Arrhythmias and Blocks Flashcards
Where do impulses originate?
The SA node
How do you measure heart rate?
divide 300 by the number of blocks inbetween peaks
When you have a change in frequency (HR) what changes?
Diastolic time (T-P segment) not the systolic time.
This affects stroke volume
Sinus Bradyardia
HR below 60 bpm
T-P segment long
Automacity is lower
Conduction unchanged
All other things on EKG are normal
Sinus Tachycardia
Above 100 bpm
T-P segment is short
Sinus bradycardia and Sinus tachycardia are examples of what?
Supraventricular Normotopic Rhythms
What is Ectopic Arrhythmias?
Excitation starts at an abnormal location
What are the two type of Ectopic Arrythmias discussed in class?
Passive Rhythm or Escape
Active Rhythm or Ectopic Tachycardia
Passive Rhythm or Escape
Norma Rhythm does not reach a area in the heart so it begins to create its own excitation at a lower rate than the SA node
- Latent pacemakers fires (escape)
- Long pause precedes the escape rhythm (straight line seen on EKG)
- Site of Origin limited to latent pacemakers
- Atrial
- AV junctional
- Ventricular
- SA node must be silenced first which creates a pause in your heart
Ative Rhythm or Ectopic Tachycardia
Occurs regardless of SA node
- Active rhythms superimpose on the normal sinus rhythm
- Interval is shorter than normal and higher rate of firing than SA node
- Site of origin:
- Atrial
- AV junctional
- Ventricular
- Abnormal Automaticity of latent pacemaker
- Abnormal conduction: reentry circus
What is the effect of ischemia on conduction?
Ischemia causes depolarization
This causes conduction to decreases and Na+ System becomes inactive
Partial One Way block
This allows for a reentry loop to be created.
Electricity circles back to orifinal area of conductance.
The loop is able to form because the initial cells that were fired recover quickly so they are able to to fire again where as the area that is blocked is not able to fire. Electricity is going to go to area of availability.
When you have a junctional escape beat what is seen on the the EKG?
You no longer have a P wave (atrial depolarization)
Retrograde grade conduction causes what on the EKG?
zig zag line
What occurs when you have a ventricular escape beat?
Ventricles take over
Inverted T wave
QRS is wider
No synchronism
Myogenic Conduction
What are the three type of Ectopic Supraventricular Tachycardias?
Atrial Flutter
Atrial fibrillation
Junctional Rhythm
Atrial Flutter
Impulses travel in circular course in atria, setting up regular rapid flutter (F) waves without and isolectric baseline
- Ectopic site beating at a higher rate
- Asynchronous conduction of AV node to ventricle
- Ventricular contracton not steady
Atrial Fibrilation
Impulses take chaotic random pathways in atria
- Multiple Ectopic Sites creates electricity that bump into each other
- You wont see any significant atrial excitation
- Unsteady Ventricular Contraction
Junctional Rhytm
Impulses originare in AV node with Retrograde and anterograde transmission
- Sometime you may see a inverted T wave but not always
- SA node is still beating sometimes but when Ectopic AV node is diseased = spacing ventricles => retrograde and silencing of the SA node
Ectopic Ventricular Tachycardias
- Ventricular Tachycardia (more than 120 bpm)
- infarct present
- Slowed conduction in margin of ischemic area permits ciruclar course of impulse and reentry with rapid repetive depolarization
- Loop created
- Myogenic contraction
- No P wave or Twave, Wide QRS
- Ventricular Fibrilation
- Chaotic ventricular depolarization
- Multiple ectopic sites in ventricle
First Degree AV Block
Fixed but prolonged PR interval
(more than 260 msec)
less severe
diastolic and systolic are the same
Excitation resides in AV node
(AV node conduction velocity is slower)
Second Degree Block
SERIOUS “ NO PREDICTION/NO WARNING”
-
Mobitz I (Wenchebach)
- Progressice lengthning of PR interval with intermittent dropped beats
- PR interval is normal in the first beat and after the drop
- 4:1 less severe than 2: 1
- L type Ca+ channels are affected (can be stimulated but take a long time to recover from inactivation) -> AP Phase 0 decreases over time
- Occurs at the proximal end of AV node
-
Mobitz II (Non- Wenchebach)
- sudden dropped QRS without prior PR lengthning
- Occurs at distal end of AV node toward septum
Third Degree Block
MOST SEVERE
No relationship between P waves and QRS complexes
QRS rate slower than P rate
- impulses can originate at both SA node (P wave) and below site of block in AV node (junctional rhythm) conducting to ventricles
* damage proximal to AV node so AV node takes over and has its independent wave - Impulsed can originate at SA node (P wave) and also below sithe of block in ventricles (Idioventricular rhythm)
- abdnormal cardiomyocytes takes over
- Myogenic conduction = Wide QRS, inverted T wave (independent of P wave)
Differentiate Arrythmias from Blocks
Arrythmias are related to pacemake activity so it is all about automaticity
Blocks is about conduction
What are the most vunerable areas for Arrythmias and Blocks?
AV node
Bundle of His
Look at powerpont for bundle branch block
