Is this complete heart block?
Image 1 - ECG case
For seemingly complex rhythms, a ladder diagram is of value:
1. Look for P or "milk the P" (French - cherches le P)
The RED ARE OBVIOUS P'S AND THE GREEN ARE NOT SO OBVIOUS. Mark in the A tier (atrium)
Image 2 - P waves marked
2. Look for the QRS. Mark in the V tier (ventricle)
Image 3 (A and V tier)
This is easy since we just drop the line for sinus beats (A TIER) and QRS (V TIER)
3. Connect the AV tier
Image 4- (connecting the dots)
This is more interesting because we have to identify which impulse to connect.
EXAMINE THE QRS MORPHOLOGY/SHAPE AND THE R TO R INTERVAL.
If you do that it will be a bit easier.
QRS 1,2, 4 and 5 are wide.
QRS 3, 6 and 7 are narrow.
HOWEVER, QRS #7 is DIFFERENT FROM QRS 3 AND 6.
The RR intervals of R1R2 AND R4R5 ARE THE SAME. Thus, we can say they must be from the same source. They are wide so they are ventricular in origin (asterisk at V tier).
QRS 3 and 6 looked narrow and the P is in the conductible distance. Second, there is shortening of the RR interval compared to the preceding RR interval (R1R2 and R4R5).
"The way to recognize captured beats is not by finding an appropriate PR interval, but rather by detecting a shortening of the RR interval" - Dr. H Marriott.
So, R3 and R6 are captured beats (marked C).
QRS #7 looked different than R3 and R6. It looked narorw but the P seemed to be so close. So, this isfrom the junction.
Finally, we can say this is SR (~83 bpm) with long PRI, Second degree ADVANCE heart block (or high degree AV block). Complete heart block was rule-out because of the presence of captured beats.