ECG Basics Flashcards
What is the 5-step approach to reading an ECG?
Rate, rhythm, axis, hypertrophy, infarct/ischemia
During the resting state, cardiac cells are ______.
polarized
What is the resting membrane potential?
- 90mV
What is the difference between depolarization and repolarization?
depolarization = cells go from - to + repolarization = cells go from + to -
In order for an action potential to fire, the ______ must be met.
Threshold
What is the voltage of the threshold for an action potential?
-55 mV
Action potentials are due to fluxes in which 3 ions?
Na+, Ca2+, K+
How many phases are in an action potential? Please name them from first-to-last.
4, 0, 1, 2, 3
T/F: Phase 4 is the resting phase.
TRUE
Which phase of an action potential is the rapid depolarization phase?
0
The plateau phase is called phase ____.
2
Which node primarily determines HR?
SA node
The left bundle branch has 3 branches in total. What are they?
left anterior fascicle, left posterior fascicle, septal fascicle
Define automaticity.
The ability for certain cells of the heart to undergo spontaneous depolarization.
There is a hierarchy of automaticity with the tissue of the heart. The dominant pacemaker is the one with _________.
Greatest degree of automaticity (the fastest)
What is the spontaneous depolarization rates of the SA node, AV node, and ventricular myocardium?
60-100, 40-60, 20-40
The septum depolarizes from ____ to ____.
L -> R
From first-to-last, name all the steps of the sequence of conduction system activation.
SA node > RA/LA > AV node > Bundle of His > Septum > Bundle Branch > Purkinje Fibers > Myocardium
A R’ wave denotes a ______.
Second positive deflection.
The Q-wave, also called the septal Q-wave, is a result of _________.
The septum depolarizing from left to right.
When an ECG wave is equally positive and negative this is referred to as _____.
isoelectric
If the depolarization wave travels perpendicular to the lead, what type of wave should you expect to see?
isoelectric
An impulse traveling toward a lead will cause a _____ deflection on the QRS.
positive
The J point indicates what?
The end of QRS and beginning of ST segment.
Also referred to as the “electrical baseline”, this is called the ____ segment.
TP
The T-wave represents _________?
Ventricular repolarization
Conduction via the AV node is represented by the ____ interval.
PR
T/F: The QT interval represents the beginning of ventricular depolarization to the end of ventricular repolarization
TRUE
Why is there a delay at the AV node?
To allow the ventricles to fill before contraction.
What is the standard rate of an ECG paper?
25 mm/sec
The 1-mV standardization mark is ____ mm tall
10
On an ECG paper, each small box represents ____ seconds and each 5 small boxes represents ____.
0.04 sec, 0.20 sec
What are the 3 methods of measuring HR?
(# of RR intervals in 6s) x 10 method
300,150,100,75,60,50 method
1500/# small boxes between RR intervals or 300/# big boxes between RR intervals.
What is Bazett’s formula?
QTc = QT/ (square root RR (s)) ; RR = 60/HR
What is the normal range for QTc?
.35-.44s (350-440 ms)
If HR is ______ the QTc = QT.
60
What is Bazett’s formula used for?
Correct QT interval for HR
