ecg made easy

ECGs MADE EASYECGs MADE EASY

NORMAL ECGNORMAL ECG

ELECTROCARDIOGRAMELECTROCARDIOGRAM

The electrocardiogram (ECG) is a graphic recording of the electrical potentials produced by the cardiac tissue.– Electrical impulse formation occurs within the

conduction system of the heart.– Excitation of the muscle fibers throughout the

myocardium results in cardiac contraction.

The ECG is recorded by applying electrodes to various locations on the body surface and connecting them to a recording apparatus.

The electrocardiogram (ECG) is a graphic recording of the electrical potentials produced by the cardiac tissue.– Electrical impulse formation occurs within the

conduction system of the heart.– Excitation of the muscle fibers throughout the

myocardium results in cardiac contraction.

The ECG is recorded by applying electrodes to various locations on the body surface and connecting them to a recording apparatus.


Clinical Value of the ECG– Atrial and ventricular hypertrophy– Myocardial ischemia and infarction– Pericarditis– Systemic diseases that affect the heart– Determination of the effect of cardiac drugs– Disturbances in electrolyte balance– Evaluation of function of cardiac pacemakers

Clinical Value of the ECG– Atrial and ventricular hypertrophy– Myocardial ischemia and infarction– Pericarditis– Systemic diseases that affect the heart– Determination of the effect of cardiac drugs– Disturbances in electrolyte balance– Evaluation of function of cardiac pacemakers


Considerable diagnostic value– Conduction delay of atrial and ventricular electrical

impulses– Determination of the origin and behavior of

dysrhythmias

Considerable diagnostic value– Conduction delay of atrial and ventricular electrical

impulses– Determination of the origin and behavior of

dysrhythmias


Value of ECG in the following clinical conditions– Prediction of sudden cardiac death– Prediction of ischemic pre-conditioning– Prediction of adverse states in AMI, post-MI and

silent ischemia cases– Progression/regression of LV mass

Value of ECG in the following clinical conditions– Prediction of sudden cardiac death– Prediction of ischemic pre-conditioning– Prediction of adverse states in AMI, post-MI and

silent ischemia cases– Progression/regression of LV mass

RECORDING AND MONITORING AN ECGRECORDING AND MONITORING AN ECG

Lead Configurations– Bipolar Leads

• Two electrodes placed at 2 different sites• Register the difference in potential between these 2

leads

– Unipolar leads• Measure the absolute electrical potential at one site• Requires a reference site• Reference site formed by the limb leads

Lead Configurations– Bipolar Leads

• Two electrodes placed at 2 different sites• Register the difference in potential between these 2

leads

– Unipolar leads• Measure the absolute electrical potential at one site• Requires a reference site• Reference site formed by the limb leads

12 LEAD ECG12 LEAD ECG

Limb LeadsRA Red Right arm

LA Yellow Left arm

LL Green Left leg

RL Black Right leg

Chest LeadsV1 Red 4th ICS RPSB

V2 Yellow 4th ICS LPSB

V3 Green Midway between V2 and V4

V4 Brown 5th ICS LMCL

V5 Black LAAL Lateral & horizontal to V4

V6 Violet LMAL Lateral & horizontal to V4

Limb LeadsRA Red Right arm

LA Yellow Left arm

LL Green Left leg

RL Black Right leg

Chest LeadsV1 Red 4th ICS RPSB

V2 Yellow 4th ICS LPSB

V3 Green Midway between V2 and V4

V4 Brown 5th ICS LMCL

V5 Black LAAL Lateral & horizontal to V4

V6 Violet LMAL Lateral & horizontal to V4

ELECTROPHYSIOLOGY OF THE HEARTELECTROPHYSIOLOGY OF THE HEART

Four Electrophysiologic Events Involved in the Genesis of the ECG– Impulse formation– Transmission of the impulse– Depolarization– Repolarization

Four Electrophysiologic Events Involved in the Genesis of the ECG– Impulse formation– Transmission of the impulse– Depolarization– Repolarization

