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By Ken Grauer, MD
Figure. 12-lead ECG and accompanying rhythm strip recorded from an older man on multiple medications.
Clinical Scenario: The 12-lead ECG and accompanying rhythm strip shown in the Figure were obtained from an older man who presented with acute dyspnea from pneumonia. He was on multiple medications, and was in moderate-to-severe respiratory distress at the time this ECG was recorded. Is the rhythm Torsades de Pointes?
Interpretation/Answer: At first glance, the tracing in the lead II rhythm strip clearly resembles Torsades, as there appears to be an intermittently large amplitude sinusoidal pattern with alternating polarity. However, this is not what is happening. The clue to the true etiology of the rhythm lies with careful surveillance of all leads on the 12-lead ECG. This reveals an underlying regular supraventricular (narrow QRS complex) tachycardia that is best seen in leads III, V3, V4, and V5. The relatively small baseline undulations in these leads are clearly identified as artifact. Armed with this knowledge, one can prove artifact as the cause of baseline distortion in the simultaneously recorded rhythm strip at the bottom of the Figure by beat-to-beat comparison with the rhythm in leads III and V3. Doing so should make it apparent that the underlying narrow QRS rhythm continues without interruption throughout the lead II rhythm strip. This underlying rhythm is sinus tachycardia, with intermittent sinusoidal-appearing artifact produced by this patient’s respiratory distress.
Recognition of artifact is often a challenging endeavor. Perhaps the two most helpful clues toward facilitating recognition are: I) Look first at the patient for correlation with the clinical setting (ie, unresponsiveness consistent with malignant arrhythmia?—or "telltale activity" such as hand tremor, performance of CPR, seizure, or respiratory distress?); and II) Look carefully for an underlying rhythm, which if present continuously throughout the tracing despite distorting activity proves artifact as the cause.
Dr. Grauer, Professor, Assistant Director, Family Practice Residency Program, University of Florida, is Associate Editor of Internal Medicine Alert.