CARDIOLOGY - ECG Interpretation (Week 4) Flashcards
What are the 5 steps to interpreting ECGs?
1) Analyze the Rhythm
2) Analyze the Rate
3) Analyze the P waves
4) Analyze the QRS Complex
5) Analyze the P-R Interval
Using the 5 steps to interpret ECGs will help to avoid what?
pattern recognition
Step 1: Analyze the Rhythm - what are you analyzing specifically?
- rhyhtm is determined by analyzing the ventricular rhythm (QRS complex)
- Compare R-R intervals on an ECG tracing from left to right
What are the two methods in analyzing heart rhythm?
- use of ECG calibers
- pencil/pen and paper
Pencil/pen and paper method for analyzing heart rhythm
- 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
Regular vs. irregular rhythm
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)
Regularly irregular rhythm
Irregularity has a pattern
Occasionally irregular rhythm
One or two R-R intervals maye be irregular (i.e. drops a beat and another pacemaker takes over)
Irregularly irregular rhythm
totally irregular and no relationship between R-R intervals (such as a-fib)
Step 2 - Analyze the Rate - what are you analyzing specifically?
- heart rate is determined by analyzing ventricular rate (QRS complexes)
- an adequate rate of ventricular contractions is responsible for cardiac output
Analyzing the rate can be done in 4 ways, including:
- Triplicate method
- HR calculator ruler
- R-R method
- 6-second count method
Triplicate method
- 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
Heart rate (HR) calculator ruler
- 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
6-second count method
- 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
R-R method to calculate HR
- 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
Step 3- Analyze the P waves
What are the 5 components to observe when evaluating P waves?
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)?
The normal P wave in Lead II looks:
positive, smoothly rounded, usually precedes each QRS complex
Step 4: Analyze the QRS Complex - what are you analyzing specifically?
QRS complex width and regularity
Normal vs Abnormal QRS complex
Normal: <0.12 seconds
Abnormal: equal or >0.12 seconds (equal or more than 3 small squares) - may indicate conduction problems in the ventricles
Step 5- Analyze P-R interval
What does P-R interval represent?
What is normal vs abnormal?
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)
Abnormal PR interval may indicate:
a delayed in conduction through AV node or Bundle of His
