Cardiac angiography and cardiac catheterization

Insertion of a catheter through an artery or vein into the heart cavity allows obtaining information on the pressure value, the nature of blood flow, the oxygen saturation of blood obtained from different chambers, and with the introduction of a contrast agent and subsequent cardioangiography, to evaluate morphological features. These studies allow obtaining highly accurate information on morphological and functional changes in the heart and solving various diagnostic, and increasingly therapeutic problems.

Special catheters with a diameter of 1.5-2.7 mm and a length of 80-125 cm are used for cardiac catheterization. To insert the catheter, the ulnar vein or femoral artery is punctured using special needles. There are various types of catheters with devices, such as inflatable balloons, which allow for therapeutic measures. A contrast agent (cardiotrast) is injected into the corresponding cavities of the heart through the catheters and a series of X-ray images are taken to clarify morphological changes.

Of particular practical importance is coronary arteriography, which is performed along with ventriculography in patients with ischemic heart disease. This makes it possible to assess and establish the presence, localization, severity and spread of coronary obstruction, as well as to assess its cause, i.e. the presence of atherosclerosis, thrombosis or spasm of the coronary arteries. Narrowing of the coronary artery by 50-75% of its lumen is of hemodynamic importance. Narrowing by 50% is of hemodynamic importance if its length is sufficiently large. Narrowing by 75% or more is significant even if it is present on a short section of the vessel. Coronary artery spasm usually occurs over a significant section and is subject to regression with the introduction of nitriglycerin. At present, during catheterization of the heart and coronary arteries, therapeutic measures for myocardial revascularization are simultaneously performed. In case of myocardial infarction, thrombolytic agents are administered intracoronarily.

In case of stenosing coronary sclerosis, transluminal coronary angioplasty or laser recanalization is performed. Coronary angioplasty consists of bringing a balloon to the narrowing area, which is inflated and thus the narrowed area is eliminated. Since repeated narrowing of the same area often occurs later, special plastic surgery is performed with the installation of an endoprosthesis, which is subsequently covered with intima.

Indications for coronary angiography are the need to clarify the genesis of pain in the heart and chest, refractory angina, the question of the choice of surgery (coronary angioplasty or coronary artery bypass graft). Coronary angiography is a relatively safe procedure, but complications are possible during its implementation, including the occurrence of a heart attack, dissection or rupture of a coronary vessel, the occurrence of thrombophlebitis, neurological disorders.

In case of heart defects, angiocardiography allows to clarify the anatomical features, including the size of the heart chambers, the presence of regurgitation or blood flow, the degree of narrowing of a particular opening.

The following parameters are normally determined in the heart cavities: pressure in the right ventricle is 15-30 mm Hg (systolic) and 0-8 mm Hg (diastolic), in the pulmonary artery - 5-30 mm Hg (systolic) and 3-12 mm Hg (diastolic), in the left atrium (as in the left ventricle) - 100-140 mm Hg (systolic) and 3-12 mm Hg (diastolic), in the aorta 100-140 mm Hg (systolic) and 60-80 mm Hg (diastolic). The oxygen saturation of blood obtained from different chambers of the heart varies (right atrium - 75%, right ventricle - 75%, pulmonary artery - 75%, left atrium - 95-99%). By measuring the pressure in the cavities of the heart and examining the oxygen saturation of blood when it is received from different chambers, it is possible to obtain significant additional information on the morphological and functional changes in the rheocardium. The pressure level also allows one to judge the contractile function of the right and left ventricles. The pulmonary capillary wedge pressure when a catheter is inserted into the pulmonary artery (as distally as possible) reflects the pressure in the left atrium and, in turn, characterizes the diastolic pressure in the left ventricle. With catheterization, it is possible to measure cardiac output (liters per minute) and cardiac index (liters per minute per 1 m2 of body surface) quite accurately ^. In this case, the introduction of fluid of a certain temperature (thermodilution) is used. A special sensor produces a curve that, with a horizontal line, forms an area proportional to the cardiac output. The presence of an intracardiac shunt is determined by measuring the oxygen saturation of the blood in the corresponding chambers of the heart.

Differences in blood oxygen saturation between the right atrium and the right ventricle may occur with a ventricular septal defect, which causes a left-to-right shunt. Taking into account the cardiac output, the amount of blood shunted can be calculated. In the presence of acquired and congenital defects, the question of the tactics and nature of surgical treatment is decided. Currently, in patients with certain defects, such as mitral stenosis, surgery is sometimes performed taking into account echocardiography data without catheterization. In patients with stenosis of the valve openings, valvuloplasty with a balloon is sometimes performed instead of surgery.

Long-term catheterization of the right heart and pulmonary artery using a floating balloon catheter (Swan-Ganz catheter) is performed for several hours to a day. In this case, pressure in the pulmonary artery and right atrium is monitored. Indications for such a study with a balloon catheter are the occurrence of cardiogenic or other shock, postoperative monitoring of patients with severe cardiac pathology, as well as patients who require correction of the amount of fluid and central hemodynamics. This study is important in the differential diagnosis of pulmonary edema of cardiac and non-cardiac origin, in rupture of the interventricular septum, papillary muscle rupture, acute myocardial infarction and assessment of hypotension that does not change with fluid administration.

During cardiac catheterization, it is also possible to perform endomyocardial biopsy of the left or right ventricle tissue. Reliable results can only be obtained if tissue from 5-6 different areas of the myocardium is examined. This intervention is important for diagnosing rejection of a transplanted heart. In addition, it can be used to diagnose congestive cardiomyopathy and differentiate it from myocarditis (inflammatory lesion of the myocardium), as well as to recognize infiltrative processes in the myocardium, such as hemochromatosis, amyloidosis.

Currently, there is a constant improvement in cardiac examination techniques using, for example, nuclear magnetic resonance, etc., in order to replace invasive intervention (cardiac catheterization) with non-invasive examination in many cases. An example of this is subtraction digital angiography, which involves the introduction of a contrast agent into a vein (without catheterization) followed by an X-ray examination, the data of which are computer processed, resulting in a conventional X-ray coronary angiogram and an assessment of the morphological state of the coronary arteries. Intracardiac cardioscopy is fundamentally possible and is already being performed, which also allows for a direct visual assessment of morphological changes in the heart.

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