RU2368318C1 - Method of diagnostics of paradoxical embolism in case of cryptogenic ischemic stroke - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medicine, namely to neurology, cardiology and ultrasonic diagnostics. Suspension of air microbubbles obtained by mixing 9 ml of physiological solution of sodium chloride and 1 ml of sterile air is introduced into patient intravenously. Transthoracal echocardiography is carried out at the background of Valsalva test. Period of time from the moment when contrast appears in right auricle till the moment of air bubbles visualisation in left auricle is marked, place through which contrast gets into left auricle - either through interatrial septum or through pulmonary vein orifice - is registered. If during first 5 seconds after filling of right auricle appearance of contrast coming through interatrial septum is registered in left auricle, paradoxial embolism with source in open oval window is diagnosed. If bubble visualisation takes place in later period of time and fact of their penetration into left auricle from pulmonary vein orifice is registered, paradoxial embolism with source in intrapulmonary arterial-venous communications in form of pulmonary bypass is diagnosed.

EFFECT: method allows to increase diagnostics accuracy which is achieved due to application of transthoracal echocardiography with contrast.

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Description

The invention relates to medicine, in particular, to neurology, cardiology and ultrasound diagnostics.

Vascular diseases of the brain due to the high prevalence and severe consequences for the health of the population represent a major medical and social problem (Suslina Z.A., Varakin Yu.Ya., Vereshchagin N.V. Vascular diseases of the brain. M .: Medpress-inform , 2006). Past stroke significantly increases the risk of developing a second stroke. Unfortunately, at present, relapses of stroke account for about a quarter of acute cerebrovascular accidents, exceeding the stroke rate by 15 times in the general population of people of the same age and gender, which probably reflects the failure of secondary prevention (Stroke. Principles of diagnosis, treatment and prophylaxis.Edited by N.V. Vereshchagin, M.A.Piradov, Z.A.Suslina. - M .: Intermedika, 2002). In most cases, a repeated cerebral event is due to the same circumstance and develops according to the same mechanism as the first, therefore, timely recognition of the pathogenetic subtype of ischemic stroke and verification of its immediate cause is the key to the success of secondary prevention.

In recent years, researchers have been increasingly interested in paradoxical cerebral embolism (PE), which is most often mentioned in connection with cryptogenic ischemic stroke.

Detecting the possibility of PE in the presence of other obvious causes of a stroke allows reclassifying a cryptogenic stroke to cardioembolic and deciding on the principles of secondary prevention (conservative or surgical).

It is known that right-left ("paradoxical") shunting is provided by intracardiac or intrapulmonary arteriovenous communications. The main intracardiac way of PE implementation is considered in adults to be an open oval window (000), which is a valve message between the atria, which ensures the passage of arterial blood into the left atrium from the right at the embryonic period, bypassing the non-functioning lung vessels. According to various researchers, LLC is detected in 27-35% of the population. Moreover, in individuals under 55 years of age with cryptogenic stroke, LLC is found in 46-66% of cases, which determines the relevance of the problem being studied (Belokon N.A., Podzolkov V.P. Congenital heart diseases. M., Medicine, 1990).

As another way of PE implementation, intrapulmonary arteriovenous communications are considered. The latter are determined by the presence of a pulmonary shunt (LS), designed to discharge part of the venous blood with a sharp increase in pressure in the pulmonary artery (Shurygin I.A. Respiratory monitoring: pulse oximetry, capnography, oximetry. M .: BINOM, 2000).

In addition, defects of the interventricular septum, common atrioventricular canal, and open ductus arteriosus can act as prerequisites for PE. However, these defects cause a powerful flow from the left ventricle to the right, therefore, the right-left shunt and PE are rare and are considered as casuistry.

The increase in interest in PE as a risk factor for cryptogenic strokes is associated with the development of various instrumental diagnostic methods that could, with maximum accuracy and reliability, reveal either the very variant of the structure of the interatrial septum or readiness for PE.

It is important to note that LLC and LS are related to low-symptom subclinical abnormalities, which accounts for the complexity of their timely identification. Cardiac catheterization and radiopaque ventriculography today are more of a historical interest, taking into account modern technical requirements for the diagnostic procedure: non- or minimally invasive and safe. Computed or magnetic resonance imaging of the heart or lungs in this respect is preferable, but they are characterized by low sensitivity, as well as economic inexpediency, given the high cost of these studies.

Among the methods for diagnosing PE variants, methods using transthoracic (TTE) and transesophageal (TEE) echocardiography meet modern requirements. The standard TFE is the easiest to use, however, the inability to detail the structure of the atria does not allow LLC to be detected even despite the use of color Doppler coding.

