ECG - Blocks

1. Normal Sinus

1.1. From SA Node

1.2. P wave before QRS

1.3. PR - 0.12 - 0.20

1.4. QRS - same shape and size - < 0.12

1.5. Rhythm = P-P & R-R; Regualr

1.6. Rate = 60 - 100 bpm

2. 1st Degree AV Block

2.1. From the Atria

2.1.1. Delay between the atria and bundle of his

2.2. PR > 0.20

3. 2nd Degree AV Block - Mobitz I (Wenkebach)

3.1. Block at AV junction

3.1.1. progressive

3.2. PR becomes progressively longer until QRS is dropped

3.3. P - P = regular

3.4. R - R = irregular

4. Mobitz II

4.1. Block at AV junction

4.1.1. intermittent block

4.2. More P waves then QRS complexes

4.3. Usually a pattern

4.3.1. 2:1, 3:1, 4:1

5. 3rd Degree AV Block

5.1. Block between atria and ventricles

5.2. P waves: no relationship to QRS

5.3. No true PR interval

5.4. QRS: same shape and size

5.4.1. Usually wide, bizarre and > 0.12

5.5. Ventricular rate usually 20 - 40

5.6. Atrial rate usually 60 - 100

6. Bundle Branch Block

6.1. Block in bundle branch (left, right or both)

6.2. QRS usually same size and shape, notched appearance

6.2.1. Usually > 0.12

6.3. Looks like PVC except:

6.3.1. Has P wave

6.3.2. t wave going in same direction

6.3.3. Initiated by SA node, not ventricle