Chapter

Cardiac investigation—nuclear and other imaging techniques

Nikant Sabharwal and Harald Becher

in Oxford Textbook of Medicine

Fifth edition

Published on behalf of Oxford University Press

Published in print May 2010 | ISBN: 9780199204854
Published online May 2011 | e-ISBN: 9780199570973 | DOI: http://dx.doi.org/10.1093/med/9780199204854.003.160303_update_001

Series: Oxford Textbooks

Cardiac investigation—nuclear and other imaging techniques

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Myocardial perfusion scintigraphy

Three radioisotopic tracers are routinely used in single photon emission computed tomography (SPECT) imaging: thallium-201 and technetium-99 m (bound to either sestamibi or tetrofosmin). Imaging can be performed at rest or with stress (exercise or pharmacological), comparison allowing determination of whether regional perfusion is normal, or there is ischaemia, or there is infarction/scar.

Myocardial perfusion imaging is minimally invasive, and—in contrast to other methods of investigation—is not limited by exercise capacity, airways disease, abnormalities of the resting ECG, pacemakers, or acoustic windows.

In the investigation of the patient with possible coronary artery disease, a normal SPECT study is very reassuring, predicting a very low chance of a major cardiac endpoint event in the following few years (<1% per year). High-risk markers on SPECT provide additional prognostic value to clinical and electrocardiographic variables, and decisions about revascularization can be usefully informed by SPECT imaging.

ECG-gated SPECT allows images to be taken throughout the cardiac cycle, when comparison of end-systolic and end-diastolic images then allows volumetric analysis and calculation of left ventricular ejection fraction.

Positron emission tomography (PET)

Perfusion can be assessed with nitrogen-13 ammonia or rubidium-82, and metabolism with fluorine-18 fluorodeoxyglucose (FDG). Cardiac PET studies tend to be confined to research institutions, with the metabolic tracer FDG considered to be the ‘gold standard’ for assessment of myocardial viability.

Cardiac MRI

Cardiac MRI can reveal images of spectacular similarity to anatomical cross-sections and is the best method available for quantifying ventricular volumes, ejection fraction, myocardial mass, and differentiating viable (preserved myocytes) from nonviable (fibrotic) myocardium (although echocardiography—which is cheaper and more readily available—remains the first choice in routine clinical practice for many of these indications).

Cardiac MRI is also very useful in assessing patients with congenital heart disease and is particularly indicated for those with complex conditions or in whom it is difficult to obtain good echocardiographic pictures.

Cardiac CT

Multislice spiral computed tomography (MSCT) is indicated to assess pericardial thickening/calcification and is a fast and noninvasive method for the visualization of the coronary arteries. It can also be used to quantify the amount of coronary and aortic valve calcium.

Cardiac CT does not yet match invasive coronary angiography, but many studies have shown a very high negative predictive value, hence cardiac CT appears to be a reasonable test to rule out coronary stenoses in patients with low-to-intermediate likelihood of disease. However, with further developments it is likely that coronary CT will replace invasive coronary angiography for diagnostic purposes.

Chapter.  5442 words.  Illustrated.

Subjects: Cardiovascular Medicine ; Nuclear Medicine

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