Heart Disease and Heart Murmurs in Cats
Heart murmurs are caused by a disturbance to normal blood flow within the heart on
in the major blood vessels exiting the heart. They can occur as a result of heart
disease, or other underlying disease e.g. anaemia. Occasionally we detect heart
murmurs that are incidental. This often occurs in very young animals and the murmur
may disappear as they get older. Heart murmurs are often graded on how loud they
appear, but the grade of heart murmur does not necessarily correlate with the severity
of the heart problem.
Occasionally we hear abnormal heart rhythms. This can either be because the heart is
beating irregularly or occasionally cats develop what we call a ‘gallop’ rhythm. This
is where we hear a third heart sound in addition to the normal two sounds heard with
every beat. Cats with irregular rhythms usually require an ECG to assess what the
cause of the irregular rhythm is. Cats with a gallop rhythm almost always have
significant heart disease, which warrants further work-up.
Heart disease (cardiomyopathy) can be divided into four subtypes:
Hypertrophic Cardiomyopathy
Dilated Cardiomyopathy
Restrictive Cardiomyopathy
Intermediate Cardiomyopathy
The most common type of heart disease in cats is Hypertrophic Cardiomyopathy
(HCM). Dilated Cardiomyopathy used to be more prevalent as it was brought on by a
taurine deficiency in the diet. Cat foods today are supplemented with taurine.
We are not sure why some cats develop HCM. In some breeds it appears to be
hereditary, e.g. Maine Coone. HCM can occur secondary to another underlying
disease e.g. hyperthyroidism, or high blood pressure as a consequence of kidney
problems.
In HCM, the heart wall of the left ventricle (the main pumping chamber in the heart)
thickens. This leads to a smaller chamber inside the heart for the blood to fill and so
less blood is pumped out of the heart with every contraction. As the disease
progresses, the heart becomes less and less effective and eventually the heart is not
able to pump enough blood through to satisfy demand, this leads to heart failure.
Commonly breathlessness, lethargy and loss of appetite are noted. Cats will often not
develop any obvious symptoms until heart failure is severe, as they tend to moderate
their behaviour initially to reduce their body’s oxygen demand, e.g. by sleeping more.
Signs of heart disease may come on very suddenly (hours to days), but the underlying
heart disease has usually been present for a considerable time.
As heart disease progresses the left atrium (the chamber in the heart which supplies
blood to the left ventricle) also enlarges. Blood in the enlarged chamber does not flow
properly and very occasionally clots can form here. Pieces of the clot can break off
and become trapped in other blood vessels. This commonly occurs where the blood
supply branches to the hindlegs and the tail. This causes loss of blood supply to these
areas, which feel cool to the touch and can become paralysed, along with severe pain.
Success rates for treatment is low, especially as the underlying heart disease means
they are at risk of further blood clots.
Diagnosis of Heart Disease
A diagnosis of heart disease is usually made with ultrasound. Ultrasound allows us to
measure the chambers of the heart and assess how well the heart is contracting.
Enlargement of the heart is usually only a couple of millimetres compared to normal
and is much more easily appreciated on ultrasound than xray. If the heart is enlarged,
xrays of the chest are recommended to assess if any fluid is building up on or
surrounding the lungs as a consequence of the heart enlargement. This cannot be seen
with ultrasound. Follow-up ultrasounds can be performed to monitor how fast the
heart disease is progressing.
If your cat is found to have heart disease it is important to rule out other underlying
conditions, which may be causing the heart disease. This usually involves a routine
blood test to check kidney function and thyroid levels, and a blood pressure check. If
an underlying cause is found, the heart disease often resolves or stabilises once the
underlying disease is under control.
Treatment of Heart Disease
Treatment of heart disease is aimed at reducing any fluid build-up on the chest and
improving how well the heart is able to pump. The most commonly prescribed drugs
are diuretics e.g. frusemide and ACE inhibitors e.g. Fortekor. Occasionally, drugs
need to be given to slow the heart down, to allow it to fill properly between
contractions. If your cat has a large left atrium, drugs may be given to reduce the
chance of a blood clot forming.
Costs Involved
The initial consultation costs £27. Subsequent consultations cost £22.99. A cat with
heart disease requiring medications will normally need to be checked every 3-6
months once stable.
Cardiac ultrasounds usually cost between £55 and £77 depending on the time needed
to take the measurements. Ultrasounds are normally performed whilst your cat is
conscious. Follow-up ultrasounds are performed every 3-12 months depending on the
severity of heart disease present. Chest xrays cost £58.66 for the first film and £26.78
for each subsequent film. Usually two xrays are needed. Most cats require sedation
for xrays to be taken. The cost of sedation varies as the amount of sedative drugs
required alters considerably with the size and temperament of the cat. Blood sampling
charges are £15.58 if done at the time of consult, £19.65 if you decide to have a
separate appointment to have the bloods taken. Lab fees to check kidney and thyroid
values, including blood sampling, cost about £57. Blood pressure checks cost £16.00£18.92 depending if done at the time of a consultation or not.
If your cat requires Fortekor, this costs about £23 for cats less than 5kg and about £45
per month for cats over 5kg. Diuretic treatment costs depend on the dose required but
are usually less than £5 per month.