understanding ekgs pgs 11-15

7/27/2019 Understanding EKGs Pgs 11-15

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11

The direction of the waveform gives us information about the direction of flow of

electricity:

(Figure 9: the relationship between waveforms and the isoelectric line)

• Waveforms with a positive deflection represent electricity flowing toward the positivepole, a negative deflection shows movement toward the negative pole, and biphasicdeflection represents that electricity is moving in both directions.

• Rapid conduction will make the complex narrow; slower conduction will make thecomplex wide.

• Higher electrical flow (energy) will make the complex higher or deeper.

The intrinsic rate of the SA node is 60-100 beats per minute. If the SA node fails, or its

impulses are blocked, then a secondary pacemaker will take over. Below is a list of the

heart’s pacemakers and their rates of firing:

Pacemaker: SA Node AV Junction Ventricles

Intrinsic Rate

(beats/min):

60 -100 40 - 60 20 - 40



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Waveforms and Complexes

EKG Interpretation is based upon examining the P-QRS-T, their relationship to each

other, and timing.

• On an EKG waveform, time is measured as length on graph paper (25mm/sec).• There is a dark vertical line each 0.2 seconds or 5 small boxes to create 1 big box.• There is a hash mark on the EKG paper each 3 seconds (15 big boxes).

• 1 small box = 1 mm (.04 sec) • 5 small boxes = 0.2 seconds• Hash marks each 3 seconds • 15 big boxes = 3 seconds• 30 big boxes (3 hash marks) = 6 seconds

2 methods to determine the EKG rate:

A: Count the number of R waves in a 6 second strip and multiply by 10

B: Count the # of large squares between 2 consecutive R waves & divide into 300

(Or memorize this scale):

Line: Value:

1 300

2 150

3 100

4 75

5 606 50

7 43

8 37

9 33



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White‐RightArm(RA) Green‐RightLeg(RL)

Red‐LeftLeg(RL) Brown‐Chest(C)

Black‐LeftArm(LA)

Using the Cardiac Monitor

The EKG records a representation of the electrical activity of the heart, as impulsestravel between two leads. The impulses are detected by electrodes on the skin andtransmitted to the monitor (or telemetry transmitter) via wires. Either three or five color

coded wires are placed on the chest in the following configuration:

(Figure10: Electrode placement)

Most EKG rhythms are interpreted using

lead II measuring electricity flow from RA to the LL

Proper application of electrode pads is a very important step in obtaining accurate and qualitytracings. The goal is to achieve good contact between the electode and the skin. Below aresome tips for good electrode placement:

• Shave sites if necessary. Hair interferes with good contact between the skin and electrode

• Remove excess skin oil from the sites to allow electrodes to stick well. Use alcohol or acetone, being extra gentle if you have just shaved the skin

• Gently abrade the skin to help electrodes stick better. Some companies provide a bumpysurface on the underside of electrodes for this purpose, or you may use a dry washcloth

• Apply a thin coat of Tincture of Benzoin to the site if the patient perspires a lot. Allow to drybefore applying electrodes

• After applying electrodes to prepared sites, press firmly to ensure good contact

• Apply the snap on wires to the electrode pads before applying to the chest to avoidunnecessary pressure on the patient

Lead + Electrode - Electrode

I Left Arm Right Arm

II Left Leg Right Arm

III Left Leg Left Arm



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Analyzing a Rhythm Strip

1. What is the rate?

• To determine the ventricular rate, measure the distance between two

consecutive R waves (R-R interval)• To determine the atrial rate, measure the distance between two consecutive P

waves (P-P interval)

2. Is the rhythm regular or irregular?

• To determine if the ventricular rhythm is regular or irregular, measure the

distance between two consecutive R-R intervals and compare with other R-R

intervals. If the ventricular rhythm is regular, the R-R measurements will be equal

• To determine if atrial rate is regular, measure P-P and compare

3. Is there one P wave before each QRS?• Are P waves present and uniform in appearance?

• Is there a P wave before each QRS or are there P waves not followed by QRS?

• Is the atrial activity occurring so rapidly that there are more atrial beats than QRS

complexes?

4. Is the PR interval within normal limits?

• If the PR interval is less than .012 or more than 0.20 seconds, conduction

followed an abnormal pathway or the impulse was delayed in the area of the AV

node

• Is the PR interval constant or does it vary?

5. Is the QRS narrow or wide?

• What is the duration of the QRS complex?

• <0.10 sec, presumably supraventricular in origin

• >0.12 sec, probably ventricular

• Do the QRS’s occur uniformly throughout the strip?

6. Interpret the rhythm, specifying the site where the dysrhythmia originated (eg

sinus), the mechanism (eg bradycardia), and the ventricular rate. For example:“Sinus bradycardia with a ventricular rate of 38/minute”

7. How is the rhythm clinically significant?

In Simple Terms



15

1. Determine the Rate - < 60 = Bradycardia, > 100 = Tachycardia

2. Determine the Origin -

• Upright P wave = Sinus

• Wavy, Irregularly shaped, or flutter “P waves” = Atrial (fib or flutter)

• Rapid (>150) w/ no visible P wave but “pointed complex” between QRS’s = Atrial Tach (SVT)

• Inverted or absent P waves (with narrow QRS) = Junctional

• Absent P wave with wide QRS = Ventricular

• Extra P waves or P’s without QRS’s = A Heartblock

- A long PRI ( >.20 sec/5 boxes) = 1st Degree Block

- Extra P waves with a constant PRI at each QRS = 2nd Degree Type II

- Progressively longer PRI until a QRS drops = 2nd

Degree Type I (Wenckebach)

- Complete disassociation of P’s to QRS (usually wide QRS) = 3rd Degree Block

*Note, delayed conduction (aberrancy) can cause a wide QRS with P waves = still Sinus

if there is a P wave

Interpretation: Normal Sinus Rhythm

understanding ekgs pgs 11-15

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