CRITICAL CARE NURSING NOTES
<TOPICS: ECG>
By Rachel Chan (RN)
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)
<TOPICS: ECG>
By Rachel Chan (RN)
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)
