ECG Abnormalities

Question 1

Possible P-wave morphologies

Answer 1

P mitrale, P pulmonale, P-wave inversion

Question 2

P Mitrale

Answer 2

Prolonged P-wave with a notched appearance like bunny ears. Double P-wave. Indicates LA enlargement as LA depolarisation takes longer (seen in mitral stenosis).

Question 3

P Pulmonale

Answer 3

Peaked P-wave seen with RA enlargement as RA depolarisation takes longer (seen in pulmonary HTN).

Question 4

P-wave inversion

Answer 4

Inverted P-waves seen in non-inferior leads in ectopic atrial rhythms and junctional rhythms

Question 5

Absent P-waves

Answer 5

Non-sinus rhythm
Can indicate A-fib
Junctional rhythm (impulse at AV node bypasses atria, can also occur after QRS if retrograde conduction occurs)
VT
Hyperkalaemia (elevated potassium levels suppress atrial activity)
Sinus arrest / SSS

Question 6

PR interval abnormalities

Answer 6

Prolonged, shortened, varied

Question 7

Prolonged PR interval

Answer 7

> 200ms
May indicate 1st degree AV block or ectopic beats (rhythm may be originating in atria far from AV node)

Question 8

Shortened PR interval

Answer 8

<120ms
May indicate junctional rhythms (rhythm originates in/beside AV junction) or pre-excitation syndromes from accessory pathway (AVRT - WPW)

Question 9

Varied PR interval

Answer 9

Could be ectopic atrial beats depending where focus is located and how long it takes to travel through atria to AV node, or 2nd degree or 3rd degree AV blocks, or pericarditis (PR- and ST-depression and -elevation in different leads)

Question 10

Possible QRS abnormalities

Answer 10

Broad, narrow, low voltage/amplitude, high voltage/amplitude, abnormal Q-waves

Question 11

Broad QRS

Answer 11

> 120ms due to impulse not entering Purkinje system so cell-to-cell depolarisation takes longer
May be due to aberrant conduction of supraventricular complexes (SVT, WPW) or may be ventricular origin (VT, PVCs, BBB)

Question 12

Narrow QRS

Answer 12

<120ms and indicates a normal functioning conduction system
If there are no symptoms and normal P-wave and PR interval morphology, it is overall completely normal
Associated tachy or brady with abnormal P-waves and PR intervals can indicate supraventricular arrhythmias (SVT, AF, AT, flutter, AVRT, AVNRT, junctional rhythm, PACs)

Question 13

High amplitude/voltage QRS

Answer 13

Increased electrical activity in ventricles, can be caused by:
RVH/LVH, increased myocardial mass like athlete’s heart or obesity, BBB, ventricular enlargement (dilated cardiomyopathy), hyperkalaemia, VT, pre-excitation syndromes (WPW)

Question 14

Low amplitude/voltage QRS

Answer 14

Extracardiac causes (obesity, pericardial effusion, pleural effusion, pneumothorax) and cardiac causes (infection, myocarditis, end-stage HF)

Question 15

ST-segment abnormalities

Answer 15

Elevation or depression

Question 16

ST-Elevation

Answer 16

> 2 small boxes in precordial leads or >1 small box in limb leads = STEMI
Infarction is localised based on lead locations (anterior/posterior/lateral MI)
Reciprocal ST-Depression in electrically opposite leads
Also seen in LVH / LBBB / Brugada

Question 17

ST-Depression

Answer 17

Diagnostic of myocardial ischaemia (NSTEMI)
Upslope / downslope / horizontal depression
Seen in varied leads - cannot localise ischaemia
Also seen in LVH / RVH / LBBB / RBBB / SVT

Question 18

Signs of Pericarditis

Answer 18

ST-elevation with PR-depression in all leads except V1 and aVR (ST-depression with PR-elevation)