RU2504331C1 - Method of radionuclide assessment of ischemia degree in case of acute thrombosis of main arteries of lower extremities in patients with bilateral atherosclerotic affection of arteries - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: invention relates to medicine, urgent vascular surgery, radionuclide diagnostics with assessment of blood supply of soft tissues, ischemia degree, identification of zones of aseptic muscular necrosis (AMN) in patients with acute thrombosis of main arteries of lower extremities. Three-phase scintigraphy with radiopharmaceutical preparation (RPP) 99Tc-pyrphotech is performed in order to visualise main blood flow in phase of main blood flow and detection of focuses of RPP hyperfixation or zones where RPP accumulation is absent in tissue (TP) and bone (BP) phases. Index of RPP washout (IW) from shin muscular tissue and index of ratio (IR) of RPP accumulation in muscle and accumulation in shin bone in BT are determined in zones of diffuse RPP distribution in muscles of shin of either extremity separately. IR equals ratio of average impulse count in shin muscle in TP (N,) to average count of impulses in muscle in BT (N): IR=C·C/N, where C is coefficient, taking into account 99Tc, decay, decay constant ?=0.00192 min, and correction to coercion of IR value to 180 min interval between tine of examination in TP and BP: C=e·180/t, where t is time in min between TP and BP. IR equals ratio of average impulse count in shin muscle in BP (N) to average impulse count in shin bone in BP (N): IR=N/N. Degree of ischemia is stated: I-IIA at IW=1.54±0.17, IR=0.68±0.04 and non-detection of AMN focuses and zones of blood supply absence; IIB - at IW=1.36±0.18, IR=0.88±0.06 and non-detection of and focuses and identification of blood supply absence in TP; IIC at IW=0.93±0.27, IR=0.93±0>14 or is not identified, detection of AMN and zones of absence of blood supply in TP; IIIA at IW=0.82±0.18, IR=0.93±0.04 or is not identified and detection of AMN focuses and zones of absence of blood supply in TP and BP.EFFECT: method makes it possible to determine level of arterial occlusion in said group of patients, ischemia degree, AMN zone, state of either extremity microcirculation to confirm and specify clinical diagnosis and optimise treatment tactics.2 ex, 1 tbl

Description

The invention relates to medicine, emergency vascular surgery, radionuclide diagnostics and can be used to assess blood supply to soft tissues, determine the degree of ischemia and identify areas of aseptic muscle necrosis in patients with acute thrombosis of the main arteries of the lower extremities to confirm and clarify the clinical diagnosis and optimize treatment tactics. The proposed method is based on the determination of quantitative indicators and a qualitative visual assessment of the obtained scintigrams, which provides objective information about the state of the main blood flow, microvasculature of the lower extremities and the degree of damage to soft tissues in ischemic conditions separately for each limb.

The urgency of the problem of diagnosis and treatment of patients with acute ischemia, despite the technical advances in surgical treatment and management of the postoperative period, remains one of the most difficult and least solved tasks of emergency vascular surgery. The mortality rate in acute ischemia ranges from 15 to 20%. Complications include bleeding requiring a blood transfusion and / or surgery, high amputations, fasciotomy, and renal failure. Even with the widespread use of the latest endovascular techniques, including thrombolytic therapy, most authors report 15-20% of amputations within 30 days (National guidelines for the management of patients with vascular arterial pathology. Part 1. Peripheral arteries. M., 2010), and with critical ischemia of the lower extremities against the background of chronic arterial insufficiency, perioperative mortality during reconstructive operations reaches 12% (critical ischemia of the lower extremities / I.P. Dudanov, V.N. Sidorov, M.Yu. aputin, A.V. Karpov // Diagnostic and treatment standards in the clinic of internal diseases Cardiovascular diseases: collection of scientific papers of the Russian scientific and practical conference / Bulletin of the Russian Academy of Medical Sciences (app.), St. Petersburg, 2007. - Volume 18. - No. 2. - S.53-55).

