A 40 year old with nonspecific symptoms including dizziness

A 40 year old with nonspecific symptoms including dizziness.

What do you notice about the ECG?

There is a very short QT interval.  This is often found in hypercalcemia.  See Ken Grauer's comments below for detail.

Thus, the patient's chemistry was done and revealed ionized hypercalcemia of 6.3 mg/dL (normal 4.4 - 5.2)

Followup: he was found to have hyperparathyroidism

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

MY Comment, by KEN GRAUER, MD (9/12/2023):

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

Today's ECG is remarkable for an uncommon but important finding that we periodically review, because it otherwise is all-too-easy to overlook. For example — Did YOU notice the short QTc interval in today’s tracing?

• PEARL #1: The BEST way to ensure that potentially important subtle findings (such as the short QTc in today's case) are not overlooked — is to BE systematic in your approach to ECG interpretation. 
• Regardless of whether you follow my system or prefer your own system that you've developed over time — one KEY is to always look at Intervals ( = the PR interval — QRS duration — the QTc interval) at an early point in the process. The reason to always look at intervals early — is that seeing an abnormal (or changing) PR interval — or, a wide QRS — or, a very long (or very short) QTc — will change how you interpret the rest of the tracing.
• 
  
• (For more on my systematic approach — Check out My Comment in the May 3, 2020 post).

Take another LOOK at today's ECG (which I've reproduced in Figure-1):

Figure-1: I’ve labeled the initial tracing in today’s case.

How Short is the QTc in Today's Tracing?

The QTc is determined by taking the longest QT interval that you can confidently measure on the 12-lead ECG — and then correcting this QT interval for heart rate.

• With heart rates over 60/minute (if using the Bazett formula) — the QTc will be more than the QT interval that you measure.
• With slower heart rates (under 60/minute, if using the Bazett formula) — the QTc will be less than the QT interval that you measure.

Looking at the 12-lead tracing in Figure-1 — I thought the longest QT interval that I could clearly measure was in lead V2. I measured 330 msec. = 8.2 little boxes (thin vertical RED lines in V2 showing from where I measured). 

• I thought the average heart rate in ECG #1 was ~75/minute (although there is slight variation in the R-R interval — with therefore slight variation in the heart rate).
• MD CALC is a handy link that provides near instant correction of the measured QT according to heart rate — allowing you to calculate the QTc by any of the 5 most commonly used corrective formulas ( = Bazett — Fridericia — Framingham — Hodges — Rautaharju). Plugging in the above numbers into MD CALC for a heart rate of 75/minute yielded results between 353-367 msec. for the QTc (depending on which of these 5 formulas you choose).

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

PEARL #2: For those interested — I long ago put together a user-friendly Correction Factor that has been surprisingly accurate for me in assessing QTc values that I’ve estimated over the past 3+ decades.  As per the text under the ECG in Figure-2 — you only need to remember 3 values (ie, 1.1 for a rate ~75/min; 1.2 for ~85/min; and 1.3 for ~100/minute). With a little practice using this method — you can estimate the QTc within seconds.

• Applying my method to today's ECG (that appears above in Figure-1) — Since the longest QT interval that I measured was 330 msec. (in lead V2 — as shown in Figure-1) — and the average heart rate was ~75/minute — I estimate the QTc = 330 + [330 X .1 = 33) = 330 + 33 ~363 msec. 
• For speed and ease of calculation — I usually round off values (it’s all an estimate anyway! ) — but as can be seen, my estimate of ~360 msec. is very close to the formula values calculated on the MD CALC site.

Figure-2: A rapid method for estimating the QTc (Figure from My Comment in the March 19, 2019 post in Dr. Smith's ECG Blog).

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

Clinical Implications of a Short QTc:

The differential diagnosis for today's tracing, with its short QTc ~360 msec. is: i) SQTS (Short QT Syndrome); and, ii) Hypercalcemia.

• Although we are told that today's patient is a man with hypercalcemia as a result of hyperparathyroidism  (with a significantly elevated ionized serum Ca++ level = 6.3 mg/dL — vs normal values = 4.4-5.2 mg/dL) — it is worthwhile reviewing both of the above entities responsible for a short QTc.

Features of Short QT Syndrome: 

From My Comment at the bottom of the page in the September 2, 2019 post of Dr. Smith’s ECG Blog:

• SQTS is an inherited cardiac channelopathy determined by the presence of symptoms (syncope, cardiac arrest) — positive family history — and the ECG finding of an abnormally short QTc interval.
• SQTS is a relatively new diagnosis that has only been recognized as a distinct clinical entity since 2000. The disorder is rare — but it takes on importance as a potential cause of atrial and ventricular arrhythmias, including cardiac arrest. Treatment is by ICD (implantable cardioverter defibrillator).
• 
  
• Males with a QTc ≤330 ms — and females with a QTc ≤340 ms are defined as having SQTS, even if they are asymptomatic.
• 
  
• Males with a QTc ≤360 ms — and females with a QTc ≤370 ms are said to have a “short” QTc. Such patients may have SQTS if, in addition to the "short" QTc — there is a history of cardiac arrest, unexplained syncope or atrial fibrillation at an early age.
• 
  
• Regarding Today’s Case: We were told that today's patient was a 40-year old man. In view of the QTc estimated for today's patient ~360 msec. — his ECG would qualify for the classification of a “short” QTc (but not quite short enough to qualify for SQTC). Assuming the patient did not have hypercalcemia and there was no history of cardiac arrest, unexplained syncope or AFib at an early age — cardiac risk from a “short” QTc is clearly less than for patients with frank SQTC.

The ECG Diagnosis of Hypercalcemia:

From My Comment at the bottom of the page in the October 30, 2020 post of Dr. Smith’s ECG Blog:

• While the textbook description of ECG findings of hypercalcemia is often limited to “QT interval shortening” — QT shortening is not an easy ECG finding to recognize (even when you are looking for it!). In addition, what is not described in textbooks — is how high the serum Ca++ must go before such QT interval shortening occurs. As Family Medicine Attending (working in and out of the hospital) — I religiously scrutinized the ECGs of all patients I encountered in whom serum calcium levels were elevated. In my experience — NO change in ECG appearance was noted in the overwhelming majority of hypercalcemic patients until their serum Ca++ level was significantly elevated (ie, a total calcium level over 12 mg/dL). KEY Point: — Do not expect to pick up hypercalcemia on ECG unless serum Ca++ is increased by a lot. (The ionized serum calcium level of 6.3 mEq/L in today’s case clearly qualifies as sufficiently elevated to produce ECG changes).
• 
  
• PEARL #3: More than simply QT interval “shortening” — the principal ECG finding of significant hypercalcemia is a short-Q-to-peak-of-T interval. By this I mean that the time it takes for the T wave to attain its peak is shortened with significant hypercalcemia. I know of no measurement to quantify this shortened time-until-T-wave-peak. Instead — it is a subjective judgment — that with experience (armed by an increased index of suspicion for the case-at-hand) YOU can learn to appreciate.
• Regarding Today's ECG — I chose the lead with the most ST-T wave deviation ( = lead V2 in Figure-1) to draw in 2 vertical BLUE lines highlighting the point where I thought definite “peaking of the T wave" is seen. Subjectively — Doesn’t the time until attaining this T wave peak seem short?