Module 1 Rhythms (lect 4-6) Flashcards
Checklist for analyzing rhythm of an ECG
1) P before each QRS
2) QRS after each P
3) PR intervals (for AV blocks)
4) QRS interval (for bundle branch blocks)
Arrhythmia vs. dysrhythmia (is there a difference?)
Interchangeable words; both denote an Abnormal rhythm therefore, no difference
Sinus Arrhythmia
NORMAL!!!!!!
Barely detectable rate changes in sinus pacing in relation to the phases of respirations
NOT A TRUE ARRHYTHMIA
INCREASE in heart rate during INSPIRATION
DECREASE in heart rate during EXPIRATION
Define Automaticity
Ability to inherently generate a regular cadence of depolarization
What are the 3 levels of automaticity and what is the purpose?
- Atrial Foci & Junctional Foci (adrenaline, increased sympathetic, cocaine, caffeine and amphetamines, hyperthyroidism, low O2)
- Ventricular Foci (low oxygen; low potassium, ischemia, cocaine)
Purpose: back-up pacemakers in case the SA node fails
What are the rates (BPM) for the difference levels of automaticity?
- Atrial Foci = 60-80 BPM
- Junctional Foci = 40-60 BPM
- Ventricular Foci = 20-40 BPM
***should the highest pace-making center fail, an automaticity focus from the next highest level emerges or “escapes” to start pacing
What are the three Irregular Rhythms?
- Wandering Pacemaker
- Multifocal Atrial Tachycardia
- Atrial Fibrillation
Criteria for Wandering (Atrial) Pacemaker
P’ (p-prime) wave represents atrial depolarization by an automaticity focus
- Heart rate is below 100 BPM
- Is a Multifocal Atrial rhythm (originating from the atria)
- It will have at least 3 different P-wave morphological
- The pacemaker site shifts between the SA node, Atria and AV node
Underlying etiology for Wandering Atrial Pacemaker
Irregular rhythm produced by the pacemaker activity wandering from the SA Node to nearby atrial automaticity foci.
Caused by vagal tone (effect produced on the heart when only the parasympathetic nerve fibers (carried by the vagus nerve) are controlling the heart rate
Can also be caused by COPD. If the heart becomes tachycardia, then WAP will become MAT.
Criteria for Multifocal Atrial Tachycardia (MAT)
- SA node is not pacing the heart
- Several groups of excitable cells in the atria compete to pace the heart
- MAT has at least three or more different shaped P-waves
- MAT is an irregular rhythm above 100 BPM
- MAT has irregular P-R, R-R, and P-P intervals
Underlying etiology for Multifocal Atrial Tachycardia
Underlying “sick” heart which develops resistance to overdrive suppression leading to all Foci to pace together = atrial rate > 100 bpm
MAT is common with underlying chronic obstructive pulmonary disease (COPD) which strains the heart
Criteria for Atrial Fibrillation
Continuous rapid-firing of multiple atrial automaticity foci (CHAOS) - looks like speed bumps between each QRS complex
Irregular QRS rhythm
RAPID pacing of an unhealthy heart
Irritable atrial foci
No discernable P waves because the atria fail to depolarize completely
Underlying etiology for Atrial Fibrillation
NOT an arrhythmia of healthy, young individuals. IT is the result of multiple “irritable”atrial foci, suffering from entrance block, pacing rapidly. These multiple atrial foci are parasystolic, so they’re all insensitive to overdrive suppression; therefore, they all pace at once
What does ESCAPE describe?
Response of an automaticity focus to a pause in the pace-making activity
Describe Escape Rhythm and what are the three types?
A pause in SA node pacing permits an automaticity focus to ESCAPE overdrive suppression
- Atrial Escape Rhythm
- Junctional Escape Rhythm
- Ventricular Escape Rhythm
This occurs when the SA node stops pacing entirely
Describe Escape Contraction and what are the three types?
An automaticity focus transiently escapes overdrive suppression to emit one beat.
- Atrial Escape Contraction
- Junctional Escape Contraction
- Ventricular Escape Contraction
This occurs when the SA node stops pacing briefly (only one cycle missed)
Contraction = one beat Rhythm = longer period
Discuss Sinus Arrest
Occurs when a “sick” SA node stops pace-making completely
The automaticity foci provide “backup” pacing
Extremely long pause between R-R with a BPM less than 50
Describe Escape Rhythm and what are the three types?
An automaticity focus escapes overdrive suppression to pace at its inherent rate.
