Pulmonary embolism (PE): diagnosis

Diagnosis of pulmonary thromboembolism (PE) is carried out taking into account the following circumstances.

1. The sudden appearance of the above mentioned syndromes: acute respiratory failure, acute vascular insufficiency, acute pulmonary heart (with characteristic ECG manifestations), pain syndrome, cerebral, abdominal (painful stagnant liver), fever, further occurrence of lung infarction and pleural friction noise.
2. The presence of diseases listed in the article " The cause of pulmonary artery thromboembolism (PE) ", as well as predisposing factors.
3. The data of instrumental methods of research, which testify in favor of PE.
4. Presence of phlebothrombosis of the extremities:
   • soreness, local compaction, redness, local heat, swelling;
   • soreness and tightness of the calf muscles, asymmetric edema of the foot, shin (signs of deep venous thrombosis of the shins);
   • the detection of the asymmetry of the shin circumference (by 1 cm and more) and the thigh at a level of 15 cm above the patella (by 1.5 cm and more);
   • a positive Lovenberg test - the appearance of soreness of the gastrocnemius muscles at a pressure of the sphygmomanometer cuff in the range of 150-160 mm Hg. (normal morbidity appears at a pressure above 180 mm Hg);
   • the appearance of pain in the calf muscles with the rear folding of the foot (Homans' symptom);
   • detection of deep vein thrombosis of the lower limbs with the help of radioindication with fibrinogen, labeled 125I and ultrasonic biolocation;
   • the appearance of a cold zone on the thermogram.

The examination program for thromboembolism of the pulmonary artery

1. Common blood tests, urine tests.
2. Biochemical blood test: determination of the content of total protein, protein fractions, bilirubin, aminotransferases, total lactate dehydrogenase and its fractions, seromucoid, fibrin.
3. ECG in dynamics.
4. X-ray examination of the lungs.
5. Ventilation-perfusion scanning of the lungs.
6. Study of coagulogram and D-dimer in blood plasma.
7. Echocardiography.
8. Selective angiopulmonography.
9. Instrumental diagnosis of phlebothrombosis of the lower extremities.

Laboratory data

1. A general blood test - neutrophilic leukocytosis with a rod-shift shift, lymphopenia, relative monocytosis, an increase in ESR;
2. Biochemical blood test - increase in lactate dehydrogenase (especially the third fraction - LDH1); moderate hyperbilirubinemia is possible; increase in the content of seromucoid, haptoglobin, fibrin; hypercoagulation;
3. Immunological studies - the appearance of circulating complexes in the blood, which reflects the development of the immunological syndrome;
4. An increase in the content of D-dimer in the blood plasma, it is determined by the enzyme immunoassay (ELISA). The majority of patients with venous thrombosis have endogenous (spontaneous) fibrinolysis. It is completely inadequate to prevent further growth of thrombus, but causes splitting of individual clots of fibrin with the formation of D-dimers. The sensitivity of increasing the level of D-dimer in the diagnosis of proximal deep vein thrombosis or pulmonary embolism (PE) exceeds 90%. The normal level of D-dimer in blood plasma allows to predict with an accuracy of more than 90% the absence of proximal deep vein thrombosis or PE (in the absence of myocardial infarction, sepsis or any systemic diseases).

Instrumental studies with pulmonary embolism

Electrocardiography

In the acute stage (3 days - 1 week), deep teeth S1 Q III; deviation of the electric axis of the heart to the right; displacement of the transition zone to V4-V6, pointed high P teeth in II, III standard leads, as well as in avF, V1; rise of the ST segment upward in III, avR, V1-V2 and downward displacement in I, II, avL and V5-6, the teeth of T III, avF, V1-2 are reduced or slightly negative; high R in lead avR.

In subacute stage (1-3 weeks) the teeth of T II-III, avF, V1-3 gradually become negative.

The stage of reverse development (up to 1-3 months) is characterized by the gradual decrease and disappearance of negative T and the return of the ECG to the norm.

ECG changes in PE should be differentiated from ECG manifestations of myocardial infarction. Difference of ECG changes in PE from ECG changes in myocardial infarction:

• with lower diaphragmatic myocardial infarction pathological Q waves appear in the leads II, III, avF; with PAL pathological Q is not accompanied by the appearance of pathological QIII, the duration of the Q wave in the leads III, avF does not exceed 0.03 s; In the same leads, the terminal teeth R (r) are formed;
• changes in the ST segment and the T wave in the II lead with lower diaphragmatic myocardial infarction usually have the same pattern as in the leads III, avF; with PE, these changes in the II lead repeat the changes I of the lead;
• for myocardial infarction is not typical sudden turn of the electric axis of the heart to the right.

In some cases, pulmonary blockage of the right leg of the fasciculus develops in the PE (complete or incomplete), cardiac arrhythmias (atrial fibrillation and flutter, atrial and ventricular extrasystole) are possible.

Selective angiopulmonography

The method is the "gold standard" in the diagnosis of PE; characterized by the following angiopulmonographic features:

• an increase in the diameter of the pulmonary artery;
• complete (with occlusion of the main right or left branch of the pulmonary artery) or partial (with occlusion of segmental arteries) absence of contrasting of the lung vessels on the side of the lesion;
• "Diffuse" or "spotted" character of vascular contrast with multiple but not complete obturation of the lobar and segmental arteries;
• defects of filling in the lumen of the vessels in the presence of single parietal thrombi;
• deformation of the pulmonary pattern in the form of expansion and tortuosity of segmental and lobar vessels with multiple lesions of small branches.

