AV Blocks (DM)

Heart Blocks Rhythms

The sinoatrial (SA) node generates impulses, but they are blocked or delayed in an area of the hearts electrical conduction system

most usual form of heart block

First-Degree AV Block

What is happening in First-Degree Block

excessive conduction delay in the AV node

Impulse conduction between the atria and the bundle of His is delayed at the level of the AV node

What heart block is not technically a dysryhtmia

First Degree Heart Block

Causes of First Degree AV Block

Young Athletes

Medications (BBs, CCBs, digoxin)

What is the hallmark of First Degree Block

Prolonged PR > 0.20 sec (5sb)

Characteristics of First Degree AV Block

1. Rate of underlying rhythm

2. Regular rhythm

3. P waves before QRS, upright, and uniform

4. PR > 0.20 sec

5. QRS are uniform and narrows (< 0.12 sec)

First Degree AV Block

Second-Degree Heart Block (Type I)

The progressive delay of the electrical impulse at the AV node produces an increase in the length of the PR interval

PR interval continues to increase in length until the impulse is not conducted or the QRS complex is "dropped"

What rhythm is referred to as Wenckebach

Second Degree AV Block Type 1

Cause of Second Degree AV Block Type 1

Abnormal AV Condition

AV ischemia

Digitalis therapy

Increased vagal tone

Characterisitics of Second Degree AV Block Type 1

1. Atrial rate is normal | Ventricular is slower

2. Atrial is regualr | Ventricular is irregular

3. P waves before each QRS and upright and uniform (if conducted)

4. PR progresses longer until QRS is not conducted

5. QRS are uniform and narrow (< 0.12 sec)

Second Degree AV Block Type 1

Second Degree AV Block Type 1

Second Degree AV Block Type 1

Second-Degree AV Block (Mobitz Type II)

intermittent interruption of conduction near or below the AV junction

SA node is generating electrical impulses at a regular rate

Some P waves are not followed by a QRS complex

What does a Second Degree AV BLock Mobitz 2 indicate

Increase risk for complete heart block

What is the ratio often seen with Second Degree AV Block Mobitz 2

2:1

3:1

4:1

Causes of Second Degree Block Mobitz 2

AMI

Septal Wall Necrosis

Acute Myocarditis

Advanced Artery Disease

Characteristics of Second Degree AV Block Mobitz Type 2

1. Atrial rate is normal | Ventricular can be bradycardic

2. Atrial rhythm is normal | Ventricular is irregular

3. P waves before each QRS but not all P waves are followed by QRS, all are upright and uniform

4. PR is constant

5. QRS is uniform and narrow (< 0.12) when present

Second Degree AV Block Mobitz Type 2

Second Degree AV Block Mobitz Type 2

Second Degree AV Block Mobitz Type 2

What isthe most serious heart block

Complete / Third Degree

Third Degree Heart Block often progress to

Asystole

Third-Degree AV Block (Complete)

Atria and ventricles are completely blocked and separated from each other electrically and beat independently of each other

SA node fires at 60 to 100 BPM

Ventricles paced by an escape pacemaker either at junctional tissues (narrow QRS complex) or ventricles (wide QRS complex)

What rhythm is also called AV dissociation

Third-Degree AV Block

Charaterisitcs of Third Degree AV Block

1. Atrial Rate = 60-100 bpm | Ventricular rate depends on pacemaker

2. Atrial and ventricular rhythm is regualr

3. P waves are upright and uniform but have no relationship with QRS

4. PR interval has no consistency

5. QRS are uniform but can be narrow or wide depending on site

Third-Degree (Complete)Heart Block

Third-Degree (Complete)Heart Block

Third-Degree (Complete)
Heart Block

When does First Degree Blocks need to be carefully watched

AMI

If a patient has a third degree AV block with narrow QRS and asymptomatic, where si the site of origin

AV junction

Treatment for Complete Heart Blcok

Atropine

Pacing

After transcutanous pacing, what is done for third degree block

Transvenous pacemaker