ECG Kindergarten

An electrocardiogram measures the electrical signals that travel through the heart while it beats.  Doctors are looking at how long it takes the electrical wave to pass through the heart, as well as how much signal there is.

The printout from an ECG is more than just a bunch of squiggly lines.  A closer look will reveal that not only are there squiggly lines, but there are also a few letters and numbers scattered about the page.  What does it all mean?

ecgStrip Leads

All Those Wires

If you have an ECG done, you’ll rest flat on your back and they’ll hook up a bunch of electrodes. It does not hurt.  These electrodes allow the doctor to look at the heart’s electrical activity from different angles.

To illustrate how this works, consider these pictures:

Nativity

These pictures are quite different but they’re all photos of the same thing, just from different angles.  Likewise, the different leads used in an ECG give doctors heart-activity pictures from a bunch of different angles.  It’s one heart, but the electrical waves look different depending on your perspective.

Chest Electrodes and Their Leads

Six electrodes are attached to the chest at specific places to provide a picture of how the heart is functioning. These six chest electrodes show the electrical signal looking from the horizontal plane.

  • V1 and V2 look at the heart from the center (septal)
  • V3 and V4 look at the heart from the front (anterior)
  • V5 and V6 look at the heart from the side (lateral)

Limb Electrodes and Their Leads

There will also be an electrode for each limb: right arm, right leg, left arm, left leg. One peculiar thing is that the leg electrodes can be positioned anywhere between your torso and ankle.  As long as they’re the same location on both sides of the body it doesn’t seem to matter (I’ve had them near my ankle and also had them on my lower abdomen, and was confused about the variation depending on who’s doing the test – but now it makes more sense).  These limb electrodes generate views from a vertical plane.

  • When measuring the flow of electricity toward the right arm, this is called augmented vector right (aVR)

  • When measuring the flow of electricity toward the left arm, this is called augmented vector left (aVL)
  • When measuring the flow of electricity toward the left foot, this is called augmented vector foot (aVF)
  • When measuring the flow of electricity toward the right foot – nope, that doesn’t happen. They only consider the left electrode; the one on the right is neutral.

 

Maybe you’re puzzled, as I was, about how it can be a 12-lead ECG when there are only ten electrodes (6 chest + 4 limbs).  It turns out that leads are not synonymous with electrodes.  The six electrodes for the chest are the same as the leads, but to understand the others, we have to recognize that those leads are made up of pairs of electrodes.  Think back to high school science class and what we learned about electricity.  Or maybe it might help to picture the terminals on your car battery, where we know that electricity flows from the negative to the positive.

An ECG also measures the flow between the limb electrodes (from negative to positive):

  • Lead I measures the flow from the right arm’s electrode to the left arm’s electrode
  • Lead II measures the flow from the right arm to the left leg
  • Lead III measures the flow from the left arm to the left leg

If you ever want to have even a fuzzy idea of what your ECG shows, it’s important to know about the leads, because the printout of your heart’s rhythm will reference those leads.  The letters and numbers on the ECG’s printout are referring to the lead used for that portion of the tracing.  The ten electrodes give twelve leads: six chest and six limb.

The Strip (Printout)

The printout from an ECG shows the heart’s electrical signal as waves.

  • If there is no electrical impulse, the line on the ECG is basically flat. This is called the baseline.
  • When an electrical impulse is travelling toward a lead, the line on the graph will move upward.
  • When an electrical impulse is travelling away from a lead, the line on the graph will move downward.

Just as the front and back of my nativity scene look very different, waves look different depending on which lead is being used.  For example, this shows the same heartbeats as seen from two different leads:

ecg updown

But what does it mean?  Notice that the squiggles seem to have a pattern.  Every distinct portion of the ECG means something specific. First the heart is at rest, and the horizontal line showing no electrical activity is the baseline.

ECGPartsPtoT in colorThe P-wave indicates the heart’s electrical signal traveling through the atria (top chambers of the heart).

Following the P-wave, the QRS complex shows the electrical signal traveling through the ventricles (bottom part of the heart).  When this happens, the ventricles contract and the atria re-set.

