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Cardiovascular and Respiratory Disorders and Diseases

Cardiovascular and Respiratory Disorders and Diseases

By Arnold Plotnick, DVM

The cardiovascular system includes the heart and the blood vessels (arteries, veins, and capillaries). This system is responsible for pumping and delivering blood to the rest of the body. This system is of vital importance because the blood contains oxygen, nutrients, hormones, and antibodies, all of which are essential substances for survival. The respiratory system is usually divided into the upper respiratory system (nasal cavity and sinuses) and the lower respiratory system (bronchi and lungs). The respiratory system is closely affiliated with the cardiovascular system. The heart pumps blood to the lungs, and the lungs give off carbon dioxide and take up oxygen, which is then delivered to the rest of the body via the circulatory system. Respiratory illnesses in cats are very common, running the gamut from minor illnesses, such as viral respiratory infections, to potentially serious illnesses, such as asthma. Disorders of the heart are also surprisingly common and are a significant cause of mortality in cats.

Cardiovascular Disorders and Diseases

Cardiovascular Disorders and Diseases

Heart disease is a common occurrence in cats and can occur at any age. Disorders of the heart valves occur, but are much less common in cats than they are in dogs. Disorders of the heart muscle itself, however, are very common and can have serious health consequences. Fortunately, the most common heart disorder in humans- atherosclerosis (build up of plaque in the blood vessels that supply the heart)-is almost never seen in cats.

Healthy cardiovascular and respiratory systems are critical to a cat's overall well-being.

Valve disorders

Valve disorders

The heart has four valves. The mitral valve is on the left side of the heart, between the left atrium and left ventricle. The tricuspid valve is on the right side of the heart, between the right atrium and the right ventricle. The pulmonic valve mediates blood flow from the right ventricle to the lungs, and the aortic valve controls blood flow from the left ventricle, out through the aorta to the rest of the body. The job of these valves is to keep blood flowing in the proper direction. If the valves become defective and malfunction, the tight seal that the valve makes is compromised, and blood may escape around the valve.

Causes and symptoms

Valve disorders are often detected as heart murmurs during physical examinations. Valvular defects can lead to heart enlargement and eventual congestive heart failure (CHF). This can happen in younger animals as a result of a congenital malformation or in older animals as a natural result of aging. Valve disorders are much less common in cats than in dogs, however, and CHF secondary to valvular problems is rare.

Diagnosis and treatment

Definitive diagnosis of a valvular disorder is made via cardiac ultrasound. Medication may or may not be prescribed by your veterinarian, depending on whether there is concurrent heart disease present.

Heart Murmurs

A heart murmur is an abnormal sound that is caused by turbulent blood flow through the heart. Although the presence of a murmur is not necessarily something to be worried about, all murmurs should be investigated because they could be the first sign of serious heart disease. Cardiac problems that can cause a heart murmur include cardiomyopathies (diseases of the heart muscle), disorders of the heart valves, and congenital defects. Murmurs are graded on a scale from 1 to 6, with 1 being barely audible and 6 being intense enough to cause vibrations that can be felt by touching the chest. The intensity of the murmur does not correlate with the severity of the condition, and not all murmurs are indicative of heart disease. Heart murmurs can be the result of other systemic diseases or conditions, for example, anemia or high blood pressure. In some cases, a murmur may be completely benign and not be associated with any illness at all. Murmurs are common in older cats. Some kittens are born with murmurs and then outgrow them. To investigate the cause of a murmur, diagnostic tests are necessary and may include blood tests, blood pressure measurement, chest X-rays, an EKG, and an echocardiogram (ultrasound examination of the heart).

Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy

Cardiovascular disease is the number one cause of death in people in the United States. Most cat owners probably don't realize that heart diseases are also quite common in cats. In fact, disorders of the myocardium (heart muscle) are the major cause of heart failure in cats. The most common feline cardiomyopathy (heart muscle disorder) is hypertrophic cardiomyopathy (HCM). This condition occurs when the heart muscle, especially that of the left ventricle, becomes excessively thickened. The job of the left ventricle is to pump blood out through the aorta to the rest of the body. When the wall of the ventricle becomes thickened and stiff, the ventricle cannot hold as much blood, and less blood is sent to the body with every pump. Frequently, the septum (the wall that separates the right side of the heart from the left) becomes thickened, too. This makes it even more difficult for blood to flow out of the aorta and puts a big strain on the heart. The chamber above the left ventricle, called the left atrium, tries to pump blood into the thickened left ventricle, but it is not easy because the thickened ventricle is stiff and much less compliant. This causes increased pressure in the atrium, and the atrium gets larger and larger. The increased pressure in the atrium may be transmitted to the lungs, resulting in fluid retention in the lungs and eventual CHF.

Causes and symptoms

Although there are specific conditions that can cause the heart muscle to become thicker (such as hyperthyroidism and high blood pressure), HCM is considered to be a primary disease because in most cases an inciting cause cannot be found. In Maine Coons, however, a genetic predisposition for HCM has been discovered. Eventually, through selective breeding, the gene responsible for HCM in Maine Coons may be eliminated. If HCM is identified in any cat, it is advisable not to breed the affected cat and to carefully screen closely related family members. The majority of cases, however, are domestic shorthaired cats without any family history of disease. Cats of either sex can be affected, although males are predisposed. Most cases occur in middle age, usually between the ages of four and eight, although the disease has been reported in cats as young as three months and as old as seventeen years.

Diagnosis and treatment

The clinical signs of HCM can vary greatly from cat to cat. Some cats present with nonspecific signs, such as lethargy, decreased appetite, weight loss, hiding, and reluctance to socialize with the owner and with other cats. Coughing, which is common in dogs with heart disease, is rare in affected cats. In a majority of cases (55 percent), cats have no clinical symptoms, and a diagnosis is pursued only after some abnormality-a heart murmur or an abnormal rhythm-is detected during a routine physical exam when the veterinarian listens to the chest with the stethoscope. A lesser but substantial number of cats are discovered to have HCM when they present to the veterinarian already in CHF. An even more upsetting (and dire) scenario is the discovery that a cat has HCM when it presents as an emergency with sudden painful hind limb paralysis. This devastating complication of HCM occurs when a blood clot (also known as a thrombus) forms within the left atrium and a small piece of this clot (called an embolus) breaks off from the main clot and travels down the aorta, becoming lodged at the end of the aorta and rapidly cutting off the blood supply to the legs. This condition is known as arterial thromboembolism (ATE).

X-rays, electrocardiograms (EKG), and echocardiograms (cardiac ultrasound) are the common diagnostic tests performed on animals with suspected heart disorders. For cats with HCM, however, x-rays are of limited usefulness. X-rays tend to be normal in the early stages of the disease. As the disease progresses and the cat goes into heart failure, pulmonary edema (fluid in the lungs), and/or pleural effusion (fluid in the chest cavity) may be visible on the x-rays. Although most EKGs are normal in cats with HCM, an EKG can provide the veterinarian with useful information because disturbances in the electrical conduction system of the heart occur in about 30 percent of cats with HCM.

Ultimately, a definitive diagnosis of HCM is achieved by means of echocardiography (cardiac ultrasound). Ultrasound allows for evaluation of many parameters, including the size of the chambers, the thickness of the heart muscle, the function of the valves, how well the heart is contracting, how efficiently the blood is flowing through the heart, and whether there is a blood clot in the left atrium. The goals of treating cats with HCM are to improve the ability of the ventricle to fill, prevent or delay the onset of CHF, and prevent such Biblecomplications as arterial thromboembolism. Medications may be prescribed to slow down the heart (beta blockers), so that there is adequate time for the stiff ventricles to fill, and to relax the heart muscle (calcium channel blockers), again to facilitate filling of the stiffened chambers. Cats who are in heart failure and have fluid accumulation in their lungs often benefit from having diuretics administered. Another category of drugs, called angiotensin converting enzyme (ACE) inhibitors, has been shown in some studies to be useful in managing HCM. Which drug or drugs are prescribed depends on the ultrasound findings, whether the cat has concurrent CHF, and the personal preference and experience of the veterinarian or veterinary cardiologist. To reduce the chance of a thrombus forming within the heart, veterinarians often give cats medications that reduce the blood's ability to clot, such as aspirin, heparin, or clopidogrel (Plavix).

