Second-Degree Heart Block (Type 1)
Also called Mobitz 1 or Wenckebach is a disease of the electrical conduction system of the heart in which the PR interval has progressive prolongation until finally the atrial impulse is completely blocked and does not produce a QRS electrical impulse.
Once the p-wave is blocked and no QRS is generated, the cycle begins again with the prolongation of the PR interval.
One of the main identifying characteristics of second degree heart block type 1 is that the atrial rhythm will be regular.
In the above image, notice that the p-waves are regular, the PR-interval progressively gets longer until a QRS is dropped and only the p-wave is present.
Although second degree heart block type-1 is not clinically significant for ACLS, recognition of the major AV blocks is important because treatment decisions are based on the type of block present.
Below is a short video which will help you quickly identify second-degree AV block type 1 on a monitor. Please allow several seconds for the video to load.