Imagine the shock of a sudden and painful health condition that leaves your beloved feline friend paralyzed and in distress. This is the reality of Feline Aortic Thromboembolism, often abbreviated as FATE or saddle thrombus. In this article, we'll explore this dramatic and challenging condition, from its causes and symptoms to treatment options and what pet owners can expect.
Deciphering Feline Aortic Thromboembolism
Feline Aortic Thromboembolism, known as FATE or saddle thrombus, is a severe condition that arises suddenly. It manifests as the paralysis of one or both of a cat's rear legs, rendering them useless and often noticeably colder than usual. Cats suffering from FATE experience extreme pain, hyperventilation, and vocal distress. This condition results from a blood clot, medically known as a thrombus, forming in the heart and traveling down the aorta, ultimately lodging at the saddle.
Understanding the Saddle Thrombus
The aorta, the body's largest artery, originates from the heart and travels down the back, branching into arteries that supply blood to the rear legs. The point where the aorta divides into the left and right iliac arteries is referred to as the saddle. A saddle thrombus is a blood clot that breaks off from a larger clot in the heart and becomes lodged at the saddle. This not only obstructs blood supply to one or both rear legs but also triggers a cascade of metabolic events, including the release of inflammatory mediators, such as serotonin. The muscles in the affected legs become rigid, the foot pads turn bluish, and the cat experiences excruciating pain. Inflammatory mediators can lead to circulatory shock.
The Origin of the Saddle Thrombus
Saddle thrombus originates from a larger clot in the left atrium of the heart, raising the question of why a cat's heart would develop such clots. Astonishingly, 89 percent of cats with saddle thrombus have underlying heart disease. Heart disease disrupts blood flow, creating an environment conducive to clot formation.
However, not every cat with heart disease will develop abnormal clots. Predicting which cats are at risk remains a challenge. Hypertrophic cardiomyopathy, the most common feline heart disease, may offer some clues. Factors like the size of the left atrium and the presence of "smoke" during echocardiography (a whispy material seen in circulating blood) are considered by some cardiologists as suggestive risk factors. Unfortunately, many cats with saddle thrombus display no previous heart disease symptoms, making the thrombus episode their first sign of a problem.
Assessing the Severity: How Bad Can it Get?
The outcome of FATE varies but can be quite severe. Let's explore the possibilities:
*Best Case Scenario (Saddle Thrombus Without Concurrent Heart Failure)*
In cases where heart failure is not concurrent with saddle thrombus, the primary focus is on pain control and nursing care until the thrombus dissolves, restoring circulation. However, the interruption of blood flow to the legs can lead to significant tissue damage, potentially life-threatening. Toxic biochemicals from damaged tissue can be released into the bloodstream when the clot dissolves, possibly proving lethal, even in the absence of heart failure. Recovery can be partial or complete, taking several weeks to determine.
Key Takeaways
- Treatment focuses on pain management and nursing care.
- Heart failure may develop in the future, requiring medication.
- Blood thinners are needed to prevent future saddle thrombi.
- Survival may vary, with some cats not surviving the circulatory situation.
Saddle Thrombus With Concurrent Heart Failure
When a cat experiences both saddle thrombus and heart failure, it faces a life-threatening cardiac crisis. Controlling heart failure with medication alongside thrombus recovery is crucial. Cats in this scenario require heart medication, blood thinners, and nursing care. The median survival time for saddle thrombus cats with heart failure is 77 days, compared to 223 days for those without heart failure.
Tissue Damage from Thrombus
Permanent limb damage is possible but not common. Some cats may experience skin or muscle loss due to circulatory compromise. In about 5% of cases, tissue damage presents as an open wound, which should heal as circulation returns. In more severe cases, amputation of a limb may be necessary.
Rapid Death from Tissue Damage or Heart Failure
Unfortunately, many cats may die during the hospitalization process. Factors like heart failure, the formation of new clots, or reperfusion injuries when toxic substances enter the bloodstream as circulation returns can contribute to fatalities. One critical predictive parameter is the cat's body temperature at presentation, with cats having a body temperature over 98.9⁰F having a greater chance of survival.
Euthanasia Considerations
Given the potential for recurrent saddle thrombus episodes, long-term medication administration, and treatment for heart disease, along with the initial pain and severity of the condition, approximately 50-75% of pet owners choose euthanasia without attempting treatment.
Statistics
- 50% of treated cats survived to be discharged from the hospital.
- Median hospitalization time was two days.
- Cats using aspirin for future clot prevention had a median survival time of 192 days, while those using clopidogrel bisulfate had 443 days.
- 25% of cats using aspirin as their primary clot prevention drug after discharge had at least one more FATE episode within 6-12 months.
What to Expect at the Hospital
Upon arrival at the hospital, the veterinarian must swiftly determine whether the cat is suffering from a saddle thrombus or another cause of rear limb paralysis and pain. Signs of a saddle thrombus include cold rear feet, bluish or purplish footpad color compared to the front feet, and sometimes a clipped toenail to check for bleeding. Pain relief is initiated, and the initial body temperature is recorded for prognosis assessment.
Once the cat is more comfortable, comprehensive blood tests and chest radiographs are performed. These tests evaluate kidney function, circulation-related toxins, biochemical body function, stress, heart failure, and potential lung cancer. Diuretics may be administered to alleviate fluid buildup caused by heart failure. Blood thinners may be used, transitioning to oral medications.
Most cats initially receive care from their regular veterinarian. The need for 24-hour care and the potential benefits of transferring to a specialty center should be considered. Specialty centers offer overnight pain relief and monitoring, allowing for immediate response to cardiac or embolism-related complications. A veterinary cardiologist assesses the underlying heart condition and prescribes necessary medications. Hospitalization ranges from a few days to a week for pain management, comfort, and appetite establishment.
Saddle Thrombus in the Absence of Heart Disease
While we've primarily discussed saddle thrombus in the context of heart disease, it's essential to note that other factors can lead to aortic thromboembolism. Approximately 6% of cats with FATE have cancer, often lung cancer discovered during chest radiographs. Cancer treatment becomes necessary, along with thrombus recovery and preventive measures against future clots.
In about 3% of cases, no apparent reason for the thrombus is found. In such instances, a thorough search for tumors, which can induce abnormal clotting, is initiated, often using abdominal ultrasound. This scenario adds the challenge of addressing the discovered cancer alongside managing thrombus recovery and clot prevention.
In conclusion, Feline Aortic Thromboembolism is a severe and often painful condition that can strike suddenly. Understanding the causes, symptoms, and potential outcomes is crucial for pet owners. While the prognosis varies, early intervention and close collaboration with a veterinarian can improve a cat's chances of recovery and comfort.
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