TRANSMEMBRANE ACTION POTENTIALTRANSMEMBRANE ACTION POTENTIAL

REFRACTORINESSREFRACTORINESS

LAYERS OF THE HEART WALLLAYERS OF THE HEART WALL

Epicardium– Coronary arteries are

found in this layer

Myocardium– Responsible for

contraction of the heart

Endocardium– Lines the inside of the

myocardium– Covers the heart valves

Epicardium– Coronary arteries are

found in this layer

Myocardium– Responsible for

contraction of the heart

Endocardium– Lines the inside of the

myocardium– Covers the heart valves

CONDUCTION SYSTEM OF THE HEARTCONDUCTION SYSTEM OF THE HEART

SA NodeSA Node

Atrial MuscleAtrial MuscleAV NodeAV Node

Bundle of HisBundle of His

Bundle BranchesBundle Branches

Purkinje FibersPurkinje Fibers

Ventricular MuscleVentricular Muscle

MYOCARDIAL CELL TYPESMYOCARDIAL CELL TYPES

Primary Property

Contractility

AutomaticityConductivity

Primary Property

Contractility

AutomaticityConductivity

Primary Function

Contraction and Relaxation

Generation and conduction of electrical impulses

Primary Function

Contraction and Relaxation

Generation and conduction of electrical impulses

Where Found

Myocardium

Electrical conduction system

Where Found

Myocardium

Electrical conduction system

Kinds ofCardiac Cells

Myocardial cells

Specialized cells of the electrical conduction system

Kinds ofCardiac Cells

Myocardial cells

Specialized cells of the electrical conduction system

TERMINOLOGYTERMINOLOGY

Chronotropic Effect– Refers to a change in heart rate– A positive chronotropic effect refers to an increase in heart rate– A negative chronotropic effect refers to a decrease in heart rate

Dromotropic Effect– Refers to a change in the speed of conduction through the AV junction– A positive dromotropic effect results in an increase in AV conduction

velocity– A negative dromotropic effect results in a decrease in AV conduction

velocityInotropic Effect

– Refers to a change in myocardial contractility– A postive inotropic effect results in an increase in myocardial

contractility– A negative inotropic effect results in a decrease in myocardial

contractility

Chronotropic Effect– Refers to a change in heart rate– A positive chronotropic effect refers to an increase in heart rate– A negative chronotropic effect refers to a decrease in heart rate

Dromotropic Effect– Refers to a change in the speed of conduction through the AV junction– A positive dromotropic effect results in an increase in AV conduction

velocity– A negative dromotropic effect results in a decrease in AV conduction

velocityInotropic Effect

– Refers to a change in myocardial contractility– A postive inotropic effect results in an increase in myocardial

contractility– A negative inotropic effect results in a decrease in myocardial

contractility

TERMINOLOGYTERMINOLOGY

Waveform– Movement away from the baseline

in either a positive or negative direction

Segment– A line between wave forms

Interval– A waveform and a segment

Complex– Consists of several waveforms

Waveform– Movement away from the baseline

in either a positive or negative direction

Segment– A line between wave forms

Interval– A waveform and a segment

Complex– Consists of several waveforms

ECG PAPERECG PAPER

ELECTROGRAMELECTROGRAM

Upward deflection

Downward deflection

Diphasic deflection

Upward deflection

Downward deflection

Diphasic deflection

- +

- +

- +

AVF

I

AVR

AVL

THE NORMAL ELECTROCARDIOGRAMTHE NORMAL ELECTROCARDIOGRAM

P wave– Generated by activation of the atria

PR segment– Represents the duration of atrioventricular (AV)

conduction

QRS complex– Produced by activation of both ventricles

ST-T wave– Reflects ventricular recovery

P wave– Generated by activation of the atria

PR segment– Represents the duration of atrioventricular (AV)

conduction

QRS complex– Produced by activation of both ventricles

ST-T wave– Reflects ventricular recovery

STANDARD 12 LEAD ECGSTANDARD 12 LEAD ECG

The P wave– Atrial activation– Height < 0.2 mV (2 mm)– Duration < 0.12 sec

The P wave– Atrial activation– Height < 0.2 mV (2 mm)– Duration < 0.12 sec


P-R Interval– Intraatrial, internodal, His purkinje conduction– Duration 0.12 to 0.20 or 0.22 sec

P-R Interval– Intraatrial, internodal, His purkinje conduction– Duration 0.12 to 0.20 or 0.22 sec


