Cardiac catheterization

Cardiac catheterization is performed by puncture and percutaneous insertion of the catheter into the vessel - peripheral vein (ulnar, subclavian, jugular, femoral) for the right heart or artery (shoulder, femoral, axillary, radial) for the left heart.

[1], [2], [3], [4], [5], [6]

Procedure for cardiac catheterization

In the case of a pronounced narrowing of the aortic valve or with its artificial prosthesis, when it is impossible to retrograde the catheter into the left ventricle, transseptal puncture of the atrial septum from the right atrium to the left and then to the left ventricle is used. The most commonly used access to the vessel according to the method of Seldinger (1953). After local anesthesia of the skin and subcutaneous tissue with 0.5-1% novocaine solution or 2% lidocaipa solution and small incision on the skin with a needle, a vein or an artery is punctured; when the blood appears from the proximal tip of the needle (pavilion) (you should try to puncture only the front wall of the vessel), a conductor is introduced through the needle, and the needle is removed and along the conductor, which, naturally, should be longer than the catheter, a catheter is inserted into the vessel. The catheter is advanced to the desired location under X-ray control. In the case of using Swan Hans type floating catheters with a balloon at the end, the position of the tip of the catheter is determined from the pressure curve. It is preferable to install a thin-walled introducer with a hemostatic valve and a side branch for rinsing into the vessel, and it is easy to introduce a catheter and replace it, if necessary, with another one. The catheter and introducer to prevent thrombus formation is washed with heparinized isotonic sodium chloride solution. Applying different types of catheters, it is possible to reach different parts of the heart and blood vessels, measure pressure in them, take blood samples for oximetry and other tests, inject RKV to determine anatomical parameters, constrictions, discharge of blood, etc.

If there is no fluoroscopic (fluoroscopic) control of the location of the catheter, catheters with a swollen floating balloon at the end are used which, with blood flow, can move to the right atrium, right ventricle, pulmonary artery and record the pressure in them. The pulmonary artery wedge pressure allows one to indirectly judge the condition of the left ventricle function, its end-diastolic pressure (CDD), since the left ventricular cortex has a mean pressure in the left atrium or pressure in the pulmonary capillaries. This is important for the control of therapy in cases of hypotension, CH, for example, with acute myocardial infarction. If the catheter has additional devices, it is possible to measure cardiac output by diluting the dye or thermodilution, recording intracavitary electrograms, and performing endocardial stimulation. The curves of intracavitary pressure with the help of a liquid pressure sensor such as Statham and ECG are recorded on a jet recorder or a computer with a possible printout on paper, and by changing them one can judge one or another pathology of the heart.

Measurement of cardiac output

It should be noted that there are no absolutely accurate methods for measuring cardiac output. When heart catheterization is most often used three options for determining cardiac output: the Fick method, the method of thermodilution (thermodilution), and the angiographic method.

Fick's method

It was suggested by Adolph Fick in 1870. The method is based on the assumption that at rest, the oxygen supply to the lungs is equal to the amount of oxygen consumed by the tissues, and the amount of blood ejected by the LV is equal to the volume of blood flowing through the lungs. It is necessary to take mixed venous blood, since the concentration of oxygen in the blood of the hollow veins and the coronary sinus differs significantly. Blood is taken from the pancreas or pulmonary artery, which is preferable. By the concentration of oxygen in the arterial (Ca) and venous (Sv) blood can be established arteriovenous difference but oxygen. Calculating the oxygen content absorbed during 1 min, it is possible to calculate the volume of blood flowing through the lungs at the same time interval, ie, the minute heart volume (MO):

Mo = Q / Ca-Sv (l / min),

Where Q - absorption of oxygen by the body (ml / min).

Knowing MO, you can calculate the cardiac index (SI). To do this, you must divide MO into the surface area of the patient's gel, which is calculated by its height and body weight. MO in an adult is normally 5-6 l / min, and SI is 2.8-3.5 l / min / m ².

