ECG Interpretation Flashcards
What is the Flowchart for interpreting an ECG
- Right patient?
- Rate
- Sinus Rhythm?
- Cardiac Axis
- Assess P waves
- P-R Interval
- QRS Complex Width
- ST-elevation?
- T Wave inversion?
- Q Waves?
- QT Interval
Where is T wave inversion normal
In aVR, III, V1 and V2
What does T wave inversion represent
Ischemia (24-48 hours), Ventricular Hypertrophy, BBB, Digoxin
What may cause ST elevation
MI, Pericarditis
How do you differentiate ST elevation in an MI from Pericarditis
localised in MI, in most leads in pericarditis
What causes ST depression
Ischemia
What does bundle branch block cause
delayed depolarisation of ventricles, causing a wide QRS
Where is RBBB best seen
V1
Where is LBBB best seen
V6
What does RBBB look like
M shape in V1 OR Positive v1 + wide QRS
What does LBBB look like
Wide QRS + negative V1 OR M shape in V6/W shape in V1
What does asymptomatic LBBB indicate
Aortic Stenosis
What does (new) LBBB + chest pain indicate
Acute MI
What is the minimum requirement for ST elevation to be considered significant
> 2mm in a chest lead, >1mm in a limb lead, must be at least 2 leads to be significant
What causes Right axis deviation
Right ventricular hypertrophy
What most commonly causes left axis deviation
Conduction deficits
What does an axis deviation indicate
Not much if in isolation, although signs of RVH/LVH/Pulmonary embolus( in RAD)/conduction deficits should be investigated
What indicates right ventricular hypertrophy
Tall V1 R wave + Right axis deviation + V5/V6 having equal R + S waves
what indicates left ventricular hypertrophy
Tall V6 R wave (+ potentially left axis deviation)
Whats the height rule for R waves in V5/V6 and the s wave in V1
Combined height shouldn’t exceed 25mm (otherwise this indicates LVH)
What indicates 1st degree heart block
PR interval >220ms
What causes 1st degree heart block
Found in athletes commonly, coronary aa disease, acute rheumatic fever, electrolyte disturbance, digoxin toxicity
What are the 3 variations of 2nd degree heart block
Mobitz type 2 Wenkebache phenomenon (Mobitz type 1) 2:1/3:1/4:1 conduction
What is Mobitz type 2 heart block
constant P-R interval with occasional non conducted p waves
What is Mobitz type 1/Wenkebache heart block
Gradually lengthening P-R interval until a non conducted beat and repeat
What is 3rd degree heart block
atrial contraction + ventricle contraction independent of eachother
What does 3rd degree heart block indicate
MI/Chronic tissue disease, Pacing required
What is sinus bradycardia associated with
athletic training, fainting, hypothermia, hypothyroidism, post MI
What is sinus tachycardia associated with
exercise, fear, pain, haemorrhage or thyrotoxicosis
Where are the 3 places non-sinus rhythms can originate from
Atrial muscle, Ventricular muscle, AVN
What does a non sinus atrial rhythm look like
abnormal p waves
What does a non sinus ventricular rhythm look like
wide/abnormal QRS complexes
What does a non sinus AVN rhythm look like
no p wave
How fast does the AVN depolarise
50 bpm
What is the rough speed of an excape rhythm
30bpm
How do you manage bradycardia
Treat reversible causes
asses for adverse factors (shock, syncope, heart failure, MI, recent asystole, mobitz type 2, type 3 heart block)
if non present monitor
if some present 500mcg IV atropine (up to 3g) + pacing if necessary
What needs to be identified to be able to say an ECG is showing a tachycardic rhythm
P waves
Whats the speed of atrial tachycardia
100-200bpm
What is the maximum conduction speed of the AV node
200bpm
When should Atrial fibrillation be treated
if the rhythm is irregular
What should you do if there is atrial fibrillation at a regular rate
attempt vagal manouvers (carotid sinus massage, valsava manover)
If unsuccessful Adenosine 6mg (12mg if ineffective, verapimil in asthma)
Last resort cardioversion
What does ventricular tachycardia look like
wide QRS in all 12 leads
Why is ventricular tachycardia dangerous
may progress to ventricular fibrillation
When does ventricular tachycardia require cardioversion
<90mmHg systolic
Chest pain
Heart failure
Rate >150
If no abnormal features are present how do you treat ventricular tachycardia
amiodarone 300mg
Cardioversion if this fails
What does ventricular fibrillation look like on an ECG
No QRS, disorganised
What does atrial fibrillation look like on an ECG
Irregular baseline with no p waves , 450-600 bpm, normal QRS
if AF is suspected but not seen on an ECG what should be the next line of investigation
24-hour ambulatory ecg monitoring
what is the treatment cascade for fibrillation
Symptomatic or haemodynamically unstable = immediate cardioversion
Haemodynamically stable = rate/rhythm control (beta blocker or rate limiting Ca2+ inhibitor) + anticoagulation (aspirin if low risk of stroke via CHADVASC, warfarin if medium-high risk, aspirin + clopidogrel if warfari is CI)
What does atrial flutter look like
Saw tooth baseline, 300-450bpm , similar to AF but baseline looks regularly irregular as opposed to AF where it looks irregularly irregular
What does hyperkalaemia look like on an ECG
tall ‘tented’ t waves, wide QRS, prolonged PR interbal
What does hypokalaemia look like on an ECG
T wave flattening, V wave at the end of T wave
V wave = larger wider t wave
What does hypercalcaemia look like on an ECG
QT shortening
What does hypocalcaemia look like on an ECG
QT lengthening
What is wolf-parkinson-white syndrome + what does it look like on an ecg
There is an additional conducting bundle alongside the bundle of his, unconnected to the AVN, causing spontaneous paroxysmal tachycardia
ECG shows a delta wave (lengthening of the proximal part of the QRS complex due to pre-excitation of the accessory bundle)
What region/artery is represented in lead 1
Lateral region, supplied by the circumflex artery
What region/artery is represented in Lead 2
Inferior region, supplied by the right coronary artery
What region/artery is represented in Lead 3
Inferior region, supplied by the right coronary artery
What region/artery is represented in aVL
Lateral (no artery)
What region/artery is represented in aVF
Inferior region, supplied by the right coronary artery
What region/artery is represented in V1
Septal region, supplied by the left anterior descending artery
What region/artery is represented in V2
Septal region, supplied by the left anterior descending artery
What region/artery is represented in V3
Anterior region, supplied by the left anterior descending artery
What region/artery is represented in V4
Anterior region, supplied by the left anterior descending artery
What region/artery is represented in V5
Lateral region, supplied by the circumflex artery
What region/artery is represented in V6
Lateral region, supplied by the circumflex artery
What do p waves look like in right atrial hypertrophy
peaked
What do p waves look like in left atrial hypertrophy
notched and broad
what do deep Q waves indicate
previous infarction
where are deep Q waves normal
Leads I, aVL, V5 + V6
What is a normal QT interval
<0.45 seconds
What is the minimum for a wide QRS
> 120ms
How big and how much time does a small square on the ECG paper represent
1mm, 0.04 seconds (40ms)