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THE FELINE HEART: Heart Murmurs
Hypertrophic Cardiomyopathy (HCM)
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The Truth About HCM and The Maine Coon Cat ... Click Here For Further Discussion Maine Coons are generally a healthy and strong breed and have evolved to survive the New England climate. Maine Coons, like all cats, are affected by Hypertrophic Cardiomyopathy (HCM), the most common heart disease seen in cats, whether pure bred or moggie. HCM is NOT exclusive to the MAINE COON CAT breed. It has been diagnosed in Ragdolls,Persians and other breeds as well. It is only singled out as APPEARING TO BE prevalent to these breeds, as these breeds have been heavily studied by animal geneticists. HCM is MORE common in the average feral cat as they can interbreed more rapidly. What is a Heart Murmur? Murmurs are a common finding not a symptom. Murmurs are extra heart sounds that are produced as a result of turbulent blood flow which is sufficient to produce audible noise. Murmurs may be present in normal hearts without any heart disease. These types of murmurs, often referred to as innocent or functional murmurs, usually cause no trouble for the patient. The loudness of the murmur reflects the amount of turbulence but is not evidence of severity. The presence or absence of a heart murmur in itself is not indicative of heart disease. The grade or loudness of the murmur is only sometimes related to the severity of the heart abnormality causing it. Heart disease can be present in the absence of murmurs. Murmurs are graded from I to VI based on the loudness. But loudness does not always mean heart damage or even that it is severe. Conversely many cats with severe HCM have barely detectable murmurs. The grade or loudness of the murmur is only sometimes related to the severity of the heart abnormality causing it. In cats, benign murmurs can sound exactly like murmurs in a cat with serious heart disease. In fact up to 35 % of cats with heart disease do not have any audible abnormalities on examination. "One big problem with heart murmurs is that they don't correlate exactly to the type or severity of heart disease. For instance, an owner of a dog with a quiet murmur might expect that the heart disease would be minimal compared to a loud murmur that should indicate more severe heart disease. It simply doesn't work that way. What's more important is the company the murmur is keeping. Are there clinical signs such as exercise intolerance, collapsing episodes, bluish mucous membranes? Does the dog have a rapid heart rate that's not stress related? The more of these signs, the more likely a heart murmur is significant." (Seattle veterinary cardiologist Jerry Woodfield) Murmurs related to Heart Disease may at times be difficult to distinguish from normal, innocent (also called physiologic or functional) murmurs. Innocent cardiac murmurs are believed to the related to normal blood flow in the circulation. Innocent murmurs are most common in young, growing animals. The prevalence of innocent heart murmurs in mature dogs (especially in athletic dogs) is undetermined. A common clinical problem is the distinction between innocent murmurs and murmurs arising from Heart Disease. The best determinant of what's going on with your cat's heart is Color Doppler Echocardiography. All methods of evaluation have limitations and may be associated with false positive and false negative diagnoses. It must be recognized that some cases of CHD (Coronary Heart Disease) fall below the threshold of diagnosis. In other cases, a definitive diagnosis may not be possible with currently available technology and knowledge. These limitations can be minimized by considering the following general guidelines:
(Source: OFA: Orthopedic Foundation For Animals)
(Sources: Dorland's Medical Dictionary, Medline Plus Medical Dictionary; Sandy Arora, Holisticat; Encinitas Pet Health Blog, The Drake Center for Veterinary Care; Michael La Corte MD Pediatric Cardiologist, Schneider Children's Hospital) What is an "Innocent" or "Functional" or "Benign" or "Normal" Heart Murmur? Low-grade heart murmurs of 1-3/6 are a common finding during the physical development of 50-75% or more (99% is likely more accurate) of normal, healthy kittens. 