Coronarography (coronary angiography)

Coronary angiography continues to be the “gold standard” for diagnosing coronary artery stenosis, determining the effectiveness of drug therapy, PCI and CABG.

Coronary angiography is the contrasting of coronary arteries under X-ray control with the introduction of RVC into the mouths of the arteries and recording of the image on X-ray film or a video camera. Computer hard drives and CDs are increasingly used, and the image quality does not deteriorate.

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Indications for coronary angiography

In recent decades, indications for coronary angiography have been constantly expanding due to the spread of such methods of treating coronary atherosclerosis and coronary heart disease as TBCA with stenting and CABG. Coronary angiography is used to assess the coronary bed (narrowing and its length, severity and localization of atherosclerotic changes), determine treatment tactics and prognosis in patients with symptoms of coronary heart disease. It is also very useful for studying the dynamics of coronary tone, immediate and remote results of TBCA, CABG and drug therapy. Briefly, indications for coronary angiography can be formulated as follows:

1. insufficient effectiveness of drug therapy in patients with coronary heart disease and the decision on other treatment tactics (TBCA or CABG);
2. clarification of diagnosis and differential diagnosis in patients with an unclear diagnosis of the presence or absence of coronary heart disease, cardialgia (difficult to interpret or questionable data from non-invasive and stress tests);
3. determination of the state of the coronary bed in representatives of professions associated with increased risk and responsibility, in cases of suspected signs of coronary heart disease (pilots, astronauts, transport drivers);
4. AMI in the first hours of the disease for (intracoronary) thrombolytic therapy and/or angioplasty (TBCA) in order to reduce the area of necrosis; early post-infarction angina or recurrent MI;
5. evaluation of the results of CABG (patency of aortocoronary and mammary coronary bypass grafts) or PCI in case of recurrent attacks of angina pectoris and myocardial ischemia.

Methodology for performing coronary angiography

Coronary angiography can be performed either separately or in combination with right heart catheterization and left (less often right) pulmonary artery catheterization, myocardial biopsy, when along with coronary bed assessment it is additionally necessary to know the parameters of pressure in the right ventricle, right atrium, pulmonary artery, minute volume and cardiac index, indicators of general and local ventricular contractility (see above). When performing coronary angiography, constant ECG and blood pressure monitoring should be ensured, a complete blood count should be performed and biochemical parameters, blood electrolyte composition, coagulogram, blood urea and creatinine parameters, tests for syphilis, HIV, and hepatitis should be assessed. It is also desirable to have a chest X-ray and duplex scanning data of the iliofemoral segment vessels (if the femoral artery is punctured, which is still the case in most cases). Indirect anticoagulants are discontinued 2 days before the planned coronary angiography with blood clotting monitoring. Patients with an increased risk of systemic thromboembolism (atrial fibrillation, mitral valve disease, history of systemic thromboembolism episodes) may receive intravenous unfractionated heparin or subcutaneous low-molecular-weight heparin during the coronary angiography procedure during the withdrawal of indirect anticoagulants. For planned CAG, the patient is brought to the X-ray operating room on an empty stomach, premedication consists of parenteral administration of sedatives and antihistamines. The attending physician must obtain written informed consent from the patient for the procedure, indicating the rare but possible complications of this technique.

The patient is placed on the operating table, ECG electrodes are applied to the limbs (precordial electrodes should also be at hand if necessary). After processing the puncture site and isolating it with sterile linen, local anesthesia is administered at the arterial puncture point and the artery is punctured at an angle of 45°. When the blood stream is reached from the pavilion, a 0.038 × 0.035 inch guidewire is inserted into the puncture needle, the needle is removed and an introducer is installed in the vessel. Then, 5000 IU of heparin are usually administered as a bolus or the system is continuously flushed with heparinized isotopic sodium chloride solution. A catheter is inserted into the introducer (different types of coronary catheters are used for the left and right coronary arteries), it is advanced under fluoroscopic control to the aortic bulb and, under blood pressure control, the coronary artery orifices are catheterized from the coccyx of the catheter. The size (thickness) of the catheters varies from 4 to 8 F (1 F = 0.33 mm) depending on the access: for femoral access, 6-8 F catheters are used, for radial access - 4-6 F. Using a syringe with 5-8 ml RVC, the left and right coronary arteries are manually contrasted selectively in various projections, using cranial and caudal angulation, trying to visualize all segments of the artery and their branches.

