Cardio-computed tomography (synonyms: cardio-CT; CT-cardio, cardiac computed tomography (CT); coronary CT (CCTA)) refers to a radiological examination procedure in which computed tomography (CT) is used to image the heart and its supplying vessels. Cardio-CT can be divided into different examination modalities. One is calcium scoring (calcium scoring; determination of the extent of calcified plaques in the coronary arteries (arteries that surround the heart in a coronary shape and supply the heart muscle with blood); calcium score/calcium score/calcium score), and the other is angiography (vascular imaging) of the coronary vessels (coronary arteries; coronary angiography) or bypasses (bypass circulation). All three can accurately reflect the extent of vascular calcification.
Indications (areas of application)
- Screening of patients with multiple risk factors (such as smoking; obesity; suspected atherosclerosis (arteriosclerosis, hardening of the arteries); diabetes mellitus; hypothyroidism (hypothyroidism); periodontitis (inflammation of the periodontium), etc.).
- Exclusion of the early phase of coronary sclerosis/coronary heart disease (CHD); but not in angina pectoris (“chest tightness”; sudden pain in the heart area)/possible sign of infarction).
- In patients with low pretest probability, there is a level IIA or level IIB indication in the diagnosis of CHD
- Primary examination test for evaluation for the presence of CHD.
- After myocardial infarction (heart attack) – assessment of the heart to detect the damaged area of the heart (extent of infarction).
Cardio-CT is not suitable for acute emergencies, as no interventions can be performed. In this case, the method of choice is cardiac catheterization.
The procedure
Computed tomography is one of the non-invasive, that is, non-penetrating, X-ray diagnostic imaging procedures. The body or the body part to be examined is imaged layer by layer with a rapidly rotating X-ray tube. A computer measures the attenuation of the X-rays as they pass through the body and uses this to determine a detailed image of the part of the body being examined.The principle of CT (computed tomography) is to show the differences in density of different tissues. For example, water has a different density than air or bone, which is expressed in different shades of gray. To visualize the vessels, including the coronary arteries, the patient is administered a contrast medium containing iodine. This allows the radiologist to obtain even more precise images of any disease process present during the examination. In addition, a heart rate-lowering drug may be administered to make the heart’s actions more clearly visible. The examination is performed while the patient is lying down. The vascular system of the heart can be imaged within 10 minutes (only 10 minutes are required from the time the patient is placed on the examination table until he or she is removed from the table). The latest devices use the multislice method, i.e. several slices are taken at the same time. Modern examination devices use the 64-slice method, i.e. 64 slices are prepared at the same time. This method can be compared to a Rettig, which is cut in a spiral shape. In this case, however, only one slice is involved, and in the method described above, 64 slices are produced one inside the other as a spiral and processed by the computer. Modern devices also work with a so-called low-dose technique, i.e. only 50% of the radiation is required to produce these precise images with a slice thickness of up to 0.4 mm. New reconstruction algorithms (reconstruction calculation methods) make this precision possible. For imaging of the vessels including the coronary arteries (CT coronary angiography; cCTA, Cardiac computed tomography angiography); coronary CT angiography), the administration of iodine-containing contrast medium is required. Cardiac computed tomography offers two modalities of investigation:
- Native computed tomography (CT; computed tomography without contrast) to quantify coronary calcium by calcium scoring (calcium scoring).
- Contrast-enhanced CT angiography (cCTA; procedure that can be used to visualize blood vessels in the body) for anatomic and morphologic assessment of coronary stenoses (“narrowing of heart disease vessels).
ECG-assisted radiation can also reduce the radiation that occurs during the examination. It is between one and six millisieverts. Two examination techniques are used:
- Retrospective ECG-gated spiral examination; radiation exposure: functional analyses are possible; 5-10 mSv.
- Prospectively ECG-triggered sequential examination (“step and shot”); image acquisition is controlled by the patient’s ECG; functional analyses are now also possible; low radiation exposure: 2-3 mSv
Cardiac computed tomography is now feasible using dual-source CT (DSCT) technology and CT systems with a large detector width (256-line single-source CT [SSCT]) during a single heartbeat. Calcium Scoring
Quantification of coronary calcium is performed by the Agatston method:
| Agatston score category | Agatston score risk percentiles |
| 0 (no coronary calcifications) | 0% (very low risk) |
| 1-10 (minimal coronary calcifications) | 1-25% (low risk) |
| 11-100 (mild coronary calcifications) | 26-50% (mild risk) |
| 101-400 (moderate coronary calcifications) | 51-75% (moderate risk) |
| >400 (severe coronary calcifications) | 76-95% (high risk) |
Calcium scoring is considered a reliable risk predictor. CT coronary angiography (cCTA).
Quantitative evaluation of cCTCA is performed in a standardized manner using the CAD-RADS (Coronary Artery Disease Reporting and Data System) system by determining the maximum percent stenosis diameter using the following graduation:
| CAD-RADS category | Stenosis |
| 0 | No visible stenosis (0%) |
| 1 | minimal stenosis (1-24%) |
| 2 | Mild stenosis (25-49%) |
| 3 | moderate stenosis (50-69%) |
| 4 | severe stenosis (70-99%) |
| 5 | total vessel occlusion (100%) |
CT coronary angiography provides a reliable and rapid exclusion of stenosing coronary artery disease (CAD). Furthermore, the procedure allows reliable long-term prognosis in patients without evidence of CAD. In the presence of intermediate stenosis, fractional flow reserve is measured. CT-based measurement of fractional flow reserve (FFR)
FFR indicates the ratio of the mean blood pressure distal to the stenosis to the mean aortic pressure; considered a measure of how much a stenosis restricts blood flow in the coronary vessel; gold standard for analyzing coronary stenosis; usually measured by invasive coronary angiography. CT-based measurement of FFR is now possible (= CT-FFR); the value can be calculated for any segment of the coronary system. Indication
- Angiographically moderate stenosis in:
- Inconclusive clinic or
- When ischemia is inconclusive or not present.
