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Cardiac Rhythms

By: Virginia Titman, MSN, RN

EKG Tracing

Wave

0.12 - 0.20 sec

0.04 – 0.20 sec

0.36 – 0.44 sec

PR Interval

Atrial Depolarization

Starts at beginning of P and ends at the beginning of Q

QRS Complex

QT Interval

Ventricle Depolarization and Repolarization

0.12 – 0.20 seconds

Ventricle Depolarization

Starts at the beginning of Q and ends at the end of S

0.04 – 0.12 seconds

Stars the beginning of Q and ends at the end of T

0.36 – 0.44 seconds

ST Segment

Interval between Ventricle Depolarization & Repolarization

Starts at the end of the S and starts at the beginning of T

SHOULD be FLAT; used to measure for an MI

PR Segment

Delay of AV node

Allows ventricles to fill with blood

EKG Strip

Each Big Box = 0.20 sec

Each Small Box = 0.04 sec

EKG Interpretation Steps

Identify and Examine the P wave

Measure the PR interval

Measure the QRS Complex

Identify and Examine the T wave

Measure the QT Interval

Identify the Rhythm

Determine the HR

Interpret the Strip

Step 1 & 2: Identify and Examine the P wave; Measure the PR interval

Is there a P wave before every QRS Complex? ( A P wave should be present before every QRS Complex)

Is the P wave upright? (An upright P wave is normal)

Measure your PR interval (Normal PR interval 0.12-0.20 sec)

Step 3: Measure the QRS Complex

Is there a QRS Complex? ( A QRS Complex should always follow a P wave)

Measure your QRS Complex (Normal QRS Complex 0.04 – 0.12 sec)

Is this narrow or wide? (Narrow QRS < 0.04 and Wide QRS >0.12)

Step 4: Identify and Examine the T wave

Most labile wave in the EKG

Can be upright, inverted, notched, large or small

*View the next slide all the different T waves

There are approximately 63 different reasons for a T wave abnormality. The starred examples are the most common “need to know” examples

Step 5: Measure the QT interval

Identify you QT interval

Measure your QT interval (Normal QT interval 0.36 – 0.44 sec)

Is this AT interval short or long? (Short QT < 0.36 and Long QT >0.44)

Step 6: Identify the Rhythm

Is this rhythm Regular or Irregular?

R R R

Step 7: Determine the Heart Rate using the 6 Second Method

Is this a 6 second strip?

Count the number of R in between and multiply by 10

Recommended for irregular rhythms

1 2 3 4 5 6 7 8

Step 7: Determine the Heart Rate using the 1500 Box Method

Use the Box Method when you don’t have a 6 second strip

Take 1500 divided by the number of small boxes between 2 R’s

Recommended for regular rhythms

R R

1 2 3

Step 8: Interpret you Rhythm – Normal Sinus Rhythm (NSR)

Rate: Atrial and ventricular rates of 60 to 100 beats/min

Rhythm: Atrial and ventricular rhythms regular

P waves: Present, consistent configuration, one P wave before each QRS complex

PR interval: 0.12 to 0.20 second and constant

QRS duration: 0.04 to 0.12 second and constant

Take a Break!

Take a break because we are going to be discussing the most common rhythms you should be familiar with for NCLEX/ATI.

Sinus Tachycardia (ST)

Rate: Atrial and ventricular rates of 100 to 149 beats/min

Rhythm: Atrial and ventricular rhythms regular

P waves: Present, consistent configuration, one P wave before each QRS complex

PR interval: 0.12 to 0.20 second and constant

QRS duration: 0.04 to 0.12 second and constant

Supraventricular Tachycardia (SVT)

Rate: Atrial and ventricular rates of 150-300 beats/min

Rhythm: Atrial and ventricular rhythms regular

P waves: Present, consistent configuration, one P wave before each QRS complex (often invisible d/t embedding in T-wave)

PR interval: 0.12 to 0.20 second and constant (may be difficult to measure)

QRS duration: 0.04 to 0.12 second and constant

Sinus Bradycardia (SB)

Rate: Atrial and ventricular rates less than 60 beats/min

Rhythm: Atrial and ventricular rhythms regular

P waves: Present, consistent configuration, one P wave before each QRS complex

PR interval: 0.12 to 0.20 second and constant

QRS duration: 0.04 to 0.12 second and constant

Premature Atrial Complexes/Contractions (PAC’s)

