Written by Pendell Meyers
A female in her 60s with COPD, DM, hypothyroidism, CAD, and severe bladder cancer presented from a nursing home with altered mental status, hypotension, hypoxia, and bradycardia.
Here is her initial ECG (no prior for comparison):
|What do you think?
Here is another ECG minutes later:
|There is a regular wide complex bradycardia.
There are P-waves at a rate of approximately 100bpm with no clear relationship to the QRS complexes, diagnostic of complete heart block.
The QRS morphology is wide (computer QRS duration 179 msec) but it does not fit any clear bundle branch block pattern (it is similar to LBBB but not truly LBBB).
The T-waves in the precordial leads are peaked. Overall this is highly concerning, if not diagnostic, for hyperkalemia.
Third degree heart block was recognized, but hyperkalemia was not initially. She was given push dose epinephrine and atropine with no change. External pacing was attempted but failed.
A transvenous pacemaker was then placed, with capture obtained:
|Ventricular paced rhythm.
Computerized QRS duration 192ms, but it appears to be ~200 msec in several leads.
It is unusual for any patient with any conduction pattern to reach 190-200 msec in the absence of hyperkalemia or other sodium channel blockade.
The J-point is not easy to find, but there is excessively discordant ST deviation in many leads (this is why we excluded hyperkalemic patients in our ventricular paced rhythm study of acute coronary occlusion using the modified Sgarbossa criteria!).
The first potassium level was reported to be hemolyzed by the laboratory.
She was placed on an epinephrine drip. Her mentation improved after pacing and epinephrine drip.
The second potassium then returned at 8.1 mEq/L. Labs confirmed new renal failure.
Around this time the patient’s family arrived and explained that the patient’s goals of care were palliative. Comfort care was instituted. The patient expired.
Hyperkalemia is an important cause of bradycardia and heart blocks.
Never place a transvenous pacemaker without considering hyperkalemia and a trial of IV calcium.
Comment by KEN GRAUER, MD (1/13/2019):
Superb case with essential teaching points by Dr. Pendell Meyers that have been emphasized many times on Dr. Smith’s blog, but which never cease to be insightful and instructive. As stressed by Dr. Meyers — HyperKalemia is an important cause of bradycardia and heart blocks! It needs to be given high priority whenever clinical circumstances are potentially consistent with this diagnosis.
- The goal of My Comment is to illustrate some advanced pointers in clinical arrhythmia interpretation. Although none of these pointers were “needed” for the essentials of diagnosis and management of this case — awareness of these ECG & Arrhythmia PEARLS may prove invaluable in evaluation and management of other cases.
- For clarity — I’ve labeled the first 2 tracings in this case (Figure-1):
|Figure-1: The first 2 ECGs in this case (See text).