Robert’s Heart

I’m an electronic engineer by trade and a software engineer by training.  My cardiologist is not so different.  Our jobs are that of problem solvers.  To solve a problem:  1) Gather evidence,  2) Make an intelligent, educated guess,  3) Apply your educated guess.  The more empirical the evidence is the more accurate the guess is.  Don’t confuse engineering (the application of science) with science (the fact of knowing something).  In the cardiologists case it is obviously important to base your decisions on the best information possible.

In my last post, It’s My Heart I left off with my doctor having diagnosed me with vasovagal syncope.  Knowing this is wrong, I awoke at 4am and couldn’t sleep trying to figure out how to get a correct diagnosis.  I need to prove with empirical evidence to another engineer that my problem is rhythm related and not a reflex problem.  It comes down to being able to capture my issue on an ECG strip.  I either need to purchase or build an ECG machine.  My search revealed no consumer grade ECG machines which produce anything usable for less than $500.00, at least not that I could find.  I then searched for plans to build an ECG machine and I immediately came across this Scientific American Article.  It described a unit which amplifies the heart’s signal while not amplifying noise.  The output is a 1 volt peak-to-peak signal.  I then needed a way to capture this signal.  It didn’t take me long to remember that sound cards capture audio in a range that is compatible with a 1 volt peak-to-peak signal.

I spent some time on the internet and at the local electronics shop to purchase all of the parts needed.  I also needed some stick-on ECG electrodes to connect the leads to the skin.  Fortunately there are many sources for these on the internet.  For about $15.00 I purchased a pack of 50.

After building the ECG electronics and doing some limited testing I connected it up to my PC sound card and began to capture the data with the open source audio software Audacity.  This software is awesome software for novice and professional recording artists alike.  But the fact Audacity is free and graphs the audio signal were the overriding factors for me :-).  I hooked it all up and there is was.  An ECG:

Audacity ECG

At the time, I hadn’t realized how important using Audacity to capture the signal was.  It turns out that the filters available in Audacity are very important and allow me to cleanup any remaining noise in the signal.  Additionally I can capture hours of data then select only the sections that are important for review.

When I finally captured an SVT on the machine (4 months later) I needed to present this to the doctor.  My mom, a cardiac nurse, reviewed the data with me.  She found it difficult to review the data in Audacity because she had been trained as a cardiac nurse to read them on strips which have a graph paper background with specific timing.  Without this it is difficult to determine all of the important timing parameters of the ECG.  To present this data to my doctor I needed to convert it to strips he understands.

To convert from the raw audio data to a graphic strip I wrote a Perl script.  It converts 6 or 30 second audio captures into GIF files which are easy to print.  The script maps the audio timing onto the graph paper background that provide a reference for medical professionals.  All of the ECGs you see on this site were converted with this script.  Click Here For an Example

In the end the cardiologist acknowleged the SVT and we were back on track.  Still the diagnosis is “benign” SVTs.  While the word “benign” is great news they still don’t feel benign.  After time and time again being told they are benign I’m learning to live with them.  We are also trying to control them with meds.  More on the meds later.

So, on 12/30/07 I finally caught an SVT on the monitor (ECG: 12/30/07 SVT), that’s great. The problem is, that evening, I kept having them. While it was a bit uncomfortable it did give me an opportunity to capture some good information. Later in the evening on 12/30 I was monitoring myself when I caught a complete SVT and more… This SVT was particularly painful and had a feeling of significant pressure in my chest in addition to the usual light headed feeling. At about three and a half minutes into the SVT the pain and pressure went away, but I still had the arrhythmic feeling in my chest. The ECG still showed an arrhythmia, but it wasn’t regular like the SVT. The next morning my mom identified the irregular rhythm as Atrial Fibrillation. FYI My mom is a retired cardiac care nurse who has been a big help for me to understand (in a novice kinda way) what I’m looking at on the ECGs.

