The spiked helmet sign (SHS) is a rare electrocardiographic marker associated with an increased risk of lethal ventricular tachyarrhythmias and sudden cardiac death. To our knowledge, this is the first study aimed at reviewing recent research progress on this electrocardiogram (ECG) pattern to summarize its electrophysiological mechanisms, epidemiological features, clinical characteristics, and clinical significance. SHS formation is attributed to sympathetic hyperactivity, which mediates increased dispersion of ventricular repolarization, leading to marked QT prolongation and macroscopic T-wave alternans. This pattern can be observed in critically ill patients with cardiac or noncardiac conditions. In particular, immediate identification of this ECG abnormality is crucial in recognizing and treating noncardiac conditions in older male patients.