clinical teaching ecg interpretation

7/28/2019 Clinical Teaching Ecg Interpretation

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Clinical teaching onECG INTERPRETATION


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Anatomy and Physiology of Cardiac Cycle:


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BASICS OF ECG:

The PQRST of Normal Sinus Rhythm

P WAVE - It represents atrial depolarization(electrical stimulation) and when it

occurs on the EKG or strip we know that the atrial cells have received the stimulus

from the SA Node.


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PR INTERVAL: The PR interval measures the time it takes the impulse to travel

from the atria to the ventricles.

QRS complex : It represents ventricular depolarization and when it occurs we

know the ventricular cells have received the stimulus. It is measuring the time it

takes the impulse to travel through the ventricles.


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ST SEGMENT: an isolectric line following the QRS complex. It is telling us thatthe ventricles are repolarizing.

T WAVE: last wave form during a Normal sinus rhythm (NSR). When this occurs

we know that the ventricles have recovered and are ready for the next impulse tooccur.

The Cardiac Cycle Family :

1. The cardiac cycle family includes the P wave, QRS and ST segments and theT Wave

2. When the cardiac cycle is normal all of the waveforms (PQRST) will bepresent on the rhythm strip of EKG

3. All of these waveforms can be positive (above the isoelectric line), negative(below the isoelectric time) or biphasic (waveforms with components above

and below the isoelectric line)


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RECOGNIZING NORMAL SINUS RHYTHM ON AN EKG STRIP.

The EKG paper is divided into small squares and large squares. Each large square

contais 25 small quares.

1. On the horizontal line, one small square represents .04 seconds and one largesquare represents .20 seconds in time

2. On the vertical line one small square represents 1 mm and one large squarereoresebts 5mm in voltage.

3. 30 large squares equals 6 seconds in time. When calculating time for thedifferent waves, segments and complexes you count the amount of small

squares and multiply by o.4

4. When calculating the heart rate., you are also counting the ventricular rate:count the number of squares inbetween the two spikes of the QRS complex..

5. 30 large squares equal 6 second strips. You can calculate the HR bycounting how many QRS complexes there are in a six second time frame and

multiplying by ten.


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Normal Sinus Rhytm Requirements :

1. Ventricular Rate: 60-100bpm2. Ventricular Rhythm: Regular3. Ventricular rhythm is determined by measuring the R-R interval. The R-R

interval is the dcistance between 2 QRS complexes

4. PWAVES: P waves should be present, a P wave for ever QRS and theconfiguration normal for eh lead. P waves should be upright in Lead II and

the can be upright, biphasic or inverted in Lead V1 (rhythm strips on

telemetry floors and the bottom of the 12 lead ekg, are lead II)

5. Atrial Rate : 60- 1006. Count how many boxes inbetween the p waves. Or , on a second strip count

how many p waves and multiply by 10.

Normal Sinus Rhytm Requirements :

1. Atrial Rhythm is determined by measuring the P-P interval . They should bethe same distance between on each measured. A variation of 0.12 seconds (3

small squares) can occur and the rhythm is considered regular.

2. PR Interval: The PR interval measures the time it takes the impulse to travelfrom the atria to the ventricles.

3. QRS: The QRS duration measures the time it takes the impulse to travelthrough the ventricles.

4. Twaves should all have the same configuration. Twaves have a wealth ofinformation in them and is important to study, they are almost the most

unstable component of an EKG. A different T wave configuration does not

always mean something is going on.


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NORMAL SINUS RHYTHM BY THE NUMBERS


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ABNORMALITIES THAT CAN BE DIAGNOSED WITH EKG

Shortened QT interval

1. Hyperkalemia,2. some drugs,3. certain genetic abnormalities

Prolonged QT interval:

1. Hypokalemia2. some drugs3. certain gentic abnormalities

Flattened or Inverted T waves

1. Coronary Ischemia,2. hypokalemia,3. Left Ventricular hypertropy4. Digoxin effect5. some drugs.

Hyperacute T Waves

1. 1st sign of acute MI, where T waves become more prominent, symmetricaland pointed

