A delay that arises in the conduction between the atrium and the ventricle is termed a heart block. In most cases, this term is a misnomer, because the condition most frequently causes a delay rather than an actual block. However, one advanced form of the condition, complete heart block, does, in fact, refer to a true disconnect between the atrium and the ventricle.

Heart block typically occurs as part of the aging process. The conductive fibers become thickened and scarred with fibrosis or collagen as they age. Ultimately, they calcify, delaying the relay of electrical signals and affecting the performance of the heart. Specific diseases, such as Lyme disease, can also cause heart block. However, the Lyme condition is usually reversible with the treatment of the disease. Certain drug therapies are associated with a decreased heart rate or may otherwise impact the functioning of the SA or AV node. In such instances, a choice will be made whether to discontinue the medication or implant a pacemaker. The pacemaker supports the heart electrical cycle, thereby allowing the patient to safely continue the drug therapy.

A pacemaker helps to ensure a regular heart rhythm.

Patients who have heart block usually receive an implantable pacemaker device. The pacemaker can deliver electrical signals to the atrium and ventricle with or without the cooperation of the heart's own system. Today's sophisticated pacemakers can follow the lead of the atrial chamber if that structure continues to operate normally, but will assume control if the heart fails to fall within certain parameters—typically between 50 and 150 beats per minute. If the ventricular chamber does not follow the lead of the atrium, it receives its own, specially timed electrical stimulation through a second wire extended from the pacemaker to the ventricular chamber.

Pacemakers enable us to guarantee both that a patient's heart rate will not fall below a certain normal value, and that it will increase appropriately in response to activity. Patients who have electrical disease in an otherwise healthy heart can continue to function normally once they receive a pacemaker. The elderly are by far the most common recipients of pacemakers, but these devices have also been implanted in children and young adults. Pacemaker functions can be monitored by phone. The settings can be changed by the physician in an office using a remote control device to communicate with a computer in the pacemaker itself. Replacement is required every five to 10 years on average and is indicated by regular checkups.