Implantable Cardioverter-Defibrillator (ICD): What First Aiders Should Know
An implantable cardioverter-defibrillator (ICD) is a battery-powered medical device designed to correct dangerous heart rhythms and help prevent sudden cardiac death. The device is implanted in the chest and connected to the heart through one or more insulated wires (leads) placed through a vein.
An ICD may be recommended for individuals who have experienced a life-threatening abnormal heart rhythm or who are at high risk due to underlying heart conditions such as heart failure, coronary artery disease, or structural or electrical abnormalities of the heart.
How an Implantable Cardioverter-Defibrillator Works
An ICD continuously monitors the heart’s rhythm.
If a dangerously fast heart rhythm is detected, the device responds by:
- Delivering electrical pacing to restore a normal rhythm, or
- Delivering a shock to reset the heart rhythm if pacing is ineffective
If the heart rate becomes too slow, the ICD can also act like a pacemaker by sending electrical signals to maintain an appropriate heart rate.
The device operates automatically and only activates when needed.
Placement of an Implantable Cardioverter-Defibrillator
An ICD is implanted during a minor surgical procedure, usually under local anesthesia with light sedation.
During the procedure:
- A small incision is made in the upper chest
- One or more leads are guided through a vein into the heart
- The device is placed under the skin and programmed
- The incision is closed once testing confirms proper function
Most individuals remain in hospital overnight for observation.
What Does an ICD Shock Feel Like?
If the ICD delivers a shock, it may feel like a sudden jolt or strong thump in the chest. While uncomfortable, this indicates the device is working to correct a dangerous rhythm.
Electrical pacing used to correct slower or mildly fast rhythms is usually not felt.
Important First Aid Considerations
For first aiders and bystanders:
- A person with an ICD can still experience cardiac arrest
- CPR and AED use are still required if the person becomes unresponsive and is not breathing normally
- An ICD shock does not replace the need for emergency response
Understanding ICDs helps first aiders respond confidently and without hesitation during cardiac emergencies.
First Aid Training in Canada
First aid and CPR training teaches:
- How to recognize cardiac emergencies
- When to begin CPR
- How and when to use an AED safely, even if an ICD is present
This knowledge is essential for workplaces, schools, parents, caregivers, and community responders across Canada.
Educational Disclaimer
This information is provided for educational purposes only and does not replace medical advice. For hands-on skills and emergency response training, certified first aid instruction is recommended.