Cardiac Arrhythmias Flashcards
arrhythmias
What is the cause?
abnormal heart rhytms
altered impulse formation, impulse conduction or both
bradycardias
It has ______ (increase/decrease) firing rate
slow heart rhythms
decreased
tachycaridas
It has _________ (decrease/increase) firing rate
fast heart rhytms
increased
What are the factors cause the altered impulse formation in tachycardias?
increase automaticity of SA node & of latent pacemakers
automaticity of atrial/ ventricular myocytes
triggered activity
What are the factors cause the altered impulse formation in bradycardias?
decrease automaticity of SA node
What are the factors cause the altered impulse conduction in tachycardias?
What are the factors cause the altered impulse formation in bradycardias?
unidirectional block & reentry
conduction block
T/F: In normal conditions, only SA node cells are able to depolarize itself to threshold
False.
AV node, Bundle of His & Purkinje fibers cells can also depolarize itself
Why does triggered activity lead to the tachycaridas?
some action potentials can trigger abnormal depolarizations that result in extra heart beats or rapid arrhythmias
T/F: cardiac tissue damage can cause myocytes outside the specialized conduction system to acquire automaticity
True
Which pacemaker cells have the fastest firing rate? 2nd & 3rd?
SA node > AV node & Bundle of His > Purkinje fibers
Describe the cells depolarization & repolarization
1) phase 4 depolarization: the Na+ channels slowly open
2) phase 0: progressive decline in K+ efflux & Na+ channels is inactive while Ca2+ slowly influx
3) K+ efflux progressively while Ca2+ channels slowly closes
What are factors that determine firing rates?
slope of phase 4 depolarization
the maximum negative diastolic potential
the threshold potential
the rate of pacemaker current (If) is equivalent to ___________
What does If depend on?
the slope of phase 4 depolarization
the # and kinetics of individual pacemaker channels through the current flows
The more negative MDP (maximum diastolic potential), the _______ firing rate as the slop of phase 4 depolarization _________ (less steeper/ more steeper)
longer
less steeper
The less negative threshold potential, the ______ firing rate as the slope of phase 4 depolarization is ________ (longer/shorter)
longer
longer
What modulate SA node?
sympathetic nervous system
Why do we say that SA node is a native pacemaker?
Because it has the highest firing rate -> set the HR
True/False: Automaticity of SA node can increase under exercise or emotional stress
True
Through what cells receptors does sympathetic system stimulate SA node?
what are hormones that these receptors react with?
ß-adrenergic receptors
epinephrine or norepinephrines
What are two factors of firing rate depends on that sympathetic stimulation affect?
steeper the slope of phase 4 depolarization
shift threshold to more negative values
What are the factors of firing rate depends on that parasympathetic system affect?
shifts maximum negative diastolic potential (MDP) is more negative
decreases the slope of phase 4 depolarization
How does PNS decrease the slope of phase 4 depolarization?
by decreasing the probability of pacemaker channels being open
what are the arrhythmias as consequences of decreased SA node?
escape rhythm
supraventricular arrhythmias
ventricular arrhythmias
escape rhythms
what will happen to impulse formation in escape rhythms
SA node is suppressed -> decreased firing rate
impulse formation is shift to latent pacemakers cells
What are the types of escape rhythms in heart?
Explain each
nodal or junctional escape beat: originate in AV node through His-Purkinje fibers (normal QRS)
ventricular escape beat: originate from Purkinje fibers (abnormal QRS)
What is the cause of escape rhythms?
strong parasympathetic stimulation
Where does supraventricular arrhythmias occur?
Does it have normal or abnormal QRS?
What are types of Supraventricular arrhythmias?
above the ventricle
normal
PSVT, Atrial flutter & atrial fibrilation
Describe the ECG of atria flutter
rapid succession of identical, back to back atrial depolarization waves (P wave)
atria flutter
T/F: all atrial impulses are transmitted to ventricles in atria flutter
regular rapid arrhythmias
False. Not all because AV node is in refractory period
T/F: SA node is more sensitve to parasympathetic stimulation than latent pacemakers cells
T/F: ventricular escape beat have normal QRS complex
False
abnormal
atrial fibrilation
Describe the ECG
irregular rapid impulses from atrial foci depolarize atria
chaotic & erratic baseline with no discrete P waves & irregular space QRS complex
Ventricular arrhythmas has ______ (normal/abnormal) QRS complex
abnormal
What are the symptoms of ventricular arrhythmias?
premature ventricular contraction
ventricular tachycardiacs
ventricular fibrilation
premature ventricular contraction (PVC)
ectopic beat
ectopic beats
What are the causes of ectopic beats?
when latent pacemaker develops rate of depolarization faster than of SA node -> disturbance of impulse formation
ischemia, electrolyte disturbance & hypoxemia
T/F: The impulse in ectopic beats are premature relative to normal rhythm
True
What is the cause of ventricle tachycardia?
What can ventricle tachycardia lead to?
the re-entry mechanism
ventricular fibrilation
ventricular fibrilation
rapid, irregular ventricular depolarization due to the impulse generated from ventricular foci
early after depolarizations
Why does this happens?
changes in membrane potential in the positive direction that interupt normal repolarization
because action potential duration is longer than normal
What phase does early after depolarization occur in?
phase 2 (plateau) and phase 3 (during repolarization)
T/F: early after depolarization can be self-pertuating & lead to repeated depolarizations and tachycaridas
True
When does delayed after depolarization occur?
after repolarization but before another normal action potentials would occur
True/False: the impulses can’t be blocked when it enters the region of the heart that is non-conductive
false
fixed block
the block is caused by a barried in which fibrosis or scarring replaces conducting myocytes
What does block within the AV node or His/Purkinje system do?
prevent the impulse propagation to the more distal sites
1st degree of AV block
What are the causes?
delayed conduction between atria & ventricle
vagal stimulation, beta-receptor antagonist, amyloidosis, sarcoidosis
2nd degree of AV block
3rd ______
intermitten or cyclical failure of impulse conduction
failure of impulses conduction
What are the causes of 3rd degree of AV block?
atria & ventricle beat independently; ventricle escape rhythm (atrial rate is faster than ventricular rate)
His/Purkinje block
failure of impulse conduction through one of bundle branches -> ventricle depolarize much slowly
unidirectional block & re-entry
an electrical rhythm circulates repeatedly around a re-entry path & recurrently depolarize a region of cardiac tissue
What type of heart diseas is this?
Mobitz type 1 - 2nd degree block
What type of heart disease is this?
mobitz type II - 2nd degree block
no R wave
