by: Kieran Borgeat BSc(Hons) BVSc MVetMed CertVC MRCVS DipACVIM DipECVIM-CA
Heart disease is common in dogs, especially as they get older. Interestingly males seem to develop heart disease younger than females. The two most common types of heart disease in dogs are mitral valve disease, or MVD for short and dilated cardiomyopathy, or DCM for short.
Mitral valve disease (MVD) is the commonest heart problem that we diagnose in the UK. Small to medium dogs tend to develop MVD, and although some breeds are at particular risk (the Cavalier King Charles spaniel, Chihuahuas, Whippets, Shi Tzu, Yorkshire terriers and Border collies), any small to medium size dog can develop the disease.
It is probably genetic, as we can see that it runs in families of dogs, but there is not yet a genetic test available to help screen for individual dogs who might be at greater risk. We know that dogs affected by MVD younger tend to have offspring who also develop the disease at a young age, so family history is important in knowing how likely your dog is to develop MVD, and what age to start asking your vet to look for signs.
Most dogs with MVD will develop a typical heart murmur – an abnormal noise that can be heard by a vet when listening to the chest with a stethoscope. Often, this heart murmur is present for some years before other signs are seen. Also, heart murmurs tend to become louder as MVD gets worse.
Once a heart murmur is as loud as the normal heart sounds (often referred to by vets as “Grade 3”), investigation is warranted to check for an increased heart size. We know that dogs with MVD and heart enlargement, even those with no obvious outward signs of a problem, will be at risk of developing a condition called heart failure – fluid accumulation in the lungs.
Treatment during the symptom-free or “asymptomatic” stage of MVD (before heart failure develops) has been proven to delay progression of the disease, and help dogs to stay free of heart failure for longer. For this reason, I recommend that vets check the heart size in dogs with MVD by taking a chest x-ray or performing a heart ultrasound scan.
The next most common heart disease in dogs is called dilated cardiomyopathy (DCM). Early, asymptomatic disease once again benefits from early medical treatment, so detection of this problem as early as possible is important. Unlike MVD, DCM affects larger breed dogs. Although any dog can potentially be affected, the most commonly affected breeds are the Doberman Pinscher, Great Danes, Irish Wolfhounds, Boxers, Newfoundlands, Scottish Deerhounds, and the Dogue de Bordeaux.
Detection of DCM in the asymptomatic stage can be difficult; over half of dogs with early asymptomatic disease do not have a detectable heart murmur. This means that vets may need to screen for the disease using blood tests or by performing a heart ultrasound scan. Dogs with a family history of DCM or unexplained, sudden death, especially higher-risk breeds, should be prioritised for screening.
As a specialist in cardiology, I often see the end result of both MVD and DCM – dogs brought to the vets with heart failure and breathing difficulties. Sadly, many cases are fatal. Although most dogs will respond well to treatment and have a good quality of life on medication, treatment needs to be lifelong, and sadly their prognosis is always poorer than dogs who are diagnosed and treated early in the asymptomatic stage, where we can slow the disease. For this reason, I recommend vets and owners are proactive in looking for heart disease in dogs before any obvious signs – in this way, we can help dogs to enjoy their lives and feel better for longer, even if they have a broken heart.
Kieran Borgeat BSc(Hons) BVSc MVetMed CertVC MRCVS DipACVIM DipECVIM-CA is an American, European and Royal College of Veterinary Surgeons (RCVS) Recognised Specialist in Veterinary Cardiology. He is the lead cardiology clinician at Langford Vets Small Animal Referral Hospital at the University of Bristol. Kieran has a passion for clinical work, teaching and research. He graduated from the University of Bristol in 2005 and worked in general practice for 6 years before undertaking a Residency and Masters degree at the Royal Veterinary College in London.