Bradycardia is a change in the rhythm of your heartbeat. When the heart beats too fast, it’s called tachycardia. When it beats too slow, it’s called bradycardia. An arrhythmia can also mean that your heart beats irregularly (skips a beat or has an extra beat).
Bradycardia is another form of arrhythmia, but instead of a very fast heart rate, people suffering from bradycardia present an abnormally slow or unsteady heart rhythm (usually less than 60 beats per minute). This slower heart rate results in less blood and oxygen being pumped and results in dizziness, fainting, being extremely tired, and shortness of breath.
There are two primary causes of Bradycardia, the most common being a problem with the sinoatrial (sinus) node, which is the body’s natural pacemaker. The sinoatrial node regulates the heartbeat by sending signals to the atrioventricular, which passes the signals on to the lower half of the heart. These signals cause the heart to contract and pump blood and oxygen to the rest of the body. Sometimes, the sinoatrial node does not send signals frequently enough, causing the heart to contract less often than it should.
The other primary cause of Bradycardia is the malfunction in the heart’s electrical pathways. This means that even when the sinotrial node is sending properly timed signals to the heart to contract that those signals are not reaching the lower part of the heart. The electrical signals may be delayed in the atrioventricular node or may fail to reach the ventricles all together.
This condition is called heart block. Although the lower heart has a natural standby system that can produce its own signals, these signals are often too slow. As a result, heart block often means that the ventricles pump too slowly.
In either case, these problems result in heartbeats that don’t sufficiently meet the needs of your body.
Heart block may also cause a loss of AV synchrony. If the timing of contractions between the upper and lower heart is poor, the ventricles may not fill with enough blood before pumping. Your doctor may call this condition asynchrony.
Diagnostic tests such as an electrocardiogram assist the doctor in discovering the specific cause of the bradycardia. When an irregular heart rhythm cannot be seen at the time of the test, an implantable loop recorder, a temporary device that records a patient’s heart beats for later retrieval may be used to track the rhythm.
The physician might also prescribe a stress test or electrophysiologic study. A stress test is an electrocardiogram performed while the patient exercises, usually jogging on a treadmill or riding a stationary bike. An electrophysiologic study is a more invasive test where the doctor inserts a small tube through a blood vessel, running it to the heart, where he/she can more closely determine the cause of the bradycardia.
Bradycardia is most commonly treated with a pacemaker. A pacemaker alters the heart rate to help meet your body’s needs. The pacemaker provides signals much like the heart’s normal signals. Depending on your particular situation, a pacemaker will:
- replace sinoatrial node signals that are delayed or get lost on the pathway between the upper and lower heart; or,
- help maintain a normal timing sequence between the upper and lower heart; or
- make sure the critical lower chambers of the heart always contract at an adequate rate.