ECGs + Conduction problems

Question 1

Describe what leads would show ST elevation for anterior, lateral, inferior MI + what artery would be implicated?

Answer 1

Anterior/Septal leads

• V1-4
• LAD

Lateral leads

• I, aVL, V5, V6
• LCX or LAD

Inferior leads

• II, III, aVF
• RCA [RMA] and/or LCX

Question 2

Describe the difference between 1st, 2nd, 3rd degree heart blocks

Answer 2

(1.) 1st degree - indicated on an ECG by a prolonged PR interval. no missed beats.

(2. ) Mobitz I second degree AV block
- progressive prolongation of PR interval followed by a dropped QRS complex

(3. ) Mobitz type II second degree AV block
- normal PR interval with dropped QRS beat too

(4. ) 3rd degree heart block
- complete absence of AV conduction
- no relationship between P and QRS complex

Question 3

What is a bundle branch block?

What would you seen in an ECG for a LBBB and RBBB?

Answer 3

(1. ) Condition where there is a delay or blockage in electrical impulses pathway.
(2. ) Damage/blockage to these pathways can arise from Myocardial infarction, ischaemia, SA node disease etc. This causes an alteration in the depolarisation of the ventricles.
(3. ) LBBB = W in V1 (WiLLiaM) + M in V6
(4. ) RBBB = M in V1, W in V6 (MaRRoW)

Note: it w and m notches aren’t clear look in other chest leads such as V3.

Question 4

RF for LBBB and RBBB?

Answer 4

(1. ) LBBB: Dilated Cardiomyopathy, LVH, HTN
(2. ) RBBB: Thin tall young people, PE
(3. ) MI Myocarditis

Question 5

What would you seen in an ECG for atrial flutter

Answer 5

• ‘Sawtooth pattern’ in lead II, III, aVF

Question 6

Causes of AF?

Answer 6

(1. ) CAD
(2. ) HTN
(3. ) Valvular heart disease
(4. ) Hypothyroidism

Question 7

Symptoms of AF? (4)

Answer 7

• Breathlessness/dyspnoea
• Palpitations
• Syncope/dizziness
• Chest discomfort

Question 8

Mx of AF

Answer 8

(1. ) CHA2DS2-Vasc
- Stroke risk assessed for pts w/ nonvalvular AF
- if >2 give anticoag

(2. ) Rate Control: BB or CCB
- if fails consider digoxin, then amiodarone

(3. ) Rhythm control: Cardioversion
- this is 1st line if acute + pt is haemodynamically unstable (inc RR, chest pain, hypotension, oedema) +/- amiodarone
- if refractory consider ablation

(4. ) Investigate underlying cause
- usually due to an inferior MI (RCA occlusion) -> carry out Ix for MI: tropnins, PCI Mx.

Question 9

Describe what you’d see on an ECG for AF?

Answer 9

AF is an example of a SVT

(1. ) Absence of P waves
(2. ) Fibrillation in V1
(3. ) R-R interval is irregularly irregular
(4. ) QRS complex is narrow and irregular

Question 10

What is paroxysmal AF?

Answer 10

spontaneous termination within 7 days - although this commonly occurs within 48hrs.

Question 11

Describe the lead placement in an ECG

Answer 11

• V1 = right sternal edge, 4th ICS
• V2 = left sternal edge, 4th ICS
• V3 = halfway between V2 and V4
• V4 = 5th ICS in midclavicular line.
• V5 = anterior axillary line
• V6 = mid-axillary line

Question 12

What are the types of arrhythmias are there?

Answer 12

(1. ) Tachycardia >100bpm
- This can be further subdivided into SVT (above ventricles) or ventricular
- SVT e.g. AF, flutter, sinus tachy
- Ventricular e.g. ventricular tachycardia, ventricular fibrillation

(2. ) Bradycardia <60bpm
- e.g. heart blocks, sinus bradycardia)

Question 13

What would you seen in an ECG for a SVT condition

Answer 13

(1. ) Narrow QRS complex tacchycardia

(2. ) Ddx = AF, atrial flutter, sinus tachycardia, SVT

Question 14

How would you manage a Sinus tachycardia?

