Computed tomography of the heart

Computed tomography of the heart ( cardiac CT ) is a special CT angiography of the coronary arteries.

Indications

The investigation is not yet established procedure. For the following indications, a clinical benefit in individual patient studies showed:

• The suspicion of the presence of coronary heart disease (CHD ) and at moderate clinical probability.
• To monitor the progress of a coronary artery bypass.
• For the evaluation of valvular heart disease.
• For the evaluation of cardiac masses.

The cardiac CT has a good negative predictive value. The investigation is therefore well adapted to exclude coronary artery disease. The investigation is but poorly adapted to occupy a coronary heart disease.

Contraindications

Pregnancy is an absolute contraindication. Since iodine-containing contrast agent is used, a contrast agent allergy, hyperthyroidism, renal impairment is a relative contraindication. Arrhythmia, or tachycardia Koronararterienstents reduce usually the image quality and make the implementation of a CT coronary angiography less meaningful.

Implementation

Calcium score

Often a so-called lime -score analysis is carried out before the actual CT angiography of the coronary arteries. The shooting is performed without contrast agent administration; while the layer thickness is in CT angiography in the range of about 1 mm, it is for calcium score recordings 3-5 mm. The Koronarkalkmenge is assessed for each vessel and measured quantitatively in total. To what extent the amount of lime has a prognostic value on the course of coronary heart disease is controversial. At high quantities of lime should be dispensed with subsequent coronary CT angiography, since the evaluation of calcified vessels is inaccurate or even impossible.

CT angiography of the heart

Due to the small diameter of the coronary vessels of the heart and the movement of a CT apparatus to be used for the analysis, which has a high spatial and temporal resolution. Since the detector width of almost all CTs (as of 2011 ) is smaller than the diameter of the heart, the image from recordings of several cardiac cycles must be assembled. The wider the detection of CTs used, the less cardiac cycles are for recording required ( approximately 5 to 10 heartbeats in a 64-slice CT) and the lower the likelihood that are created by an abnormal heart rhythm image artifacts. In order to achieve a lower heart rate and variability, a beta-blocker is administered prior to the study, if possible. Also glyceryl trinitrate are often administered to increase the vessel diameter of the coronary arteries. In parallel to an ECG is derived. For the presentation of the vessels iodinated contrast agent is applied. Stenosis within the coronary arteries can be detected and measured. Distinction can be made if it is calcified plaques or stenoses by noncalcified plaques. If the CT coronary heart disease (CHD ) suspects then mostly invasive cardiac catheterization is required to confirm. Patients at high risk of coronary heart disease should be investigated primarily by means of cardiac catheterization in order to avoid a double burden. In patients with a low to medium probability of coronary heart disease, the cardiac CT examination seems appropriate to exclude CHD.

Radiation exposure

The radiation exposure from a cardiac CT, depending on the CT device and test protocol used at 5 to 30 mSv. This corresponds to 2-15 times the natural background radiation per year in Germany. The radiation cancer risk can be estimated only with difficulty and located according to the calculation formula of the International Commission on Radiological Protection between 1,5:1.000 - 2,5:10.000 additional cancers per study. Through the use of modern CT scanners with appropriate imaging protocols and reconstruction algorithms, the implementation of a CT coronary angiography with about 1 mSv or even Submillisiviertbereich is possible in individual cases; the average radiation exposure is less than 10 mSv.

Alternative test methods

The gold standard for the presentation of heart disease vessels by means of cardiac catheterization / coronary angiography. The CT angiography of the heart may be an alternative examination method for cardiac catheterization in special cases.

The ECG allows the diagnosis of Erregunsausbreitungsstörungen in the heart, such as those occur in a fresh or old myocardial infarction. In addition, the ECG is suitable to identify arrhythmias.

With echocardiography to movement disorders, blood clots and flaps leaks can be identified.

The myocardial scintigraphy is an afflicted with radiation exposure investigation, which may represent acute circulatory disorders in heart muscle.

The cardiac MRI examination is a method without radiation exposure, which may lead to wall motion abnormalities and dysfunction. However, it has not been able to prevail as a standard procedure.

Swell

• Dewey: Coronary CT Angiography Springer Verlag, 2008, ISBN 3540798439