressed, inappetent, HR 160bpm. VHS 10.5, heart measures 3.5 rib spaces in width.

What is the chamber abnormality?

enlarged LV, LA, RV or RA?

Answer 19

• none of the above –> pericardial fluid
• The cardiac silhouette is enlarged but rounded, with no specific chamber enlargement.
• The final diagnosis was pericardial fluid, secondary to plasma cell neoplasia.
• It can be difficult to differentiate pericardial disease from primary cardiac disease, particularly in the cat, but the overall rounding of the margins and crispness of the cardiac silhouette suggests pericardial disease.
• Echocardiography would obviously be useful in a case like this