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). 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 fibrous tissue replacement that interferes with conduction 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 typically due to another disease process like diseases of the nervous system, respiratory system, or gastrointestinal system and are not a primary cardiac issue.
Diagnosing Heart Block
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, based on physical examination findings to assess heart structure and function.
Treatment for Heart Block
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 although they 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, and in some cases medical management of the heart rate might be necessary.