The prognosis for HCM varies. Hypertrophic cardiomyopathy can progress rapidly in some cats, whereas in others the condition remains relatively static for years. Many cats will have slowly progressive disease that ultimately leads to CHF. A significant number of cats with HCM will be fine for a while, only to develop sudden rear limb paralysis due to ATE. When the heart muscle becomes thickened, the coronary arteries have trouble supplying enough blood to the heart muscle. The areas of inadequate blood supply may serve as a site where abnormal rhythms are generated. These abnormal heart rhythms can lead to fainting, or in some instances, sudden death. Cats who develop blood clots tend to do poorly. Those who survive their initial twenty-four hours have a median survival time of two to six months. Cats with CHF fare somewhat better, surviving for three to eighteen months. Those with no symptoms survive, on average, three to five years after the diagnosis.

Although cats of either sex can contract HCM, it is more common in males.

Radiograph showing a cat's lungs.

Arterial Thromboembolism

Arterial Thromboembolism

A significant number of cats with HCM develop ATE. This is one of the most serious complications associated with HCM and is one of the most common causes of hind limb paralysis in the cat. Cats with HCM are at increased risk of developing a blood clot (also known as a thrombus) in the left atrium of the heart.

Causes and symptoms

Arterial thromboembolism occurs when a piece of this thrombus-the piece is called an embolus-breaks free from the main thrombus and enters the circulation. The embolus eventually becomes lodged in a vessel, cutting off the blood supply to that area. Smaller emboli may travel into small arteries and affect blood flow to a limb or to other sites such as the brain, lungs, or kidneys. The vast majority (more than 90 percent) of emboli become lodged at "the aortic trifurcation"-the area at the very end of the aorta where it branches off to supply the left and right rear legs and the tail. This area has also been called the "saddle" area, and a blood clot lodged in this area is sometimes termed a "saddle thrombus." Cats are literally normal one second and paralyzed in the next second.

Diagnosis and treatment

A diagnosis is usually made based on clinical signs at presentation. Most cats present with acute onset of lameness, partial paralysis, or complete paralysis of the affected limbs. The hind limbs are often cold, and the nail beds are cyanotic, that is, they have a bluish tinge due to lack of blood flow. No pulses can be felt in the rear legs. Many of the cats with ATE show signs of shock. Virtually all cats with ATE are in obvious and considerable pain, as evidenced by excitement, frenzy, vocalization, rolling, and panting.

Some cats diagnosed with ATE were diagnosed with HCM not long before. Others may have been diagnosed with HCM months or even years before, with no clinical signs until that day. Some cats with CHF that is well controlled may suddenly fall victim to ATE. The majority of cats with ATE, however, present without any evidence of preexisting heart disease. For these cats, diagnostic tests such as cardiac ultrasound invariably confirm that there is heart pathology and that a blood clot is present within the left atrium. Ultrasound machines are able to evaluate arterial blood flow. During the cardiac evaluation, the ultrasound probe can be placed on the inside of the thigh to evaluate arterial blood flow to the rear limbs. An inability to detect arterial blood flow supports the diagnosis of ATE. The ultimate goal of managing the acute episode of ATE is to pull the cat through this initial critical phase. Controlling pain, improving cardiac blood flow, and treating CHF if present are the top priorities. Restoring blood flow to the rear limbs Bibleis of secondary importance; making sure the cat survives takes center stage. Many cats do not survive the initial episode; they either die or are euthanized within the first 48 hours of the onset of paralysis. Pain control is essential because these cats are in great discomfort. Improving circulation using intravenous fluids is of paramount importance. This can be a challenge, however, because fluid therapy must be administered cautiously in cats with heart disease.

