Radioisotope studies of the heart - Causes, symptoms and treatment. MF.

In the early 70s of the last century, new methods of research, called radioisotope( radionuclide) methods, appeared in doctors' practice. The principle of these studies is based on the introduction into the blood of the patient of substances that have a tendency to certain tissues, that is, the ability to attach and penetrate into certain cells. Also, these substances have the ability to radiate, which is captured by a gamma camera, processed on a computer and displayed on the monitor of the device in the form of a two-dimensional image in several projections. In cardiology, such methods include radioisotope ventriculography, radio angiocardiography, perfusion scintigraphy of the myocardium .The latter is used most often.

The general essence of the methods is as follows: a patient is injected into the blood with one of the preparations tropic to erythrocytes or myocardial cells and after a few minutes receives a picture of the passage of blood through the chambers of the heart or blood supply of the myocardium.

For example, in the diagnosis of acute myocardial infarction, the patient is administered intravenously a solution containing one of the following radioactive substances-technetium-99, thallium-201, indium, pyrophosphate labeled with technetium, potassium-43, etc. Due to binding of drug molecules to cell membranesheart muscle is a gradual accumulation of it in the cells themselves. Preparations produce radiation that is captured by the camera, processed, and a luminous image of the heart appears either on the computer or with accumulation defects( "cold spots") or with excessive accumulation( "hot spots").

With ischemia, heart attack or scar replacement of the myocardium( postinfarction cardiosclerosis), when the blood supply of the heart muscle is impaired, thallium can not penetrate from the bloodstream into the cells, which leads to the formation of cold spots. With the use of pyrophosphate, labeled with technetium, the appearance of hot spots is caused by the reverse, increased permeability of membranes of damaged cells for the preparation.

For heart diseases, cardiomyopathies, technetium is introduced, evenly distributed along the bloodstream and binding to red blood cells. The blood with the drug flows through the chambers of the heart, and its motion is recorded by a series of pictures that reveal the disturbance of the systolic and diastolic functions of the atria and ventricles, the reverse flow of blood to the atria or ventricles, and the mixing of blood in the presence of the patient such defects as atrial andinterventricular septa.

Despite the fact that some of the drugs are taken out of the cardiac muscle for a long time, that is, the technique makes it possible to conduct the test again after a few hours, and sometimes even every other day, this method of examination in modern institutions has not been widely used.

First, working with radioactive drugs requires great precautions.
Secondly, with the help of this technique, in combination with clinical symptoms, it is not possible to determine the true prescription of the process, since the absence of a drug in the affected area may indicate the development of acute myocardial infarction, and ischemia without infarction, and postinfarction cardiosclerosis, since blood flow disordersand the receipt of the drug in the cells occur with all these diseases.

Thirdly, in recent years, other diagnostic methods have been massively used, for example, ultrasound of the heart with dopplerography, which allows visualizing the movement of blood through the chambers of the heart, or coronary angiography, which can provide complete information on the patency of the coronary arteries. But still, radionuclide studies can be used in diagnostically unclear cases when other methods( ECG, ultrasound of the heart) fail to confirm or deny the diagnosis.

Indications for cardiac isotopic examination of

The examination can be indicated for diseases such as:
- acute myocardial infarction
- chronic ischemic heart disease
- hypertrophic and dilated cardiomyopathy
- defects of partitions between the atria or ventricles
- postinfarction myocardial aneurysms
-control of the effectiveness of thrombolytic therapy in myocardial infarction( a series of images before and after the administration of streptokinase, a drug that dissolves a thrombus, toory is causing blockage of the coronary arteries)

This method can be prescribed under the following conditions:
- pains in the heart area that are not controlled by nitroglycerin intake, not found confirmation on ECG
- pronounced dyspnea at rest or walking
- dry cough with episodes of suffocation
- episodes of "gurgling" coughwith asphyxiation, especially in prone position and at night - manifestations of "cardiac" asthma or pulmonary edema
- presence of heart murmurs diagnosed by a doctor with the help of auscultation
- carrying out stress tests( on a veloergometer) in patients with confirmationischemic heart disease with pre- and post-exercise studies to assess the infringement of myocardial infarction

Contraindications for radioisotope methods of research

To contraindications include febrile conditions, sepsis, allergy to radiopharmaceuticals established earlier, acute diseases and exacerbations of chronic diseases of other organs and systems.

Complications with this method do not develop. Despite the use of radioactive substances, the probability of a radiological hazard is negligible, since the total dose of irradiation obtained in the course of one study is less than in radiography or computed tomography, especially since most drugs are rapidly excreted from the body.

Decoding of the results of the radioisotope study of the heart

This is how the scintigraphy looks before and after physical exertion. In the upper row, the arrows indicate a perfusion defect, which is evidence of myocardial ischemia, provoked by a stress test.

After receiving the pictures, the data is analyzed using a computer. As a result of the study, you can find out whether the patient has myocardial ischemia, acute or transferred myocardial infarction, the presence of shunts( connections) between the chambers of the heart, which should not normally be, and also assess the functions of ejection of blood from the ventricles, such as stroke volume,ejection fraction, velocity of blood flow through the atria and ventricles. The indices are calculated by analyzing the amount of isotope passed through the blood in the chambers of the heart for each cardiac contraction and by the amount of the isotope absorbed by the cells of the heart muscle.

General practitioner Sazykina O.Yu.