Range and Variability of the Canine Heart Rate

" Canine heart rate is stated as the heartbeats noted per unit of time, such as heartbeats per minute – or bpm. At the clinic, veterinarians prefer detecting heart sounds, heart rate and/or murmurs to detect any abnormality in heart function. A physical examination for dogs with a history of possible heart problems is mostly based upon the estimation of the dog heart rate. Detection of heart sounds, murmurs, pulses and arrhythmias are included in any physical examination, in order to estimate the strength of collective canine heart function. However, a confirmatory diagnosis is made on basis of the results from specific procedures such as an electrocardiogram, echocardiogram and chest X-Rays etc. Specific treatment of a dog heart condition can resolve any abnormal canine heart rate. The use of supportive remedies and care can also help to improve canine heart function."

Canine Heart Rate Facts

A health dog has steady, strong and regular heart rate, with an average 70 – 120 heartbeats per minute, which if detected, generally are heard in two parts, representing relaxation and contraction of the dog heart, but technically, these are four different sounds, classified as S1, S2, S3 & S4. These represent the closure and opening and/or contraction or relaxation of different cardiac valves.

Puppies have a relatively faster heart rate, i.e. 180 bpm are considered normal for puppies of up to one year. Larger dogs have slower heart rate then small sized dogs. Similarly, dogs with a normal physique and health have slower heart rates as compared to diseased dogs.

It should be remembered that heart rate is not only related to heart disease in dogs. In general, a faster canine heart rate may represent anxiety, anemia, fever, dehydration, shock, infection and heart or lung disease in general. A chronically slower canine heart rate on other hand, usually represents some kind of serious canine heart disease. Due to this unique characterization of heart rate in dogs, auscultation (listening to sounds) of the thorax and chest with help of a stethoscope is a vital part of a canine physical examination, something that is done for almost all canine health problems.

How to Detect:

Since, heart rate is a vital characteristic when estimating canine health, a dog owner should be aware of techniques used to detect and identify differences between a normal and an abnormal  heart rate. It should be considered as an essential part of a routine checkup or examination done by owners at home. A dog may be lied on its back and the site where the elbow of a dog touches its chest while laying, is the most appropriate site for detection of a dog heart rate/beats. An owner can either sense heart beats with the tips of the fingers, or with help of a stethoscope.

A normal and healthy dog will represent strong, steady and regular heart beats, while a diseased dog will express extremely fast or slower heart beats. Similarly, pulse rate or transmitted heartbeat can be detected in the femoral artery (which lies in the groin area). Normal ranges of heartbeats should be carefully detected and if any disturbance, murmurs or missing heartbeats are detected, a dog should immediately be referred to a veterinarian for detailed examination.

Diagnostic Importance:

As discussed above, auscultated (listened to) canine heart rate and/or heart sounds are divided into four parts; S1, S2, S3 & S4. The first heart sound, S1, represents the closure of artrioventricular valves (AV). The second heart sound, S2 represents the closure of semilunar valves. S3 or the third heart sound is heard on the rapid filling of ventricular valves in early diastole (when heart ventricles fill with blood), while final or S4 heart sound is detected on artrial systole (heart contraction).

In dogs, only S1 and S2 heart sounds are audible on auscultation (when listening) and veterinarians make their whole estimation on the basis of these two audible sounds. Clinical diagnosis is based upon normal audibility of these sounds, fast galloping S3 and S4 sounds represents serious cardiac myopathy (dog heart disease). Similarly, in estimation/diagnosis of a condition through the canine heart rate, pattern in splitting of S1 and S2 heart sounds too are also important.

In cases where there are severely complicated dog heart diseases; heart sounds, murmurs and arrhythmias are additional physical auscultating procedures (listening to the heart) done for confirmation of any disease.

Confirmatory diagnosis is done with the help of advanced procedures such as electrocardiogram, echocardiograms, Ultrasounds and chest X-Rays, which reveals the exact status and condition causing patient health risk.

Treatment of an Abnormal Dog Heart Rate:

Dog heart rate may appear abnormal or slightly altered in almost every health condition. This is only a representation of a health disorder. Specific tests and clinical procedures are the only way to confirm any underlying condition. Therefore, the specific treatment of any condition whether it is related to the cardiac system or not, is essential to resolve any abnormality in canine heart rate. Heart diseases should be treated accordingly, with medical and surgical approaches. Similarly, for problems such as dehydration, anemia and anorexia, specific therapies should be applied to overcome any underlying condition.

Supportive therapies and care is always required for dogs diagnosed with serious heart or any systemic health problem. Care should be taken in day to day routine activities for any dog with abnormal heart rates, including nutrition, the monitoring of heart rate, blood pressure and overall physiology.

Some natural remedies, like heart tonics and immunity and liver boosters, can help to improve circulatory and heart rate conditions during disease.

References:

Merck Veterinary Manual (Merck & Co.)