Hyperkalemia

The Shrinking Battery in Your Heart's Wall

Imagine your heart muscle cells are tiny batteries with a negative terminal inside and positive terminal outside. Normally, the voltage difference is huge — like comparing a charged phone battery (inside at –90V) to the air around it (at 0V). This 90-volt gap is what lets the battery fire: when you flip the switch, electrons rush across and power the heartbeat. But high potassium (hyperkalemia) is like slowly leaking potassium (the positive charge carrier) into the space around the battery, making the outside less positive and the inside less negative. The gap shrinks to maybe 20 volts instead of 90. Now when you flip the switch, the flow is sluggish and unreliable — sometimes the current gets stuck halfway, other times it misfires. Keep adding potassium, and the gap becomes 10 volts, then 5 volts. Finally, there's almost no difference between inside and outside, and the battery won't fire at all — your heart stops.