ECG interpretation

Question 1

ECG strips are divided into boxes. How many small boxes in a large box

size in mm of the small boxes

Answer 1

25

1mm x 1mm

Question 2

rate of ECG recording and therefore

how much time does a large box and a small box show

Answer 2

• ECG records ast 25mm/s  5 large squares covered each sec

one large square = 0.2sec; one small square = 0.04sec

Question 3

t or f

100% of the time the electrical impulse stimulates muscle ontraction

Answer 3

f sometimes there are rare disorders that make this incoordinated

Question 4

what is the ony time during cardiac cycle that L ventricle is perfused and why does tachycardia affect this

Answer 4

• Left ventricular muscle perfused only during diastole. As such, tachycardia = less perfusion to LV. If demand exceeds supply  LV ischemia (+ poss infarc)

Question 5

what does asystole or isoelectric line indicate

Answer 5

• Isoelectric line: no electrical signal on ECG; indicates asystole (systole absent in pt, has cardiac arrest)

Question 6

if there is a rise in the line on the ECG (up from the isoelecric line what does this indicate

Answer 6

• Rise in line on ECG: positive deflection – means electrical act is following the same direction of flow as bipolar lead or traveling toward unipolar lead

Question 7

what is an artefact

what could cause this

Answer 7

artefact (= anything appearing on ECG trace that is not from cardiac origin)
often looks like jagged line

could be from any electrical activity eg shivering

Question 8

how can you identify artefacts/distinguish them from being cardiac in origiin

Answer 8

• Artefact can usually be ID’d by incongruity w other info (eg: with AFib would see jagged isoelectric line, but the QRS complex would appear normal. With artefact, see jaggedness in QRS as well)

Question 9

the strenght of the plateau or absolute refractory period in the cardiac cycle is d/t what ion

Answer 9

o Strength of contraction d/t amount of intracellular Ca2+ and so length of plateau influences contractile strength

Question 10

value of resting voltage in mv

Answer 10

-90mv

Question 11

where are the electrodes placed for lead II

Answer 11

• Lead II (2) is normally being shown if not specified. Goes from R arm to L foot

Question 12

how s amplitude meas or shown in the strip

Answer 12

Vertically(AMPLITUDE): each small box is 0.1mV, or 1mm, adding up to 0.5mV or 5mm **this will come in handy later when we discuss MIs

Question 13

can you note the atria contracting partway through the P wave

Answer 13

no! the ECG only detects electrical activity

Question 14

what to look at in P wave

Answer 14

in my notes from med surg and elsewhere it says it should be less than 0.11 secs on her slides it says 0.6-0.12
Represents atrial depolarization
When evaluating a P wave, look closely at its characteristics, especially its location, configuration, and deflection

Question 15

how are dysrhythmias named

Answer 15

o Dysrhtymias are named according to site of origin of impulse and mechanism of formation or conduction involvd eg impulse that originates in SA node and at slow rate is sinus bradycardia

Question 16

what aspect do you focus on with the PR interval

what does the PR interval reflect

duration

Answer 16

When evaluating a PR interval, look especially at its duration
From the beginning of the P wave to the beginning of the QRS complex.
The PR interval tracks the atrial impulse from the atria through the AV node, bundle of His, and right and left bundle branches. When evaluating a PR interval, look especially at its duration.

Duration: 0.12 to 0.20 second

Question 17

what do changes in the PR interval reflect

Answer 17

Changes in the PR interval indicate an altered impulse formation or a conduction delay, as seen in AV block.

Question 18

what char does a normal QRS comple have

how high can it be

what does it come after

how long is it and what can you compare its length to

Answer 18

Follows the PR interval
5 to 30 mm high but differs for each lead used
0.06 to 0.10 second, or half of the PR interval

Duration is measured from the beginning of the Q wave to the end of the S wave (or from the beginning of the R wave if the Q wave is absent)
consists of the Q wave (the first negative deflection after the P wave), the R wave (the first positive deflection after the P wave or the Q wave), and the S wave (the first negative deflection after the R wave

Question 19

ST segment what to pay extra attn to

what does it look like
what does abn indicate

Answer 19

Pay special attention to the deflection of the ST segment. 
A normal ST segment has the following characteristics:
Extends from the S wave to the beginning of the T wave 
Usually isoelectric (neither positive or negative

A change in the ST segment may indicate myocardial damage. An ST segment may become either elevated or depressed.

Question 20

what is the point that marks the end of the QRS complex and start of the ST segment known as

Answer 20

The point that marks the end of the QRS complex and the beginning of the ST segment is known as the J point.

Question 21

what to evaluate with a t wave

is duration significant

Answer 21

When evaluating a T wave, look at the amplitude, configuration, and deflection.

Duration is not measured

Question 22

what are normal T wave char

what does it come after
how high is it and what shape

Answer 22

Normal T waves have the following characteristics:
Follows the S wave
0.5 mm in lead II configuration—typically round and smooth
deflection—usually upright in lead II

Question 23

what does T wave represent

Answer 23

The T wave represents ventricular recovery or repolarization.

