The Electrocardiogram - Nordgren

Question 1

What is Doppler Electrocardiography?

Answer 1

• Measures and visualizes the speed and direction of blood flow.
  
  • Red: blood moving toward the probe
  • Blue: blood moving away from the probe
• Useful for detecting valve stenosis or insufficiency
• Uses sonogram technique (ultrasound)

Question 2

What is the ESPVR? How does it reflect cardiac contractility?

Answer 2

• End-Systolic Pressure-Volume Relationship
  
  • Plot ESV vs. ESP on PV loop
  • used to assess contractility
    
    • Decreases in contractility are associated with a downward shift of the ESPVR line

Question 3

What is Fick’s Principle? What is it used for?

Answer 3

• Calculates the rate at which a substance is being added to or removed from the blood as it passes through an organ
• Q = X_tc / ([X]_a – [X]_v)
  
  • Q: flow
  • X_tc: amount of substance consumed
  • [X]_a: what goes in arterial
  • [X]_v: what goes out veinous
• Most accurate measure of CO!

Question 4

What is Cardiac Index?

Answer 4

• Cardiac Index = CO / body surface area
  
  • relates cardiac function to the size of the individual
  • use nomogram to determine suface area from height and weight

Question 5

What is physiological basis of the ECG?

Answer 5

• The result of currents propagated through the extracellular fluid.
  
  • currents are generated by the wave of excitation that travels through the heart.

Question 6

What is the EKG used to evaluate?

Answer 6

• Electrical properties:
  
  • excitation rate
  • excitation rhythm
  • impulse conduction

Question 7

What does the P wave signify in an EKG?

Answer 7

Atrial depolarization

Question 8

What does the PR interval signify in an EKG?

Answer 8

conduction time through atria & AV node

Question 9

What is the normal PR interval in msec?

Answer 9

120-200 msec

(3-5 tiny boxes)

Question 10

What does the QRS complex signify in an EKG?

Answer 10

Ventricular Depolarization

Question 11

What is the normal time length of a QRS complex?

Answer 11

60-100 msec

(1.5-2.5 tiny boxes)

Question 12

What does the ST segment signify on an EKG?

Answer 12

Plateau phase of ventricular APs

Question 13

What does the T wave signify in an EKG?

Answer 13

Ventricular repolarization

Question 14

What does the QT interval signify in an EKG?

Answer 14

Total duration of ventricular systole

Question 15

What is the normal time length of the QT interval?

Answer 15

<380 msec at normal HR (60bpm)

(less than halfway between Q –> Q)

Question 16

What/Where are the three ECG regions with no voltage?

Answer 16

1. End of PR Interval (between P & Q)
2. ST Segment
3. After T wave

Question 17

What are Einthoven’s basic electrocardiographic conventions?

Answer 17

• Einthoven’s Triangle:
  
  • ECG trace is a recording of the voltage difference measured between two points on the triangle between R & L arms and L leg.
    
    • Bipolar limb leads

Question 18

What is a normal Mean Electrical Axis?

Answer 18

anywhere from -30° to 90°

Question 19

How do you calculate mean electrical axis?

Answer 19

• First Option:
  
  • lead with largest R wave
  • I=0°, II=60°, aVF=90° III=120°, aVL=-30°, aVR=-150°
• Equiphasic Approach:
  
  • Determine which lead contains the most equiphase QRS complex
  • find which lead lies 90° away from most equiphase lead and its corresponding value
• Third:
  
  • measure difference of QRS above and below baseline in lead I and III
  • use chart to draw lines

Question 20

What plane does a 6-Lead ECG record the electrical activity of the hear?

Answer 20

frontal plane

Question 21

What plane does a 12-Lead ECG look at the electrical activity of the heart?

Answer 21

transverse plain