Cardiac Electrophysiology Flashcards
What are the 7 conduction pathways through the heart?
1) SA node (normal pacemaker)
2) Intranodal tracts (controversial)
- AV nodal tract
- Bachmann’s bundle to LA
3) AV node
4) Bundle of His
5) Bundle Branches
6) Purkinje fibers
7) Ventricular muscle
what is the relationship of the component of the ECG w/ the mechanical events in the heart?
P-Wave
Atrial depolarization
what is the relationship of the component of the ECG w/ the mechanical events in the heart?
PR interval
Atrial Systole and AV nodal delay
what is the relationship of the component of the ECG w/ the mechanical events in the heart?
QRS complex
ventricular depolarization (atrial depolarization)
what is the relationship of the component of the ECG w/ the mechanical events in the heart?
QT interval
Ventricular systole
what is the relationship of the component of the ECG w/ the mechanical events in the heart?
T wave
Ventricular repolarization
Action potential with a PLATEAU phase are found where?
Atrial muscle cells
Ventricular muscle cells
Action potentials arising om the SA node and AV node are biphasic. what does that mean?
they have a depolarization and depolarization phase with no plateau phase.
what is the RMP of the cardiac ventricular cell?
-90 mV
What are the phases of the ventricular action potential.
Phase 4
Resting membrane potential (diastole)
What are the phases of the ventricular action potential.
Phase 0
Rapid depolarization
Na+ diffuses into cell
AKA the upstroke of the potential
What are the phases of the ventricular action potential.
Phase 1
Transient (breif) repolarization
Cl- influx
K+ Efflux
What are the phases of the ventricular action potential.
Phase 2
Plateau
Ca+ influx
(as always K+ efflux)
What are the phases of the ventricular action potential.
Phase 3
Repolarization
K+ Efflux
What are the phases of the ventricular action potential. Phase 4 (last phase 4)
RMP
(diastole)
Na+ / K+ pump operates to restore intracellular Na+ and K+ to appropriate levels
See page 103 in sweat book for diagram
pg 103 sweat book
What are the phases of the SA or AV nodal action potential?
Phase 4
RMP (Diastole) Spontaneous depolarization to threshold K+ efflux Na+ influx Ca++ influx (during last 1/3 of phase)
What are the phases of the SA or AV nodal action potential?
Phase 0
SLOW depolarization
Ca++ and Na+ diffuse into cell
(side note it is the L-type Ca+ channels aka slow Ca++ channels thus the reason it is slow depolarization)
What are the phases of the SA or AV nodal action potential?
Phase 1
Gotcha there is no phase 1
What are the phases of the SA or AV nodal action potential?
Phase 2
Gotcha again with nodal action potential there is no phase 1 and phase 2
What are the phases of the SA or AV nodal action potential?
Phase 3
Repolarization
K+ Efflux
What are the phases of the SA or AV nodal action potential?
back to phase 4
RMP (diastole)
R/T the action potential of the SA node….. changing the rate of what phase leads to a change in HR?
Phase 4
R/T the action potential of the SA node prolonging the phase 4 does what?
slows HR
R/T the action potential of the SA node shortening the Phase 4 dose what?
increases HR
then next questions teach you to read the question closely…. pay attention to nodal action or ventricular action potentionals.
read carefully
on what phase of the NODAL ACTION potential does digitalis work to SLOW the HR?
Phase 4
- Dig slows the HR by slowing phase 4 depolarization of cells in the SA and AV node
on what phase of the NODAL ACTION potential do CCB’s work to SLOW the HR
Phase 4
- CCB slow HR by slowing phase 4 depolarization of cells in the SA and AV node
on what phase of the NODAL ACTION potential does Lidocaine or phenytoin work to control VENTRICULAR dysrhythmias?
Phase 4
to recap why these drugs work on phase 4
in the NODAL action potential Ca++ is in phase 4 there is no plateau phase as with the ventricular action potential
on what phase of the VENTRICULAR ACTION POTENTIAL do CCB’s work?
Phase 2
Plateau phase
The resting membrane potential of the cardiac ventricular cell is what?
-90 mV
What ion is responsible for establishing the transmembrane resting potential
K+
When the gated Na+ channel is in the inactive state ( phase 2), the cardiac cell is in the ____ _____ period?
absolute refractory period
an influx of what ion causes the ventricular cell to produce a plateau in phase 2 of the action potential?
Ca++
Ca++ ions influence the opening of the gated K+ channel, with Hypocalcemia what happens to the duration of the plateau phase?
prolong
Ca++ ions influence the opening of the gated K+ channel, with Hypercalcemia what happens to the duration of the plateau phase?
shortened
on an ECG tracing each mm corresponds to how many seconds?
0.04 seconds
The QRS complex results from what and what phase?
Ventricular depolarization
Phase 0
The T wave results from what? and what phase?
Ventricular repolarization
phase 3
the QT interval reflects the duration of what phase of the action potential?
Plateau phase (2)
with HYPOcalcemia what happens to the QT interval?
it is prolonged
with HYPERcalcemia what happens to the QT interval?
it is shortened
peaked or tented T waves reflect what K+ problem?
Hyperkalemia
U waves reflect what K+ problem
Hypokalemia
what leads indicate Posterior inferior MI and what coronary artery supplies it?
II, III, aVF
Right (RCA)
which leads indicate septal, anterior wall MI? and what coronary artery supplies it?
V2-V5
Left Anterior Descending (LAD)
which leads indicates a lateral wall MI? and what coronary artery supplies it?
I, aVL, V4 - V6
Left Circ
MAP is determined by what 2 factors?
CO
SVR
CO is determined by what 2 factors?
HR
SV
SV is determined by what 3 factors?
Preload
Afterload
Contractility
Preload is determined by what 2 factors?
IV volume Venous tone ( when veins constrict blood is diverted to the heart, and vice versa)
The major determinant of IV volume is the amount of what in the body?
Sodium
what hormone is most important for controlling vascular volume
Aldosterone
Compared with the normal heart, the size of the left ventricle chamber is NOT changed what what type of hypertrophied heart?
concentric
Compared with the normal heart, the size of the left ventricle chamber IS substantially increased what what type of hypertrophied heart?
Eccentric
