ECG interpretation Flashcards
Which way does an ECG spike when a signal is moving towards a recording electrode?
Upwards
What should the patient’s position be when undergoing an ECG?
Lying down 30-40˚
Where should V1 be placed?
4th right intercostal space, sternal angle
Where should V2 be placed?
4 left intercostal space, sternal angle
Where should V4 be placed?
5th left intercostal space
Where should V6 be placed?
Mid-axillary line, same level as V4
What is the order in which an ECG should be interpreted?
- Name, DOB, date and time of ECG
- Calibration
- Rate
- Rhythm
- Axis
- P wave
- PR interval
- QRS complex
- ST segment
- T waves
What’s the usual calibration of an ECG?
25 mm/sec
How is heart rate calculated?
300/number of large squares between beats
What does the PR interval represent?
The delay created by the AV node
What is a normal PR interval?
120-200 ms
2-5 small squares
What does the QRS complex represent?
Ventricular depolarisation
What is a normal QRS complex length?
<120 ms
3 small squares
What is QRS complex elongation caused by?
Aberrant conduction or ventricular origin
What does a P wave represent?
Atrial depolarisation
What is a normal P wave?
<2.5mm in height
<3mm in width
What does a T wave represent?
Ventricular repolarisation
What is a normal T wave?
Normally same directions QRS and no more than 1/2 QRS height
What is sinus rhythm?
Normal rhythm where heart is controlled by SA node
What is sinus arrhythmia?
Sinus rhythm but heart rate is irregular
What is the origin of supraventricular arrhythmias?
Within or above the ACnode
What is happening in atrial fibrillation?
Atria are in fibrillation, only some of the SA impulses arrive in the AVN
What are features of AF on an ECG?
Absent P waves
Irregularly irregular
Ragged baseline
Ventricular rate 30-200bpm
What is there a risk of in AF?
Embolic stroke
What are features of atrial flutter on an ECG?
Narrow complex tachycardia
Atrial rate of approx. 300bpm
Sawtooth baseline
What is Wolf-Parkinson-White syndrome?
Arrhythmia with an accessory AV pathway which does not have AVN delay.
This causes pre-excitation and upscoping of the QRS (delta wave)
What are features of supraventricular ectopic arrhythmia on ECG?
Varying PR and RR interval
Why do ventricular arrhythmias have broad QRS complexes?
Excitation spreads slower moving through normal myocardium than through the regular conduction system
What arrest rhythms are shockable?
Ventricular tachycardia or fibrillation
For which arrest rhythms would you do CPR?
Pulseless electrical activity, asystole
What causes ventricular tachycardia?
Damaged heart muscle formed scar tissue, creating abnormal (re-entrant) electrical pathways
What is the difference between monomorphic and polymorphic ventricular tachycardia?
Monomorphic - tachycardia coming from a single focus
Polymorphic - tachycardia coming from multiple foci
What are the features of monomorphic ventricular tachycardia on an ECG?
Regular broad complex tachycardia
What are the features of polymorphic ventricular tachycardia on an ECG?
Long QT
Torsade de Pointes (arctic monkeys cover type pattern)
What is happening in ventricular fibrillation?
Ventricles fibrillate (contract at rates of up to 500bpm), renders heart incapable of synchronised beat
What are features of ventricular fibrillation on ECG?
Irregular random baseline with no discernible waveform
Which leads most detect a lateral MI?
1, aVL, V5, V6
Which leads most detect an anterior MI?
V1-4
Which leads most detect an inferior MI?
II, III, aVF
What are features of ischaemia on ECG?
T waves: tall, biphasic, inverted, flattened
ST depression
What is classed as ST elevation?
ST elevation in 2 contiguous limb (>1mm) or chest (>2mm) leads
What are features of NSTEMI on ECG?
Transient ST elevation
ST depression
New T-wave inversion
What is heart block?
Block in conduction between atria and ventricles due to AV node dysfunction
What is first degree heart block?
PR interval >2s, no progressive lengthening, stable rhythm
What is second degree heart block Mobitz I?
Progressive PR elongation with eventual missed beat
What is second degree heart block Mobitz II?
Constant PR interval, every 2nd p-wave (approximately) missing QRS
What is third degree/complete heart block?
No p-wave and QRS relationship, broad QRS
What is bundle branch block?
Block in one of the 2 main branches coming off the Bundle of His
What does bundle branch block look like?
WILLIAM MARROW
- LBBB: V1 = W, V6 = M
- RBBB: V1 = M, V6 = W
