BASIC ECG INTERPRETATION 2015. Conduction System Review.

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BASIC ECG INTERPRETATION 2015

Transcript of BASIC ECG INTERPRETATION 2015. Conduction System Review.

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BASIC ECG INTERPRETATION2015

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Conduction System Review

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CARDIAC CELLS

Current

Electrical charge flow from one point to another

Voltage

Energy measurement between positive and negative points

Measured in millivolts

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CARDIAC CELLS

Action Potential

Five Phase cycle reflecting the difference in concentration of electrolytes (Na+, K+, Ca++, Cl-) which are charged particles across a cell membrane

The imbalance of these charged particles make the cells excitable

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Cardiac Cell Action Potential

Phase 0 Depolarization

Rapid Na+ entry into cell

Phase 1 Early depolarization

Ca++ slowly enters cell

Phase 2 Plateau-continuation of

repolarization

Slow entry of Sodium and Calcium into cell

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Cardiac Cell Action Potential

Phase 3 Potassium is moved out of

the cell

Phase 4

Return to resting membrane potential

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CARDIAC CELLS

Current (flow of energy) of electrolytes from one side of the cell membrane to the other requires energy (ATP) Expressed as volts

Measured as ECG

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CARDIAC CELLS

Properties

1. Automaticity

1. Cardiac pacemaker cells create an electrical impulse without being stimulated from another source

2. Excitability

1. Irritability

2. Ability of cardiac muscle to respond to an outside stimulus, Chemical, Mechanical, Electrical

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CARDIAC CELLS

3.Conductivity

Ability of cardiac cell to receive an electrical impulse and conduct it to an adjoining cardiac cell

4.Contractility

Ability of myocardial cells to shorten in response to an impulse

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CONDUCTION SYSTEM

Sinoatrial Node (SA)

Primary pacemaker

Intrinsic rate 60-100/min

Located in Rt. Atrium

Supplied by sympathetic and para-sympathetic nerve fibers

Blood from RCA-60% of people

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CONDUCTION SYSTEM

Atrioventricular Junction

Internodal pathways merge

AV Node

Non-branching portion of the Bundle of His

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CONDUCTION SYSTEM

AV Node

Supplied by RCA – 85%-90% of people

Left circumflex artery in rest of people

Delay in conduction due to smaller fibers

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CONDUCTION SYSTEM

Bundle of His Located in upper

portion of interventricular septum

Intrinsic rate 40-60/min

Blood from LAD and Posterior Descending

Less vulnerable to ischemia

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CONDUCTION SYSTEM

Right & Left Bundle Branches LBB – Left Bundle Branch

Anterior Fasicle

Anterior portion left ventricle

Posterior Fascicle

Posterior portions of left ventricle

Septal Fasicle

Mid-spetum

RBB – Right Bundle Branch Right Ventricle

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CONDUCTION SYSTEM

Purkinje Fibers Intrinsic

pacemaker rate 20-40/min

Impulse spreads from endocardium to epicardium

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The ECG

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ECG

Records electrical voltage of heart cells

Orientation of heart

Conduction disturbances

Electrical effects of medications and electrolytes

Cardiac muscle mass

Ischemia / Infarction

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ECG Leads

Tracing of electrical activity between 2 electrodes

Records the Average current flow at any specific time in any specific portion of time

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ECG

Types of leads Limb Lead (I, II, III)

Augmented (magnified) Limb Leads (aVR, aVL, aVF)

Chest (Precordial) Leads (V1,V2,V3,V4,V5,V6)

Each lead has Positive electrode

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ECG Each lead ‘sees’

heart as determined by 2 factors 1. Dominance of

left ventricle

2. Position of Positive electrode on body

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ECG

Lead I

Negative electrode

Right arm

Positive electrode

Left arm

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ECG

Lead II

Negative Electrode Right Arm

Positive Electrode

Left Leg

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ECG

Lead III

Negative Lead Left Arm

Positive Lead

Left Leg

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ECG PAPER Graph Paper

Small boxes

1mm wide; 1 mm high

Horizontal axis

Time in seconds

1 mm box represents 0.04 seconds

ECG paper speed is 25 mm/second

One large box is 5 small boxes and =.20 seconds (.04sec x5)

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ECG PAPER

Waveforms

Movement from baseline

Positive (upward)

Negative (downward)

Isoelectric –along baseline

Biphasic - Both upward and downward

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ECG

P Wave

First waveform

Impulse begins in SA Node in Right Atrium

Downslope of P wave –is stimulation of left atrium

2.5 mm in height (max)

O.11 sec. duration (max)

