When your dog is coughing, it can be for different reasons like allergies or a respiratory infection. However, if your veterinarian detects a heart murmur or arrhythmia during a physical exam, then your dog might have heart disease.
The main types of heart disease in dogs
Valvular diseases are disorders of the heart valves located between the chambers of the heart and blood vessels. There are four heart valves: the tricuspid valve, the pulmonic valve, the mitral valve, and the aortic valve.
Some valvular disorders can be inherited like pulmonic stenosis and aortic stenosis, which refers to a thickening of the heart valves, making the heart work harder. Other valvular disorders can be acquired, especially in older pets and certain breeds.
The Cavalier King Charles Spaniel dog has a higher risk of developing mitral valve insufficiency. This can be due to mitral valve dysplasia – where the valve does not develop normally as a puppy – or mitral valve regurgitation, which is when the mitral valve begins to leak over time due to higher pressure on the left side of the heart. Valves can also become infected due to bacteria in the blood supply. This is called endocarditis.
Treatment varies based on the type of valve affected and the patient’s clinical signs. Young dogs with pulmonic stenosis might be good candidates for a surgery called balloon valvuloplasty, where a balloon-like tool is surgically placed into the valve, inflated, and thus opens the constricted valve.
Dogs with diseased mitral valves are more difficult to treat surgically. Their prognosis is typically good because the pulmonic valve is affected by pressures on the right side of the heart, which is a lower pressure area compared to the left side. The left side of the heart needs to be a higher-pressure area in order to pump blood to the entire body, and this means that the left-sided valves – mitral and aortic – can be more difficult to fix. Veterinary cardiologists can perform mitral valve replacement surgery, but this is not yet a common practice.
Heartworm disease is caused by a bite from a mosquito carrying heartworm larvae called microfilaria. These microfilariae go through several stages of development in the dog’s muscle tissues and then move into the bloodstream. Once they get to the heart, they develop into full-fledged worms. A dog can have as many as three hundred heartworms once diagnosed. The worms can obstruct the chambers of the heart and the main pulmonary artery, leading to heart failure.
Treatment can be painful, expensive, and time-consuming. Your veterinarian will prescribe an oral antibiotic for four weeks called doxycycline. If your dog is coughing and showing other clinical signs, then an oral steroid will be recommended as well. Three injections are given over the span of a month, and it is extremely important to keep your dog confined for several months. This means no running off-leash and no playing, which can be difficult for high-energy dogs. Adverse reactions to treatment are possible, and sudden death is a major risk factor when pets have heartworm disease. Prevention is key! Make sure that your dog is taking heartworm prevention from your veterinarian year-round.
One of the most important myocardial diseases is dilated cardiomyopathy or DCM. The walls of the heart become dilated and thin, affecting the heart’s ability to effectively contract. This is sometimes a genetic illness but can also develop in middle-aged to older dogs. Large breed dogs like Doberman Pinschers tend to be more likely to develop DCM. Recent evidence from the FDA suggests that there may be a link between grain-free diets and the development of DCM.
Older and overweight are the main causes of heart disease
Some causes of heart disease have been mentioned above, such as genetic factors and breed type. Overweight pets seldom develop the kind of heart disease that overweight humans might develop, such as coronary artery disease. However, being overweight does put a bigger strain on the heart’s ability to do its job. Extra weight also makes it harder to breathe, putting even more strain on the heart. Older pets are more likely to develop a valvular disease, especially small breed dogs like Chihuahuas and Pomeranians.
If your dog has the following signs, it may be heart disease.
One of the biggest signs of heart disease in dogs is coughing. When the heart must work harder to pump, fluid can back up in and around the lungs, causing coughing and difficulty breathing. Fluid can also build up in other places like the hind limbs. This is called edema. In certain conditions where the heart becomes enlarged, it can apply pressure to the mainstem bronchi and the trachea – or wind-pipe – which also causes coughing. Signs can also be very subtle, such as lethargy, depression, and exercise intolerance. Appetite can also be affected, causing weight loss, and further weight loss can be related to cardiac cachexia, which is a kind of muscle wasting due to heart disease. As heart disease progresses, it can cause fainting or collapsing – aka syncope – and in some cases, sudden death.