CT coronary calcium score is a diagnostic algorithm, usually performed within the framework of CT-coronary angiography and allows quantitative calculation (evaluation of the index) of calcium in atherosclerotic plaques of the coronary arteries. It is a method of objective diagnosis of coronary calcification and a prognostic marker of the progression of cardiosclerosis and coronary heart disease. The calculation of coronary calcium is carried out by a special computer program, the result reflects both the total index and the distribution of the indicator for each coronary artery separately.
The main indications for coronary calcium CT are the presence of atypical pain in the chest area and the need for screening of persons without clinical manifestations of myocardial ischemia who are at risk. It consists of people with hypercholesterolemia, diabetes mellitus, hypertension, obesity, burdened with a family history. The risk group includes smokers, men over 40 years old and women over 45 years old, people who lead a sedentary lifestyle. In addition, coronary calcium screening is prescribed to patients in order to monitor ongoing pharmacotherapy and assess the patency of coronary shunts, as well as to persons who will undergo coronary artery bypass grafting or other operations on heart vessels.
CT coronary calcium score is contraindicated for women carrying a child, regardless of the trimester of pregnancy. Relative contraindications include childhood, the presence of mental illness and claustrophobia, severe obesity (most tomographs are designed for body weight up to 130 kg). The addition of CT by intravenous contrast is contraindicated in persons who have a history of allergic reactions to similar radiopaque drugs, patients with severe renal insufficiency, diabetes mellitus, iodine-dependent thyroid diseases.
Depending on the clinical situation (occurrence of coronary artery disease, heart attack or screening of persons at risk), ECG, ultrasound of the heart, laboratory determination of markers of myocardial infarction (troponins), etc., can be performed beforehand. In most cases, CT coronary calcium score does not require special preparation, however, before the introduction of intravenous contrast, excretory kidney function is evaluated in all patients and a test for individual tolerability of the drug is carried out. When using a contrast agent, it may be necessary to remain hungry for 4-6 hours before the study.
Methodology of conducting
CT coronary calcium score is performed using a CT scanner. Externally, the device, depending on the model, is a large square or circle with a hole in the middle with a platform-table for the patient. Before starting the tomography, the examinee is asked to take off all metal objects located in the chest area (piercings, jewelry), because they are able to “layer” on the pictures. Next, the patient lies down on the table, if necessary, an ECG device is connected to it. After that, the table moves inside the tomograph, and the radiologist goes to the next room, conducts a scan, observes the patient, communicates with him and controls the resulting images. After receiving the first (native) results, intravenous contrast may be administered.
The duration of CT coronary calcium score is 10-20 minutes, depending on the thickness of the sections and the capabilities of the device. At this time, you can hear clicking or clicking of various loudness – the noise that the tomograph makes when taking the next picture. Throughout the study, the patient should lie still. In the native study, unusual somatic sensations do not occur during or after the procedure. When using radiopaque substances, slight dizziness, nausea or headache may occur. The procedure does not cause any complications or consequences for most people.
Interpretation of results
In most institutions, you can get a CT result of coronary calcium as early as 1 hour after passing the scan. As a rule, the patient is given a description of pathological changes and the conclusion of a radiology doctor, a CD with the obtained images and/ or a 3D model, printed copies of the images. Based on the results of CT screening of coronary calcium, it is possible to assess the prevalence and severity of calcification of the coronary arteries. This technique allows you to determine the exact localization of pathological clusters, their density and the degree of narrowing of the vessel lumen. A calcium index is used to unify the results obtained. CI is an indicator that is obtained by multiplying the density factor in Hounsfield units (1-4 HU) by the calcification area of all myocardial vessels. Depending on the obtained CI value, patients are divided into 5 groups.
In patients with CI 0, according to the results of coronary calcium CT, there is no damage to the coronary vessels, respectively, the risk of cardiovascular diseases is very low. With CI 1-10 units, calcification is minimal, the risk of coronary heart disease and heart attack is low. KI from 11 to 100 units . indicates moderate vascular stenosis, probable coronary artery disease and a moderate risk of heart attack. With CI 101-400 units, the number of calcinous plaques is above average, which means moderate hemodynamic disorders, a high probability of coronary heart disease and myocardial infarction. In persons with CI over 400 units . there is a pronounced stenosis of the coronary arteries, which in the near future may lead to myocardial infarction.