PVCs present:

Low MagnesiumPeaked Twaves, widened QRS complex, Depressed ST

HyperkalemiaFlattened T waves, Prominent U WAVES

Hypokalemia


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ARRYTHMIA /DYSRYTHMIA

Sinus Bradycardia

A heart rate less than 60 beats per minute (BPM). This in a healthy athletic person

may be 'normal', but other causes may be due to increased vagal tone from drug

abuse, hypoglycaemia and brain injury with increase intracranial pressure (ICP) as

examples


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Looking at the ECG you'll see that:

Rhythm - Regular Rate - less than 60 beats per minute QRS Duration - Normal P

Wave - Visible before each QRS complex P-R Interval - Normal Usually benign

and often caused by patients on beta blockers

SINUS TACHYCARDIA

An excessive heart rate above 100 beats per minute (BPM) which originates from

the SA node. Causes include stress, fright, illness and exercise. Not usually a

surprise if it is triggered in response to regulatory changes e.g. shock. But if their is

no apparent trigger then medications may be required to suppress the rhythm


Rhythm - Regular Rate - More than 100 beats per minute QRS Duration - Normal

P Wave - Visible before each QRS complex P-R Interval - Normal The impulse

generating the heart beats are normal, but they are occurring at a faster pace than

normal. Seen during exercise


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Supraventricular Tachycardia (SVT) Abnormal

1. A narrow complex tachycardia or atrial tachycardia which originates in the'atria' but is not under direct control from the SA node. SVT can occur in all

age groups

2. Looking at the ECG you'll see that:3. Rhythm - Regular4. Rate - 140-220 beats per minute5. QRS Duration - Usually normal6. P Wave - Often buried in preceding T wave7. P-R Interval - Depends on site of supraventricular pacemaker8. Impulses stimulating the heart are not being generated by the sinus node, but

instead are coming from a collection of tissue around and involving the

atrioventricular (AV) node


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Atrial Fibrillation

1. Many sites within the atria are generating their own electrical impulses,leading to irregular conduction of impulses to the ventricles that generate the

heartbeat. This irregular rhythm can be felt when palpating a pulse

2. Looking at the ECG you'll see that:3. Rhythm - Irregularly irregular Rate - usually 100-160 beats per minute but

slower if on medication QRS Duration - Usually normal P Wave - Not

distinguishable as the atria are firing off all over P-R Interval - Not

measurable The atria fire electrical impulses in an irregular fashion causing

irregular heart rhythm Fibrillation4. Many sites within the atria are generating their own electrical impulses,

leading to irregular conduction of impulses to the ventricles that generate the

heartbeat. This irregular rhythm can be felt when palpating a pulse

5. Looking at the ECG you'll see that:6. Rhythm - Irregularly irregular Rate - usually 100-160 beats per minute but

slower if on medication QRS Duration - Usually normal P Wave - Not

distinguishable as the atria are firing off all over P-R Interval - Not

measurable The atria fire electrical impulses in an irregular fashion causing

irregular heart rhythm


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Atrial Flutter

1. Looking at the ECG you'll see that:2. Rhythm - Regular Rate - Around 110 beats per minute QRS Duration -

Usually normal P Wave - Replaced with multiple F (flutter) waves, usually

at a ratio of 2:1 (2F - 1QRS) but sometimes 3:1 P Wave rate - 300 beats per

minute P-R Interval - Not measurable As with SVT the abnormal tissuegenerating the rapid heart rate is also in the atria, however, the

atrioventricular node is not involved in this case.

1st Degree AV Block

1. 1st Degree AV block is caused by a conduction delay through the AV nodebut all electrical signals reach the ventricles. This rarely causes any

problems by itself and often trained athletes can be seen to have it. The

normal P-R interval is between 0.12s to 0.20s in length, or 3-5 small squares

on the ECG.

2. Looking at the ECG you'll see that:3. Rhythm - Regular Rate - Normal QRS Duration - Normal P Wave - Ratio

1:1 P Wave rate - Normal P-R Interval - Prolonged (>5 small squares)


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2nd Degree Block Type 1 (Wenckebach)

1. Another condition whereby a conduction block of some, but not all atrialbeats getting through to the ventricles. There is progressive lengthening of

the PR interval and then failure of conduction of an atrial beat, this is seen

by a dropped QRS complex.

