chapter 004ecgs made easy

Aehlert: ECGs Made Easy, 5th Edition

PowerPoint Lecture Notes

Chapter 04: Atrial Rhythms

Copyright © 2013 by Mosby, an imprint of Elsevier Inc.

Chapter 4

Atrial Rhythms

2 Copyright © 2013 by Mosby, an imprint of Elsevier Inc. All rights reserved.

Atrial Dysrhytmias, Premature

Complexes, Wandering Atrial

Pacemaker, and Multifocal Atrial

Tachycardia (MAT)

Copyright © 2013 by Mosby, an imprint of Elsevier Inc. All rights reserved. 3


Explain the concepts of altered automaticity,

triggered activity, and reentry.

Explain the terms bigeminy, trigeminy, quadrigeminy,

and run when used to describe premature

complexes.

Describe the ECG characteristics, possible causes,

signs and symptoms, and initial emergency care for

premature atrial complexes (PACs).

Learning Objectives


Explain the difference between a compensatory

and noncompensatory pause

Explain the terms wandering atrial pacemaker

and multifocal atrial tachycardia.

Describe the ECG characteristics, possible

causes, signs and symptoms, and initial

emergency care for wandering atrial pacemaker

(multiformed atrial rhythm).

Learning Objectives




emergency care for multifocal atrial tachycardia

(MAT).

List four examples of vagal maneuvers.

Learning Objectives



Atrial Dysrhytmias


Introduction

Atria

Thin-walled, low-

pressure chambers

Receive blood from

systemic circulation

and lungs

“Atrial kick”


Atrial dysrhythmias reflect abnormal electrical

impulse formation and conduction in the atria.

Atrial Dysrhythmias: Mechanisms



Atrial dysrhythmias may occur because of:

Altered automaticity

Triggered activity

Reentry

Altered automaticity and triggered activity are

disorders in impulse formation

Reentry is a disorder in impulse conduction

Atrial Dysrhythmias: Mechanisms


Can occur in:

Normal pacemaker cells

Myocardial working cells that do not normally function

as pacemaker sites

These cells depolarize and initiate impulses

before a normal impulse

Altered Automaticity


Results from abnormal electrical impulses that

sometimes occur during repolarization (after

depolarizations), when cells are normally quiet

Requires a stimulus to initiate depolarization

Triggered Activity


bernardm

Pencil


A condition in which an impulse returns to

stimulate tissue that was previously depolarized

Reentry (Reactivation)



Reentry requires:

A potential conduction

circuit or circular

conduction pathway

A block within part of

the circuit

Delayed conduction

with the remainder of

the circuit



Reentry results in a

single premature beat

or repetitive electrical

impulses resulting in

short periods of rapid

rhythms



Most atrial dysrhythmias are not life-threatening

Some are associated with extremely fast ventricular

rates

An excessively rapid heart rate may compromise

cardiac output

Atrial Dysrhythmias


Premature Complexes


Premature beats may be produced by:

Atria

AV junction

Ventricles

Premature beats appear early, that is, they occur

before the next expected beat

Premature Complexes



Premature beats are identified by their site of

origin

Premature atrial complexes (PACs)

Premature junctional complexes (PJCs)

Premature ventricular complexes (PVCs)

Premature Complexes


Pairs (coupled)

Two premature beats in a row

“Runs” or “bursts”

Three or more premature beats in a row

Bigeminy

Every other beat is a premature beat

Trigeminy

Every third beat is a premature beat

Quadrigeminy

Every fourth beat is a premature beat

Premature Complexes — Patterns


Occur when an irritable site within the atria

discharges before the next SA node impulse is

due to discharge

The P wave of a PAC may be:

Biphasic (partly positive, partly negative)

Flattened

Notched

Pointed

Lost in the preceding T wave

Premature Atrial Complexes



PACs—How Do I Recognize Them?


