Heart Rate and Irregular Heartbeat in Dogs

Veterinarians use a stethoscope to listen to the heart. You can listen to your dog's heart by placing your ear against his chest. The normal heartbeat is divided into two sounds. The first is a lub,followed by a slight pause and then a dub. Put together, the sound is lub-dub, lub-dub . . . in a steady, evenly spaced rhythm.

The heartbeat should be strong, steady, and regular. A slight alteration in rhythm as the dog breathes in and out is normal. An exceedingly fast pulse can indicate anxiety, fever, anemia, blood loss, dehydration, shock, infection, heat stroke, or heart (and lung) disease. A slow pulse can indicate heart disease, pressure on the brain, or an advanced morbid condition causing collapse of the circulation.

An erratic, irregular or disordered pulse indicates a cardiac arrhythmia. Many arrhythmias are associated with a sudden drop in blood pressure as the arrhythmia begins. The corresponding decrease in blood flow to the muscles and brain is accompanied by sudden weakness or collapse, often giving the impression of a fainting spell.

When the heart sounds can be heard all over the chest, the heart is probably enlarged.

Heart murmurs are common. Murmurs are caused by turbulence in the flow of blood through the heart. Serious murmurs are caused by heart disease or anatomical defects.. Anemia can cause a heart murmur.

Not all murmurs are serious. Some are said to be innocent; that is, there is no disease, just a normal degree of turbulence. To determine whether a murmur is serious or innocent, your veterinarian may request diagnostic studies such as a chest X-ray, an electrocardiogram (ECG or EKG), and an echocardiogram.

Thrills are caused by turbulence of such a degree that you can feel a buzzing or vibration over the chest. This suggests an obstruction to the flow of blood-for example, a constricted valve or a hole in the wall between two chambers of the heart. A thrill indicates a serious heart condition.

Normal Pulse

The pulse, a transmitted heartbeat, is easily detected by feeling the femoral artery, located in the groin. With your dog standing, or preferably lying on his back, feel along the inside of the thigh where the leg joins the body. Press with your fingers until you locate the pulse.

You can also feel a dog's pulse by pressing against the rib cage over his heart. Feel the heartbeat just below and behind the elbow joint. If the heart is enlarged or diseased, you may be able to detect a buzzing or vibration over the chest wall.

The pulse rate is determined by counting the number of beats per minute. Most adult dogs at rest maintain a rate of 60 to 160 beats per minute. In large dogs the rate is somewhat slower and in toy dogs it's somewhat faster. In young puppies the heart rate is about 220 beats per minute.

Circulation

You can determine the adequacy of your dog's circulation and the presence or absence of anemia by examining the gums and tongue. A deep pink color is a sign of good circulation and a normal red blood cell volume. A pale color indicates anemia. A gray or bluish tinge is a sign of insufficient oxygen in the blood (called cyanosis). With severe circulatory collapse, the mucous membranes are cool and gray. However, some dogs, such as Chows Chows, have pigmented lips, gums, and even tongues. These will normally appear bluish, purple, or even black all the time. Know what is normal for your dog.

The adequacy of the circulation can be tested by noting how long it takes for the gums to “pink up” after being firmly pressed with a finger. This is called capillary refill time. The normal response is one second or less. More than two seconds suggests poor circulation. When the finger impression remains pale for three seconds or longer, the dog is in shock.

This article is excerpted from “Dog Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.