The QRS Complex– Ventricular activation– Duration of 100 msec

The QRS Complex– Ventricular activation– Duration of 100 msec


The ST-segment– Phase 2 of transmembrane potential– Isoelectric in normal subjects

The ST-segment– Phase 2 of transmembrane potential– Isoelectric in normal subjects


The T wave– Upright after the age of 16– Juvenile T wave

The T wave– Upright after the age of 16– Juvenile T wave


The U wave– Surface reflection of negative after potential– Repolarization of Purkinje fibers– Ventricular relaxation

The U wave– Surface reflection of negative after potential– Repolarization of Purkinje fibers– Ventricular relaxation

STANDARD 12 LEAD ECGSTANDARD 12 LEAD ECGThe QT Interval

– From beginning of QRS to end of T wave– Reflects the duration of depolarization and

repolarization– Bezett: Q-Tc Interval = Q-T/ R-R

The QT Interval– From beginning of QRS to end of T wave– Reflects the duration of depolarization and

repolarization– Bezett: Q-Tc Interval = Q-T/ R-R

ANALYZING A RHYTHM STRIPANALYZING A RHYTHM STRIP

Rate

Rhythm

Axis

P wave

PR Interval

QRS Complex

T wave

Q-T Interval

Rate

Rhythm

Axis

P wave

PR Interval

QRS Complex

T wave

Q-T Interval


What is the rate?– To determine the ventricular rate,measure the

distance between 2 consecutive R-waves (R-R interval)

– To determine the atrial rate, measure the distance between 2 consecutive P-waves (P-P interval)

What is the rate?– To determine the ventricular rate,measure the

distance between 2 consecutive R-waves (R-R interval)

– To determine the atrial rate, measure the distance between 2 consecutive P-waves (P-P interval)

What Is The Rate?What Is The Rate?

Ventricular Rate– Small squares (R-R Interval) / 1500– Big squares (R-R Interval) / 300

Ventricular Rate– Small squares (R-R Interval) / 1500– Big squares (R-R Interval) / 300

What Is The Rate?What Is The Rate?

Sinus rhythm

Atrial Fibrillation– QRS complexes in 6-sec strip X 10

Sinus rhythm

Atrial Fibrillation– QRS complexes in 6-sec strip X 10


Is the rhythm regular or irregular?– To determine if the ventricular rhythm is regular or

irregular, measure the distance between 2 consecutive R-R intervals and compare that distance with the other R-r intervals.

– For atrial rhythm, measure the distance between 2 consecutive P-P intervals.

– Generally, a variation of up to 0.12 seconds (3 small boxes) is acceptable. The slower the heart rate, the more acceptable the variation.

Is the rhythm regular or irregular?– To determine if the ventricular rhythm is regular or

irregular, measure the distance between 2 consecutive R-R intervals and compare that distance with the other R-r intervals.

– For atrial rhythm, measure the distance between 2 consecutive P-P intervals.

– Generally, a variation of up to 0.12 seconds (3 small boxes) is acceptable. The slower the heart rate, the more acceptable the variation.


What Is The Axis?

Normal– 0 – (+90)

Left axis– 0 – (-90)

Right axis– (+90) – (+180)

Extreme axis– (-90) – (-180)

What Is The Axis?

Normal– 0 – (+90)

Left axis– 0 – (-90)

Right axis– (+90) – (+180)

Extreme axis– (-90) – (-180)

AVF

I

AVR

AVL

What Is The Axis?What Is The Axis?

}

}AVF

AVR

AVL

ILead I

AVF

10

10


Is there 1 P wave before each QRS?– Are P waves present and uniform in appearance?– Is there a P wave before each QRS or are there P

waves that are not followed by QRS complexes?– Is the atrial activity occurring so rapidly that there

are more atrial beats than QRS complexes?

Is there 1 P wave before each QRS?– Are P waves present and uniform in appearance?– Is there a P wave before each QRS or are there P

waves that are not followed by QRS complexes?– Is the atrial activity occurring so rapidly that there

are more atrial beats than QRS complexes?


Is the PR interval within normal limits?– If the PR interval is less than 0.12 or more than

0.20 second, conduction followed an abnormal pathway or the impulse was delayed in the area of the AV node.

– Is the PR interval of conducted beats constant or does it vary?

Is the PR interval within normal limits?– If the PR interval is less than 0.12 or more than

0.20 second, conduction followed an abnormal pathway or the impulse was delayed in the area of the AV node.