The main instrumental diagnostic methods for diseases of the main arteries of the lower extremities are ultrasound, duplex ultrasound, contrast angiography, CT and MR angiography. However, these methods have several limitations. So, ultrasound dopplerography and duplex ultrasound do not allow characterizing the anatomy of the arteries, have limited accuracy in the tortuous, calcified segments of the arteries, when visualizing the aortic-iliac segment (obesity, gas formation), vascular prostheses and when the pulse is “normalized” distal to stenosis. The limitations of this method also include high apparatus and operator dependence, subjectivity in the interpretation of images, low reproducibility of results (A. Karalkin et al. Scintigraphy possibilities in the diagnosis of chronic lower limb muscle ischemia / Actual problems of nuclear medicine and radiopharmaceuticals: collection of scientific. Tr. All-Russian Scientific and Practical Conf. / Dubna, 2004. - S.96-99). X-ray contrast studies (contrast angiography, CT angiography) are used with water-soluble iodine-containing contrast agents, but, despite the high information content, are unsafe for the patient, especially with renal dysfunction and allergies, have a reduced sensitivity to the tibial arteries and foot arteries and carry a large radiation load . MR angiography has limited accuracy in stenoses (stenosis may be overestimated), in the area of stents, it is contraindicated in the presence of metal structures in the patient’s body, with claustrophobia (G. Trufanov, “Radiation Diagnostics”, Volume 1, M., 2007. - S.29, 34, 39).

In addition to the above limitations, the above-mentioned methods of radiation diagnostics do not allow to objectively assess the state of the microvasculature of the ischemic limb and to identify the focus of muscle necrosis at an early stage of its formation.

It is possible to obtain complete information about the blood supply to tissues during acute occlusion of the main artery using the radionuclide method, in particular, three-phase limb scintigraphy with osteotropic radiopharmaceutical (RP) ^99m Tc-pirfotech, which is a phosphate complex that binds in the patient’s body with hydroxyapatite crystals and immature collagen intravenous administration. This radiopharmaceutical is included in healthy bone tissue, and in soft tissues it accumulates only with ischemia and necrosis due to increased capillary permeability, damage to cell membranes and active transport of calcium ions into the cell. In case of muscle necrosis with preserved blood flow in the area of damage, hyperfixation of radiopharmaceuticals with accumulation in the bone phase is noted. The zone of lack of blood supply to tissues is visualized as a defect in the accumulation of radiopharmaceuticals.

For many years, to assess the state of soft tissues in the soft tissue and bone phases, the relative accumulation coefficient (KOH) was used, the calculation of which is based on a comparison of the intensity of radiopharmaceutical accumulation in the affected and healthy (conditionally!) Muscle tissue of the contralateral zone of the opposite limb (Chernysheva O.A. , Mikhailov IP, Siluyanova AS The choice of the most informative radio diagnostic indicators of the degree of ischemia in acute thrombosis of the main arteries of the lower extremities. "Diagnostic and interventional radio ogiya "- Volume 5. - №2 - 2011. - S.471-472)..:

KOH = N _pore / N _zdor ,

where KOH is the coefficient of relative accumulation;

N _then - the average count of pulses in the zone of interest of the affected limb;

N _zdor - the average count of pulses in the zone of interest of a healthy limb.

This known method, which was the prototype of the claimed, has a significant limitation in ischemia against the background of bilateral atherosclerotic lesions of the great arteries, which is most common in patients with multifocal atherosclerosis.

Radionuclide research is carried out in 3 stages:

the first phase - the phase of the main blood flow - dynamic recording immediately after a bolus injection of 500 MBq ^99m Tc-pirfotecha (effective irradiation dose is 2.85 mSv) in the 60 frames mode of 1 sec / frame, the zone of interest is “terminal aorta - iliac arteries - femoral arteries - popliteal arteries ”(field of view of the detector);

the second phase - the blood supply phase (tissue) - recording in the static mode 300 sec / frame 10 min after the introduction, the zones of interest are “hip”, “lower leg”, “foot”;

the third phase - bone - recording in static mode 300 sec / frame 3 hours after the introduction, the zones of interest are “hip”, “lower leg”, “foot”.

The phase of the main blood flow (radionuclide aortoarteriography) allows you to determine the level of arterial occlusion and can be used if it is impossible to conduct contrast angiography. The following two phases characterize the state of the microvasculature of the lower extremities.

Based on the fact that the above known method for assessing ischemia of limb tissues is unacceptable for bilateral arterial damage, we proposed two new indicators calculated for soft lower leg tissues of each limb for objective assessment of the degree of ischemia in patients with acute thrombosis against atherosclerosis of the main arteries of both limbs separately: the excretion index (IV) and the ratio index (IS) in conjunction with two visual signs - the absence of blood supply to the limb segments and the hyperfixation zone and radiopharmaceutical, corresponding to aseptic muscle necrosis (this takes into account the increase in the accumulation of radiopharmaceutical in the area of hyperfixation in the bone phase compared with tissue). It should be noted that the most objective information was obtained when assessing the blood supply to the calf muscles, since the blood supply to the muscles on the hips is often compensated due to the anatomical features (the presence of a deep femoral artery), and it is not possible to isolate soft tissues in the bone phase on the feet.

