EKG Interpretation Azam Shafquat F.H.R.S., King Faisal Specialists Hospital and Research Center, Riyadh Objectives To understand the importance of standardized techniques for EKG acquisition To recognize the features of a normal electrocardiogram To recognize the common EKG misdiagnosis due to inappropriate acquisition of EKGs 1
RATE The EKG paper speed is 25 mm/s In 1 second the paper travels 25mm Each large square (5mm) is equivalent to 0.2 seconds Each small square is therefore 0.04 seconds Rate Easy way to calculate is to find a QRS falling on a heavy line and then count large squares till the next QRS Count 300/150/100/75/60/50 Alternatively count the number of large squares and divide 300 by the number of large squares Alternatively 1500 divided by number of small squares 2
So what s the rate? Rate? A. 60-80/min B. 80-100/ min C. 100-150 D. >150 3
Rate? A. 60-80/min B. 80-100/ min C. 100-150 D. >150 WHAT S ODD ABOUT THIS EKG? Rate? A. 60-80/min B. 80-100/ min C. 100-150 D. >150 4
Question? The correct position for placement of Chest Leads (V1 V6) is A. V1 and V2 in 2 nd Intercostal space B. V4 is placed 2 Intercostal spaces below V2 C. V5 is placed in the 5 th Intercostal space D. V6 is placed in the mid axillary line 5
Electrode Positions for 12 Lead EKG The correct position for placement of Chest Leads (V1 V6) is A. V1 and V2 in 2 nd Intercostal space B. V4 is placed 2 Intercostal spaces below V2 C. V5 is placed in the 5 th Intercostal space D. V6 is placed in the mid axillary line 6
Leads I, II, III Leads avr, avl, avf 7
Right Leg Electrode RL electrode is connected to the electrical ground It does not participate in EKG acquisition You can attach it anywhere on the body Only problem is when it is accidently interchanged with another electrode AXIS Normal axis between 30 to 90 degrees in the frontal plane 8
Depolarization travelling towards the + electrode is recorded as a positive or upright deflection on that lead on the EKG QRS Axis in the frontal plane Use the limb leads Look at lead I Look at lead avf - 9
What is the Axis? A. Normal Axis B. Left Axis Deviation C. Right Axis Deviation D. Extreme Axis Deviation What is the Axis? A. Normal Axis B. Left Axis Deviation C. Right Axis Deviation D. Extreme Axis Deviation 10
p wave axis Where is the p wave coming from? A. Low Left Atrium B. AV Node C. High Right Atrium D. None of the above 11
Where is the p wave coming from? A. Low Left Atrium B. AV Node C. High Right Atrium D. None of the above This patient has A. Ectopic Atrial Rhythm B. Right Axis Deviation C. Left Axis Deviation D. None of the above 12
Negative P and QRS waves in lead I avr and avl morphology exchanged Lead I and V5 V6 morphology different This patient has A. Ectopic Atrial Rhythm B. Right Axis Deviation C. Left Axis Deviation D. None of the above 13
Reversal Xr I II III AVR AVL AVF V1 V6 LA/RA I III II AVL AVR AVF Unchang ed LA+ RA- RL LL After RA LA Lead Interchange Reversal of the RA and LA cables Negative P and QRS waves in lead I avr and avl will be morphology will be exchanged Negative QRS complex in lead I in the presence of mainly positive QRS in leads V5 and V6 14
This patient has A. Right arm left arm electrode misplacement B. Right ventricular hypertrophy C. Abnormal Chest X - Ray RA LA Reversal vs Dextrocardia Lead reversal and dextrocardia look the same in limb leads Lead reversal has normal precordial wave forms QRS becomes progressively smaller mostly QS or rs in V3-V6 with dextrocardia Lead I and V6 are similar in morphology in dextrocardia 15
This patient has A. Right arm left arm electrode misplacement B. Right ventricular hypertrophy C. Abnormal Chest X - Ray V6 16
This EKG shows A. Anterior Wall MI B. Inferior Wall MI C. Lateral Wall MI D. Septal Wall MI E. None of the above Positive P and QRS in avr Inverted P QRS in II Reversal of avr and avf 17
