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The heart valves close (with a snap) from 60 to 200 times a minute. If there are any bacteria in the blood, which will happen more frequently if there is a long term infected area such as the gums, odd ones may get trapped on the edges of the valves. There is then an response by the tissue of the valve triggered by this, and scar tissue tends to be formed on the valve edge. If these scars grow to much over 1mm, they will prevent the valve closing properly and blood will leak back on every heart beat. If the leak becomes bad enough, this will cause failure of the heart's function as a pump.
click here to closeSome Siameses and Boxers have a genetically caused narrowing of the aortic valve. Most can live normal lives, but some will be seriously disabled and have only a short life-span. Breeders are trying to select unaffected animals to breed from.
click here to closeThe reason all these things happen is that the body has evolved to survive accidents during breeding age but has not evolved to survive in old age.
click here to closeDrugs are used to counteract the effects of failure and to control the body's responses which make the situation worse.
The heart is a pump which is better than anything humans have yet designed. It can be regulated by demand and will pump a complex fluid without turbulence or damage to the cells within the fluid. It has no moving parts to wear out and will typically beat about half a billion times in an animal's lifetime.
There are things which can damage the heart, and there are particular degenerative processes which can lead to the pump failing. A few unlucky animals are born with defective hearts which will restrict their life expectancy, though some of them can be corrected surgically.
The commonest preventable cause of heart damage is dental infection. So dental hygiene is not just a cosmetic exercise.
Some breeds of cat and dog are inclined to have narrow heart valves which make it more difficult for blood to be pumped through them and so lead to overstrain of the heart. Some breeds of dog are prone to degeneration of the heart muscle (especially very large breeds) and some have abnormal valve structure.
Whatever the cause, when the heart is unable to pump blood as effectively as the body requires there are several ways in which the body tries to improve its blood supply.
Animals in heart failure will show a variety of symptoms. It is much easier to spot in dogs than cats (and difficult in cage pets too).
Treatment of heart failure is by means of drugs which will affect the heart or circulation to prevent the body's responses which overload a failing pump. These days we hope to give pets with failing hearts a long period of good quality active life by means of drugs, but the drugs do not mend the problem, only control it, and so must be taken for the rest of the pet's life.
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