99% of murmurs are considered to be “innocent” or “functional” and completely normal. Therefore they are considered clinically insignificant. Murmurs are usually normal noises or sounds that can be heard as the blood is moving through the chambers of the heart. They can be audible at one point in time and then inaudible at another. Innocent murmurs also may disappear and then reappear. Most innocent murmurs disappear when a kitten reaches adulthood, but some adults still have them. When a kitten's heart rate changes, such as during excitement or fear, the innocent murmurs may become louder or softer. This still doesn't mean that the murmur is abnormal. This situation is common in a veterinarian's office and is referred to as the "white coat syndrome" which causes the kitten's heart to behave differently under stress. As in children, innocent heart murmurs do not affect the kitten's health and require no treatment. Innocent heart murmurs are those which do not impair the function of the heart and have no symptoms. In an otherwise healthy kitten (asymptomatic), any low intensity murmur detected during kittenhood is likely to be a normal part of their growing phase and that is why it is called "innocent" and therefore not clinically significant. llness, medications, and stress can cause heart murmurs as well (eg: fever). It can be very hard to determine if a heart murmur is present when listening to the chest of an excited kitten. When a patient is very excited and respiration is rapid (ie: in a new environment), causing the heart to pump faster and harder than normal, the blood turbulence can also be heard. The movement of the blood through the chambers of the heart is more easily heard in a young and/or thin-chested individual. Innocent cardiac murmurs are believed to be related to the normal blood flow during circulation. Innocent murmurs are most common in young, growing animals. A common clinical problem is the distinction between innocent murmurs and murmurs arising from CHD, Coronary Heart Disease. The noninvasive method of echocardiography with Doppler is the preferred method for establishing a definitive diagnosis for CHD. Examinations performed in mature animals are most likely to be definitive. Innocent heart murmurs are less common in mature animals than in young animals and are less likely to be a source of confusion. (Source: offa.org) As many as 50 - 75 % of all children will have an audible murmur at some point in childhood. Normal heart murmurs are heard in many children of all ages, but they are particularly common in young infants, children of pre-school and early school age (3 to 5 years), and adolescents. A normal murmur may be heard throughout childhood, or it may disappear at any time. In most cases, a normal murmur will disappear completely at some point in childhood, although some persist into adulthood. Certain conditions (such as fever, anemia, exercise, pregnancy, and changes in body position) may change the way a normal murmur sounds, making it easier or more difficult to hear. (Source: Angelo Milazzo MD, Pediatric Cardiologist and medical director of Duke Children's Raleigh Consultative Services Clinic & Dr. Dennis Clements MD, PhD, Chief of Primary Care Pediatrics at Duke Children's Hospital) Asymptomatic murmurs in children are extremely common. Innocent or normal murmurs occur in approximately 30-50% of children. They are heard most often in school aged children but are not infrequent in infants or adolescents. Innocent murmurs usually can be recognized by skilled ausculation and bedside maneuvers without the need for extensive and expensive diagnostic testing." (Source: Abraham Rudolph et al, Rudolph's Fundamentals of Pediatrics.) A heart murmur is an extra sound that the blood makes as it flows through the heart. Your doctor uses a stethoscope to listen to your heartbeat. When you have a heart murmur, your doctor can hear an extra whooshing or swishing noise along with your heartbeat. Heart murmurs are very common, especially in children, and are usually harmless. These normal murmurs are called "innocent" heart murmurs. There is nothing wrong with your heart when you have an innocent murmur. Up to 1/2 of all children have innocent murmurs. They usually go away as children grow. Adults can have innocent murmurs too. They can happen when your blood flows harder and faster than usual—during pregnancy, for example, or a temporary illness, such as a fever. They usually go away on their own. Innocent murmurs are often found in adults over 50 years of age. (Source: George Philippides, MD, Cardiology, Palo Alto Medical Foundation) Heart murmurs in kittens are as common as in puppies. Innocent heart murmurs are common and often disappear with age.(Source: David Sewell BVM&S BSc MRCVS, Feline Advisory Bureau Newsletter, Issue 16, 2005) Not all murmurs are clinically significant: Physiological murmurs can be heard secondarily to a modification in the viscosity or the velocity of blood flow without a change in cardiac morphology. For example, in cases of severe anaemia, hypoproteinaemia, hyperthyroidism and stress. Innocent or functional murmurs are typically mid systolic murmurs that are detected in puppies and kittens up to 16 or 24 weeks of age or in athletic adult dogs without any concurrent pathology (Wotton, 1998).(Source: Francisco Llabrés-Díaz, Davies Veterinary Specialist, Practical Radiography in small animal practice III, Cases With A Heart Murmur) Innocent murmurs are most common in puppies less than 16 weeks old. Kittens can have innocent, dynamic murmurs for a much longer time, even as adult cats. These innocent murmurs are always systolic (decrescendo), located over the left heart base, and should never exceed a grade 3/6. (Source: Nicole van Israel DVM CertSAM CertVC DipECVIM-CA (Cardiology) MSc MRCVS, Heart Murmurs in Puppies and Kittens, UK Vet Volume 10 No 6 July 2005. Your cat may have what is called an
