Pacemakers are typically implanted for slow heartbeats. Defibrillators are recommended for patients who have had malignant ventricular arrhythmias such as ventricular tachycardia or ventricular fibrillation causing sudden cardiac death or patients at risk for these events.

The defibrillator shocks the heart out of these life threatening arrhythmias. These devices typically take an hour to an hour and a half to implant. Patients are generally kept in the hospital overnight but in some instances can even be sent home on the same day.

These devices are placed transvenously with wires running into the heart. In general these devices do not limit a patient's activities or the lifestyle. In fact, the newer generations of these devices are even compatible with MRI scanning.

These devices can now be followed remotely from home, with data transmitted to the physician’s office. Variations include subcutaneous defibrillators, HIS Bundle Pacing, cardiac resynchronization therapy, as well as remote monitoring of implantable devices.

Below: A defibrillator implant procedure. (A pacemaker implant is performed in the same way.)

Subcutaneous (SQ) AICD Implantation

This automatic implantable defibrillator from Boston Scientific Corp. was recently approved to treat sudden cardiac death. Conventional implanted defibrillators require leads be placed through veins and placed directly into the heart. This novel device avoids placing any leads into the heart. Placing leads through blood vessels to the inside of the heart can cause acute problems during the implant of a defibrillator, including cardiac perforation or a collapsed lung. In the longer term, endocardial leads have been shown, especially over time, to ultimately fail to function. They can also cause vessel obstruction, valve malfunction, or become infected. This newer device avoids these complications.

The lead used with this device runs subcutaneously, under the skin over the front of the chest. Again, there is no "hardware" placed in the blood vessels or heart. The shock waveform is delivered between the lead and the device itself.

Notice there is no lead in the heart or blood vessels:
Here is a conventional AICD, where there is lead in both the heart and blood vessels:


The SQ AICD is not recommended for those who need pacing for bradycardia or cardiac resychronization.

This device may be ideal for young patients especially, so they can avoid the long term problems associated with endocardial/endovascular leads.

Micra Transcatheter Implanted Pacemaker (No Leads)

Dr. Steven Zweibel and Dr. Meir Friedman were the first doctors at Hartford Hospital to implant a micra transcather pacemaker, a technology that avoids wires (pacemaker leads) and the surgical creation of a pacemaker pocket by implanting the device directly into the heart. (It's implanted via the femoral vein. Click here for a manufacturer's video of the implantation procedure.)

"Because the Micra pacing system has no leads like a traditional pacemaker," says Dr. Zweibel, "complications such as dislodgment or fracture of these wires are eliminated. There is also a lower risk of infection and there is no visible scar, like we see with traditional pacemakers. The Micra pacemaker is MRI-compatible and has a battery longevity of about 12 years. It also has the ability to increase a patient’s heart rate for them when their heart is unable to."

Learn more from Dr. Steven Zweibel, director of electrophysiology at Hartford Hospital:


Q: Is Micra the right pacemaker for all patients?
A: No. Micra is intended for patients who need a single chamber pacemaker (also known as a ventricular pacemaker, or VVIR). Talk  to your doctor about the suitability, benefits, and risks of Micra for you.

Q: How is Micra placed into my heart?
A: Your doctor will insert a "straw-like" catheter into a vein in your upper thigh and use the catheter to move Micra into the right ventricle of your heart. The catheter is then removed. 

A: Micra was designed, tested and approved to be used safely with MRI scanners. You can undergo an MRI scan as long as patient eligibility requirements are met. Your pacemaker ID card specifies the implanted device model. If your doctor has questions about scanning eligibility, he or she should contact a Medtronic representative or Medtronic Technical Services.  

Q: Will items containing magnets affect my Micra?
A: Maybe. We recommend keeping items containing magnets at least 6 inches away from an implanted pacemaker. This includes mobile phones, magnetic therapy products, stereo speakers, and handheld massagers. We do not recommend putting a mobile phone in your shirt pocket or using magnetic mattress pads and pillows.