Acepromazine, a sedative, has been used by some clinicians to decrease anxiety and improve blood flow to the affected areas by dilating the blood vessels. Anticoagulants are recommended during the acute crisis to prevent any new thrombi from forming in the heart and to prevent the embolus from growing in size and further reducing the blood flow to the affected region. Drugs are available that have the potential to dissolve a thrombus or embolus. They are expensive, however, and can have significant side effects. Whether these drugs offer any real benefit remains controversial. Without treatment, in the natural course of disease, blood flow will often resume to the affected area as the body eventually dissolves the clot on its own. Vessels in the tissues adjacent to the blocked vessel experience a gradual increase in blood flow as they learn to adapt to their injury. Preventing ATE is a logical goal, but few studies on how to do so have been performed in veterinary medicine, and therapeutic recommendations are lacking. Platelets play a significant role in the development of ATE, and antiplatelet drugs such as aspirin are a logical choice for prevention of ATE. Aspirin treatment, however, has not been reported to result in dramatic reduction in the prevalence of ATE. Clopidogrel (Plavix), an antiplatelet drug commonly used in humans, has recently been shown to be safe and effective in helping reduce the incidence of ATE.

HCM is a frustrating disorder to treat, and it becomes even more frustrating when ATE complicates the picture. Although there is no predicting which cats with HCM will be stricken with ATE, continued research in the areas of prevention and treatment will allow for more successful management of this devastating disease in the future.

A cat who is breathing through her open mouth possibly has a respiratory illness.

Arterial thromboembolism is a serious complication of HCM and one of the most common causes of paralysis in cats.

Dilated Cardiomyopathy

Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a heart muscle disorder in which the walls of the right and left ventricles-the chambers that pump blood out of the heart-become thinner and thinner. As this happens, the contractions get weaker and weaker, and the heart is unable to pump blood with sufficient force, leading to heart failure.

Causes and symptoms

In 1987, researchers discovered that a deficiency in the amino acid taurine was a significant cause of DCM. Pet food manufacturers supplemented their diets with adequate amounts of taurine, and the incidence of DCM plunged. Now, very few cases can be attributed to taurine deficiency. Most cases diagnosed today are idiopathic; that is, they have no known cause. The clinical signs of DCM may include poor appetite, lethargy, and inability to play or exercise. Cats in heart failure secondary to DCM may show labored breathing or a distended abdomen. Unfortunately, by the time DCM is diagnosed, nearly all cats are in CHF.

Diagnosis and treatment

A diagnosis of DCM is made after various tests are performed, such as chest x-rays, an EKG, and an echocardiogram. x-rays usually show an enlarged heart and may show patchy accumulations of fluid in the lungs (pulmonary edema) and enlarged veins around the heart. The EKG may be normal or may show an abnormal rhythm. The most informative test is the echocardiogram, which typically shows severe dilation of all chambers of the heart in combination with weak cardiac contractions. Blood levels of taurine should be evaluated in all cases of DCM. Treatment may include drugs that help the heart contract more strongly, such as digitalis or pimobendan, as well other drugs to control CHF if present. Taurine supplementation is recommended for cats with low taurine levels. Periodic echocardiograms are necessary to monitor the course of the disease. Cats with DCM secondary to taurine deficiency have an excellent prognosis if they receive taurine supplementation and their CHF is under control. Cats with idiopathic DCM and CHF have a guarded to poor prognosis. Medication helps stabilize the patient but doesn't alter the progression of the heart failure. Most cats survive only a few months after the diagnosis is made.

Change in Voice

Occasionally, cat owners will become aware of a change in their cat's voice. The most common cause is a viral upper respiratory infection. Most viral URIs result in runny eyes, snotty nose, and lots of sneezing. Occasionally, they result in laryngitis-a "sore throat"-and this can lead to hoarseness and a change in voice. Cats with oral tumors involving the throat or the vocal cords may experience a change or loss of voice. There is also a condition called laryngeal paralysis in which the cartilages and muscles that control the vocal folds in the throat become dysfunctional, causing the larynx to not open properly and leading to a change of voice. This is much more common in dogs than cats. Even though most cases are due to upper respiratory infections that are fairly benign, a change in voice should be evaluated by your veterinarian. He or she may want to sedate the cat and perform a thorough oral exam, looking at the back of the throat and even trying to pass an endotracheal tube down the trachea to see if there is a mass or other obstruction. X-rays may be necessary to look for masses that are in the trachea or in the neck.

