10 ECG, CO2 Elimination, & ETCO2 Flashcards
Einthoven’s Triangle
Discovered ECG mechanism
Electrocardiogram
Potential difference across the membrane (voltage)
Each cardiomyocyte can create potential difference across the heart
Vector
Mean potential difference
Direction & magnitude
Length correlates to magnitude
(-) → (+)
Lead I
R arm (-) → L arm (+) 0°
Lead II
R arm (-) → L leg (+) 60°
Lead III
L arm (-) → L leg (+) 120°
Mean Electrical Axis (MEA)
Average all depolarization waves = resultant vector
Normal
-30° to 60° MEA
Lead I positive (upward deflection)
Lead II positive
aVF positive
Left Axis Deviation
-30° to -90°
Causes: L ventricular enlargement, R side MI, R side tension pneumo, normal variant (diaphragm elevation
Right Axis Deviation
90° to 180°
Causes: R ventricular enlargement, L side MI, L side tension pneumo, pediatrics variant
aVR
Augmented voltage right R arm set to positive Sum L arm + L leg (-) starting point at chest center -150°
aVL
Augmented voltage left L arm set to positive Sum R arm + L leg (-) starting point at chest center -30°
aVF
Augmented voltage foot Foot set to positive Sum R arm + L arm (-) starting point at chest center 60°
V Leads
Transverse plain V1 = 120° V2 = 90° V3 = 75° V4 = 60° V5 = 30° V6 = 0°
Anteroseptal
V1
V2
Anteroapical
V3
V4
Anterolateral
V5
V6
Lateral
I, aVL, V5, V6
Left circumflex artery