Closest to the proposed technical solution is a method for diagnosing PE in cryptogenic ischemic stroke, according to which the patient is injected intravenously with a suspension of air microbubbles obtained by mixing 9 ml of physiological sodium chloride solution and 1 ml of sterile air, against which transesophageal echocardiography (TEE) is performed, and in detecting early interatrial discharge, preconditions for PE are diagnosed (Rahmatullah AF, Rahko PS, Stein 1H. Transesophageal echocardiography for the evaluation and management of patients with cerebral ischemia. Clin. Cardiol. 1999; 22: 391-396). However, the use of TEE is technically much more complicated and more expensive than transthoracic echocardiography (TTE), since it requires a special expensive ultrasound transducer and trained medical staff. In addition, using this method, it is impossible to detect LB, i.e. it is impossible to differentiate the source of pathological central venous arterial bypass grafting.

The technical effect of the invention is to increase the accuracy of diagnosis of PE, which allows to identify the probability of PE and its cause in the early stages of identifying the mechanism of development of ischemic stroke.

It is achieved by the fact that a suspension of microbubbles of air obtained by mixing 9 ml of physiological solution of sodium chloride and 1 ml of sterile air is injected intravenously to the patient, against which transthoracic echocardiography is performed. At the same time, the time interval from the moment the contrast appears in the right atrium to the moment of visualization of air bubbles in the left atrium and the place through which the contrast enters the left atrium through the interatrial septum or through the mouth of the pulmonary veins is recorded. If during the first 5 seconds after filling the right atrium, the appearance of contrast entering through the atrial septum in the left atrium is detected, then PE with a source in an open oval window is diagnosed. If the visualization of the vesicles occurs at a later period of time and the fact of their penetration into the left atrium from the mouth of the pulmonary veins is noted, then PE is diagnosed with a source in the pulmonary arteriovenous communications in the form of a pulmonary shunt.

40 patients with ischemic stroke were examined, of which 23 (57%) were men and 17 (43%) were women. The age of patients ranged from 15 to 75 years, the average age was 45.5 ± 16.6 years.

The method was carried out as follows. For patients with ischemic stroke in order to detect the prerequisites for PE, a contrast TFE was performed. The contrast technique was carried out as follows.

A catheter was inserted into the elbow vein, to which a tee with 2 fixed syringes of 20 ml each was attached using a flexible polymer tube. In the first syringe, 9 ml of physiological saline was collected, in the second - 1 ml of air. Additionally, 0.5 ml of the patient’s autologous blood was taken into the first syringe. After that, using a special stub, access to the vein was blocked and access to another syringe was opened. Using pistons, the contents of the two syringes were mixed vigorously for 15-20 seconds to form a contrast with microbubbles of air, and one of the syringes was filled with them. Then the intravenous access was opened, and the prepared contrast was introduced for 4-5 seconds. Then, a second procedure was carried out using the Valsalva maneuver, which increases pressure in the right heart and the pulmonary artery system and more fully opens the existing right-left shunt. After 5 seconds from the beginning of the administration of the contrast medium, the patient took a deep breath and strained for 10 seconds while maintaining a certain pressure equal to 40 mmHg, controlled by a manometer.

The appearance of contrast in the left atrium during the first 5 seconds after filling the right atrium was considered the diagnostic criterion for the LLC. When visualizing vesicles in a later period, LS was considered the cause of the discharge. The degree of severity of the right-left shunt was estimated according to the gradation we proposed, taking into account the number of vesicles that appeared in the left parts of the heart: the minimum shunt was up to 10 vesicles, the small one was 10-20 vesicles, the moderate one was a lot of individual uncountable vesicles, the large one was merged into a common echo contrast.

According to the TFE with contrast at rest, an early (first 5 sec) discharge from the right to the left atrium through the interatrial septum was visualized in 27 (90%), and during the Valsalva test, in 29 (97%) patients (Table 1). In total, all 30 (100%) patients had an early discharge of contrast from the right to the left atrium.

Table 1 The results of the TFE with contrasting to identify signs of LLC Conditions for the diagnostic method The number of patients with early discharge,% TTE (n = 30) Peace 27 (90%) Valsalva Test 29 (97%)

In all 30 patients who have, according to the contrast CTF, an early discharge through the interatrial septum, using the TEEC an LLC was identified with a size of 2.7 mm (1; 5). No other cardiac disorders associated with the possibility of PE were found. When assessing the functional size of the shunt, according to the TFE, in 6 (20%) patients the discharge was minimal, in 10 (33%) - small, in 9 (30%) - moderate, in 5 (17%) patients - large (table .2). When TEE revealed LLC appropriate sizes: from 1.8 ± 0.7 mm to 3.8 ± 0.6 mm (table 2).

table 2 Functional size of the interatrial shunt at early discharge according to the CTF data in comparison with the results of the TEEC Shunt size according to CTE and TEE (n = number of patients) TTE (n = 30) TEE (n = 30) Minimum (n = 6) 1.8 ± 0.7 mm Small (n = 10) 2.5 ± 0.8 mm Moderate (n = 9) 2.9 ± 1.2 mm * Large (n = 5) 3.8 ± 0.6 mm ** # Note.
* - p = 0.06;
** - p <0.01 when comparing LLC sizes with minimal discharge;
# - p <0.01 when comparing LLC sizes with a small reset.