[7], [8]

Thermodilution method

This method uses a chilled isotonic sodium chloride solution (5-10 ml), which is injected through the multilobar catheter into the right atrium, the tip of the catheter with the thermistor is located in the pulmonary artery. The curves are calibrated by briefly switching on a constant resistance, which gives the deviations of the recording device, corresponding to the temperature change determined for the thermistor. Most devices for thermodilution are equipped with analog computing devices. Modern equipment allows you to produce up to 3 measurements of blood MO for 1 minute and repeatedly repeat the study. Cardiac output, or MO, is determined by the following formula: MO = V (T1-T2) x 60 x 1.08 / S (l / min),

Where V is the volume of the entered indicator; T1 is the temperature of the blood; T2 - indicator temperature; S is the area under the dilution curve; 1.08 is a coefficient that depends on the specific density and heat capacity of blood and isotonic sodium chloride solution.

The advantages of thermodilution, as well as the need for catheterization only of the venous bed, make this method currently the most suitable for determining cardiac output in clinical practice.

Some technical aspects of the operation of the catheterization laboratory

The personnel of the catheterization angiographic laboratory includes the head, physicians, the operating average medical staff and radiotechnicians (radiologists), if film and x-ray photography is used. Vlaboratoriy, using only videofilms and computer image recording, X-ray labs are not needed. All employees of the laboratory should possess methods of cardiopulmonary resuscitation, for which in the X-ray surgery room there should be appropriate medications, a defibrillator, a device for electrical stimulation of the heart with a set of electrode catheters, a central oxygen supply and (preferably) an apparatus for artificial ventilation of the lungs.

Complex and risky diagnostic procedures and PCI (angioplasty, stenting, atherectomy, etc.) should preferably be carried out in clinics where there is a cardiosurgical team. According to the recommendation of the American College of Cardiology / American Heart Association, angioplasty and examination of patients with a high risk of complications, AMI can be performed by experienced, qualified specialists without having cardiosurgical support in the hospital if the patient can not be transported to a more suitable place without additional risk. In Europe and some other countries (in particular, and in Russia) are increasingly performing endovascular interventions without the presence of cardiac surgeons, since the need for an emergency cardiosurgical aid is currently extremely low. It is enough to agree with any nearby cardiovascular surgery clinic for emergency transfer to the patient in the event of peri-and post-procedural complications.

To maintain the form, skills and skills of operators in the laboratory, at least 300 procedures must be performed per year, and each doctor must do at least 150 diagnostic procedures per year. For catheterization and angiography, a high-resolution x-ray angiography system, a system for monitoring ECG and intravascular pressure, archiving and processing of angiographic images, a sterile instrumentation and various types of catheters (different types of catheters for coronary angiography are described below). The angiographic unit should be equipped with a prefix for kinangiographic or digital computer imaging and archiving, be able to obtain an image online, i.e., immediately with quantitative computer analysis of angiograms.

Changes in intracavity pressure curves

Intravascular pressure curves can vary with different pathological conditions. These changes serve to diagnose patients with various cardiac pathologies during examination.

To understand the causes of pressure changes in the heart cavities, it is necessary to have an idea of the temporal relationship between mechanical and electrical processes occurring during the cardiac cycle. The a-wave amplitude in the right atrium is higher than the amplitude of the y-wave. Excess of the y-wave over the a-wave in the pressure curve from the right atrium suggests a violation of atrial filling during ventricular systole, which happens when the tricuspid valve is deficient or a defect

When stenosis of the tricuspid valve, the pressure curve in the right atrium resembles that in the left atrium with stenosis of the mitral valve or constrictive pericarditis, when in the middle and the end of the diastole there appears a decrease and a plateau typical of elevated pressure during an early systole. The mean pressure in the left atrium corresponds quite accurately to the pulmonary artery wedge pressure and diastolic pressure in the pulmonary trunk. When the mitral valve is deficient without stenosis, there is a rapid decrease in pressure during the onset of systole (a decrease in the y-wave), and then gradually increasing it in late diastole (diastase). This reflects the achievement of a balance of pressure in the atrium and ventricle in the late phase of ventricular filling. In contrast, in patients with mitral stenosis, a decrease in the y-wave occurs slowly, while the pressure in the left atrium continues to decrease throughout the diastole, and there is no sign of diastasis of pulse pressure in the left atrium, since the atrioventricular pressure gradient persists. If mitral stenosis is accompanied by a normal sinus rhythm, the goat-wave in the left atrium persists and atrial contraction causes the creation of a large pressure gradient. In patients with isolated mitral regurgitation, the v-shaft is clearly expressed and has a vertical descending knee of the y-line.

