cardiac conduction 2 Flashcards
P wave =
atrial depolarization
QRS =
ventricular repolarization
T wave =
T wave =ventricular repolarization
PR interval =
index of conduction time across the AV node
QT interval =
total duration of depolarization and repolarization
The Q is an
initial negative deflection,
the R is the
upward deflection
the S is a
terminal negative deflection.
The sinus node depolarization initiates the
beat but is too small to see
on the ECG.
how many separate leads in a ECG?
12
the shape of the QRS depends on?
where the positive electrode is placed
On EKG, The first signal seen is the
P wave generated by depolarization of first the right and then the left atrium.
why is QRS voltage greater than P?
The QRS voltage is much greater than the P voltage because ventricular mass exceeds atrial mass.
Why is the T wave wider than QRS?
The T wave is wider than the QRS because ventricular repolarization takes considerably longer than depolarization.
why is atrial depolarization not seen?
because normally it s buried in the QRS which is a much larger signal.
If the activation wave is \_\_\_\_\_, a positive (upward) deflection will be recorded
toward a sensing electrode
the ____ the muscle mass, the ___ the voltage recorded
greater
greater
the pattern of deflection varies with the____
position of the recording electrodes
The SA node is high in the ____ and the depolarization wave sweeps _____.
right atrium
downward and leftward.
a lead with a positive electrode near the right arm normally has a predominantly ____ QRS
negative
a lead with a positive electrode near the left leg has a ____ QRS.
positive
normal sequence of activation of the ventricles
- The upper portion of the septum is depolarized from left to right.
- There is then depolarization downward in the septum to the apex.
- Depolarization is from endocardium to epicardium
- Depolarization moves upward from apex in the free walls of both ventricles.
- depolarization of the base of the ventricles.
SA (sinoatrial node) abnormalities:
cause “sick sinus syndrome” resulting in slow sinus rates or takeover by other pacemakers which may be either fast or slow.
3 types of AV block
1st, 2nd, 3rd degree