Respiratory System Disorders and Diseases

Respiratory System Disorders and Diseases

Disorders of the feline respiratory system can be generally divided into disorders of the upper respiratory system (the nasal cavity and sinuses) and the lower respiratory system (the airways and the lungs). Examples of disorders of the upper respiratory system include infections and nasopharyngeal polyps. Asthma is the most common lower respiratory disorder in cats. Infectious bronchitis is less common. Heartworm disease is frequently diagnosed in dogs but is still quite rare in cats.

Upper Respiratory Infections

Upper Respiratory Infections

Upper respiratory infections (URIs) are a common, contagious disease in cats.

Causes and symptoms

The most common cause of upper respiratory infections is viral, with the feline herpes virus (FHV) and the calicivirus (FCV) accounting for 80 percent of all feline URIs. Bacteria and fungi can also cause URIs in cats. Cats can acquire these infections through several means, including coming into contact with another cat who has a URI, contact with aerosolized virus particles when an infected cat sneezes, contact with items such as infected food or water bowls, or contact with human hands that have touched an ill cat. Young kittens are at greatest risk of infection. The most common way that kittens contract URIs is via nursing, around the time of weaning. Cats exposed to other sneezing and ill cats, such as in a shelter environment or a cattery, are also at increased risk, as are unvaccinated cats and cats with immunosuppressive disorders.

Once exposed to the virus, cats experience an incubation period lasting two to five days, after which signs of infection develop. These may include lethargy, decreased appetite, sneezing, conjunctivitis, watery discharge from the eyes and/or nose, congestion, and fever. Corneal ulcers can develop, especially in cats infected with FHV. Ulcers in the mouth and on the tongue commonly develop in cats infected with FCV, and cats may drool as a result.

Diagnosis and treatment

Diagnosis of URI is based mainly on clinical signs. Determining specifically whether FHV, FCV, or both are responsible for the infection is rarely necessary because treatment is symptomatic regardless. Treatment is usually aimed at preventing a secondary bacterial infection from occurring by administering antibiotics. The amino acid lysine is thought to improve recovery from these infections and is often prescribed as well. Most cases resolve in five to fourteen days. In stubborn cases, antiviral drugs, such as famciclovir, can be administered. Cats with conjunctivitis or corneal ulcers may also require topical eye medications. Cats with severe nasal congestion may experience poor appetite because they cannot smell their food. These cats may need to be fed with a syringe or given appetite stimulants until the congestion resolves. Hospitalization is rarely necessary. Once infected, cats become carriers of the virus and may periodically have bouts of URI during times of stress. Vaccines against viral URIs are available. They can reduce the potential for infection in cats who have never been exposed to the virus. Most cats, however, are exposed to the virus during kittenhood and are carriers. Vaccination does not eliminate the carrier status of previously infected cats, and it does not prevent viral shedding. However, vaccinated cats experience milder symptoms when the virus reemerges from dormancy.

Using an Inhaler

Inhaled steroids are the most potent inhaled anti-inflammatory drugs available. Inhaled steroids like fluticasone (Flovent) are of a large molecular size and thus do not pass into the bloodstream when inhaled. As a result, they do not cause the unwanted side effects that pills or injections do. Many cat owners find that giving inhaled steroids is faster and seems to bother the cat less than trying to administer oral medication.The inhaler for these drugs fits on one end of the chamber, and a specially designed facemask attaches onto the other end. Cat owners can be taught by their veterinarian to gently place the facemask over the cat's mouth and nose, and the cat is allowed to inhale and exhale the medication seven to ten times with the mask in place. The facemask needs to fit properly. Flat-faced cats (Persians, Himalayans) may have difficulty achieving a tight fit.

A cat who is breathing through her open mouth possibly has a respiratory illness.

