CARDIOLOGY - ECG Interpretation (Week 4)

Question 1

What are the 5 steps to interpreting ECGs?

Answer 1

1) Analyze the Rhythm
2) Analyze the Rate
3) Analyze the P waves
4) Analyze the QRS Complex
5) Analyze the P-R Interval

Question 2

Using the 5 steps to interpret ECGs will help to avoid what?

Answer 2

pattern recognition

Question 3

Step 1: Analyze the Rhythm - what are you analyzing specifically?

Answer 3

• rhyhtm is determined by analyzing the ventricular rhythm (QRS complex)
• Compare R-R intervals on an ECG tracing from left to right

Question 4

What are the two methods in analyzing heart rhythm?

Answer 4

• use of ECG calibers
• pencil/pen and paper

Question 5

Pencil/pen and paper method for analyzing heart rhythm

Answer 5

• Place a straight edge of a piece of paper near peaks of two consecutive R waves
• mark off the distance
• compare this R-R interval with other R-R intervals in the ECG tracing

Question 6

Regular vs. irregular rhythm

Answer 6

Regular:

• distances between R-R intervals are equal OR
• equal to or <0.16 seconds (4 small squares) apart

Irregular:

• distance between the shortest and longest R-R intervals vary by >0.16 seconds (4 small squares)

Question 7

Regularly irregular rhythm

Answer 7

Irregularity has a pattern

Question 8

Occasionally irregular rhythm

Answer 8

One or two R-R intervals maye be irregular (i.e. drops a beat and another pacemaker takes over)

Question 9

Irregularly irregular rhythm

Answer 9

totally irregular and no relationship between R-R intervals (such as a-fib)

Question 10

Step 2 - Analyze the Rate - what are you analyzing specifically?

Answer 10

• heart rate is determined by analyzing ventricular rate (QRS complexes)
• an adequate rate of ventricular contractions is responsible for cardiac output

Question 11

Analyzing the rate can be done in 4 ways, including:

Answer 11

• Triplicate method
• HR calculator ruler
• R-R method
• 6-second count method

Question 12

Triplicate method

Answer 12

• requires memorizing the following numbers: 300-150-100-75-60-50-43-37-33
• each number represents a 5mm square (1 large square)
• count each 5mm square between R waves

Cons: only accurate if the rhythm is regular

Question 13

Heart rate (HR) calculator ruler

Answer 13

• a literal ruler you have to buy, has directions on it that you can follow

CONS: mechanical devices or tools should not be relied on as they are not readily available

• reasonably accurate if the rhythm is regular

*DO NOT RELY ON THIS ONE

Question 14

6-second count method

Answer 14

• useful in obtaining quik rate in regular and irregular rhythms (but use the triplicate method for regular rhythms)
• count the number of R waves in a 6 second strip and x10

CONS: least accurate method in determining heart rate

Question 15

R-R method to calculate HR

Answer 15

• count the large squares between peaks of two consecutive R waves
• divide that number by 300 to obtain HR

CONS: only if you’re good at mental math; only accurate if the rhythm is regular

Question 16

Step 3- Analyze the P waves

What are the 5 components to observe when evaluating P waves?

Answer 16

1) Are the P waves present?
2) Are the P waves regular (similar to R-R interval)?
3) Are the P waves upright or inverted?
4) IS there one P wave for every QRS complex?
5) Do all the P waves look alike (morphology)?

Question 17

The normal P wave in Lead II looks:

Answer 17

positive, smoothly rounded, usually precedes each QRS complex

Question 18

Step 4: Analyze the QRS Complex - what are you analyzing specifically?

Answer 18

QRS complex width and regularity

Question 19

Normal vs Abnormal QRS complex

Answer 19

Normal: <0.12 seconds

Abnormal: equal or >0.12 seconds (equal or more than 3 small squares) - may indicate conduction problems in the ventricles

Question 20

Step 5- Analyze P-R interval

What does P-R interval represent?

What is normal vs abnormal?

Answer 20

Analyzing the interval that represents the time it takes for an impulse to be conducted through the atria and AV node

Normal: 0.20 seconds or less

Abnormal: >0.20 seconds (more than 5 small squares)

Question 21

Abnormal PR interval may indicate:

Answer 21

a delayed in conduction through AV node or Bundle of His