Introduction

• Radiology plays an important part in the diagnosis and management of cardiac disease. It allows assessment of the pulmonary vasculature and lungs which is not possible with echocardiology.
• Radiology also plays an important role in the differentiation of cardiac and respiratory cough.

Radiographic considerations

• The radiographic technique is particularly important in thoracic imaging   Radiography: thorax.

Positioning

• For the investigation of cardiac disease a right lateral projection and dorsoventral (DV) projection should be taken.
• Careful positioning is important, particularly to prevent rotation of the thorax which can lead to a false impression of mild left atrial enlargement.
• The heart has a complex shape and even small degrees of rotation can make assessment of chamber size unreliable, particularly on the DV projection.

Restraint

• Care must be taken to ensure that the stress of radiography will not cause further decompensation in animals with congestive heart failure.
• Oxygen supplementation by a face mask may help ease the patient's respiratory distress improving the quality of the radiographs, although some cats may not tolerate this well and stress can potentially worsen the situation.
• A DV projection can usually be taken without sedation in dyspnoeic animals.
• The lateral projection can then be taken after the patient's condition has been stabilized.
• In most cases, however, it is safer to give a low dose of sedation if required than to struggle with a dyspneic animal.
• The combination of midazolam Midazolam and ketamine Ketamine is a useful sedative for cats. Low dose butorphanol Butorphanol tartrate and alfaxalone Alphaxalone, intramuscularly or intravenously, is also frequently used to sedate unstable cats.

Alpha 2 agonists should be avoided.

Exposure factors

• A high kV low mA technique should be used to reduce contrast within the thorax and allow exposure times to be kept as short as possible.
• Movement blur Radiography: film faults is one of the most common problems in thoracic radiography, particularly in dyspneic patients.
• This can be minimized by using a high kV, and using a fast film/screen Radiography: x-ray film combination.

Radiological evaluation of the heart

Pulmonary assessment

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Litster A L & Buchanan J W (2000) Radiographic and echocardiographic measurement of the heart in obese cats. Vet Radiol Ultrasound 41 (4), 320-325 PubMed.
• Litster A L & Buchanan J W (2000) Vertebral scale system to measure heart size in radiographs of cats. JAVMA 216 (2), 210-214 PubMed.

Other sources of information

• Rishniw M (2000) Radiography of feline cardiac disease. In: Veterinary Clinics of North America -Small Animal Practice - Clinical Radiology. Philadelphia: W B Saunders, pp 395-425.