Category Archives: Biomedical Engineering

Biomedical Engineering

“Aftershocks” – why we try to better understand arrhythmias

Today while looking for other cardiac electrophysiology blogs (let me know if you find any — I cannot), I came across an article called “Aftershocks” by Elizabeth Ann Bartlett. Here are some excerpts:

In the four years I lived with an automatic implantable cardioversion defibrillator (AICD) while waiting for a heart transplant, I had only a few episodes of being shocked. But in each I was fully conscious and shocked multiple times. My experiences, some of which are described below, were horrific. I learned well the power of electricity not only to heal, but to harm.

I should note, however, that my experience with an AICD, although not unique, is not typical either. [ This is a bit of an edge case, sort of a worst-case scenario, and as she mentions, technology has improved since this was written. –Brock ]

Lub dub, lub dub, lubdub, lubdub. Faster and faster and faster. Boom boom boom boom POW! What was that? It nearly threw me to the floor. POW! again. It threw me to the bed. POW! What was this pain, this devil, this evil tormentor, in my chest? And then it stopped. Finally, it dawned on me that my defibrillator had gone off.

My heart had slowed a bit but was still racing. My husband called 911 and my neighbor, Nancy, a cardiac nurse. As paramedics struggled to get IV lines in, I felt myself slipping away. I’m going now, I thought, but no, BAM! There it was again. A stretch of calm, into the ambulance. BAM! BAM! Calm again. BAM!

BAM! Make it stop! Make it stop! BAM! I pleaded with God to end the torment, one way or the other.

I was shocked 16 times on the way to the hospital. Shocked into submission. I found myself begging for amiodarone.

This is truly terrifying to read. Every time her device was set off, it not only caused her pain, but damaged her already failing heart by literally blowing holes in the cells (electroporation). As highlighted by this slide from my CEP basics page, even in non-edge-case patients the psychological aftereffects of defibrillation are a real problem:

Psychological aftereffects of defibrillation
The paper mentioned in the slide is here.

Even eight years after the device was removed, says Bartlett,

the shocks, at least the physical sensations of them, still come on occasion. During the time the AICD was implanted, I was diagnosed with post-traumatic stress disorder from the shocking episodes; but I could not be treated with the normal therapy of removing myself from the situation—the perpetrator lived inside my body. I have suffered from flashbacks and nightmares, though these episodes have lessened over time.

Actual physical sensations of being shocked have hit me out of the blue—standing in a grocery line, teaching a class, in my early waking moments. A bright flash of lightning will bring it all right back. Other AICD patients I’ve known have experienced the same phenomenon.

She describes a defibrillator as a “torture device that [she] came to fear almost more than the death from which it supposedly was saving [her].”

It was almost certainly saving her. The fact that she has lived to be picked up by the paramedics in both episodes recounted in the article is good evidence of that. Nonetheless, the devices need to improve. Device manufacturers have pushed the envelope of improvement given the current knowledge of the heart and its problems. We have to better understand the problems and how to circumvent or eliminate them before the devices can improve much more.

And that’s what we’re working on.

Tools of the Trade

I’ve been thinking back on my trials and tribulations when working on the ischemia paper. One thing that tripped me up all along was a lack of knowledge of the techniques for analyzing cardiac electrophysiology data. Something that said, “if you want to find out why X is happening, first try Y and look for this, then try Z and look for that.”

Rather than whine about the lack of a list of such things, I’ve decided to start my own. I’ve added (or will shortly) a Page (on the right) called “Tools of the Trade”. There, I hope to document useful methodologies that I have used and that I use in the future.

Do you have any suggestions for analyzing electrical activity in the heart?

Recharging ICDs Wirelessly

As far as I know this is not an April Fool’s joke. The article is two days old, and the patent does apparently exist.

A company called powercast has developed a way to capture energy from radio waves at a variety of frequencies, and to thereby wirelessly power devices. There is huge potential here for the implantable pacemaker/defibrillator business, as the devices currently have to be (surgically) replaced when the batteries run out. I think the current lifetimes are around 10 years.