Cardiology 7.12 Flashcards
V tach what happens to CO
it decreases, HR increases and can’t pump out enough blood
why doesn’t CO decrease during exercise
the arteries dilate
major reason SA node changes firing rate
input from autonomic nervous system
increased vagal tone, another way of saying
Ach
name examples of ways to decrease SA nodal firing rate
increased vagal tone beta blockers hypothyroidism L-type Ca channel blockers sick sinus syndrome
E & NE do what
increase rate of diastolic depol
what is major controller of SA firing at rest
vagal tone
what has little effect of ventricular conduction system
vagal stimulation
one consequence of pronounced bradychardia:
escape beats
what is escape beat
losing QRS wave - example: thrd degree heart block
latent pacemakers have escaped and are driving ventricles at a much slower rate
describe third degree heart block
complete blockage of AP conduction from atria to ventricles (AV node) lower pacemaker driving ventricles
width of QRS indicitve of
conduction delay through ventricles
abnormally slow SA firing can result in
escape beats & escape rhythms
what is driving ventricular firing in third degree heart block
lower pacemakers
what is ectopic beat
premature depol from sinus node
originates from site other than sinus node
what would cause ectopic beats & ectopic rhythm
high catecholamines
ischemia
digitalis toxicity
mechanism of ectopy
increased automaticity of latent pacemakers
abnormal automatciity of cells outside the specialized conduction system
triggered activity
what is triggered activity
early after depol
delayed after depol
what would happen to p wave in atrial premature depol
inverted p wave
dra example of PAC
pg 176
what does PAC stand for
premature atrial contraction
PAC and PVC are examples of
ectopic hart beats
what does PVC stand for
premature ventricular contraction
PAC frequently caused by
excessive catecholamines
two types of triggered actiity
DAD & EAD
DAD stands for
delayed afterdepolarization
DAD describe
extra depolarization. not a problem by itself, but if it depolarizes to threshold it will fire an action potential, and one AP wouldn’t be a problem, but you can develop a tachycardia
mechanism of DAD
Spontaneous SR calcium release, that will trigger calcium wave which activates Na-Ca exchange which produces the DAD
overall there is a inward current which will depol the cell
what does Na-Ca exchange do
keeps Ca levels down in cell
three sodium in for two calcium out
what is result of Na-Ca in DAD
depols the cell b/c more + in than out so cell gets more +
EAD stands for
early afterdepolarization
what do you see in EAD
pg 183
mechanism of EAD
reactivatoin of calcium current (or sodium), can lead to ventricular fibrillation
EAD can lead to
ventricular fibrillation
EAD is promoted by what
conditions rtaht prolong action potential duration
examples of things that can prolong AP duration
K channel blockers inherited loss of K channels hypokalemia hypocalcemia bradycardia
slower HR what hapens to AP duration
longer
hypokalemia does what to Ap duration
hyperpolarizes and prlongs AP duration
long QT can trigger
ventricular tachycardia
pg 185
pg 185
bigger the calcium current, what does it do to conduction
faster it will conduct
conduction velocity in AV node, upstroke is
calcium current
the bigger calcium current n AV node, what happens to velocity
increased
examples of what can be a block
closed gap junctions, fibrosis
two types of second degree heart block
Mobitz type I and II
motibz type I
progressive preceeding block is preogressively longer p wave, and then it wll drop a beat
what is mobitz type I block called
wenckebach block
motbitz type II block
PR interval is normal
random dropped WRS (double check on this)
bundle branch block what will it do
widens QRS
what is normally last thing to repol
base of left ventricle
left bundle branch block tends to shift axis to
left
one biggest thing that can cuase conduction block
ischemia
ischemia what does it do to K and Na
reduces Na and high K - so depols cell
if you reduce the sodium currnet you will
reduce conduction velocity (except AV and SA node)
pg 200
pg 200