Q: Is it safe to go through an airport metal detector?
A: Yes, you can safely go through airport security with this device.

Q: Are household appliances safe to use?
A: Yes, household appliances that are properly maintained and in good working order are safe. This includes microwave ovens, major appliances, electric blankets, and heating pads.

Q: Can I exercise, resume my regular activities?
A: Yes, you should be able to return to your usual activities, as long you do not exceed your fitness level. Discuss questions about specific activities with your doctor.

Q: Does Micra last forever?
A: No, Micra has a battery and the battery life depends on your heart condition. The estimated average longevity is 12 years. Individual patient experience may vary. Your doctor will check on the battery when you come in for a checkup. 

Q: What happens when the Micra battery runs low?
A: Micra is designed to provide options when a new device is needed. It may be turned off and a new Micra or a traditional system may be implanted. The Micra also offers a retrieval feature to enable retrieval, when possible. Your doctor will determine what is best for you.

Q: How often will I need to visit the doctor after Micra is implanted?
A: Your doctor will decide how often he or she wants to see you. Typically, your first follow-up appointment is one month after implant, with additional follow-ups every 6-12 months.

HIS Bundle Pacing

This newer pacing technology involves placing a pacing lead at the area of the HIS bundle, or bundle of HIS.  This electricalbundle is part of the natural electrical conduction system of the heart, branching into the Right bundle branch and Left bundle branch, which rapidly transmit electrical signals to the Right and Left ventricles.

The advantage of pacing the bundle of HIS is that the electrical signals then travel over the normal pathways of the natural electrical system, rapidly reaching the two ventricles simultaneously, avoiding dyssynchrony (electrical delay between the 2 ventricles, which can cause inefficient contraction of the ventricles and even weakening of the heart muscle). 

The technique can be a bit challenging, as it involves screwing a pacing lead into a very specific area, and is not always successful. However, when it is successful, pacing this area can closely mimic normal electrical activity and overcome the disadvantages of pacing the ventricles in areas far away from the natural electrical system.

When Bluetooth Meets Pacemaker

Dr. Steven Zweibel, director of electrophysiology at Hartford Hospital on the Bluetooth-enabled Azure pacemaker:

Q: Describe how does this technology works.
A: For decades, we used technology to have a pacemaker communicate with a special monitor so that we can remotely track the function of a pacemaker device. Studies have shown that this remote monitoring helps reduce mortality. Twenty-first century advancements allow for these new devices to make use of Bluetooth technology coupled with a smartphone app to allow monitoring via their mobile device.  The same information that we receive via the bedside monitor can now be sent via their mobile device. This can give us more timely information about arrhythmias or issues with the device.  Since the app on the patient’s mobile device is a piece of software, there is the ability to upgrade the app to provide new functionality. An example of an advance that I can envision in the future would be the ability for the device to detect when a patient has fallen and contact a family member or healthcare provider automatically.


Q: How secure is the transfer of patient data?
A: The data between the patient’s pacemaker and mobile device is fully encrypted, as is the data going from the mobile device to (device manufacturer) Medtronic and then to our device clinic.  It is very important to note that the patient’s pacemaker works completely independently from their mobile device and that no changes to the programming of the pacemaker can be done via the patient’s mobile device.

Q: This new pacemaker is unique in another way: It’s compatible with MRI imaging.
A:  Most devices that we implant at Hartford Hospital, including pacemakers and defibrillators, are now MRI compatible, and have been for a few years. This new pacemaker is no exception.  This has been a great advance for our patients to allow them to have the option of having an MRI scan, when previously this was not possible.

Q:  Describe more of the benefits of pacemaker technology today.
A: Device companies have been working very hard on battery and circuitry technology to make these devices last as long as possible.  I used to tell patients that their pacemaker would last 7 to 10 years. Now I can safely tell them that they should expect to get at least 12 to 14 years from their pacemaker battery. This will lead to fewer operations to replace their device when the battery becomes depleted.

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