innocent heart murmur. Many kittens and puppies can be born with a low
grade systolic heart murmur that is not
necessarily heart disease or a heart defect that requires surgical
correction, but rather a passing phase in the kittens or puppies
development. These types of innocent murmurs may disappear by 6 or 7
months of age. An innocent murmur is more likely if your kitten has no
other symptoms of heart disease such as coughing, Many young animals have soft murmurs due to flow through the great vessels, mild anemia, and reduced muscle and adipose tissue deposition around the heart and thorax. These innocent murmurs are usually soft (grade I-III/VI), systolic, they may be of short duration (less than the entire duration of systole), and may have a musical character over the heart base. Innocent murmur can change character with changes in body position, and they typically disappear by 6 to 12 months of age. Loud murmurs of long duration and those associated with stunted growth, altered pulse quality, or other evidence of cardiac limitation are often the result of cardiac malformation. (Source: John E. Rush, DVM, MS, DACVIM (Cardiology), DACVECC Cardiology, Tufts University School of Veterinary Medicine, Lecture Notes March 2006) It is imperative to appreciate that the presence of a heart murmur in a young animal is not pathognomonic for a congenital heart defect. Many young animals will have a low-grade systolic murmur that is the result of mild turbulence and is not associated with a congenital heart defect. These murmurs usually disappear by 6 mo of age in dogs and cats. Innocent murmurs are heard in the absence of any other demonstrable evidence of cardiovascular disease. High-grade systolic murmurs (grade IV/VI or greater) and diastolic murmurs are indicative of cardiac disease and should prompt further investigation. Heart murmurs are classified as follows: Grade I—the lowest intensity murmur that can be heard, typically detected only while auscultation is performed in a quiet room; Grade II—a faint murmur, easily audible, and restricted to a localized area; Grade III—a murmur immediately audible when auscultation begins; Grade IV—a loud murmur immediately heard at the beginning of auscultation but not accompanied by a thrill; Grade V—a very loud murmur with a palpable thrill, the loudest murmur that is still inaudible when the stethoscope is just removed from the chest wall; or Grade VI—an extremely loud murmur that can be heard when the stethoscope is just removed from the chest wall. (Source: The Merck Veterinary Manual) "People tend to hear the word murmur and they get nervous - 99% of murmurs in children are normal. So another name for an innocent or functional murmur is a "normal" murmur. In normal children and even infants, because they are thin chested and if they are cooperative you can actually hear the blood moving normally through the chambers of the heart. That is what an innocent or normal murmur is, just a noise (vibratory or musical) that you can hear of the blood moving through the heart in a completely normal way. It's usually present in childhood and it can come and go. If your child has a fever and your doctor listens, he may hear it, sometimes he may not. Generally by adult life it is no longer audible. It doesn't mean that the blood is not moving, but you don't hear it anymore. If we saw every child that had an innocent murmur we would have children wrapped around our office around the block." Key Findings of a Healthy Kitten: Normal Respiratory Rate, Weight Gain, Normal Femoral Pulses (meaning no blockage in aorta), Feeding Well, and Comfortable. Click here to watch video clips on the subject of Innocent Murmurs: http://www.youtube.com/watch?v=YJiYUsMW-wQ http://www.youtube.com/watch?v=O3vsxEvS-fU&feature=related (Source: Michael LaCorte, MD
