ECGs

Question 1

What complex do you look at for BBB and how does it change?

Answer 1

QRS.

It becomes greater than 3 small squares 0.12s

Question 2

Causes of BBB?

Answer 2

Normal
pericarditis
myocarditis
congestive hf
congenital heart disease

Question 3

Which of the ECG leads look at which side and chamber of the heart?

Answer 3

Right atrium = aVR
Right ventricle; V1, V2
(thats why in a rbbb, you see positive deflection in v1 qrs)

Left atrium = aVF
Left ventricle = V3-V6
(lbbb +ve deflection in v6)

So if there is a left sided issue look at the associated leads

Question 4

What 3 characteristic signs would you see on ECG for RBBB? Why?

Answer 4

1. R prime sign on V1 & V2
   Due to slow right ventricular depolarisation resulting in a 2nd R wave (RSR)
2. T wave flattening / inversion
3. sometimes left axis deviation

Question 5

How do you calculate HR with ECG?

Answer 5

300 / No. of large squares between R waves (R-R interval).

Question 6

Which wave produces a positive deflection in all leads except in aVR?

What does this wave represent?

Answer 6

P wave

Question 7

What are the deflections seen in the QRS complex?

Answer 7

Q wave - negative deflection
R wave - positive
S wave - negative

page 186

Question 8

Normal duration of the PR interval?

Answer 8

0.12-0.2s

Question 9

How would you describe the rhythm of ECGs?

Answer 9

The time between successive R waves

Question 10

What is a regularly irregular rhythm?

What is an irregularly irregular rhythm?

And examples of conditions?

Answer 10

RI - irregular rhythm but with clear pattern (heart blocks)

II - irregular rhythm no pattern (atrial fibrillation)

Question 11

What causes LBBB?

Answer 11

Ischaemic heart disease
Fibrosis of conduction pathways
HTN
Acute MI
Aortic stenosis
Cardio myopathies

LBBB can NEVER be considered normal/physiological

Question 12

Changes are seen in the R wave in RBBB?

Where can changed be seen in for LBBB?

Answer 12

ST segment and T wave

Question 13

For LBBB and RBBB, M patterns on seen on which leads?

Answer 13

V1 - RBBB

V6 - LBBB

Question 14

What is the main change in 1st degree heart block?

Answer 14

PR interval fixed but prolonged

Question 15

What are the 2 types of 2nd degree heart block?

Answer 15

Type 1 / Mobitz 1

Type 2 / Mobitz 2

Question 16

What is the main change in 2nd degree heart block?

Answer 16

Mobitz 1 - PR interval gets progrressively longer after each p wave until no conduction at all then cycle repeats.

Mobitz 2 - Each P wave is not always followed by a QRS. ratios can be 2:1 or 3:1. PR interval fixed however.

Question 17

3 Characteristics of 3rd degree heart block?

Answer 17

1. No conduction through av junction. atria and ventricles conduct independent of each other
2. P waves may merge with QRS if conduction happens together
3. QRS abnormally shaped

Question 18

Why is 3rd degree heart block dangerous?

Answer 18

Can cause asystole (cardiac arrest) due to reduced cardiac output

Question 19

Common causes of the 3 heart blocks?

Answer 19

1. Anterior and Inferior Myocardial infarctions (note infarction of diff parts of the heart will cause diff heart blocks)
2. Drugs; B- blockers () Calcium channel blockers (Verapamil), Cardiac glycosides (Digoxin)
3. Cardiomyopathies
4. CHD

Question 20

Which heart block tends to have infectious causes i.e. rheumatic fever and myocarditis?

Answer 20

type 1 / mobitz 1

Type 3 complete block

Question 21

Causes of ST elevation?

What is relevant ST elevation

Answer 21

Impending infarction
Pericarditis
Early repolarisation - Normal in some young males
vasospastic angina

relevant if it exceeds;
1mm in a limb lead
2mm in precordial/chest leads

make sure to read electure too!

Question 22

On an ECG if a pulse is regular and p waves are visible what is the rhythm?

Answer 22

Sinus rhythm

Question 23

Which 2 leads to look at to calculate the axis? WHY?

Answer 23

Lead 1 and aVF as they are perpendicular to each other

Question 24

In addition to a negative aVF, what other lead must be negative for a true left axis deviation?

Answer 24

Lead 2

Question 25

ST depression in leads II, III and aVF is consistent with which condition?

Answer 25

inferior ischaemia