Third Degree AV Block 

3rd Degree AV Block


COMPLETE HEART BLOCK OR COMPLETE AV DISSOCIATION. IMPULSE IS COMPLETELY BLOCKED BETWEEN THE ATRIA AND THE VENTRICLES. USUALLY TAKES PLACE BETWEEN THE AV JUNCTION AND BUNDLE OF HIS. THE VENTRICLES MUST INITIATE THEIR OWN IMPULSES AND THE ATRIA AND VENTRICLES ARE FUNCTIONING INDEPENDENTLY! THE P-R INTERVALS ARE CONSTANTLY CHANGING IN LENGTH AND THE INTERVALS DO NOT BECOME PROGRESSIVELY LONGER AS THEY DO IN MOBITZ I. NO TRUE P-R INTERVAL OCCURS. P WAVES AND QRS COMPLEXES APPEAR AS WELL AS P-R INTERVAL THAT ARE CONSTANTLY CHANGING IN LENGTH. THE PRINTERVAL’S DO NOT BECOME PROGRESSIVELY LONGER. AND THERE IS NO RELATIONSHIP BETWEEN THE P WAVES AND QRS COMPLEXES. THERE IS NO TRUE PR INTERVAL AND THE QRS COMPLEXES ARE WIDE AND BIZZARE WITH A TIME FRAME OF >0.12 SECONDS. DEPOLARIZATION IS AT THE INHERENT RATE BUT THE P TO P AND R TO R INTERVALS ARE NOT EQUAL. ATRIAL RATE 60 TO 100 VENTRICULAR RATE 20 TO 40. THIS IS A LETHAL DYSRHYTHMIA. CAN LEAD TO ASYSTOLE 


Characteristics

Rate Atrial rate is greater than, and independent of ventricular rate.
Rhythm Atrial regular (P waves plot on time. Ventricular regular. NO relationship between the 2 P-Waves Normal in shape and size

PR Interval None. The Atria and Ventricles beat independent of each other. Thus, there is no true PR interval
QRS Duration Narrow or wide depending on the location of the escape pace maker and the conduction of the intraventricular conduction system.


Treatment

Monitor Diagnostic 12 lead 

Oxygen 15 LPM NR mask

IV 18g AC

Symptomatic Bradycardia 

Administer Meds

Atropine 0.5-1 SIVP over 1-2 min Repeat every 3-5 min (3.0mg max) 

Dopamine 5-10mcg/kg/min (Diluted Infusion only)

Epinephrine 2-10mcg/min (Diluted Infusion only)
Consider Transcutaneous Pacing


MEDS

Atropine 0.5-1 SIVP over 1-2 min Repeat every 3-5 min (3.0mg max )

Dopamine 5-10mcg/kg/min (Diluted Infusion only) 

Epinephrine 2-10mcg/min (Diluted Infusion only)

Narrow= Junctional Pacemaker. 

Wide= Ventricular Pacemaker


Noticeable by: 

P waves occur at normal rhythm and QRS occur at a normal rhythm but are independent of each other 

© Matt Dillard 2012