Pulmonary embolism (TELA) - Diagnosis

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

1. The sudden appearance of the above syndromes: acute respiratory failure, acute vascular failure, acute pulmonary heart disease (with characteristic ECG manifestations), pain syndrome, cerebral, abdominal (painful congestive liver), increased body temperature, and later the appearance of pulmonary infarction and pleural friction rub.
2. The presence of diseases listed in the article “ Cause of pulmonary embolism (PE) ”, as well as predisposing factors.
3. Data from instrumental research methods indicating pulmonary embolism.
4. Presence of signs of phlebothrombosis of the extremities:
   • pain, local hardening, redness, local heat, swelling;
   • pain and tightness of the calf muscles, asymmetric swelling of the foot and lower leg (signs of deep venous thrombosis of the lower legs);
   • detection of asymmetry in the circumference of the lower leg (by 1 cm or more) and the thigh at a level of 15 cm above the patella (by 1.5 cm or more);
   • positive Lowenberg test - the appearance of pain in the calf muscles with pressure from the sphygmomanometer cuff in the range of 150-160 mm Hg (normally pain appears with pressure above 180 mm Hg);
   • the appearance of pain in the calf muscles when dorsiflexing the foot (Homans' symptom);
   • detection of deep vein thrombosis of the lower extremities using radioindication with fibrinogen labeled with 125I and ultrasound biolocation;
   • the appearance of a cold zone on the thermal image.

Pulmonary embolism screening program

1. General blood and urine tests.
2. Biochemical blood test: determination 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 diagnostics of phlebothrombosis of the lower extremities.

Laboratory data

1. Complete blood count: neutrophilic leukocytosis with band shift, lymphopenia, relative monocytosis, increased ESR;
2. Blood biochemistry - increased lactate dehydrogenase content (especially the third fraction - LDH1); moderate hyperbilirubinemia is possible; increased content of seromucoid, haptoglobin, fibrin; hypercoagulation;
3. Immunological studies - the appearance of circulating complexes in the blood is possible, which reflects the development of an immunological syndrome;
4. Increased D-dimer levels in blood plasma, determined using enzyme-linked immunosorbent assay (ELISA). Most patients with venous thrombosis have endogenous (spontaneous) fibrinolysis. It is completely insufficient to prevent further thrombus growth, but causes the breakdown of individual fibrin clots with the formation of D-dimers. The sensitivity of increased D-dimer levels in diagnosing proximal deep vein thrombosis or pulmonary embolism (PE) exceeds 90%. Normal D-dimer levels in blood plasma allow predicting with over 90% accuracy the absence of proximal deep vein thrombosis or PE (in the absence of myocardial infarction, sepsis or any systemic diseases).

Instrumental studies in pulmonary embolism

Electrocardiography

In the acute stage (3 days - 1 week) deep S1 Q III teeth are observed; deviation of the electrical 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; upward elevation of the ST segment in III, avR, V1-V2 and downward displacement in I, II, avL and V5-6, T III, avF, V1-2 teeth are reduced or slightly negative; high R tooth in lead avR.

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

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

ECG changes in PE must be differentiated from ECG manifestations of myocardial infarction. The difference between ECG changes in PE and ECG changes in myocardial infarction:

• in case of inferior diaphragmatic myocardial infarction, pathological Q waves appear in leads II, III, avF; in case of pulmonary embolism, pathological Q waves are not accompanied by the appearance of pathological QIII waves, the duration of the Q wave in leads III, avF does not exceed 0.03 s; terminal R waves (r) are formed in these same leads;
• changes in the ST segment and T wave in lead II in inferior diaphragmatic myocardial infarction usually have the same pattern as in leads III, avF; in PE, these changes in lead II repeat the changes in lead I;
• Myocardial infarction is not characterized by a sudden turn of the electrical axis of the heart to the right.

In some cases, pulmonary embolism causes right bundle branch block (complete or incomplete), and heart rhythm disturbances (atrial fibrillation and flutter, atrial and ventricular extrasystole) are possible.

Selective angiopulmonography

The method is the “gold standard” in the diagnosis of pulmonary embolism; the following angiopulmonographic signs are characteristic:

• 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 contrast enhancement of the lung vessels on the affected side;
• “blurred” or “spotted” character of vessel contrasting with multiple, but not complete obstruction of lobar and segmental arteries;
• filling defects in the lumen of blood vessels in the presence of isolated mural thrombi;
• deformation of the pulmonary pattern in the form of expansion and tortuosity of segmental and lobar vessels with multiple lesions of small branches.

