cardiac electrophysiology Flashcards
A 21 y/omale from Southeast Asia dies in his sleep. Post-mortem molecular autopsy demonstrates a loss-function-mutation in the Voltage Gated Sodium Channel (SCN5a). This will have the following effect on the action potential:
phase 0 and 1 since this sodium channel is responsible for phase 0
can result in long QT syndrome when overactivated –> burmuda syndrome
what defines the plateu phase in an action potential
L type ca channels
ca coming in and k moving out both slowly
what channels are key for excitatation and contraction
L type ca –> ca induced ca release
what is channel and phase and responsible for LQTS 1 and 2 inherited arrhythmias syndromes
–IKr(rapid)
–IKs(slow)
phase 3
in KCNQ1, loss of this can cause long QT
what phase and channel is responsible for (Torsadede Pointe) drug induced arrthymias and is tested for when developing new drugs
K in phase 3
what activates phase 4 in SA nodal cells
what does phase 4 control
hyperpolarization
heart rate
how does going for a run activate the slope of phase 4
makes it steeper- faster hr
Catecholamines
name mechanisms to slow SA firing
- Slows depolarization-
- Lowers resting –> opens K
- Raises threshold decreases Ca
can slow or stop AV conduction
Blocking the HERG channel will have the following effects on the action potential AND ECG:
1.Prolong BOTH Phase III and QT interval
could cause Torsade de Pointe
Anisotropy
ordered propogation
what is Arrhythmogenic Right Ventricular Cardiomyopathy
Disruption of Desmosomes in Intercalated Disc Causes Heart to Turn into Fat!
How can arsenic cause QTc prolongation
trafficking defect, preventing the HERG channel from getting to the sarcolemma (phase III)
what can cause exercise induced tachycardia
leaky RyR channel
A.Ca2+influx leads to delayed-after-depolarization mediated triggered arrhythmia
what kind of things could cause a inversion where the repolarization occurs from endo to epi (normal repolarization is epi to endo)
pathologic and could be thickening of the heart
what would you estimate the rate to be if the p to p covered 5 boxes
60
300 150 100 75 60 50
what are the 5 questions you ask every ecg
- What is the Rate?
- What is the Rhythm?
- What is the Axis?
- What are the Intervals?
- Waveform?
what would you see in lead 1 if you had left axis deviation due to left ventricular hypertrophy
what if you had right axis deviation due to right ventricular hypertrophy
positive in lead 1 but isoelectric in AVR
reverse
if the myocardium is thicker than __ mm you increase risk of sudden cardiac death
3
what does the PR interval represent and how long should it be
start of atrial dep to ventricular depolarization
120-200
what does the QT interval represent and how long should it be
start of ventricular depolarization to the end of ventricular repolarization
should be less than 440 in men and 460 in women
what impact would testosterone have on the QT interval
shortens it
what is the qrs complex and how long should it be
qrs –> begining to end of ventricular dep
90-100
advances is more than .12s
what kind of things could cause an altered waveform
obesity
COPD
effusions
hypothyrodism
kATP and MI could cause ST elevatio
which occlusion can be electrially silent
LCx
where would you see a signal for LCx or diagnal
V5/V6
I
AVL
where would you see a signal for LAD
septal?
V1-V4
septal (V1,V2)
where would you see a signal for RCA
II, III, aVF
why can you see Why can you see the fibrillatorywaves in the ventricle but not atria
mass = larger magnitude
how do you tell R vs L BBB
R –> LAD V1
L –> V6
