ECGs: Everything a finalist needs to know Dr Amy Coulden As part of the Simply Finals series
Aims and objectives To be able to interpret basic ECG abnormalities To be able to recognise commonly tested ECGs in exams To be able to present an ECG as part of OSCE scenario To be able to set up an ECG as part of OSCE scenario
The ECG Atrial depolarisation Ventricular depolarisation Ventricular repolarisation SA node (right atrium) -> AV node -> Interventricular septum (bundle of His) -> Left and right bundle branches
Setting up the ECG- Chest leads V1- Right sternal border- 4 th IC space V2- Left sternal border, 4 th IC space V3- Half way between V2 and V4 V4- Left mid clavicular line, 5 th IC space V5- Half way between V4 and V6 V6- Left mid axillary line, horizontal to V4
Setting up the ECG- limb leads Don t forget to calibrate the machine 10mm/mV & 25mm/s Right arm- Red Left arm- YeLLow Right foot- Black Left foot- Green
Presenting an ECG 1. What? When? Who? Where? Why? An electrocardiogram dated 15 th January 2018 at 10:30 of Joe Bloggs, 52 years old performed in A&E with a presenting complaint of chest pain 2. Main abnormality (if apparent) 3. Structured approach - Rate - Rhythm - Axis - P waves/ PR interval - QRS complex - ST segment - T waves/ QT interval 4. Summary 5. Further investigation and management
Rate Rate= 300/ R-R interval 1 per every large square= 300 bpm 2 = 150 bpm 3 = 100 bpm 4 = 75 bpm 5 = 60 bpm 6 = 50 bpm HR >100- tachycardia HR < 60- bradycardia
Around 75-85 bpm What s the rate?
35 bpm What s the rate?
What s the rate? R waves x 6 ( bottom strip- II) = rate per minute Around 65bpm Around 150bpm Therefore rate = 17 x 6 = 102 bpm
Rhythm 2 questions - Regular or irregular? - If irregular - Regularly, irregular? i.e follows a pattern - Irregularly irregular? AF!
Rhythm Diagnosis? Sinus arrhythmia Irregular, P wave before every QRS, Regular PR interval, rate 40-60 Regular R-R interval, no P waves, rate around 200bpm, narrow complex Diagnosis? Supraventricular tachycardia Diagnosis? Fast atrial fibrillation Irregularly irregular, no P waves, tachycardia Regularly irregular, PR not increasing, regular dropped QRS Diagnosis? 2 nd Degree heart block, type II
Axis Left axis deviation Right axis deviation Normal axis -30 - +90
Axis deviation Look at leads I and avf (or III) Are they Leaving? (i.e. I is positive and avf (or III) is negative) Are they Reaching? (i.e I is negative and avf (or III) is positive) Look at lead II Look at lead II Is it negative? Is it positive or isoelectric? Is it negative? Is it positive or isoelec Left Axis Deviation Physiological LAD Right Axis Deviation
What s the axis? Normal axis
P waves P wave = Atrial depolarisation <3 small squares (120ms)
P waves P Mitrale- Left atrial enlargement P Pulmonale- Right atrial enlargement No P waves? Disorder/ absence of atrial contraction
What s the diagnosis Atrial flutter with 4:1 block
What s the diagnosis? Atrial fibrillation
PR interval Start of P to start of QRS complex <5 small squares (200ms)
AV nodal block PR interval >5 squares PR interval constant No dropped QRS 1 st degree heart block 2 nd degree heart block, type I (Wenckebach) PR interval >5 squares Increasing PR interval Followed by dropped ORS PR interval >5 squares Fixed PR interval Regular dropped QRS complexes 2 nd degree heart block, type II Complete heart block Complete dissociation between P waves and QRS complexes Widened QRS
QRS complex Ventricular depolarisation < 3 small squares (120ms)
Bundle branch block W i L L i a M Broad complex QRS (> 120ms) M a R R o W
LBBB or RBBB? RBBB
LBBB or RBBB? LBBB New onset LBBB can be a sign of acute ischaemia It is not possible to intepret the ST segment in LBBB
ST segment The period when the ventricles are polarised
Can you think of causes of ST Ischaemia Pericarditis Hyperkalaemia elevation? Ventricular aneurysm Brugada syndrome Normal variant (high take off) To name a few
ST elevation MI
Cardiac territories- MI SEPTAL Note: Posterior MI ST depression in anterior leads (V1-V2) - RCA or Left Cx
What s the diagnosis? What vessel is involved? Anterolateral MI with reciprocal depression LAD + Left Cx
Evolving ECG pre and post MI ST elevation T wave inversion Q wave
T wave Ventricular repolarisation
Tall tented T waves (Note- could also have prolonged PR and widened QRS) Diagnosis? Hyperkalaemia U have no Pot and no T, but a long PR and a long QT Inverted/ flattened T waves, U waves, long PR and long QT Diagnosis? Hypokalaemia Hyperacute, wide based T waves (also ST elevation) Diagnosis? Acute MI
Long QT Prolonged: > 450ms males, > 470ms females (Use QTc on print out) Can you name a few causes? Congenital CNS causes- stroke, intracerebral bleed Electrolyte disturbances (hypokalaemia, hypomagnesemia, hypocalcaemia) Drugs e.g. antipsychotics
Now let s practice Present this ECG to your neighbour
27 M BG: known antiphospholipid syndrome PC: pleuritic chest pain. Diagnosis? PE S1 Q3 T3 Other ECG findings consistent with PE? Sinus tachycardia, RBBB, RAD
72 F BG: IHD PC: Collapse Diagnosis? Trifascicular block RBBB LAD AV Block
25 F PMH: Nil PC: Palpitations Diagnosis? Supraventricular tachycardia Narrow complex QRS Tachycardia- rate 150 bpm No P waves
As opposed to Broad complex QRS Tachycardia No P waves Diagnosis? Ventricular tachycardia
32 M BG: Anxiety PC: Chest pain Diagnosis: Normal ECG
78M BG: IHD PC: OOH arrest Diagnosis? Ventricular fibrillation Fibrillating wide complexes Tachycardia
28 M BG: FHx of young cardiac arrest PC: Collapse Diagnosis? Brugada syndrome
Wide based QRS on it s own: ventricular ectopic Torsades de points: Polymorphic VT Sick sinus syndrome: Brady, tachy and tachybradycardias High take off: normal variant
Wolf Parkinson White (AVRT): Short PR, Wide QRS, delta wave Digoxin toxicity: reverse tick AVNRT (junctional tachycardia): Narrow complex QRS, no P waves, regular Pericarditis: Widespread ST elevation, PR depression
Any questions? THE END