Cardiovascular & Respiratory Problems
Asthma is also called chronic bronchitis or allergic bronchitis. Inhaled antigens within airways cause a sudden contraction of the airway smooth muscle, narrowing the air passages. The disease is often progressive. The antigens that initiate the airways are usually not identified, but the common suspects are grass and tree pollens, smoke (cigarette or fireplace), sprays (hair sprays, flea sprays, household deodorizers), dusty cat litter, and flea powder. Food allergy is also a consideration. Cigarette smoke is becoming a greater suspect in smokers' households because the pollutants gravitate to the floor or carpet. The most common sign of asthma is coughing, severe cases have difficulty breathing and wheezing.
X-rays or blood samples may be useful in some cases as an aid to diagnosis.
Treatment for mild asthmatic cases involves administering steroids such as prednisolone possibly in combination with drugs to dilate the air passages. Antibiotics are useful if there is a secondary infectious bronchitis. Weight loss in obese cats is an important part of therapy and if possible avoidance of the allergens that may be causing the asthma such as dusty cat litter and cigarette smoke. If an acute respiratory crisis develops then hospitalisation and oxygen therapy can be used.
The prognosis is good in the short term, however other problems may arise as a sequel to longstanding asthma problems.
Hypertrophic cardiomyopathy is the most common heart disease of the cat. It is known to occur secondary to hyperthyroidism, high blood pressure and some heart abnormalities. The left hand side of the heart enlarges and the heart becomes stiff and fails to fill with blood in between contractions. The average age of affected cats is 6 years.
These cats are most often examined because a murmur, or other heart abnormality, is detected during routine examination. Although some cases may be first diagnosed only after severe clinical signs become apparent
Many cats present with breathing difficulties. Some develop a paralysis of the hind limbs due to a blood clot (thromboembolism) traveling from the heart to the iliac arteries and cutting off blood supply to the hind limbs. The precise abnormalities found are dependent upon the stage of disease.
In order to assess these animals properly ECGs, ultrasound and X-rays may all be required. Blood pressure monitoring is important.
A variety of drugs can be used to treat heart failure and major therapeutic advances have been achieved over the last few years. The disease process is however irreversible. Animals in heart failure should not be stressed or excited if possible. Any fluid build up within the lungs can be reduced with diuretics and fluid around the lungs may need to be drained off to ease breathing.
The prognosis of affected cats is dependent upon the severity of disease. Those with no clinical signs have an average survival of nearly 5 years. Cats presented with evidence of heart failure have an average survival of 4-5 months. Systemic thromboembolism is a concern and often results in exacerbation of the heart failure. Recurrence is also likely.
Thromboembolic disease is the dissemination of particles of clotted blood throughout the vascular system. This frequently occurs secondary to heart disease, especially hypertrophic cardiomyopathy since that can create stasis and pooling of blood and it increases its likelihood to clot.
Blood clots can settle anywhere throughout the circulation but by far the most common site is the aortic trifurcation (saddle thrombus). The significance of this site is that the blood supply to the hindlimbs and tail is occluded. This leads to sudden onset paralysis of the hind limbs, which are cold to the touch and have no pulse.
The treatment is based on management of the underlying heart failure and attempting to promote collateral circulation within the affected limbs. The prognosis is guarded, around half of affected cats will survive the initial crisis, thereafter they need to show significant improvement in hind limb function over the next 24-72 hours. If this is not achieved then the prognosis is grave. Those animals which recover are at risk of the condition recurring.
Hypertension is a prolonged increase in blood pressure beyond normal limits and is common in cats.
The most common causes of raised blood pressure include hypertrophic cardiomyopathy, chronic renal failure and hyperthyroidism. Affected cats tend to be older animals and may present with increased thirst and urination, lethargy, blood in the urine, heart failure, or sudden onset blindness.
Blood pressure monitoring will detect and assess the extent of the problem, more extensive investigation is required to determine the underlying cause including blood tests, eye examination, X-rays and ultrasound.
Several drugs can be used to reduce blood pressure, amlodipine is probably most frequently used, in some circumstances benezapril is invaluable. Other treatment depends on the underlying cause. Prompt treatment is required for cats with sudden onset blindness if sight is to be recovered.
Upper Respiratory Tract Infections
A number of infectious agents can cause upper respiratory infections, the most serious are feline herpesvirus, feline calcivirus and Chlamydia psittaci.
The herpes virus and calcivirus are responsible for the majority of the cat flu cases seen in general practice. Both viruses are extremely contagious and both can be carried and excreted by apparently healthy cats.
The clinical signs of infection are fever, nasal discharge, sneezing, conjunctivitis, ocular discharge, eye or mouth ulcers and drooling saliva. Affected cats are usually very dull, inappetant and lethargic. Eating or drinking can be painful so many become dehydrated.
Treating these cats can be a very intensive process, intravenous fluids are required to maintain hydration, nutritional support by feeding with a nasogastric tube may be required. Antibiotics should be given to control secondary bacterial infection and topical eye drops should be given if conjunctivitis is a problem. Nasal decongestants are a useful symptomatic treatment.
If the cat responds to nutritional and fluid support within 4-6 days the prognosis is relatively good. Those cats that do not respond well should be tested for FIV and FeLV viruses.
Vaccination is the most effective method of control of feline herpesvirus and feline calcivirus and is strongly recommended.