Reversal Lead I II III AVR AVL AVF V1 V6 RA/LL III II I AVF AVL AVR Unchanged LL LA LII RL RA This EKG shows A. Anterior Wall MI B. Inferior Wall MI C. Lateral Wall MI D. Septal Wall MI E. None of the above 18
Right Arm Left Leg Exchange Positive P and QRS in avr Inverted P QRS in II Reversal of avr and avf ) This EKG shows A. Dextrocardia B. Right Arm Left Arm Reversal C. Right Arm Left Leg Reversal D. Right Arm Right Leg Reversal 19
Limb Lead Exchange with Right Leg (Neutral Terminal) Right leg used as ground or neutral terminal Both legs have a common connection with the torso and hence are at similar potentials Limb Lead Exchange with Right Leg (Neutral Terminal) If right leg changes with one of arm leads RL RA LA LL One of I, II or III will be a straight line ( little potential difference between the two legs) The culprit lead can be figured out depending on the straight line lead Other 2 leads will be identical or mirror images Two of the Unipolar Leads will look identical 20
RL Lead I RA LA Lead III LL Lead II (RA LL) straight line and at similar potentials RA must be connected to Right Leg Lead I (RA to LA) and Lead III ( LL to LA ) are mirror images avr and avf will be identical This EKG shows A. Dextrocardia B. Right Arm Left Arm Reversal C. Right Arm Left Leg Reversal D. Right Arm Right Leg Reversal 21
Let s solve the problem in this EKG Lead III with no potential difference LA and LL at same potential difference, so LA must be attached to Right Leg Lead I (RA to LA) and Lead 2 (RA to LL) will be similar avf ( Unipolar to LL) and avl (Unipolar to LA) similar ) This EKG shows RL and RA interchange LL and LA interchange Both of the above 22
RL LL Lead II Lead III RA LA Lead I RA-LA interchanged with RL and LL Lead I (RA LA) straight line and at similar potentials RA and LA must be connected to Right and Left Legs avr and avl will be identical Lead II (RA to LA) and Lead III ( LL to LA ) are identical ) This EKG shows RL and RA interchange LL and LA interchange Both of the above 23
The EKG shows Right Leg interchange Pericardial effusion Other 24
The EKG shows Right Leg interchange Pericardial effusion Other This EKG shows A. Inferior Wall MI B. Lateral Wall MI C. Anterior Wall MI D. Septal Wall MI E. None of the above 25
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Confirm by comparing with old EKG This EKG shows A. Inferior Wall MI B. Lateral Wall MI C. Anterior Wall MI D. Septal Wall MI E. None of the above 27
Summary Faulty EKG acquisition can lead to misdiagnosis Rate may be effected by paper speed QRS size can be changed by change in Voltage avr is helpful if RA interchange has occurred Right leg electrode interchange can be recognized by absent complexes in effected limb lead Pseudo infarct patterns can be secondary to lead misplacements Thank you. 28
The EKG shows A. Lead Reversal B. Ectopic Atrial Tachycardia C. Dextrocardia D. None of the above The EKG shows A. Lead Reversal B. Ectopic Atrial Tachycardia C. Dextrocardia D. None of the above azamshafquat@gmail.com 29
Reversal Lead I II III AVR AVL AVF V1 V6 LA/RA I III II AVL AVR AVF LA/LL II I III AVR AVF AVL RA/LL III II I AVF AVL AVR Unchang ed Unchang ed Unchang ed To assess -30 to 0 QRS Axis in the frontal plane Use the limb leads Look at lead I Look at lead II II - 30
Q Wave The first negative deflection of a QRS complex before a positive deflection Q waves denote an area of infarcted or necrosed tissue 31
Q waves Q waves Presence of any Q waves abnormal in V1-3. In all other leads small q waves may be present (except lead III) Q wave in lead III may be normal EKG diagnosis of Old MI QS complexes Abnormal Q waves Reduction in R wave height ESP if old EKG showed normal R wave progression 32
Infarct Localization Inferior Wall MI II, III, avr Septal Wall MI V1, V2 Anterior Wall MI V3, V4 Lateral Wall MI I, avl, V5, V6 33