Heart block is when the electrical signals sent to your pet's heart from their brain aren't properly conducted from the top to the bottom of your companion's heart. This cardiac issue can be quite serious if not identified and addressed. Here, our veterinary cardiologists explain what it is, its diagnosis and the treatment for heart block in pets to our Boulder and clients.
What is Heart Block?
Heart block, in general, is the delayed or absent conduction through the communication point between the upper and lower chambers of the heart (called the atrio-ventricular, or AV node). Essentially, the top of your pet's heart isn't properly conducting electrical signals from the brain properly to the bottom of their heart, affecting their heartbeat.
There are several types of heart block, including first degree, second degree, and third degree (complete) heart block. However, the most serious forms are known as high-grade second degree AV block, and third degree AV block.
The most common causes of these types of heart block are the buildup of fibrous tissue on your pet's heart that interferes with the conduction of brain signals through the AV node.
Other causes include electrolyte abnormalities, high resting nervous system tone (called high vagal tone), some medications and inflammatory or infectious processes. Alterations in nervous influence are generally due to a secondary health condition like diseases of the nervous system, respiratory system, or gastrointestinal system and are not a primary cardiac issue.
How is Heart Block Diagnosed?
Most cases of heart block are diagnosed by performing an electrocardiogram (ECG). An ECG records conduction through the heart and therefore enables detection of the various types of heart block. In some cases, a specific test, called an “atropine response test” will be performed as well to confirm that the heart block is due to a cardiac cause. In cases of intermittent heart block, a Holter monitor (24 hour ECG monitor) may be recommended.
An echocardiogram may also be recommended depending on physical examination findings to assess heart structure and function.
How is Heart Block Treated?
If the heart block is due to a primary cardiac issue, then the treatment depends on the severity of the condition. If the heart block is causing symptoms (decreased energy level or fainting episodes), then the treatment of choice is to place a permanent pacemaker to control the heart rhythm and alleviate these symptoms.
If a permanent pacemaker is not an option, then medical management options can be considered. However, these are often less successful than pacemaker therapy.
If the heart block is due to a non-cardiac issue, treatment of the underlying disease process is recommended. In some cases medical management of the heart rate might be necessary.