The RFP excretion index (IV) from the calf muscle tissue was calculated as the ratio of the average count of pulses in the calf muscle in the tissue phase (N _mtf ) to the average count of pulses in the muscle in the bone phase (N _kf ):

IB = K · N _mtf / N _kf ,

where K is the coefficient taking into account the decay of ^99m Tc (half-life is 6.0058 hours, the decay constant is N _healthy λ = 0.00192 min ^-1 ) and the correction for bringing the value of the ionosphere to the interval of 3 hours (180 min) between the study time in tissue and bone phases, since it is not always possible to strictly observe the three-hour interval between the 2nd and 3rd phases of the study.

K = e ^{−λ · t} · 180 / t,

where t is the time interval in minutes between the tissue and bone phases of the study.

The ratio index (IP) of the accumulation of radiopharmaceuticals in the muscle and the accumulation in the leg bone in the bone phase was calculated as the ratio of the average count of impulses in the leg muscle in the bone phase (N _m ) to the average count of impulses in the leg leg in the bone phase (N _to ):

IC = N _m / N _to .

These two indices are calculated for each limb separately and, therefore, give a more objective assessment of the state of the microvasculature of tissues in patients with bilateral atherosclerotic lesion of the great vessels of the extremities compared with the known method comparing the affected and conditionally healthy limb.

To obtain the parameters of the norm, we examined 10 people. (20 lower extremities) without diseases of the main arteries. IV and IS with adequate blood supply to the legs, taking into account the decay of the radiopharmaceutical and corrections for the time of recording the bone phase, were 2.40 ± 0.17 and 0.50 ± 0.02, respectively.

To determine the compliance of scintigraphic and clinical data, we examined 60 patients with acute thrombosis of various localization (iliac, femoral artery, femoral-popliteal prosthesis, popliteal artery, aorto-femoral and femoral-tibial prosthesis) and clinical signs of acute ischemia of the lower extremities I-III degree classifications of I.I. Zatevakhin and chronic ischemia according to the classification of A.V. Pokrovsky. The clinical classification of the degrees of ischemia contains some subjective points, such as patient complaints and examination data.

When analyzing the results, it was noted that under conditions of impaired blood flow and existing limb ischemia, the IW decreases in proportion to the severity of the disease, and the IS increases, and the IV changes most clearly with the increase in ischemia, and the IS, starting from the IIB degree, does not change or changes slightly, which is associated with violation of bone blood flow in this stage of the disease. In acute grade I ischemia, the indicators were IV = 1.56 ± 0.17; IP = 0.68 ± 0.04; with ischemia IIA - 1.54 ± 0.11 and 0.70 ± 0.04, respectively; with ischemia IIB - 1.36 ± 0.18 and 0.88 ± 0.06; IIB - 0.93 ± 0.27 and 0.93 ± 0.14; IIIA - 0.82 ± 0.18 and 0.93 ± 0.04.

When analyzing the values of these indicators in patients with various clinical degrees of ischemia at the tibia level, a significant difference was observed in comparison with the norm (p <0.05), as well as between the groups: I and IIB, I and IIIA, IIA and IIB, IIA and IIIA, IIB and IIB.

Additional information indicative of circulatory decompensation was the presence of visual scintigraphic signs of soft tissue damage in the examined patients in the form of areas of lack of blood supply to limb segments that were detected in the affected limb starting from grade IIB ischemia, or necrosis sites starting from grade IIB. At I and IIA degrees of ischemia, there were no signs of a lack of blood supply, necrosis, and no significant differences in IV and IS were obtained, so these degrees were combined. At IIB degree, the zones of absence of radiopharmaceutical accumulation in the calf muscles and / or foot tissues in the tissue phase were visualized; in IIB, there was a lack of radiopharmaceutical accumulation in the limb segments in the tissue phase in combination with focal necrosis; with IIIA - lack of blood supply to the muscles of the leg and foot tissues in both the tissue and bone phases in combination with necrotic changes in areas with preserved blood flow. In case of muscle necrosis with the presence of blood flow in the lesion area, there was a local or extended hyperfixation of the radiopharmaceutical with an increase in KOH in the bone phase. With IIB degree, as a rule, a small area of necrosis was detected, and with IIIA, extended necrosis, which captures one or more muscle groups. Patients with a higher degree of ischemia had external signs of gangrene of the extremity, which did not raise doubts among angiosurgeons in determining the degree of ischemia, and were not considered in this work.