Pediatric Cardiology What causes a Normal (Innocent) Heart Murmur? Many conditions, all within normal limits, may cause the blood to flow with turbulence leading to a heart murmur on ausculation. All these conditions do not indicate any abnormality and cause no ill effect on ones health. Some of the conditions causing an innocent heart murmur are: Small blood vessels to the lungs (pulmonary arteries). This is referred to as Peripheral Pulmonary Stenosis or PPS. While kittens were in their mother's uterus, there was very little blood flow to the lungs since kittens do not breathe prior to birth as they are supplied with oxygen from the placenta . This will cause the blood vessels to the lungs to be small (since blood flow causes blood vessels to grow). Once the kitten is born, blood flow increases tremendously to the lungs. Rapid growth of the pulmonary arteries will cause blood to be turbulent as it crosses these relatively small blood vessels and this turbulence will produce a murmur. "Innocent heart murmurs in healthy newborns are often related to pulmonary branch stenosis (peripheral pulmonic stenosis - a narrowing of the artery in one short segment), a condition that resolves by 6 months of age. Echocardiograms (heart ultrasound exam) showed that 50% of babies with a murmur had pulmonary branch stenosis compared with 12% of matched babies who had no murmur. The research group performed follow-up investigations at 6 weeks, 3 months, and 6 months. The murmur had resolved in 64% of babies at 6 weeks, in 84% at 3 months and in 98% at 6 months. The pulmonary branch stenosis had resolved in all babies by 6 months. The authors concluded that "Innocent heart murmurs in healthy babies born at term are mostly related to pulmonary branch stenosis, which resolves in two thirds by 6 weeks and in all by 6 months." (Source: Archives of Diseases of Childhood, Fetal and Neonatal Edition.) Blood Flow through the aortic valve (Still's murmur) and pulmonary valve (Physiologic pulmonary flow murmur): Blood flow across these two valves is audible in some kittens. This is not because there is anything wrong with these valves, but it may be due to the fact that kittens have a faster heart rate, which means that blood normally travels with a higher speed causing noise, resulting in the heart murmur. Also, kittens have thinner chest walls, which allows sounds to be more readily audible. It may sound very loud during fever, anxiety, or exercise. The heart murmur may eventually be inaudible as the chest wall gets thicker and the heart rate slows down. (Sources: The Children's Heart Institute; Pediatric Cardiology, University of Chicago)
If a kitten has an innocent heart murmur, then the heart is normal and there is nothing to outgrow. However, the murmur may after a few years be no longer audible as the chest wall gets thicker and the heart rate slows down. What are the Signs and Symptoms that might indicate an Abnormal , Pathological Murmur? Murmurs that are 4/6 or greater, particularly when accompanied by symptoms should prompt further investigation. Symptoms: weakness, depression, lethargy, coughing, weight loss, difficulty breathing, anorexia (not eating), fainting spells, abdominal distention (fluid), possible cyanosis (blue tinge to tongue and mucous membranes), exercise intolerance, vomiting, collapse, failure to thrive and grow. A murmur, which indicates there is something abnormal in the heart or a major artery is, called a not-innocent, not-functional, or organic murmur. A narrow valve, a narrow artery, a leaking valve, or a hole in the heart, usually causes it. According to the American Heart Association congenital cardiovascular defects are present in about 1 percent of live births and this is pretty much the same situation you have with animals. A narrow valve A narrow artery A leaking valve A hole in the heart A hole in the heart is called septal defect. If it is between the upper cardiac chambers, it is called Atrial Septal Defect (ASD), and is called Ventricular Septal Defect (VSD) if it is between the lower cardiac chambers. The importance of septal defects depends on their size and site. Ventricular septal defects can vary from small holes, which may cause a heart murmur but no symptoms and usually close by themselves, to larger holes that cause symptoms. Ventricular septal defects never get bigger and sometimes get smaller or close completely. A smaller hole may actually make a louder noise than a large hole, and the murmur may get louder as the ventricular septal defect closes. Those with small ASDs that don't close and don't cause symptoms are healthy and don't need treatment. Most small ventricular septal defects will not require an echocardiogram as they tend to close, but often moderate or large ventricular septal defects will need to have at least one echocardiogram to provide the cardiologist with a complete picture of the defect. (Sources: Cat Health Guide, Cincinnati Children's Hospital Medical Center, Harry Kaplovitz MD Pediatric Cardiology, Jared C. LaCorte M.D., FAAP, FACC Pediatric Cardiology Metro Pediatric Cardiology) What is Hypertrophic Cardiomyopathy (HCM)? Cardiomyopathy is the name applied to an abnormality of heart muscle function. The heart's pumping ability