ECG Characteristics

Ventricular/atrial rhythm Regular with premature beats

Ventricular/atrial rate Usually within normal range, but depends on underlying rhythm

P waves Premature (occurring earlier than the next expected sinus P wave), positive (upright) in lead II, one before each QRS complex, often differ in shape from sinus P waves–may be flattened, notched, pointed, biphasic, or lost in the preceding T wave

S = SA node; = atrial beat

PACs—How Do I Recognize

Them?


ECG Characteristics

PR interval May be normal or prolonged depending on the prematurity of the beat

QRS duration Usually 0.11 sec or less but may be wide (aberrant) or absent, depending on the prematurity of the beat; the QRS of the PAC is similar in shape to those of the underlying rhythm unless the PAC is abnormally conducted

S = SA node; = atrial beat

PACs—How Do I Recognize

Them?


Sinus tachycardia at 111 beats/min with three PACs


A noncompensatory (incomplete) pause often

follows a PAC

Represents the delay during which the SA node resets

its rhythm for the next beat

The period between the complex before and after a

premature beat is less than two normal R-R intervals

Compensatory/Noncompensatory

Pause


A compensatory pause is present if the period

between the complex before and after a

premature beat is the same as two normal R-R

intervals.

PVC = premature ventricular complex

Compensatory/Noncompensatory

Pause


PACs associated with a wide QRS complex are

called “aberrantly conducted” PACs

Indicates conduction through ventricles is abnormal

Aberrantly Conducted PACs



A PAC may occur very prematurely and close to

the T wave of the preceding beat

Only a P wave may be seen with no QRS after it

(appearing as a pause)

This is a “nonconducted” or “blocked” PAC

P wave occurred too early to be conducted

Nonconducted PACs


Because both dysrhythmias have

a pause associated with them,

how would you differentiate

between a sinoatrial block and a

nonconducted PAC?


PACs—What Causes Them?

Acute coronary

syndromes

Atrial enlargement

Digitalis toxicity

Electrolyte imbalance

Emotional stress

Heart failure

Hyperthyroidism

Mental and physical

fatigue

Stimulants: caffeine,

tobacco, cocaine

Sympathomimetic

medications, such as

epinephrine

Valvular heart disease



Occasional PACs usually do not require

treatment

Frequent PACs may induce episodes of atrial

fibrillation or PSVT

Frequent PACs are treated by correcting the

underlying cause:

Correcting electrolyte imbalances

Reducing stress

Reducing or eliminating stimulants

Treating heart failure

PACs—What Do I Do About Them?


Wandering Atrial Pacemaker


Multiformed atrial rhythm

Updated term for the rhythm formerly known as

wandering atrial pacemaker

Size, shape, and direction of P waves vary

Wandering Atrial Pacemaker



Wandering Atrial Pacemaker—

How Do I Recognize It?


ECG Characteristics

Ventricular/atrial rhythm Usually irregular as the pacemaker site shifts from the SA node to ectopic atrial locations or AV junction

Ventricular/atrial rate Usually 60 to 100 beats/min, but may be slower; if the rate is faster than 100 beats/min, the rhythm is termed multifocal (or chaotic) atrial tachycardia

P waves Size, shape, and direction may change from beat to beat; may be upright, inverted, biphasic, rounded, flat, pointed, notched, or buried in the QRS complex


How Do I Recognize It?


ECG Characteristics

PR interval Varies as the pacemaker site shifts from the SA node to ectopic atrial locations or AV junction

QRS duration 0.11 sec or less unless abnormally conducted

May be observed in normal, healthy hearts

(particularly in athletes) and during sleep

May also occur with some types of organic heart

disease and with digitalis toxicity


What Causes It?



Usually produces no signs and symptoms unless

associated with a slow rate

If the rhythm occurs because of digitalis toxicity,

the drug should be withheld


What Do I Do About It?