Positive in Lead II

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A normal ECG waveform

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ECG

QRS Complex

Electrical impulse through ventricules

Larger than P wave due to larger muscle mass of ventricles

Follows P wave

Made up of a

Q wave

R wave

S wave

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ECG

Q wave

First negative deflection following P wave

Represents depolarization of the interventricular septum activated from left to right

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ECG

S wave

Negative waveform following the R wave

Normal duration of QRS

0.06 mm – 0.10 mm

Not all QRS Complexes have a Q, R and S

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ECG

T wave

Represents ventricular repolarization

Absolute refractory period present during beginning of T wave

Relative refractory period at peak

Usually 0.5 mm or more in height

Slightly rounded

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ECG

U wave Small waveform

Follows T wave

Less than 1.5 mm in amplitude

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ECG

J PointPoint where the

QRS complex and ST-segment meet

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ECG PR Interval

Measurement where P wave leaves baseline to beginning of QRS complex

0.12 - .20 sec.

QRS Interval

Measurement from beginning of the Q wave until the end of the S wave.

0.06 - .12 sec.

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ECG

QT interval

Begins at isoelectric line from end of S wave to the beginning of the T wave - 0.44 sec.

Represents total ventricular activity

Measured from beginning of QRS complex to end of T wave.

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ECG Analysis

Determine Rate Normal? Fast? Slow?

Atrial Rate? Ventricular Rate?

Is it Regular? ( R-R and P-P intervals) Regularly irregular ( pattern) or irregularly irregular?

Are P-waves Present? Are there p waves before every QRS?

Is the P-P interval constant?

Is The P-R interval normal?

Is the QRS normal? Is the morphology of the QRS the same?

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ECG Analysis Determining Rate

Rate Six Second Method

Two – 3 second markers

Count complexes and multiply x 10

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ECG

Normal Sinus Rhythm

Electrical activity activity starts in SA node

AV Junction

Bundle Branches

Ventricles

Depolarization of atria and ventricles

Rate: 60-100 /Regular

PR interval / QRS duration normal

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ECG

Sinus Bradycardia Sinus Node fires at a rate slower than

normal

Conduction occurs through atria, AV junction, Bundle Branches and Ventricles

Depolarization of atria and ventricles occurs

In adults – rate is slower than 60 / minute

Rate is regular

Why?

Athletes Vagal Stimulation

Medications Cardiac disease

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ECG

Sinus Bradycardia Causes

H’s Hypoxia

Hypovolemia

Hydrogen Ion (acidosis)

Hypo-Hyperkalemia

Hypoglycemia

Hypothermia

T’s Toxins

Tamponade

Tension Pneumothorax

Thrombosis

Trauma

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ECG

Sinus Tachycardia SA node fires faster than 100-180/minute

Normal pathway of conduction and depolarization

Regular rate

Why?

Coronary artery disease; Fear; anger; exercise;

Hypoxia;Fever

Treatment:

Treat Cause

Beta-Blockers

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ECG

Sinus Arrhythmia The SA node fires Irregularly / Rate 60-

100/min.

Normal pathway of electrical conduction and depolarization

PR and QRS durations are normal

Why?

Respiratory- Increases with inspiration; decreases with expiration

Often in children; Inferior Wall MI; Increased ICP;

Medications: Digoxin; Morphine

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ECG

Sinus Arrest SA node fails to initiate electrical impulse

for one or more beats

May see no beats on monitor or other pacemaker cells in the heart may take over

Rate: Variable ; Rhythm: Irregular

Why?

Hypoxia; Coronary artery disease; Hyperkalemia

Beta-Blockers; CA channel blockers; Increased vagal tone

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ECG

Premature Atrial Complexes An electrical cell within the atria fires

before the SA node fires

Rate: Usually closer to 100; Irregular rhythm

P wave usually looks abnormal and complex occurs before it should

Why?

Emotional stress; CHF; Acute coronary syndromes

Stimulants; Digitalis Toxicity; etc.

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ECG

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ECG

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ECG

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ECG

Supraventricular Tachycardiac (SVT) Fast rhythms generated ‘Above the Ventricles’ Paroxysmal SVT (starts or ends suddenly) Rate – usually 130-250 Why? Stimulants; Infection; Electrolyte

Imbalance

MI; Altered atrial pathway (WPW)-Kent

S & S Lightheadedness; Palpitations; SOB; Anxiety;

Weakness

Dizziness; Chest Discomfort; Shock

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ECG

Atrial Flutter Irritable focus within the atrium typically fires at a

rate of about 300 bpm

Waveforms resemble teeth of a saw

AV node cannot conduct faster than about 180 beats/minute

Atrial vs ventricular rate expressed as a ratio

Why: Re-entry- Hypoxia Pulmonary embolism

MI Chronic Lung diseasePneumonia etc.

