Second Degree Heart Block-Type 1
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.
Don’t forget the helpful phrase we all learned in nursing school: “Longer, longer, longer, DROP, then we have a Wenckebach”.
Studying this weekend to recertify for the first time. Love your site. Thank you for all your hard work to make this an enlightening experience as well as reducing my stress level.
I have already recommended your site and will continue to do so.
Thank you Brenda ! I personally love mnemonics. They free me up from that momentary ” pause” ( no pun intended) in the thought process that usually leads to a complete block ( again, no pun intended) in my review. If you have one for the Glascow Coma Scale that would be fantastic!
This makes total sense..It gave me a clear understanding of my strips..thanks so much
This so ROCKS!!!! I can actually make sense of these strips! Big ThanK YOU
(1) The SA Node is the hearts primary pacemaker. (2) The SA Node generates an impulse which propagates across/thru the atria and to the A/V Node in attempt to cause the stimulation to the ventricles (via the Bundle of His and then the Purkinje Fibers. (3) The A/V Nodes primary function is to figuratively act as a gatekeeper as if there was a little man standing there with his hand on the gate allowing signals to pass thru in such a way that optimizes the hearts contracting as a smooth functioning unit (this ensures the greatest movement of blood thru the heart chambers and sets the stage for the greatest EF from the left ventiricle). (4) In the case of heart block the gatekeeper is (for some physiologic reason) restricting the passage of necessary stimulations from above the A/V Node (in the best case scenario the SA Node) from passing thru his gate so that they can transfer their stimulus to the ventricles. (5) If the QRS’s are narrow the block is in the A/V Node (internodal), if the are QRS’s wide (aberrant conduction) then the block is below the A/V Node and somewhere in the Bundle of His or Bundle branches which is much more serious and could ultimately lead to 3rd degree block and will typically create hemodynamic issues for the patient. The MD will most likely end up installing an artificial pacemaker in the patient to safegaurd the possibility of more serious heart failure.