Automated external defibrillators (AEDs) have become common in public spaces in Ireland. They are there to save the lives of people who have heart attacks. Even untrained bystanders can use these in an absolute emergency. Someone recently asked me if these devices can be used to save the life of a dog – or a cat – that had collapsed with a heart issue.
The short answer is “no”, but the long answer is more interesting, highlighting the significant differences between pets and people when it comes to heart disease.
Defibrillators work by first checking to see if there is an irregular heart rhythm (an arrhythmia) and if this is the case, the device applies an electrical shock to the chest, in the hope that this will jump-start the heart back into a normal rhythm. Heart attacks are the main cause of a sudden onset arrhythmia in humans, most commonly caused by coronary artery disease, when the arteries are blocked by a build-up of plaques of fatty deposits, including cholesterol. Pets don’t suffer from this type of heart disease, and they don’t collapse with this type of heart attack.
Heart disease in dogs and cats is completely different from this classic human condition. Pets don’t suffer from narrowing of the coronary arteries. Each species of pet has its own variant of what goes wrong with their cardiovascular system.
The most common heart condition in cats is cardiomyopathy, which means “disease of the heart muscle”. There are different types of cat cardiomyopathy, each with a different cause. One type – so-called dilated cardiomyopathy- can be caused by a deficiency of an amino acid called taurine. Fortunately, this is rarely seen these days, as all commercial cat food is checked to make sure that it contains enough taurine to protect cats. Another type of cardiomyopathy is inherited: this is more common in certain breeds of pedigree cat, such as Maine Coons. Anyone buying a kitten from a breed of cat predisposed to cardiomyopathy should ensure that the kitten’s parents have been screened with pre-breeding tests to ensure that they are free of this life-shortening condition.
Cat cardiomyopathy can also be caused by certain underlying diseases, such as hyperthyroidism (an overactive thyroid gland) or high blood pressure. The good news is that these underlying conditions can be successfully treated.
In most cases of cardiomyopathy in cats, the cause remains unknown: it just happens. Often owners notice no signs of illness at all: the disease is picked up when the cat has a routine visit to the vet. When the vet listens to the heart with a stethoscope, instead of the normal steady heartbeat, they hear an irregular rhythm. If the vet hears this, they will usually recommend an ultrasound examination of the heart: this allows the precise movements of the heart muscle to be seen, enabling the diagnosis to be confirmed. A normal heart contracts strongly and regularly, while a heart with cardiomyopathy moves feebly and irregularly.
If the disease is not noticed in the early stages like this, eventually signs of difficult or rapid breathing are likely to occur. There’s also a risk of a blood clot forming in the main blood vessel to the back legs, causing immediate paralysis: this is a painful, serious, and life-threatening condition.
Early identification and treatment of heart disease prolongs an affected cat’s life. Similar medication to that used in humans is prescribed, including diuretics, beta-blockers and calcium channel blockers. A complete cure is not possible: a heart transplant is the only way that full heart function can be restored, and this isn’t done in cats – or dogs – anywhere in the world.
Dogs commonly suffer from a wider range of types of heart disease than cats. As well as their own canine versions of cardiomyopathy, dogs often suffer from leaky heart valves (puppies can be born with these, or they can develop as part of the ageing process), and irregular heartbeats (it’s becoming common for dogs to have pacemakers installed to regularise the heartbeat in these cases). Dogs can also suffer from disease of the pericardium, which is the thin, clingfilm-type membrane that encases the heart.
As with cats, heart disease in dogs is sometimes diagnosed during a routine health check by the vet: a heart murmur or an irregular beat may be noticed. But compared to cats, it’s more likely that owners will notice that something’s wrong: their dog may not want to go for walks anymore, they may start to cough, or they may develop laboured breathing after an energetic run across the park.
Once an abnormality of a dog’s heart has been identified, it’s important to be as specific as possible about the precise nature of the problem. Again, further investigations may be recommended, such as x-rays and ultrasound, as well as ECG’s in some cases.
The genetic background to heart disease in dogs is highly significant: some pedigree breeds of dog are far more likely to suffer from certain problems compared to cross-breeds. Almost every single Cavalier King Charles Spaniel suffers from leaky heart valves, while giant breeds of dog (like Great Danes, Irish Wolfhounds, and Saint Bernards) are prone to cardiomyopathy. Again, puppy purchasers should ask breeders about the heart health of the parent dogs.
Once an accurate diagnosis of the heart problem has been made, medication can help. Similar drugs to those given to humans with heart disease are prescribed, either once or twice daily for the rest of the dog’s life. These are expensive drugs, especially for large dogs, costing several hundred euros a month.
Heart disease in pets is complex: it’s no wonder that veterinary cardiologists have become one of the more in-demand specialities in this rapidly changing veterinary world.