- Atrial Escape Rhythm
- Junctional Escape Rhythm
- Ventricular Escape Rhythm
This occurs when the SA node stops pacing entirely
Atrial Escape Rhythm
A cardiac dysrhythmia occurring when sustained suppression of sinus impulse formation causes other atrial foci to act as cardiac pacemakers. Rate = 60-80 BPM, p wave of atrial escape has abnormal axis and different from the p wave in the sinus beat. However, QRS complexes look exactly the same
Junctional Escape Rhythm
Depolarization initiated in the atrioventricular junction when one or more impulses from the sinus node are ineffective or nonexistent.
Rate: 40-60 BPM
Irregular rhythm in single junctional escape complex; regular in junctional escape rhythm
P waves: depends on the site of the ectropic focus. They may be inverted and may appear before or after the QRS complex or they may be absent, hidden by the QRS. QRS is usually normal
Idioventricular (Escape) Rhythm
When the ventricles are not stimulated, the automaticity center escapes overdrive suppression to become a ventricular pacemaker
Rate: 20-40 BPM (almost not compatible for life)
Most common mechanism of action for ventricular escape rhythm
Complete conduction block high in the ventricular conduction system below the AV node
Rare mechanism of action for ventricular escape rhythm
Failure of the SA node to fire and the atria to fire (everything is shutting down)
Atrial Escape Contraction
A transient sinus block (SA node misses ONE CYCLE)
Atrial automaticity takes over (or escapes overdrive suppression) and emits a beat
P’ wave differed from P waves generated by the SA node
Looking for a long pause, then a jacked up P’ wave, and then back to normal contractions
Junctional Escape Contraction
If both the SA node and atrial foci fail to pace one cycle, a junctional automaticity focus will escape overdrive suppression
Normal ventricular conduction: normal QRS Complex
After one beat, the SA node takes over as the dominant pacemaker and suppresses the junctional focus
A single junctional escape beat may produce a retrograde atrial depolarization that records as an INVERTED P’ wave either before or after the QRS complex
Ventricular Escape Contraction
A ventricular automaticity focus takes over as pacemaker
Produces a LARGE QRS complex
Premature Contractions
An irritable focus spontaneously fires a single stimulus. Produces a contraction (depolarization) earlier than expected in the rhythm
Premature Atrial Contraction
Originates in an irritable atrial automaticity focus; P’ wave earlier than expected. P’ wave looks different than the sinus-produced P wave
How does Reset Pacing work?
Resetting allows the dominant pacing stimulus to generate another contraction one cycle length from the premature contraction
Resetting occurs when the dominant center of automaticity (SA node) is depolarized by the premature contraction
How does reset pacing not reset?
The depolarization from the premature contraction does not reach the dominant pacing center
What resets a premature contraction?
A center of automaticity resets the rhythm when it is depolarized by a premature contraction
Atrial Bigeminy
When an irritable automaticity focus fires a premature atrial contraction (P’) that couples to the end of a normal cycle and repeats
Define Couplet
The cycle containing the premature contraction + normal cycle
Atrial Trigeminy
When an irritable atrial focus prematurely fires after 2 normal cycles and the couplet repeats continuously
Premature - normal - normal - premature - normal - normal….
Premature Junctional Contraction
Occurs when an irritable automaticity focus in the AV junction suddenly fires a premature stimulus that conducts to and depolarized the ventricles
AV node prematurely stimulates the ventricles
AV node=AV junction=junctional contraction
T wave into QRS (no P wave)
Junctional Bigeminy
An irritable focus in the AV node initiating a premature junctional contraction after each normal cycle
May note inverted (retrograde) P’ waves with every premature junctional contraction
Junctional Trigeminy
When a premature junctional contraction is coupled with 2 consecutive, normal cycles in a repeating series of couplets
Premature Ventricular Contraction (PVC)
Originates in an irritable ventricular automaticity focus
Produces a LARGE QRS complex
LARGE QRS followed by a COMPENSATORY PAUSE
Define PVC Compensatory Pause
NOT caused by resetting of the SA node
The SA node depolarized but the ventricles are still refractory from the PVC
This results in a pause as the ventricles finish repolarizing
Ventricular Bigeminy
When a PVC becomes coupled to a normal cycle and the pattern continues with every cycle in succession
Ventricular Trigeminy
A repetitive pattern of a PVC coupling with every 2 normal cycles
Runs of PVCs
Occurs when an irritable ventricular automaticity focus fires a rapid series of impulses
DANGER: a run of 3 or more PVCs in rapid succession = Ventricular Tachycardia (VT)
Low serum potassium, poorly oxygenated blood
Multifocal PVCs
PVCs produced by multiple, irritable ventricular foci
Leads to QRS complexes that appear DIFFERENT since each foci produces its own unique PVC
Tachyarrythmia
Rapid rhythm originating in irritable automaticity foci
Sometimes more than one active focus is generating pacing stimuli at once
Tachyarrythmia Rates
- Tachycardia (not sinus; atrial, junctional or ventricular) = 150-250 BPM
- Flutter = 250-350 BPM
- Fibrillation = 350-450 BPM
Paroxysmal Tachycardia (3 types)
Atrial, Junctional and Ventricular Tachycardias
An irritable focus SUDDENLY paces rapidly
How does sinus tachycardia differ from paroxysmal tachycardia?
