Saturday, June 15, 2019

Patient with Dyspnea. You are handed a triage ECG interpreted as "normal" by the computer.

I was handed this ECG of a patient with dyspnea:

What do you think?

Computer interpretation: Normal EKG
Physician Overread (Final interpretation): Normal EKG





















The ST segment is very flat, with a sudden rise to the peak of the T-wave.  This makes the base of the T-wave look very narrow.  A narrow-based T-wave is nearly pathognomonic for hyperkalemia.  My diagnosis was hyperkalemia.

The resident I showed it to saw nothing.  I explained all this to the resident, then went to see the patient.

Turns out he is a dialysis patient.

Later, the ECG computer interpretation was overread by another physician, and that physician thought it was normal, but took the step to compare with the most recent previous ECG.  There was no change, so that physician concluded that it was indeed normal and entered "Normal EKG" as the final diagnosis.

However, I looked a bit more in depth, and the previous ECG had also been recorded during hyperkalemia.

The K returned at 6.3 mEq/L.

Let's look at a couple previous ones from 2 years prior:

This was recorded when this patient presented with diaphoresis and muscle cramps:
The formal read was normal except for "possible old lateral MI"
QTc was measured at 484 ms which appears to be accurate, but the statement did not say "long QT"

There are definitely peaked T waves, and a long flat ST segment with an abrupt rise to the peak of the T-waves.

The K was 6.6 mEq/L

What else do you suspect?

This ECG was recorded a few hours later after bringing down the K to 4.8 mEq/L.:
These are now normal T-waves.
Can you see the difference between these and the T-waves in the 1st 2 ECGs?


Computer interpretation AND physician overread:
Normal except for long QT (486 ms)

The other thing you might have suspected is hypocalcemia, as the long QT is long because of a long ST segment (not because of a wide T-wave). 
The (not ionized) Ca on these 2 ECGs was 6.4 mg/dL (very low)
On the first ECG above, the QTc was 402 ms and the Calcium was normal.

The diagnosis was fluid overload and hyperkalemia.  Dialysis fixed both.

Learning Points:

1. Peaking of T-waves can be very subtle
2. Comparison with previous must be done with a previous that is recorded in the presence of a normal K.
3.  Peaked Ts are not necessarily large or tall.  They have a narrow base, and a sharp upstroke.  Often they look as though they would puncture you if you sat on them.
4.  Early repolarization and even LVH can have T-waves that mimic hyperK.
5. Having the physician read every EKG, whether the computer calls it normal or not, is of course only useful if the physician can recognize the abnormality

If you miss hyperK T-waves, your patient may have an unexpected cardiac arrest:

Here is a really interesting post, in which a patient with very subtly peaked T-waves, which are misinterpreted as early repolarization, has a ventricular fibrillation arrest before the K returns high:

HyperKalemia with Cardiac Arrest. 

Peaked T waves: Hyperacute (STEMI) vs. Early Repolarizaton vs. Hyperkalemia



===================================
Comment by KEN GRAUER, MD (6/15/2019):
===================================
Instructive case! I focus My Comments on ECG #1 = the initial ECG obtained in the ED (Figure-1). In my opinion, rather than calling this ECG “normal” (as did 2 clinicians and the computer) — there are ECG findings that should be noted: iProlonged QTc; iiLVH, clearly by voltage; iiiST segment straightening in multiple leads; andivTall, peaked (and pointed) T waves with a narrow base in at least 4 of the 6 chest leads. 
  • While I fully acknowledge that some of these ECG findings are subtle — I submit that recognition that this ECG is not “normal” would not have been overlooked IF interpreters had used a Systematic Approach (For “My Take” on how routine use of a Systematic Approach not only improves accuracy, but also speeds you up — See Dr. Smith’s May 7, 2019 Blog).
Figure-1: The initial ECG done in the ED (See text).

