Thromboembolism in dogs symptoms. Arterial thromboembolism in cats. Therapy and prognosis

One of the main processes of healthy blood and the circulatory system is the ability of blood to coagulate and clot, which, of course, is vital for wound healing and normal recovery from scratches, cuts and other damage to both the skin and internal systems. However, blood clots that form in the wrong place or for the wrong reason can pose a serious threat to your dog's health as the clot can effectively shut down the circulatory system and/or travel to major organs and lead to risks such as stroke and others. acute and life-threatening conditions.

Dangerous blood clots can form inside the body for a variety of reasons, and generally, various risk factors for a potential clot can be identified and mitigated - for example, if your dog has had surgery and will be sedentary or resting in one place for an extended period of time.

A blood clot is known by the scientific name "thrombus" and by knowing some of the risk factors and how clots can form in the first place, you can ensure that you do everything you can to prevent them from developing. help you identify a potential problem in the adoption process soon enough to intervene.

In this article, we look at blood clots and their risks in dogs in more detail, including how they can form, how to identify the problem, and what can be done to treat them. Read on to find out more.

How can dogs develop a blood clot?

As already mentioned, blood clotting is an important element of a dog's normal healthy circulatory system, but when a clot develops inappropriately or otherwise results in blockage or circulation of the clot itself, it can present a serious problem.

There are so many different things that can potentially cause a blood clot, including sitting or lying in one position for long periods of time, so airlines sometimes offer compression hosiery for people on long-haul flights and encourage people to move around regularly.

Some of the potential causes of blood clots in dogs include:

• Recovery from surgery when the dog tends to lie still in one position for a long period of time.
• Any other forced or voluntary period of lying or sitting in one position without moving.
• Autoimmune disorders that can increase blood viscosity and make it thicker and more prone to clotting.
• Some forms of hypothyroidism make the blood more prone to clotting.
• Any condition that affects the bone marrow or blood, such as leukemia.
• Circulatory disorders, which can lead to pooling of blood in certain areas of the body. It also increases the risk of blood clots in sedentary dogs.
• Narrowing of the veins and arteries in the heart, which can lead to blockages and clots.
• Anemia.

These examples are simply some of the potential elements that may be combined to increase the risk of, or promote, a clot and are by no means exhaustive. If your dog has a medical condition or other risk factors for a blood clot (for example, after surgery), your veterinarian should inform you of this and advise you of possible warning signs of problems.

What are the symptoms of a blood clot in dogs?

The symptoms of a blood clot in dogs will often be invisible or very difficult to detect until they are acute and problematic, and because a blood clot can develop in many different areas of the body, the symptoms that they may present in the early stages can be highly variable.

Blood clots in the limbs, such as the limbs and tail, can lead to coldness in the affected area and potential paralysis, or the area in question may feel strange to your dog (for example, with pins and needles type of sensation) which can cause them try to shake it up and manipulate it to restore circulation. This can potentially dislodge the clot and cause it to migrate to another area of ​​the body, which can be very serious.

A clot in the area of ​​a dog's heart or lungs can lead to a range of systemic symptoms such as shortness of breath, exercise intolerance, and other obvious acute signs of a problem, and most importantly, it can be very difficult to find a dog's pulse.

Ultimately, there are no specific symptoms of a blood clot in any given dog or body part, and the definition of a blood clot quickly relies heavily on being aware of the risk factors for a blood clot and the symptoms it can cause in combination.

Again, your veterinarian should evaluate you with the appropriate risk factors for your own dog and specific symptoms to be vigilant if necessary.

Can a clot be treated?

A blood clot is a potentially life-threatening condition for your dog because the clot itself can cut off circulation and lead to necrosis of the affected area, in the case of the limbs. However, a clot from a limb that ruptures and travels through the dog's system is an even greater risk because it can be in or near a large organ and lead to a stroke or other serious and acute condition.

If you suspect your dog may have developed a blood clot, try to keep them as quiet as possible and contact your veterinarian immediately. Your veterinarian will advise you on how to get your dog to the clinic safely and with minimal movement potential, and then work quickly to administer a combination of blood thinners and fluid therapy.

This will help flatten and break up the clot and allow the system to flush it out under close supervision.

Thrombus treatment is risky, in both dogs and humans - while they cannot always be prevented due to their association with certain health conditions by keeping your dog mobile and encouraging them to stretch and move around regularly (unless your veterinarian advises otherwise). ) will help.

