CT coronary angiogram is a computer angiography of coronary vessels based on scanning the passage of radiopaque substance in certain phases of the cardiac cycle. It is indicated for the study of the state of heart vessels: detection of stenoses, zones of ischemia or myocardial necrosis, calcification and atherosclerosis of coronary vessels; assessment of the degree and extent of the stenosing process. It is carried out to clarify the indications for the choice of the method of treatment of coronary heart disease and control of the patency of stents after CABG and balloon angioplasty. CT of coronary vessels does not replace invasive X-ray coronary angiography, however, it is not inferior to it in terms of diagnostic criteria.
CT coronary angiogram is prescribed primarily to detect pathological changes in the coronary vessels that can lead to the development or exacerbation of coronary artery disease, the occurrence of acute myocardial infarction. For this purpose, angiography is used to determine the cause of pain in the heart and the degree of patency of the coronary vessels, the localization and extent of stenosis, anomalies in the development of arteries. Diagnostics is used to visualize atherosclerotic plaques, blood clots, their location, size, and vascular calcification.
The procedure makes it possible to identify areas of myocardial ischemia, the causes of arrhythmia (a feature of this method is sensitivity to the frequency of heart contractions). Manipulation allows you to visualize changes in the structure of the walls of the arteries feeding the heart, aneurysms, scars. The technique is used at the stage of preoperative preparation of patients for coronary artery bypass grafting (CABG), stenting combined with balloon plastic surgery, or without it. In addition, CT coronary angiogram is one of the methods of observation in the period after CABG and vascular plasty.
A patient with coronary artery pathology undergoes a CT scan only after excluding contraindications or restrictions to this manipulation. If there are any, the study will be replaced by another one or preventive measures will be taken to correct the restrictions. An absolute contraindication to CT is pregnancy due to the teratogenic effect of X-rays on the fetus. Manipulation is not performed in acute heart failure, severe arrhythmia and in children under 5 years of age due to the impossibility of guaranteeing complete immobility of the child.
Since the procedure is radiopaque, a contraindication to it is the intolerance of patients to iodine, as well as the risk of deterioration of the general condition of the subjects suffering from thyroid pathology, diabetes mellitus, severe renal and hepatic insufficiency, myeloma. CT coronary angiogram is not indicated for patients with claustrophobia, patients with mental disorders accompanied by uncontrolled motor activity, general severe condition. According to vital indications, before the procedure, such patients are put into a short-term drug sleep or spend it under the guise of sedatives. Due to the technical characteristics of the tomograph, a relative contraindication is severe obesity.
Manipulation is carried out on an outpatient basis, in conditions of planned or emergency hospitalization in a round-the-clock hospital. Before it is carried out, the possibilities of venous access to the heart are studied, which provides the necessary rate of contrast penetration into the coronary arteries in order to obtain scans of optimal quality, assess the adequacy of the patient to determine the ability to follow the doctor’s instructions during CT coronary angiography. An hour before the study, the patient is offered to take a drug that reduces the frequency of contractions of the heart muscle. Nursing mothers need to stop feeding on the day of manipulation and resume it only after the contrast is completely removed from the body (after 48 hours).
Since CT coronary angiogram is performed with contrast enhancement, on an empty stomach, the patient is advised to stop eating 3-4 hours before the procedure, drink only clear liquids. In addition, all patients undergo a skin allergy test for the tolerability of iodine preparations. In case of a negative result, the general condition of the patient is checked: pulse, blood pressure, ECG data and a catheter with a valve (introducer) is installed into the ulnar vein. To synchronize with the scan, an ECG sensor is placed.
By performing intravenous contrast, the bolus is optimized (administration of the drug within 3-6 minutes) 100 milliliters of saline solution. As a rule, no unpleasant sensations appear at the same time, warmth may be felt as the contrast acts, a metallic taste in the mouth. In rare cases, bleeding is possible at the site of the catheter installation. Iodine preparations stain the vessels on the scans in a bright white color. This improves their visualization, guarantees the clarity of the image. 10 minutes before CT coronary angiogram, the patient takes nitroglycerin to dilate the heart vessels. Sufferers of claustrophobia are offered sedatives.
Methodology of conducting
CT coronary angiogram is performed in a special room shielded from X-rays. Outside of this room, the patient leaves all metal objects and jewelry. The clothes for the study should be loose and comfortable, not contain metal inclusions. Some clinics use disposable underwear sets. The doctor is informed about the presence of implants, pacemakers, endoprostheses in the patient’s body. During the procedure, the medical staff is in the next room and communicates with the patient through a microphone mounted in the tomograph.
During the manipulation, contact between the doctor and the patient is necessary, the execution of specialist commands. Scanning begins some time after contrast is introduced. The study is carried out in the position of the patient lying on his back on the mobile table of the device, which automatically passes through the scanning tunnel. At the same time, the patient does not feel discomfort. Special sensors record and transmit a layered image of the arteries to a computer. After processing the results, a three-dimensional three-dimensional model of the examined organ is formed, which the doctor sees on the tomograph screen.
After completion of CT coronary angiogram, the patient can immediately leave the clinic. The results are deciphered by a radiologist (radiologist). The absence of pathological changes indicates the norm. If any pathology is detected, the question of further management of the patient is decided by the attending physician. He can refer the patient for additional examination, observe on an outpatient basis, prescribe hospitalization (emergency or planned). The images and the conclusion with the results of CT coronary angiogram are given to the patient in his hands, sent to the e-mail address of the examinee or transferred to an electronic carrier.
CT coronary angiogram has a number of advantages over other research methods. It has the ability to simultaneously obtain data on the condition of the heart valves and myocardium associated with hemodynamic disorders. The technique allows you to visualize changes in the valves of the heart muscle as a result of developmental abnormalities, stenosis, as well as to identify pericarditis of various etiologies, which distinguishes it from CT. In some cases, the study is performed in conjunction with visualization of the renal arteries, vessels of the head and neck. The indisputable advantage of the method is the possibility of outpatient examination with an assessment of the condition of the coronary vessels, as well as the pulmonary arteries, aorta, myocardium, pericardium, valves and cavities of the heart.
CT angiography takes less time than MRI. It is allowed to carry out the procedure with an installed pacemaker, the technique allows you to differentiate various vascular diseases, which is impossible with radiography. CT coronary angiogram is performed in order to detect pathological changes in the early stages, in order to prevent their progression, the development of complications, and reduce the risk of death from ischemia. The demand for computed angiography of the heart is explained by its noninvasiveness and diagnostic accuracy in comparison with other manipulations used to study coronary vessels.