If stenosis is detected, a survey is performed in two orthogonal projections for a more accurate assessment of the degree and eccentricity of the stenosis: if in the left coronary artery, we usually stand in the right anterior oblique projection or direct (this way the left coronary artery trunk is better controlled), in the right (RCA) in the left oblique projection.

The LCA originates from the left coronary sinus of the aorta with a short (0.5-1.0 cm) trunk, after which it divides into the anterior descending (AD) and circumflex (CV) arteries. The ADA runs along the anterior interventricular groove of the heart (also called the anterior interventricular artery) and gives diagonal and septal branches, supplies blood to a large area of the LV myocardium - the anterior wall, interventricular septum, apex and part of the lateral wall. CV is located in the left atrioventricular groove of the heart and gives obtuse marginal branches, left atrial and, in the left type of blood supply, posterior descending branch, supplies blood to the lateral wall of the LV and (less often) the inferior wall of the LV.

The RCA originates from the aorta from the right coronary sinus, goes along the right atrioventricular groove of the heart, in the proximal third it gives off branches to the conus and sinus node, in the middle third - the right ventricular artery, in the distal third - the artery of the acute margin, posterolateral (from which a branch goes to the atrioventricular node) and posterior descending arteries. The RCA supplies blood to the RV, pulmonary trunk and sinus node, the inferior wall of the LV and the interventricular septum adjacent to it.

The type of blood supply to the heart is determined by which artery forms the posterior descending branch: in approximately 80% of cases it comes from the RCA - the right type of blood supply to the heart, in 10% - from the OA - the left type of blood supply, and in 10% - from the RCA and OA - a mixed or balanced type of blood supply.

Arterial access for coronary angiography

The choice of access to the coronary arteries usually depends on the operating physician (his experience and preferences) and on the condition of the peripheral arteries, the coagulation status of the patient. The femoral access is most frequently used, safe and widespread (the femoral artery is quite large, does not collapse even in shock, is located far from vital organs), although in some cases it is necessary to use other routes of catheter insertion (axillary, or axillary; brachial, or radial). Thus, in patients with atherosclerosis of the vessels of the lower extremities or previously operated on for this reason, in outpatients, puncture of the arteries of the upper extremities (brachial, axillary, radial) is used.

In the femoral method, the anterior wall of the right or left femoral artery is palpated well and punctured 1.5-2.0 cm below the inguinal ligament using the Seldinger method. Puncture above this level leads to difficulties in digitally stopping bleeding after removal of the introducer and to a possible retroperitoneal hematoma, below this level - to the development of a pseudoaneurysm or arteriovenous fistula.

In the axillary method, the right axillary artery is most often punctured, less often the left. At the border of the distal area of the armpit, the pulsation of the artery is palpated, which is punctured in the same way as the femoral artery, after local anesthesia with subsequent installation of an introducer (for this artery, we try to take catheters no larger than 6 F in size to more easily stop bleeding and reduce the likelihood of hematoma development at this puncture site after the examination). This method is currently rarely used by us due to the introduction of radial access several years ago.

The brachial or shoulder method has been used for a long time: Sones used it in 1958 for selective catheterization of coronary arteries, making a small skin incision and isolating the artery with the application of a vascular suture at the end of the procedure. When the author performed this method, there was no big difference in the number of complications compared to puncture of the femoral artery, but his followers had a higher frequency of vascular complications (distal embolization, arterial spasm with impaired blood supply to the limb). Only in isolated cases is this approach used due to the vascular complications listed above and the difficulty of fixing the brachial artery during its percutaneous puncture (without a skin incision).

The radial method - puncture of the radial artery on the wrist - has been used more and more often in the last 5-10 years for outpatient coronary angiography and rapid patient mobilization; the thickness of the introducer and catheters in these cases does not exceed 6 F (usually 4-5 F), and with femoral and brachial access, 7 and 8 F catheters can be used (this is especially important in complex endovascular interventions, when 2 or more guidewires and balloon catheters are needed, in the treatment of bifurcation lesions with stenting).

Before puncture of the radial artery, an Allen test is performed with compression of the radial and ulnar arteries to detect the presence of collateralization in case of a complication after the procedure - occlusion of the radial artery.

The radial artery is punctured with a thin needle, then an introducer is inserted into the vessel via a guidewire, through which a cocktail of nitroglycerin or isosorbide dipitrate (3 mg) and verapamil (2.5-5 mg) is immediately injected to prevent arterial spasm. For subcutaneous anesthesia, 1-3 ml of 2% lidocaine solution is used.

With radial access, difficulties may arise in passing the catheter into the ascending aorta due to the tortuosity of the brachial, right subclavian artery and brachiocephalic trunk; other coronary catheters (not Judkins, as with femoral access) such as Amplatz and multi-profile catheters are often required to reach the coronary artery ostia.

