#CARDIOLOGY - 1. AV BLOCKS

Hey friends,
How are you doing??

Today i want to tell you about ATRIOVENTRICULAR BLOCKS.

WHAT IS ATRIOVENTRICULAR BLOCK??

First of all, we have to know about the conducting system to understand the term AV BLOCK.

CONDUCTING SYSTEM OF HEART

All of us know heart beats in a rythmic fashion. But how its happeninng and why not all the parts of heart beat once? The structure of conducting system willl let you know about this.

Image source:wikimedia commons

The conducting system of heart contains the following parts:

1. SA node
2. AV node
3. Bundle. Of His
4. Branches of Bundle. Of His and
5. Purkinje fibers.

SA node: it contain special atrial cells that depolarise on its own. And influenced by circulating catecholamines & ANS.

Annulus fibrosus : its the conduction barrier that blocks the direct conduction from atrium to the ventricles.

AV node: It lies in the right atrium in the midline and pierces annulus fibrosus anteriorly.

Image source: Doomsteaddiner.net

AV blocks

These are of 3 types based on the severity of the block:

1ST DEGREE
This is charecterised by prolong PR interval of >0.2 sec and it is mostly asymptomatic.
Here is a ECG strip of this block, notice the PR interval (arrow).

Image source:openpediatrics.

2ND DEGREE
There are still two types in this 2nd degree AV block. They are

1. Mobitz type 1 or WENKEBACHS phenomenon.
   Its charecterised by *progressive prolongation of PR interval culminating in a dropped beat.
   Its a problem in the AV node itself.
   See the progressive prolongation in the pic.
   
   Image source: openpediatrics

2. Mobitz type 2:
   Here there is constant PR interval but there is a risk of asystole. Its a disease of Bundle of His or purkinje fibres.
   

3RD DEGREE:
In this atria and ventricles beat separately. Its called AV dissociation.
Ventricular activity is by escape rhythm.
The pulse will be slow and regular at a rate of 25-50/minute.
Here is an ECG strip of 3rd degree block , see that the rate of atrial depolarisation is more than the ventricular.
()
Image source:openpediatrics.

MANAGEMENT

1. A simple 1st degree doesnt need any treatment in most of the cases.

2. AV block complicating MI
   In many cases the AV block is due to MI(myocardial ischaemia and treating the MI will spontaneously cure the block.
   And if there is an extensive damage to the cardiac tissue and the conducting system due to MI there might be the need of a PACEMAKER.

3. In chronic AV block, the patients need a PERMANENT PACEMAKER as there is a high risk of sudden asystole and death.

Reference: HARRISON’S principles of internal medicine -19th edition.

I thank @Air-clinic, @nairadaddy & @thelovejunkie for their support.

I hope you all like my post and kindly comment me if there are any mistakes and please upvote and resteem.This might help others.

Thank you.