18 year old female with palpitations and fever

What is the EKG intepretation?

A. Atrial flutter
No. Atrial flutter with 2:1 conduction with a ventricular rate around 130 may be suspected in this EKG. However, the waves before the QRS complexes are more likely P waves as (a) there is no regular flutter pattern (b) there is only one wave per QRS complex and (c) the waves are upright in lead II. Importantly there is no impression of a saw-toothed baseline in the inferior leads as it is seen in atrial flutter.
B. Sinus tachycardia
Yes! The regular ventricular rhythm, the upright P waves preceding the QRS complexes in II, III and aVF and the rate below the usual area for other supraventricular tachycardias collectively indicate sinus tachycardia. Also the patient presents with fever, which may explain the sinus tachycardia. However other supraventricular arrhythmias are relevant to consider. In particular if the patient takes any antiarrhythmic drugs as these may put the rate of another tachycardia below its usual range. If in doubt about the diagnosis check if the rate varies or is “fixed” at a certain level over time. If the rate varies over time it suggests sinus tachycardia. Also check earlier electrocardiograms to get an impression of P wave morphology in normal sinus rhythm. Finally consider to perform an esophageal recording or to do vagal maneuvers to de-mask eventual flutter waves or to terminate an AVNRT. Also adenosine may de-mask flutter waves or terminate an AVNRT.
C. Atrial fibrillation
No. Atrial fibrillation is seen as an irregular ventricular rhythm and an oscillating baseline with absent P waves. In this EKG the ventricular rhythm is regular and the QRS complexes are preceded by P waves.
D. AV nodal re-entry tachycardia (AVNRT)
No. Though the rhythm in AVNRT is also regular, the rate is usually faster: 150-250 beats per minute. Also in AVNRT the P waves are negative in inferior leads (if seen) as they are retrogradely conducted from the AV node.
E. Wolff-Parkinson-White (WPW) tachycardia
No. In WPW tachycardias the rate is usually faster. If in doubt remember to look for delta waves in an EKG in normal sinus rhythm (though the WPW syndrome may be concealed).

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