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Contraindications to coronary angiography

There are currently no absolute contraindications for large catheterization angiographic laboratories, except for the patient’s refusal to undergo this procedure.

Relative contraindications are as follows:

• uncontrolled ventricular arrhythmias (tachycardia, fibrillation);
• uncontrolled hypokalemia or digitalis intoxication;
• uncontrolled arterial hypertension;
• various febrile conditions, active infective endocarditis;
• decompensated heart failure;
• blood coagulation disorders;
• severe allergy to RVC and iodine intolerance;
• severe renal failure, severe damage to parenchymal organs.

The following risk factors for complications after cardiac catheterization and coronary angiography should be taken into account: advanced age (over 70 years), complex congenital heart defects, obesity, malnutrition or cachexia, uncontrolled diabetes mellitus, pulmonary insufficiency and chronic obstructive pulmonary diseases, renal failure with a blood creatinine level of more than 1.5 mg / dL, three-vessel coronary artery disease or left main coronary artery disease, angina class IV, mitral or aortic valve defects (as well as the presence of prosthetic valves), LVEF < 35%, low exercise tolerance according to the treadmill test (or other exercise tests) accompanied by hypotension and severe myocardial ischemia, pulmonary hypertension (pulmonary artery systolic pressure more than 30-35 mm Hg), pulmonary artery wedge pressure more than 25 mm Hg. Vascular risk factors for complications of coronary angiography: disorders of the blood coagulation system and increased bleeding, arterial hypertension, severe atherosclerosis of peripheral vessels, recent stroke, severe aortic insufficiency. Patients with these risk factors should be closely monitored with hemodynamic monitoring, ECG for at least 18-24 hours after coronary angiography and catheterization. Coronary angiography performed for emergency indications is also associated with an increased risk of complications during and after the procedure, which requires compliance with the risk/benefit principle for the patient.

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Determination of the degree of stenosis and variants of coronary artery disease

Coronary artery stenosis is divided into local and diffuse (extended), uncomplicated (with smooth, even contours) and complicated (with uneven, irregular, undermined contours, leakage of coronary artery stenosis into plaque ulceration sites, parietal thrombi). Uncomplicated stenosis usually occurs with a stable course of the disease, complicated - in almost 80% of cases, occur in patients with unstable angina, ACS.

Hemodypamic significant, i.e. limiting coronary blood flow, is considered to be a narrowing of the vessel diameter by 50% or more (but this corresponds to 75% of the area). However, stenoses of less than 50% (the so-called non-obstructive, non-stenotic coronary atherosclerosis) can be prognostically unfavorable in the case of plaque rupture, formation of a mural thrombus with the development of coronary circulation instability and AMI. Occlusions - complete overlap, blockage of the vessel by morphological structure - can be cone-shaped (slow progression of narrowing followed by complete closure of the vessel, sometimes even without myocardial infarction) and with a sharp rupture of the vessel (thrombotic occlusion, most often with AMI).

There are various options for quantitative assessment of the extent and severity of coronary atherosclerosis. In practice, a simpler classification is more often used, considering the three main arteries (LA, OA and RCA) as the main ones and distinguishing between one-, two- or three-vessel coronary lesions. The lesion of the left coronary trunk is indicated separately. Proximal significant stenosis of the LCA and OA can be considered equivalent to the lesion of the left coronary trunk. Large branches of the three main coronary arteries (intermediary, diagonal, obtuse marginal, posterolateral and posterodescendant) are also taken into account when assessing the severity of the lesion and, like the main ones, can be subject to endovascular treatment (TBCA, stenting) or bypass.

Polypositional contrasting of arteries is important (at least 5 projections of the LCA and 3 of the RCA). It is necessary to exclude the overlap of branches on the stenotic section of the vessel being examined. This allows one to exclude underestimation of the degree of narrowing in the case of an eccentric plaque location. This should be remembered in standard analysis of angiograms.

Selective contrasting of venous aortocoronary and aortoarterial (internal thoracic artery and gastroepiploic artery) bypasses is often included in the plan of coronary angiography in patients after CABG to assess the patency and functioning of the bypasses. For venous bypasses starting on the anterior wall of the aorta approximately 5 cm above the RCA orifice, coronary catheters JR-4 and modified AR-2 are used, for the internal thoracic artery - JR or IM, for the gastroepiploic - a Cobra catheter.

