What do you think of this 12-lead? ***UPDATED

Without any details to accompany this tracing, what do you think?

(Hint: You probably won’t see too many similar strips at Prehospital 12-Lead ECG Blog or Dr. Smith’s ECG Blog, the two blogs on this subject that I visit the most.)



Thanks for all the responses. Reading through them, there are different opinions regarding this tracing.

I wasn’t sure if I wanted to post this relatively boring tracing in the first place, since the other blogs (ahem, Tom) always have way more exciting cases, but based on the feedback, it seems that we can have a worthwhile discussion about it. I’ll try to make it so you don’t feel like you’re wasting your time.

Let’s take a look at some of the boring technical stuff:

Rhythm: Normal sinus.

Rate: 67, regular.

P waves: Present, all the same shape.

PR: 0.154 s, constant, 1 P wave per QRS complex.

QRS: 0.104 s, constant, not quite at the 0.12 s cutoff that is generally used for BBB/IVCD. (Be sure to apply the full interval across ALL 12 of the leads, or you’ll mistake the terminal part of the QRS for ST-deviation, such as aVR in this case. It can also help measure J-points.)

QT: 0.368 s

QTc: 0.388 s

Lead placement: It doesn’t stick out to me as incorrect.

Frontal axis: Normal quadrant, probably closer to 90° than 0°.

Z axis: 50° posterior, which is a bit more posterior than normal, and possibly why I and aVF are both nearly isoelectric at the same time. (Picture this in 3-D space.)

Hypertrophy: R in V2 (22mm) + S in V5 (12mm) = 34mm, not quite at the 35mm cutoff that is generally used for LVH, but close. Anyway, it’s not a yes-or-no, hard cutoff.

U waves: Present in V1-V4. Seen in many cases, including LVH.

R-wave progression: Other than the late transition from negative to positive, it looks fairly normal to me without notable loss of amplitude. LBBB typically has poor R-wave progression in V1-V4, and so does anterior MI.

T-wave discordance: No lead really sticks out as abnormal. In any case, experts (not me) don’t really agree on which part of the QRS – terminal or dominant deflection – to use to determine T-wave concordance/discordance. I think it’s more of a pattern recognition thing; I just kind of know when I look at it.

Ischemia/infarction: The precordial T waves are fairly large, so are they hyperacute in the setting of an anterior MI? The J-point is mostly fuzzy, so there is arguably ST-depression in I, II, III, aVF and V6. There is ST-elevation in aVL and V1-V4. Along with the T waves, is this significant? How do we even measure the J-point? What to do?

This is why EKG interpretation remains, for the most part when it comes to crucial decisions, more of an art than a science. A lot of this goes back to pattern recognition, which only comes with looking at a lot of 12-leads. Some may say the concavity in V2-V4 is likely benign, possibly due to early repolarization. As different commenters pointed out, there are a number of things that may or may not be wrong with this tracing. I’d like to tell you that it goes without saying that the patient’s presentation and a thorough history are very important, but I keep running into crews who activate cath labs for 25-year-olds with toe pain. It also helps immensely if we have old EKGs for comparison. Of course, in the pre-hospital setting, we don’t usually have a lot of those lying around.

Well, fortunately, I happen to have a 12-lead of the same person from 2007.

With the exception of a few tenths of a millivolt in a couple of precordial leads, this tracing is pretty much the same as the one from 4 years ago.

Both tracings were obtained at routine medical exams administered by the person’s employer. Both were done properly – correct lead placement and connections – by the same provider.

One of the things I’ve slowly learned over the years is that while it’s sometimes difficult to identify badness on a 12-lead, it’s even more difficult to tell yourself to stand down and relax.

So, does this mean that these 12-leads show significant pathologies?

I don’t think so. I know it’s not a picture-perfect tracing, the ones you see when you Google “normal EKG,” but everything about human beings has a wide range of (usually) normal variants. In addition to normal variants, there are countless unhealthy people with normal baseline tracings. This is what makes things so difficult sometimes.

I think these tracings are fairly close to normal, for the most part. I know this because I feel pretty healthy.

Basics #1

Please remove most of the patient’s clothing as needed to properly visualize the complaint.

For instance, if I see multiple shirts still tucked in on someone with abdominal pain, I’m going to assume that you didn’t examine anything.