– Is the PR interval of conducted beats constant or does it vary?


Is the QRS narrow or wide?– What is the duration of the QRS complex?

• If it is 0.10 second or less (narrow), it is presumed to be supraventricular in origin.

• If it is greater than 0.12 second (wide), it is probably ventricular in origin.

– Do the QRS’s occur uniformly throughout the strip?

Is the QRS narrow or wide?– What is the duration of the QRS complex?

• If it is 0.10 second or less (narrow), it is presumed to be supraventricular in origin.

• If it is greater than 0.12 second (wide), it is probably ventricular in origin.

– Do the QRS’s occur uniformly throughout the strip?


Interpret the rhythm– Specifying the site where the dysrhythmia

originated (sinus), the mechanism (bradycardia), and the vetnricular rate.

– For example, “sinus bradycardia with a ventricular response (rate) of 38/min.”

Interpret the rhythm– Specifying the site where the dysrhythmia

originated (sinus), the mechanism (bradycardia), and the vetnricular rate.

– For example, “sinus bradycardia with a ventricular response (rate) of 38/min.”

ANALYZING RHYTHM STRIPANALYZING RHYTHM STRIP

Localization

I, AVL– High lateral

II, III, AVF– Inferior

Localization

I, AVL– High lateral

II, III, AVF– Inferior

AVF

I

AVR

AVL

ANALYZING THE RHYTHM STRIPANALYZING THE RHYTHM STRIP

Localization

V1,V2– Septal

V3,V4– Anterior

V5,V6– Apicolateral

V1-V3 or V4– Anteroseptal

V3 or V4-V6– Anterolateral

Localization

V1,V2– Septal

V3,V4– Anterior

V5,V6– Apicolateral

V1-V3 or V4– Anteroseptal

V3 or V4-V6– Anterolateral

V1-V6 – Extensive anterior

I,AVL,V5,V6 - Lateral

V1-V6 – Extensive anterior

I,AVL,V5,V6 - Lateral


How is the rhythm clinically significant?How is the rhythm clinically significant?

NORMAL SINUS RHYTHMNORMAL SINUS RHYTHM

RateRhythm

P waves

PR intervalQRS

RateRhythm

P waves

PR intervalQRS

60-100 beats per minuteAtrial regularVentricular regularUniform in appearance, upright, normal shape, one preceding each QRS complex0.12-0.20 second0.10 second or less. If greater than 0.10 second in duration, the QRS is termed “wide” since the existence of a bundle branch block or other intraventricular conduction defect cannot be accurately detected in a single-lead.

60-100 beats per minuteAtrial regularVentricular regularUniform in appearance, upright, normal shape, one preceding each QRS complex0.12-0.20 second0.10 second or less. If greater than 0.10 second in duration, the QRS is termed “wide” since the existence of a bundle branch block or other intraventricular conduction defect cannot be accurately detected in a single-lead.

Sinus RhythmsSinus Rhythms

Normal Sinus Rhythm

RateRhythm

P waves

PR intervalQRS

60-100 beats per minuteAtrial regularVentricular regularUniform in appearance, upright, normal shape, one preceding

each QRS complex0.12-0.20 second0.10 second or less. If greater than 0.10 second in duration,

the QRS is termed “wide” since the existence of a bundle branch block or other intraventricular conduction defect cannot be accurately detected in a single-lead.


Sinus BradycardiaRateRhythm

P waves

PR intervalQRS

Less than 60 beats per minuteAtrial regularVentricular regularUniform in appearance, upright, normal shape, one preceding

each QRS complex0.12-0.20 secondUsually 0.10 second or less


Sinus TachycardiaRateRhythm

P waves

PR intervalQRS

Usually 100-160 beats per minuteAtrial regularVentricular regularUniform in appearance, upright, normal shape, one preceding



Normal Heart Rates in ChildrenAge

NeonateInfant (6 mos)ToddlerPreschoolerSchool-agedAdolescent

Awake Heart Rate(per minute)

100-180100-16080-11070-11065-11060-90

Sleeping Heart Rate(per minute)