Scintigraphic criteria for ischemia by two quantitative indicators and two visual signs are presented in the table.

Table Assessment of the degree of lower limb ischemia by the radionuclide method. Degree of ischemia Willow IP Blood supply zones Foci of aseptic necrosis I-IIA 1.54 ± 0.17 0.68 ± 0.04 no no IIB 1.36 ± 0.18 0.88 ± 0.06 in tissue phase no IIB 0.93 ± 0.27 0.93 ± 0.14 (or not determined) in tissue phase there is IIIA 0.82 ± 0.18 0.93 ± 0.04 (or not determined) in tissue and bone phases there is

The method is as follows.

Three-phase scintigraphy with 99 ^m Tc-pirfotech is performed to visualize the main blood flow (in the first phase) and to identify foci of hyperfixation of the radiopharmaceutical (necrosis) or areas of lack of radiopharmaceutical accumulation (lack of blood supply) (in the second and third phases). Foci of necrosis, as in the known method, are calculated using KOH (coefficient of relative accumulation) and the growth of KOH is recorded in the bone phase compared with the tissue phase (if this is not, then these are just infiltrative changes). In the zones of diffuse distribution of radiopharmaceuticals in the muscles of the tibia of each limb, separately determine IV and IS. By the totality of changes (two indices + two visual signs), the degree of ischemia is established.

Achievable result. This method of radionuclide assessment of the degree of ischemia allows the examined patients with acute thrombosis of the main arteries of the lower extremities to determine the level of arterial occlusion, the state of the microvasculature of each limb separately, in particular, to clarify the degree of ischemia of each limb, identify areas of lack of blood supply and necrosis, and choose an adequate therapeutic tactic.

Example 1. Patient Sh., 63 years old, was admitted to the clinic 3 days after the onset of intense pain in the left lower limb. It was treated on an outpatient basis without effect, delivered via the NSR channel. Clinical diagnosis: Atherosclerosis. Right thigh-popliteal prosthesis thrombosis. Acute ischemia of the right lower limb, I degree. In the anamnesis - 3 years before admission, a resection of the aneurysm of the right popliteal artery was performed, a femoral-popliteal prosthesis was performed below the gap of the knee joint; 2 years before admission, a resection of the aneurysm of the left popliteal artery was performed, femoral-popliteal prosthesis below the gap of the knee joint. On examination: ripple on aa. tibialis posterior is absent on both sides, on a. dorsalis pedis is absent on the right. With UZDG: On the right - thrombosis of the femoral-popliteal shunt, occlusion of the superficial femoral, popliteal and posterior tibial arteries; on the left - the femoral-popliteal shunt we pass, hemodynamically insignificant stenosis of the distal anastomosis, occlusion of the superficial femoral, popliteal and posterior tibial arteries.

With scintigraphy: the main blood flow of the thighs and left lower leg is preserved, at the level of the right lower leg - collateral type. Tissue blood flow of the right lower limb is preserved throughout, visually moderately reduced on the foot, and the left lower limb is preserved at all levels. IV (excretion index) on the right = 1.61, IP (ratio index) on the right = 0.70 (both indices correspond to I-IIA art. Ischemia). IV on the left = 1.71, IP on the left = 0.64 (indicators are slightly better than on the right, but also correspond to I-IIA art. Ischemia). Zones of lack of blood supply and foci of muscle necrosis were not detected.

The patient underwent a course of anticoagulant, antiplatelet, vasodilator, rheological and angiotropic conservative therapy with a good effect.

In this case, the clinical and scintigraphic signs of ischemia I Art. coincided.

Example 2. Patient I., 56 years old, was admitted through the NSR channel with a diagnosis of thrombosis of the iliac-femoral shunt on the left, acute ischemia of the left lower limb, grade IIB. I turned for help 4 days after the onset of intense pain in the left foot at rest, noted a feeling of numbness and cooling of the foot. History — 8 months before admission, he underwent iliac-femoral prosthetics on the left, 2 months before admission — thrombectomy from the prosthesis, reconstruction of the distal anastomosis. On examination: the left foot is cool, pale, movements are limited, sensitivity is reduced, calf muscles are soft, slightly painful on palpation, a symptom of a “white spot” D = 3 s, S = 6 s, pulsation of the main arteries on the left is not detected, on the right - only in Scarp triangle, right lower limb normal color, warm. When ultrasound: atherosclerosis of the aorta and arteries of the lower extremities: stenosis of the terminal aorta; right: stenosis at all levels, occlusion of the superficial femoral artery; left: ileo-femoral thrombosis without restoration of blood flow in the distal canal. Angiography: occlusion of the right superficial femoral artery with restoration of blood flow in the popliteal artery and lower leg arteries; thrombosis of an aortic femoral shunt on the left without restoration of blood flow in the superficial femoral, deep femoral, popliteal, and lower leg arteries.

