Basics
Paper speed of the typical ECG is 25 mm/sec, each little box is 1 mm and each large box is 5 mm
- 1 mm = 0.4 seconds
- 5 mm = 0.2 seconds
- 1 mm (h) = 0.1 mV
LEADS
Each lead represents a vector of the heart's electrical activity
Bipolar leads (frontal plane)
Bipolar leads (frontal plane)
- Lead I: Right Arm (-) to Left Arm (+)
- Lead II: Right Arm (-) to Left Leg (+)
- Lead III: Left Arm (-) to Left Leg (+)
- Lead aVR
- Lead aVL
- Lead aVF
- Leads V1, V2, V3 posterior anterior
- Leads V4, V5, V6
- Depolarization of the heart toward the positive electrode produces a positive deflection
- Depolarization of the heart away from the positive electrode produces a negative deflection
- Repolarization of the heart toward the positive electrode produces a negative deflection
- Repolarization of the heart away from the positive electrode produces a positive deflection
First: Rate, Regularity, rhtyhm
THEN go left to right
RAte
- Normal: R-R intervals between 3-5 big boxes (60-100 bpm)
- Estimate rate: <3= Tachy; >5 = Brady
- Count big boxes from R-R interval: 300, 150, 100, 75, 60, 50
- Accurate calculation: 1500/R-R interval in mm
Regularity
Regular vs Irregular:
- Is the distance between each P-P interval and R-R interval the same?
- Is there an irregular pattern that repeats itself?
- You may need calipers to determine regularity
Rhythm
Sinus: P waves before each QRS in a 1:1 fashion
Non-Sinus: Ectopic, Junctional, Ventricular
Non-Sinus: Ectopic, Junctional, Ventricular