ECG Flashcards
A selection of cardiology questions focused around the ECG.
what is an electrocardiogram?
a graphical representation of the electrical activity of the heart
10 electrodes, 12 traces obtained
which leads are bipolar and orientated in the coronal plane?
standard leads I, II, and III
which leads are unipolar and orientated in the coronal plane?
augmented leads aVR, aVF, aVL
which leads are unipolar and orientated in the horizontal plane?
V1 to V6
bipolar leads =
utilise a single positive and a single negative electrode between which electrical potentials are measured
unipolar leads =
single positive recording electrode and utilise a combination of the other electrodes to serve as a composite negative electrode
Eindhoven’s triangle
aVR, aVL, aVF readings made from signals from leads I, II, and III
P wave
atrial depolarisation
QRS complex
ventricular depolarisation
T wave
ventricular repolarisation
duration of PR interval
120-200ms
3-5 small squares
duration of QRS
80-120ms
2-3 small squares
duration of QT
350-450ms
how do you calculate QTc
QTC = QT / √ RR
duration of QTc
<350ms is short
for men, >440ms is long
for women, >480ms is long
what is the direction of travel of electrical impulses in the heart?
SA node → AV node → Bundle of His → Bundle branches → Purkinje fibres
ECG territories: which leads are lateral?
lead I, aVL, V5, V6
ECG territories: which leads are inferior?
lead II, lead III, aVF
ECG territories: which leads are septal?
V1, V2
ECG territories: which leads are anterior?
V3, V4
how to calculate heart rate from ECG?
if heart beat is regular, 300 divided by no. of big squares between QRS complexes
if heart beat is irregular, number of QRS complexes on rhythm strip multiplied by 6
types of irregular heart rhythm
regularly irregular
irregularly irregular
what causes right axis deviation?
right ventricular hypertrophy
what causes left axis deviation?
conduction defects
left axis deviation on ECG
Look at Leads I, II, aVF.
Left Axis Deviation =
Leaving each other
right axis deviation on ECG
Look at Leads I, II, aVF.
Right Axis Deviation =
Reaching towards each other
no p waves?
atrial fibrillation
no QRS complex?
heartblock
sawtooth baseline is a sign of
atrial flutter
chaotic baseline is a sign of
atrial fibrillation
left atrium enlargement on ECG
P mitrale
right atrium enlargement on ECG
P pulmonale (tall P wave)
what does prolonged PR interval suggest?
AV block
ECG sign of first degree heart block
fixed prolonged PR interval
ECG sign of second degree heart block
Mobitz type 1: PR interval increases then dropped beat
Mobitz type 2: PR interval fixed with dropped beats (2:1, 3:1, 4:1)
ECG sign of third degree heart block
complete heart block OR AV dissociation - no relation between P waves and QRS
what can torsades de pointes develop into?
outline looks like a party streamer
ventricular fibrillation
management of ventricular fibrillation
Oxygen, IV access, Cardiac monitor, ECG
Drugs: Amiodarone
Electricity: DC Cardioversion
management of torsades de pointes
IV magnesium sulfate
Stop drugs causing prolonged QTc
examples of narrow complex tachycardia
Atrial Fibrillation Atrial Flutter Re-entry (AVRT or AVNRT) Atrial Tachycardia Multifocal Atrial Tachycardia
SVT treatment
Vagal manouevres (e.g. Valsalva, carotid sinus massage, head in ice-cold water)
Adenosine
DC Cardioversion
AF or Flutter: Beta blockers, amiodarone or digoxin. (Rate + rhythm control)
Rate control prophylaxis thereafter +/- catheter ablation
treatment of bradycardia
atropine
pacemaker
treatment of tachycardia
adenosine, amiodarone, beta blockers, verapamil, digoxin
DC cardioversion
ECG sign for pericarditis
widespread concave ST elevation (or saddle-shaped)
causes of ST depression
Ischaemia – horizontal or downsloping ST-depression, de Winter’s sign
Digoxin – generalised ST depression with curved ST segment
Hypokalaemia – typically <0.5mm
Heart Failure – may be seen in left lateral leads (I, aVL, V5, V6)
SVTs – typically V5, V6
Physiologial – seen during exercise
Secondary ST Depression LVH or RVH LBBB or RBBB Pre-excitation Pacemaker stimulation in left ventricle
sign of hyperkalaemia on ECG
tall T waves
T wave inversion may be a sign of:
previous episode of ischaemia
acute ischaemia
cerebrovascular insult
hypertrophic cardiomyopathy
causes of prolonged QTc
Drugs – Antipsychotics, Tricyclic antidepressants, chloroquine, hydroxychloroquine, quinine, macrolides, some anti-arrythmics. Hypokalaemia Hypomagnesaemia Hypocalcaemia MI Hypothermia Raised intra-cranial pressure Congenital Long QT syndrome
what does a delta wave indicate?
Wolff-Parkinson-White syndrome