80-16075-16060-9060-9060-9050-90


Sinus Dysrhythmia (Arrhythmia)Rate

Rhythm

P waves

PR intervalQRS

Usually 100-160 beats per minute but may be faster or slowerIrregular (R-R intervals shorten during inspiration and

lengthen during expiration)Uniform in appearance, upright, normal shape, one preceding



Sinoatrial (SA) BlockRateRhythm

P waves

PR intervalQRS

Usually normal but varies because of pauseIrregular – the pause is the same as (or an exact multiple of)

the distance between two other P-P intervalsUniform in appearance, upright, normal shape, one preceding



Sinus ArrestRateRhythm

P waves

PR intervalQRS

Usually normal but varies because of the pauseIrregular – the pause is of undetermined length (more than

one PQRST complex is omitted) and is not the same distance as other P-P intervals.

Uniform in appearance, upright, normal shape, one preceding each QRS complex

0.12-0.20 secondUsually 0.10 second or less

Atrial RhythmsAtrial Rhythms

Premature Atrial Complexes1. Early (premature) P waves2. Upright P waves that differ in shape from normal sinus P waves in Lead II

• P waves may be biphasic (partly positive, partly negative), flattened, notched or pointed

3. The early P wave may or may not be followed by a QRS complex


Compensatory vs. Non-compensatory PauseTo determine whether or not the pause following a premature complex is

compensatory or non-compensatory, measure the distance between three normal beats. Compare that distance between three beats, one of which includes the premature complex.

Non-compensatory (incomplete) – if the normal beat following the premature complex occurs before it was expected (i.e., when the distance is not the same)

Compensatory (complete) – if the normal beat following the premature complex occurs when expected (i.e., when the distance is the same).


Premature Atrial Complexes (PACs)RateRhythmP waves

PR interval

QRS

Usually normal but depends on underlying rhythmEssentially regular with premature beatsPrematureDiffer from sinus P waves – may be flattened, notched, pointed,

biphasic, or lost in the preceding T waveVaries from 0.12-0.20 second when the pacemaker site is near

the SA node; 0.12 second when the pacemaker site is nearer the AV junction

Usually less than 0.10 second but may be prolonged. The QRS of the PAC is similar to those of the underlying rhythm unless the PAC is abnormally conducted.


Vagal ManeuversVagal maneuvers – are methods used to stimulate baroreceptors in the internal

carotid arteries and the aortic arch. Stimulation of these receptors results in reflex stimulation of the vagus nerve and release of acetylcholine. Acetylcholine slows conduction in the AV node, resulting in slowing of the heart rate

• Coughing• Bearing down• Squatting• Breath-holding• Carotid sinus pressure (massage)• Immersion of the face in ice water• Stimulation of the gag reflex

Carotid pressure should be avoided in older patients. Simultaneous, bilateral carotid pressure should never be performed.


The Unstable PatientSigns and Symptoms• Shock• Chest pain• Hypotension• Shortness of breath• Pulmonary congestion• Congestive heart failure• Acute myocardial infarction• Decreased level of consciousness


Supraventricular TachycardiaRateRhythmP waves

PR interval

QRS

150-250 beats per minuteRegularAtrial P waves may be seen which differ from sinus P waves (may

be flattened, notched, pointed, or biphasic). P waves are usually identifiable at the lower end of the rate range but are seldom identifiable at rates above 200. May be lost in the preceding T wave.

Usually not measurable because the P wave is difficult to distinguish from the preceding T wave. If P waves are seen, the RR interval will usually measure 0.12-0.20 second.

Less than 0.10 second unless an intraventricular conduction defect exists.


ELECTRICAL THERAPY – Synchronized CountershockDescription and PurposeSynchronized countershock reduces the potential for delivery of energy during the

vulnerable period of the T wave (relative refractory period). A synchronizing circuit allows the delivery of a countershock to be “programmed”. The machine searches for the peak of the QRS complex (R wave deflection) and delivers the shock a few milliseconds after the highest part of the R wave.

Indications:• Supraventricular tachycardia• Atrial fibrillation• Atrial flutter• Unstable ventricular tachycardia with pause


Wandering Atrial Pacemaker (Multiformed Atrial Rhythm)Rate

Rhythm

P waves

PR intervalQRS

60-100. If the rate is greater than 100 beats per minute, the rhythm is termed multifocal (or chaotic) atrial tachycardia.