This strip (Click Here For The ECG) shows the beginning of the SVT. At about 14 seconds on that strip a “glitch” in the SVT causes it to speed up from what was 190 BPM to 232 BPM. That’s when the SVT became particularly uncomfortable.

This strip (Click Here For The ECG) shows the conversion from SVT to AF. It is pretty noisy because I was moving around at the time. After a few minutes the AF settled into about 140 BPM (Click Here For The ECG) and lasted for at least 15 minutes when I stopped monitoring. It did eventually, spontaneously, convert to a sinus rhythm.

I built the little ECG machine to capture an episode of supraventricular tachycardia (SVT) for the doctor. After waiting several months for something to occur I captured this SVT on December 30th 2007. It lasted several minutes. This SVT ran at about 220 beats per minute. This strip shows the last 2 seconds of the SVT and the conversion to sinus rhythm: Click Here To View

One of the first recordings I took with my homemade 3 lead ECG is this one. I took it on August 26th 2007.  It is a normal rhythm:  Click Here To View

My Nuclear Stress Test (earlier post) was prompted by an emergency room visit where I appeared (by my own account) to have short runs of ventricular tachycardia (VTAC). It had been my understanding that any VTAC was dangerous.

On Wednesday (7/16/08) I had been having some rather strong arrhythmias some felt like Supraventricular Tachycardia (SVTs). In the mid afternoon I had a few of these which caused me to have a light headed feeling. This has happened before when I’ve had SVTs. So, I hooked up my little 3 lead ECG and monitored my heart for a few minutes when I had a run of PVCs. At first it was 3 in a row every couple of minutes and occasionally it was 4 in a row. I ran these past my mom who is a retired cardiac care nurse. She confirmed that these were technically VTAC. She also indicated that I should be concerned. Moderately concerned I attempted to contact my doctor for an opinion (yeah right… just try to get a doctor on the line at 4:50 pm). A few minutes later I had a run of 9 beats of VTAC (3 seconds) (Click Here For The ECG). Now I’m concerned. If it can run for 3 then 4 then 9 beats… it can continue. “I’m going to the ER.” So I printed a copy of the ECG and headed there in earnest.

When I arrived in the ER the triage nurse took a look at my ECG and said “looks like VTAC.”

…skip a few hours of being hooked up and monitored plus blood tests…

ER Dr. says we want you to stay over night for monitoring. Ok… they agree this is concerning. I usually get “Benign Palpitations. Have a nice day.” With the tone: “Don’t let the door hit you in the ass on the way out.”

…skip being awakened every two hours for blood tests DOH!…

The next day my Cardiologist eventually came by to see me (about 1:30pm, and yes that’s an annoyed tone in my typing). He indicated these too were benign, but that I should probably be on a higher dose beta blocker and we should do a few more tests. Specifically a Nuclear Stress Test and a Cardiac MRI. He did confirm that technically this is VTAC. But it isn’t dangerous unless it becomes prolonged (i.e. I pass out). So if I pass out I should dial 911. Yeah right

I’m not so certain about the beta blocker thing. About 2 weeks ago I started a daily extended release beta blocker and this is the first time I’ve seen runs of PVCs. I monitor my heart whenever I have strong feelings of the arrhythmias. I would know if I had seen these before, and I haven’t. The cardiologist wants to basically double that dosage. I’ll discuss the beta blocker thing next time we talk.

Had several SVT’s yesterday (7/23/08) so I hooked up the homemade 3 Lead ECG to see what was up (I know I’m a freak). Monitoring Lead II for a short period of time I had an SVT and noticed something new today: Inverted P waves after the SVT converted to a sinus rhythm. I’m not certain what that means… but it’s new. I’ll have to print that one for my cardiologist.

At between 16 and 17 seconds on the ECG (Click Here For The ECG) the P wave inverts.

Come to think of it the SVT in this strip doesn’t really follow the normal pattern I’ve seen in the past. Hmm.