A New Seizure in a Healthy 20-something

A 20-something year old who is the picture of good health presented with a new onset seizure.  A witness described what sounded like a 3 minute tonic-clonic seizure.  Her seizure workup was negative and she was scheduled for an outpatient MRI and EEG.Because she was persistently tachycardic, an ECG was recorded.  At the time her K was 3.2 mEq/L:Here is the interpretation by the computer, confirmed by the over-reading physician:JUNCTIONAL TACHYCARDIAINTRAVENTRICULAR CONDUCTION DELAY [130+ ms QRS DURATION]ABNORMAL ECGP-R Interval 116 msQRS Interval 158 msQT Interval 422 msQTC Interval 485 msP Axis 259QRS Axis 88T Wave Axis 36What do you think?When I saw it, I was immediately alarmed:First, I think there are P-waves underneath all that artifact, so it is not a junctional rhythm.  The abnormality is in the QRS and QT intervals.  I measure QT at 500 ms, with Hodges correction (what our computer uses) = 582 ms, Bazett = 668 ms. Part of this long QT is thewide QRS, which the computer measured at 158 ms. If you deduct that extra QRS duration, you get a QT of 440 ms.  I think the QRS duration was also erroneously measured and it is really 130 ms.  Thus, the QT would be about 470 ms without this extra QRS duration, with the corrections at 552 ms (Hodges) and 628 (Bazett).  What constitutes a long QT in the setting of prolonged QRS such as LBBB, RBBB, and Paced rhythm is complicated and beyond the scope of this post, but suffic...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs