12 Lead ECG interpretation Ischaemic Changes Work Shop Hayley Coxon
Topics covered Recap on ECG format and basics Normal ECG ECG changes in myocardial ischaemia/infarction ST segment T wave Q wave Acute MI locations and reciprocal changes Other causes of T wave and ST changes Practice ECGs
ECG Paper 1 large box = 0.2 seconds 5 large boxes = 1 second 10 mm/1mv Reference 1 small box = 0.04 seconds Time
P, QRS & T Wave Isoelectric line
Normal Intervals P-R interval: 0.12-0.20 sec (3 to 5 small squares) QRS width: 0.08-0.12 sec (2 to 3 small squares) PR interval QRS complex QT interval Q-T interval: 0.35-0.43 sec *The PR interval should really be referred to as the PQ interval, however it is commonly referred as the PR interval.
Lead Groups Limb Leads Chest Leads (precordial leads) Lead I avr V1 V4 Lead II avl V2 V5 Lead III avf V3 V6 Bipolar Unipolar Unipolar
Standard Bipolar Leads I II III - I + - Einthovens - Triangle II III + +
Augmented Unipolar Leads + + Augmented Voltage Right (avr) Augmented Voltage Left (avl) avr will always be negative if the limb leads are placed correctly + Augmented Voltage Foot (avf)
Limb leads -120-90 -60 Left axis -150 av R -30 av L +180 0 I +150 +-30 Right axis +120 III +90 av F +60 II
R Wave Progression 1 r 2 1 2 V6 2 R S V1 1 q V1 V2 V3 V4 V5 V6
12 Lead ECG Check List Remember Always treat the patient - not the ECG. 1. The PR interval is between 0.12 & 0.2 sec (3-5 small squares). 2. The QRS duration is <0.11 sec (<3 small squares). 3. The QRS complex should be predominantly upright in leads I & II. 4 QRS & T waves tend to have the same general direction in the limb leads. 1. Confirm that avr is negative (if not check limb lead placement). 2. The R wave in the precordial leads must grow from V1 to at least V4. 3. The ST segment should start isoelectric except in V1 & V2 where it may be slightly elevated. 4. The P waves should be upright in I, II & V2 to V6 5. There should be no Q waves > 0.04 seconds (1 small square) in width in I, II, V2 to V6. 10 The T wave must be upright in I, II, V2 to V6. Chamberlain DA. Personal communication
Normal 12 Lead ECG
ECG patterns of myocardial ischaemia and infarction ST segment depression/elevation T waves changes Hyperacute Inverted T waves Biphasic T waves Flattened T waves Pathological Q waves U-wave inversion less well-known
ST Segment
ST Segment 1 2 3
J Point J point - starting point when measuring ST segment deviation.
J Point Examples 1 2 3 4 5 6
T Wave
Hyperacute T waves Broad, asymmetrically peaked or hyperacute T-waves are seen in the early stages of STEMI
Inverted T waves
Biphasic T waves Myocardial ischaemia Waves go up then down
Flattened T waves Dynamic T-wave flattening due to anterior ischaemia (left) T waves return to normal once the ischaemia resolves (right)
Q Wave The septum depolarises from left to right
Q waves Represents the normal left-to-right depolarisation of the interventricular septum Small septal Q waves are typically seen in the left-sided leads (I, avl, V5 and V6) Small Q waves are normal in most leads Deeper Q waves (>2 mm) may be seen in leads III and avr as a normal variant Under normal circumstances, Q waves are not seen in the right-sided leads (V1-3)
Pathological Q Waves > 1 mm wide > 2 mm deep > 25% of depth of QRS complex Seen in leads V1-3
A normal 12-lead ECG DOES NOT rule out an acute myocardial infarction
Acute Myocardial Infarction ST elevation >2mm in V1-V3 and >1mm in all other leads in >2 contiguous leads 1. Myocardial injury presents as raised ST 1. Infarction can present as Q wave 1. I Lateral avr V1 Septal V4 Anterior II Inferior avl Lateral V2 Septal V5 Lateral III Inferior avf Inferior V3 Anterior V6 Lateral 1. The Task Force on the management of acute myocardial infarction of the European Society of Cardiology. Eur Heart J 2003;24:28-66
Evolution of an acute myocardial infarction A. B. C. Onset 15 Minutes > 1 Hour D. E. F. > 24 Hours Days Later Months later
Location of infarctions Septal AMI V1, V2 Anterior AMI V3, V4 Inferior AMI II, III, AVF Lateral AMI V5, V6 - (I, AVL)
Inferior AMI I II III II avr avl avf V1 V2 V3 V4 V5 V6 III avf II
Right Sided Chest Lead Placement Move the standard left chest leads to the right side in the same position V3R Directly between V1 & V4R. V4R Fifth intercostal space, midclavicular line. V5R Level with V4R at left anterior axillary line V6R Level with V5R at midaxillary line (midpoint of the armpit). V4R is the most sensitive indicator of a right ventricular infarction
RV Infarction (standard Leads)
RV Infarction (Right Sided Leads) V4R V5R V6R
Antero-septal AMI V1 V2 V3 V4 I II III avr avl avf V1 V2 V3 V4 V5 V6
V6 V5 V4 V3 V1 V2 Antero-lateral AMI I avr V1 V4 II I avl V2 V1 V5 V4 III avf V3 V6 V2 V5 avl I V3 V6
Lateral AMI avl I I II avr avl V1 V2 V4 V5 III avf V3 V6
Reciprocal Changes If a lead is looking directly at the infarct site it will produce ST segment elevation When a lead sees the infarct from the opposite perspective, the ST segment may become depressed in that lead II, III avf I, avl, V leads
Infarction Overview Site Indicative Leads Reciprocal Leads Inferior II, III & avf I & avl Septal V1 V2 None Anterior V3 V4 None Anteroseptal V1 V4 None Lateral I, avl & V5 - V6 II, III & avf Anterolateral I, avl & V3 V6 II, III & avf Posterior None V1 V4
? Posterior AMI V1-V4 Depression
Posterior - Lead Placement V1 - V3 are moved round to become V7 - V9. They are placed on the same horizontal plane as V4 V7 Posterior axillary line V8 Midscapular line in between V7 & V9 V9 To the left of the spine V4 V4 V7 V8 V9
Posterior ECG
Dynamic Changes in AMI Pre-hospital ECG showing possible hyperacute S-T changes in anterior leads
Dynamic Changes in AMI 2nd ECG taken 20mins later, showing established antero-lateral S-T elevation
Identify the following 6 ECG infarction sites
ECG 1
ECG 2
ECG 3
ECG 4
ECG 5
ECG 6
ECG 7
Other causes of ST Segment Elevation Pericarditis Benign early repolarization Left bundle branch block Left ventricular hypertrophy Ventricular aneurysm Brugada syndrome Ventricular paced rhythm Raised intracranial pressure
Pericarditis Benign early repolarisation LBBB LV Aneurysm Brugarda
Pericarditis
Benign early repolarisation
Raised Intracranial Pressure
Other reasons for inverted T waves Normal finding in children Persistent juvenile T wave pattern Bundle branch block Ventricular hypertrophy ( strain patterns) Pulmonary embolism Hypertrophic cardiomyopathy Raised intracranial pressure
LVH
Hypokalaemia Waves go down then up
Raised Intracranial Pressure
Thank you More practice ECGs?