This patient has a severe electrolyte abnormality. Can you tell from the ECG what it is? Show
Smith Impression: The ECG shows sinus tachycardia, some prolongation of the QT interval, and ST depression. None of these findings are specific to this patient's severe hypernatremia. With ST depression, one must entertain hypokalemia as well as ischemia, but the K was normal. Clinical History and Lab data: This patient complained of diarrhea, and attempted to treat his diarrhea with homemade electrolyte solution. He presented with altered mental status and his Na = 175 mmol/L. Other electrolytes were normal. His troponin was modestly elevated and the ST depression is probably due to demand ischemia. I don't believe you can make the diagnosis from the ECG. None of the findings on the ECG are attributable to hypernatremia. As far as I can tell, there are no typical ECG findings in the context of severe hypernatremia. One might guess that high extracellular Na would result in more rapid influx of Na during depolarization, and therefore a narrower QRS. On the other hand, it might also result in hyperpolarization of the membrane and thus slower depolarization. As for repolarization, one might make arguments both ways. I have not seen any experimental data nor heard arguments from experts who would know much more. In any case, the clinical data is scant. Here the QRS is 84 ms. While this is on the low end of normal. No ECG was recorded after normalization of the Na, but there was a prior ECG available and the QRS duration was 92 ms. So perhaps hypernatremia shortens the QRS a bit, but that is really conjecture at this point. There is this unfortunate case report, with a review: Another case here (unfortunately, although they show all 4 ECGs, they are too small, with low resolution, to
make conclusions. =================================== MY Comment by KEN GRAUER, MD (7/1/2020): =================================== The subject of today’s case relates to a particular electrolyte abnormality. We need to acknowledge at the outset, that other than for hyperkalemia — an “electrolyte disorder” will rarely be the primary indication for obtaining an ECG. That said — the ECG may provide invaluable assistance in assessing some patients with certain types of electrolyte disorders, especially for explaining some of the ST-T wave abnormalities that may be seen. KEY Point: An important concept to appreciate, is that some electrolyte disorders can (and should) be recognized immediately (ie, before blood test confirmation returns).
That said — many electrolyte disorders are not instantly recognizable from the ECG. This is the situation in today’s case. For clarity — I’ve reproduced the presenting ECG from today’s case in Figure-1.
My THOUGHTS on ECG #1: Although the history in today’s case should clearly make you suspicious of electrolyte disturbance (ie, The patient presented with altered mental status, after trying to treat his diarrhea at home with a self-made electrolyte solution) — I did not think his initial ECG was diagnostic.
Assessment of the QTc interval for ECG #1is worthy of discussion. In my experience — the clinical utility of assessing the QTc at faster heart rates is limited.
Returning to Systematic Assessment of ECG #1:
MY Clinical Impression of ECG #1:
Serum Sodium and the ECG:
QUESTION: In the interest of honing ECG interpretation skills — Consider the following 2 ECGs that are shown in Figure-2 (Both of these tracings are taken from the February 19, 2015 post in Dr. Smith’s ECG Blog).
ANSWERS: The rhythm in both tracings shown in Figure-2is sinus, albeit with bradycardia (as well as with lots of artifact) for ECG #2. That said — the principal abnormal findings relate to assessment of ST-T wave changes:
ECG #3 — The history in this case is insightful. My years in primary care taught me to be leery of older patients presenting with an unusual history of atypical pain in some specific part of their body. While clearly patients with “frozen shoulder” may experience exacerbations in the degree of their shoulder pain — I immediately became suspicious after hearing this history and seeing ECG #3, that the patient had hypercalcemia secondary to malignancy. The remarkable ECG finding in this tracing is a short QTc interval.
Concluding NOTE: We’ve featured numerous cases of hyper- and hypokalemia in prior blog posts. Simply enter either hyperkalemia or hypokalemia into the Search Bar on Dr. Smith’s ECG Blog if interested in finding ECG examples of these electrolyte disorders.
Which electrolyte imbalance shortens QT intervals on electrocardiogram tracings?Hypercalcemia. Elevated calcium level is defined as a level greater than 2.7 mmol/ L, with severe hypercalcemia being greater than 3.4 mmol/L. The most common EKG finding associated with hypercalcemia is shortening of the QT interval.
What electrolyte imbalances cause ECG changes?The most common and clinically most relevant electrolyte imbalances concern potassium, calcium and magnesium.. T-waves become wider with lower amplitudes. ... . ST segment depression develops and may, along with T-wave inversions, simulate ischemia.. What electrolyte imbalance causes ventricular tachycardia?This irregular rhythm happens most often in people with heart disease or a prior heart attack. It may also occur in those with electrolyte imbalances (such as high or low potassium levels).
What electrolyte causes peaked T wave?Peaked T Waves
These changes are often seen when the serum potassium exceeds 5.5 mEq/L. 1 , 2 The corrected QT interval is either normal or shortened.
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