For the first time in medicine, the concept of blockage of a vessel (embolism) by something (for example, a thrombus), followed by a violation of the blood supply to surrounding organs and tissues, was introduced in 1856. In veterinary medicine, the first experimental work that showed the existence of a causal relationship between thromboembolism and heart disease in cats was carried out in the 60s of the twentieth century.

Causes of thromboembolism:

1) The most common aortic thromboembolism in cats with hypertrophic cardiomyopathy (HCM) and endomyocarditis, less often pulmonary embolism. At the same time, an increase in the chambers of the heart contributes to stagnation of blood and the formation of blood clots. Also, chronic cardiac pathology is accompanied by dysfunction of the liver and kidneys, which lead to insufficiency of the anticoagulant system of the blood. With endomyocarditis (inflammation of the endo- and myocardium), cell death occurs, which can also cause blood clots.

2) Severe infections and sepsis.

3) All kinds of shock.

4) Extensive surgical operations.

5) Immune diseases, allergies.

6) Oncological diseases (especially vascular tumors).

7) Chemical and thermal burns of the esophagus and stomach.

8) Extensive trauma and bleeding.

9) Poisoning with hemolytic poisons.

10) Incorrect use of drugs that increase and decrease blood coagulation.

Clinical signs (appear quickly, within a few minutes):

• The first symptom of a thromboembolism is often the animal's intense vocalization due to severe pain.
• The animal breathes frequently (dyspnea), with its mouth open.
• There is a decrease in the overall temperature, the development of shock (cardiogenic).

Paralysis or paresis of one or several limbs at the same time with a significant decrease in temperature in this limb (limbs), blue fingertips and a decrease or absence of pain sensitivity. Also, the arterial pulse on palpation is reduced or absent. Significant or complete loss of reflexes and sensation in a paralyzed limb. Muscles become firmer.

An important distinguishing feature of thromboembolism from acute (for example, traumatic) spinal cord injury, which is also accompanied by paralysis or paresis of the limbs, is a decrease in local temperature and pallor (or blue tint) of the fingertips!

The development of neurological symptoms in thromboembolism is based on damage to the nervous tissue as it is more sensitive to a lack of oxygen. A few minutes after the violation of blood supply in the nervous tissue, signs of ischemia develop. The severity of thromboembolism can be judged by the degree of neurological disorders.

The diagnosis is made on the basis of clinical signs, history taking and additional research methods (biochemical blood test, ultrasound dopplerography of large vessels of the abdominal cavity, ECG, echocardiography, X-ray, neurological examination, myelography, angiography).

Timely diagnosis of primary pathology allows preventing the development of complications. Thromboembolism of the aorta and pulmonary artery are the most dangerous conditions and often lead to the death of the animal. If the above clinical symptoms occur, it is necessary to urgently deliver the animal to the clinic as soon as possible, without wasting a minute! Take care of your pets and they will love you back. You can ask your questions on our forum.

Veterinary cardiologist

Blinova Elena Vladimirovna

Veterinary clinic Bambi.

In veterinary practice, one of the causes of serious circulatory disorders, and often the death of an animal, is thromboembolism. Sometimes the owners do not even have time to deliver their pet to the veterinary clinic, this disease develops so rapidly.

Thromboembolism- an acute violation of the natural circulation, which occurs due to blockage (embolization) of the artery by a thrombus, that is, a blood clot.

Particles exfoliate from this clot and spread throughout the animal's body, clogging small vessels and disrupting blood circulation. This sets off an inflammatory reaction that dissolves the clots and can be life-threatening if too many vessels or a large vessel (pulmonary artery, aorta) is affected.

The cause of thromboembolism is an increased tendency to form blood clots, which depends on many factors. Any damage to the vessel wall, the entry of certain enzymes into the blood, including digestive ones, can be a consequence of an increase in blood clotting. Also, an increase in thrombus formation is observed in violation of the anticoagulant system of the blood, that is, with a decrease in the release of substances that slow down blood clotting.

The photo shows a thrombus in the aorta in a cat.

Thus, there can be many reasons for this disease, for example, shock, surgical interventions, pathologies during pregnancy, trauma, allergies, ischemia, bleeding, unjustified use of drugs that increase blood clotting, and so on.

So, in chronic heart failure, animals are prescribed anticoagulant drugs (warfarin, aspirin, clopidogrel) for life as a prophylaxis. The expediency of such measures is explained by the fact that chronic heart failure is the most common cause of thromboembolism in cats (more than 85% of cases).

Thromboembolism has a very high recurrence rate, with recurrent disease being more severe than previous episodes. Acute relapse has a high mortality rate.

The disease can affect an animal regardless of species, sex and breed. But mostly thromboembolism occurs in cats.

