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By Ken Grauer, MD
Clinical Scenario: The ECG shown in the figure was obtained from a patient with an acute exacerbation of long-standing pulmonary disease. In follow-up to last month’s ECG review (Emergency Medicine Alert 2001;9:5), is the tracing in the figure another example of atrial flutter, with the arrhythmia in this case being most evident in leads I and aVL?
Interpretation: Initial inspection of leads I and aVL suggests that the rhythm in the figure might be atrial flutter (with a flutter rate for atrial activity of just under 300/minute). Inspection of QRS morphology in other leads, however, suggests that this is not the case. The key to interpretation of this rhythm lies with remembering that the ECG in the figure is a simultaneous three-channel recording. Thus, leads I, II, and III are all recorded during the same period of time (and point X in leads II and III is recorded at the identical instant in time). Whereas superficial inspection of lead I might suggest the possibility of atrial flutter—a very different impression is suggested from review of lead II. That is, the rhythm in lead II appears to be sinus, as determined by the presence of an upright P wave that precedes each QRS complex in this lead and seems to be conducting. The fine undulations that alter the baseline of lead II look to be artifactual. Inspection of the ECG appearance in the third simultaneously recorded lead in this initial lead grouping (lead III) reveals an especially erratic and irregular spiky pattern that is highly characteristic of the presence of artifact.
The key to making a positive diagnosis of artifact lies with being able to detect the underlying normal cardiac rhythm that continues throughout—not affected in the least by artifact activity (as seems to occur here in lead II, and more subtly in lead III). Although identifying the underlying cardiac rhythm amidst a background abundant in artifact is often a task much easier said than done—one can follow regular QRS activity in lead III of this tracing despite the distracting artifactual distortion by beginning at point X, and walking out with calipers (at a regularly occurring R-R interval) the QRS complexes that occur throughout the rest of the tracing. Clinically, the ECG in this figure should be repeated in the hope of improving recording quality minimizing artifactual distortion.