Gradual Response or NO automaticity focus
Atrial Tachycardia
Caused by sudden, rapid firing of irritable atrial automaticity focus
Rage: 150-250 BPM
Overdrive suppresses the SA node and all other automaticity foci
P’ waves do NOT look like P waves
(He said it won’t be on the exam but who the fuck knows the truth)
Junctional Tachycardia
Caused by the sudden rapid pacing of an irritable automaticity focus in the AV junction
Rate: 150-250 BPM
AV node hyperstimulation
AV Nodal Reentry Tachycardia (AVNRT)
A type of junctional tachycardia
A theoretical “re-entry circuit” continuously circles through the AV node depolarizing the atria and ventricles
Supraventricular Tachycardia (SVT)
Atrial Tachycardia OR Junctional Tachycardia
Both originate above the ventricles (supraventricular)
Ventricular Tachycardia (absolutely must be able to identify this)
Produced by an irritable ventricular automaticity focus
Rate: 150-250 BPM
LARGE, consecutive PVC-like complexes
Caused by coronary disease or infarction;
How does Ventricular Tachycardia work?
One of the regular atrial depolarizations (from the SA node) finds the AV node receptive to depolarization
The AV node subsequently depolarized the ventricles via the ventricular conduction system
This leads to normal QRS complexes in the midst of large QRS complexes produced by the irritable ventricular automaticity focus
Torsades de Pointes
A form of ventricular tachycardia
POLYMORPHIC (many shapes) QRS complexes
Rate: 250-350 BPM
“Twisting of Points”; two competitive irritable foci in different ventricle areas
Caused by low potassium or medications that block potassium channels
Atrial Flutter
An irritable atrial automaticity focus produces a rapid series of atrial depolarizations
Rate: 250-350 BPM
“FLUTTER” waves describe as “SAW TOOTH”
Because the AV node takes long time to repolarize, only a few atrial depolarizations reach the ventricles = MANY more P waves than QRS complexes
Ventricular Flutter
Caused by a highly variable irritable ventricular focus; coronary arteries are not receiving blood flow. Leads to ventricle Fibrillation
Rate: 250-350 BPM
QRS look smooth and have a SINE-WAVE pattern
QRS are of similar amplitude
Define Fibrillation
Caused by rapid discharges from numerous irritable automaticity foci in the atria or ventricles
Erratic and uncoordinated rhythm; Waves are not distinguishable
Rates are difficult to determine and the “range” is 350-450 BPM
Atrial Fibrillation
Caused by many irritable atrial foci firing rapidly
Produces rapid, erratic atrial rhythm
Rate range 350-450 BPM
Only a small portion of the atria is depolarized by any one discharge which leads to few depolarizations leading to the AV node
AV node does not receive many depolarizations which means there are few ventricular depolarizations = NO discernable P waves AND IRREGULARLY IRREGULAR ventricular rhythm
Ventricular Fibrillation
Due to numerous ventricular foci pacing rapidly causing an erratic twitching of the ventricles
Numerous ventricular foci firing leads to ineffective twitching of the ventricles
DANGER: ERRATIC, NO IDENTIFIABLE WAVES
350-450
Wolf-Parkinson-White Pattern
An abnormal, accessory (extra) AV conduction pathway called the bundle of Kent
“Short circuits” the delay of ventricular conduction in the AV node
Leading to premature depolarization of the ventricles just before normal AV node-induced ventricular depolarization begins
Pre-excitation syndrome. Ventricles are stimulated before (pre) normal depolarization
Criteria for Wolff-Parkinson-White Pattern
SHORTENED PR interval indicates pre-excitation (ventricles start contracting sooner because of the extra pathway)
DELTA WAVE also indicating earlier ventricular contraction
WIDENED QRS complex
INVERTED T wave because of different focus of depolarization from the accessory pathway
