AVNRT vs Junctional Tach??

[KimberlyShane]

Could someone please tell me how to differentiate between AVNRT and JT when interpreting ECG strips? I know in some leads, AVNRT will have the pseudo R and S waves, but is that it? Thanks in advance for any input!

[AJJKRN]

What the hell does AVNRT mean? Is JT junctional tachycardia? This may help many posters start the ball rolling...

(FWIW, we don't all use the same acronyms)

[EGspirit]

I think she means AV node retrograde tachycardia. I always thought there was an inverted P wave. I looked it up:

Atrioventricular re-entrant tachycardia. It's caused when an impulse from an ectopic foci in th atrium reaches the AV node. half the nerve fibers in the AV node are refractory, but half are not, and the ones that are not allow the impulse to pass to the ventricles, but the AV impulse then travels back through the now-not refractory fibers and contracts the atrium again. This cycle sets up the tachycardia, and it gives a P wave that is usually inverted and comes after the QRS complex, or may be hidden completely in the QRS complex. It comes after the QRS complex, because the impulse wasn't coming from the sinus node, so there is no ordinary p-wave, but the ventricles are fired by the AV node, but the RE-ENTRANT impulse gives an inverted p-wave as it contracts the atrium again, so the p wave is seen after the QRS complex.

In junctional tachycardia, the impulse comes from the AV node, thus the P-wave is inverted, but comes before the QRS complex--not always before, but that's how I would differentiate the two.

Both can be caused by digoxin toxicity.

Quite interesting actually.

[KimberlyShane]

Thanks for the reply! :) I know differentiating between the two rhythms is a fine line as junctional p waves aren't very reliable. I've only recently began studying more advanced ECG and had never heard of AVNRT until now. Every day I learn something new. :)

[EGspirit]

Thanks for the reply! :) I know differentiating between the two rhythms is a fine line as junctional p waves aren't very reliable. I've only recently began studying more advanced ECG and had never heard of AVNRT until now. Every day I learn something new. :)

Yes, me too. I learn something new each time I study it. And cardiology is my favorite subject. :)