Felis ISSN 2398-2950

Radiology: cardiac examination

Contributor(s): Fraser McConnell, Mark Rishniw, Jordi Lopez-Alvarez

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.
Clinical tip:
Question: What is the normal VHS score in cats?
Answer: 7.5 +/- 0.3

Radiological evaluation of the heart

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Pulmonary assessment

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Further Reading

Publications

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

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.


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