Easy Basics of ECG Learning |study notes

• Step 1: Calculate rate.
• Step 2: Determine regularity.
• Step 3: Assess the P waves.
• Step 4: Determine PR interval.
• Step 5: Determine QRS duration.

Step 1: Calculate Rate

• Option 1
– Count the # of R waves in a 6 second rhythm strip, then multiply by 10.
– Reminder: all rhythm strips in the Modules are 6 seconds in length.

Interpretation? 9 x 10 = 90 bpm

• Option 2

– Find a R wave that lands on a bold line.
– Count the # of large boxes to the next R wave. If the second R wave is 1 large box away the rate is 300, 2 boxes – 150, 3 boxes – 100, 4 boxes – 75, etc.
– Memorize the sequence:
300 – 150 – 100 – 75 – 60 – 50

Step 2: Determine regularity

• Look at the R-R distances (using a caliper or markings on a pen or paper).
• Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Irregularly irregular?

Interpretation? Regular

Step 3: Assess the P waves

• Are there P waves?
• Do the P waves all look alike?
• Do the P waves occur at a regular rate?
• Is there one P wave before each QRS?
Interpretation? Normal P waves with 1 P wave for every QRS

Step 4: Determine PR interval

• Normal: 0.12 – 0.20 seconds.
(3 – 5 boxes)

Interpretation?0.12 seconds

Step 5: QRS duration

• Normal: 0.04 – 0.12 seconds.
(1 – 3 boxes)
Interpretation? 0.08 seconds

Rhythm Summary

• Rate 90-95 bpm
• Regularity regular
• P waves normal
• PR interval 0.12 s
• QRS duration 0.08 s
Interpretation?  Normal Sinus Rhythm

•    Etiology: the electrical impulse is formed in the SA node and conducted normally.

•    This is the normal rhythm of the heart; other rhythms that do not conduct via the typical pathway are called arrhythmias.

NSR Parameters
•    Rate                60 – 100 bpm
•    Regularity            regular
•    P waves            normal
•    PR interval            0.12 – 0.20 s
•    QRS duration        0.04 – 0.12 s
Any deviation from above is sinus tachycardia, sinus bradycardia or an arrhythmia

Arrhythmia Formation
Arrhythmias can arise from problems in the:
•    Sinus node
•    Atrial cells
•    AV junction
•    Ventricular cells

SA Node Problems
The SA Node can:
fire too slow— Sinus Bradycardia

fire too fast— Sinus Tachycardia

Atrial Cell Problems
Atrial cells can:

•    fire occasionally from a focus —Premature Atrial Contractions (PACs)

•    fire continuously due to a looping re-entrant circuit —-Atrial Flutter

Atrial Cell Problems
Atrial cells can also:
• fire continuously from multiple foci Atrial Fibrillation

or
fire continuously due to multiple micro re-entrant “wavelets” Atrial Fibrillation

AV Junctional Problems
The AV junction can:

•    fire continuously due to a looping re-entrant circuit–Paroxysmal   Supraventricular Tachycardia
•    block impulses coming from the SA Node–AV Junctional Blocks

Ventricular Cell Problems
Ventricular cells can:
•    fire occasionally from 1 or more foci –Premature Ventricular Contractions (PVCs)
•    fire continuously from multiple foci–Ventricular Fibrillation
•    fire continuously due to a looping re-entrant circuit–Ventricular Tachycardia