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Atrial tachycardia

Supraventricular Tachycardia With Wenckebach Conduction

Wed, 03/16/2016 - 22:55 -- Dawn

This ECG was obtained from a patient in a walk-in health clinic.  We do not have any other information on the patient.  We thank Joe Kelly for donating this interesting ECG to the GURU. 

IRREGULAR RHYTHM    If you march out the P waves, you will see that they are regular, at a rate of approximately 130 bpm.  But the QRS complexes are not regular, and there are fewer QRS complexes than P waves.  

WENCKEBACH CONDUCTION   Looking closely at the PR intervals, you will notice that they progressively prolong.  This “pushes” the QRS complexes progressively toward the right.  Eventually, the T wave – and the refractory period – will land on the next P wave.  That P wave will be unable to conduct to the wave, and no T wave of course, so the next P wave will conduct with a shorter PR interval.

We are including a short rhythm strip from this patient, with conduction marked with a laddergram. 

Atrial Flutter With 2:1 Conduction

Fri, 10/04/2013 - 23:07 -- Dawn

Unfortunately, we have no clinical information on this patient, not even age or gender, as the ECG machine defaults to "Age 60".  The rhythm is a supraventricular tachycardia at a rate of about 260/min. with 2:1 conduction, resulting in a heart rate of about 130 / minute.  Some would call this atrial tachycardia, and some atrial flutter.  Since the reentrant pathways involved in the two rhythms are different, it is probable that an electrophysiologist could determine the exact location of the pathway in the EP lab.  Without benefit of this test, we use our best guess.  We will leave it to our more advanced Gurus to debate the origins of this rhythm.

The fast P waves are best observed in the limb leads, with one P wave occuring in the QRS complex.  If you ignore the QRS complexes for a moment, you can draw an unbroken line through them, uncovering the flutter waves.  SVTs with 2:1 conduction can easily be mistaken for sinus tachycardia.  Always suspect and look for atrial flutter when the heart rate is around 150 / minute.  A 12-lead is a big help, as flutter waves show up better in some leads than in others.  Another way to uncover atrial flutter is to slow the rate with vagal maneuvers or medication to decrease the conduction ratio, and observe several flutter waves in a row without QRS complexes.

Of even more concern to this patient may be the ST elevations - slight but noticeable - in Leads V2 - V4, and possibly I and aVL.  The J points (the beginning point of the ST segment) can be obscurred by the P wave lying beneath the QRS, and it may be difficult to judge ST elevations.

We expect this ECG to elicit many opinions - possibly different from ours.  Please add your comments below.  We will enjoy the discussion.

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