On the left ventricular pressure curve, the CVD immediately precedes the onset of its isometric contraction and is located immediately after the a-wave in front of the c-wave of left atrial pressure. Left ventricular cystic fibroids may increase in the following cases: heart failure if the ventricle experiences a high load caused by excess blood flow, for example, with aortic or mitral insufficiency; hypertrophy of the left ventricle, accompanied by a decrease in its extensibility, elasticity and compliance; restrictive cardiomyopathy; constrictive pericarditis; cardiac tamponade caused by pericardial effusion.

With stenosis of the aortic valve, which is accompanied by a complicated outflow of blood from the left ventricle and an increase in the pressure in it compared to systolic pressure in the aorta, i.e., the appearance of a pressure gradient, the left ventricular pressure curve resembles a pressure curve during isometric contraction. Its outlines are more symmetrical, and the maximum pressure develops later than in healthy individuals. A similar picture is observed when recording pressure in the right ventricle in patients with pulmonary artery stenosis. Curves of blood pressure can also differ in patients with stenosis of the aortic aorta of various types. Thus, with valve stenosis, a slow and delayed increase in the wave of the arterial pulse is observed, and with hypertrophic cardiomyopathy the initial sharp increase in pressure is replaced by its rapid decrease and then by a secondary positive wave reflecting obstruction during systole.

[9], [10], [11]

Derived indices of intraventricular pressure

The rate of change / increase of the intra-radial pressure curve during the phase of isovolumic contraction is called the first derivative - dp / dt. Previously, it was used to assess the contractility of the ventricular myocardium. The value of dp / dt and the second derivative, dp / dt / p, are calculated from the intraventricular pressure curve using electronic and computer technology. The maximum values of these indicators are indexes of the rate of ventricular contraction and help to regain contractility and inotropic status of the heart. Unfortunately, a wide spread of these indicators in different categories of patients does not allow us to develop any averaged standards, but they are quite applicable in one patient with baseline data and against the use of drugs that improve the contractile function of the heart muscle.

Currently, having in the arsenal of patients' examination such methods as EchoCG in its various modifications, computer (CT), electron beam and magnetic resonance imaging (MRI), so important as before, these indicators for diagnosis of cardiac pathologies are not have.

[12], [13], [14], [15]

Complications of cardiac catheterization

Cardiac catheterization is relatively safe, however, like any invasive technique, it has a certain percentage of complications associated with both the intervention itself and the general condition of the patient. The use of more sophisticated and thin atraumatic catheters, low osmolar and / or nonionic RCVs, modern angiographic devices with computer image processing in real May time allowed for the invasion to significantly reduce the frequency of possible complications. For example, the lethality with cardiac catheterization in large angiographic laboratories does not exceed 0.1%. C. Rerine et al. Report a total mortality rate of 0.14%, in patients under 1 year of age it is 1.75%, in those over 60 years of age it is 0.25%, in single-vessel coronary lesion 0.03%, in tri-vessel 0 , 16%, and with lesion of the main LCA trunk - 0.86%. In heart failure, lethality also increases from the NUNA class: at I-II FK - 0.02%, III and IV FK - 0.12 and 0.67%, respectively. In some patients, the risk of serious complications is increased. These are patients with unstable and progressive angina, recent (less than 7 days) myocardial infarction, signs of pulmonary edema due to myocardial ischemia, circulatory failure III-IV FC, severe right ventricular failure, valvular heart disease (severe aortic stenosis and aortic regurgitation with pulse pressure more than 80 mm Hg), congenital heart diseases with pulmonary hypertension and right ventricular failure.

In a multivariate analysis, 58,332 patients with severe complications were severe congestive heart failure, hypertension, CLS, aortic and mitral valve diseases, renal failure, unstable angina and AMI in the first 24 hours, cardiomyopathies. In 80-year-old patients, the lethality with invasive diagnostic procedures is also increased to 0.8%, and the frequency of vascular complications at the puncture site reaches 5%.

[16], [17], [18], [19], [20]