Heart Murmurs in Dogs and Cats Explained
Presenter: Nuala Summerfield BSc BVM&S DipACVIM(Cardiology) DipECVIM-CA (Cardiology) MRCVS
European and American Recognised Specialist in Veterinary Cardiology
About The Webinar
It is always a very worrying time when a heart condition is diagnosed in a pet. A better understanding of what is going on and demystifying some of the technical jargon can be extremely helpful for us coming to terms with the problem and planning how best we can help. In this fascinating presentation, Cardiologist Nuala Summerfield uses heart sound recordings, xrays, ECGs and heart scans to explain what heart murmurs are, what can cause them and how these associated conditions are diagnosed and treated.
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Nuala answers your questions
The original question is shown in red with Nuala's answer shown in black below it.
My german shepherd bitch was diagnosed with a grade 3 heart murmur at 6 weeks. She was examined at 6 months and the heart murmur had gone. Is it safe to breed her?
Heart murmurs in young puppies are common and most of these “flow” murmurs will disappear by 5 months of age. Flow murmurs are low grade (soft) and are not due to underlying heart disease. If your dogs’ heart murmur has definitely gone then it was very likely a flow murmur. However, if you are planning to breed your dog, the best way to confirm that there is no congenital heart disease present is for your dog to have a heart ultrasound (echocardiogram) performed by a veterinary cardiologist.
What do you hear when a dog has DCM?
In dogs with the early stages of DCM, there may be nothing abnormal to hear with a stethoscope. As the DCM progresses and becomes more advanced, it is more likely that an abnormality may be heard with a stethoscope. DCM is a heart muscle disease which causes the heart muscle to weaken and stretch. Therefore a heart murmur may not be present, as the valves in the heart may not be leaking even if the heart muscle is diseased. Only approximately 50% of dogs with DCM have a heart murmur, and this is usually due to a leaky mitral valve. Dogs with DCM may have an abnormal (rapid or irregular) heart rhythm (arrhythmia). It may also be possible to hear a gallop sound (third heart sound) which suggests that the heart muscle is not relaxing properly.
The pup with hole in the heart; did he go on to live happily and healthily?
Yes, most puppies and kittens with ventricular septal defects (VSDs / hole in the heart) have normal quality of life and lifespans, as long as the hole between the left and right ventricle is small and there are no other congenital heart defects present to complicate things.
Is a flow murmur something breeders should try to avoid when considering which breeding lines to select?
As long as the murmur is definitely a flow murmur, then it should not be a concern for breeding as flow murmurs are not due to underlying heart disease. However, if you are planning to breed your dog, or if your breeding line produces a lot of puppies with flow murmurs, the best way to confirm that there is no congenital heart disease present is for your dog to have a heart ultrasound (echocardiogram) preformed by a veterinary cardiologist.
Is it just a coincidence that dogs prone to heart disease are quite hyper breeds?
I think so, yes! No proven link has been found to my knowledge.
My 5-year-old male cat possibly has HCM. Definitely has a heart murmur. Has had 4 cardiac ultrasounds since 2011. Originally thought to have HCM, started on Atenolol. Further ultrasounds showed no evidence of HCM. Atenolol discontinued. Ultrasound last month (previous one 18 months ago) detected left ventricular thickening similar to the very first readings. So maybe he DOES have HCM? My question: Can left ventricular thickening alter over time? Can it be thick one reading, low the next, and then up again?? I know HCM is untreatable. Thanks. He also has a possible mitral valve leak. Is a domestic short hair1st was thick, then next 2 were normal, and then the last one was thick again.
It is possible that the thickness of the left ventricular walls of a cat with HCM can improve with atenolol therapy, although this doesn’t happen very commonly to our knowledge. A mitral valve leak is often present in cats with HCM due to systolic anterior motion of the mitral valve, and this causes a murmur. You could consider asking your vet to refer you to a veterinary cardiologist for a second opinion.
Do dogs and cats get heart attacks?
They do not get heart attacks in the same way as we humans do, as they do not suffer from coronary artery disease and high cholesterol, as we do. Cats and dogs can have sudden death due to abnormal heart rhythms, but although these may resemble a “heart attack”, they are not the same thing.
If owners exercise their dogs from an early age eg jogging with them, will this reduce the risk of acquired heart disease in later life?
No proven link has been found to my knowledge, although moderate regular exercise, a balanced diet and weight control has a variety of health benefits for your pet.
HCM is found in humans from birth. Why is it not found from birth or very young in cats?
Many kittens that unfortunately die at birth or shortly after birth never see a veterinary cardiologist for a heart investigation, or never have a post mortem examination to determine cause of death Therefore it is very possible that HCM may affect some of these kittens, but it is never diagnosed. We do see HCM in some very young cats from approximately 6 months of age.
Why don't some dogs with MVD which has progressed into CHF develop fluid accumulation in the lungs and others do?
Congestive heart failure (CHF) means that fluid accumulation has developed. In dogs with Mitral valve disease (MVD), this fluid typically develops in the lungs and is called pulmonary oedema. Some dogs can have advanced MVD with a loud murmur for a significant period of time before developing CHF, and in fact not all dogs with MVD do develop CHF in their lifetime. However, if your dog has developed CHF, this means there must be fluid in the lungs which causes rapid, heavy breathing. Fluid accumulation in the lungs from CHF will only resolve with diuretic therapy.
Why are some breeds more susceptible to heart problems than other breeds.
There is a genetic cause for heart disease in certain breeds, which has been proven.
At what point in MVD is Pimobendan usually started? When the dog becomes symptomatic of actual CHF or earlier?
