Cardiac Arrhythmia

A dog came in today for a check up to see if she was eligible for surgery.  When we hooked her up to the EKG, we discovered a small heart arrhythmia.

A heart arrhythmia is a disturbance in the beating rhythm of the heart.  This could either be in the amplitude, the frequency or the regularity of the beating.  All of these different kinds of heart arrhythmias involve abnormal electrical activity in the heart muscle.  They can be caused by congenital heart abnormalities, genetic factors, breed disposition, stress, infection or heart disease.

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Every heart beat begins in the sinoatrial node (SA) in the upper right chamber of the heart called the right atrium.  The electrical impulse then travels through the right atrium to an intermediate station called the atrioventrical node (AV) and then to the left and right ventrical chambers at the bottom of the heart.  This journey through the heart creates a pattern that can be seen on an electrocardiogram (EKG).  When there is a disturbance or difference in the electrical impulse's movement through the heart, it is called a heart arrhythmia.

There are two broad umbrella terms that define the different kinds of heart arrhythmias: tachycardia and bradycardia.  Tachycardic arrhythmias are when the heart beats faster than normal.  Although the clinical signs are minimal and sometimes go undetected, tachycardia can be very dangerous for the dog's health.  If the heart rate remains high for too long, the dog could suffer from damage to the heart tissue or heart failure due to pulmonary edema.

Bradycardic arrhythmias are when the heart beats slower than normal.  When the heart beats slow, the amount of oxygen getting to the body is decreases, making it difficult for the organs and tissues to do their jobs.  Patients with bradycardic arrhythmias tend to become dizzy, and confused when not enough oxygen is getting to the brain.  It can also lead to fainting and collapsing.   

A bradycardia arrhythmia is what we saw on the EKG of this dog.  It appeared as if the heart was skipping a beat, however there was just a longer pause before the next beat.  This was valuable information for the doctors and nurses who were planning to take this dog to surgery.  This could possibly cause some problems for the dog while under anesthesia.

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Because there are so many kinds of different arrhythmias, it is hard to say how to prevent them.  Regular veterinary check ups, good exercise, and a healthy diet are a good start though!