Saturday, July 26, 2014

How This Blog Got Going: MRI Safe and Conditional Pacemakers, Reprise

I have decided to return to the thing that I was working on when I started this blog ... an MRI conditional pacemaker. Specifically, an MRI conditional pacemaker for St. Jude Medical. At the time I was Lead Human Engineering Clinical Systems Engineer on this project. Before I go any further I would like to distinguish between MRI conditional and MRI safe devices. It is important to distinguish between the two.

MRI Conditional v. MRI Safe

Having an MRI safe implanted cardiac device is the ideal situation. If the cardiac device is MRI safe, it means that a device patient can be "popped" into an MRI without any changes to the device. For the patient it's just like the person does not have an implanted device. The only difference is that the resulting imagery from the MRI around the device may not be as good if the person did not have an implanted device. 

An MRI conditional device presents some significant procedural challenges to all those involved. If a person has an MRI conditional device, certain conditions must be met before the device patient is allowed to enter the MRI. When I was working at St. Jude Medical, changes in the settings that operate the device are required before the patient enters the MRI. Once scanning is complete, the settings need to be changed back to their normal, operational settings.

As of publication of this article, only one medical device company has a commercially available MRI safe pacemaker, Biotronik. St. Jude Medical and Medtronic have commercially available MRI conditional devices. 

When I was work at St. Jude, the only cardiac device being engineered to permit patients to have MRI scans were pacemakers. At the time ICDs and CRTs were not considered for MRI compatibility. However, apparently, Biotronik has developed an MRI conditional ICD that is commercially available ... at least in Europe.

There are other issues regarding MRI compatibility such as whether there are limits on the area that can be scanned a cardiac device patient ... something other than a full body scan. The allowable limits on how much can be scanned are continually in flux. But this particularly issue does not have anything to with the story I want to tell.

My Experience with the MRI Conditional Project

The St. Jude Medical MRI conditional pacemaker was engineered to enable patients to undergo an MRI scan. To insure that pacemaker patients would not be harmed by the scan required that the operating settings on the pacemaker be adjusted. (To make a long story short ... a change in the setting needed to make sure that the sensing lead to heart be turned off. The pacemaker could be changed to constant pace or turned off entirely if the patient is not pacemaker dependent ... as most pacemaker patients are.)

So the major problem in this entire issue was in regards to how to change the settings on the device? Who would do it, how would it be done, what would the settings be? Essentially three basic approaches were considered:
  1. Have the patient's cardiac physician or cardiac nurse go to the MRI center, lugging their device programmer with them, change the settings on the patient's device to those that are MRI compatible, wait for the scan to complete, reset the settings to normal and examine the patient to insure that the patient is OK.
  2. Have the settings changed remotely. The patient is at the MRI center, the cardiac professional is in the office, at the hospital or at home. This is known as "remote programming."  At the time this was something that the FDA did not allow. Using remote programming, the patient's device communicates wireless to a pacemaker communicator located at the MRI center. The cardiac professional sees a 30 second rhythm strip before setting the patient's device to the MRI settings and sees another 30 second rhythm strip after the changes have been made. (Just like an onsite cardiac professional would do.) The patient undergoes the scan. During that time, the professional can perform other tasks. Once the scan is complete, the cardiac profession changes the pacemaker settings back to normal and sees the before and after rhythm strips. 
  3. The pacemaker is programmed with two settings by the cardiac professional using the programmer. The first set of settings define the normal operation of the pacemaker. The second set are the MRI settings: that is, the settings of the pacemaker when the patient undergoes an MRI scan.  When the pacemaker patient goes to the MRI center, the MRI tech takes a wand (that's best way I can describe it.) and changes the settings from normal to MRI. Once the patient completes the MRI scan, the MRI tech uses the wand to change the patient's setting back to normal. 
I became quickly apparent that cardiac professionals had no interest in option 1. As it turned out St. Jude Medical chose the third approach. 

When the third approach was described, I had numerous objections ... mostly related to the device that would change the setting on the pacemaker. Thankfully, there have been substantial changes and upgrades made to the wand. However, I wanted to purse option 2, remote programming. And the desire to purse option 2 inspired me to start this blog ... hence the title Medical Monitoring & Remote Programming.

Wherefore Remote Programming?

Most physicians showed some hesitancy when it came to adopting remote programming. They saw it as unproven ... and they were right, it was (and so far as I know still is) unproven and still not acceptable to the FDA. However, many if not most were intrigued by the idea and thought that the technology should be pursued. Many clearly saw the potential value of the technology, the value of being able to monitor patients remotely with the potential ability to change cardiac device settings without the patient being in the office could be a revolution in patient care ... not only for people with chronic conditions like heart problems, diabetes or neurological problems that involve implanted devices, but potentially everyone. And it need not involve the need for implanted or wearable devices. We'll explore this in later postings.

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