Atrial – irregularVentricular - irregularSize, shape, and direction may change from beat to beat. At

least three different P waves are required for a diagnosis of wandering atrial pacemaker

Variable Usually less than 0.10 second unless an intraventricular

conduction defect exists


Atrial FlutterRate

Rhythm

P waves

PR intervalQRS

Atrial rate 250-350 beats per minute; ventricular rate variable – determined by AV blockade. The ventricular rate will usually not exceed 180 beats per minute due to the intrinsic conduction rate of the AV junction.

Atrial regularVentricular may be regular or irregularNot identifiable P waves; saw-toothed “flutter waves”Not measurableUsually less than 0.10 second but may be widened if flutter

waves are buried in the QRS complex or if an intraventricular conduction defect exists.


Atrial FribrillationRate

Rhythm

P waves

PR intervalQRS

Atrial rate usually greater than 350-400 beats per minute; ventricular rate variable

Ventricular rhythms usually very irregular; a regular ventricular rhythm may occur because of digitalis toxicity.

No identifiable P waves; fibrillatory waves present. Erratic wavy baseline.

Not measurableUsually less than 0.10 second but may be widened if an

intraventricular conduction defect exists.


Wolff-Parkinson-White (WPW) SyndromeRate

RhythmP waves

PR intervalQRS

If the underlying rhythm is sinus in origin, the rate is usually 60-100 beats per minute.

Regular unless associated with atrial fibrillationNormal and upright unless WPW is associated with atrial

fibrillationIf P waves are seen, less than 0.12 secondUsually greater than 0.12 second. Slurred upstroke of the

QRS complex (delta wave) is often seen in one or more leads)

Junctional RhythmsJunctional Rhythms

Premature Junctional ComplexesRate

RhythmP waves

PR interval

QRS

Usually normal, but depends on the underlying rhythmEssentially regular with premature beatsMay occur before, during, or after the QRSIf visible, the P wave is inverted in leads II, III, AVFIf the P wave occurs before the QRS, the PR interval will be

usually less than or equal to 0.12 second. If no P wave occurs before the QRS, there will be no PR interval.

Usually 0.10 second or less unless an intraventricular conduction defect exists.


Junctional Escape BeatRate

RhythmP waves

PR interval

QRS

Usually normal, but depends on the underlying rhythmEssentially regular with LATE beatsMay occur before, during, or after the QRSIf visible, the P wave is inverted in leads II, III, AVFIf the P wave occurs before the QRS, the PR interval will be




Junctional Escape RhythmRateRhythmP waves

PR interval

QRS

40 to 60 beats per minuteAtrial and ventricular rhythm very regularMay occur before, during, or after the QRSIf visible, the P wave is inverted in leads II, III, AVFIf the P wave occurs before the QRS, the PR interval will be




Accelerated Junctional RhythmRateRhythmP waves

PR interval

QRS





The Unstable PatientSigns and Symptoms• Shock• Chest pain• Hypotension• Shortness of breath• Pulmonary congestion• Congestive heart failure• Acute myocardial infarction• Decreased level of consciousness


Junctional TachycardiaRateRhythmP waves

PR interval

QRS




Ventricular RhythmsVentricular Rhythms

Premature Ventricular ComplexesRate

Rhythm

P wavesPR interval

QRS

Usually normal but depends on the underlying rhythmEssentially regular with premature beats. If the PVC is an

interpolated PVC, the rhythm will be regular.There is no P wave associated with the PVCNone with the PVCs because the ectopic beat originates in

the ventricleGreater than 0.12 second.Wide and bizarre.T wave frequently in opposite direction of the QRS complex.


Patterns of PVCs1. Pairs (couplets) – two sequential PVCs2. Runs or bursts – three or more sequential PVCs are called vntricular

tachycardia (VT)3. Bigeminal PVCs (ventricular bigeminy) – every other beat is a PVC4. Trigeminal PVCs (ventricular trigeminy) – every third beat is a PVC5. Quadrigeminal PVCs (ventricular quadrigeminy) – every fourth beat is a PVC


Common Causes of PVCs• Normal variant• Anxiety• Exercise• Hypoxia• Digitalis toxicity• Acid-base imbalance• Myocardial ischemia• Electrolyte imbalance (hypokalemia, hypocalcemia, hypercalcemia,

hypomagnesemia)• Congestive heart failure• Increased sympathetic tone• Acute myocardial infarction• Stimulants (alcohol, caffeine, tobacco)• Drugs (sympathomimetics, cyclic antidepressants, phenothiazines)


