Hyperkalæmia

Report:

Broad-complex rhythm of uncertain origin, 50/min

Indeterminate axis

Intraventricular conduction defect

QRS 0.18”

Repolarisation changes suggestive of hyperkalæmia

Comment:

The patient’s potassium level was probably over 9.0 mEq/L; the first measured level was 8.8 mEq/L, taken after this recording was obtained.

There is, possibly, sino-ventricular conduction of sinus rhythm here: the rhythm strip shows a very shallow elevation of the isoelectric line approximately 0.28” before the QRS, consistent with (very) flat P waves. When definite P waves appear (144a), at a lower potassium level, they are still quite small and conducted with 1o AV block (PR 0.24”); with potassium normalised, they reach the height of P pulmonale (144b). Definitive diagnosis of sino-ventricular conduction (a bit of a zebra, anyway) would require observed gradual emergence of P waves with falling potassium levels; a sudden appearance suggests change from junctional to sinus rhythm at the same or similar rate.

The IVCD in hyperkalæmia typically resembles RBBB, with or without a “hemiblock”; sometimes a standard-looking fascicular block appears. At very high levels, the QRS prolongation is always diffuse and different from “normal” conduction delays.

The ST segment elevation in the anteroseptal leads is also typical of hyperkalæmia.

The changes shown here are an example of immediately life-threatening hyperkalæmia, requiring urgent (“emergent” in the USA) treatment.

144a. Emerging P waves

144b. Prominent P waves 145. A patient treated with IV adenosine for atrial flutter, instructed to cough during the funny-looking part of the strips. He complied, but complained it was unnecessary. Was he right or wrong?