Answer 14

(1. ) Treat underlying cause

(2. ) Give fluids as hypovolaemia usually causes s.tacy

Question 15

How would you manage a pt where they’ve had or been given too much BB, CCB, digoxin?

Answer 15

(1. ) Glucagon for BB
(2. ) Ca for CCB
(3. ) Digibond for digoxin

Question 16

Management of heart block

Answer 16

This is for symptomatic HB such as mobitz type 2, third degree heart block

(1. ) Atropine (dec PNS) which helps inc HR
(2. ) Epinephrine (inc SNS)
(3. ) Pacing

Question 17

What are the four groups of antiarrhythmics drugs?

Answer 17

• class I, Na-channel blockers;
• class II, beta-blockers
• class III, K-channel blockers
• class IV, Ca-channel blockers; and miscellaneous antiarrhythmics

Question 18

How do Na channel blockers work as anti-arrhythmics?

Answer 18

slows HR by slowing depolarization, reducing cell excitability, and reducing conduction velocity.

Question 19

How do beta-blockers work? When is it CI?

Answer 19

(1. ) They act on beta-adrenergic receptors found in the heart (B1) and smooth muscles of vessels (B2). Activation of beta-R (via NA or Epi) causes a Ca influx into cells via L-type channels.
(2. ) B-blockers prevent this from happening, thus dec HR.
(3. ) CI = in pts on CCB, asthma

Question 20

How do K-channel blockers work as anti-arrhythmics?

Answer 20

(1. ) K channels blockers causes less K to leave the cells, this reduces the rate of repolarisation.
(2. ) This prolongs AP and thus prolongs the refractory periods (where cell is unexcitable by new stimulus). So less likely to generate an AP.
(3. ) Longer repolarization prevents the fast conduction of AP throughout the heart, which eventually leads to a slower HR.
(4. ) Amiodarone is an example

Question 21

How do CCB work and what are the two types and their uses?

Answer 21

(1.) CCB inhibit L-type Ca channels.

(2. ) The two groups are:
- Dihydropyridines: these are not antiarrhythmics and are selective for vascular smooth muscle and are used for HTN (e.g. amlodipine)

• Non-dihydropyridines: these are used to target myocytes (e.g. verapamil)

Question 22

How does digoxin work

Answer 22

(1. ) Mimics the effect of the vagal nerve i.e. dec HR

(2. ) H/E digoxin has a narrow therapeutic window and an overdose could cause arrhythmias

Question 23

Effect of hi and low K on ECG

Answer 23

(1. ) Hyperkalaemia:
- Tall T waves
- flattening of P waves
- broadening of QRS eventually ‘sine wave pattern’

(2. ) Hypokalaemia:
- Flattening of T wave
- QT prolongation

Question 24

Effect of hi and low Ca on ECG

Answer 24

• Hypercalcaemia: QT shortening

- Hypocalcaemia: QT prolongation

Question 25

Steps to ECG interpreting?

Answer 25

(1. ) Rate
(2. ) Rhythm
(3. ) Axis
(4. ) P, PR, QRS, ST, QT

Question 26

Mx of SVT

Answer 26

Stable pt (i.e. no shock, syncopes, HF, MI)

(1. ) Valsvular movement e.g. blowing into syringe
(2. ) If fails consider IV adenosine
- this is CI in asthma
- consider BB or CCB

Unstable

(1. ) Synchronised DC shock
(2. ) IV amiodarone

Question 27

When would use ECG in your IX?

Answer 27

(1. ) Chest pain
- Acute MI, pericarditis, PE
(2. ) Palpitations
(3. ) Breathlessness
- HF, LBBB, previous MI
(4. ) Blackout

Question 28

Describe which part of the ECG represents the following:

(1. ) Ventricular repolarisation
(2. ) Atrial depolarisation
(3. ) Ventricular depolarisation of <120ms
(4. ) Normal duration of 120-200ms
(5. ) Assesses activity within lateral myocardial territory
(6. ) Assesses activity within inferior myocardial territory
(7. ) Yields complexes that are normally inverted compared to the anterior and inferior leads

Answer 28

(1. ) T-wave
(2. ) P-wave
(3. ) QRS complex
(4. ) PR-interval
(5. ) Leads I, avL, V5, 6
(6. ) Leads II, III, aVF
(7. ) aVR