Heart disease

Heart (cardiac) disease occurs in pet rabbits but is often underdiagnosed. As rabbits now live longer, more information has become available on what heart problems befall pet rabbits, and the best treatment options.

Rabbits can rarely be affected by heart disease that is congenital (they are born with it) but it is more common that they will have acquired disease of the heart muscle (cardiomyopathy) or heart valves (valvular degeneration) that develop later in life. Congestive heart failure is the condition that results from functional or structural heart disease, and it is commonly characterized by enlargement of the heart, and fluid build-up in the lungs.

Any rabbit, large or small can develop heart disease, at any point in their life, but the incidence increases as the rabbit ages. Large and particularly giant rabbits seem more prone to a type of heart disease known as cardiomyopathy (disease affecting the heart muscle), although the reason for this predisposition is unknown.

The signs of heart disease in rabbits mostly arise from the heart’s inability to effectively pump oxygen around the body causing an oxygen deficit in the tissues (hypoxia). This presents in a number of different ways. Signs of this include:

• Difficulty breathing (dyspnea) – the rabbit may show deep or rapid breaths, open-mouth breathing, discharge from the nose, or the sounds of breathing may be more noticeable.
• Hunched posture – the rabbit may sit with a hunched posture to help it breathe more easily, or because it feels unwell. It is best to let the rabbit sit in the most comfortable position and try not to disturb it too much until you see the veterinarian.
• Exercise intolerance – the rabbit may move around less and be reluctant to move. It may also breathe heavily after any amount of activity.
• Lack of appetite (anorexia) – the rabbit may lack energy and feel unwell, causing it to lose its appetite and stop eating.
• Pale or blue gums/lips (cyanosis) – lack of oxygen in the tissues can make them appear pale white, or blue tinged, the tissue is no longer looking healthy and pink.
• Weight loss – the rabbit may lose weight and muscle condition from a lack of activity and normal eating patterns.

As rabbits are prey animals, they will hide signs of illness for as long as possible, so by the time signs as seen the rabbit is likely to have been ill for some time. Rabbits are predisposed to stress and collapse from oxygen deprivation due to unique physiological features such as nasal breathing (they can only breathe effectively through their nose) and limited collateral circulation (the vessels in the heart have limited ability to bypass diseased areas) so great care must be exercised to address breathing problems quickly and calmly, seeking veterinary attention as soon as possible.

Your veterinarian will need to firstly take a clinical history from you and perform a clinical examination on your rabbit, including listening to their heart to see if they can hear a heart murmur or abnormal heart rhythm. If your veterinarian suspects heart disease, they will want to perform further diagnostic tests to confirm the diagnosis and identify how severe the condition has become.

Some tests include an electrocardiogram (ECG) to look at the electrical activity of the heart and to look for abnormal heart rhythm. Radiographs (x-rays) of the chest may be taken to assess the size and shape of the heart, and to look for excess fluid build-up around the heart and lungs.

Echocardiography and ultrasound of the heart may be used to look at the blood flow, contractibility of the heart muscles. Your rabbit may need to be sedated for some of these procedures.

For some heart conditions such as significant defects, or tumors there are few viable treatments for rabbits, but for other conditions such as congestive heart failure, medication is an option. There are a number of heart medications that can be prescribed for animals, but none are licenced for use in rabbits; however, they can be used under the veterinary cascade system when there is no other alternative.

The medication/s used will be specific to the type of heart disease. Some improve the strength of the contractibility of the heart, others remove excessive fluid which can build up in the chest cavity as a consequence of heart disease, and some dilate the valves in the heart; a combination of medications may be required. Your veterinarian will recommend the most appropriate treatment for your rabbit. Many of the medications are in tablet form, so you may need to crush the tablet and mix with water to syringe into your rabbit.

With regular checks by your veterinarian and the correct treatment, many rabbits can have a good quality of life. Heart disease is likely to shorten your rabbit’s lifespan, and the medication given will need to be continued for life, but with careful monitoring your rabbit can live comfortably with the condition.