S & S: SOB; Weakness; Dizziness; Fatigue; Chest discomfort

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ECG

                                                                                                                     

          

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ECG

Atrial Fibrillation

Irritable sites in atria fire at a rate of 400-600/minute

Muscles of atria quiver rather than contract (fibrillate)

No P waves – only an undulating line

Only a few electrical impulses get through to the ventricles – may be a lot of impulses or a few

A lot of impulses (ventricular rate high- then called atrial fibrillation with rapid ventricular response)

A few impulses (ventricular rate slow – then called atrial fibrillation with slow ventricular response)

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ECG AV Block

Delay or interruption in impulse conduction Classified according to degree of block and/or to site of

block

First Degree Block

Impulses from SA node to the ventricles is DELAYED but not blocked

Why? Ischemia

Medications

Hyperkalemia

Inferior MI

Increased Vagal Tone

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ECG

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ECG

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ECG

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ECG Second Degree Block Type I - Wenckebach

Lengthening of the PR interval and then QRS wave is dropped

Why? Usually RCA occlusion (90% of

population) Ischemia

Increase in parasympathetic tone

Medications

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ECG

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ECG

The dropped QRS

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ECG

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ECG

Second Degree AV Block – Mobitz Type II

Why Ischemia LCA – Anterior MI

Organic heart disease

Important:

Ventricular Rate

QRS duration

How many dropped QRS’s in relation to P waves?

What is the ratio?

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ECG

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ECG

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ECG

Third Degree AV Block (Complete Block)

No P waves are conducted to the ventricles The atrial pacemakers and ventricle pacemakers

are firing independently Why?

Inferior MI

Anterior MI

Serious

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ECG

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ECG

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ECG

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ECG Ventricular Rhythms

Are the heart’s least efficient pacemakers Generate impulses at 20-40/min They assume pace-making if:

SA nodes fail, very slow (below 20-40) or are blocked

Ventricles site(s) is irritable

Irritable due to ischemia

Depolarization route is abnormal and longer, therefore QRS looks different and is wider.

T wave is opposite in direction to QRS

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ECG Premature Ventricular Contractions

May be from One Site and all look the same

Called Unifocal (from one focus or foci)

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ECG May be from Different sites (Foci) and are called

Multifocal PVC’s

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ECG May occur every other beat – Ventricular Bigeminy

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ECG

May occur every third beat – Ventricular Trigeminy

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ECG R on T PVC

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ECG

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ECG Couplets (2 PVC’s in a row); Triplets (3 PVC’s in a row)

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ECG Couplets also known as ‘Salvos’.

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ECG Run of PVC’s

Ventricular Tachycardia

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ECG Ventricular Tachycardia

Defined as Three or more PVC’s occurring in a row at a rate > 100/min

Wide QRS No P waves No T waves Why?

Ischemia

Infarction

Congenital

Usually lethal

S & S: Weakness, Dizziness, Shock, Chest Pain,Syncope

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ECG

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ECG

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ECG Torsades de Pointes (Twisting of the Points)

Ventricular Tachycardia in which the QRS changes in shape, amplitude and width

Causes: Hypomagnesium

Hypokalemia

Quinidine therapy

S & S: Altered mental status, shock, Chest pain, SOB, Hypotension

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ECG

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ECG

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ECG Ventricular Fibrillation

Chaotic rhythm of the ventricles Lethal if not treated Causes:

AMI

Electrolyte Imbalance

Drug OD’s

Trauma

Heart Failure

Vagal Stimulation

Increased SNS

Electrocutions

Congenitial Heart defects

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ECG

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ECG

Pulseless Electrical Activity – PEA Rhythm on monitor but no corresponding pulse

Why? Look for Cause!

H’s and T’s

Hypoxia Toxins

Hypovolemia Tamponade, cardiac

Hydrogen Ion (acidosis) Tension Pneumothorax

Hypo-Hyperkalemia Thrombosis (coronary or pulmonary)

Hypoglycemia Trauma (Increased ICP, hypovolemia

Hypothermia

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ECG

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ECG

Asystole No electrical activity on monitor No pulse Why? Look for Cause! H’s and T’s

Hypoxia Toxins

Hypovolemia Tamponade, cardiac

Hydrogen Ion (acidosis) Tension Pneumothorax

Hypo-Hyperkalemia Thrombosis (coronary or pulmonary)

Hypoglycemia Trauma (Increased ICP, hypovolemia)

Hypothermia

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Thanks for Coming!Questions?