Clinical picture

Thromboembolism is characterized by sudden onset, the signs of the disease develop very rapidly. Quite abruptly, pronounced depression and a complex of neurological disorders in the animal occur. His behavior indicates that the patient is in pain, but where exactly is not clear.

In the video, a cat with thromboembolism. Flaccid paralysis of the pelvic limbs.

The basis of neurological symptoms is ischemic damage to nerve tissues, because they are most vulnerable to oxygen deficiency. Already 3 minutes after the violation of blood circulation in them, signs of ischemia develop, the gray matter of the spinal cord is especially prone to necrosis. The complexity of the disease can be judged on the basis of the established degree of neurological disorders. In our veterinary clinic, each case was accompanied by paresis and paralysis with symptoms of damage to the lower motor neurons (flaccid paralysis); weakening or complete absence of reflexes, decrease or disappearance of pain sensitivity. There is monoparesis, paraparesis and tetraparesis.

In this video, a cat with paralysis of the lower extremities as a result of thromboembolism.

Diagnostics

Diagnosis of thromboembolism is carried out on the basis of many methods:

• Neurological examination.
• Laboratory determination of blood clotting time.
• Thrombocoagulometry.
• Identification of clinical symptoms (temperature changes, pain, paresis, paralysis, etc.).
• Biochemical and clinical analysis of blood.
• Angiography (X-ray examination of blood vessels, produced with the help of special radiopaque substances). This method is the most informative in this disease.
• Cardiological examination (Rg-KG, ECHOCG).
• Vascular ultrasound with Doppler.
• In case of death of the animal - pathoanatomical autopsy.

In this picture, we can clearly distinguish a blood clot in the heart (in the left ventricle) in a cat.

According to the results of all studies in our veterinary clinic, animals are divided into groups, this is necessary to predict the outcome and choose the treatment:

• 1 group. It includes patients with neurological disorders of 1-3 degrees, while there is a compensated circulatory disorder and a mild form of ischemia. With timely treatment in patients of this group, 100% survival and full preservation of the functions of all limbs are observed. Often such patients may recover spontaneously, but it is important to emphasize that in the absence of treatment, relapses are almost always observed!
• 2 group. It includes animals with neurological disorders of 3-4 degrees, blood circulation - subcompensated, the degree of ischemia - average. The survival rate in this group is 80%, it is not possible to completely restore the functions of the limbs.
• 3rd group. It includes patients with grade 5 neurological disorders. The mortality rate here is 98%, but in rare cases, such patients can still survive.

Treatment of thromboembolism

Therapeutic treatment of thromboembolism is aimed at ensuring blood flow to the heart, preventing further ischemic damage to still living body cells. Infusion therapy - to keep the liquid part of the blood in the vascular bed. Improvement in hematocrit and blood viscosity improves its fluidity, which facilitates its passage through the altered vascular bed.

Thrombolytic therapy is necessary to restore blood flow through clogged vessels and reduce pressure in them. Such therapy is carried out within 24-72 hours, after its completion, heparin therapy is carried out for 7 days.

Along with infusion and thrombolytic therapy, drugs from the group of antioxidants and antihypoxants are used, as well as drugs that improve peripheral circulation (pentoxifylline), anti-shock therapy is carried out.

The treatment of thromboembolism is surgical removal of the thrombus. This is possible when the thrombus is localized in the area of ​​the aortic bifurcation (its division into the common iliac arteries is usually located at the level of the IV-V lumbar vertebra). The technique of the operation is to open the aorta, after which the blood clot is washed out of the vessel by blood flow, then the aorta is sutured.

The video shows this process.

The complexity of the operation and the prognosis for its result depend on the severity of the patient's condition and the timeliness of the animal's owners contacting the veterinary clinic.

Based on practical experience, many veterinary surgeons believe that after the occurrence of an embolism, the maximum time during which an operation can still be performed is 1 hour. High mortality in arterial blockage is associated with reperfusion syndrome - a process in which the products of ischemic necrosis enter the bloodstream and have a pathogenic effect (capable of causing disease) on vital organs and systems.

In the implementation of long-term anticoagulant therapy, it is necessary to control blood clotting. It is best to do this in a veterinary clinic, but if in the future the owners do not have the time or opportunity for this, then they can be trained to conduct a rapid assessment of this indicator.

For this procedure, you will need a clean glass slide. On it you need to drip three drops of blood. Further, in order for the glass to maintain temperature, place it on the palm or wrist and swing it, controlling the flow of blood. Blood should clot after 5-9 minutes, and against the background of taking anticoagulants - after 7-9 minutes. If the clotting time decreases, you need to increase the dose of the drug.

