Saturday, December 24, 2016

ECG Blog #139 (Atrial Flutter – AV Block – Artifact – Sinus Rhythm)

The rhythm in Figure-1 was diagnosed as AFlutter (Atrial Flutter) with 4:1 AV conduction. Do you agree?
  • What could be done to confirm your answer?
Figure-1: Lead II rhythm strip. Is this AFlutter? NOTE — Enlarge by clicking on the Figure.
Interpretation: As emphasized in ECG Blog #137 — the most common ventricular response to untreated atrial flutter is with 2:1 AV conduction. But the next most common ventricular response is with 4:1 AV conduction. At first glance, the rhythm in Figure-1 appears to be atrial flutter with this latter conduction ratio. However, close inspection reveals this is not the case!
  • Use of calipers demonstrates that the small upright deflections on the baseline between QRS complexes are definitely not regular. This makes it extremely unlikely that these deflections represent flutter activity, since flutter waves (by definition) should be extremely regular.
  • There is also a changing relationship between these small vertical deflections (that are seen throughout the baseline on this rhythm strip) — and neighboring QRS complexes. In contrast, with atrial flutter — there is usually a constant relationship between atrial deflections and neighboring QRS complexes. This is because with the exception of the variable conduction variant of flutter — there will usually be a readily identifiable repetitive pattern of atrial activity with respect to each QRS complex that results in a predictable conduction ratio.
  • Finally, if one steps back a bit from this tracing — underlying upright (sinus) P waves can be seen to precede each QRS complex with a fixed (and normal) PR interval (red arrows in Figure-2). The fact that these sinus P waves are unaffected by the smaller, irregularly occurring upright deflections proves that these smaller pointed deflections are the result of artifact.
Figure-2: We have labeled Figure-1 by adding red arrows to highlight underlying regularly-occurring sinus P waves (See text).
Comment: The best way to prove artifact — is to go to the bedside to observe the patient as the ECG is being recorded. Tapping, scratching, coughing, shaking, shivering, seizing and tremor are but a few of the common causes of artifactual arrhythmias. The patient in this case had Parkinson’s disease, which characteristically produces a tremor at a frequency that approximates the rate of atrial flutter. Bottom Line: It is easy to be fooled by artifact. It is well to develop a healthy respect for the gamut of “real appearing” arrhythmias that artifact distortion may produce.
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