Angiographic examination must necessarily include both sounding of the right heart, and retrograde or ikavografiyu, allowing you to clarify the sources of embolism, which most often are floating thrombi in the iliac and inferior vena cava.

Carrying out selective angiopulmonography provides the possibility of bringing thrombolytics to the site of occlusion of the vessel. Pulmonary arteriography is performed by puncture of the subclavian vein or internal jugular vein.

Chest X-ray

In the absence of a pulmonary infarction with pulmonary embolism (PE), X-ray methods may not be sufficiently informative. The most characteristic signs of pulmonary embolism (PE) are:

• bulging pulmonary cone (manifested by smoothing the waist of the heart or protruding the second arc behind the left contour) and widening the shadow of the heart to the right due to the right atrium;
• an increase in the contours of the pulmonary artery branch followed by a break in the course of the vessel (with massive thromboembolism of the pulmonary artery (PE));
• a sharp expansion of the root of the lung, its stump, deformation;
• local bleaching of the pulmonary field in a restricted area (a symptom of Westermarck);
• the appearance of discoid lung atelectasis on the affected side;
• high standing of the dome of the diaphragm (due to reflex wrinkling of the lung in response to embolism) on the side of the lesion;
• widening of the shadow of the superior hollow and unpaired veins; the superior hollow vein is considered enlarged with increasing distance between the line of spinous processes and the right mediastinal contour more than 3 cm;
• after the appearance of a lung infarct revealed infiltration of the lung tissue (sometimes in the form of a triangular shadow), more often located subpleural. A typical pattern of lung infarction is detected not earlier than the second day and only in 10% of patients.

Ventilation-perfusion scanning of the lungs

Ventilation-perfusion scanning of the lungs assumes a consistent perfusion and ventilation scan followed by a comparison of the results. For pulmonary embolism (PE) is characterized by a perfusion defect with preserved ventilation of the affected segments of the lung.

Perfusion scan of the lungs makes it possible to make a diagnosis of pulmonary embolism (PE) more reliable, to determine the volume of pulmonary embolism. The absence of defects in the perfusion of the lung tissue practically excludes the presence of pulmonary embolism (PE). PE on the scan is manifested by defects in isotope accumulation that correspond to the foci of oligemia, and it should be noted that similar scans are observed in other diseases that disrupt blood circulation in the lungs (emphysema, bronchiectasis, cysts, tumors). If after a lung scan the diagnosis of pulmonary embolism (PE) remains questionable or a significant violation of pulmonary perfusion is detected, contrast angiopulmonography is indicated.

Depending on the severity of pulmonary perfusion defects, high (> 80%), medium (20-79%) and low (<19%) pulmonary embolism (PE) are distinguished.

For perfusion lung scintigraphy, an intravenous injection of an albumin macroaggregate with a particle size of 50-100 μm, labeled with ^99m Tc, which does not fill the lumen of impassable pulmonary arteries and arterioles, is used.

With the help of ventilation scintigraphy, the localization, shape and size of non-ventilated areas of the lungs are determined. The patient inhales a mixture containing an inert radioactive gas, for example, ¹³³ Xe, ¹²⁷ Helium aerosol ^99m Tc.

Further, the results of perfusion and ventilation scintigraphy of the lungs are compared. For PE, the presence of a large segmental perfusion defect with normal ventilation values is specific.

The coincidence of segmental and larger defects of perfusion and ventilation can be observed in embolism, complicated by infarct-pneumonia.

Instrumental diagnosis of phlebothrombosis of lower extremities

Venous-occlusive plethysmography

The method is based on measuring the rate of change in the volume of the tibia after removal of external pressure that interrupted the venous outflow of blood. In case of violation of the patency of deep veins, the decrease in the volume of the tibia after the cuff opening will be slowed down.

Ultrasonic Doppler Flowmetry

The method is based on the acoustic evaluation and recording of the change in the frequency (length) of the ultrasonic wave emitted by the instrument in the direction of the vein. Violation of the permeability of the vein is manifested by a decrease in the rate of blood flow.

Radiometry with fibrinogen labeled with radioactive iodine

Above the thrombus area, increased radiation is detected due to the inclusion of an isotope into the thrombus together with the fibrin formed.

NMR-phlebography

It allows to reliably diagnose thrombosis of the veins of the tibia, pelvis, thighs.

Radiopaque phlebography

One of the most informative methods for detecting phlebothrombosis.

Pulmonary artery thromboembolism prognosis

With extensive PE, against a background of severe cardiovascular and respiratory system disorders, the mortality rate may exceed 25%. In the absence of severe disorders of these systems and the magnitude of pulmonary artery occlusion, not more than 50%, the outcome of the disease is favorable.

The probability of recurrence of PE in patients who did not receive anticoagulant therapy may be about 50%, and up to half of the relapses can lead to a fatal outcome. With timely properly conducted anticoagulant therapy, the frequency of recurrence of PE can be reduced to 5%, with deaths occurring in only 1/5 of patients.