Of the remaining 10 patients, in 7 (70%) patients, according to the TFE with contrast, discharge into the left atrium at rest was late in nature and was realized through the mouth of the pulmonary veins. Moreover, in 4 (57%) patients the discharge was minimal, in 3 (43%) patients - small. During the Valsalva test, no additional changes occurred. A positive test could be due to the presence of HL with venous-arterial discharge. According to the TEE, in all patients, including those with a late shunt, the oval window was closed, and there were no other signs of interatrial communication.

An example implementation of the method

Example 1: Patient M., 59 years old, suffered a repeated ischemic disturbance of cerebral circulation in the basin of the left middle cerebral artery. The cause of the stroke has not been established. After the first stroke, he took aspirin. With contrast TFE, both at rest and during the Valsalva test, an early discharge from the right to the left atrium was revealed in the form of microbubbles merging into the general echocontrast, characterizing the large atrial shunt, on the basis of which LLC was diagnosed. When TEE the diagnosis is confirmed, found LLC with a diameter of 5 mm. Based on the proposed method of the invention, the pathogenetic mechanism of stroke is defined as a paradoxical embolism.

Example 2: Patient K., 29 years old, suffered an ischemic disturbance of cerebral circulation in the vertebral-basilar system. The cause of the stroke has not been established. Among concomitant diseases there was thrombophlebitis of deep veins of the legs. With contrast TFE, both at rest and during the Valsalva test, an early discharge from the right to the left atrium was revealed in the form of 10-15 individual microbubbles characterizing the shunt as small, on the basis of which LLC was diagnosed. When TEE the diagnosis is confirmed, LLC with a diameter of 2 mm was found. Based on the proposed method of the invention, the pathogenetic mechanism of stroke is defined as a paradoxical embolism.

Example 3: Patient B., 53 years old, suffered an acute ischemic disturbance of cerebral circulation in the pool of the right middle cerebral artery. The cause of the stroke has not been established. With contrast TFE, both at rest and during the Valsalva test, a late discharge into the left atrium from the pulmonary veins was revealed in the form of 1-2 separate microbubbles, which is typical for minimal LH. When TEE interchamber messages or other violations are not detected. Based on the proposed method of the invention, the pathogenetic mechanism of stroke is defined as a paradoxical embolism in the presence of LV.

Thus, in comparison with the prototype method, it is possible to more accurately and cost-effectively diagnose patients with LLC and LS by the method of contrast TFE with the calculation of the amount of contrast and the time of its appearance in the left heart. The use of a standard minimally invasive inexpensive technique for establishing the existence of a central venous-arterial discharge according to standard conditions allows us to identify patients with PE and determine the leading pathogenetic mechanism of stroke.

The proposed method for the diagnosis of PE variants with TFE with contrast is highly sensitive and allows patients with cryptogenic stroke to detect the presence of pathological central venous arterial bypass grafting and to differentiate its source. With LLC, the discharge is of an early nature, and its functional value is in accordance with the anatomical size of the oval hole. In LH, the discharge is late and, as a rule, minimal. Verification of the presence and source of relief allows you to clarify the mechanism of acute cerebrovascular accident and optimize the secondary prevention of ischemic stroke.

Claims (1)

A method for diagnosing paradoxical embolism in cryptogenic ischemic stroke, namely, that the patient is injected intravenously with a suspension of air microbubbles obtained by mixing 9 ml of physiological sodium chloride solution and 1 ml of sterile air, against the background of which echocardiography is carried out, characterized in that they carry out transthoracic echocardiography on the background of the Valsalva test, note the time interval from the moment the contrast appears in the right atrium to the moment of visualization of air bubbles in the left atrium and, register the place through which the contrast enters the left atrium - through the interatrial septum or through the mouth of the pulmonary veins, while if, during the first 5 seconds after filling the right atrium, the appearance of contrast entering through the interatrial septum in the left atrium is recorded, then a paradox is diagnosed embolism with a source in an open oval window, if the visualization of the vesicles occurs in a later period of time and the fact of their penetration into the left atrium from the mouth of the pulmonary veins is noted, then gnostiruyut paradoxical embolism with a source of intrapulmonary arteriovenous communications in the form of pulmonary shunt.