Cardiac Telemetry Practice Exam 2026 – Complete Preparation Guide

Severe hyperkalemia disrupts cardiac conduction enough to produce a sine-wave pattern on telemetry. High extracellular potassium reduces the resting membrane potential, partial depolarization inactivates sodium channels, and slows impulse propagation. This causes the QRS to widen and the T waves to merge with the QRS, yielding the characteristic sine-wave appearance. This pattern signals life-threatening potassium excess and imminent risk of dangerous arrhythmias if not treated promptly.

Other electrolyte patterns don’t produce this sine-wave. Hypokalemia tends to cause flat or inverted T waves with U waves; hypercalcemia shortens the QT interval; hypomagnesemia is a setup for QT prolongation and torsades de pointes rather than a sine wave.