2. Looking at the ECG you'll see that:3. Rhythm - Regularly irregular Rate - Normal or Slow QRS Duration -

Normal P Wave - Ratio 1:1 for 2,3 or 4 cycles then 1:0. P Wave rate -

Normal but faster than QRS rate P-R Interval - Progressive lengthening of P-

R interval until a QRS complex is dropped

2nd Degree Block Type 2

1. When electrical excitation sometimes fails to pass through the A-V node orbundle of His, this intermittent occurance is said to be called second degree

heart block. Electrical conduction usually has a constant P-R interval, in the

case of type 2 block atrial contractions are not regularly followed by

ventricular contraction


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2. Looking at the ECG you'll see that:3. Rhythm - Regular Rate - Normal or Slow QRS Duration - Prolonged P

Wave - Ratio 2:1, 3:1 P Wave rate - Normal but faster than QRS rate P-R

Interval - Normal or prolonged but constant

3rd Degree Block

1. 3rd degree block or complete heart block occurs when atrial contractions are'normal' but no electrical conduction is conveyed to the ventricles. The

ventricles then generate their own signal through an 'escape mechanism'

from a focus somewhere within the ventricle. The ventricular escape beats

are usually 'slow'

2. Looking at the ECG you'll see that:3. Rhythm - Regular Rate - Slow QRS Duration - Prolonged P Wave -

Unrelated P Wave rate - Normal but faster than QRS rate P-R Interval -

Variation Complete AV block. No atrial impulses pass through the

atrioventricular node and the ventricles generate their own rhythm


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Bundle Branch Block

Abnormal conduction through the bundle branches will cause a depolarization

delay through the ventricular muscle, this delay shows as a widening of the QRS

complex. Right Bundle Branch Block (RBBB) indicates problems in the right side

of the heart. Whereas Left Bundle Branch Block (LBBB) is an indication of heartdisease. If LBBB is present then further interpretation of the ECG cannot be

carried out.


Rhythm - Regular Rate - Normal QRS Duration - Prolonged P Wave - Ratio 1:1 P

Wave rate - Normal and same as QRS rate P-R Interval - Normal

Premature Ventricular Complexes

Due to a part of the heart depolarizing earlier than it should


Rhythm - Regular Rate - Normal QRS Duration - Normal P Wave - Ratio 1:1 P

Wave rate - Normal and same as QRS rate P-R Interval - Normal Also you'll see 2

odd waveforms, these are the ventricles depolarising prematurely in response to a


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signal within the ventricles.(Above - unifocal PVC's as they look alike if they

differed in appearance they would be called multifocal PVC's, as below)

Junctional Rhythms


Rhythm - Regular Rate - 40-60 Beats per minute QRS Duration - Normal P Wave

- Ratio 1:1 if visible. Inverted in lead II P Wave rate - Same as QRS rate P-R

Interval - Variable Below - Accelerated Junctional Rhythm

Ventricular Tachycardia (VT) Abnormal

1. Looking at the ECG you'll see that:2. Rhythm - Regular Rate - 180-190 Beats per minute QRS Duration -

Prolonged P Wave - Not seen Results from abnormal tissues in the ventricles


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generating a rapid and irregular heart rhythm. Poor cardiac output is usually

associated with this rhythm thus causing the pt to go into cardiac arrest.

Shock this rhythm if the patient is unconscious and without a pulse

Ventricular Fibrillation (VF) Abnormal

Disorganised electrical signals cause the ventricles to quiver instead of contract in

a rhythmic fashion. A patient will be unconscious as blood is not pumped to the

brain. Immediate treatment by defibrillation is indicated. This condition may occur

during or after a myocardial infarct.