Warning Dysrhythmias

• Six or more PVCs per minute• PVCs that occurred in pairs (couplets) or in runs or three or

more (ventricular tachycardia)• PVCs that fell on the T wave of the preceding beat (R-on T

phenomenon)• PVCs that differed in shape (multiformed PVCs)


Ventricular Escape BeatRate

Rhythm

P wavesPR interval

QRS

Atrial and ventricular rate dependent upon the underlying rhythm.Irregular. The ventricular escape beat occurs LATE, after the next

expected sinus beat.There is no P wave associated with escape beat. None with the escape beat because the complex originates from

the ventricles.Greater than 0.12 second.T wave deflection is opposite that of the QRS complex.


Idioventricular (Ventricular Escape) RhythmRate

Rhythm

P wavesPR intervalQRS

Atrial not discernible, ventricular 20-40 beats per minuteAtrial not discernibleVentricular essentially regularAbsentNoneGreater than 0.12 second.T wave deflection is in the opposite direction of the QRS.


Accelerated Idioventricular RhythmRate

Rhythm


Atrial not discernible, ventricular 40-100 beats per minuteAtrial not discernibleVentricular essentially regularAbsentNoneGreater than 0.12 second.T wave deflection is in the opposite direction of the QRS.


Ventricular Tachycardia (VT)Rate

Rhythm

P waves

PR intervalQRS

Atrial rate not discernible, ventricular rate 100-250 beats per minute

Atrial rhythm not discernibleVentricular rhythm is essentially regularMay be present or absent; if present they have no set

relationship to the QRS complexes – appearing between the QRS’s at a rate different from that of the VT.

NoneGreater than 0.12 second.Often difficult to differentiate between the QRS and the T

wave.


VENTRICULAR TACHYCARDIA - CAUSES• Hypoxia• Exercise• R-on T PVCs• Catecholamines • Digitalis toxicity• Myocardial ischemia• Acid-base imbalance• Electrolyte imbalance • Ventricular aneurysm• Coronary artery disease• Rheumatic heart disease• Acute myocardial infarction • CNS stimulants (cocaine, amphetamines)


LONG QT INTERVAL - CAUSESDrug induced• Cyclic antidepressants• Phenothiazines• Type 1A antidysrhythmics (quinidine, procainamide, disopyramide)• Organophosphate insecticides

Eating disorders (bulimia, anorexia)

Electrolyte abnormalities (hypomagnesemia, hypokalemia, hypocalcemia)


ANTIDYSRHYTHMIC CLASSIFICATIONSGroup I

Group IIGroup IIIGroup IV

Primarily inhibit the fast sodium channel in cardiac tissue, resulting in an increased refractory period

1A - increased conduction velocity and prolong the action potential (Quinidine, Procainamide, Disopyramide)

1B - Either increase or have no effect on conduction velocity (Lidocaine, Phenytoin, Tocainide, Mexiletine)

1C - Decrease conduction velocity (Flecainide, Encainide)Beta-adrenergic blockers (Propranolol)Prolong repolarization (Bretylium, Amiodarone)Block slow calcium channels, resulting in decreased automaticity,

and depression of myocardial and smooth muscle contraction (Verapamil, Nifedipine, Diltiazem)


Torsades de Pointes (TdP)Rate

Rhythm


Atrial rate not discernible, ventricular rate 150-250 beats per minute

Atrial not discernibleVentricular may be regular or irregularNoneNoneGreater than 0.12 second.Gradual alteration in the amplitude and direction of the QRS


Ventricular FibrillationRate

RhythmP wavesPR intervalQRS

Cannot be determined since there are no discernible waves or complexes to measure

Rapid and chaotic with no pattern or regularityNot discernibleNot discernibleNot discernible


Defibrillation (Unsynchronized Countershock)Description and Purpose:The purpose of defibrillation is to produce momentary asystole. The shock

attempts to completely depolarize the myocardium and provide an opportunity for the natural pacemaker centers of the heart to resume normal activity. Defibrillation is a random delivery of energy – there is no relation of the discharge of energy to the cardiac cycle.