Nasopharyngeal Polyps

Nasopharyngeal Polyps

Nasopharyngeal polyps are benign masses that may arise in a cat's nose, pharynx (back of the throat), or middle ear. Those arising in the middle ear may extend through the eardrum, into the external ear canal.

Causes and symptoms

Why nasopharyngeal polyps occur is unknown, but they're most commonly seen in young cats; the average age at the time of diagnosis is one and a half years. The clinical signs of a polyp vary, depending on the location. Polyps in the nasal cavity cause noisy breathing or snoring, nasal discharge, coughing, and sometimes trouble swallowing. Those that occur or extend into the ear canal may cause ear infection, ear discharge, and vestibular signs (loss of balance, tilted head).

Diagnosis and treatment

In many instances, a diagnosis can be achieved via oral examination with the cat under anesthesia or heavy sedation. The soft palate is pulled back with a surgical instrument, and if a polyp is present it is usually readily apparent. X-rays of the skull may be useful in making or confirming the diagnosis. Polyps that have invaded the ear are diagnosed by visualizing the polyp deep in the ear canal using an instrument called an otoscope. In some cats, sedation is required for a proper, thorough ear exam. If the polyp is located deep in the middle ear, a computed tomography (CT) scan or magnetic resonance imaging (MRI) can give additional information as to its full extent. Polyps located above the soft palate that extend into the back of the throat are treated by grasping them with a hemostat at the base of the polyp and plucking them out. This usually causes instant improvement in breathing and a complete resolution of clinical signs. Polyps that extend into the middle ear require a more complex surgery. The prognosis for recovery is excellent, although if the polyp is not completely removed there is a possibility of recurrence.

Asthma

Asthma

Asthma in humans is a lower airway disease that causes people to cough and wheeze and limits their ability to exercise. These clinical signs occur because the airways in asthmatic humans are hyperreactive and may undergo spontaneous constriction when exposed to certain stimuli. A remarkably similar condition exists in cats.

Causes and symptoms

Asthmatic cats experience recurrent bouts of coughing, wheezing, and labored breathing. The condition affects approximately 1 percent of the general cat population, and more than 5 percent of Siamese cats. Some cats have only a brief history of coughing episodes before presenting with acute, severe respiratory compromise, the so-called asthma attack. When not having episodes of coughing or wheezing, most cats behave completely normally. Clinical signs of asthma in cats may be acute or chronic. In acute cases, there is a history of sudden onset of labored breathing. In most cases, however, asthmatic cats are presented to veterinarians with a complaint of chronic coughing.

Diagnosis and treatment

There are no simple laboratory tests that can diagnose feline asthma with 100 percent certainty. A diagnosis is usually made based on the history, physical examination findings, and x-rays of the chest. Radiographs (x-rays) provide the most information for veterinarians presented with a coughing cat. Radiographs help eliminate other causes of coughing and wheezing, such as heart failure, pneumonia, lung cancer, and inhaled foreign bodies. Identification of thickened air passages (seen as "doughnuts" and "train tracks" on an X-ray) is the most important radiographic finding in a diagnosis of feline asthma. Other helpful tests include a complete blood count and a heartworm test. Occasionally, if clinical signs, x-rays, and blood tests are ambiguous, other tests such as bronchoscopy may be necessary. Bronchoscopy involves the use of an instrument with a tiny fiberoptic camera (the bronchoscope) to examine the inside of the lungs and collect specimens for cytology or biopsy.

The ideal treatment of asthma would be to limit the cat's exposure to the offending allergen. However, it is often impossible to definitively determine which allergen is triggering the bronchitis. People should not smoke or apply perfume around asthmatic cats, and dusty cat litters should be avoided. Corticosteroids are the most effective long-term treatment of feline asthma. These drugs are anti-inflammatory, and they help in removing the inflammatory cells that surround the airways in affected cats. Humans who receive oral steroids often experience serious side effects that may preclude their routine use. Fortunately, cats are fairly resistant to the health-threatening side effects of corticosteroids. Prednisolone, initially given at high doses for two weeks and then slowly tapered down to every-other-day therapy, remains the most consistent, reliable, and effective treatment for asthma in cats.

