Feline arterial thromboembolism

Since drug thrombolysis in cats does not achieve satisfactory results, the focus today is on the self-dissolution of the clot by the body's own repair processes.

Cats with abnormally increased hemostasis, which can occur with hyperthyroidism, tumors, extensive inflammation, blood poisoning (sepsis), injury, or disseminated intravascular coagulation, represent another risk group.

Endothelial cell damage exposes the underlying extracellular matrix, to which platelets attach and form a clot.

Substances such as antithrombin III, thrombomodulin, tissue-type plasminogen activator and urokinase dissolve formed blood clots and prostacyclin and nitric oxide inhibit platelet aggregation.

[8] They or parts of them are carried along with the blood flow, enter the aorta via the left ventricle, get stuck at vascular outlets and block them.

In cats, this occurs predominantly in the aorta in the area of its terminal branch, i.e., at the outlet of the two external iliac arteries (Aa.

[12] In contrast, aortoiliac occlusive disease (aortic bifurcation syndrome), which corresponds to the most common localization in cats, is extremely rare in humans.

Occlusion of the iliac arteries results in partial (paresis) or complete paralysis (plegia) of the hind extremities.

[19] The main symptoms can be summarized in the "5-P rule" - paresis (Lähmung), pallor (Blässe), pain (Schmerz), pulselessness (Pulsverlust), poikilothermia (Untertemperatur).

[22] Occlusion of a coronary artery (myocardial infarction) leads to cardiac arrhythmias, usually with a fatal outcome, and is therefore often no longer presented to a veterinarian at all, so that its frequency is possibly underestimated.

Occlusion of renal or intestinal vessels causes severe abdominal pain (acute abdomen) and often also leads quickly to death.

[22] The activities of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST) are elevated due to the death of muscle cells in the blood.

[30] The "kidney values" (creatinine, urea, SDMA) may also be elevated due to the shock-induced reduced renal function (prerenal azotemia).

[2] In most cases, the diagnosis can already be made in the most common location (aortic thrombosis) based on the previous report and clinical signs (peracute posthand paralysis without trauma).

Differential diagnosis should continue to exclude primarily trauma to the spinal cord (traffic accident, window fall), which may be due to an event not observed by the owner.

Lidocaine, in addition to its analgesic effect, also protects to some extent against damage caused by reopening of the occluded vessel (reperfusion injury).

Non-opioid analgesics do not provide adequate pain relief and may increase circulatory disturbances in animals, causing renal or gastrointestinal damage.

[43] Pimobendan also increases blood flow in the left atrium and heart ear to a small extent and additionally improves atrial function.

[8] On the other hand, if there is no congestive heart failure but reduced blood flow (perfusion), then intravenous therapy are infused.

This usually results in frequently fatal reperfusion injury, hyperkalemia, metabolic acidosis, kidney failure, and bleeding, so that the survival rate is often lower than with conservative treatment.

Surgical removal of the thrombus is also rarely performed in veterinary medicine because of the associated risks, although it can be successful in individual cases.

Therefore, the current focus is on endogenous dissolution of the clot and thus spontaneous revascularization, which occurs quickly enough in just under 40% of cases.

According to a U.S. study, only about one-third of cats survive arterial thromboembolism, with half of those who die being euthanized without attempted treatment.

[2] Prognosis depends largely on the extent and duration of damage, with bilateral complete occlusions of the iliac arteries having the lowest chance of survival.

If only one limb is affected and there is residual motor function, there is a better chance that the cat will recover and continue to live with a good quality of life.

Excess blood potassium (hyperkalemia) and elevated kidney enzymes (azotemia) are other negative prognostic factors.

Even after spontaneous reopening of the blood vessel (revaskularization), relapses often occur due to a new thromboembolism, which even thromboprophylaxis cannot reliably prevent.

[53] Anecdotal reports indicate that cats can survive such an event and lung function can return to normal with formation of collaterals.

For example, one study showed that a flow velocity in the left heart ear of less than 0.2 m/s was associated with the occurrence of thrombi and spontaneous echocardiographic contrast (smoke).

Spontaneous echocardiographic contrast is an aggregation of red blood cells and thus a thrombus precursor that resembles smoke on sonographic imaging.