This rhythm strip was obtained from a man who was suffering an acute inferior wall M.I. There are ST elevation and hyperacute T waves. The rhythm is SINUS ARRHYTHMIA WITH SECOND-DEGREE AV BLOCK, TYPE II. There is also first-degree AV block.
There are more P waves than QRS complexes, with a 3:2 ratio. The atrial rate varies between 55 -68 beats per minute. The sinus rate speeds slightly after the dropped QRS in each group. The ventricular rate is about 40 bpm, with grouped beating. (Regularly irregular.)
The PR intervals are steady at 226 ms (slightly prolonged).
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One Characteristic to Clinch the Diagnosis
With a Mobitz II AV block, the PR interval that immediately precedes the non-conducted P wave and the PR interval that immediately follows it should be equal.
Jerry W. Jones MD FACEP FAAEM
https://www.medicusofhouston.com
Twitter: @jwjmd
Thank you!
Thanks, Dr. Jones.
Dawn Altman, Admin
The struggles of new students with heart blocks
I have been an instructor for a Basic Cardiac Monitoring class for 17 years. Mobitz I & II + 3rd degree, are where the students struggle the most. I focus on the P to QRS relationship, and tell them over and over to use the calipers to ascertain the Atrial and Ventricular rates.
I must say though, we don't provide any strips of Mobitz II that include Sinus Arrhythmia; that would throw them off completely.
Pete Hupp
Agree!
I agree. I think it is more difficult to teach beginning students, especially if they have very little A&P background. How to teach accurately without getting into the weeds??? And, they are bound to be confronted with rhythms that don't follow the "rules" they have learned. Teachers who teach more advanced students don't always know the struggle! :-).
Dawn Altman, Admin