Indications:• Unstable ventricular tachycardia with a pulse• Pulseless ventricular tachycardia• Ventricular fibrillation• Sustained Torsades de Pointes


AsystoleRate

Rhythm


Ventricular usually indiscernible but may see some atrial activity.

Atrial may be discernible.Ventricular indiscernible.Usually not discernibleNot measurableAbsent


Causes of Pulseless Electrical Activity (MATCHx4ED)Myocardial infarction (massive acute)AcidosisTension pneumothoraxCardiac tamponadeHypovolemia (most common cause)HypoxiaHyperkalemiaHypothermiaEmbolus (massive pulmonary)Drug overdoses (cyclic antidepressants, calcium channel blockers, beta-blockers,

digitalis)

Atrioventricular BlocksAtrioventricular Blocks

Classification of AV Blocks

Degreeof block

Site of block

Partial (incomplete)blocks

Complete block

AV node

Infranodal Bundleof His

Bundlebranches

First-degree AV blockSecond-degree AV block type ISecond-degree AV block type IISecond-degree AV block 2:1 conduction

Third-degree AV block

First-degree AV blockSecond-degree AV block type IThird-degree AV block

Second-degree AV block type II – (uncommon)Third-degree AV block

Second-degree AV block type II – (more common)

Third-degree AV block


First Degree AV BlockRate

RhythmP waves

PR intervalQRS

Atrial and ventricular rates the same; dependent upon underlying rhythm.

Atrial and ventricular regularNormal in size and shapeOnly one P wave before each QRSProlonged (greater than 0.20 second) but constantUsually 0.10 second or less unless an intraventricular

conduction exists


Second-Degree AV Block, Type I (Wenckebach)Rate

Rhythm

P waves

PR interval

QRS

Atrial rate is greater than the ventricular rate. Both are often within normal limits.

Atrial regular (P’s plot through)Ventricular irregular.Normal in size and shape. Some P waves are not followed by

a QRS complex (more P’s than QRS’s).Lengthens with each cycle (although lengthening may be very

slight), until a P wave appears without a QRS complex. The PRI after the nonconducted beat.

Usually 0.10 second or less but is periodically dropped.


Second-Degree AV Block, Type II (Mobitz)Rate

Rhythm

P waves

PR interval

QRS

Atrial rate is greater than the ventricular rate. Ventricular rate is often slow.Atrial regular (P’s plot through)Ventricular irregular.Normal in size and shape. Some P waves are not followed by

a QRS complex (more P’s than QRS’s).Within normal limits or prolonged but always constant for the

conducted beats. There may be some shortening of the PRI that follows a nonconducted P wave.

Usually 0.10 second or greater, periodically absent after P waves.


Second-Degree AV Block, 2:1 ConductionRate

RhythmP waves

PR intervalQRS

Atrial rate is greater than the ventricular rate.Atrial regular (P’s plot through)Ventricular regular.Normal in size and shape; every other P wave is followed by a

QRS complex (more P’s than QRS’s)ConstantWithin normal limits if the block occurs above the bundle of

His (probably type I); wide if the block occurs at or below the bundle of His (probably type II); absent after every other P wave.


Complete (Third-Degree) AV BlockRate

Rhythm

P wavesPR interval

QRS

Atrial rate is greater than the ventricular rate. The ventricular rate is determined by the origin of the escape rhythm.

Atrial regular (P’s plot through). Ventricular regular. There is no relationship between the atrial and ventricular rhythm.

Normal in size and shape.None – the atria and ventricles beat independently of each

other, thus there is no true PR interval.Narrow or broad depending on the location of the escape

pacemaker and the condition of the intraventricular conduction system.

Narrow = junctional pacemaker; wide = ventricular pacemaker.


Classification of AV Blocks

Ventricular RhythmPR IntervalQRS Width

Ventricular RhythmPR Interval

QRS Width

Second-Degree AV Block Type I

IrregularLengthening

Usually narrow

Second-Degree AV Block, 2:1 Conduction

RegularConstant

May be narrow or wide

Second-Degree AV Block Type II

IrregularConstant

Usually wide

Complete (Third-Degree) AV Block

RegularNone – no relationship between P

waves and QRS complexesMay be narrow or wide

ecg made easy

Documents