11/01 Flashcards
What are the causes of arrhythmias?
abnormal rhythmicity in the pacemaker
* Firing faster/slower
* current sent in a wrong direction
* ectopic pacemaker
Shift of pacemaker from sinus node
Blocks at different points in the transmission
* might cause ectopic pacemaker
Abnormal pathways of transmission in the heart
* normally have a very defined pathway and speed. Ectopic pacemakers might cause AP to go in a different path
Spontaneous generation of abnormal impulses from any part of the heart
* VRM increased
What can cause an ectopic pacemaker in a pacemaker cell?
Increased VRM
Things that increase VRM are things that prevent the heart from _________
Resetting itself
I.e Ischemia in the AV node increase VRM so that the AV node still fires but it is an abnormal beat aka arrhythmia
Anything that increases VRM increases the risk of what
An ectopic pacemaker
Increased K+ levels in the blood leads to an increased ________
VRM
Tachycardia
Abnormal Sinus rhythm where the SA node is firing faster than normal d/t an abnormal SA node. This generates a faster P wave
With sinus tachycardia we should have a normal ____ on the EKG and a short ______
normal looking EKG with a normal P wave
and Short PR interval
What defines Sinus Tachycardia?
HR >100 BPM
What causes ST?
- Increased body temperature
- Reflex stimulation of the heart by the sympathetic system or a loss of stimulation of the vagus system
What toxic conditions did Dr. Smidt mention that increase VRM and can cause ST?
Nicotine
Alcohol
Acidosis
Hyperkalemia
What is the definition of sinus bradycardia?
HR <60 BPM
a normal EKG, just slow
What happens in athletes with a physicological hypertrophy of the heart?
They have a high Stroke volume
Slow heart bc of high stroke volume, don’t need as many BPM
Vagal stimulation to slow down the HR if high HR isn’t needed
What causes sinus bradycardia?
Being an athlete (physiologic hypertrophy)
In general, having a ____ HR is a good thing
Low
If you have a high resting heart rate, your _____ probably isn’t what it is supposed to be
Stroke volume
High resting HR is usually d/t
Hyperthyroidism
Could be a valve problem
Causes for bradycardia
Usually d/t increased vagal
Neural reflex to drugs (increase in HR, baroreceptors see this, phenylephrine increases HR)
Decrease in sympathetic nervous system
Atrial tachycardia that comes and goes
Paroxysmal atrial tachycardia
What does Paroxysmal tachycardia look like in a pt.?
What would cause this?
Sometimes we have normal R-R intervals and sometimes we have fast HR
Something that temporarily blocks vagal stimulus. When the vagus nerve goes back to normal HR goes back to normal
What do the P & T waves look like atrial tachycardia?
T wave goes away, it is hidden under the QRS. They overlap and become indistinguishable.
P wave goes away when the _____
SA node is ischemic
When the SA node is blocked what happens?
The fastest self discharge rate tissue takes over as the pacemaker of the heart
Usually AV node
If AV node isn’t working then
Purkinje fibers take over but gives us a very slow heart rate
If you have a ventricular rate of 20 , what kind of activity can you do?
You can maybe walk around your house but can’t be a professional basketball player
Depending on which part of the AV node is sending out an AP what might happen?
You could have an inverted P wave d/t the AV sending retrograde AP towards the SA node.
What determines if we have an inverted P wave or possibly no P wave at all in relation to sinoatrial block?
Early part of AV node= inverted P wave
Later part of the AV node= retrograde AP takes a while and sometimes it might not be picked up as a negative P wave because electrical activity might be going on in the ventricles that mask the P wave
Why is it that sometimes you have an inverted P wave in sinoatrial block and sometimes you don’t see a P wave at all?
In an AP stimulated in the early part of the AV node it takes a bit for a normal AP to get to the ventricle so it gives the AP time to get to the SA node and provide an inverted P wave but if the AP was stimulated in the later part of the AV node then by the time the retrograde AP hits the SA node, there is electrical activity in the ventricles that mask the inverted P wave.
With all arrhythmias if the timing is off you have a
Decrease in Stroke volume
When the atria contract which valves are open?
