Heart Medications For Pets Explained
Heart disease does not always mean that the heart is failing. Many pets with heart disease show no signs of being poorly and are able to lead reasonably normal lives without medication. However, most heart conditions do worsen over time and once symptoms develop, treatment will most likely be required for the rest of your pet’s life.
What are the early signs of heart disease in pets?
In the early stages of heart disease, there may be no outward signs of illness and your pet may just need to have regular check-ups with the vet to monitor the condition. However, in most cases, the disease does progress and treatment may be necessary to relieve the signs of the heart disease and slow down the rate of progression of the condition.
Management of heart disease in pets requires a combination of:
Drugs to remove excess, retained, fluid in your pet’s body
Drugs to either change heart rate or improve the strength of the heart
Dietary changes
Lifestyle changes, for example, alterations to the daily exercise regime
In order to understand how various conditions affect the heart, it is useful to consider the anatomy of the heart and how it functions.
How does the heart work?
The heart is a hollow, muscular organ and in mammals and birds, it is divided into four chambers: the left and right atrium, and the left and right ventricles.
Blood from the body flows through large veins called the vena cavae into the right atrium. When the right ventricle relaxes, blood in the right atrium moves through the tricuspid valve and into the right ventricle. When the right ventricle is almost full, the right atrium contracts pushing additional blood into the right ventricle.
The right ventricle then contracts, pushing blood through the pulmonary arteries, which lead to the lungs. In the lungs, the blood absorbs oxygen and releases CO2. The blood then flows through the pulmonary veins into the left atrium.
When the left ventricle relaxes, the blood in the left atrium pours through the mitral valve into the left ventricle, and when the left ventricle is nearly full, the left atrium contracts pushing additional blood into the left ventricle. The left ventricle then contracts pushing the blood through the aortic valve into the aorta, and this blood carries oxygen to all of the body except the lungs.
In summary, the function of the heart is to pump blood. The right side of the heart pumps blood into the lungs when oxygen is added to it and carbon dioxide (CO2) is removed, and the left side of the heart distributes the blood to the rest of the body, where oxygen and nutrients are delivered to tissue, and waste products (including CO2) are transferred to the blood for removal by other organs such as the kidneys and lungs.
Is heart disease common in pets?
Heart disease is a relatively common problem in some breeds of dogs such as the Cavalier King Charles Spaniel (who are prone to Mitral Valve Disease - MVD), and Dobermans (prone to dilated cardiomyopathy - DCM).
What is MVD?
In MVD, which affects cats as well as dogs, the valve between the left atrium and left ventricle thickens resulting in the valve not being able to close properly and blood leaking back through it. This leak is heard as a heart murmur using an instrument called a stethoscope. This causes the heart to have to work harder to pump blood around the body, and as a result of this, the heart enlarges over time.
The heart may be able to cope with this over a long period of time; however, at some point, the pressure becomes so high that blood accumulates in the blood vessels of the lungs causing fluid to leak into the lungs and Congestive Heart Failure develops.
What are the symptoms of MVD?
Symptoms of MVD include coughing which is usually worse after lying down, or at night; slowing down on walks or lethargy in general, a faster respiration rate than usual, weight loss and collapse.
How is MVD treated?
There is currently no cure for MVD, and in the early stages of the condition, treatment may not be needed, but once the heart enlarges, treatment with pimobendan can delay the onset of heart failure. If signs of heart failure are already present, then treatment may also include a diuretic to remove excess fluid from the body, and additional drugs to reduce scar tissue formation.
What is DCM?
Dilated Cardiomyopathy (DCM) is a primary disease of cardiac muscle that results in a decreased ability of the heart to generate pressure to pump blood through the vascular system. The causes of DCM have been suggested as nutritional, genetic and infectious diseases. The dilation of all 4 chambers of the heart may occur and as the ability of the heart to act as a pump diminishes, clinical signs relating to this develop such as a reduced delivery of oxygenated blood to the body (lethargy, weight loss, collapse), and congestion of blood in the lungs (coughing, increased respiratory rate, abdominal distension).
How is DCM treated?
Treatment of the condition is directed at dilating the peripheral blood vessels to decrease the workload of the ventricles of the heart, eliminating congestion in the lungs and controlling heart rates. Drugs which may be used to achieve the above are again pimobendan, and ACE-inhibitor such as benazepril, and antiarrhythmic drugs e.g. sotalol.
In summary, there are several conditions which come under the heading of “Heart Disease”, although we have just chosen to concentrate on DCM and MVD today as these are the most commonly seen ones in general practice in the UK. Treatment options may vary depending upon clinical signs, age of the dog, and response to tried treatments, and can help many such affected pets to go on for a long time with a good quality of life.
Dr Rachel Louise Keane BVSc BSc MRCVS says you need to remain vigilant for symptoms of heart disease in your pets.
“The important thing is to be observant of your pets, and if they do start to display signs of a diminished appetite, lethargy, weakness and coughing, particularly if this is worse at night or when lying down, then please don’t delay but get your pet booked in with your vet right away, for the sooner necessary treatments are initiated, the better the prognosis."
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Sources
Canine Heart Disease and Nutrition Part 1 | Daily Vet | PetMD
Heart disease in dogs | The Kennel Club
https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub/conditions/heart-problems-in-dogs
Heart disease in your dog - Bishops Stortford Vets (stortvet.com)