- Critical Care Nursing: ECG/EKG
- Prepared by experienced RN Ms. Chan (BNurs (First Hon, CGPA 3.8/4.0), MPH)
- Provide a thorough introduction to ECG/EKG interpretation for nursing students and other healthcare professionals with no or little experience. Start with an introduction to anatomy and...
Graduated from top university in HK with BNurs(First Hon, CGPA:
3.8/4.0) and MPH degree
By Rachel Chan (RN, BNurs(First Hon), MPH)
, ECG
Cardiac action potential(ventricular myocardial cell)
Absolute Refractory period during repolarization
Two type of cell
Pacemaker cell: automaticity, regularity, excitability, conductivity i.e. SA, AV, purkinje, bundle of his – can
only initiate pace, but not contraction
Myocardial cell: contractility – can only contract
By Rachel Chan (RN, BNurs(First Hon), MPH)
, 5 Phases of myocyte (blue line):
0: depolarization, activation of NA+ channel -> NA+
1: inactivation of the Na+ by the inner gate
2: plateau- K+ out, recovery of cell to original stat
3: rapid repolarization- K+ channel, ca++ pump out by three means
4: flat isoelectric line.
Phase 0,1,2 involve Na, K gate, responsible for the QRS(i.e. ventricular depolarization)
ca responsible for repolarization, ST &T
polarization ≠ contraction, QRS only mean the ventricular depolarization
Contraction and relaxation of heart(cardiomyocytes)
By Rachel Chan (RN, BNurs(First Hon), MPH)
, Refractory period
resist to cell membrane stimulus prevent cardiac spasm/tetany
absolute RP( QRS + upslope T): absolute no response
Relative RP(downslope T): vulnerable period as some cells are repolarized already respond to strong
than normal stimulus
R on T phenomenon: QRS can land on the downslope T VF
Supernormal period(after T): a weaker than normal stimulus can result in depolarization dysrhythmia
ECG background:
SA node -> atrium -> AV node -> bundle of his -> left right bundle branches -> Purkinje fibers ->
ventricles syncytium
Lead: electrical pic of heart from diff direction; ≠electrode
Sinus rhythm: electrical activation begin in the SA node
Cardiac rhythm is identified from whichever lead with the P wave most clearly: Lead II commonly , but lead
I is preferred if severe respiratory s/s(which may affect ECG)
By Rachel Chan (RN, BNurs(First Hon), MPH)
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