What Is Heart Block?

Heart block causes problems with the way the heart conveys electrical signals, and depending on the type, it can disrupt or slow heart rhythm and result in serious risks. Though the name sounds like it involves blocked arteries or blood flow to the heart, this condition really references the way the atria send electrical signals to the ventricles to cause them to maintain a steady rhythm. When this conduction path is slowed or fully interrupted, the heart may beat slower or beat so inefficiently it cannot adequately circulate blood. The severity of this condition and its need for treatment depends on type, and generally three types (Types I, II, and III) are discussed.

There are different circumstances under which any form of heart block may occur. It is sometimes a congenital condition, manifesting in some children before they are even born. It may result after cardiac surgery to treat congenital heart defects or adult heart disease. Some athletes develop it at any time in life. Older adults with or without various kinds of heart disease may also have heart block, and this last group tends to be the largest.

Types of heart block indicate its symptoms and need for treatment. Type I refers to a situation where tiny delays in the signaling from atria to the ventricles, and it doesn’t have any symptoms or require medical intervention. An electrocardiogram (ECG) shows delays, but many don’t know they have Type I because ECGs aren’t routine tests. This form of signal dysfunction is benign, may never progress to another type, and doesn’t pose risk for problems. The heart can function very well with a very small signal delay.

Type II can be more serious and there are at least two subtypes of this form of heart block. In one subtype, some electrical signals don’t make it to the ventricles and this can result in “skipped” beats, which additionally causes symptoms like dizziness.
A more serious form is called Mobitz Type II, and many signals miss the ventricles creating a heart rhythm that is far too slow. This second type requires treatment — implantation of a pacemaker to regulate rhythm is often needed.

Type III or complete heart block also needs pacemaker implantation because no signals from the atria reach the ventricles. Heart rate is significantly slowed as the ventricles rely on their own conduction system, which is inadequate. Without treatment with a pacemaker, heart attack or heart failure may occur and fatality is possible.

If this condition in any of its forms arises, patients will be referred to a cardiologist or electrophysiologist to diagnose the type and to look for any other illnesses that may be contributing factors. As stated, some forms of Type I and Type II may not need treatment, but Mobitz Type II and complete heart block benefit from rhythm regulation to keep the heart functioning well. Pacemaker implantation is a common surgery, and many patients undergoing it leave the hospital within a day or two of surgery.