This patient with alcohol withdrawal and tachycardia had an ECG recorded:
|What do you think?
There is sinus tachycardia.
Look at the QT interval: it is far more than half the QT. The computer reads the QT at 386 ms, and QTc of 462 (proprietary correction formula unknown!)
Read this article:
I measure the QT at 440 ms. RR interval is 470 ms. It is possible that what we are seeing is a fusion of the T- and U-wave, but the consequences are similar.
Here is the QTc:
|Very long QT !!
(Fridericia is best; at heart rates over 60, Bazett results in a QT that is too long)
The magnesium returned at 1.2 mEq/L (low).
There was also a profound metabolic alkalosis, with K = 3.0 mEq/L.
The patient is at high risk of Torsades.
Do not trust the computer measurement of the QT interval when it looks long!