Fall Quiz 2 Flashcards
What is the difference between a compensatory and non compensatory premature beat?
A compensatory premature beat will have QRS complexes that march out evenly before and after the pause.
What is a premature beat?
When an irritable ectopic focus fires prematurely.
What is an escape beat?
When the SA node doesn’t fire at its regular interval and an ectopic focus fires.
What is a reentry circuit?
A group of cardiac cells that depolarize in a circular pattern that is rapid and repetitive.
What is the underlying mechanism of most tachydysrhytmias?
Reentry circuits
What are the 2 types of reentry circuits?
Macroentry & Microentry
This refers to the amount of tissue that is affected by the circuit.
List the 3 conditions necessary to establish a reentry circuit.
- Two separate parallel paths of impulse conduction.
- Slowed conduction or complete unidirectional block in one of the pathways.
- The right timing of the absolute refractory period.
What is Wolf Parkinson White Syndrome? (WPW)
A macroreentry pathway where an accessory pathway provides secondary access to the ventricles.
List 6 types of Atrial Rhythms.
W: Wandering atrial pacemaker (WAP) E: Ectopic atrial tachycardia (EAT) A: Atrial Fibrillation (AFib) P: Premature atrial contraction (PAC) M: Multifocal atrial tachycardia (MAT) A: Atrial Flutter
Explain WAP
- Regular to irregularly irregular
- Wandering Atrial Pacemaker
- Pacemaker shifts between multiple foci (impulse origins)
- must have at least 3 different p-wave morphologies
- normal rate (60-100)
- normal QRS (less than 0.12)
Explain MAT rhythm.
- Regular to irregularly irregular
- Multifocal Atrial Tachycardia
- Tachycardic version of WAP
- 3 different pwave morphologies
- Less common than, and easy to confuse with AFib
- look for inverted pwaves to differentiate from AFib
Explain PAC rhythm.
- Premature Atrial Contraction
- Results from premature discharge of an ectopic atrial focus.
- characterized by a premature abnormal pwave.
- pwave may be buried in twave.
List 3 causes of PAC
Caffeine
Sympathomimetics
Hypoxia
What is a nonconducted PAC
It is a premature atrial contraction from an ectopic focus that is not transmitted through the AV node, resulting in a premature pwave with no corresponding QRS.
Explain EAT rhythm.
- Ectopic Atrial Tachycardia
- regular rhythm
- results from increased automaticity from an ectopic atrial focus or microreentry circuit.
Explain AFib.
- Atrial fibrillation
- caused by many irritable atrial foci firing at once, causing chaos.
- only some impulses are transmitted through the AV node resulting in irregularly irregular rhythm.
- PRI: non-existent
- QRS: <0.12
List some etiology of AFib.
- Atrial enlargement
- Age
- Pericarditis
- Coronary artery disease
- MI
- hypertension
- Alcohol abuse
List 2 problems associated with chronic AFib.
- Reduced cardiac output
* blood clots formed in the atria can lead to embolism or stroke
Explain Atrial Flutter
- rapid discharge of single ectopic focus causing atrial rate of 250-500 (usually 300)
- usually a regular rhythm
- is an example of a macro-reentry circuit
- rare - usually converts on its own.
Name the 4 junctional rhythms.
PJC: Premature Junctional Contraction
Junctional rhythm
Accelerated junctional rhythm
Junctional tachycardia
Describe what junctional p-waves look like.
No p-wave or inverted p-wave and occasionally retrograde
p-waves.
Describe a PJC.
Premature junctional contraction.
Caused by a premature discharge of an ectopic focus in the AV node.
Absent, inverted, or retrograde p-waves.
Usually a regular underlying rhythm.
Explain junctional rhythm.
Rhythm that originates in the AV node as the SA node has either slowed or failed. Rhythm: regular Rate: 40-60 P-waves: absent, inverted or retrograde QRS: narrow
What is accelerated junctional rhythm?
Same as junctional rhythm with a rate of 60-100
What is junctional tachycardia?
Same as junctional rhythm with a rate over 100
Describe AVNRT
AV node reentrent tachycardia
About 10% of population have 2 pathways through the AV node
Sometimes a reentry circuit develops if the conditions are right
*regular
*very rapid
*no discernible p-waves
*narrow QRS
Describe AVRT.
AV reentrant tachycardia
Can occur when an accessory pathway connects the atria and ventricles
WPW (wolf Parkinson white) is the most common
List the 4 rhythms that are very difficult to tell apart and that (for this class) are referred to as SVT (supraventricular tachycardia)
EAT: ectopic atrial tachycardia
Junctional tachycardia
AVNRT
AVRT
What is the general formula for Determining a patients natural maximum heart rate (sinus heart rate)?
220-age.
This formula can help determine between SVT and sinus tach
How do you differentiate an inverted junctional p-wave from an inverted atrial p-wave?
PRI less than 0.12 is considered junctional.
PRI longer than 0.12 is considered atrial.
By definition, where do all ventricular rhythms originate?
In the ventricles, below the bundle of His
Describe ventricular QRS complexes?
They are ALL wide
Define and describe a PVC
Premature Ventricular Contraction
- results from an ectopic focus in the ventricles
- no p-wave
- wide QRS, often distorted or bizarrely shaped
What is the difference between a unifocal and Multifocal PVC?
Unifocal have the same focus, Multifocal have numerous foci.
What is bigeminy? Trigeminy?
Bigeminy: when every other beat is a PVC
Trigeminy: when every 3rd beat is a PVC
Name 6 etiology of PVC’s
Sympathomimetics Hypoxia Caffeine Idiopathic Myocardial ischemia Electrolyte imbalance
What are the characteristics of Ventricular Escape Rhythm?
Rhythm: regular Rate: less than 40 P-waves: none PRI: none QRS: wide, sometimes bizarre
List 3 etiology of ventricular escape rhythm
Damage to higher pacemaker
Complete heart block
First successful rhythm following defibrillation
What is accelerated Ventricular rhythm?
Same as ventricular rhythm with a rate of 40-100
Describe ventricular tachycardia
Rhythm: regular or slightly irregular
Rate: greater than 100-250
List 4 vtach etiology
Acute MI Myocardial ischemia Electrolyte imbalances Acid base disturbances **nearly all vtachs occur because of micro reentry circuits due to slow or non-conducting tissue
What is Torsades de Pointes?
A polymorphic vtach
Frequently occurs in the setting of prolonged QT
Treated with mag sulfate
Why is prolonged QTI problematic?
Because of the excessive relative refractory period.
Describe Vfib.
Completely chaotic electrical activity in the ventricles.
Always pulseless.
Name 5 etiology of Vfib.
MI Hypoxia Electrolyte imbalances Electrical shock Drugs
Describe asystole.
No electrical activity
Final ECG in all deaths
Describe bundle branch blocks.
Must originate supraventrically
Wide QRS
Can be identified generically in lead II
12-lead needed to differentiate the side of the block
What type of pacemaker only fires when the intrinsic ones fail?
A “demand” pacemaker
Define the term “ventricular capture”
When a pacemaker spike is followed by a wide QRS
Define “intrinsic beat”
A beat from the hearts own rhythm.
Define a fusion beat.
A complex formed when a paced beat fires simultaneously with an intrinsic beat.
