Monday, May 1, 2023

A woman in her 60s with large T-waves. Are they hyperacute, hyperkalemic, or something else?

 Case written by Brandon Friedman M.D., edits by Meyers

A woman in her 60s with a history of chronic atrial fibrillation on Eliquis, ESRD on hemodialysis, type-II diabetes mellitus, prior CVA, hypertension, and hyperlipidemia presented to the emergency department with multiple complaints after missing dialysis. She described a feeling of general unwellness, diarrhea, right-sided abdominal pain, bilateral leg pain, bilateral leg swelling, and diffuse itching. She missed her last two dialysis appointments, with her last session occurring one week prior to presentation. On initial assessment, she was found to be tachycardic, for which an ECG was ordered and is shown below (no prior available):

What do you think?

When first evaluating this ECG, the physicians taking care of her were immediately concern about the T waves in multiple leads, especially the inferior leads where they appear too large for their QRS complexes. They were considering hyperkalemic or hyperacute T waves there. 

Due to the patient’s reported history of missing dialysis, the high-voltage of the T-waves initially raised concern for hyperkalemia. A VBG was ordered, which reported a normal potassium level of 4.9 mmol/L. This value was subsequently confirmed as 5.0 mmol/L on a formal electrolyte panel.

So if the high-voltage T-waves are not a result of hyperkalemia, what’s causing them to be so large? 

Like the team did in this case, let's start over from the beginning and interpret the entire ECG systematically, beginning with the rhythm.

First, we have a narrow-complex, regular tachycardia, with a rate of about 135-140. This narrows our differential for the rhythm down to sinus tachycardia, paroxysmal supraventricular tachycardia (PSVT, or SVT), and atrial flutter. The patient’s history is notable for paroxysmal atrial fibrillation, which raises clinical suspicion for atrial flutter, since these two entities frequently coexist on a spectrum. A closer look at the ECG demonstrates regular atrial waves in many leads, at exactly double the rate of the QRS complexes. They are flutter waves, and the rhythm is 2:1 atrial flutter. There is also a single premature beat, likely a PVC.

Lead V1, for example should generally have up-down biphasic P wavs in sinus rhythm, but in this case they are down-up (mostly up), and thus cannot be sinus P waves. Paying attention to leads II, III, and aVF, the flutter waves are highlighted by the arrows below. The flutter waves are super-imposed on the T-waves, which results in the broad-based slow up-slurring of the T-waves, as well as their apparent increased voltage. Further, these T-wave changes are only notable in some leads, and aren’t seen in all leads (such as lead I, where the flutter waves are basically not seen at all, leaving only the normal T waves seen there). 

She underwent urgent hemodialysis for volume overload, with improvement in her presenting symptoms. She also received IV metoprolol for rate control, with good effect.

Here is her ECG after rate control:

Records revealed chronic atrial fib/flutter, and rhythm control was not attempted during this admission.

Her rate control regimen was stabilized on carvedilol and diltiazem. She was discharged home.

Learning Points:

Atrial flutter can be very tricky to identify, and can cause all kinds of problems such as mimicking or concealing ischemia and OMI. In this case it caused perceived large T waves mimicking hyperacute T waves.

See these related cases:

A 50 year old man with sudden altered mental status and inferior STE. Would you give lytics? Yes, but not because of the ECG!


MY Comment, by KEN GRAUER, MD (5/1/2023):


In my experience — Atrial Flutter (AFlutter) is by far, the most commonly overlooked cardiac arrhythmia. The reason for this is easy to understand — atrial activity is often not well seen in many instances of this arrhythmia. And so it was, that AFlutter was not initially recognized in today's case.
  • I focus my comment on several additional suggestions to the above discussion by Drs. Friedman and Meyers — in the hope of facilitating recognition of this sometimes elusive arrhythmia.

For those interested in more on "My Take" for recognizing AFlutter — Please CHECK OUT:
  • The November 12, 2019 post in Dr. Smith's ECG Blog — in which I walk through a step-by-step approach on an even more subtle case of AFlutter than the one presented today.
  • My Comment in the March 6, 2020 post — in which I review assessment of atrial activity (and RP' intervals) in reentry SVT rhythms

For clarity in Figure-1 — I've reproduced today's initial tracing, in which I've labeled atrial activity in the 5 KEY leads.

Figure-1: The initial ECG in today's case.

Application to Today's Tracing:
The following considerations may help to avoid overlooking AFlutter:
  • Assuming your patient is stable (and not in need of immediate cardioversion) — regular use of a systematic approach to rhythm interpretation is the BEST way not to overlook subtle (as well as not-so-subtle) ECG findings. This does not slow you down! Once your system becomes automatic — you'll find it of invaluable assistance! (You'll also find your speed and accuracy in arrhythmia interpretation has increased — because you don't have to constantly go back-and-forth repeating your efforts).

