Implantable Cardioverter Defibrillators (ICD)
ICDs are automatic devices that can detect and treat dangerous rapid heart rhythms. While artiarrhythmic drugs may prevent the occurrence of an arrhythmia, ICDs are the only treatment that can terminate (stop) an existing arrhythmia once it has started.
ICDs, like drugs, do not cure the underlying disease that causes arrhythmias. Instead, these devices terminate the arrhythmia and store a record of the event for the doctor to evaluate later.
How Therapy Is Delivered
The ICD monitors the heart rhythm continuously. If it senses a life-threatening rhythm, it delivers an electrical treatment, or therapy, based on the settings programmed by your doctor.
- Antitachycardia Pacing. If the ICD detects
a rapid, regular rhythm (such as VT), it can deliver a series of small,
rapid pacing pulses. These pulses override the rapid rhythm and help return
the heart to its normal rhythm.
- Cardioversion. If pacing does not stop the
rapid rhythm, or if the arrhythmia is very fast, the ICD may deliver one
or more electric shocks to the heart. These cardioversion shocks can be
programmed from low to high energy, as needed.
- Defibrillation. If the ICD senses a very
rapid, irregular rhythm (such as VF), it will deliver a high energy shock
to the heart. The defibrillation shock interrupts the arrhythmia so a more
normal rhythm can be restored.
The ICD's main function is to interrupt rapid heart rhythms. Sometimes, however the heart may beat too slowly---this is called bradycardia. If the ICD senses a very slow heartbeat, it can deliver pulses to et the slow heartbeat back to the right speed. This is called bardycardia pacing.
What Therapy May Feel Like
