Mark Errol Amayag, Paul Doligas & Mary Rose Nieminen
Introduction
The American Heart Association states that the incidence of cardiac arrest in the out-of-hospital setting is more than 350,000 while in the in-hospital environment, it is around 209,000. It was also mentioned that the survival rate was not that high, 12% and 24.8% respectively. In our recent studies, we had been discussing about resuscitation, ECG and the different types of arrythmia. Since we find these topics very interesting, we decided to focus on the new ways how to decrease mortality rates caused by cardiac arrests. An implantable cardioverter-defibrillator (ICD) is a specialized implantable electronic device designed to directly treat a cardiac tachyarrhythmia. It is equipped with a demand pacing system and serve the dual functions of emergency defibrillation and backup pacing. It means that if a patient has a ventricular ICD and the device senses a ventricular rate that exceeds the programmed threshold, the device may be programmed to deliver antitachycardia pacing therapy (ATP) or defibrillation. After reading articles concerning ICDs, several questions came to our minds, how costly the device is, how is it implanted to the patient, does the procedure have complications, how common is its usage nowadays, and how long is the devices' lifespan.
How does it work?
An implantable cardioverter defibrillator (ICD) has wires with electrodes on the ends that connect to one or more of your heart's chambers. These wires carry the electrical signals from your heart to a small computer in the ICD. The computer monitors heart rhythm. If the ICD detects an irregular rhythm, it sends low-energy electrical pulses to prompt the heart to beat at a normal rate. If the low-energy pulses restore heart's normal rhythm, this might avoid delivery of high-energy pulses or shocks of the defibrillator (which can be painful). Single-chamber ICDs have a wire that goes to either the right atrium or right ventricle. The wire senses electrical activity and corrects faulty electrical signaling within that chamber. Dual-chamber ICDs have wires that go to both an atrium and a ventricle. These ICDs provide low-energy pulses to either or both chambers. Some dual-chamber ICDs have three wires. They go to an atrium and both ventricles. The wires on an ICD connect to a small metal box implanted into chest or abdomen. The box contains a battery, pulse generator, and small computer. When the computer detects irregular heartbeats, it triggers the ICD's pulse generator to send electrical pulses. Wires carry these pulses to the heart. The ICD also can record the heart's electrical activity and heart rhythms. The recordings can help doctor fine-tune the programming of ICD so it works better to correct irregular heartbeats. The type of ICD given to patient is based on heart's pumping abilities, structural defects, and the type of irregular heartbeats the patient had. ICD will be programmed to respond to the type of arrhythmia the patient most likely to have.
Usage and Safety
Main Parts:
- The ICD – The ICD is powered by a battery and generates an electrical shock. It is also called the battery, device, or pulse generator.
- The leads – Flexible, insulated wires, or leads, monitor the electrical impulses and report the heart's electrical activity back to the ICD.
Procedure:
In most cases, an ICD is inserted after the person is given a sedative and a local anesthetic (numbing medication) is injected into the skin. Some patients will be given general anesthesia, which is used to induce sleep while the procedure is performed. The surgery involves making an incision below one of the collarbones. The leads will be placed into the heart through the vein that runs next to the collarbone. Up to three leads will be placed inside the heart. One lead will be placed in the ventricle (bottom chamber) and one may be placed in the atrium (top chamber), on the right side of heart. A third lead is implanted when cardiac resynchronization therapy is planned. During the operation, routine electrical measurements of the heart will be made to be sure that the leads are positioned correctly. After the leads are in place, they are connected to the ICD. The device will be placed under the skin in the upper chest. The clinician may trigger the heart to beat rapidly, and then use the ICD to deliver a shock to the heart and stop the rapid beating; this is usually done one to five times to make sure the ICD functions properly. The procedure takes about 30 to 90 minutes to complete. A chest x-ray is performed after the procedure to be sure the leads are in the proper position and that the lung has not been injured or collapsed during the procedure. Patients usually stay in the hospital overnight. The first follow-up appointment to check the incision is usually one to two weeks after the surgery.
Safety:
- Follow-up apointment - six weeks after implant then followed by every 3 months or 6 months follow-up.
- Battery Replacement – device will normally last between 5-10 years. Having the battery replaced requires a surgical operation similar to initial implant (same scar site). • Driving- driving is not allowed6 months following ICD procedure.
- Most household appliances are safe to use with ICD. • Mobile phones should be used on the opposite side to implant.
- All power tools should also be kept at arms’ length.
- ICD users cannot undergo a Magnetic Resonance Imaging (MRI) scan unless they have been fitted with an MRI compatible device.
- This device (ICD) can be sensitive to strong electromagnetic interference (EMI). If ICD users' employment requires to be close to large industrial generators or other sources of EMI, they may need to take extra precautions. They should discuss any issues or concerns with the employer before returning to work.
- As a rule the ICD users begin to feel unwell using any equipment, they must stop and remove themselves from the area.
- In the event of air travel, ICD patient must inform security screeners that he has an ICD before going through the metal detector.
Prospects
Remarkable technologic advances have made ICDs easier and safer to implant and better accepted by patients and physicians. The development of transvenous lead systems, more effective biphasic defibrillation waveforms, and "active can" technology allows implantation in nearly all patients without the need for thoracotomy. The current ICDs have markedly progressed in their therapeutic and diagnostic functions. Early devices were simple “shock boxes,” offering only high-energy shocks when the patient's heart rate exceeded a cut-off point. Diagnostic information was limited to the number of shocks delivered. Current devices offer tiered therapy with programmable antitachycardia pacing schemes, as well as low-energy and high-energy shocks in multiple tachycardia zones. Dual-chamber, rate-responsive bradycardia pacing is now available in all ICDs, and sophisticated discrimination algorithms minimize shocks for atrial fibrillation, sinus tachycardia, and other non–lifethreatening supraventricular tachyarrhythmias. Diagnostic functions, including stored electrograms, allow for verification of shock appropriateness. Device battery longevity has also increased; early devices lasted 5 years or less, while current devices are expected to last 8 years or longer.
References
American Heart Association.Statistical. Available at <http://cpr.heart.org/AHAECC/CPRAndECC/General/UCM_477263_Cardiac-Arrest-Statistics.jsp> Accessed 4 March 2017.
How Does an Implantable Cardioverter Defibrillator Work? Updated 9.11.2011. Available at <https://www.nhlbi.nih.gov/health/health-topics/topics/icd/howdoes> Accessed 4 March 2017.
Implantable Cardioverter Defibrillator (ICD). Reviewe July 2016. Available at <http://www.nhsgoldenjubilee.co.uk/files/9614/7558/8846/implantable_cardioverter_defibrillator_V2.p df > Accessed 03 March 2017.
Pacemakers and Implantable Cardioverter Defibrillators. Available at <http://emedicine.medscape.com/article/162245-overview#a2> Accessed 4 March 2017.
Pacemakers and Implantable Cardioverter-Defibrillators. Updated 13.2.2017. Available at < http://emedicine.medscape.com/article/162245-overview#a3 > Accessed 06 March 2017.
Patient education: Implantable cardioverter-defibrillators (Beyond the Basics). Updated February 2017. Available at < http://www.uptodate.com/contents/implantable-cardioverter-defibrillators-beyond-thebasics > Accessed 06 March 2017.