In the early stages of heart disease, cats often don’t show any signs that they are unwell – they manage to cope due to well developed compensatory mechanisms and by altering their activity levels. This often means that it is not until the disease is well advanced that we realise there is a problem and diagnose a cardiomyopathy.
Most of the clinical signs are associated with part of the underlying pathology and problems that can develop secondarily to the heart disease. These include:
- Anorexia (not eating)
- Weakness/ lethargy
- Difficulty breathing, increased respiratory rate
- Paralysis of the back legs
The major long term concerns with all types of cardiomyopathy are:
Development of congestive heart failure – Breathlessness and lethargy are the most frequently noticed signs of congestive heart failure and result from failure of the heart to efficiently pump blood.
Thromboembolic disease – Altered flow of blood in enlarged heart chambers increases the risk of blood clot formation within the heart called a thrombus. If parts of the thrombus become dislodged, they can travel in the bloodstream and block smaller blood vessels. These travelling blood clots are called emboli and the most common place for them to lodge is at the bottom of the aorta, which is the largest artery in the body. This results in obstruction of the blood supply to the back legs, which is very painful and can lead to paralysis. This blockage is commonly referred to as a saddle thrombosis. Although some cats may recover with appropriate treatment, this is a potentially fatal complication of any cardiomyopathy.
Hypertension – High blood pressure or hypertension is a possible complication seen in many cases of hypertrophic cardiomyopathy. This may result in spontaneous bleeding, such as nose-bleeds or hemorrhage within the eye and may also cause retinal detachment and blindness. This may be noticed as a sudden loss of vision and widely dilated pupils. This is an emergency situation since the blindness will be permanent unless the retina is reattached within a couple of days. Drugs that lower the blood pressure may be used to treat cats with this problem. Measuring blood pressure in cats is challenging due to their small size and the rise in blood pressure with stress, which makes interpretation of results difficult. For these reasons, hypertension may be detected only after a problem has occurred.