Normal Durations/Intervals

Question 1

P wave duration and amplitude in seconds

Answer 1

duration: 0.06-0.10 seconds
amplitude: 0.5-2.5mm

Question 2

PR Interval in seconds

Answer 2

0.12-0.20 seconds

long PR interval = 1st degree complex

short PR interval = supraventricular arrhythmia

Question 3

QRS duration in seconds

Answer 3

0.06-0.11 seconds

longer QRS complex = ventricular hypertrophy/ enlargement, bundle branch block

Question 4

PR interval vs segment

Answer 4

PR interval begins at the start of the P wave and ends at the start of the QRS complex

PR segment is the isoelectric (flat line) between the end of the P wave and the beginning of the QRS complex

Question 5

ST segment

Answer 5

the isoelectric line (flat line) that follows the QRS complex

• we look at this for ischemia

Question 6

T wave

Answer 6

larger, slightly asymmetrical waveform that follows the ST segment

Question 7

J-point

Answer 7

where the QRS complex meets the ST segment

Question 8

QT Interval

Answer 8

begins at the start of the QRS complex until the end of the T wave

• measures the time of ventricular depolarization and repolarization
• normal duration is 0.36-0.44 seconds
  
  • this is for 60bpm; varies based on heart rate
  • as the HR slows the QT interval increases

Question 9

Right Atrial Enlargement

Answer 9

aka “P pulmonale”

if amplitude of P wave is >2.5mm[2.5blocks] (normal is 0.5-2.5)

clinical conditions: pulmonic stenosis, tricuspid stenosis, tricuspid regurgitation

Question 10

Left Atrial Enlargement

Answer 10

• Duration of the P wave is >0.10 sec (2.5 blocks)
  
  • normal P-wave duration is 0.06-0.10 seconds
• P-wave usually notched “P mitrale”
• terminal portion of P wave in V1: negative, duration of 0.04 sec (one small block) and depth of 1mm (one small block)

Question 11

Bilateral atrial enlargement

Answer 11

increased amplitude and duration of P wave

amplitude >2.5mm, duration >0.10 seconds

Question 12

Right Ventricular Hypertrophy

Answer 12

less common than LVH

• due to pulmonary HTN or pulmonic stenosis
• R. axis deviation occurs due to increased thickness of R ventricle
• Criteria:
  
  • R axis deviation (>+90degrees)
  • R wave > S wave in V₁
    
    • R wave is usually >7mm tall
  • S wave > R wave in V₆