The correct diagnosis is hyperkalemia (Figure 2).
The QRS complexes are regular at a rate of 110 beats/min. There are no P waves noted. The most important finding is a diffusely widened QRS complex (⊔) with a duration of 0.28 sec. In addition, the T waves are tall and symmetric (⊥). Hence, the underlying problem is hyperkalemia.
The only condition that causes the QRS complex to be ≥ 0.24 sec is hyperkalemia, regardless of the rhythm or the presence of an underlying intraventricular conduction delay; the hyperacute T waves are also consistent with hyperkalemia. The etiology of the rhythm is uncertain.
The QRS complexes have a normal morphology but are diffusely widened; they are probably supraventricular. P waves are not seen, suggesting that the rhythm is junctional. However, the absence of P waves in hyperkalemia is due to atrial asystole; ie, the atria do not respond to impulses generated by the sinus node or an atrial focus. This often occurs before there is marked QRS widening. If there is a sinus rhythm this is termed sinoventricular rhythm. Ultimately, the ventricles will not respond to electrical stimuli (ie, asystole). With treatment of hyperkalemia, the QRS complex narrows and P waves will become obvious if there is an underlying sinus or atrial rhythm.
Philip Podrid, MD, is an electrophysiologist, a professor of medicine and pharmacology at Boston University School of Medicine, and a lecturer in medicine at Harvard Medical School. Although retired from clinical practice, he continues to teach clinical cardiology and especially ECGs to medical students, house staff, and cardiology fellows at many major teaching hospitals in Massachusetts. In his limited free time he enjoys photography, music, and reading.
You can follow Dr Podrid on Twitter @PPodrid
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Cite this: ECG Challenge: Hypotension in a Cardiomyopathy Patient - Medscape - Mar 23, 2021.