Bronchodilators are drugs that reverse airway constriction, allowing the air passages to open. Bronchodilators may be used as adjunct therapy, but they shouldn't be used as sole treatment. Chronic inflammation is the root of the problem, and treatment of this inflammation using steroids is the cornerstone of therapy. Some cat owners find it nearly impossible to orally medicate their cat. In this situation, an injectable long-acting steroid may be given. This is a less desirable approach to treatment, however, as these injections vary in how long they last (anywhere from three weeks to three months) and may be associated with side effects such as transient diabetes. When the effects of the injection wear off, the clinical signs usually return.

Administration of medication via inhaler is an alternative therapeutic option. Metered dose inhalers (MDIs) are commonly used in asthmatic humans. They allow high concentrations of drugs to be delivered directly to the lungs, avoiding or minimizing systemic side effects. Inhaled drugs relieve symptoms of asthma much faster than oral or injectable drugs. The inhalers are designed for people to coordinate the activation of the device during a slow, deep inhalation for optimal lung delivery. Obviously, this cannot be controlled in children or in animals. Addition of a spacer allows the MDI to be used in children and pets. The spacer is a plastic chamber about the size of an inner roll of toilet paper. (See Using an Inhaler.) Feline asthma is not a curable disease. Recent advances in our understanding of the disorder, however, have allowed veterinarians to devise more effective treatment plans, and cats are breathing a little easier as a result.

Unfortunately, asthma is a common illness of cats.

Using a dust-free litter, such as wood pellets, can help reduce the incidence of feline asthma attacks.

Steroids, such as prednisolone, are very effective treatment for feline asthma.

Chronic Bronchitis

Chronic Bronchitis

The bronchi are the tubes that transport air from the trachea (windpipe) to the lungs. Within the lungs, the bronchi divide into smaller branches called bronchioles. Inflammation of the bronchi and bronchioles is called bronchitis, and when the inflammation is persistent it is called chronic bronchitis. Although chronic bronchitis is more common in dogs than in cats, some cats do suffer from it.

Causes and symptoms

The cause of most cases of chronic bronchitis is not known; in some instances, the condition develops as a result of a longstanding infection. Chronic exposure to environmental irritants, such as cigarette smoke, has been suggested as another possible cause of chronic bronchitis in cats. Cats with chronic bronchitis may show clinical signs related to the respiratory system, including coughing, rapid and/or labored breathing, and wheezing, as well as general signs of illness such as poor appetite and lethargy. The respiratory compromise may affect the cat's ability to play or exert herself.

Diagnosis and treatment

Diagnosis is usually made through evaluation of chest x-rays. In some instances, more advanced diagnostic tests are required, the best one being bronchoscopy. For this test, the cat is anesthetized and a long thin snake-like tube with a fiberoptic camera on the end (the bronchoscope) is inserted into the trachea and then down farther into the bronchi. This allows visualization of the airways, where samples of material from the airways can be evaluated for cytology, biopsy, and culture. Treatment of chronic bronchitis depends on the diagnostic findings. It an infectious agent is isolated from the culture specimen, treatment with antibiotics is warranted. Chronic bronchitis that is inflammatory in nature often requires antiinflammatory medications such as corticosteroids. Bronchodilators (drugs that widen the air passages) and cough suppressants may be indicated, depending on the severity of the condition. Chronic bronchitis cannot be cured, but it is often controllable through the use of medication. Obesity worsens the condition; cats should be maintained at their ideal weight. Environmental irritants such as chemical fumes, dust from renovations, and cigarette smoke can further irritate the airways and should be minimized.

Heartworm Disease

Heartworm Disease

The name heartworm disease is somewhat of a misnomer in cats; the heartworms primarily affect the lungs, not the heart. Heartworm disease is usually thought of as a dog disease. Feline heartworm disease (FHD), however, is more prevalent than once believed. It is now understood that whenever heartworm infection exists in the local canine population, it will also be found in the feline population. There are significant differences, though, between FHD and its canine counterpart.

Causes and symptoms

Cats acquire heartworm disease when a mosquito carrying heartworm larvae bites the cat. The larvae enter the skin through the bite wound and develop into juvenile worms. The immature worms enter a blood vessel and travel in the bloodstream. When they finally arrive at the lungs, they cause a dramatic inflammatory reaction. In many cases, the immune system of the cat reacts against the juvenile worms causing them to die, which results in an even more severe inflammatory response. In some cats, all of the juvenile worms die and the cat clears the infection. In other cats, a few juvenile worms escape destruction and develop into adult worms. Although most cats end up with only one or two adult worms in the pulmonary arteries of the lungs, even a small number of worms are potentially life-threatening.

The adult worms suppress the immune system, allowing them to live in the heart or lungs for months or even years, often causing no problems. When the adult worms die, however, a major, severe inflammatory reaction can occur. Pieces of dying heartworms can obstruct the pulmonary vessels, resulting in thromboembolism, which often leads to severe illness or fatal acute lung injury. The respiratory signs that develop when the juvenile worms arrive at the lungs and subsequently die are often misdiagnosed as asthma or bronchitis, when in fact it is part of a syndrome termed heartworm-associated respiratory disease (HARD). Even if the cat clears the infection, the initial damage to the lungs can be significant. Cats who go outdoors and have increased contact with mosquitoes are at increased risk of infection, but that doesn't mean that indoor-only cats are safe from the disease. In one study, 28 percent of cats diagnosed with heartworms were indoor-only cats. The signs of heartworm disease vary widely. Many cats show no clinical signs at all. Most cats have signs of respiratory disease such as coughing, wheezing, or rapid or labored breathing. Other possible clinical signs include intermittent vomiting (unrelated to eating), diarrhea, poor appetite, weight loss, seizures, and fainting. A heart murmur is sometimes heard on physical exam.

Diagnosis and treatment

Heartworm disease can be difficult to diagnose in cats. The most useful tests are heartworm serology, chest x-rays, and echocardiography. Serologic tests involve testing the blood for heartworm antibodies or heartworm antigens. A positive antibody test means that the cat has been exposed to heartworms but doesn't necessarily mean that the cat is currently infected with heartworms. A positive antigen test indicates that the cat is currently infected with adult female worms. In most cases, both tests are run to provide as much information as possible. Chest x-rays may provide additional information but are rarely definitive in making the diagnosis. In cats who are infected with adult heartworms, an experienced ultrasonographer may detect the worms via ultrasound. Detection of worms in this way allows for a definitive diagnosis.

Treatment of FHD varies depending on the individual cat. If the cat shows no clinical signs despite being infected, the cat should be closely monitored. The anti-inflammatory drug prednisolone is often administered to these nonsymptomatic cats in tapering doses, as medical supportive therapy. Cats who become acutely ill from heartworm disease need more aggressive medical attention, which may include hospitalization, intravenous steroids and fluids, drugs to relax the airways, and supplemental oxygen. The drugs that are used in dogs to kill off the adult worms are, unfortunately, not safe for use in cats. If adult worms have been identified via ultrasound, surgical removal of the worms by inserting a special catheter into right jugular vein and advancing it down toward the pulmonary vessels may be attempted in cats who are infected with several worms or in cats in critical condition from their illness. This procedure is very difficult and must be done by an experienced specialist at a referral center.

Heartworm disease is completely preventable. Monthly preventatives, either oral or topical, should be administered to cats at risk (that is, those in heartworm endemic areas). Both indoor and outdoor cats should be protected. Heartworm preventatives should be administered starting thirty days before the estimated onset of mosquito season and continued for thirty days after mosquito season has ended. In fact, the best option is to administer the monthly preventative every month, year-round. In endemic areas, prevention should begin in kittens starting at eight weeks of age.

In cats, heartworm actually affects the lungs more than the heart. Keeping your cat indoors lowers her risk of contracting heartworm.

Heartworm is completely preventable using monthly oral or topical medications.

From The Cat Bible, Copyright by Sandy Robins, licensed through ContentOro, Inc and used by arrangement with I-5 Press

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