If you strap a major trauma patient to the longboard with clothes on, that means you’re either lazy (clothes are coming off somewhere and it had better begin with you in the field) or incompetent (you don’t realize this person is going to the trauma center).

Call review #2

Code 3 for chest pain.

This is not really a call review, since this is not what I do here, but I think it’s an interesting call in some ways.

A polite but anxious 53-year-old woman tells me she “bent over” and began feeling a discomfort in her chest with tightness in her throat. She tells me she has “an arrhythmia problem.” She does not know what specific arrhythmia. She has not heard of PSVT, A-fib, WPW, etc. She has no other significant medical history.

We convert her PSVT with Adenosine.

“How many times have you had similar events?”

“About 15 since I was a teenager.”

“You’ve never gone to the hospital for this?”

“No. They always stop. The longest one lasted 12 minutes. My cardiologist hasn’t been able to see what rhythm it is.”

She’s worn Holters without anything interesting showing up.

We medical people are a skeptical bunch – how often do we nod politely but dismiss it afterward when a patient tells us they have a medical problem that isn’t presenting with a tangible symptom that we can see?

Sometimes that’s just how things work out. She has been averaging more than 2 years between each event, so it’s totally conceivable that it hasn’t been captured on an EKG somewhere. If we didn’t see it today, she probably would have gone to her cardiologist for her 16th episode without making any progress toward any treatment plan.

Usually people know they have PSVT. But not always.

This reminds me of a patient in Garcia and Holtz’s 12-Lead ECG: The Art of Interpretation:

The first thing we noticed was the markedly prolonged QT interval. In case you have never seen a prolonged QT interval, this is as prolonged as it gets! Anyway, the patient recounted that, since she was a young adult, she would suddenly faint for no reason. She had seen many doctors, and they had no reason or diagnosis for the fainting. She was labeled a crackpot and placed on many antidepressant and antipsychotic medications over time. She lost her job because of the meds and became homeless. Her only statement was, “I’m really not crazy, I just fall out.”

Well, this doctor believed her, especially after looking at her ECG. Right after placing her on a monitor, the doctor started to examine her heart. He noticed that she slumped, and looked up to see her unresponsive. The monitor showed torsades de pointes. About 1 minute after she collapsed, during the chaos of gathering resuscitation equipment, she awoke and said, “See doc, I told you I pass out!” This poor patient’s life was ruined because no one saw a prolonged QT interval. She had Romano-Ward syndrome and ended up doing fine.

Not everyone lies. Even though it sure seems like it sometimes.


Call review #1 ***UPDATED

Code 3 for hypertension.

This is a 76-year-old female whose daughter called for a relatively sudden onset of weakness over the past hour. She speaks no English, and her daughter tells us that she’s been generally “fine” except that over the past week when taking a walk she’s been experiencing some mildly increased SOB that subsides with rest.

Pt appears just a tad tired, but otherwise looks fine.

VS: BP 221/83, P 40, R 18, SpO2 94% RA

In a moment of candor, the fire captain says, “I’m not sure what’s going on, but I heard someone say something about a block.” He hands me this from their Zoll:

What do you think? What do you do?

***Update #1:

So, it seems like most people have commented that this is a 3º AV block, which is what I was thinking when I looked at this first strip.

After some interrogation, her daughter tells us that the patient has a history of hypertension and breast cancer that was treated with a lumpectomy and chemotherapy a few years ago, which caused extensive heart damage, requiring the implantation of a pacemaker. She isn’t sure what kind of pacemaker it is, but she mentions that it only “came on sometimes” and does not think that it is constantly firing. She also mentions that the pacemaker was “adjusted” a month ago, but she has no details to offer.

Looking at the Zoll, I wonder if her pacemaker is firing.

We switch her to our LP12, and I’m a little disappointed (not that I wish people were sick, but you know what I mean). I was excited about the possibility of a decent call for a change, but this is turning out to be a bit anti-climactic. Here are a couple of strips, confirming what I half-suspected:


For those of you not familiar with the LP12, to limit distortion to the actual tracings, the default setting suppresses the pacemaker spikes, which are instead represented by the hollow arrows at the bottom of the strip.

It seems that the Zoll simply failed to detect the pacemaker firing, which, after a little research, is something that happens every now and then, according to Zoll themselves. (Probably the same situation with other monitors as well.)