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Complications of coronary angiography

The mortality rate for coronary angiography in large clinics is less than 0.1%. Serious complications such as myocardial infarction, stroke, severe arrhythmia and vessel damage occur in less than 2% of cases. There are 6 groups of patients who have an increased risk of serious complications:

• children and people over 65 years of age, with older women having a higher risk than older men;
• patients with angina pectoris FC IV, their risk is higher than in patients with angina pectoris FC I and II;
• patients with damage to the left coronary artery trunk are 10 times more likely to develop complications compared to patients with damage to 1-2 coronary arteries;
• patients with valvular heart defects;
• patients with left ventricular failure and LVEF < 30-35%;
• patients with various non-cardiac pathologies (renal failure, diabetes, cerebrovascular pathology, pulmonary diseases).

In 2 large studies of patients undergoing catheterization and coronary angiography, mortality was 0.1-0.14%, myocardial infarction 0.06-0.07%, cerebral ischemia or neurologic complications 0.07-0.14%, reactions to RCA 0.23%, and local complications at the femoral artery puncture site 0.46%. In patients using the brachial and axillary arteries, the percentage of complications was slightly higher.

The number of fatal outcomes increases in patients with damage to the left coronary artery trunk (0.55%), with severe heart failure (0.3%). Various rhythm disturbances - extrasystole, ventricular tachycardia, ventricular fibrillation, blockades - may occur in 0.4-0.7% of cases. Vasovagal reactions occur, according to our data, in 1-2% of cases. This is expressed in a decrease in blood pressure and associated cerebral hypoperfusion, bradycardia, pale skin, cold sweat. The development of these phenomena is determined by the patient's anxiety, reaction to pain stimuli during arterial puncture and stimulation of chemo- and mechaporeceptors of the ventricles. As a rule, it is sufficient to use ammonia, raise the legs or the foot end of the table, less often intravenous administration of atropine, mesaton is required.

Local complications occur, according to our data, in 0.5-5% of cases with different vascular accesses and consist of a hematoma at the puncture site, infiltrate, and false aneurysm.

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Congenital anomalies of coronary circulation

Coronary arteriovenous fistulas are a fairly rare pathology consisting of a connection between a coronary artery and any cavity of the heart (most often the right atrium or ventricle). The blood flow is usually small, and myocardial blood flow is not affected. 50% of such patients have no symptoms, while the other half may develop symptoms of myocardial ischemia, heart failure, bacterial endocarditis, and rarely pulmonary hypertension. Fistulas from the RCA and its branches are more common than fistulas of the LAD and OA.

Blood discharge into the right ventricle is observed in 41% of fistulas, into the right atrium in 26%, into the pulmonary artery in 17%, into the left ventricle in 3% of cases, and into the superior vena cava in 1%.

If the fistula originates from the proximal part of the coronary artery, the origin can be determined using echocardiography. The best method for diagnosing this pathology is CGA.

The origin of the LCA from the pulmonary artery trunk is also a rare pathology. This anomaly manifests itself in the first months of life with heart failure and myocardial ischemia. In this case, the general perfusion of the myocardium through the LCA ceases and is carried out only due to the RCA, and can be sufficient provided that collateral blood flow from the RCA to the LCA develops.

Typically, such patients develop MI in the first 6 months of life, which subsequently leads to death in the first year of life. Only 10-25% of them survive without surgical treatment until childhood or adolescence. During this time, they develop persistent myocardial ischemia, mitral regurgitation, cardiomegaly, and heart failure.

When contrasting the ascending aorta, only the RCA can be seen branching off from the aorta. In later frames, the RCA and OA can be seen filling up along the collaterals with contrast discharge into the pulmonary trunk. One of the methods of treating adult patients with abnormal branching of the LCA from the pulmonary trunk is the application of a venous shunt to the LCA. The outcome of such an operation and the prognosis largely depend on the degree of myocardial damage. In very rare cases, the RCA, and not the LCA, branches off from the pulmonary artery.

Also rarely observed are such anomalies as the origin of the LCA from the RCA and the OA from the RCA or near the orifice of the RCA.

A recent publication indicates the percentage of occurrence of some anomalies of the origin of the coronary arteries: origin of the LCA and OA from separate orifices - 0.5%, the origin of the OA from the right sinus of Valsalva - 0.5%. Origin of the RCA orifice from the ascending aorta above the right sinus of Valsalva - 0.2%, and from the left coronary sinus - 0.1%, arteriovenous fistula - 0.1%, origin of the LCA trunk from the right coronary sinus of the aorta - 0.02%.

