2 - ECG Flashcards
Why does the <3 have to contract?
To pump to very vital vascular beds/circulation
When someone presents chest pain, what do you in a fully equipped hospital setting and why?
ECG! To dx if cardiac or non-cardiac chest pain
What will be represented in the ECGοΌ
Fast response AP/summation of electrical activity generated by enormous no of individuals cardiac cellsοΌmyocytesοΌin the atria and ventricles
Normal cardiac cell membranes are capable of
- Polarized under RMP
- Rapidly discharge (depolarize)
- Conduct/propagate electrical currents
- *certain cells (sinus node),depolarize and repolarize automatically
Determine the phases of the fast response AP in an ECG tracing
Phase 0-1 = QRS
Phase 2 = ST segment
Phase 3 = T wave inscription
Phase 4 = TQ segment
Position of Limb Leads? Augmented Limb Leads?
Draw Hexaxial Reference System
What view of the heart will you get from limb leads? Precordial/chest leads?
Limb leads - frontal view
Chest/Precordial leads - horizontal view
Placing of precordial/chest leads
V1 - 4th ICS, just to the right of the sternum
V2 - 4th ICS, just to the left of the sternum
V4 - 5th ICS, left midclavicular line
V3 - between V2 and V4
V5 - anterior axillary at same levels as V4
V6 - midaxillary at same level as V4
Aspects of the Heart Monitored by the ECG leads?
2, 3, aVF = inferior
V5, V6, aVL = lateral
V2-V4 = anterior/septal
V1-V2 = Posterior wall
What does each horizontal line represent in an ECG tracing? Vertical?
1 horizontal = 0.04 s or 40 ms
1 vertical = 0.1 mV
What should you do first when you look at an ECG tracing? Before analysis
Look at calibration!
Should be 10 mm = 1 mV amplitude
Additional leads in children? Why do we need additional leads?
V3R, V4R (Right)
V7 (Left)
We need more leads because children are normally physiologically RV dominant = there could be some degree of RV enlargement or hypertrophy after birth
Why?
>In utero, RV is working as hard as your left since the resistance in the pulmonary vascular bed is also high)
What does a positive deflection indicate? Negative? Biphasic?
A. Positive deflection
- mean wave of depolarization spreads towards the leadβs positive poles
B. Downward/Negative deflection
- mean is away the + pole or towards the - pole
- e.g. aVR
C. Biphasic
- mean depolarization path is directed at right angles (perpendicular) to any lead axis
Segments
PR
ST
TP
Intervals
- PR
- start of P to start of Q - QRS
- Start to end of QRS - QT
- Start of QRS to end of T - R-R