Multifocal Atrial Tachycardia

(MAT)


When wandering atrial pacemaker is associated

with a ventricular rate faster than 100 beats/min,

the rhythm is called multifocal atrial tachycardia

(MAT) or chaotic atrial tachycardia

Multifocal Atrial Tachycardia



MAT—How Do I Recognize It?


ECG Characteristics

Ventricular/atrial rhythm Usually irregular as the pacemaker site shifts from the SA node to ectopic atrial locations or AV junction

Ventricular/atrial rate Faster than 100 beats/min

P waves Size, shape, and direction may change from beat to beat; may be upright, inverted, biphasic, rounded, flat, pointed, notched, or buried in the QRS complex

PR interval Varies as the pacemaker site shifts from the SA node to ectopic atrial locations or AV junction


Most often seen in patients with severe chronic

obstructive pulmonary disease

Also seen in the setting of acute coronary

syndromes, hypokalemia, or hypomagnesemia

May be a precursor of atrial fibrillation

MAT—What Causes It?


Treatment is directed at the underlying cause

If you know the rhythm is MAT and the patient is

symptomatic, consult a cardiologist

If patient is symptomatic but you are uncertain

rhythm is MAT:

Vagal maneuvers (if no contraindications), adenosine

MAT—What Do I Do About It?



Coughing

Squatting

Breath-holding

Carotid sinus massage

Application of a cold stimulus to the face

Valsalva’s maneuver

Gagging

Vagal Maneuvers


Carotid Sinus Massage







Can interrupt reentry pathways that involve the

AV node

Rapid onset of action

Short half-life

Adenosine


Supraventricular Tachycardias,

Atrial Flutter, and

Atrial Fibrillation




emergency care for atrial tachycardia (AT).

Explain the terms paroxysmal atrial tachycardia

(PAT) and paroxysmal supraventricular

tachycardia (PSVT).

Discuss the indications and procedure for

synchronized cardioversion

Learning Objectives




emergency care for atrioventricular nodal

reentrant tachycardia (AVNRT).



emergency care for atrioventricular reentrant

tachycardia (AVRT).

Learning Objectives




emergency care for atrial flutter.



emergency care for atrial fibrillation (AFib).

Learning Objectives



Supraventricular Tachycardias


Begin above the bifurcation of the bundle of His

Includes rhythms that begin in the:

SA node

Atrial tissue

AV junction

Supraventricular Arrhythmias


Types of Supraventricular

Tachycardias



Atrial tachycardia is a series of rapid beats from

an atrial ectopic focus

This rapid atrial rate overrides the SA node and

becomes the pacemaker

Paroxysmal atrial tachycardia (PAT)

Atrial tachycardia that starts or ends suddenly

Atrial Tachycardia


Atrial Tachycardia


Atrial Tachycardia—How Do I

Recognize It?


ECG Characteristics

Ventricular/atrial rhythm Regular

Ventricular/atrial rate 100 to 250 beats/min

P waves One P wave precedes each QRS complex in lead II; P waves differ in shape from sinus P waves; an isoelectric baseline is usually present between P waves; if the atrial rhythm originates in the low portion of the atrium, P waves will be negative in lead II. With rapid rates, it is difficult to distinguish P waves from T waves.


Atrial Tachycardia—How Do I

Recognize It?


ECG Characteristics

PR interval May be shorter or longer than normal


PSVT with 2:1 Block


P waves are clearly seen before the QRS complexes. Others

are hidden in the T waves. Atrial rate is 180 beats/min.

Ventricular rate is 90 beats/min.

Atrial Tachycardia—What Causes

It? Acute illness with

excessive

catecholamine release

Digitalis toxicity

Electrolyte imbalance

Heart disease

Coronary artery

disease

Valvular disease

Cardiomyopathies

Congenital heart

disease

Infection

Pulmonary embolism

Stimulant use

Caffeine

Albuterol

Theophylline

Cocaine



Possible assessment findings and symptoms:

Acute changes in mental status

Asymptomatic

Dizziness or lightheadedness

Dyspnea

Fatigue

Fluttering sensation in the chest

Hypotension

Ischemic chest discomfort

Palpitations

Signs of shock

Syncope or near-syncope

Atrial Tachycardia—What Do I Do

About It?


