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By Ken Grauer, MD, Professor, Department of Community Health and Family Medicine, University of Florida. Dr. Grauer is the sole proprietor of KG-EKG Press, and publisher of an ECG pocket brain book.
Scenario: The simultaneously obtained lead II and lead V1 rhythm strip seen above was interpreted as showing atrial fibrillation with a rapid ventricular response. Do you agree?
Interpretation: The rhythm in the tracing is rapid, irregularly irregular, and clearly supraventricular. Other than a few low-amplitude undulations in the baseline, the lack of atrial activity in lead II suggests atrial fibrillation as the underlying rhythm. However, nearly persistent and much larger amplitude baseline deflections in simultaneously recorded lead V1 suggest another possibility. At first glance, one might interpret the rhythm in lead V1 as atrial flutter with a variable ventricular response, especially during the latter part of the tracing. Baseline undulations are also seen during the initial portion of the tracing, although of lower amplitude and with much greater variation in morphology. Throughout this lead V1 rhythm strip, there is marked variation of QRS morphology, as well as baseline wander. Inconsistency of the pattern of baseline undulation that occurs in association with this amount of variation in QRS morphology in lead V1 suggests either excessive patient movement at the time the tracing was recorded and/or other cause of artifact. The pattern seen in lead V1 might also be interpreted as atrial "fib-flutter" in recognition of the almost sawtooth appearance of atrial activity during the latter portion of the tracing. Atrial "fib-flutter" is a descriptive term used by some to portray the electrocardiographic appearance seen when undulations in the baseline alternate between characteristics of both atrial flutter and fibrillation. The important practical point of this descriptive entity is that the arrhythmia clinically behaves as atrial fibrillation in regard to its response to medical and electrical therapy. How much the baseline undulations seen on this rhythm strip are due to artifact vs the underlying arrhythmia is difficult to tell.