An angiographic study must necessarily include both probing of the right heart chambers and retrograde iliac arteriography, which allows for clarification of the sources of embolism, which are most often floating thrombi in the iliac and inferior vena cava.

Selective angiopulmonography provides the ability to deliver thrombolytics to the site of vessel occlusion. Pulmonary arteriography is performed by puncturing the subclavian vein or internal jugular vein.

Chest X-ray

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

• bulging of the pulmonary cone (manifested by smoothing of the waist of the heart or protrusion of the second arc beyond the left contour) and expansion of the shadow of the heart to the right due to the right atrium;
• enlargement of the contours of the pulmonary artery branch with subsequent rupture of the vessel (in case of massive pulmonary embolism (PE));
• sharp expansion of the root of the lung, its truncation, deformation;
• local enlightenment of the lung field in a limited area (Westermarck's symptom);
• the appearance of discoid atelectasis of the lung on the affected side;
• high position of the dome of the diaphragm (due to reflex wrinkling of the lung in response to embolism) on the affected side;
• dilation of the shadow of the superior vena cava and azygos veins; the superior vena cava is considered dilated when the distance between the line of the spinous processes and the right contour of the mediastinum increases by more than 3 cm;
• After the onset of pulmonary infarction, infiltration of the lung tissue (sometimes in the form of a triangular shadow) is detected, often located subpleurally. The typical picture of pulmonary infarction is detected no earlier than the second day and only in 10% of patients.

Ventilation-perfusion scanning of the lungs

Ventilation-perfusion scanning of the lungs involves sequential perfusion and ventilation scanning with subsequent comparison of the results. Pulmonary embolism (PE) is characterized by the presence of a perfusion defect with preserved ventilation of the affected lung segments.

Perfusion scanning of the lungs allows to make the diagnosis of pulmonary embolism (PE) more reliable, to determine the volume of embolic damage to the pulmonary vessels. The absence of defects in the perfusion of the lung tissue practically excludes the presence of pulmonary embolism (PE). PE on the scanogram is manifested by defects in the accumulation of the isotope, corresponding to foci of oligemia, while it is necessary to take into account that similar scanograms are observed in other diseases that impair blood circulation in the lungs (emphysema, bronchiectasis, cysts, tumors). If after scanning the lungs the diagnosis of pulmonary embolism (PE) remains doubtful or a significant violation of pulmonary perfusion is revealed, contrast angiopulmonography is indicated.

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

For perfusion scintigraphy of the lungs, intravenous administration of albumin macroaggregate with particle sizes of 50-100 µm, labeled with ^99m Tc, which does not fill the lumen of obstructed pulmonary arteries and arterioles, is used.

Ventilation scintigraphy is used to determine the location, shape, and size of non-ventilated areas of the lungs. The patient inhales a mixture containing an inert radioactive gas, such as ¹³³ Xe, ^{127 Xe, or99m} Tc aerosol.

The results of perfusion and ventilation lung scintigraphy are then compared. The presence of a large segmental perfusion defect with normal ventilation indices is specific for PE.

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

Instrumental diagnostics of phlebothrombosis of the lower extremities

Venous occlusive plethysmography

The method is based on measuring the rate of change in the volume of the lower leg after the removal of external pressure that interrupted the venous outflow of blood. If the patency of the deep veins is impaired, the decrease in the volume of the lower leg after the cuff is released will be slower.

Ultrasound Doppler flowmetry

The method is based on acoustic assessment and recording of changes in the frequency (length) of the ultrasound wave emitted by the device in the direction of the vein being examined. Violation of the vein patency is manifested by a decrease in the blood flow velocity.

Radiometry with fibrinogen labeled with radioactive iodine

Increased radiation is recorded above the thrombus area due to the inclusion of the isotope in the thrombus along with the resulting fibrin.

NMR phlebography

Allows reliable diagnosis of thrombosis of the veins of the lower leg, pelvis, and thighs.

X-ray contrast phlebography

One of the most informative methods for detecting phlebothrombosis.

Prognosis for pulmonary embolism

In case of extensive pulmonary embolism against the background of pronounced disorders of the cardiovascular and respiratory systems, the mortality rate can exceed 25%. In the absence of pronounced disorders of these systems and the magnitude of pulmonary artery occlusion no more than 50%, the outcome of the disease is favorable.

The probability of recurrence of PE in patients who have not received anticoagulant therapy may be about 50%, and up to half of the recurrences may result in death. With timely and correctly administered anticoagulant therapy, the frequency of recurrence of PE may decrease to 5%, and deaths are observed in only 1/5 of patients.