6. The ECG - calculating heart rate and intervals Flashcards Preview

ESA 2- Cardiovascular System > 6. The ECG - calculating heart rate and intervals > Flashcards

Flashcards in 6. The ECG - calculating heart rate and intervals Deck (19)
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1
Q

What is normal ECG paper speed?

A

25 mm/sec

2
Q

How many small and large squares are there in a second?

A

25 small squares = 1 sec

5 large squares = 1 sec

3
Q

How long does 1 small or large square last?

A

1 small square = 0.04 sec (40 ms)

1 large square = 0.2 sec (200 ms)

4
Q

How many large sqaures are there in 6 seconds and 1 min?

A

6 secs = 30 large squares

1 min = 300 large squares

5
Q

How is heart rate (bpm) calculated for regular and irregular rhythms?

A

Regular
- 300/no. of squares of R-R interval

Irregular
- no. of QRS in 6sec x 10

6
Q

What is the normal range for the PR interval?

A

0.12 - 0.20 secs (3-5 small boxes)

7
Q

What is the normal range for the QRS interval (width of QRS complex)?

A

< 0.12 secs (<3 small boxes)

8
Q

What does the QT interval represent?

A

Ventricular depolarisation + repolarisation

9
Q

Why is QT interval usually corrected for changes in heart rate?

A

QT interval gets shorter with increasing heart rate (shorter diastole) - can mask problems so must be corrected for HR to assess this accurately

10
Q

What is the upper limit for corrected QT interval?

A
  1. 45 secs (11-12 small boxes) in adult males

0. 47 secs (11-12 small boxes) in adult females

11
Q

What is sinus rhythm?

A

Normal rhythm of depolarisation initiated by sinoatrial node (as has fastest rate of depolarisation)

12
Q

How is normality of sinus rhythm assessed?

A

1 - is the rhythm regular? (use rhythm strip and paper)
2 - is heart rate normal (60-100 bpm)?
3 - are P waves present and preceding every QRS?
4- are P waves upright in leads I and II?
5 - is PR interval normal (0.12-0.20 secs/3-5 small boxes)?
6 - is QRS width normal (<0.12 secs/<3 small boxes)?

13
Q

What is a sinus rhythm with rate <60bpm or >100bpm called?

A

sinus bradycardia or sinus tachycardia

14
Q

What does a shorter R-R interval indicate?

A

faster heart rate

15
Q

What does a wider QRS complex indicate?

A

ventricular depolarisations that aren’t initiated by normal conductance mechanism

16
Q

What does a longer P-R interval indicate?

A

slow conduction from atria to ventricles (1st degree heart block)

17
Q

What does a raised or depressed ST segment indicate?

A

myocardial infarction or ischaemia (should be isoelectric)

18
Q

What does a prolonged QT interval indicate?

A

prolonged repolarisation of ventricles, which can lead to arrhythmias as occur in long QT syndrome

19
Q

What are the most common causes of 1st degree heart block?

A
  • AV nodal disease
  • enhanced vagal tone (e.g. in athletes)
  • myocarditis (e.g. from Lyme disease)
  • acute MI (esp. when inferior)
  • electrolyte imbalances (hypokalaemia)
  • medication