Second degree AV block: Mobitz and Wenckebach

The second degree AV block is like a slowing down of traffic that sometimes gets blocked by police and no signal can get through sometimes. We can describe the rhythm as an intermittent block that sometimes gets blocked in the AV node. There are 2 types, type 1 (Wenckebach or Mobitz type 1) and type 2 (Mobitz type 2). The names given to the rhythm are the doctors that first noted the rhythm and described it in a medical journal so for simplicity we’ll note it as either a type 1 or type 2.

2nd degree AV block Type 1 is a progressive block which means the electrical conduction gets blocked at the AV node. So you will note the longer distance between the P wave and QRS complex it will get longer and longer and finally the QRS complex no longer follows the P wave. The sequence then starts over again with a normal P wave and interval and resulting in a dropped QRS complex. The rhythm is irregular and that is usually the only symptom you can have with this. Of course every one is different and some people can sometimes have different symptoms but that is usually only 10% of the cases, usually there are no symptoms except for the feeling of the irregular pulse.

Second degree AV block Type 2 is an intermittent blockage and differs only slightly from type 1. The difference lies in when the intermittent block occurs. The P wave interval is constant and from time to time there is a P wave and no QRS complex and the pattern repeats. So the rhythm is then felt the same as type 1 irregular usually having no other symptoms. Type 2 AV block is a transitional rhythm that is chronic (developed over time) or again be caused by drugs and medications. Usually no treatment is needed except just watch and change medications as needed.

They do not come over night they have been developing for some time. Again some drugs and medications can cause 2nd degree blocks and if you see your family doctor on a regular basis you can usually catch this with an ECG. So what do you do if you have an irregular rhythm, go to your family doctor if no symptoms, but if you feel dizzy, lightheaded or have been passing out go to the emergency room.

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