The T-wave indicates that the ventricles are resetting and getting ready for the next heartbeat.

ecg contractions

When we combine what we know about leads with what we know about these waves, we can look at the printout from an ECG and see how it all fits together.  This illustration is color-coded to show which leads view the heart from different angles, and where that information shows on the ECG’s printout.

Certainly this isn’t enough information to allow patients to read an ECG, but it does give us some background to have a hope of understanding what doctors are saying if they ever attempt to explain what they’re seeing on the printout of our electrocardiogram.

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About Pericarditis ECG’s:

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There’s always something new…

RA doesn’t just affect joints.  It can affect the lungs, kidneys, pancreas, and so on – all the body’s systems.  That’s a problem with a systemic disease.

Although I had thought my disease was fairly well controlled, it turns out that even though my joints seem to be okay, and my labs look fantastic, there’s hidden inflammation wreaking havoc internally.  In my ongoing learn-A&P-by-malfunction life-course, I now get to learn all about pericarditis.

Pericard-itis is exactly what it sounds like it would be: inflammation of the pericardium.  And if you’ve ever taken Greek (thank you, Dr. Pecota), the pericardium is exactly what it sounds like it might be:  peri is a preposition meaning around, and cardion means heart, so the pericardium means something around the heart.  Thus pericarditis is inflammation of the thin, double-walled sac that surrounds the heart.  And let me tell you, it hurts!

There are many potential causes of pericarditis, and one is autoimmune diseases like RA.  Other causes include infection, heart attack/surgery, cancer, chest injury, HIV, and TB.  But with RA/SLE/PsA as a risk factor, this is something that the autoimmune community really ought to know more about.

The main symptom is chest pain.  This is most commonly sharp, stabbing pain – particularly in the center.  If you’re atypical like me, it could be more of a dull ache.  Think of your entire sternum hurting.  If you have a history of costochondritis (inflammation of the joints where the ribs attach to the sternum), you might be tempted to dismiss pericarditis symptoms as a costochondritis flare.  We’re talking about chest pain, though.  Go see your doctor!

Other symptoms can include:

  • Fatigue
  • Shortness of breath or difficulty breathing
  • Coughing
  • Palpitations
  • Fever
  • Pain when swallowing

It’s important to know the symptoms and seek help when warranted.  Don’t blow this off as a minor flare.  When we have chest pain, we need an accurate diagnosis and a good treatment plan!

Easier said than done.  I ignored things for a couple weeks, until finally my family members were concerned and insisted that I see our doctor.  Now, I like my doctor, but am not looking for extra excuses to see him.  I tend to figure that if I ignore things long enough, they’ll get better on their own.  After all, the body has a remarkable ability to heal itself!  Nonetheless, to get family members off my back, I went to see my doctor.  He is usually pretty good at the MD’s poker face. Nothing fazes him.  But when we discussed the “what makes it better/worse” question and I told him that it helps to lean forward, he looked at me like I’d lost my mind.  I smiled, “What can I say?  I just report the symptoms. You get to figure out what they mean.”  As it turns out, it’s pretty well documented that sitting up and leaning forward can ease the chest pain associated with pericarditis.  Once the doctors gave a name to my symptoms and I was able to read about it, I exclaimed, “HA! I’m not crazy!”  Well, maybe I am, but not about this!

Tests

When you see your doctor for chest pain, tests will be done.  Lots of tests.  Doctors don’t like their patients dying, so take complaints of chest pain quite seriously.  Even if you insist that it’s not your heart, it’s your lungs, they will ignore you and focus on your heart.  Expect to have an electrocardiogram (ECG/EKG) done almost immediately.  This not only tells the doctor what your heart is doing at that moment, but can show evidence of a past heart attack.1

Stethoscopes are a great invention.  In the case of pericarditis, the layers of the pericardium can rub against one another, and doctors are often able to hear this rubbing.  It’s fascinating.  Painful, but fascinating.

Another test, but one that can’t be done in a lot of primary care offices, is an echocardiogram (echo). This is an ultrasound of the heart, and in addition to an ECG is one of the tests that can be used in diagnosing pericarditis.  Positive results are considered conclusive, however negative results are not.

