By Ken Grauer, MD
Professor Emeritus in Family Medicine, College of Medicine, University of Florida
Dr. Grauer reports no financial relationships relevant to this field of study.
Did this patient develop ventricular fibrillation (Vfib) while the ECG in the figure was recorded?
Although the appearance in several leads of this tracing may suggest momentary development of Vfib, this is not what is happening. Instead, a regular rhythm (presumably sinus) continues throughout the recording.
The presence of artifact is extremely common. Potential sources of artifact include tremor, shivering, brief seizure activity, or other body movement; loose or faulty lead connection; external devices that may produce various types of interference; and application of a monitoring lead in close contact with a pulsating artery, among others. Extreme clinical conditions with acutely ill patients may lead to unavoidable artifact. That said, most of the time, interpretation of the ECG still will be possible, despite a less-than-perfect recording. However, when artifact becomes as pronounced as it is in this figure, interpretation of the ECG may become extremely challenging.
The best way to prove artifact is to recognize persistence of an underlying spontaneous rhythm that is unaffected by any erratic or suspicious deflections that are seen. Therefore, despite close resemblance to Vfib in leads III, aVL, and aVF of this ECG, an underlying regular supraventricular (that is, narrow QRS) rhythm at a rate just under 100/minute still can be seen in virtually all other leads on the tracing. Proof that the high-amplitude chaotic deflections seen in leads III, aVL, and aVF constitute artifact is forthcoming from inspection of simultaneously obtained leads. For example, dropping a vertical line from the narrow QRS complexes that we can recognize (amid the artifact) in lead aVR (directly above the small black circles) shows that despite baseline artifact, this vertical line would fall precisely on tiny QRS complexes in leads aVL and aVF. This proves the erratic high-amplitude deflections seen in leads aVL and aVF must be artifact because the underlying regular rhythm continues at the same rate throughout the entire recording in all 12 leads. Note that while we suspect the mechanism of the underlying narrow rhythm in this ECG is sinus (upright P waves are suggested in lead II), the amount of artifact prevents clear distinction between a sinus vs. junctional rhythm. But we can say with certainty that a regular supraventricular rhythm is present.