Class 4 Flashcards
ECG is a vector (T/F)
True
Wave of (depolarization/repolarization) Flows towards the positive recording electrode
Depolarization
Depolarization goes toward (upward/downward) deflection
Upward
Wave of (Depolarization/repolarization) Close towards the positive electrode
Repolarization
Repolarization goes toward (upward/downward) deflection 
Downward
Ventricular systole is about (-) duration
1/3
Ventricular diastolic is about (-) duration
2/3
P-wave is
Atrial depolarization
QRS complex is
Ventricular depolarization
T-wave is
Ventricular repolarization
U wave is
Repolarization of papillary muscles, delayed repolarization of Purkinje fibres
What is not seen on an ECG and why?
Atrial repolarization, overwhelmed by ventricular depolarization
PR interval
Atrial depolarization to the start of ventricular depolarization
Time required for the impulses generated by the SA node to initiate the depolarization of the ventricular septum
PR interval
PR segment
Time starts at the end of atrial depolarization to the start of ventricular depolarization
Length of segment related to time of delay for the action potential passing through the AV node
PR segment
QRS duration
Indicates duration of ventricular depolarization
Functional integrity of the ventricular conduction system and contractile myocardium
 QRS duration
What is in the ventricular conduction system
- bundle of His
- Bundle branches
- Purkinje fibres
ST segment
End of ventricular depolarization and beginning of ventricular repolarization
The isoelectric line is which segment?
ST segment
There is no electrical activity for the atria and ventricles in what segment?
ST segment
QT interval
Time starts at beginning of ventricular depolarization to the end of ventricular repolarization
Rough estimate of duration of ventricular action potential, is which interval?
QT interval
Which segment is directly correlated with heart rate?
QT interval
What could it mean if you have a short PR interval?
Wolf Parkinson white syndrome
What could it mean if you have a long PR interval?
A heart block, disruption of conduction
What could a wide QRS mean? (3)
One more branch block, ventricular rhythm, hyperkalaemia
What can a tall QRS complex mean
Ventricular hyper trophy
What is hyperkalemia?
High potassium concentration
What does hyperkalaemia due to an ECG?
Gives a wide QRS complex
What will an increase in extra cellular potassium levels cause? In regards to membrane potential
Partial depolarization of the membrane potential’s
What are fast sodium channels?
Voltage gated aNachannels
Sodium channels have both activation and activation gates. Is activation closed or open? Is in activation closed or open?
Activation is closed at resting state, inactivation is open at resting state
At the end of depolarization, the inactivated gates will do what?
Close themselves
After the in activated gates close, what happens?
Repolarization will begin
As the membrane potential approaches resting state during repolarization, what do the in activation gates do?
Reset themselves and start opening their gated
Opening of the inactivation gate will normally follow by
The closing of the activation gates
Opening of the inactivation gate will normally follow by the closing of the activation gates when?
When the membrane potential is returning to resting state
How do you calculate QT interval?
QTc = QT/ Root RR
Why do you need to calculate correlated QT?
It is closely related to heart rate
What could deviation from the isoelectric line mean?
Acute myocardial ischaemia
ST segment elevation could mean
Epicardial ischaemia
Depression of the ST segment could mean
Endocardial ischaemia
What could an inverted T-wave indicate? (3)
Myocardial ischemia, intraventricular conduction delay, anxiety attack
Normally, an ECG contains how many limb leads and how many chest leads?
6 and 6
What are the names of the six limb leads?
I, II, III, AVR, AVL, and AVF
What are the six chestleads called?
V1, V2, V3, V4, V5, and V6
Leads one, two, and three are known as
Bipolar limb leads
Where is lead one?
Negative lead at right arm, positive lead at left arm
Where is lead to?
Negative lead at right arm, positively lead at left leg
Where is lead three?
Negative lead at left arm, positive lead at left leg