Question 24

what is most imp about QT interval

Answer 24

duration

Question 25

where does Qt interval start and stop and how long should it be

Answer 25

Location—extends from the beginning of the QRS complex to the end of the T wave Duration—varies according to age, sex, and heart rate; usually lasts from 0.36 to 0.44 seconds; shouldn’t be greater than half the distance between consecutive R waves when the rhythm is regular.

Question 26

what normal process will affect QT interval duration

Answer 26

heart rate will shorten it if increasing

Question 27

what does QT interval meas

Answer 27

The QT interval measures ventricular depolarization and repolarization. The length of the QT interval varies according to heart rate. The faster the heart rate, the shorter the QT interval. The QT interval shows the time needed for the ventricular depolarization-repolarization cycle.

Question 28

what would short or long QT interval indicate

Answer 28

An abnormality in duration may indicate myocardial problems. Prolonged QT intervals indicate that the relative refractory period is longer. Prolonged QT syndrome is a congenital conduction- system defect present in certain families. Prolonged QT intervals indicate that the relative refractory period is longer. Short QT intervals may result from digoxin toxicity or hypercalcemia.

Question 29

what is a U wave are they always there what is most significant about them

Answer 29

The U wave may not appear on an ECG Represents the recovery period of the Purkinje or ventricular conduction fibers The configuration is the most important characteristic of the U wave.

Question 30

char of U wave what can cause them

Answer 30

Location—follows the T wave Typically upright and rounded A prominent U wave may be due to hypercalcemia, hypokalemia, or digoxin toxicity

Question 31

what are the 8 steps to ECG interpretation (just the names of the steps

Answer 31

1. Determine the rhythm- 2. Determine the rate-cant just look at VS monitor. Do p wave and R wave. If the pt has irreg heart rhythm make sure you have 6 second strip. 3. Eval the P wave- 4. meas PR interval-make sure they are all the same. 5. meas QRS 6. eval T wave 7. QT interval-can be alt by brady or tachy eg from exercise. QT represents the entire ventricle cycle 8. Note any abn and conclude your analysis

Question 32

step 1 of ECG interpretation how is this done what tool do you need

Answer 32

1)Determine the atrial and ventricular rhythm: Measure from P-P and R-R Are they regular or irregularly spaced? Using either calipers or the paper method

Question 33

what is the paper method for determining the rhythm

Answer 33

not as easy as caliper method take paper and meas R-R and make notes on your paper then move those little noted areas to the next R and compare and so on then do for P-P

Question 34

how to determine the rate from an ECG this is best for regular rhythm

Answer 34

Various methods to determine the rate…. Most accurate is dividing by 1500, this works well for regular rhythms: Count the small squares between two consecutive P waves and then divide 1,500 by that number to get the atrial rate. To obtain the ventricular rate, use the same method with two consecutive R waves. ie: 1500/20 = 75 BPM

Question 35

determining rate for irreg rhythm how long of a strip will you need

Answer 35

you need 6 sec strip

Question 36

det rate of irreg rhythm method

Answer 36

The 10 times method is helpful for irregular rhythms: Print a 6 second strip (ECG paper is marked at 3 second intervals) Count the number of P waves and multiply by 10, and repeat for the R waves

Question 37

how many lg boxes is in between the vertical hash marks (the black lines) how many seconds is this

Answer 37

15lg boxes | 3 seconds

Question 38

what do you look at when evaluating the P wave

Answer 38

Are there P waves? How do they look? Normal? Upright? Rounded? Are they all a similar size and shape? Is there one P wave per QRS complex?

Question 39

what do you look at when eval the PR interval how long should it be?

Answer 39

Count the small squares between the P wave and the beginning of the QRS complex, multiply by 0.04 Normal range = 0.12 – 0.20 seconds Are the PRIs constant?

Question 40

what do you look at when eval the QRS what is normal range

Answer 40

Measure from the end of the PR interval to the end of the S wave Count the number of small squares and multiply by 0.04 Normal range = 0.06 -0.10 seconds Is each QRS the same? If not, measure and record each one separately Does each QRS follow a P wave?

Question 41

do you meas the legnth of T waves what do we need to look at with them

Answer 41

Are there T waves? Are they upright in lead II? Are they all the same shape? Does each T wave follow a QRS complex?

Question 42

what kind of relationship does QT interval have with heart rate

Answer 42

inverse relationship As the heart rate increases, the QT interval decreases; as the heart rate decreases, the QT interval increases.

Question 43

what to eval when looking at QT interval

Answer 43

Count the number of small squares between the beginning of the QRS complex and the end of the T wave, where the T wave returns to the baseline and multiply by 0.04 Normal range = 0.36 – 0.44 seconds

Question 44

what is step 8 of ECG analysis and what do you do

Answer 44

Note any abnormalities and conclude your analysis Are there any ectopic beats? Anything else unusual? Is the ST segment isoelectric? Elevated? Depressed? Record and document your findings

Question 45

how to document your analyss

Answer 45

1-The origin of the rate (sinus node, atria, AV node, or ventricles) 2-The rate (bradycardic, tachycardic) 3-Rhythm abnormalities (flutter, fibrillation, heart block, escape rhythm, or other arrhythmias)