The Classic Comprehensive Handbook of Cat Care
HEART AND BLOOD
(CIRCULATORY SYSTEM)
Your cat’s circulatory system is similar to your own. It consists of a four-chambered heart that serves as a blood pump, arteries that carry blood away from the heart to the capillaries where molecular exchange occurs, and veins that return blood to the heart. There are no direct methods you can use to examine this system. A stethoscope (available at medical supply houses) will aid you in listening to your cat’s heart, but one is not necessary to deal with everyday health problems you may encounter.
The normal heart beats about 130 times per minute in the resting cat.
Slightly agitated or nervous but normal cats often have heart rates between 165 to 200 beats per minute. You can feel the heartbeat by placing your fingers or the palm of your hand against your cat’s chest just behind the point of the elbow. Placing your hand completely around the lower part of the chest with your fingers on one side and your thumb on the other is another simple and easy way to feel your cat’s heart beat. If you cannot feel the heartbeat, you can usually hear it by placing your ear (or a stethoscope) against the chest. Each heartbeat consists of a strong, low-pitched thud, followed by a less intense, higher pitched thud, followed by a pause—lub- dup… lub-dup … lub-dup. In most healthy cats this rhythm is very regular, unlike dogs who usually have a variable heartbeat rhythm.
SCHEMATIC DRAWING OF HEART
FEELING THE HEARTBEAT
To take your cat’s pulse, place your fingers at the middle of the inside surface of the rear leg near the point where the leg meets the body. This is the area where the femoral artery passes near the skin, allowing you to feel the pulse. The heart rate and pulse rate should be the same; true discrepancies between them indicate serious circulatory problems. It is easiest to count the heart rate or pulse for fifteen seconds, then multiply by four to calculate the rate per minute.
FEELING THE PULSE
A measure of capillary circulation is capillary refilling time. To measure this, press one finger firmly against your cat’s gums. When you lift it away you will see a pale area that should refill with blood almost instantaneously.
This measure of circulatory effectiveness can be helpful in evaluating possible shock.
Blood is the fluid transported by the circulatory system. Blood consists of plasma, platelets, red blood cells, and white blood cells. The composition of the liquid portion of the blood, plasma, is very complex. It carries nutrients throughout the body, removes wastes, including carbon dioxide, and provides a means of transport for the hormones produced by the endocrine glands, as well as transporting the particulate blood constituents, the platelets and the red and white blood cells. Platelets are produced primarily in the bone marrow of the adult cat. These small bodies help prevent hemorrhage when a blood vessel is injured by aggregating together to form a physical barrier to blood flow and by stimulating clot formation. Red blood cells carry oxygen to the tissues and to a much lesser degree transport carbon dioxide away. They give blood its red color. They also determine the cat’s blood group (type). Cats have three blood types A, B, and AB. Cats in group B have the greatest risk of reaction to unmatched blood transfusions since blood type A is most common.
Ideally the blood type of both the donor and recipient should be known prior to blood transfusion. A veterinarian can have your cat’s blood typed in anticipation of an emergency requiring blood transfusion or donation. There are several kinds of white blood cells, and each type has a particular function. As a group the white blood cells are most important in preventing and fighting infection. The red blood cells and white blood cells often change in number and in type when a cat becomes sick. The measurement of these cells by means of a complete blood count (CBC) performed by your veterinarian is frequently necessary for correct diagnosis and treatment of cat health problems.
The spleen is an abdominal organ that, although not necessary for life, has many functions related to the blood. You may have felt this organ during your examination of the digestive system. In the adult cat the spleen produces some white cells, and, in times of need, it can produce red cells as well. It is a blood reservoir that can supply large numbers of red cells rapidly when the body needs oxygen. The spleen also removes old and abnormal red blood cells from circulation and stores some red cell components, such as iron.