Rate: Any atrial or ventricular rate

Rhythm: Irregular

P waves: Present, inconsistent configuration (P-waves will look different or may be hiding in T-wave), one P wave before each QRS complex

PR interval: May differ between beats

QRS duration: 0.04 to 0.12 second and constant

Atrial Fibrillation (AF or A-fib)

Rate: Atrial rate up to 350-600 bpm; ventricular rates of 60 to 100 beats/min (>100 bpm = AF w/ rapid ventricular response [RVR])

Rhythm: Atrial and ventricular rhythms irregular

P waves: “Wavy baseline”; Many P-waves before QRS

PR interval: unmeasurable and inconsistent

QRS duration: 0.04 to 0.12 second and constant

P P P P P P

Atrial Flutter (A-flutter)

Rate: Atrial rate up to 350-600 bpm; ventricular rates of 60 to 100 beats/min (>100 bpm = AF w/ rapid ventricular response [RVR])

Rhythm: Atrial irregular; ventricular (usually) regular

P waves: “Sawtooth” baseline (F-waves); Many P-waves before QRS; usually measured in number of P-waves observed (ex: 4:1 A-flutter)

PR interval: Unmeasurable and inconsistent

QRS duration: 0.04 to 0.12 second and constant

1 2 3 4

1st Degree Heart/AV Block (1AVB)

Rate: Any rate (brady-, tachy-, or normal)

Rhythm: Atrial and ventricular rhythms regular

P waves: Present, consistent configuration, one P wave before each QRS complex

PR interval: >0.20 second and constant

QRS duration: 0.04 to 0.12 second and constant

(NHLBI, n.d.)

2nd Degree Heart/AV Block Type I (Mobitz I or Wenckebach)

Rate: Any rate (brady-, tachy-, or normal)

Rhythm: Atrial irregular; ventricular regular until dropped beat

P waves: Present, consistent configuration; some with QRS that doesn’t follow

PR interval: Varies; Lengthens until a QRS is dropped

“Longer, longer, longer, block; then you’ve got a Wenckebach!”

QRS duration: 0.04 to 0.12 second and constant

(NHLBI, n.d.)

2nd Degree Heart/AV Block Type II (Mobitz II)

Rate: Any rate (brady-, tachy-, or normal)

Rhythm: Atrial regular; ventricular irregular (due to dropped beats)

P waves: Present, consistent configuration, some P waves without a QRS complex

PR interval: 0.12-0.20 second

QRS duration: 0.04 to 0.12 second and constant

(NHLBI, n.d.)

3rd Degree Heart/AV Block or Complete Heart Block (3AVB or CHB)

Rate: Atrial normal or tachycardic; Ventricular bradycardia (usually)

Rhythm: Atrial and ventricular rhythms regular

P waves: Present, consistent configuration, are not associated with QRS complexes

“Divorce Rhythm”

PR interval: Unmeasurable

QRS duration: Any length (may be >0.12 sec), but constant

(NHLBI, n.d.)

Premature Ventricular Complexes (PVC’s)

Rate: Any

Rhythm: Any; extra ventricular complexes

PVC’s may be bigeminal, trigeminal, consecutive, etc. and unifocal or multifocal

P waves: Present, consistent configuration, one P wave before most QRS complexes

PR interval: 0.12 to 0.20 second and constant

QRS duration: 0.04 to 0.12 second and constant EXCEPT for ventricular complexes, which are >0.12 sec

Ventricular Tachycardia (VT)

Rate: No atrial rate; Ventricular rate usually 140-180 or higher

Rhythm: Ventricular rhythms regular

P waves: None

PR interval: N/A

QRS duration: >0.12 second

LETHAL DYSRHYTHMIA!

Ventricular Fibrillation (VF)

Rate: Unmeasurable

Rhythm: Irregular s/t quivering of ventricles

P waves: None

PR interval: N/A

QRS duration: N/A

LETHAL DYSRHYTHMIA!

Fatal if not reversed w/in 3-5 mins!! Uses a lot of oxygen d/t quivering ventricles

Ventricular Asystole (Asystole)

Rate: 0

Rhythm: None, may have some p-waves without QRS or random QRS complexes

P waves: None

PR interval: None

QRS duration: None

LETHAL DYSRHYTHMIA!

Pulseless Electrical Activity (PEA)

Electrical activity without mechanical response

ECG rhythm present without pulse

Treatment: ACLS until pulse/BP restored

LETHAL!

Thank You!

Please Complete the EKG Workbook