Clinical Teaching Ecg Interpretation
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Transcript of 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
Looking at the ECG you'll see that:
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.
Looking at the ECG you'll see that:
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
Looking at the ECG you'll see that:
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
Looking at the ECG you'll see that:
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.
Looking at the ECG you'll see that:
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)
Looking at the ECG you'll see that:
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