Electrocardiographic (ECG) artifacts—waveforms mimicking cardiac pathology despite extracardiac origins—present considerable diagnostic challenges in acute cardiovascular settings. Although ST-T changes may indicate true pathological conditions such as acute coronary syndrome, hypertrophic cardiomyopathy, pulmonary embolism, or myocarditis[8-10], technical artifacts stemming from non-ischemic factors can closely simulate these abnormalities, potentially leading to misdiagnosis and unnecessary interventions[6-7]. This case highlights the capacity of arterial pulsation to produce deceptive ECG changes and, importantly, delineates a previously unreported pattern of mid-portion T-wave inversion in precordial leads, which may aid in artifact recognition.
3.1 Origins and Localization of Electrocardiographic Artifacts
The accurate identification of ECG artifacts begins with recognizing their sources, which are broadly classified as technical, physiological, or environmental [1-5]. Our case focuses on a physiological source: arterial pulsation artifact. Such artifacts frequently obey the "single-limb lead exemption principle" [3,6-7], which is derived from the Einthoven triangle and Wilson Central Terminal (WCT) theory. This principle provides a vital diagnostic key:
A right arm artifact will spare lead III.
A left arm artifact will spare lead II.
A left leg artifact will spare lead I.
Furthermore, interference from a limb electrode does not remain isolated; it can disseminate to the precordial leads because the WCT itself becomes contaminated and serves as the reference for all chest leads (V1-V6) [6].
Applying this framework to our case, the complete sparing of lead II was an pivotal observation. It definitively pointed to the left arm as the source of the artifact, thereby correcting our initial suspicion of the right radial artery. This demonstrates that a systematic approach—first analyzing the ECG for a spared lead to localize the source, followed by physical verification of the electrode—is fundamental to unmasking pulsation artifacts.
3.2 Mid-Portion T-Wave Inversion in Precordial Leads: A Novel Artifactual Pattern
The most striking feature was a previously unreported pattern of repolarization artifact: isolated mid-portion T-wave inversions across leads V2–V6. Its signature characteristics—preserved initial T-wave morphology, a shallow focal mid-T notch (<1 mm), and immediate normalization after technical correction—are pivotal for diagnosis. The key distinction from pathological T-wave inversions (e.g., the symmetric depth of Wellns' or the asymmetric breadth of LVH) lies in its dynamic reversibility and precise spatiotemporal specificity.
Mechanistically, we posit that pulsation-induced currents from a limb electrode are integrated into the Wilson Central Terminal (WCT). From the WCT, this interference is broadcast to all precordial leads. The reason it manifests solely in the mid-portion of the T-wave is that this segment corresponds to the peak of ventricular repolarization (action potential phase 3). This is a period of well-established electrical vulnerability [11], where the myocardium is most susceptible to extrinsic electrical noise, thus explaining the highly selective nature of this artifact.
3.3 Clinical Implications and a Proposed Diagnostic Framework
This case provides three key clinical insights:
First, anatomical precision in electrode placement is essential, as minor misplacement near arterial pulsation sites can generate substantial artifacts.
Second, dynamic testing through electrode repositioning is highly suggestive of an artifact: complete normalization of ECG changes after adjustment strongly argues against acute ischemia.
Third, a composite biomarker significantly improves specificity: the coexistence of limb-lead ST-T changes following the exemption principle along with precordial mid-T-wave inversion provides a highly discriminative signature for pulsation artifacts.
Based on these insights, we propose the following structured diagnostic approach for similar scenarios:
1. Perform lead-specific analysis to identify any spared limb lead and localize the potential artifact source;
2. Physically inspect electrode positions, paying particular attention to proximity to arterial pulsation sites;
3. Repeat ECG after systematic electrode repositioning to determine the reversibility of observed abnormalities;
4. If abnormalities persist, proceed with further ischemic evaluation based on clinical presentation and biomarker results.
Previous work by Rudic et al. [12] demonstrated that repolarization dynamics can differentiate artifacts from true pathology with high specificity (>90%). The combined signature described here—exemption-consistent limb lead changes plus precordial mid-T inversion—warrants further investigation to validate its discriminative capacity and potential to reduce unnecessary invasive procedures in clinical practice.