In dogs with MVD, pimobendan in licensed for use when congestive heart failure develops. There is a study ongoing called the Epic Trial which is looking at whether pimobendan might help dogs with MVD before they develop CHF, but we do not have results from this study yet. So currently, it is typically started as soon as a dog with MVD develops fluid in the lung (CHF).
If a heart problem is diagnosed should all the tests you've described be performed?
Not necessarily. It depends on what type of heart problem is detected (e.g. a heart murmur or an abnormal heart rhythm etc.), and what symptoms, if any, your pet has such as heavy, rapid breathing, collapse etc. A veterinary cardiologist can advise you and your vet as to the best test(s) to start with to give the most useful information.
Why sometimes is a heart murmur heard only when we the dog is raised up on two legs?
This is not something I have come across personally, but if the heart murmur is soft and variable (i.e. only heard in certain positions), then it could be a flow murmur rather due to underlying heart disease. However, if there is any doubt, an echocardiogram (heart scan) should be performed to check that the heart is normal.
Is the blood test-Cardiopet-useful for monitoring mitral valve disease. My 8 yr old Gordon went for a scan demo with a cardiologist as a normal dog-no symtoms or HM but was found to have mitral valve dysplasia. I wondered if blood test may be useful and also the fact that this is more common in small dogs but she is obviously a big dog.
The Cardiopet pro-BNP blood test is not ideally suited to monitor your dogs’ mitral valve problem, especially as your dog has no symptoms. Regular auscultation with a stethoscope to monitor for a heart murmur by your veterinary surgeon, and follow-up heart scans (echocardiograms) with the cardiologist are the best way. Unfortunately there is no available blood test that will monitor your dog accurately over time in the way that a heart scan will.
My 15 year old border collie has a heart murmur. He's not on any medication but he pants a lot, should he be on anything to help?
It is important to make sure that the panting is due to heart disease before starting any heart medication, as there are lots of different causes of panting, especially in older dogs. The heart murmur may be due to a leaky mitral valve (which is common in older dogs) and may not be causing your dog any problem at the moment. I would advise that you discuss this issue with your vet. They may suggest a few diagnostic tests such as a blood test and a set of chest xrays as a good starting point to investigate the possible cause of your dog’s panting.
I rescue boxer dogs and last year we had an 8 month old pup come in, the week before he came to us he was neutered and the vet didn't notice any heart problems. 2 months later he died from heart failure, he saw a cardiologist 2 weeks prior when he developed fluid in his abdomen, the cardiologist suggested he had congenital DCM, is it possible that the other vet could have missed this?
Congenital primary or genetic DCM is rare, this means DCM that the puppy has at birth or develops very shortly after birth. Sub aortic stenosis is the most common type of congenital heart disease in Boxers. This does not look like DCM on a heart scan as the heart muscle becomes thicker, not dilated.
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a form of acquired heart disease with a genetic cause, seen typically in middle aged to older Boxers, although some Boxers younger than 12 months have been diagnosed with ARVC. It can cause the heart to dilate in some affected Boxers and is associated with life-threatening abnormal heart rhythms.
Myocarditis (inflammation of the heart muscle possibly due to a viral or bacterial infection) can cause the heart muscle to weaken and dilate. It can look like DCM on a heart scan and can occur in such young dogs. If it is severe enough it can lead to heart failure and death.
Nutritional deficiencies (taurine deficiency) is uncommon but can cause a dietary form of DCM, and can be seen in dogs fed a vegan / vegetarian diet for any length of time.
Also, some other congenital heart problems such as abnormally formed heart valves (valve dysplasia) and patent ductus arteriosus (PDA) can cause the heart to stretch as too much blood flows through certain heart chambers - but these congenital problems should cause a loud heart murmur.
May we have a reference concerning with low salt diet in heart murmur/disease prevention? What usually we have to do with this? Do special heart diets have a role to play in treatment?
The benefit of sodium restriction in dogs and cats with heart disease has not been proven. Some veterinary cardiologists recommend it and others do not feel it has any significant role to play in the treatment and prevention of heart disease.
However, there has been some research into the effect of diet on heart disease done at Tufts University in the USA. You can read their information for owners by following this link http://vet.tufts.edu/heartsmart/diet/restricted_nutrients.html
Your pet’s appetite may deteriorate as heart disease progresses and CHF develops. It is very important that your pet eats regularly and takes in sufficient calories and energy to optimize their quality of life at this time. Some pets find sodium restricted diets less palatable, so in these circumstances a sodium restricted diet may not be beneficial if the pet is reluctant to eat it. Be aware that some pet treats have very high salt levels and should probably be reduced or avoided in pets with heart disease and CHF.
When would she start using Aspirin in a cat?
What dose of aspirin would you recommend for cats with HCM for continual treatment?
The typical dose is 75 mg total dose of aspirin per cat given orally every 3 days. Aspirin must not be given daily to cats as they do not Another drug that may help with clot prevention in cats with heart disease is clopidogrel.
Anti-platelet drugs such as aspirin and clopidogrel are indicated when there is significant atrial dilation (typically it is the left atrium in cats), as this may predispose to clot formation in the dilated heart chamber. Your cat may not have any outward symptoms of heart disease, but if the heart scan shows atrial dilation, then anti-platelet medications will be recommended. If we see spontaneous echo contrast (or “smoke”) on a heart scan, which indicates that the blood is flowing too slowly in the heart chambers, this is a very concerning finding as it will often lead to a clot forming. In some cats, an actual clot will be visible in the heart on a heart scan.