The atrioventricular valves(tricuspid & mitral)
so that the atria can prime the ventricles while the ventricles are relaxed
If you have something that causes the ventricles to depolarize early it causes which valves to close?
Why is this a bad thing?
Early closure of the of the atrioventricular valves
Because now the atria contract against a closed valve which causes turbulence.
What does having early closure of the AV valves cause?
causes Damage to the valves and causes them to Calcify
Blood sloshing around and turbulence causes clots
What causes blood clots in the heart?
When atrial contractions are not coordinated with the ventricles. It is like pushing blood into a “brick wall” (closed AV valve) and turbulence results which allows blood to sit and form clots
physiology of a normal AV delay?
A delay at the AV node normally to hold off on firing the ventricles to give the atria time to have a coordinated contraction.
PR interval is .16
>.16 the more the abnormal block.
What causes an enhanced block at the AV node?
- Ischemia= increased VRM
Less voltage ion channels participating in the AP
-we already have slow ion channels here so if VRM gets higher then it takes an even longer period of time for the AP to get through the AV node. - Compression of AV bundle by remodeling after an MI or CHF. Patchwork to prevent the heart walls from blowing out.
If remodeling gets out of control and we have too much scar tissue at the AV node then it can compress the AV node and cause them to have a smaller internal diameter causing increase in resistance = slower AP conduction.
Could be calcifications but usually scar tissue - AV nodal inflammation
- Excessive vagal stimulation (V&X reflex)
- Excess digitalis/beta blockers-impair generation of AP at SA node and reduce speed of conduction at AV node
How does digitalis work?
Inhibits the Na+/K+ pump
Inhibiting the pump =more Na+ in the cell
NCX is a major way Ca++ gets pumped out of the heart cell and it only works d/t Na having a big gradient in the cell
Therefore digitalis results in a slower rate of Ca++ removal. Good if heart is failing as a last resort.
What is a last ditch effort for heart failure?
Digitalis
Why is digitalis dangerous?
It’s messing with something that is very important Na+/K+ pump and VRM.
It works on the Na+/K+ pumps all over the body
PDE inhibitors are not specific to
Just the heart. No absolute specify in any drug.
Incomplete heart block or 1st degree heart block is classified by PR interval being
> 0.20 seconds
Not a true block, it’s just a delay.
Have a P wave in front of every QRS.
Delay from P wave to QRS
2nd degree heart block is classified by
Dropped beats
PR interval increase beyond .25 seconds.
Atria has a faster heart beat than the ventricles in
2nd degree heart block
Mobitz type 1 second degree heart block is classified by:
What is another name for this type of block?
Abnormal amount of time between PR interval
Variable PR interval and sometimes beats are dropped
Wenckebach
“Irregular PR interval on each of the different heart beats”
Mobitz Type 2 second degree heart block is classified by:
Fixed ratio of P to QRS except some beats are dropped after the P wave. Has a fixed PR interval
Which Mobitz type is more dangerous?
Mobitz type 2
When is a pacemaker required in Mobitz type 1
when you get old and decrepit but not required for everyone
When pts haven’t seen the dr in a while and we do an EKG and we sometimes find which heart block?
Mobitz type 2.
Which heart block is cause for a pacemaker?
Mobitz Type 2
P to QRS complex ratio options in Mobitz type 2
P:QRS
2:1
3:2
3:1
Which heart block has some impulses pass through AV node and some do not but is overall very regular
Mobitz type 2
3rd degree or complete heart block is classified by:
Pathophysiology of having so many beats?
R-R interval is consistent
A bunch of random P waves all over the place
Total AV node block, relying on the ventricular escape (15-40 BPM)
Cardiac output is low.
Nervous system sees this and tries to get the heart to increase rate.
Might help the ventricles increase rate a little bit. Also increases the atria rate but AP are not making it past the AV node.
Which heart block has a complete dissociation of QRS from p waves
Complete heart block or 3rd degree
A flutter is defined by:
Circular reentry that is completely separate from the SA node.
A really slow conduction rate in the atria it leads to circular movements that involves the entire atria
What would happen if A flutter AP were at a faster rate?
AP would run into a refractory period which would not allow the conduction to generate an AP. Therefore A-flutter happens at a slower conduction rate.