And, here’s the cleanest copy of the 4 nearly-identical 12-leads obtained over 30 minutes:

It looks like there is intrinsic atrial firing at about 90 bpm without any conduction to the ventricles, which are paced consistently at pretty much exactly 40 bpm. I’m certainly no expert like Tom, who in his comments wondered about the possibility of a paced rhythm, but there are some who might say that leads II and III look like there’s concordant ST elevation (based on the positive terminal QRS deflections), whereas I feel that the first upward deflections are part of the T waves, rather than part of the QRS complexes.

VS: BP 212/102, P 40, R 18, SpO2 98% with oxygen 2L/min via cannula

BGL: 120mg/dL

It appears that the pacemaker is firing as intended without any apparent issues, other than the fact that the rate seems on the low side. I wonder if it’s intentionally set this way. And I wonder what pacemaker “adjustment” her daughter was referring to. We transport her code 2 with a saline lock, with the unopened pacing pads and the therapy cable on her lap. And a pair of shears in case I have to cut her shirt very quickly. (I hate cutting clothes if I can help it.) The ride goes without incident or any change in her condition. Her shirt survives. Her BP remains mostly the same.

We leave her at the ED, and a couple of hours later we bring someone else to the same hospital, which is coincidentally the area cardiac receiving center. I check with the original nurse, who says that the rep from the pacemaker manufacturer is in the room.

It’s not often we get to talk to these pacemaker reps. So, I go to meet her. She tells me that the patient has a dual-chamber demand pacemaker with a lower atrial rate limit of 80 bpm and a lower ventricular rate limit of 40 bpm. It was set up this way because the patient previously had occasional brady-arrhythmias due to the chemotherapy but did not require a pacemaker that was always firing.

So, it is thought that some time over the past week, with her atrium still firing normally, she lost her ventricular portion of the rhythm for some reason(s) out of many possible reasons. And now her pacemaker is functioning as intended. Since it’s now the only way her ventricles are contracting effectively, 40 bpm – previously the last-resort rate – is too low. The rep adjusts it upwards to 60 bpm.

Interestingly, her BP is now in the 170s/90s range without any other interventions. No one has an answer for that.

As of this writing, there is no other significant finding.

I didn’t start this blog to write call reviews, but this call is interesting to me in a few ways from a training perspective. We teach crews to do all this stuff but we don’t do a good enough job of teaching them to think about what they’re going to do before they do it. I shudder when I think about how many ways this call could have gone wrong if we didn’t figure out that it was a paced rhythm and not 3º AV block. Even though we’re writing about it now with the benefit of hindsight, I personally know crews out there who would have immediately given this patient Atropine or started transcutaneous pacing based on that very first Zoll tracing.

Please don’t misunderstand me – I’m certainly NOT knocking anyone who thought this was 3º AV block based on the first Zoll strip, because that’s exactly what I was thinking, and without the pacemaker spikes, that’s what it looked like. What I am concerned about is the fact that there are crews out there who would jump right into treatment, unnecessarily in this case, without first looking at a patient who is at most in very mild distress, and without diligently gathering as much relevant information as possible.

Furthermore, over the past 5 years or so, with more and more such tools as 12-lead, CPAP, capnography, etc. at our disposal, EMS is slowly but surely shifting toward a new paradigm, and it’s much more important for us to thoroughly obtain findings and assess our options. It takes some discipline to take that extra minute or two, that extra deep breath, to make sure we do things right the first time. The old way in EMS of providing treatment as quickly as possible based on a limited history and assessment, other possibilities be damned, is thankfully falling out of favor (but not quickly enough). Using Lasix for pneumonia is probably the best example, out of many, of this mindset.

***Update #2:

Tom over at Prehospital 12-Lead ECG is posting a series on pacemakers.

Response to comments:

Regarding ST elevation, as Tom mentioned, the filters in monitor mode (3-lead, 4-lead, when not obtaining 12-leads) are set for different frequency ranges than in diagnostic mode (when obtaining 12-leads). As a result, ST elevation present in monitor mode may not be present in diagnostic mode. Anecdotally for me, every time someone has said “there’s ST elevation” on a call when looking at a 3-lead or 4-lead, I have yet to see it present on a 12-lead.