Feline Dilated Cardiomyopathy
Until recently, cats presented with two types of cardiomyopathy:
Dilated cardiomyopathy was very prevalent in the UK and rest of the world in the 80's and 90's. After extensive research, it was found that a world wide deficiency of Taurine (an essential amino acid) in commercial cats foods was the cause. Food manufacturers have since added Taurine to all their products and the disease has made a marked decline in incidence.
Most cats present in left sided heart failure with fluid in the lungs (pulmonary oedema) with some if not all of the following symptoms:
- Shortness of breath
- Rapid breathing
- Coughing (not as much as in dogs in heart failure)
- Weak pulse
- Pale gums with poor refill
- Jugular pulse
- Sudden hindleg lameness from an embolus (see below)
Cats with dilated cardiomyopathy have very enlarged heart chambers with thin walls that can't pump effectively.
With this heart enlargement, the valves between the atria and ventricles get "pulled apart" so a gap appears in the middles of the valve allowing blood to shoot up into the right and left atria (see heart valve disease)
The left atrium becomes very enlarged due to leaking of the mitral (left a-v) valve.
Cat blood clots approx. 15 times quicker than human or dog blood. Inside the dilated left atrium, blood sludges around not knowing where to go. On cardiac ultrasound, a "London fog" appearance in the left atrium can sometimes be seen. In a number of cats a solid blood clot forms in the left atrium which looks like a billiard ball bouncing around inside the left atrium.
The blood clot (embolus) leaves the left atrium into the left ventricle and out the aorta to wherever fresh blood is delivered. Small clots can go to the brain, kidneys, foreleg, parts of the intestines or elsewhere. Most clots are pretty big and tend to travel down the aorta missing the smaller outlets until they reach the end of the aorta where it splits in 2 to supply the lower part of the body.
This is called a saddle thrombus and cats have acute hindleg paralysis which very quickly get very stiff, swollen and very painful due to the lack of blood supply.
Symptoms of embolus
Cats develop a very sudden illness depending on where the embolus goes and blocks off the oxygen rich blood supply to vital organs
- Foreleg lameness/nerve deficits (can look like radial nerve damage - a "dead leg")
- Acute painful kidney failure
- Acute painful intestinal damage
- Acute painful hindleg paralysis (often mistaken for a motor vehicle accident)
- Accompanying heart failure symptoms
Early cases can present with mild symptoms of general weakness, lethargy, and slight shortness of breath. Most cats have a heart murmur and a rapid heart and respiratory rate as the first detectable symptoms.
Severe cases can present in fulminate heart failure with or without a serious life threatening blood clot (embolus).
Diagnosis is based on symptoms, clinical examination, xrays and ultrasound examination.
- An enlarged globular or "ugg boot" shaped heart
- Distended pulmonary arteries and veins
- Pulmonary oedema
- Pleural effusion (fluid between the lungs and the chest wall itself)
Cardiac ultrasound (echocardiography)
- Dilated heart chambers
- Poor contraction of the ventricles
- Sometimes a visible embolus "billiard ball" or "London fog" in the left atrium
See an ultrasound video of a human heart with an embolus in the left atrium.
This was a very serious and frustrating disease to treat.
Conventional therapy involved treating the heart failure by using of diuretics (e.g. Frusemide) ACE inhibitors (e.g. Captopril) and anti-clotting drugs (e.g. Aspirin).
Aspirin is safe to use at low doses and only twice a week. It was thought that it would prevent embolus formation but this has recently been disproved (Mark Kittleson's work) and is no longer used.
Cats with acute saddle thrombus formation have a grave prognosis. If the cat can get to a specialist centre quickly for the clot to be dissolved by using special intravenous drugs, it stands a better chance of survival.
However once the muscles start to die off and build up a lot of waste products, dissolving the embolus results in these breakdown products entering the circulation and causing severe life threatening kidney damage. So fixing one problem leads to another.
Oral administration of Taurine resolved a number of cases with hearts sometimes returning to normal.
Preventing embolus formation has proved very difficult in cats. Many cardiac specialists have saved cats only to have another clot episode a few months later. This happens despite the use of Heparin and/or Aspirin.