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Collateral blood flow

In a normal heart with intact coronary arteries, collaterals (small anastomotic branches connecting large coronary arteries) are not visible on CAG because they are collapsed. When an obstructive lesion of one artery is present, a pressure gradient is created between the distal portion of the hypoperfused vessel and the normally functioning vessel, causing the anastomotic channels to open and become angiographically visible. It is not entirely clear why some patients develop effectively functioning collaterals while others do not. The existence of collateral blood flow bypassing the obstructed artery protects the area of myocardial hypoperfusion. Collaterals usually become visible when the vessel is narrowed by more than 90% or occluded. In one study of patients with AMI and ISA occlusion, coronary angiography for the first time 6 hours after AMI revealed collaterals only in 50% of cases, and CAG after 24 hours after AMI - in almost all cases. This confirmed that collateralization after vessel occlusion develops quite quickly. Another factor in the development of collateral blood flow is the state of the artery that will give collaterals.

Collateral intersystemic and intrasystemic blood flow plays a significant role in stenotic lesions of the coronary bed. In patients with complete occlusion of the vessel, regional LV contractility is better in those ventricular segments supplied by collateral blood flow than in those without collateralization. In patients with AMI without previous TLT, emergency CAG showed that individuals with adequately developed collaterals had lower LV EDP, higher CI and LVEF, and a lower percentage of myocardial asynergy than those without collaterals. During TBCA, balloon inflation at the site of arterial stenosis caused a less pronounced pain response and a change in the ST segment on the ECG in those patients with well-developed collaterals compared to those with poorly developed ones.

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Errors in coronary angiography

Frame-by-frame assessment, multi-projection imaging of the vessel with the definition of all proximal, middle and distal segments of the artery and its branches, good quality angiograms, and the experienced eye of a specialist help to avoid errors in conducting and interpreting CAG data.

Interpretation of coronary angiograms is complicated by insufficiently clear contrast of the coronary arteries. Normal, unchanged coronary arteries have smooth contours on coronary angiography, with free passage of contrast agent, good filling of the distal bed and absence of blurring and irregularity of contours. For good visualization of all segments of the artery, there should be good filling of the vascular bed with contrast, which is possible with tight filling of the artery by manual introduction of the RCA. Filling of the vessel is often poor when using catheters with a smaller internal diameter (4-5 F), which are used in transradial coronary angiography. Inadequate filling of the coronary artery with contrast may lead to a conclusion about an ostial lesion, irregularity of contours, or a mural thrombus.

Superselective deep catheterization of the left coronary artery, especially in patients with a short trunk, with the introduction of a contrast agent into the left coronary artery may erroneously indicate occlusion of the left coronary artery. Other causes of insufficiently tight filling with a contrast agent may be poor semiselective cannulation of the artery orifice (it is necessary to select a catheter corresponding to the coronary anatomy), increased coronary blood flow in myocardial hypertrophy (arterial hypertension, hypertrophic cardiomyopathy, aortic insufficiency), or an excessively wide venous aortocoronary bypass graft.

Intravascular ultrasound and determination of the pressure gradient in stenosis help in diagnostically difficult cases when assessing the significance of vessel narrowing.

Unrecognized occlusions of branches of large coronary arteries can be determined only in late angiography frames when the distal segments of the occluded branch are filled with collaterals.

Superposition of large branches of the LCA in the left and right oblique projections sometimes complicates visualization of stenoses or occlusions of these vessels. Using caudal and cranial projections helps to avoid diagnostic errors. The first septal branch of the LCA, when the LCA itself is occluded immediately after its origin, is sometimes mistaken for the LCA itself, especially since this branch expands to create collateral blood flow to the distal LCA.

"Muscular bridges" - systolic compression of the coronary artery, when its epicardial portion "dives" into the myocardium; manifested by a normal vessel diameter in diastole and narrowing of a short section of the artery running under the myocardium in systole. Most often, these phenomena are observed in the LAD basin. Although coronary blood supply is mainly carried out in the diastolic phase, cases of myocardial ischemia, angina pectoris and MI are sometimes described as a result of pronounced systolic compression along the "muscular bridge". There are also paroxysms of atrioventricular block, episodes of ventricular tachycardia during exercise or sudden death. Effective therapy for these conditions includes the use of beta-blockers and, in very rare cases, surgical treatment.

Cardiac probing and catheterization, coronary angiography and ventriculography retain their high information content, accuracy and reliability in the diagnosis and treatment of various forms of cardiovascular diseases and continue to be the “gold standard” in determining the treatment tactics for various pathological conditions of the heart and blood vessels.

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