During systole, they contract and pump blood out to the body. The rate and force of contraction of the heart and the degree of narrowing or widening of blood vessels are controlled by several hormones and by the autonomic nervous system the part of the nervous system that controls involuntary activity.
Heart of the Cat
The heart beats because of a tiny electrical current that begins in the sinoatrial node. Rhythmic electrical impulses or discharges from the sinoatrial node cause the contraction of muscle fibers in the heart. While an animal is at rest, the sinoatrial node discharges many times each minute; in a resting cat, it will discharge more than times per minute. Heart rate is also inversely related to blood pressure. When blood pressure increases, heart rate decreases; when blood pressure decreases, heart rate increases.
In heart failure, nerve endings that are sensitive to blood pressure changes called baroreceptors report the lower blood pressure to the brain, resulting in an inappropriately elevated heart rate. Unfortunately, this further injures the heart. Heart sounds are produced by the rapid acceleration and deceleration of blood and the resulting vibrations in the heart due to the circulation of blood. They can be heard using a stethoscope. In cats, 2 heart sounds can normally be distinguished. Heart murmurs are vibrations that can be heard coming from the heart or major blood vessels and generally are the result of turbulent blood flow or vibrations of heart structures such as part of a valve.
Murmurs are typically described by their timing that is, whether they occur during diastole, systole, or continuously , their intensity that is, whether they can be heard easily or with difficulty , and their location. Not every murmur indicates a heart disorder; for example, innocent murmurs are sometimes detected in healthy kittens less than 3 months of age. Arrhythmias are abnormalities of the rate, regularity, or site of heartbeat formation.
An arrhythmia does not necessarily indicate heart disease. Many arrhythmias are functionally insignificant and require no specific treatment. Some arrhythmias, however, may cause severe signs such as loss of consciousness due to lack of blood flow to the brain or lead to sudden death. Preview — Heart of the Cat by S. Heart of the Cat Sarafin Warriors 3 by S. Heart of the Cat Sarafin Warriors, 3 4. To see what your friends thought of this book, please sign up.
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See all 6 questions about Heart of the Cat…. Lists with This Book. Feb 18, Evelyn rated it liked it. This review has been hidden because it contains spoilers. To view it, click here. Erin rated it it was ok Oct 05, Deborah rated it it was amazing Sep 12, Angely rated it liked it Dec 13, Giants rated it it was amazing Jul 04, May Chevalier-martin rated it really liked it Feb 16, Linda Ewart rated it it was amazing Jan 11, Angelique Leal-hatim rated it liked it May 17, Sarah rated it it was amazing Feb 14, MBAButterfly rated it really liked it Feb 18, Sluggish blood flow within the heart sometimes allows blood clots to form.
Cats with blocked hind leg circulation have difficulty using those legs that ranges from a wobbly gait to complete rear leg paralysis. They are in varying degrees of hind leg pain; in fact, occasionally, pain is the only symptom. Due to reduced leg circulation, their feet and thighs may be cold to the touch. The size and exact location of these clots is unpredictable. So both legs might be effected or each to a different degree less commonly the right front leg As in human stroke embolisms , the problem may pass or improve on its own with time.
But those cats are at very high risk of developing the problem again. When these clots do not self-correct quickly, all tissue past the clot is robed of oxygen hypoxia and soon dies. But other things can cause aortic blockages. Problems such as cancer , hyperthyroidism or subsequent to a traumatic accident. Since it is a lot harder to miss leg paralysis, about three quarters of the cats — later found to have underlying HCM — were taken to their vet hospital because the owner noticed the paralysis — not because of suspicion of heart issues.
Traditionally, veterinarians would answer you that clots tend to form when blood moves slower than it should through the heart. Others would mention undue turbulence of blood passing through a heart that no longer retained streamlined passages designed for easy flow.
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Others would mention that disturbances in the pumping sequence arrhythmias give the heart and the blood within it a jerky irregular sloshy motion that makes clotting more likely to occur. That is all probably true. Other studies suggest that stored clot activation compounds ADP that are stored within those platelets are somehow liberated by the processes going on in the cardiomyopathy heart. I mentioned earlier that veterinarians believe that the underlying cause of hypertrophic cardiomyopathy and perhaps the other cardiomyopathies as well is a genetic defect in genes that direct how the heart muscle is constructed.
Due to these two proteins, when calcium in the cell rise the muscle cells contract, when calcium level falls, they relax. That knowledge should be of great value to veterinary cardiologists in judging the severity of HCM and its potential to affect cats that currently have no symptoms but carry the genetic defect for the disease. You can read that article here.
Chronic Valvular Heart Disease in Cats
New knowledge leads to new treatments. But I told you that humans also get HCM; and physicians had no better ways of slowing the progression of disease in people than veterinarians did in cats. So a company called MyoKardia in San Francisco got to work on it. What they needed was a negative ionotrope, a drug that would lessen the force of heart muscle contractions. For that, they used a mouse that had been bioengineered to also develop HCM. They found one, MYK which you can read about here. They have another, MYK, that may be helpful in dilated cardiomyopathy where increased heart contraction force is the goal.
MYK is now undergoing human clinical trials. Initial trials in HCM cats are said to show promise. You can read about that medication through the link at the top of this page or here. When either of the three forms of cardiomyopathy occur, it is usually the left lower chamber, the left ventricle, that experiences problems first. But the defective genes that affect the force of heart muscle contraction in the left ventricle are the same genes that affect the right ventricle.
So eventually, in cats, the right ventricle muscles often thicken as well increasing the pressure of blood moving to the lungs. If high blood pressure can be already be well documented in these early or mild cases, I would probably begin them on one of the ACE inhibitors mentioned below - but that's just my opinion.
A beta- blocker perhaps if the echocardiographer saw evidence of marked blood turbulence or "smoke". A T-4 test as well to be sure underlying hyperthyroidism was not a contributing cause for high blood pressure would be appropriate. Abnormal heart sounds arrhythmias , picked up with a stethoscope or EKG would add to those suspicions. Heart murmurs and abnormal lung sounds moist rales , heard through the stethoscope, would substantially reinforce that suspicion.
At this point, most vets would suggest a chest X-ray.
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Some would run an EKG as well. In these severe cases, the heart shadow on the x-ray will be enlarged and there is usually excess fluid in the lungs. Front line veterinarians, like me, with general diagnostic skills, are not as adept at recognizing the telltale signs of cardiomyopathies that are apparent to veterinary cardiologists who use these machines day in and day out.
Those folks are generally located in veterinary specialist centers and university teaching hospitals.
Introduction to Heart and Blood Vessel Disorders in Cats - Cat Owners - Veterinary Manual
Looking higher up, into the left atrium, they might even detect the blood clots thrombi I mentioned earlier. Elevated blood pressure due to kidney disease and or hyperthyroidism can cause similar changes. So your vet will want to rule those things out.
If you are just worried that your cat might have a genetic tendency to develop cardiomyopathies because of its breed or because parents or siblings developed the problem your vet might suggest genetic testing. At the moment, that test is available only for Maine Coon and Ragdoll cats. In the United States, the veterinary teaching hospital at North Carolina State University has the most extensive programs on cat and dog genetics and their links to disease.
Their genetics lab has many studies in progress and also offers a pet genetic testing service to the public. They have pickup stations around the world. A positive test result means that a cat is more susceptible to HCM than a cat that does not carry these defective genes. However the DNA test does not predict the age at which clinical onset might occurs or how severe the disease might become.