Interpretation of Arrhythmias

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Interpretation of Arrhythmias

 by
Louise Diehl, RN, MSN, ND, CCRN, ACNS-BC, NP-C
Nurse Practitioner - Owner
Doctor of Naturopathy
Lehigh Valley Wellness Center

Here are some guidelines to help you with EKG rhythm interpretation.

Steps to interpretation:

    Calculate heart rate (ventricular) *
        Multiply # of R waves in strip
            6 second strip by 10
            3 second strip by 20
        Divide the # of large squares between two R waves into 300 (less accurate)

    Rhythm (ventricular) **
        Measure the interval between 2 R waves
        Regular vs. Irregular ( > 3 tiny blocks or 0.12 seconds)
        Do not estimate. Use an EKG caliber or paper.

    Examine P wave
        Present, upright, all look the same

    Measure PR interval
        Beginning of P to beginning of QRS complex
        Should be the same
        Normal 0.12 to 0.20 seconds

    Measure QRS duration
        Beginning of Q to end of S
        Normal is < 0.12 seconds

    Examine ST segment (should be iso-electric)

    Examine T wave (upright, flat, inverted, spiked)

* If P wave occurs before every QRS, atrial rate will be the same as ventricular.
** If P wave occurs in the same place before every QRS, atrial rhythm will be the same as ventricular.

Basic Characteristics of Cardiac Rhythms
Dysrhythmia Rate Rhythm P-R
Interval QRS
Interval Comments
Sinus Rhythms
Normal Sinus  60-100  Regular  0.12-0.20 sec  <0.12 sec  
Sinus Bradycardia  <60  Regular  0.12-0.20  <0.12 sec  
Sinus Tachycardia  100-160  Regular  0.12-0.20 sec  <0.12 sec  
Sinus Arrythmia  60-100  Irregular  0.12-0.20 sec  <0.12 sec  Rhythm varies with respiration
Sinus Pause/Arrest  Depends on pauses  Usually regular with pauses  0.12-0.20 sec  <0.12 sec  
Atrial RhythmsPAC  Depends on underlying rhythm  Interrupts underlying rhythm  0.12-0.20 sec  <0.12 sec  Regularity depends on underlying rhythm and number of PAC’s
Atrial TachycardiaSVT  150-250  Regular  0.12-0.20 sec  <0.12 sec  P waves may be hidden in previous T due to rapid rate
Atrial Flutter  V rate varies A rate 250-350  Irregular  Variable  <0.12 sec  “Sawtooth” pattern F waves
Atrial Fibrillation  Controlled AF <100
Uncontrolled AF  >100  Irregular  Nonmeasureable <0.12 sec  
Wandering Pacemaker  60-100  Irregular  <0.20 sec  <0.12 sec  Morphology of P wave changes
Heart Blocks
1st AV block  60-100  Usually regular  >0.20 sec  <0.12 sec  P:QRS ratio 1:1
2nd Degree Mobitz 1, Wenkebach  V < A  Atrial regular
Ventricular irregular  Progressively longer until one QRS dropped  <0.12 sec  P:QRS ratio 1:1
2nd Degree Mobitz II  Remains Constant  Atrial regular, Vent regular or irregular  variable     More P’s than QRS’s
3rd Degree Block Complete  40-60 Junct
20-40 Vent  p-p regular
r-r regular  Nonmeasurable     More P’s than QRS’s
Junctional Rhythms PAC  Depends on underlying rhythm  Interrupts underlying rhythm        For all junctional rhythms P waves are inverted. The can be hidden, precede or fall after the QRS
Junctional Escape  40-60  Regular  <0.12 sec if present  <0.12 sec  
Accelerated Junctional  60-100  Regular  <0.12 sec if present  <0.12 sec  
Junctional Tachycardia  100-180  Regular  <0.12 sec if present  <0.12 sec  
Ventricular Rhythms PVC  Depends on underlying rhythm  Interrupts underlying rhythm  No PR interval  >0.12 sec wide and bizarre  
Ventricular Tachycardia  150-250  Regular  No PR interval  >0.12 sec wide and bizarre  
Ventricular Fibrillation  No cardiac output  Irregular  No PR interval  No QRS  Chaotic
Idioventricular  <20-40  Regular  No PR interval  >0.12 sec bizarre  Slows as heart dies
Ventricular Asystole  None  None  None  None  No electrical activity

Reference:  ECG Interpretation Made Incredibly Easy. Springhouse Corporation, Springhouse, PA, 1997