Thromboembolism is a disease that develops suddenly, progresses very rapidly and often recurs. Since the main etiological factor - heart failure - is incurable, animals with thromboembolism must be observed and treated throughout their lives. Such a patient needs regular visits to the veterinary clinic for ongoing neurological examination. With professional patronage by an experienced veterinarian, such a pet can live a full life without serious complications.

⦁ Veterinary Clinic of Orthopedics, Traumatology and Intensive Care, Veterinary Clinic. A. Fillmore. Saint Petersburg.
⦁ Veterinary clinic. A. Fillmore. Saint Petersburg.
Thrombosis (novolat. thrombōsis - coagulation from other Greek. θρόμβος - clot) - intravital formation of blood clots inside the blood vessels, preventing the free flow of blood through the circulatory system. When a blood vessel is damaged, the body uses platelets and fibrin to form a blood clot (thrombus) to prevent blood loss. Under certain conditions, blood clots can form in the bloodstream even without vascular damage.
A clot that circulates freely throughout the bloodstream is called an embolus. When a thrombus covers more than 75% of the cross-sectional area of ​​the arterial lumen, the flow of blood (and, accordingly, oxygen) to the tissue is reduced so much that symptoms of hypoxia and accumulation of metabolic products, including lactic acid, appear. When obstruction reaches more than 90%, hypoxia, complete oxygen deprivation, and cell death may follow.
Thromboembolism is a combination of thrombosis and its main complication - embolism.

Pathophysiology of thromboembolism (TE). Triad of Virchow:
⦁ Deterioration of the endothelium. Under normal conditions, the endothelium of the blood vessel has the function of an anticoagulant. Abnormal (affected) endothelium contributes to the formation of a thrombus at the site of injury.
⦁ A change in blood flow velocity is one of the reasons leading to TE. Blood flow abnormalities are common in patients with cardiovascular disease. Blood stasis allows increased contacts between platelets and clotting factors with the vascular endothelium, thereby promoting coagulation. Turbulent flow can lead to the formation of endothelial injury and also promote coagulation.
⦁ Change in coagulation. Hypercoagulation has been identified in both dogs and cats with TE. An increase in blood coagulation factors II, V, VII, IX, X, XII and fibrinogen in combination with a decrease in the natural anticoagulant antithrombin III were found in different animal species with various pathologies. Several clotting disorders have been identified specifically in cats with aortic thromboembolism.

Thrombi that form in the arterial system, where blood flow is high, are mostly made up of platelets. The consequences of arterial thromboembolism are acute and often lead to catastrophic consequences. Aortic TE in cats is the most common example of arterial TE in veterinary medicine. Affected cats almost always have significant underlying heart disease and congestive heart failure. However, cases have been described in which some cats suffered from thromboembolism without heart failure, even if they had a tendency to heart disease.

Feline systemic thromboembolism (TEC) is a complication of burnout hypertrophic cardiomyopathy (HCM), restrictive cardiomyopathy, dilated cardiomyopathy, primary mitral valve disease, atrial and other cardiac neoplasms. Stagnation of blood in the dilated chambers of the heart and increased platelet reactivity are predisposing factors in the development of this pathology. As a rule, the blood clot is localized in the trifurcation of the aorta, which leads to severe ischemic lesions of the pelvic limbs and tail. If the clot is small, it can travel to one internal iliac artery and cause paralysis or paresis in only one pelvic limb. Less often, a thrombus can be in the vessels coming from the heart in the cranial direction: the subclavian and carotid arteries, causing a violation of blood flow to the chest limbs, neck and head. One publication reported that during cranial thrombus migration, the right thoracic limb may be affected, however, in our practice, there were cases of damage to both the right and left thoracic limbs. Systemic thromboembolism can also affect other organs, including the kidneys, gastrointestinal tract, and brain.

Clinical signs and initial diagnosis

Diagnostic Notes

Additional diagnostic methods

Visual diagnostics of animals with thrombosis gives us not only the diagnosis and topographic orientation of the pathology, but also the algorithm for further treatment of such patients, life forecasts.

⦁ Laboratory diagnostics (general clinical, biochemical blood tests, electrolytes) can reveal a variety of biochemical disorders. Most cats present with stress hyperglycemia, prerenal azotemia (which may also be associated with renal artery thromboembolism), hyperphosphatemia, and a dramatic increase in serum creatine kinase. There are reports of hypocalcemia and hyponatremia. A potentially dangerous complication of thromboembolism is an increase in potassium levels, often occurring suddenly as a result of restoration of tissue perfusion, although potassium levels may be reduced during the initial study. Additionally, coagulation tests are possible, although they are often normal.

