Pacemakers are most commonly advised in patients whose heartbeat slows to an unhealthy low rate. ICDs are advised in specific patients who are at risk for potentially fatal ventricular arrhythmias (an abnormal rhythm from the lower heart chambers, which can cause the heart to pump less effectively). There may be other reasons why your physician advises placement of a pacemaker or ICD.
When the heart's natural pacemaker or electrical circuit malfunctions, the signals sent out may become erratic: either too slow, too fast, or too irregular to stimulate adequate contractions of the heart chambers. When the heartbeat becomes erratic, it is referred to as an arrhythmia.
Arrhythmias can cause problems with contractions of the heart chambers by:
- Not allowing the chambers to fill with an adequate amount of blood because the electrical signal is causing the heart to pump too fast.
- Not allowing a sufficient amount of blood to be pumped out to the body because the electrical signal is causing the heart to pump too slowly or too irregularly.