If symptomatic because of the rapid rate:

Apply pulse oximeter and administer oxygen if

indicated

Obtain vital signs

Establish IV access

Obtain 12-lead ECG


About It?


If symptomatic because of the rapid rate:

Vagal maneuvers

Adenosine drug of choice

Calcium channel blockers

Beta-blockers

Synchronized cardioversion if hemodynamic

compromise present


About It?



Delivery of an electrical shock to the heart timed

to occur during QRS

Synchronized Cardioversion


Some unstable narrow-QRS tachycardias

Unstable atrial fibrillation

Unstable atrial flutter

Unstable monomorphic ventricular tachycardia

Cardioversion—Indications


Cardioversion—Procedure







Most common type of SVT

Caused by reentry in the area of the AV node

AV Nodal Reentrant Tachycardia

(AVNRT)



AVNRT—How Do I Recognize It?


ECG Characteristics

Ventricular/atrial rhythm Ventricular rhythm is usually very regular

Ventricular/atrial rate 150 to 250 beats/min (usually 180 to 200 beats/min in adults)

P waves P waves are often hidden in the QRS complex. If the ventricles are stimulated first and then the atria, a negative (inverted) P wave will appear after the QRS in leads II, III, and aVF. When the atria are depolarized after the ventricles, the P wave typically distorts the end of the QRS complex.

AVNRT—How Do I Recognize It?


ECG Characteristics

PR interval P waves are not seen before the QRS complex, therefore the PR interval is not measurable


Common in individuals with no structural heart

disease

Triggers:

Hypoxia

Stress

Anxiety

Caffeine

Smoking

Sleep deprivation

Many medications

AVNRT—What Causes It?



AVNRT also occurs in individuals with:

COPD

Coronary artery disease

Valvular heart disease

Heart failure

Digitalis toxicity

AVNRT—What Causes It?


Possible assessment findings and symptoms:

AVNRT—What Do I Do About It?


Chest pain or pressure

Dizziness

Dyspnea

Heart failure

Lightheadedness

Nausea

Nervousness, anxiety

Palpitations (common)

Signs of shock

Syncope

Weakness

Stable patient

Apply pulse oximeter

• Administer supplemental oxygen, if indicated

Obtain vital signs

Establish IV access

Apply cardiac monitor

Obtain 12-lead ECG

Vagal maneuvers

Adenosine




Unstable patient

Apply pulse oximeter

• Administer supplemental oxygen, if indicated

Establish IV access

Administer sedation

• If the patient is awake and time permits

Synchronized cardioversion



Atrioventricular reentry tachycardia (AVRT)

involves a pathway of impulse conduction

outside the AV node and bundle of His

Pre-excitation

Impulse begins above the ventricles but travels via a

pathway other than AV node and bundle of His

Supraventricular impulse excites the ventricles earlier

than normal

AV Reentrant Tachycardia (AVRT)


AV Reentrant Tachycardia (AVRT)



Short PR interval

Delta wave

QRS widening

Secondary ST segment and T wave changes

WPW—How Do I Recognize It?






ECG Characteristics

Ventricular/atrial rhythm Regular, unless associated with atrial fibrillation

Ventricular/atrial rate Usually 60 to 100 beats/min, if the underlying rhythm is sinus in origin

P waves Normal and positive in lead II unless WPW is associated with atrial fibrillation

PR interval If P waves are observed, less than 0.12 sec

QRS duration Usually greater than 0.12 sec; slurred upstroke of QRS (delta wave) may be seen in one or more leads


Common cause of tachydysrhythmias in infants

and children

Accessory pathway in WPW is likely to be

congenital in origin

WPW—What Causes It?