is diminished, resulting in such signs as inability to exercise, fatigue, fainting, fluid collection in the lungs, abdomen, and limbs, or emboli (clots that arise in the heart and travel to the kidney, brain, or legs). The causes of cardiomyopathy include genetic predisposition, infections, toxic causes (drugs and chemical compounds), specific dietary insufficiencies, and unknown causes. Whereas some cases are entirely reversible, others are not and are treated with various levels of success. HCM is found in many cat breeds and in non-pedigree cats. It has been studied in Maine Coons, but it is by no means confined to that breed. It is only singled out as appearing to be prevalent to these breeds, because these are the breeders who are doing the most to try to trace, document, and prevent carrying the genes on in their lines. HCM is more common in the average feral cat as they can interbreed more rapidly. (Source: The Feline Welfare HCM Page) Hypertrophic Cardiomyopathy (HCM) is the most common form of acquired heart disease in the cat, and it predominantly affects young to middle-aged male cats. It is the enlargement of the left ventricular wall, papillary muscles, and septum, which limits the size of the left ventricular chamber. This type of enlargement prevents the heart from expanding (to receive blood) adequately, thus decreasing cardiac output. The incidence of blood clots is somewhat greater than in other forms of cardiomyopathy. The dynamics of this clotting directly relate to the restricted ventricular filling, which allows the blood to remain for a longer period of time in the left atrium, thereby having a greater chance of forming blood clots. HCM can be diagnosed by ultrasound scanning by an experienced ultrasonographer. The age when HCM can first be diagnosed is variable, but after two years of age it will probably make its appearance if it is going to develop, but this is not guaranteed. A negative scan is no guarantee that a cat has not inherited HCM. Cats can be tested negative and still die. Others can be tested positive and live to a ripe old age, or never have had it. The advice being commonly given at present is not to use known HCM positive cats for breeding, and to test existing progeny of positives. HCM unfortunately is progressive and incurable, but treatment can slow its development and make the cat more comfortable. Depending on the rate of development and the medical care given, a cat with HCM can live happily for several years. Serious complications are heart attacks and thrombosis, both of which are likely to be fatal. (Source: Cornell Book of Cats, 1989, Mordecai Siegal and Cornell University, Chapter 20 - The Internal Cat, pp. 192-3.) How does Gender and Age relate to the development of HCM? The natural history of FHCM in Maine coon cats is similar to human FHCM, in which the disease commonly becomes evident during childhood or adolescence and progressively worsens during young adulthood. In our colony, most cats first had definitive evidence of HCM between 8 and 24 months of age. The disease usually reached its nadir between 1.5 and 3 years of age. Cats generally become mature adults between 12 and 18 months of age, so these periods correspond to adolescence and young adulthood. In a few female cats, however, the disease was not evident until 3 years of age. HCM in our cats progressed to severe HCM and death more commonly in males than in females. (Source: Familial Hypertrophic Cardiomyopathy in Maine Coon Cats : An Animal Model of Human Disease Mark D. Kittleson DVM, PhD, Kathryn M. Meurs DVM, PhD, Marcia J. Munro BA, Judith A. Kittleson RN, Si-Kwang Liu DVM, PhD, Paul D. Pion DVM and Jeffrey A. Towbin MD, 1998) What are the Causes of HCM? The cause of primary (true) HCM is a genetic mutation in the heart muscle cell itself which interferes with its ability to contract and pump blood. Certain problems can cause HCM as a secondary problem such as Hyperthyroidism, Hypertension and Chronic Kidney Disease. In these cases when the primary problem is treated, the HCM usually resolves. Other types of Heart
Disease occasionally occur in cats. What are the Signs, Prognosis, and Treatment for HCM? Signs indicative of HCM include labored and noisy breathing, shortness of breath, lethargy, loss of appetite, coughing, and possible lameness or paralysis of the hind legs due to arterial blood clots. Prognosis is fair if arrythmias and clots can be controlled medically. Treatment by the veterinarian consists of dosages of negative inotropes (substances that affect the force of muscle contractions), diuretics, and carefully controlled doses of aspirin. (Source: Cornell Book of Cats, 1989, Mordecai Siegal and Cornell University, Chapter 20 - The Internal Cat, pp. 192-3.) What Tools are currently available to Test for and/or Diagnose HCM?