Treatment of arterial thromboembolism

⦁ If the thrombus has formed recently (less than 2-4 hours), you can try aggressive thrombolytic therapy:
⦁ Streptokinase 90,000 IU/cat IV over 30 minutes, then 4,500 IU/cat/hour over 3 hours; according to various sources, the duration of therapy is 2-24 hours.
Possible side effects: life-threatening hyperkalemia secondary to massive muscle damage often occurs; reperfusion injury; bleeding (since streptokinase causes systemic fibrinolysis).
⦁ Tissue plasminogen activator (alteplase) 0.25–1.0 mg/kg/h intravenously. The total dose should not exceed 1–10 mg/kg. The advantage is faster thrombus lysis and less risk of bleeding. However, the use of the drug has a high percentage of deaths due to hyperkalemia and shock (due to reperfusion injury), and has not been proven effective for survival compared with conservative therapy.
⦁ Conservative therapy consists in the treatment of congestive heart failure, in the control of dehydration (including after aggressive thrombolytic therapy), the control and correction of hyperkalemia, hyperphosphatemia and azotemia, in drug analgesia and the prevention of arterial thromboembolism with low molecular weight heparins.

Drugs recommended for the treatment of arterial thromboembolism, if more than 3 hours have passed since the onset of symptoms of the disease:
⦁ Dalteparin (fragmin) 100–150 IU/kg subcutaneously every 12 hours.
⦁ Enoxaparin (Clexane) 1.5 mg/kg or 180 IU/kg subcutaneously every 6 to 8 hours.
The duration of therapy depends on the improvement of the clinical condition in animals with TEC, as a rule, the minimum course is about 7 days, with positive dynamics in the first 3 days of treatment.
⦁ Alternative therapy
⦁ Warfarin, a vitamin K antagonist. The dose should be titrated to increase prothrombin time 1.5-2 times above the baseline. The starting dose is 0.25 to 0.5 mg per cat every 24 to 48 hours orally. The dose is then adjusted to extend the prothrombin time to about twice its baseline or to achieve an international normalized ratio (INR) of 2 to 4. Warfarin therapy has a much greater chance of bleeding complications.
⦁ Heparin 200 IU/kg IV, then 150–200 IU/kg SC every 8 hours. Heparin does not dissolve the formed thrombus, but may prevent further activation of the coagulation cascade.
Prevention of further thrombus formation consists in the treatment of chronic heart failure, as well as the control of potassium and creatinine levels in the blood serum, taking into account the risk of hyperkalemia.

Joint, often life-long use of the following drugs is prescribed:
⦁ Aspirin 5 mg (low dose) to 81 mg (high dose) per cat, orally once every 72 hours.
⦁ Clopidogrel 18.75 mg/cat po once every 24 hours.

Forecast

Literature:

1. Gary D. Norsworthy, DVM, DABVP. The Feline Patient Fourth Edition, 2011.
2. McIntyre D.K., Drobats K.J., Haskings S.S., Saxon W.D. Ambulance and small animal intensive care, 2013.
3. Reimer S. B., Kittleson M. D., Kyles A. E. Use of rheolytic thrombectomy in the treatment of feline distal aortic thromboembolism, 2006.
4. veterinary focus. 22.1.2012.
5. Journal of Feline Medicine and Surgery. July, 2012.
6. Journal of Internal Medicine. September/October, 2014.
7. Goggs R., Benigni L., Fuentes V. L., Chan D. L. Pulmonary thromboembolism. J Vet Emerg Crit Care (San Antonio), 2009 Feb; 19(1):30–52.
8. Bright J. M., Dowers K., Powers B. E. Effects of the glycoprotein IIb/IIIa antagonist abciximab on thrombus formation and platelet function in cats with arterial injury. Vet Ther, 2003 Spring; 4(1): 35–46.
9. Klainbart S., Kelmer E., Vidmayer B., Bdolah-Abram T., Segev G., and Aroch I. Peripheral and Central Venous Blood Glucose Concentrations in Dogs and Cats with Acute Arterial Thromboembolism. J Vet Intern Med, 2014; 28.
10. Stephanie A. Smith, Anthony H. Tobias, Kristin A. Jacob, Deborah M. Fine, and Pamela L. Grumbles Arterial thromboembolism in cats: acute crisis in 127 cases (1992–2001) and long-term management with low-dose aspirin in 24 cases. J Vet Intern Med, 2003; 17:73–83.