ECG Flashcards
what are the 3 unique properties of cardiac myotcytes
- automaticity
- rhythmicity
- conductivity
what is the inherent discharge rate of the SA node?
60-100 times per min
this rhythmicity creates the sinus rhythm
what is the inherent discharge rate of the AV node?
40-60x per minute
what is the inherent discharge rate of the His-Pukinje fibers?
30-40 times per min
T/F: the faster/higher discharge rate predominates
TRUE
autonomic influence > SA > AV > Purkinje fibers
what does the P wave depict?
atrial depolarization
the impulse is spread to the L atrium via the Bachmann bundle
what does the PR interval depict?
the spread of depolarization reaches the AV, there is a slight delay
where are bundle branches located?
interventricular septum
what does the QRS complex reflect?
ventricular depolarization
what does the T wave represent?
ventricular repolarization
what is the absolute refractory period?
the period in which the heart cannot be stimulated to contract
represented by the interval from the beginning of the QRS complex to the apex of the T wave
the standard 12 lead ECG consists of what?
6 limb leads + 6 chest leads
List the 6 different limb leads
- standard limb leads → I, II, III
- augmented limb leads → aVR, aVL, aVF
the limb leads provide a view of the heart in the ______________
frontal plane
where is V1 placed
4th intercostal space
R sternal border
where is V2 placed?
4th intercostal space
L sternal border
where is V3 placed?
between leads V2 and V4
where is V4 placed?
5th intercostal space in midclavicular line
where is V5 placed?
horizontally even with V4
but in the anterior axillary line
where is V6 placed?
horizontally even with V4 and V5 but in the midaxillary line
ECG chest leads provide a view of the heart in the ___________
horizontal plane
which leads are placed over the R side of the heart?
V1 and V2
which leads are placed over the interventricular septum?
V3 and V4
what do leads V5 and V6 demonstrate?
changes on the left side of the heart
phrase to remember where to place telemetry leads
white right
snow over grass
brown ground
smoke over fire
when performing a single lead assessment, what are you looking for?
- Heart rhythm or rate
- normal waveforms
- abnormal waveforms
which lead is frequently used if you perform a single lead assessment?
chest lead 5
OR
limb lead II
*they both provide a picture of the LV
on an ECG strip, how many squares equal 1 and 6 seconds?
5 big squares = 1 sec
30 big squares = 6 sec
Methods of determining heart rate from an ECG strip
- 300, 150, 100, 75, 60, 50 method
- count the number of large boxes between 2 adjacent R waves than 300/this count