CVD - Basic ECG

Question 1

What are some additional lead placements in ECG? What are the indications?

Answer 1

• Right ventricular leads V4R-V6R: if suspecting right ventricular infarction
• Posterior leads V7-9: if suspecting posterior ischaemia

Question 2

What is a systemic ECG interpretation (order of things)?

Answer 2

• Rhythm and rate
• Cardiac axis
• PR interval
• QRS complexes
• ST segments and T waves
• QT interval

Question 3

What is the ratio of p waves to QRS in normal sinus rhythm?

Answer 3

1:1 ratio

Question 4

How do Premature atrial complexes (“atrial ectopics” look like on ECG?

Answer 4

early, narrow complex QRS followed by compensatory pause

Question 5

How do Premature ventricular complexes (“ventricular ectopics”) look like on ECG?

Answer 5

early, broad complex QRS

Question 6

How does Atrial fibrillation look like on ECG?

Answer 6

absence of p waves, irregularly irregular rhythm

Need to comment on ventricular response rate

> 100 – “rapid ventricular response rate”

Question 7

How does Atrial flutter look like on ECG?

Answer 7

“saw tooth” appearance of p waves due to large re-entrant pathway in atrium, REGULAR 300bpm

Question 8

How do you pick left axis/right axis deviation on ECG?

Answer 8

Look at Lead I & II/aVF.

1. Normal axis: positive, positive
2. Left axis dev: positive, negative (Ladies Adore Diamonds; in diamond shape)
3. Right axis dev: negative, positive (Rover Adores Digging; in the shape of dug bone edges. opposite of diamonds)

Question 9

When do you get left axis deviation?

Answer 9

• Left anterior hemiblock
• Ischaemic heart disease
• Cardiomyopathy
• Hypertension
• Wolff-Parkinson-White syndrome - right sided accessory pathway
• (NB LV hypertrophy is not a cause)

Question 10

When do you get right axis deviation?

Answer 10

• Normal finding in children and tall thin adults
• RV volume/pressure overload: RV hypertrophy, ASD, VSD, pulmonary embolus
• Lung pathology: COPD, PE
• Dextrocardia
• Wolff-Parkinson-White syndrome - left sided accessory pathway

Question 11

When do you get extreme right axis deviation?

Answer 11

• Lead transposition
• Ventricular tachycardia
• Emphysema
• Hyperkalaemia
• Paced rhythm

Question 12

What does atrioventricular dissociation indicate?

Answer 12

Complete heart block

Question 13

(3) types of abnormalities of the QRS complex you can see on ECG

Answer 13

–Voltages eg. increased in LV hypertrophy, decreased in cardiac amyloidosis
–Q waves
–Conduction eg. left or right bundle branch blocks

Question 14

How do you diagnose LVH on ECG “on voltage criteria”?

Answer 14

• Sum of S in V1/V2 & R in V5 or V6 (whichever is larger) ≥ 35 mm (7 large squares)
• or R in aVL ≥ 11 mm

NB: Echocardiography is a more accurate test for LV hypertrophy than ECG criteria alone

Question 15

What are pathological Q waves?

Answer 15

–marker of electrical silence which implies established full thickness death of myocardium i.e scar

– > 25% height of the corresponding R wave
(and/or > 40 msec width and > 2mm in depth)

–Present in more than 1 contiguous (adjacent) lead

Question 16

Classic morphology for LBBB on ECG

Answer 16

–“WilliaM” – W in V1(often not obvious) and M pattern in V6
–Inverted T waves lateral leads V5-V6, I, aVL
–No septal Q waves

Question 17

Classic morphology for RBBB on ECG

Answer 17

–“MarroW” – M (rSR’) pattern in V1 and W in V6
–Inverted T waves V2-V3
–Slurred S wave in V6

Question 18

(4) causes of ST segment changes

Answer 18

– Myocardial ischaemia/infarction
–Pericarditis (widespread ST segment elevation)
–LV hypertrophy with “strain” pattern (ST segment depression)
–Drugs eg. digoxin

Question 19

Inferior leads of ECG

Answer 19

II, III, aVF

Question 20

Lateral leads of ECG

Answer 20

High lateral: I, aVL

Lateral: V5-6

Question 21

Anteroseptal leads of ECG

Answer 21

V1-4

Question 22

Briefly discuss the progressino of acute ischaemic changes seen on ECG

Answer 22

1. ST elevation (a key sign of acute myocardial infarction requiring urgent treatment)

+/- T wave inversion (often persists long term)

2. Q waves: if full thickness infarction (previous infarction)

Question 23

How does pericarditis present on ECG?

Answer 23

Widespread saddle shaped ST elevation

Question 24

What does horizontal ST depression suggest?

Answer 24

significant myocardial ischaemia

Question 25

What is a “strain” pattern on ECG?

Answer 25

ST depression with T wave inversion

Question 26

(3) causes of T wave abnormalities

Answer 26

–Myocardial ischaemia
–LV hypertrophy/strain, digoxin effect
–Systemic issues eg. electrolyte imbalances (K+,Mg2+, Ca2+)

Question 27

What (2) morphologies of T waves are most useful in diagnosing MI?

Answer 27

Biphasic or inverted T waves

Question 28

Briefly describe Wolff-Parkinson White syndrome

• structural abnormality
• consequences
• (2) ECG changes

Answer 28

Accessory pathway bypasses atrioventricular node

• leads to earlier (pre)-excitation of the ventricle than would occur with conduction through normal pathway
• may lead to rapid regular tachycardias

ECG:

• Short PR interval
• Delta wave reflecting pre-excitation (early excitation) of the ventricle