Rhythm - Irregular Rate - 300+, disorganised QRS Duration -Not recognisable P

Wave - Not seen This patient needs to be defibrillated!! QUICKLY

Asystole - Abnormal

1. Looking at the ECG you'll see that:


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2. Rhythm - Flat Rate - 0 Beats per minute QRS Duration - None P Wave -None

3. Carry out CPR!!

Myocardial Infarct (MI)


Rhythm - Regular Rate - 80 Beats per minute QRS Duration - Normal P Wave -

Normal S-T Element does not go isoelectric which indicates infarction

LABORATORY TESTS

CMP

Look for electrolyte imbalances.

Particularly look for K+

Precath look at renal functioning due to dye.

Magnesium level

CBC

Complete blood count,

Focus on hemoglobin and hematocrit

BNP

High levels are an indicator for congestive heart failure


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PT/INR

especially if patient is on anticoagulation therapy

SCREENING CARDIAC PANEL

TROPONIN

High specificity for myocardial cell injurty, cardiac troponin and cardiac

troponin1 helpful in evaluation of patients with chest pain

More specific for cardiac injury than CPK-MB

Elevation sooner and remain elevated longer than CPK-MB

Allows longer time for Dx and thrombolytic tx of MI.

Used for differentiating cardiac from non cardiac chest pain

Evaluation of patients with unstable angina

Estimate the size of the MI

Detect preop MI

SCREENING CARDIAC PANEL

CPK-MB ( creatine phosphokinase)

Specific for myocardial cells

Levels rise three to six hours after damage

If damage is not persistent the levels peak at 18 hours post damage

Returns to normal after two to three days


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Cardiac panels are usually done in serial draws. Usually q 8hrs, or q4/12/24hrs.

After admit.

DIAGNOSTIC TESTS

1. EKG2. ECHOCARDIOGRAM3. STRESS ECHO4. TILT TABLE TEST5. CARDIAC CATHERIZATION6. ELECTROPHYSIOLOGY TEST7. CT HEART SCAN8. MYOCARDIAL BIOPSY9. HEART MRI10.PERICARDIOCENTESIS

ECG/EKG PROCEDURE

ECG Basics

The electrocardiogram (ECG) is a diagnostic tool that measures and records the

electrical activity of the heart in detail. Being able to interpretate these details

allows diagnosis of a wide range of heart problems.

ECG Electrodes

Skin Preparation:

Clean with an alcohol wipe if necessary. If the patients are very hairy shave the

electrode areas.

ECG standard leads


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There are three of these leads, I, II and III. Lead I: is between the right arm and

left arm electrodes, the left arm being positive. Lead II: is between the right arm

and left leg electrodes, the left leg being positive. Lead III: is between the left arm

and left leg electrodes, the left leg again being positive.

Chest Electrode Placement

V1: Fourth intercostal space to the right of the sternum.

V2: Fourth intercostal space to the Left of the sternum.

V3: Directly between leads V2 and V4.

V4: Fifth intercostal space at midclavicular line.

V5: Level with V4 at left anterior axillary line.V6: Level with V5 at left midaxillary line. (Directly under the midpoint of the

armpit)


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LEAD PLACEMENT ILLUSTRATIONS

A little More Info about EKG:

Chest Leads

V1 & V2

V3 & V4

V5 & V6

View

Right Ventricle

Septum/Lateral Left Ventricle

Anterior/Lateral Left Ventricle


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Atrial contractions show up as the P wave. Ventricular contractions show as a series known as the QRS complex. The third and last common wave in an ECG is the T wave. This is the

electrical activity produced when the ventricles are recharging for the next

contraction (repolarizing).

Interestingly, the letters P, Q, R, S, and T are not abbreviations for anyactual words but were chosen many years ago for their position in the middle

of the alphabet.

The electrical activity results in P, QRS, and T waves that are of differentsizes and shapes. When viewed from different leads, these waves can show a

wide range of abnormalities of both the electrical conduction system and the

muscle tissue of the hearts 4 pumping chambers.

CONCLUSION

So far we have discussed on the anatomy and physiology of the heart , basics of

Ecg , Arrthymias

Nurses play and important role in identification of abnormal ecg rhythms .Thereby

to provide prompt interventions in treating patients

clinical teaching ecg interpretation

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