Interpretation of Arrhythmias

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 Rhythms PAC - 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