The heart is a pump made up of muscle tissue and, like all pumps, it requires a source of energy to function. The heart’s pumping energy comes from an indwelling electrical conduction system. An electrical stimulus is generated by the sinus node, which is a small mass of specialized tissue located in the right atrium or right upper chamber of the heart.
Problems with your heart rhythm can cause difficulty because your heart is unable to pump an adequate amount of blood to your body. If your heart rate is too slow, your blood is pumped too slowly. If your heart rate is too fast or too irregular, your heart chambers are unable to fill up with enough blood to pump out with each beat. When your body does not receive enough blood, symptoms such as fatigue, dizziness, fainting, and/or chest pain may occur.
An irregular heartbeat is an arrhythmia (see webmd.com/heart-disease/guide/heart-disease-abnormal-heart-rhythm). Heart rates can also be irregular. A normal heart rate is 50 to 100 beats per minute. Arrhythmias and abnormal heart rates don’t necessarily occur together. Arrhythmias can occur with a normal heart rate, or with heart rates that are slow — less than 50 beats per minute. Arrhythmias can also occur with rapid heart rates — faster than 100 beats per minute. In the United States, more than 850,000 people are hospitalized for an arrhythmia each year.
Procedures to treat individuals with arrhythmias are often performed either with a pacemaker insertion or an implanted cardioverter defibrillator (ICD). Reasons for these procedures may include:
• Atrial fibrillation that occurs when the atria beat irregularly and too fast
• Ventricular fibrillation that occurs when the ventricles beat irregularly and too fast
• Bradycardia that occurs when the heart beats too slow
• Tachycardia that occurs when the heart beats too fast
• Heart block that occurs when the electrical signal is delayed after leaving the SA node.
There are several types of heart blocks, and each one has a distinctive ECG tracing.
A pacemaker is an implanted device that sends small electrical impulses to the heart muscle to maintain a suitable heart rate. Pacemakers primarily prevent the heart from beating too slowly through a pulse generator that sends impulses to the heart muscle. Newer pacemakers have many sophisticated features designed to help manage arrhythmias and optimize heart rate-related function as much as possible.
An ICD may be inserted in order to provide fast pacing (ATP) or defibrillation when the heart beats too fast. It is used primarily to treat ventricular tachycardia and ventricular fibrillation. The ICD constantly monitors the heart rhythm. When it detects a very fast, abnormal heart rhythm, it delivers energy to the heart muscle to cause the heart to beat in a normal rhythm again. There are several ways the ICD can be used to restore normal heart rhythm.
Anti-tachycardia pacing when the heart beats too fast sends a series of small electrical impulses to the heart muscle to restore a normal heart rate and rhythm.
Defibrillation is used when the heart is beating dangerously fast or irregularly, a higher energy shock may be delivered to the heart muscle to restore a normal rhythm.
Anti-bradycardia pacing uses ICDs to provide back-up pacing to maintain heart rhythm if it slows too much.
Pacemaker and defibrillator insertions are usually performed on an outpatient basis by a cardiologist with the assistance of the ambulatory surgery team. The nature of your occupation, your overall health status, and your progress will determine how soon you may return to work and perform other tasks, such as driving or exercise. Many individuals are able to return to their daily routine within a few days.
Dr. John Pearson is a board-certified cardiologist on the medical staff at Eastern Long Island Hospital.