Using a copy of [SPICE] a free circuit simulation application, I have created several sine wave sources and summed them together. Seen here, the waves combine into a square wave with it looking ...

You must treat the hyperkalemia first. Absence of the P waves and eventually a “sine wave” pattern, as seen below, which is frequently a fatal rhythm CLINICAL PEARL: Giving intravenous calcium ...

a "sine wave" pattern (see below), which is frequently a fatal rhythm. Giving IV calcium is "cardioprotective" in the setting of hyperkalemia. Frequently, instant reversal of all hyperkalemic ECG ...