  • Those who follow Dr. Smith's ECG Blog know that I favor the Ps, Qs, 3R System for rhythm interpretation. For example, in Figure-1 — it took me less than 5-10 seconds to appreciate that normal sinus P waves are absent (ie, the lack of a clearly monophasic upright P wave in lead II) — that the QRS is narrow (therefore the rhythm is supraventricular) — that the Rhythm is regular at a Rate of ~135-140/minute — and that although "normal" sinus P waves are absent, there still is some Relation between atrial activity and neighboring QRS complexes (because the distance between the BLUE lines in Figure-1 and neighboring QRS complexes is constant!).

  • Thus, by the Ps, Qs, 3Rs — I was able within seconds to define today's rhythm as a regular SVT at ~135-140/minute, but without clear evidence of sinus P waves. Awareness that 90-95% of regular SVTs seen in an emergency situation will be 1 of 4 entities — simplifies our task for determining the specific etiology. The differential diagnosis is: i) Sinus tachycardia; ii) A reentry SVT rhythm (ie, AVNRT, orthodromic AVRT)iii) Atrial Flutter (AFlutter) — or  iv) Atrial Tachycardia (ATach).
  • Awareness that by far (!) — the most commonly missed arrhythmia is AFlutter — makes me always suspect this possibility whenever the rhythm in front of me is a regular SVT close to 150/minute, without clear evidence of normal sinus P waves. In this situation — Think AFlutter until you prove otherwise (and then you will not overlook this diagnosis)!

  • The MOST COMMON mistake I've seen even "experienced" clinicians make — was committed by the physicians who first saw today's initial ECG. There were "concerned about T waves being too large for the QRS" — without any mention of what the rhythm was! The way to avoid this oversight is simple: Promise yourself that for each ECG you encounter — you will spend an initial 2-to-3 seconds for your educated eye to look at each beat in the long lead rhythm strip(s) at the bottom of the tracing to ensure that an upright P wave appears in lead II with fixed PR interval before each QRS complex — and that no "extra deflections" are present. Doing so in Figure-1 — would have immediately suggested that lead II did not clearly have "normal" sinus P waves — and that there appear to be 2 atrial deflections for each QRS in lead V1.

  • Using calipers saves time — and — makes you smarter! To emphasize — I do not advocate using calipers when the patient in front of you is crashing because of a tachyarrhythmia. In such cases — the rhythm no longer matters, because immediate cardioversion is needed regardless of what the rhythm turns out to be! But it literally takes me no more than 5-to-10 seconds to look for flutter waves by setting my calipers at precisely half the R-R interval — and searching in key leads to see if 2:1 atrial activity is present.
  • My GO TO leads for identifying atrial activity are: i) Lead II — which is typically the BEST lead for identifying atrial activity. In AFlutter — leads III and aVF also usually provide ready evidence of 2:1 atrial activity; ii) Lead V1 — Next to lead II, lead V1 is often the 2nd-best lead in my experience for identifying atrial activity. With AFlutter — one will often see positive deflections similar to those suggested by the BLUE lines in Figure-1 in this V1 lead; iii) Lead aVR is often surprisingly helpful for identifying atrial activity (BLUE lines in ECG #1); andiv) IF none of the above leads suggest atrial activity — then I’ll survey the remaining 7 leads as I look for atrial activity. That said, AFlutter will almost always provide ready evidence of atrial activity in one or more of my “Go To” leads.
  • Since the ventricular rate in ECG #1 is between 135-140/minute — and since BLUE lines in Figure-1 clearly indicate the presence of 2:1 AV activity — the atrial rate in ECG #1 = 2 X 135-140 = 270-280/minute. In addition to the "sawtooth" appearance in each of the inferior leads — this rapid an atrial rate strongly favors AFlutter (rather than ATach) as the diagnosis!

  • With respect to today's case — Know that flutter waves can be large — and when they are, flutter waves may superimpose on the ST-T wave and simulate ST elevation or peaked T waves (as they do in today's case). Realize that until the ventricular rate is controlled — we won't know what the "real" ST-T wave looks like. 

  • PEARL #1: For challenging arrhythmias in which I just don't see atrial activity during the tachycardia — I look for a "break" in the rhythm. We see such a "break" in Figure-1, as a result of the PVCRED lines just before and after this PVC — show that regular flutter waves continue (and are better seen, at least in lead II) before and after the PVC that resets the ventricular rhythm, than in the rest of the long lead II rhythm strip.
  • PEARL #2: On occasion — atrial activity may not be readily apparent in a hemodynamically stable patient with a tachyarrhythmia. In such cases — use of an alternative lead system, such as a Lewis Lead may enhance atrial activity and facilitate rhythm determination. Figure-2 reviews how to use a Lewis Lead. The March 20, 2018 post on Dr. Smith’s ECG Blog illustrates application of a Lewis Lead in a patient in a regular SVT rhythm.

Figure-2: Use of a Lewis Lead (See text). 

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