ECGs

Question 1

Which leads show anterior pathology?

Answer 1

V1-V4 = Left Anterior Descending (LAD)
V1&V2 = Septal

Question 2

Which leads show lateral pathology?

Answer 2

V5, V6, I, aVL = Circumflex

Question 3

Which leads show inferior pathology?

Answer 3

II, III, aVF = Right Coronary Artery (RCA)

Question 4

What is shown with a normal axis?

Answer 4

leads I, II, and III positive (II most positive)

Question 5

What is shown with right axis deviation?

Answer 5

QRS is positive (dominant R wave) in leads III and aVF

QRS is negative (dominant S wave) in leads I and aVL

Causes:

Left posterior fascicular block

Lateral MI

Right ventricular hypertrophy

Acute Lung Disease (PE)

Chronic Lung Disease (COPD)

Ventricular Ectopy

WPW Syndrome

Hyperkalaemia

Horizontally positioned heart

Septal Defects

Question 6

What is shown with left axis deviation?

Answer 6

QRS is positive (dominant R wave) in leads I and aVL

QRS is negative (dominant S wave) in leads II and aVF

Causes:

Left anterior fascicular block

LBBB

Left ventricular hypertrophy

Inferior MI

Ventricular ectopy

Pacing

WPW syndrome

Question 7

What is the regular PR interval?

Answer 7

Normal 120-200ms

3-5 small squares

Prolongation suggests heart block, hypokalaemia, acute rheumatic fever

Shortening with upsweeping Q wave indicative of WPW

Question 8

What is the regular QRS complex width?

Answer 8

<120ms

3 small squares

Wide suggests ventricular origin

Narrow suggests supraventricular origin

Question 9

Reporting an ECG

Answer 9

Patient Name

Date of ECG

Rate (# of beats)

Rhythm (regular/irregular)

Axis

P wave (presence, amplitude)

PR interval (normal, shortened, widened)

QRS complex (presence, size)

ST segment

T waves (presence, inversion)

QT interval (elongated)

Other: LBBB, RBBB, pacing, ectopics, Q waves

Question 10

Sinus Rhythm

Answer 10

each QRS complex is preceded by a P wave

Question 11

Bradycardia vs Tachycardia

Answer 11

<60 = brady

>100 = tachy

Question 12

Escape Rates

Answer 12

Atrial: 60-80bpm

Junctional: 40-60bpm

Ventricular: 20-40bpm

Question 13

First Degree Heart Block

Answer 13

PR interval widened (P waves may be burried in T wave)

Question 14

Right Bundle Branch Block

Answer 14

MaRRoW (M in V1, W in V2)

Broad QRS > 120ms

Typical RSR’ pattern in V1-3

Wide slurred S wave in I, aVL, V5-6

NB: Delayed activation of the right ventricle also gives rise to secondary repolarization abnormalities, with ST depression and T wave inversion in the right precordial leads.

Question 15

Left Bundle Branch Block

Answer 15

WiLLiaM (W in V1, M in V2)

QRS duration > 120ms

Dominant S wave in V1

Broad monophasic R wave in I, aVL, V5-6

Absence of Q waves in lateral leads

LBBB can mask ECG signs of MI

Question 16

Second Degree Heart Block (Mobitz I)

Answer 16

Progressive prolongation of PR interval culminating in non-conducted P wave

Question 17

Second Degree Heart Block (Mobitz II)

Answer 17

Intermittent non-conducted P waves without progressive prolongation of the PR interval

Question 18

Third Degree Heart Block

Answer 18

Atrial rate is approximately 100bpm

Ventricular rate is approximately 40bpm

Perfusing rhythm is maintained by Junctional or Ventricular escape rhythm

Question 19

Atrial Flutter

Answer 19

Serrated / saw-toothed P waves

May show alternating pattern of 2:1, 3:1, 4:1 conduction ratios

250-350bpm

Question 20

Atrial Fibrillation

Answer 20

Irregularly irregular rhythm

no P waves

no isoelectric basline

>350bpm

Question 21

Wolff-Parkinson White

Answer 21

Delta waves - slurring slow rise of initial portion of QRS

Question 22

Ventricular Fibrillation

Answer 22

Chaotic irregular deflections of varying amplitude

No P waves, QRS complexes, or T waves identifiable

Fatal if not cardioverted

Question 23

Ventricular Ectopic Beats (Premature Ventricular Complex)

Answer 23

Premature broad QRS complex with abnormal morphology

ST segment discordant to QRS

bigeminy = frequent PVCs coupled with sinus rhythm

Question 24

Atrial Ectopic Beats (Premature Atrial Complex)

Answer 24

Abnormal P wave followed by normal QRS (P wave may be hidden in T wave)

Question 25

AV nodal (junctional) rhythm

Answer 25

Junctional rhythms are narrow complex, regular rhythms arising from the AV node. P waves are either absent or abnormal (e.g. inverted) with a short PR interval (=retrograde P waves).

