Flashcards in ECG Deck (16)

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1

## P wave

###
First short upward movement of the EKG tracing.

- atrial depolarization: It indicates that the atria are contracting, pumping blood into the ventricles.

2

## The QRS complex

###
Normally beginning with a downward deflection, Q; a larger upwards deflection, a peak (R); and then a downwards S wave.

- The QRS complex represents ventricular depolarization and contraction, emptying the ventricles

3

## PR interval

### indicates the transit time for the electrical signal to travel from the sinus node to the ventricles.

4

## T wave

### normally a modest upwards waveform, representing ventricular repolarization and relaxation

5

## How do you calculate accurate HR using an EKG?

###
Count the number of large squares from R peak to R peak, and divide that by 300.

- ie: 300/5 = 60

6

##
How many squares = 1 second?

How many large squares = 6 seconds?

How many seconds does 1 large square =?

How many seconds does 1 small square =?

###
5 large squares

30 large squares = 6 seconds

1 large square = 0.2 sec

1 small square = 0.04 sec

7

##
In individuals with irregular heart rates, how do you measure an accurate heart rate?

- what if there are 7 R waves found in that interval, how many beat in 1 min?

###
Count 30 large squares (6 seconds) and then count how many R waves are found in the 30 large squares.

7 beats in 6 seconds

- There are 60 seconds in 1 min

- There are 70 beats in 1 min

8

## In a normal heart, the time between the onset of atrial depolarization (beginning of P wave) and the onset of ventricular depolarization (beginning of QRS complex) normally varies between what time frame?

###
PR interval = 0.12s - 0.2s

or 3 - 5 small squares

- many imp disorders are associated with alterations in the PR interval

9

## The PR interval is largely determined by what?

###
physiological delay of the depolarization wave in the AV node and transit in the bundle of his.

- many imp disorders are associated with alterations in the PR interval

10

## The QRS interval duration is largely determined by what? What is the width of the QRS interval typically?

###
time taken for ventricular depolarization to be completed.

Normally less than or equal to 3 small squares

(no more than 3 ss!)

11

##
QT interval

- how many squares is it usually?

###
Time between the onset of ventricular depolarization and the end of the ventricular repolarization (beginning of QRS complex and end of T wave)

Normally less than 11 ss at a heart rate of 60 beats per min.

12

## Does the QT interval expand or decrease as the heart rate speeds up?

###
QT interval gets shorter as heart speeds up

- at higher heart rates, possible to miss underlying prolonged QT interval

13

## If you find that QT interval is 8 ss, how many seconds is that?

###
0.32 seconds

1 small square = 0.04 sec

8 small squares = 0.32 sec

14

## Corrected QT interval = ?

### QT / squareroot(RR)

15

## Ventricular depolarization

###
"ventricular systole"

Coordinated transmission of stimulus (cation flows) leading to contraction of the ventricles.

16