A chest x-ray can show what’s going on with your lungs, and will also show if the heart is enlarged.

MRI can be done to check the thickness of the pericardium, but is not likely to be one of the tests ordered initially.

Labs might also be ordered.  This is especially true if you go to the ER from your doctor’s office.  They’ll completely ignore your pcp’s input and order a plethora of tests to measure inflammation and make sure you’re not having a heart attack.2

Types

  • Acute pericarditis appears suddenly and lasts fewer than three weeks.
  • Incessant pericarditis is continuous and usually lasts 4-6 weeks, but definitely less than 3 months.
  • Recurrent pericarditis is when symptoms of acute pericarditis resolve completely, the patient is symptom-free, and then 4-6 weeks later the symptoms occur again.
  • Chronic pericarditis lasts longer than 3 months.

The Art of Medicine

Eventually I saw a cardiologist.  He’s a fantastic guy.  He read the history my family doctor sent, listened to my story, did an exam, and read the ECG.  Tired of waiting for the ultra-slow wifi to work, he said, “Let’s do this the old fashioned way,” and retrieved a couple tomes from his office – including one that he said used to be the Bible of cardiology.  It was kinda neat to watch him look things up just to confirm he was remembering things accurately, and he showed me in his books what it says about RA and pericarditis. Then he told me that he’d check up-to-date once he had a better internet connection.

After that, he showed me my ECG and explained that the machine was reading it as normal, but that’s not how he read it.  And he carefully showed me the exact places on all those wiggly lines that he thinks look like my readings are abnormal, as if I were able to read ECG’s.  I can’t, but he made it sound fascinating, didn’t treat me like an idiot, and I’m tempted to get a book to see if I can pick up the basics of reading ECG’s.

Medicine isn’t just feeding data into a computer that turns around and spits out a diagnosis and treatment plan.  There’s an art to listening to patients, asking the right questions to get all the assorted symptoms that the patient didn’t even think to mention, and putting everything together.  Then after determining a diagnosis, doctors still need to figure out a treatment plan.  Every patient is different.

Treatment

Since this is inflammation, it makes sense that anti-inflammatories would be the first line of treatment.  But RA patients already know to take ibuprofen before bothering their doctors with a little inflammation, which means my cardiologist jumped directly to the next step.

Colchicine is a gout medicine that works to reduce inflammation, and is one of the most common pericarditis treatments.  My insurance has this as a Tier II med, so be forewarned.  The most common side effect is needing frequent trips to the bathroom with lots of TP and air freshener, but if you’re already taking something like sulfasalazine, that is unlikely to be a problem 🙂

Steroids can also be prescribed to reduce the inflammation.  It’s nice to know there are options if the colchicine doesn’t work.  Frankly, given the cost difference, my personal preference would be to deal with prednisone, but there’s the usual love/hate issue when that medicine is prescribed.

Here’s hoping your life is less eventful!

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1 If the ECG’s automated results say “inferior infarct, age undetermined” do not panic. It might mean that you had a small heart attack at some time in the past, but it also might mean that the machine isn’t particularly reliable and your results should be interpreted by a skilled cardiologist who will say, “don’t worry; you’re fine.”  If the doctor says, “Don’t worry; the machine doesn’t know what it’s talking about,” believe the doctor.

2 If you go to the ER from your doctor’s office, they’ll repeat the ECG and also draw blood to run every test possible in an effort to discover whether or not you’re having a heart attack.  When they announce that you’re not having a heart attack, feel free to respond, “Nobody ever thought I was having a heart attack. I am here because my doctor told me to come here for an echocardiogram because none of the cardiologists can see me sooner than two weeks.”  Better yet, it might be appropriate to be proactive at the very beginning of the visit and insist that they enter “sent by pcp for an echo” as your chief complaint, or they’ll get it all wrong and think that you’re there for chest pain.  To tell the truth, the ER is a horrible experience and if I’m ever sent again, I will take with me the name of the ER doctor with whom my pcp spoke.  And if it’s the height of flu season, beg to be sent anywhere else.