| FFR value | Interpretation |
| 1 | Normal value |
| > 0,80 | Exclusion of hemodynamically relevant stenosis. |
| < 0,75 | Hemodynamically relevant lesion |
| Meanwhile, a cut-off value of 0.8 has become accepted | |
Note: The FAME trial confirmed that patients with stable coronary artery disease (CAD) and stenoses with an FFR >0.8 do not benefit from percutaneous coronary intervention (PCI). Myocardial perfusion CT
In addition to the previously listed classic examination modalities, myocardial CT perfusion has now been added for ischemia diagnostics (diagnostics to detect inadequate perfusion of the myocardium/cardiac muscle). The functional test is performed at rest and under pharmacological stress. In this way, fixed and stress-induced ischemia can be visualized and differentiated. The procedure allows morphological and functional analysis of myocardial ischemia (reduced supply to the myocardium/cardiac muscle) with high precision. Further notes
- Cardiac computed tomography (cardiac CT) avoided six of seven cardiac catheterization examinations in patients with chest pain or atypical angina (chest tightness, heart pain) in a randomized trial with no increased incidence of cardiovascular disease in the first three years afterward. There was no significant difference for a MACE event (“major adverse cardiovascular event”; defined here as apoplexy (stroke), myocardial infarction (heart attack), cardiac death, unstable angina, or revascularization) when comparing the cardio-CT group and the cardiac catheterization patients.
- The Coronary Artery Risk Development in Young Adults(CARDIA) study showed that participants in their early 30s to mid-40s who had coronary calcium (calcium in the coronary arteries) on native CT (computed tomography without contrast), even if it was minimal, had five times as many adverse events due to coronary artery disease (CAD; Disease of the coronary arteries) occurred in the subsequent 12.5 years.
- In symptomatic patients with suspected myocardial ischemia, positron emission tomography (PET)performed best in direct comparison with coronary CT angiography and single-photon emission tomography (SPECT).
- Unclear chest pain: in these patients, acute coronary syndrome (ACS; ST-elevation myocardial infarction (STEMI) non-ST-elevation myocardial infarction (NSTEMI) unstable angina (UA)) was diagnosed in 3% of patients with a coronary calcium score of 0 and in 23% with a score >0.
- In patients with IOCA (ischemia and no obstructive coronary artery disease; “non-obstructive CHD”), some of whom have pronounced angina pectoris symptoms and positive stress test findings (echocardiogram), no relevant coronary stenoses (narrowing of the coronary arteries) are seen on cardiac CT.
- Computed tomographic coronary angiography (CCTA).
- Computed tomographic coronary angiography (CCTA) achieves sensitivity (percentage of diseased patients in whom disease is detected by use of the procedure, ie, a positive test result occurs) and negative predictive value of greater than 95% because of its precise visualization of the coronaries. It outperforms all other noninvasive methods in terms of diagnostic sensitivity for coronary artery disease (CAD).The procedure is suitable for determining the hemodynamic relevance of coronary artery stenoses, by the following measures: Determination of
- Coronary flow reserve, ie, virtual fractional flow reserve (FFR; indicates the ratio of mean blood pressure distal to the stenosis (narrowing) to mean aortic pressure).
- Myocardial perfusion (blood flow to the myocardium; myocardial CT perfusion).
CCTA can be used as a primary diagnostic procedure in patients with an intermediate pretest probability of CHD in the low range, and secondarily in patients with an unclear stress test result. Cardiac catheterizations will decrease as a result.
- SCOTHEART trial: in patients with stable angina, long-term results have shown early coronary CT angiography (CCTA) to be useful for diagnosis. In particular, nonfatal myocardial infarctions were reduced. Note: In the CCTA group, both more secondary preventive and more antianginal drugs were used.CONCLUSION: CCTA may be the appropriate procedure for first-line diagnosis of suspected coronary artery disease (CAD).
- The SCOT-HEART study showed that cardiac CT angiography (= cardiac computed tomography with angiography of the coronary arteries (CTA); Cardiac computed tomography angiography, CCTA) has a significant impact on the incidence of diagnosis of coronary artery disease (CAD; coronary artery disease) and its therapy. The 5-year incidence of the primary endpoint (cardiac death or nonfatal myocardial infarction) was significantly lower in the CTA group than in the standard group (2.3 vs. 3.9%; p = 0.004).
- Computed tomographic coronary angiography (CCTA) achieves sensitivity (percentage of diseased patients in whom disease is detected by use of the procedure, ie, a positive test result occurs) and negative predictive value of greater than 95% because of its precise visualization of the coronaries. It outperforms all other noninvasive methods in terms of diagnostic sensitivity for coronary artery disease (CAD).The procedure is suitable for determining the hemodynamic relevance of coronary artery stenoses, by the following measures: Determination of
- In one study, CT and MRI scans performed as part of interventional cardiology resulted in noncardiac incidentalomas (incidentally found space finding (tumor) during an imaging procedure, without the presence of clinical symptoms; most commonly renal cysts in 16.3%, pulmonary nodules in 13.3%; cancer was newly detected in 1.6%) in 43.1% of cases.
- A long-term analysis by the CAC Consortium has shown that asymptomatic patients with a coronary artery calcium (CAC) score of 0 have consistently low cardiovascular, cancer, and all-cause mortality (death) rates over 12 years. The study is based on data from more than 66,000 asymptomatic individuals with an average age of 54 years.