It is more common than we think that from time to time a dog with an irregular heartbeat or cardiac arrhythmia appears at the clinic. One of them is sinus bradycardia, which consists of a reduction in heart rate due to slower impulses in the sinus node, which affect the contraction of the heart. The causes of bradycardia in dogs are diverse and it is not only produced as a consequence of some cardiac problem. The treatment will depend on the original cause and its diagnosis is key to guide the best treatment.
What is bradycardia in dogs?
Bradycardia or sinus bradycardia is a type of cardiac arrhythmia in which the affected dog has an abnormally low heart rate as a result that the impulses in the sinus node of the heart are activated more slowly. These impulses are what cause the contraction or heartbeat, therefore, a reduction in the activation of the impulses causes the beats per minute to decrease.
Sinus bradycardia can be physiological in the most athletic dogs or dogs that do intense exercise regularly, being something totally appropriate, beneficial and harmless in these cases. It is dangerous when the reduction in heart rate is the result of a serious medical condition and can lead to syncope or loss of consciousness.
There are certain breeds with a greater predisposition to bradycardia:
- Miniature Schnauzer.
- Cocker spaniel.
- West highland white terrier.
- Pug.
- Dachshund.
Bradycardia symptoms in dogs
Bradycardia is said to be present if the heart rate in dogs puppy is below 160 beats per minute, while in dogs small adults should be lower at 100 beats per minute and in large adults should be below of the 60 beats per minute.
The symptoms will depend on whether the bradycardia is physiological or not. In the first case, it is likely that your dog will not show any symptoms if he is sporty and athletic, but they may appear if the cause is an organic disease.
Within the clinical signs that a dog with sinus bradycardia may show, we can find the following:
- Cough.
- Exercise intolerance.
- Lethargy.
- Bradypnea or decreased respiratory rate.
- Exhaustion.
- Muscular incoordination.
- Seizures.
- Depression.
- Pale mucous membranes.
- Fainting.
- Sudden death.
In addition, as an arrhythmia, in some cases it can lead to heart failure, changes in blood pressure and changes in blood flow to vital organs.
Causes of bradycardia in dogs
Abnormally reduced heart rate at rest or bradycardia can have different causes in dogs, the majority being pathological. We have already mentioned that there is physiological bradycardia in sporting dogs so that the heart does not have to work as hard during exercise to pump already oxygenated blood throughout the body, but it can also be the result of a cardiac or extracardiac problem
Within the heart problems that can cause bradycardia in dogs we find myocarditis or inflammation of the heart muscle or myocardium, pericarditis or inflammation of the lining of the heart, or cardiomyopathy , which may be dilated or hypertrophic. With regard to extracardiac causes, we can highlight hypothyroidism or reduction of thyroid hormones that result in a decrease in the dog's metabolism, insufficiency orliver or kidney disease, or disorders that produce a drop in blood magnesium or potassium (hypokalaemia).
Other causes of sinus bradycardia in dogs include hypothermia or reduced body temperature, tracheal intubation, or sedation.
Diagnosis of bradycardia in dogs
Diagnosis of sinus bradycardia is simple, as your veterinarian can easily detect it with a stethoscope by measuring heart beats per minute If an electrocardiogram (ECG) is performed, extra information can be obtained to define if there really is bradycardia and if it coexists or not with another type of cardiac arrhythmia.
The next step is to determine the cause of the dog's bradycardia. To do this, your veterinarian should carry out diagnostic techniques such as a blood test and biochemistry to assess the status of the thyroid, kidney and liver and determine any electrolyte abnormality or hematological. Chest radiography is also often indicated to assess the status of the heart, although ultrasound of the heart or echocardiography is preferred
Treatment of bradycardia in dogs
Sinus bradycardia in dogs will be treated depending on the cause In sporting dogs whose bradycardia is physiological, it is not treated because We have commented that it is normal and harmless. However, it should be treated in dogs with an organic cause that is possibly producing undesirable clinical signs. As an example, let's see some specific cases:
- In the case of hypothyroidism, the dog should be treated with the missing thyroid hormone replacement.
- Kidney and liver disease should be controlled with specific therapy.
- Electrolyte imbalances need to be addressed.
- Heart problems should be treated specifically, depending on the problem in question, with cardiac stimulant and antiarrhythmic drugs.
- Cases of bradycardia reactive to intubation, sedation or anesthesia resolve spontaneously after the procedure.
- In hypothermia, the dog's body temperature should be progressively increased in order to increase the heart rate, among other symptoms, which causes this problem.
- In cases where bradycardia suddenly appears critically, it will be necessary to hospitalize the dog to control it and administer fluid therapy.
As you can see, the treatment of bradycardia in dogs varies enormously from one cause to another, so it is essential go to the veterinary center at the appearance of the first symptom.
