Arterial pulsation artifact mimicking spiked helmet sign: a case report.

This case report presents an 86-year-old female patient admitted for the surgical evaluation of a mediastinal cystic mass. Initial electrocardiogram (ECG) showed ST-segment and T-wave changes resembling the spiked helmet sign. Considering the patient's stable vital signs and the absence of ST-segment changes in lead I, the possibility of ECG interference was suspected. Further investigation and repeated ECG, with adjustments to electrode placement away from the left lower limb artery, confirmed that the changes were due to arterial pulsation interference rather than a true cardiac abnormality. This case highlights the critical need to differentiate true cardiac ischemia from artifact-mediated ECG changes, particularly in hemodynamically stable patients.