By Ken Grauer, MD
Professor Emeritus Family Medicine, College of Medicine, University of Florida
Dr. Grauer is the sole proprietor of KG-EKG Press, and publisher of an ECG pocket brain book.
The lead II rhythm strip in the figure below was obtained from a middle-aged man with new-onset palpitations. He is hemodynamically stable.
- What is this rhythm most likely to be?
- What might be done diagnostically to confirm your suspicion?
Interpretation: Since the patient is hemodynamically stable, there is time to systematically assess the rhythm. We favor use of the, “Ps, Qs, 3R” approach to remind of us of the five key parameters to assess. It does not matter in what sequence we address these parameters. What counts is that we include in our approach a search for P waves (presence of atrial activity), QRS width, and the 3 Rs (rate of the rhythm, regularity, and if atrial activity is present — whether such atrial activity is related to neighboring QRS complexes).
Normal sinus P waves are not present because there is no upright P wave in lead II. However, atrial activity does appear to be present, as we see one (if not two) negative deflections within each R-R interval. One of these negative deflections occurs just before the QRS complex. The other appears just after the QRS within the middle of the ST segment. If these negative deflections do represent atrial activity, then there is a consistent relationship between each QRS complex and the negative deflection that precedes it.
The QRS complex looks to be narrow. That said, it is impossible to be certain of this from inspection of this single monitoring lead. A 12-lead ECG obtained during tachycardia confirmed that the QRS complex was indeed narrow and that the first negative deflection in each R-R interval was not part of the QRS complex). The ventricular rhythm is regular. Each R-R interval is just over two large boxes in duration, so the ventricular rate is just over 150/min.
Impression: Putting together the above findings, we have described a regular supraventricular tachycardia (SVT). The three most common causes of a regular SVT rhythm are: 1) sinus tachycardia (in which sinus P waves sometimes may be hiding within the previous ST segment), 2) paroxysmal supraventricular tachycardia (PSVT), and 3) atrial flutter.
We have already ruled out sinus tachycardia because there are no upright P waves in lead II. We suspect this rhythm is atrial flutter because: 1) Atrial flutter is by far the most commonly overlooked SVT rhythm, since flutter waves are often not overly evident when the ventricular rate is fast, 2) The ventricular rate is very close to 150/min, which is consistent with the most common ventricular rate for untreated atrial flutter, and 3) The negative deflections we describe above are perfectly spaced at a rate of approximately 300/min (precisely twice the ventricular rate.
Application of a vagal maneuver temporarily reduced the ventricular response. This allowed diagnostic atrial activity at a regular rate of 300/min to be seen. The only rhythm that does this is atrial flutter.
NOTE: For a complete illustrated discussion of this tracing, fast forward to the 1:22 point in my ECG Video #12 at the following link: https://youtu.be/PnHIzDh4BZ8?t=1m22s (The case is reviewed over the next 11 minutes).
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