By Ken Grauer, MD
Clinical Scenario: The tracing in the Figure said, "V Tach on the monitor" (salvo of beats marked "V" on the rhythm strip). The computerized interpretation also cautioned about "deep anterior T wave inversion suggestive of ischemia." Would you agree?
Interpretation: As always, the best way to approach the interpretation of any 12-lead tracing is to begin by assessing the rhythm on a single lead rhythm strip. A lead II rhythm strip is seen at the bottom of the 12-lead ECG shown in the Figure. This rhythm strip is marked by significant baseline wander with intermittent large erratic deflections (including three peaked upright deflections marked "V"). Despite the worrisome appearance of these three deflections, this is not ventricular tachycardia.
Artifact is a common phenomenon seen on the ECGs of acutely ill patients, in whom many potential sources of distortion-producing movement may exist (patient unable to remain still because of pain or dyspnea, performance of blood draws, or other invasive procedures on the patient).
Distinction between real ECG findings and artifactual distortion may be difficult unless one remains open to the latter as a possibility. Definitive diagnosis of an artifactual rhythm can best be made by the finding of an undisturbed underlying rhythm. This is seen in the lead II rhythm strip of this Figure, which begins and ends with several definite sinus beats. Despite baseline wander and the large V-marked deflections, the underlying sinus conducted QRS complex continues at a regular rate throughout the entire rhythm strip. A look at simultaneously recorded leads V1, V2, and V3 reveals marked inconsistency in the shape of T wave inversion in these leads, raising the question of whether significant T wave inversion really is present at all. Only by repeating the ECG (and hopefully minimizing potential sources of artifact) will the issue of T wave inversion be resolved.