Aortic Thromboembolism

Also Known As: ATE

Introduction

Cats that present with aortic thromboembolism almost invariably have significant underlying cardiac disease and often show overt signs of congestive heart failure. Treatment of the condition can be very challenging both in the prevention of reperfusion injury and management of existing heart problems.

Pathogenesis

Thromboemboli commonly lodge in the distal aorta and iliac arteries. They are formed within the heart - dislodging and entering the aorta. There are three factors that cause ischaemic damage in the limbs:

1) The thromboembolus itself

2) A series of subsequent vasoconstrictive events that decrease collateral circulation.

3) Reperfusion injury following the breakdown of the clot and return of collateral circulation.

The consequence of this is ischaemic neuromyopathy. The muscle is quite sensitive to ischaemic damage - with the clot causing a rigor mortis effect in the tissue. The peripheral nerves are fairly resistant to structural damage but they undergo rapid functional change. This functional failure can be reversed it blood flow is restored before structural nerve damage occurs (several hours later). The amount of structural nerve damage determines the level of permanent nerve damage.

Signalment

As mentioned, cats normally have underlying cardiac disease - most commonly hypertrophic cardiomyopathy (HCM).

Clinical Signs

The most common presenting signs are acute rear limb paralysis, depression, pain and dyspnoea. The paralysis may be unilateral or bilateral. On clinical exam there is an absence of femoral pulses in the affected limbs and the cranial tibial and gastrocnemius muscles feel firm on palpation. The footpads are cold and discoloured and there is no response to noxious stimuli or movement in the lower limb. Additional findings include a lack of tone in the anal sphincter, bladder distention and abdominal pain. Pain and underlying cardiac disease can cause tachycadia and tachypnoea. Additional signs of cardiac disease may be detected on cardiac auscultation such as a murmur, arrhythmia or gallop rhythm.

Diagnosis

Blood Pressure Reading

Blood pressure readings should be taken on all four limbs as this allows comparison between the normal and affected legs and indicated

Radiography

Thoracic

Treatment

Treatment includes supportive therapy with fluids and diuretics, use of a vasodilator such as acepromazine, and an anticoagulant such as heparin, aspirin, or warfarin. Heparin is generally used in the acute phase, and warfarin for long-term anticoagulant therapy. Clot dissolution has been achieved using streptokinase and urokinase. Surgical removal of aortic thromboemboli has not been rewarding. It is best performed within four hours of embolization. Amputation of the left atrial appendage has also been suggested to eliminate the nidus for thrombus formation. In most cases, surgery is not rewarding and medical management is preferred.

Prognosis

TIME Prognostic indicators As with most diseases, the severity of the disease and the resulting clinical presentation are variable. Clinical signs that indicate a ‘better’ prognosis include pale pink pad colour, tail movement, good anal tone, upper thigh muscle control, normal mental acuity, eupnoea and normal body temperature. Cats have a better prognosis if they have hypertrophic cardiomyopathy and not restrictive cardiomyopathy. Left atrial size also has prognostic significance, with severe dilation being a more ominous sign. The prognosis is worse if congestive heart failure is present

A recent study showed that affected cats had a 34% chance of surviving the initial thromboembolic episode; those that did had an average survival of 11.5 months. Reembolization was common. Prognosis varies with the severity of the embolic event, degree of ischemia, evidence of abdominal organ infarction and severity of the underlying cardiac disease.

Prevention

The presence of spontaneous contrast within an enlarged atria during echocardiography is seen in at-risk cats. These animals can be treated with prophylactic anticoagulants such as aspirin and.....

Aortic Thromboembolism Learning Resources
Flashcards Test your knowledge using flashcard type questions	Small Animal Soft Tissue Surgery Q&A 03

References

Gilson, SD (1998) Self-Assessment Colour Review Small Animal Soft Tissue Surgery Manson

Moise, NS (2007) Presentation and management of thromboembolism in cats In Practice 2007 29: 2-8