2. Heart failure
What is heart failure?
Heart failure is the inability of the
heart to maintain sufficient blood circulation to meet the body’s
needs. Heart failure usually describes a failure of the heart muscle
(myocardial failure) or heart valve (mitral valve insufficiency). This
can affect the right or the left ventricle.
Dilated cardiac myopathy
(DCM) occurs most commonly in large
breed dogs and often results in sudden heart failure and death.
My dog ran down the garden and
suddenly dropped dead. The veterinarian said it was due to acute heart
failure. What does this mean?
cardiac arrest can occur for a variety of reasons. Cardiomyopathy is
the leading cause of acute heart failure (heart attack) in dogs.
this the same as a heart attack?
In humans a “heart attack” usually
refers to myocardial infarction (MI). This is death of the cells in an
area of the heart muscle (myocardium). This is usually due to oxygen
deprivation caused by obstruction of the coronary blood vessels. MI is
not a common disease of dogs, but it can occur. In dogs heart failure
is more commonly due to either DCM or to congestive heart failure (CHF)
or mitral valve disease.
is the mitral valve?
The heart has four chambers. The
upper chambers are called atria and the lower chambers called
ventricles. The heart is also divided into right and left
sides. Blood flows back from the tissues and organs of the body via
the vena cava into the right atrium. It is stored briefly in the right
atrium and then pumped into the right ventricle, which pumps the blood
into the lungs where it is oxygenated. It flows from the lungs back
into the left atrium and then passes into the left ventricle which is
surrounded by the largest and strongest of the heart muscles. This
muscle mass is necessary to generate sufficient pressure to pump the
oxygenated blood to the body. The atrium and ventricle are separated
by a valve, which prevents the blood from flowing back into the atrium
when the heart contracts. The valve between the left atrium and
ventricle is the mitral valve. Because this valve must
withstand tremendous pressure throughput life, it may fail and begin
to “leak” as the pet ages. This can be detected with a stethoscope and
is called a mitral murmur.
common is mitral valve disease?
Mitral valve disease is the most
common cause of heart failure in small dogs. In large dogs dilated
cardiomyopathy is the most common cause of heart failure.
serious is a leaking mitral valve?
Approximately 10% of all small breed
dogs will develop mitral valve insufficiency (MVI). This is often
described as a “heart murmur”. MVI is initially asymptomatic, or
having no obvious signs. As time goes on, the leak becomes more severe
and as more blood leaks back into the atrium this results in reduced
pumping efficiency. Eventually congestive heart failure occurs. This
can be months or years from the time when the murmur was first
When I took my little dog for his
annual booster the veterinarian told me he had a mitral murmur but
said he was not going to treat it at this stage. Is this correct?
Veterinary cardiologists differ in
when they recommend medical intervention for asymptomatic heart
murmurs. We will carefully evaluate your pet’s condition and lifestyle
and make the best recommendation to preserve health and vitality.
How will I know if heart failure is
most common clinical sign of congestive heart failure is coughing or
difficulty breathing. This is due to the accumulation of fluid in the
lungs called pulmonary edema. Additionally, many dogs with CHF
will tire more easily, have reduced stamina and not engage in playing
or walking as they once did. If any of these signs develop in a pet
with a heart murmur, notify your veterinarian immediately.
this mean that he will have a heart attack and die?
Not normally, although pets with
heart murmurs are at increased risk of sudden death.
is the leaky valve assessed?
A pet diagnosed with any heart
problem will usually be evaluated by:
or listening to the heart with a stethoscope is the first step in
diagnosing heart disease. Pulse quality and heart rhythm are also
assessed during auscultation.
x-rays are then used to
determine the size and shape of the heart and the presence of fluid in
and urine tests are
performed to give an indication of any other disorders in the body.
Liver and kidney function are often impaired in patients with heart
An electrocardiogram (ECG)
will also be run. This measures the electrical activity of the heart
and allows accurate determination of both heart rate and rhythm. Any
abnormal rhythms (arrhythmias or dysrhythmias) can be detected and
utilizes sound waves to evaluate the heart’s contractions and to
measure the amount of blood pumped by the heart.
does treatment usually involve?
Today we have a wide selection of
drugs that are effective in controlling the effects of CHF. These
include diuretics or drugs to remove fluid from the lungs and
medications that act directly on the heart muscle, improving
contraction and regulating rhythm. In addition, special drugs are used
which dilate the arteries, sometimes also the veins, thus reducing
load on the heart and reducing blood pressure.
this treatment costly and is it long term?
Most dogs will require treatment for
the rest of their lives. Treatment is tailored according to each
patient’s needs and many of the drugs are relatively inexpensive and
a result of all the treatment, how much longer will my dog live?
question is difficult to answer. It depends on the severity of the
condition and the initial response to treatment. Many dogs, once
stabilized, will live for months to years with little reduction in
quality of life.