The cat's heart and circulation are examined using a stethoscope. Any heart murmurs are identified, timed, localised and graded (grade 0 – 6). The heart rhythm is examined closely. Abnormal heart rhythms can occur without murmurs in HCM. Quiet murmurs may be difficult to detect in a noisy room or in a cat which purrs or fidgets. Some murmurs may increase or alter at different heart rates, or due to stress or excitement. If a significant murmur is detected, the condition should be looked into further. Auscultation does not provide a conclusive diagnosis as further investigations are required.
This test is normally indicated if an abnormal heart rhythm is detected in your cat . This test displays an electrical picture of the heart functioning. It helps detect changes in rate and rhythm (arrythmias), heart chamber size, and electrical axis. The
electrocardiogram is a noninvasive test. The heart's electrical activity
is recorded by attaching small contact electrodes to the limbs and chest
wall. This allows recording of electrical activity onto paper printed from
the electrocardiograph machine. As with all tests, the ECG is not 100 percent accurate.
With this heart test, strength of heart contractions are observed. Chamber size and thickness of the heart muscle walls, and valvular function are measured. This test can also be used to detect heartworms and tumors. Two-dimensional echocardiography (ultrasound examination of the heart) allows visualisation of a “slice” through the heart in real-time. M-mode and Doppler (spectral, with or without colour flow mapping) echocardiography allows measurements to be taken and compared with normal values.This test is the most sensitive in determining how well the heart is functioning. In some cases, it is difficult to be certain whether a cat has mild disease. Veterinary cardiologists normally carry out Doppler examinations as this is a very skilled technique which requires considerable expertise and experience. Ultrasound is a non-invasive procedure. However, ultrasound waves need good contact with the skin, so in order to perform a cardiac scan, it is usual to clip a small section of hair on both sides of the chest, just behind the elbows. Some cats may require a sedative for the ultrasound to be performed. An Echocardiogram performed on a young animal has limitations and can yield false and/or inconclusive results because the animal is still growing. Therefore, the heart and its valves and arteries etc are still growing and maturing. OFFA recommends that echocardiograms will have a better likelihood of yielding definitive results in a mature adult animal. Echocardiographs are not a fool proof way of identifying and eliminating HCM. HCM can occur at any age and one echocardiogram can not guarantee that a cat will not develop HCM at a later date. Ideally cats would have to be tested on a yearly basis however this can be very costly (i.e. Consultation Fee $165 + Echocardiogram $480 + Travel and Accomodations Costs as most veterinary cardiologists only operate out of main cities.) Some mildly affected cats where changes in the heart can be mimimal will escape detection Since the trait has variable expression, not every affected cat will have echocardiographic evidence of HCM. It is therefore possible for a cat to test negative for HCM on ultrasound, and yet still carry the defective gene and pass it to offspring. It is possible for spontaneous mutations to occur in cats from normal parents. These cats may then pass on their mutation to offspring. As, it is in humans there are over 130 gene mutations in 10 genes have been found to cause the disease.
