ECG's

Question 1

P Wave

Answer 1

• 0.08-0.10 sec (2-2.5 boxes wide)
• not higher than 2mm
• normal depolarization, contraction of the atria (L and R)
• originates from SA node
• inverted in AVR

Question 2

QRS complex

Answer 2

• Represents depolarization of the left and right ventricles
• Originates from the intraventricular septum below the AV node
• 2 boxes wide (0.06-0.10 seconds)
• Q wave- first negative deflection, R wave first positive deflection and S wave first negative deflection after an R wave*

Question 3

T wave

Answer 3

• height less than 5 mm in limb leads & 10 mm high in chest leads
• represents repolarization of the ventricles
• 0.10-0.25 seconds (6 small squares)
• first positive deflection after QRs complex
• rounded and asymmetrical
• inverted in aVR
• upright in I, II, V3-V6

Question 4

U wave

Answer 4

• after T wave
  represents delayed repolarization of the Purkinge fibres
• uncommon

Question 5

PR segment

Answer 5

• (begins with the end of the P wave and ends with the onset of the QRS complex)
• 0.02-0.10 seconds
• represents the time between the end of atrial depolarization and start of ventricular depolarization
• may take longer if there is a delay in progression of electrical impulse from av node to bundle branches*

Question 6

QT interval

Answer 6

• (first wave of QRS to end of T wave)
• QT duration is inversely proportional to HR ( as HR will increase QT will decrease)
• Total time for venrticles to depolarize and repolarize
• Less than 0.45 seconds
• usually less than half of R-R interval
• relative refractory period (at top of T wave- QRS complex)

Question 7

ST segment

Answer 7

• represents the peroid between ventricular depolarization and ventricular replolrization
• 0.20 seconds or less- depending on ( 5 small squares)
• J point- change of direction

Question 8

ECG interpretation

Answer 8

1. Rate- normal? tachy? brady?
2. Rhythm
   - regular
   - irregular
3. P wave
   - shape
   - size (2-2.5 small squares) (2mm high)
4. PR interval
   - calculate (how many squares) ( 3-5 small
   squares)
5. QRS complex
   - shape
   - size
   - width (how many squares) (3 small squares)
6. Pathological Q wave
7. ST segment
   - is it on the isoelectric line
   - look for the j point
   - size, shape

Question 9

Absent P wave

Answer 9

• A.F
• A. FL
• Junctional or ventricular rhythm

Question 10

Sinus rhythm

Answer 10

• Upright rounded P wave w QRS
• Rate: 60-100
• Rhythm: regular
• P wave normal
• PR: 0.12
• QRS: normal

Question 11

Sinus arrhythmia

Answer 11

• Sinus rhythm but irregular beat
• Rate: normal
• Rhythm: irregular
• P wave: rounded normal’
• PR: normal
• QRS: normal
  T wave: present

mild irregularit due to ventilation