With scintigraphy: the main blood flow on the left is absent from the level of the iliac artery, on the right - from the level of the middle third of the femoral artery. Tissue blood flow in both thighs preserved; visually, there is no blood supply to the anterolateral group of the leg and foot muscles in the tissue phase with restoration in the bone phase on the left; the site of RFP hyperfixation with an increase in the bone phase in the medial muscle group of the left leg (local necrosis) is determined; on the right, blood supply is maintained at all levels. IV on the left = 0.79, IP is not determined (violation of blood supply to the bones of the leg); IW on the right = 1.52, IS on the right = 0.72. The condition of the muscles of the left tibia corresponds to acute ischemia of the IIB degree, the right to chronic ischemia of I-IIA.

Based on the data of instrumental diagnostic methods, including scintigraphy, the degree of ischemia of both limbs was clarified, the diagnosis was made: atherosclerosis. Thrombosis of the iliac-femoral prosthesis on the left, thrombosis of the distal bed. Acute ischemia of the left lower limb IIB Art. Occlusion of the right femoral artery. Chronic ischemia of the right lower limb IIA Art.

The patient has no conditions for performing reconstructive surgery. A course of angiotropic therapy without effect. The patient was transferred to the purulent surgery department.

This method of radionuclide assessment of the degree of ischemia allowed the examined patients with acute thrombosis of the main arteries of the lower extremities to clarify the degree of ischemia, to identify the area of aseptic necrosis (example 2), and to select an adequate therapeutic tactic.

Claims (1)

A method for radionuclide assessment of the degree of ischemia in acute thrombosis of the main arteries of the lower extremities in patients with bilateral atherosclerotic lesions of the arteries, which consists in performing three-phase scintigraphy with a radiopharmaceutical (RFP) 99 ^m TC-pyrotechnic to visualize the main blood flow in the phase of detection of main blood flow and Radiopharmaceutical or zones of lack of radiopharmaceutical accumulation in the tissue and bone phases, on the basis of the data obtained, the presence of zones of lack of blood supply and foci of ac optical necrosis, characterized in that in the zones of diffuse distribution of the radiopharmaceutical in the muscles of the lower leg of each limb, individually determine the index of excretion (II) of the radiopharmaceutical from the muscle tissue of the leg and the ratio of the accumulation of the radiopharmaceutical in the muscle and the accumulation in the leg bone in the bone phase, IV is calculated as the ratio of the average count of pulses in the leg muscle in the tissue phase (N _mtf ) to the average count of pulses in the muscle in the bone phase (N _kf ): _VI = K · N _mtf / N _kf , where K is the coefficient taking into account the decay of 99 ^m Tc decay constant λ = 0,00192 min ^-1, and a correction for the direct BPI values for maintaining the interval of 180 minutes between the time of the study in bone and tissue phase, namely K = e ^{-λ · t ·} 180 / t, where t - time in minutes between the tissue and bone phases of the study; IS is calculated as the ratio of the average count of impulses in the leg muscle in the bone phase (N _m ) to the average count of impulses in the leg bone in the bone phase (N _k ): IS = N _m / N _k , based on the data obtained, the degree of ischemia is established, so when the values of IV 1.54 ± 0.17 and IP 0.68 ± 0.04, as well as failure to identify foci of aseptic necrosis and areas of lack of blood supply, assess the presence of I-IIA degree of ischemia; with IV 1.36 ± 0.18 and IP 0.88 ± 0.06, as well as failure to identify foci of aseptic necrosis and identification of areas of lack of blood supply in the tissue phase, the presence of IIB degree of ischemia is assessed; with IV 0.93 ± 0.27 and IP 0.93 ± 0.14 or not determined, as well as the identification of foci of aseptic necrosis and the identification of areas of lack of blood supply in the tissue phase assess the presence of IIB degree of ischemia; with IV 0.82 ± 0.18 and IP 0.93 ± 0.04 or not determined, as well as identifying foci of aseptic necrosis and identifying areas of lack of blood supply in the tissue and bone phase, the presence of grade IIIA ischemia is assessed.