Question 26

Hyperkalaemia

Answer 26

Peaked/ Tall T waves Loss of P wave Widening QRS (approaching sine wave)

Question 27

Ventricular Tachycarida

Answer 27

Wide QRS May degenerate to VF (fatal)

Question 28

Pulmonary Embolism

Answer 28

S1Q3T3 - prominent S wave in lead I - abnormal Q wave in lead III - T wave inversion in lead III

Question 29

Past MI

Answer 29

Q waves seen in leads V1-3 Inferior Q waves (II, III, aVF) May have T wave inversion

Question 30

Supraventricular Tachycardia

Answer 30

Similar to VT but has narrow QRS and possible evidence of P waves (although not sinus rhythm)

Question 31

Causes of Regular Rhythm Bradycardia

Answer 31

Physiological (athletes, during sleep: due to increased vagal tone) Drugs (e.g. beta-blockers, digoxin, amiodarone) Hypothyroidism (decreased sympathetic activity secondary to thyroid hormone deficiency) Hypothermia Raised intracranial pressure (due to an effect on central sympathetic outflow)—a late sign Third-degree atrioventricular (AV) block, or second-degree (type 2) AV block Myocardial infarction Paroxysmal bradycardia: vasovagal syncope Jaundice (in severe cases only, due to deposition of bilirubin in the conducting system)

Question 32

Causes of Irregular Rhythm Bradycardia

Answer 32

**Irregularly irregular** Atrial fibrillation (in combination with conduction system disease or AV nodal blocking drugs) due to: ● alcohol, post-thoracotomy, idiopathic ● mitral valve disease or any cause of left atrial enlargement Frequent ectopic beats **Regularly irregular rhythm** Sinus arrhythmia (normal slowing of the pulse with expiration) Second-degree AV block (type 1) Apparent Pulse deficit\* (atrial fibrillation, ventricular or atrial bigeminy)

Question 33

Causes of Regular Rhythm Tachycardia

Answer 33

Hyperdynamic circulation, due to: ● exercise or emotion (e.g. anxiety) ● fever (allow 15–20 beats per minute per °C above normal) ● pregnancy ● thyrotoxicosis ● anaemia ● arteriovenous fistula (e.g. Paget’s disease or hepatic failure) ● beri-beri (thiamine deficiency) Congestive cardiac failure Constrictive pericarditis Drugs (e.g. salbutamol and other sympathomimetics, atropine) Normal variant Denervated heart, e.g. diabetes (resting rate of 106–120 beats per minute) Hypovolaemic shock Supraventricular tachycardia (usually \>150) Atrial flutter with regular 2:1 AV block (usually 150) Ventricular tachycardia (often \>150) Sinus tachycardia, due to: ● thyrotoxicosis ● pulmonary embolism ● myocarditis ● myocardial ischaemia ● fever, acute hypoxia or hypercapnia (paroxysmal) Multifocal atrial tachycardia Atrial flutter with variable block

Question 34

Causes of Irregular Rhythm Tachycardia

Answer 34

Atrial fibrillation, due to: ● myocardial ischaemia ● mitral valve disease or any cause of left atrial enlargement ● thyrotoxicosis ● hypertensive heart disease ● sick sinus syndrome ● pulmonary embolism ● myocarditis ● fever, acute hypoxia or hypercapnia (paroxysmal) ● other: alcohol, post-thoracotomy, idiopathic Multifocal atrial tachycardia Atrial flutter with variable block

Question 35

What is the normal QT interval?

Answer 35

The QT interval should be aproxametly less than half the cardiac cycle A lengthened QT interval is a marker for the potential of ventricular tachyarrhythmias like torsades de pointes and a risk factor for sudden death.

Question 36

What is a delta wave

Answer 36

Early ventricular depolarisation typically due to Bundle of Kent activation pathway Seen in Wolff Parkinson White Syndrome

Question 37

CHADS2

Answer 37

Assessment Scale for Atrial Fibrillation and need for anticoagulants