A cat that dies suddenly or dies from HCM should have a necropsy. Most cats with HCM will have a heart that weighs more than 20 grams and most cats with severe HCM will have a heart that weighs more than 30 grams. Myocardial fiber disarray, the hallmark microscopic heart muscle abnormality seen in humans with familial HCM is seen in all Maine Coon cats with HCM. Unfortunately, most veterinary pathologists are not trained to recognize this lesion. (Source: Feline Hypertrophic Cardiomyopathy: Advice for Breeders Mark Kittleson DVM, PhD, DACVIM (Cardiology), Rebecca Gompf, DVM, MS, DACVIM (Cardiology), Susan Little, DVM, DABVP Feline May 2004)
The genetic basis for HCM is under study. In humans there are over 130 genetic mutations which have been identified in conjunction with HCM. In humans, 10 principal genes have been identified, along with about ten times that number of variants. A study by Dr Kittleson has identified one dominant gene with a variable expressivity in one group of Maine Coon cats, but in some other cases, a traceable dominant pattern of inheritance is not obvious. Katherine Meurs of Washington University has discovered a mutation on the cardiac myosin binding protein C (MyBPC) in Maine Coons. This mutation correlates with a similar mutation in people which causes late onset HCM. To date, over 35% of Maine Coons tested carry this gene but according to statistics, only 3-5% of Maine Coons will go on to develop clinical signs of the disease. It seems that even the geneticists are unable to predict the correlation between the test and those cats who will eventually develop clinical signs of HCM. Note: A negative result does not mean that the cat being tested doesn’t have HCM. It does not guarantee your cat will or will not get HCM, for as in humans it is suspected that there are hundreds of gene mutations that can cause the disease. HCM has also been shown to skip one or more generations which complicates the situation even further. "For genetic testing of hitherto unaffected relatives of an HCM patient, further considerations arise. Not all persons with an HCM genotype will have HCM. Indeed, in families where the mutation has low penetrance, the cardiac phenotype may skip one or more generations." "In HCM as in many other genetic diseases, the basic hurdle is that any of a large number of different mutations in a large number of different genes may be causative. A clinically applicable mutation detection method must therefore be not only reliable and rapid but also able to "interrogate" a large number of DNA sequences."(Source: Cardiology Presented and Explained by Robert Mathews MD) "False positives and false negatives occur however, with some “gene test negative” cats developing the disease whilst some “gene test positive” cats don’t" (Source: Boarders Veterinary Cardiology Services) "The development of HCM can appear to skip several generations, and so probably could be inherited from cats which are thought to be negative. Eliminating breeding lines which could possibly be implicated may seriously damage a breed gene pool while doing little towards eliminating the disease." (Source: The Feline Welfare HCM Page) News about the HCM Genetic Test: Article from University Clinic Giessen June 2nd, 2008
The veterinarian clinic of
the Ludwig Maximilians University in Munich has carried out a study
about the two genetic tests for HCM available in Germany for
Maine Coons. The survey showed that Maine Coons with HCM are just as
frequently positively tested in the gene test, as Maine Coons without HCM.
Therefore the results demonstrate that
the genetic test does not bring anything.
Below, you find the results of the survey that were
presented on the previous weekend at a congress for veterinarians in
Giessen. Does HCM testing provide any guarantees that my cat will never be afflicted with HCM? Based on the research available on the subject, it is apparent that there are currently no fool proof Diagnostic nor DNA tests that would enable us to effectively identify and completely eliminate this disease from The Maine Coon or any other breed's gene pool at this time. In the event that your cat begins to show any signs indicative of HCM as noted above, it is recommended that further physical examination by a veterinarian be done. If upon examination, HCM is suspected, then your veterinarian will probably recommend further diagnostic testing. In the event that HCM is confirmed, treatment with various medications will be necessary to control the disease. One must keep in mind that health problems exist in all species of animals including humans. With this being said, Maine Coons are still considered to be one of the healthiest and most natural of purebred cats. Cardiomyopathy Update: Feline Panleukopenia (Parvovirus) Vaccine Implicated in Development of Cardiomyopathy "Cardiomyopathy is an autoimmune disease, and vaccines are major causes of autoimmune disease. In my opinion, these connections are too close to be coincidence alone." ~ Don Hamilton DVM There is still another syndrome
associated with parvoviruses, one that occurred first in cats, and later in
dogs. Cardiomyopathy is a disease of the heart muscle. The muscle may either
weaken and stretch (dilated cardiomyopathy), or it may thicken greatly (hypertrophic
cardiomyopathy). Either condition will limit the heart’s ability to pump blood.
Cardiomyopathy is often fatal. Disclaimer: The opinions expressed above are our opinions based on our experience and research. We are not veterinarians, nor do we claim to have any medical training or to be an expert in feline health issues. As reputable breeders we feel it is our responsibility to continuously educate ourselves about all facets of breeding Maine Coons. In addition, to our many years of breeding experience, this knowledge helps us to maintain quality, healthy breeding stock with the goals of raising the healthiest kittens possible and improving the Maine Coon breed as a whole. |
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