Common signs and symptoms associated with

AVRT and a rapid ventricular rate include the

following:

Anxiety

Chest discomfort

Dizziness

Lightheadedness

Palpitations (common)

Shortness of breath during exercise

Signs of shock

Weakness

AVRT—What Do I Do About It?


If the patient is symptomatic because of the

rapid ventricular rate, treatment will depend on

the following:

Severity of patient symptoms

Width of the QRS complex (wide or narrow)

Regularity of the ventricular rhythm

Consultation with a cardiologist is recommended

AVRT—What Do I Do About It?



Atrial Flutter


Atrial Flutter

Ectopic atrial rhythm

in which an irritable

site within the atria

fires regularly at an

extremely rapid rate

Type I atrial flutter

Type II atrial flutter


Atrial Flutter—How Do I Recognize

It?


ECG Characteristics

Ventricular/atrial rhythm Atrial regular; ventricular regular or irregular depending on AV conduction and blockade

Ventricular/atrial rate With type I atrial flutter, the atrial rate ranges from 250 to 350 beats/min; with type II atrial flutter, the atrial rate ranges from 350 to 450 beats/min; the ventricular rate varies and is determined by AV blockade; the ventricular rate will usually not exceed 180 beats/min due to the intrinsic conduction rate of the AV junction


Atrial Flutter—How Do I Recognize

It?


ECG Characteristics

P waves No identifiable P waves; saw-toothed “flutter” waves are present

PR interval Not measurable

QRS duration 0.11 sec or less but may be widened if flutter waves are buried in the QRS complex or if abnormally conducted

Atrial flutter is usually a paroxysmal rhythm

precipitated by a PAC

May last for seconds to hours and occasionally lasts

24 hours or more

Chronic atrial flutter is unusual

Rhythm usually converts to sinus rhythm or atrial

fibrillation, on its own or with treatment

Atrial Flutter—What Causes It?


Atrial Flutter—What Causes It?

Cardiac surgery

Cardiomyopathy

Chronic lung disease

Complication of

myocardial infarction

Digitalis or quinidine

toxicity

Hyperthyroidism

Ischemic heart

disease

Mitral or tricuspid

valve stenosis or

regurgitation

Pericarditis or

myocarditis

Pneumonia

Pulmonary embolism



Cardiology consult recommended

If rapid ventricular rate, control ventricular

response

If rapid ventricular rate and signs of

hemodynamic compromise, synchronized

cardioversion

Atrial Flutter—What Do I Do About

It?


Atrial Fibrillation (AFib)


Atrial Fibrillation (AFib)



AFib—How Do I Recognize It?


ECG Characteristics

Ventricular/atrial rhythm Ventricular rhythm usually irregularly irregular

Ventricular/atrial rate Atrial rate usually 400 to 600 beats/min; ventricular rate variable

P waves No identifiable P waves, fibrillatory waves present; erratic, wavy baseline

PR interval Not measurable


AFib can occur with complete AV block

Ventricular rhythm will be slow and regular

AFib—How Do I Recognize It?


Can occur in patients with or without detectable

heart disease or related symptoms

Increased stroke risk

Atria do not contract effectively

Blood pools within the atria, forming clots

Clot dislodges and moves to artery in the brain

AFib—What Causes It?



AFib—What Causes It?

Acute pericarditis

Acute systemic infection

Advanced age

Advanced rheumatic

heart disease

After cardiac surgery

Cardiomyopathy

Chest trauma

Chronic lung disease

Congenital heart disease

Heart failure

Hyperthyroidism

Idiopathic (no clear

cause)

Ischemic heart disease

Pulmonary embolism

Valvular disease

Wolff-Parkinson-White

syndrome


Cardiology consult recommended

If rapid ventricular rate, control ventricular

response

If rapid ventricular rate and serious signs and

symptoms, synchronized cardioversion

Anticoagulation recommended if AFib has been

present for 48 hours or longer

AFib—What Do I Do About It?


Questions?


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