ECG Review
Sinus Tach into PSVT?
By Ken Grauer, MD, Professor, Assistant Director, Family Practice Program, University of Florida Dr. Grauer reports no financial relationship to this field of study.
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Figure. Non-consecutive lead II rhythm strips |
Clinical Scenario: The two non-sequential lead II rhythm strips shown in the Figure were interpreted as showing "sinus tachycardia (top strip) with sudden development of PSVT" (lower strip). Comment?
Interpretation/Answer: The rhythm in the top tracing is rapid and regular at a rate of about 130/minute. This QRS complex is narrow, defining this as a supraventricular rhythm. On initial inspection, there appear to be upright P waves with a fixed PR interval preceding each QRS complex, suggesting that the rhythm is sinus tachycardia. However, an upright, pointed deflection is also regularly seen in the early portion of each T wave. Stepping back to better appreciate the pattern of baseline activity suggests a "sawtooth" configuration in which two upright peaks in the baseline occur at equally spaced intervals for each QRS complex. Thus, the rhythm in the top tracing is atrial flutter with 2:1 AV conduction (atrial rate 260/minute; ventricular rate = 130/minute).
In the lower tracing, sinus rhythm is initially seen. There follows several PACs (premature atrial contractions), a slight pause — and then the onset of a rapid supraventricular (narrow QRS) tachyarrhythmia without clearly defined atrial activity. Although at first glance this tachyarrhythmia appears to be regular, it is not. Instead the rhythm is atrial fibrillation. When the ventricular response to atrial fibrillation is very rapid (as seen here), it may look as if the rhythm is regular unless calipers are used to measure each R-R interval.
The two non-sequential lead II rhythm strips shown in the image were interpreted as showing "sinus tachycardia (top strip) with sudden development of PSVT" (lower strip).You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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