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FOREST TRAILS ANIMAL HOSPITAL
Paul L. Welch,DVM / Lisa K. Munson,DVM / Michael A. Rhodes,DVM / Kerry J. Jones,DVM / Michelle Smith,DVM
6528 E. 101st St. / Tulsa, OK 74133 / 918-299-8448
HEART DISEASE
Heart disease is a term used to classify a number of conditions that can affect the heart’s ability
to function as a muscular pump. The breed, age, and size of an animal all play a role in the diagnosis of
specific types of heart problems. One of the most common abnormalities your veterinarian may discover
is a heart murmur. A murmur is caused by a disruption in the normal blood flow through the heart and
vessels creating an abnormal sound that can be detected with a stethoscope. In a normally functioning
heart, the left side of the heart receives oxygenated blood from the lungs and delivers this blood to the
body. The right side of the heart receives blood that has delivered its oxygen to the organs and returns it
to the lungs to be re-oxygenated. When an abnormality in the structure or function of the heart occurs
and the animal begins to show symptoms, this process is called heart failure. While some congenital
heart defects and certain arrhythmias can be corrected with surgery, the majority of animal heart failure is
treated medically.
Heart failure is a complex cascade of events that occurs when the heart is no longer able to
effectively deliver blood to the vital organs. The inability to deliver blood may be due to valvular failure,
heart muscle disease, infectious agents or congenital defects. Once the underlying cause of heart
disease is determined it is then further classified as forward or backward failure according to the
presenting symptoms.
Forward failure is the failure of blood to flow forward to the rest of the body. This involves the
left side of the heart and the circulation of blood. It may be caused by either the failure of the heart
muscle to pump properly or to an increase in the arterial blood pressure making it hard for the left side of
the heart to deliver blood to the body. Animals exhibiting signs of forward failure may be weak, can faint
with stress or minimal exertion, may be cold, drink a lot of water and have pale mucous membranes.
Backward failure can either involve the left or the right side of the heart. With left sided failure
the blood pressure increases in the veins of the lungs, therefore causing leakage of fluid into the lungs.
Subsequently, animals may have difficulty breathing and may cough or wheeze due to build up of fluid in
the lungs. Backward failure involving the right side of the heart arises when the blood pressure increases
in the veins returning to the heart. The symptoms of right sided heart failure are more subtle and include
enlargement of the liver and spleen, excessive fluid in the abdomen (ascites) and diarrhea.
When the heart begins to fail, the body senses that an insufficient amount of oxygen is reaching
the organs. The kidneys respond by producing several hormones that help to increase the blood
pressure, thereby increasing the amount of oxygen the organs receive. Although the increase in blood
pressure is a favorable response early in the disease process, high blood pressure forces the heart to
work harder to get the blood to the organs. Though beneficial at the outset, the compensatory
mechanisms ultimately degenerate into a vicious cycle with deleterious consequences. The symptoms of
heart failure then arise and attempts are then made to control them with cardiac medication.
DIAGNOSTIC TESTS
When an animal is suspected of having heart disease there are several diagnostic tests that can be used to
determine the exact nature of the heart condition.
1.
History—The age, breed, and species of animal often dictate which cardiac conditions are most likely
to occur.
2.
Auscultation—The use of a stethoscope to listen to the heart enables the doctor to detect a heart
murmur (a flow of blood backwards through the heart valves) and/or an arrhythmia (an abnormality in
heart rhythm).
3.
Radiology—Will show heart enlargement, fluid buildup in the lungs. and enlargement of the blood
vessels of the lungs and heart.
4.
Ultrasonography—Can detect the thickness of the heart muscle, which chambers or valves are
involved in heart disease and if there are any congenital defects in the heart.
5.
E.K.G.—An electrocardiogram indicates any abnormalities in heart rhythm as well as atrial and
ventricular enlargement.
6.
C.T. w/ contrast— Computed tomography with contrast medium can help to show congenital defects
with the vessels of the heart as well as the heart itself.
TREATMENT
Once it is determined that medical intervention is necessary, the veterinarian will stage the
animal’s heart disease based upon clinical signs and institute the appropriate therapy according to the
animal’s specific cardiac disease. Therapy may range from a low sodium diet and exercise restriction to a
myriad of cardiac medications that target individual symptoms. The medications include diuretics
(decrease fluid in the lungs), bronchodilators (improve oxygen exchange), vasodilators (decrease high
blood pressure), positive inotropes (improve contraction of heart muscle) and anti-arrhythmics (to stabilize
irregular heart beats). Medication is used in an attempt to resolve clinical signs and to slow the
progression of heart disease. The overall goal of therapy is to make the animal comfortable and able to
function as close to normal as possible. Ultimately however, a time comes when medications are no
longer able to correct the deficits of a failing heart and a decision must be made about the quality of the
pet’s life. If we can help with these decisions in any way, please let us know.