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Chapter 8 Heart

Methods of imaging the heart


Diagnostic catheterization has predominantly been replaced by echocardiography (including transoesophageal echocardiography), radionuclide ventriculography and MRI. Angiocardiography is usually used as part of an interventional therapeutic procedure and can be performed simultaneously with cardiac catheterization during which pressures and oximetry are measured in the cardiac chambers and vessels that are under investigations. The right heart, left heart and great vessels are examined together or alone, depending on the clinical problem.



As a result of advances in CT technology, non-invasive cardiac imaging is becoming central to the diagnosis and management of patients with cardiac disease. This is the result of fast scan times and cardiac gating facilities available with multidetector CT scanners. Whilst the examination is tailored to assessment of the cardiac structures, CT imaging gives the benefit over conventional cardiac and coronary angiography of demonstrating clinically significant non-cardiac findings within the adjacent mediastinum, lungs or upper abdomen,1 and can give additional information regarding plaque characterization.

Cardiac CT may be performed as:

The coronary artery calcium (CAC) score is calculated from the volume of calcium present in the coronary arteries. A high score indicates an increased risk of adverse coronary events and CAC scoring has been used as a screening tool for subclinical cardiac disease. Absence of coronary artery calcification does not exclude atheroma but is associated with a low risk of adverse coronary event. Evidence shows that scores will probably need to be matched to age, sex and ethnic background.2

Coronary computed tomographic angiography

Documented mean effective radiation dose for coronary CTA ranges from 6 to 25 mSv3 and reported mean effective dose for conventional catheter angiography is 5.6 mSv.4 Further improvements in CT technology continue to reduce effective dose but there must be constant awareness with attempt to minimize dose wherever possible. Tailored coronary CTA is well-documented to have a high negative predictive value for coronary artery stenosis.5,6


The exact technique will depend on individual CT scanner technology and requires a multidetector CT which is 16 slice or above. Each CT manufacturer will advise scan protocols tailored to their specific scanners; however, general parameters useful for coronary artery assessment cardiac CT are as follows:7