EKG arrhythmias and conduction

Arrhythmia

A contraction that does not follow normal electrical sequence or timing

Isolated arrhythmias

Usually do not cause harmful hemodynamic effects

Sustained arrhythmias

Can be dangerous and affect cardiac output

Normal sinus rhythm (NSR)

Electrical activity originates from SA node with normal P QRS T relationships

Four questions for rhythm analysis 1

Are normal P waves present

Four questions for rhythm analysis 2

Are QRS complexes narrow or wide

Four questions for rhythm analysis 3

What is the relationship between P waves and QRS complexes

Four questions for rhythm analysis 4

Is the rhythm regular or irregular

Sinus arrhythmia

Normal variation in heart rate with breathing

Inspiration effect on HR

Increases heart rate

Expiration effect on HR

Decreases heart rate

Sinus bradycardia

Normal rhythm with heart rate around or below 60 bpm

Sinus bradycardia significance

Common in early stages of acute myocardial infarction

Sinus tachycardia

Normal rhythm with heart rate above 100 bpm

Causes of sinus tachycardia

CHF severe lung disease or hyperthyroidism

Five types of arrhythmias 1

Normal pathway but abnormal rate or rhythm

Five types of arrhythmias 2

Ectopic rhythms from non SA node focus

Five types of arrhythmias 3

Reentrant arrhythmias due to electrical loop

Five types of arrhythmias 4

Conduction blocks causing delay or blockage

Five types of arrhythmias 5

Pre excitation via accessory pathways

Supraventricular arrhythmias

Originate in atria or AV node

Examples supraventricular beats

Premature atrial contractions and junctional beats

Examples sustained supraventricular arrhythmias

PSVT atrial flutter atrial fibrillation

Premature atrial contraction (PAC)

Early beat originating in atria

Junctional premature beat

Early beat from AV junction

Paroxysmal supraventricular tachycardia (PSVT)

Rapid regular rhythm from atria or AV node

PSVT rate

150 to 250 bpm

PSVT P waves

Often retrograde and inverted

Atrial flutter

Rapid regular atrial rhythm with saw tooth pattern

Atrial flutter atrial rate

250 to 350 bpm

Atrial flutter ventricular rate

Fraction of atrial rate such as 2:1 or 3:1

Atrial flutter key feature

Multiple P waves per QRS

Atrial fibrillation

Irregular rhythm with no distinct P waves

Atrial fibrillation atrial rate

350 to 500 bpm

Atrial fibrillation ventricular rate

Irregular and variable

Atrial fibrillation cause

Often hypertension or mitral valve disease

Atrial fibrillation baseline

Undulating or fibrillating waves

Ventricular arrhythmias

Originate below the AV node

Ventricular arrhythmia hallmark

Wide and bizarre QRS complexes

Reason for wide QRS

Slower cell to cell conduction not using His Purkinje system

Wide QRS definition

Greater than 0.1 to 0.12 seconds

Premature ventricular contraction (PVC)

Early ventricular beat with wide QRS

PVC morphology

Wide and bizarre QRS complex

PVC types

Unifocal or multifocal

Unifocal PVC

All PVCs look the same

Multifocal PVC

PVCs have different shapes

PVC rule of malignancy 1

Frequent PVCs

PVC rule of malignancy 2

Three or more consecutive PVCs

PVC rule of malignancy 3

Multifocal PVCs

PVC rule of malignancy 4

R on T phenomenon

PVC rule of malignancy 5

Occurring during acute MI

R on T phenomenon

PVC falls on preceding T wave increasing risk of dangerous arrhythmia

Ventricular tachycardia (V tach)

Three or more PVCs in a row

V tach rate

150 to 250 bpm

V tach effect

Reduces cardiac pumping efficiency

Ventricular fibrillation (V fib)

Chaotic rhythm with no identifiable P or QRS

V fib significance

Preterminal event requiring immediate treatment

Torsades de Pointes

Polymorphic ventricular tachycardia with twisting QRS complexes

Torsades key feature

QRS appears to spiral around baseline

Torsades association

Prolonged QT interval

Conduction block

Delay or obstruction of electrical conduction

Types of conduction blocks

Sinus node AV block and bundle branch block

AV block classification

First degree second degree and third degree

First degree AV block

Prolonged conduction from atria to ventricles

First degree AV block finding

PR interval greater than 0.20 seconds

First degree AV block pattern

Every P wave followed by QRS

Second degree AV block

Some impulses do not reach ventricles

Second degree AV block feature

More P waves than QRS complexes

Mobitz type I (Wenckebach)

Progressive PR lengthening until a QRS is dropped

Mobitz type I location

Block at AV node

Mobitz type II

Sudden dropped QRS without PR prolongation

Mobitz type II PR interval

Constant or normal length

Mobitz type II location

Block below AV node

Third degree AV block

Complete heart block with no conduction between atria and ventricles

Third degree AV block feature

AV dissociation

Third degree AV block atrial rate

60 to 100 bpm

Third degree AV block ventricular rate

30 to 45 bpm

Third degree AV block PR interval

Variable with no pattern

Third degree AV block treatment

Requires pacemaker

Bundle branch block (BBB)

Block in right or left bundle branch

BBB diagnosis

Based on QRS width and morphology

Normal QRS duration

Less than 0.12 seconds

Right bundle branch block (RBBB)

Delay in right ventricular conduction

RBBB QRS duration

Greater than 0.12 seconds

RBBB hallmark pattern

RSR prime bunny ears in V1 or V2

RBBB additional findings

ST depression and T wave inversion

RBBB reciprocal changes

Seen in V5 and V6

Incomplete RBBB

QRS duration between 0.10 and 0.12 seconds

Left bundle branch block (LBBB)

Delay in left ventricular conduction

LBBB QRS duration

Greater than 0.12 seconds

LBBB morphology

Broad notched R waves in I aVL V5 and V6

LBBB additional findings

ST depression and T wave inversion

LBBB reciprocal changes

Seen in V1 and V2

LBBB axis

May show left axis deviation