ECG basics Flashcards
P wave represents
depolarization of the artria
QRS represents
depolarization of the ventricle (absolute refractory periord)
what cardiac myocyte action potential phases are represented by QRS
phase 0 and phase 1 (absolute refractory period)
Q
first downard deflection following P (not always present)
R
first upeard deflection of QRS complex
S
any negative deflection following and R wave
T wave represents
ventricular repolarization
apex of T wave represents what phase of cardiac myocyte action potential
phase 3 (relative refractory period)
what is a U wave
repolarization of purkinje fibers and papillary muscle - appearance of U wave is indirectly related to heart rate (usuallly seen in low HR - athletes)
J point
1.) first point of inflection of upstroke in S wave 2.) point at which ECG trace becomes more horizontal than verticle
where is PR interval measured
onset of P wave to onset of QRS
what does PR interval represent
time for impulse to travel from SA node to ventricles
what is the normal PR interval in adults? In kids?
Adults: 0.16-0.20 Kiddos: 0.12-0.20
PR segment is measured where
end of P wave to onset of QRS
PR segment represents
duration of contraction through bundle of his, bundle brances and purkinje fibers
RR interval represents
instantaneous heart rate
QT interval measured
onset of Q to end of T
QT represnets
electrical systole - duration of ventricular depolarization and repolarization
what is the normal QT interval
0.25-0.40
ST segement potential measurement
end of S wave to the inset of T wave
ST segment potential represents which phase of cardiac myocyte action potential
phase 2
location of V1 electrode
right of the sternum in the fourth intercostal space
location of V2 electrode
left of the sternum in fouth intercostal space
location of V4
left mid clavicular line in fith intercostal space