====================

Beginning with Descriptive Analysis:
  • There is baseline artifact in ECG #1 — which is most marked in the limb leads. That said, this does not prevent accurate interpretation of the key findings.
  • Rate & Rhythm — The rhythm is sinus at ~85/minute. Intervals  The PR interval is normal. The QRS complex is not wide. However, the QTc is somewhat prolonged. I measure the QT = 400 msec (See markings in lead V3). Correcting for the heart rate of 85/minute — I estimate a QTc ~470-480 msec (which is clearly above the upper expected range ~440 msec).
  • Axis  The frontal plane QRS axis is normal (about +30 degrees).
  • Chamber Enlargement — There is no atrial abnormality, and no RVH. But voltage criteria for LVH are definitely satisfied! I have reviewed “My Take” on a user-friendly approach to ECG diagnosis of LVH in Dr. Smith’s April 27, 2019 Blog. For ease of recall — I’ve excerpted the user-friendly criteria I favor in Figure-2. ECG #1 is an example in which the most commonly helpful criteria (35 & 12 — as per Figure-2) are negative — but both Cornell Criteria (R in aVL + S in V3 ≥28 for a manand especially Peguero Criteria (deepest S + S in V4 ≥28mm for a manare met. NOTE: Short, horizontal BLUE lines in leads V4 and V5 indicate the limits for R wave and S wave amplitude in these leads, in which overlap of complexes makes assessment a bit challenging.
  • Q-R-S-T Changes  There are small, narrow Q waves in leads V5 and V6 (most probably normal septal q waves). R Wave Progression — shows slightly delayed transition (the R becomes taller than the S wave is deep between lead V4-to-V5). ST-T Waves — show ST segment straightening (short PURPLE lines in leads V4,V5,V6) and frank ST flattening (PURPLE lines) in leads V2 and V3. This is not normal — as the ST segment should normally be gently upsloping (Please see My Comment in Dr. Smith’s June 9, 2019 Blog). And, there is even a hint of ST depression in leads V5 and V6.
  • As noted by Dr. Smith — it is because of this ST segment straightening and flattening in multiple chest leads — that the abnormal shape of the T waves in leads V2-thru-V6 should be noted. As a memory aid — the shape of the Eiffel Tower (= tall and rising to a point at the top, but with a surprisingly narrow base) — should recall the shape of typical hyerkalemic waves (See Figure-1).
Putting this Together to formulate your Clinical Impression:
  • After looking at the ECG in Figure-1 — my thoughts were that we needed to know more about this patient! I saw sinus rhythm — a prolonged QTc — definite LVH by voltage — and, ST segment straightening + flattening (and slight ST depression) T waves in multiple leads that strongly suggested hyperkalemia.
  • The fact that the QTc is prolonged in association with hyperkalemia should suggest that there may also be hypocalcemia (these 2 electrolyte abnormalities in patients with renal disease so often go hand-in-hand). Although sensitivity and specificity of the ECG is far from optimal for detection of hypocalcemia — the morphologic picture we see here (ie, with fairly straightened but not elevated ST segments, at the end of which appears a hyperkalemia-looking T wave) should strongly suggest this possibility, especially in a patient with severe renal disease.
  • NOTE  Marked LVH is very common in chronic dialysis patients. The reason why T waves in ECG #1 are not all that tall in multiple leads — and why ST-T wave changes typical for LV “strain” are not seen — might be that these 2 conditions are each attenuating ST-T wave effects of the other (ie, IF on a “baseline” of marked LVH + “strain”, serum K+ then becomes markedly elevated — then you might see exactly the ST-T wave pattern we see here in Figure-1in which there is diffuse ST straightening with slight lateral ST depression + relatively modest T wave height in most leads given the high K+ value = 6.3 mEq/L).
  • P.S.  Very important point emphasized by Dr. Smith! — when going back in the patient’s chart to look for prior tracings — BE SURE (as best you can) to determine the patient’s clinical status athe time the baseline” tracing was done. This is why peaked and pointed T waves looked “unchanged” from the first prior tracing in this case — when the patient’s serum K+ was also high ( = 6.6 mEq/L) at that time.

Figure-2: The user-friendly criteria I favor for ECG diagnosisof LVH (For my source —  CLICK HERE).



2 comments:

  1. Incredibly subtle ECG. Wonderful case. Interesting as I've heard lectures where people say that you won't get any ECG changes in hyperkalemia till the K gets to 6.8.

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