junctional/ventricular/atrioventricular Flashcards
where is the first place to backup or kick in if impulse fails from the SA node?
- the AV junction
are there impulse forming cells in the AV node?
no. but there is in the junctional tissue
what is PJC
Premature Junctional Contraction:
- when impulse-forming cells fires ‘earlier’ than regular interval
will there be a P wave in PJC? explain
Yes. But they will look different from each other (if visible) d/t PJC traveling through atria in different manner
depolarization starts at the AV junctin and proceeds from there
3 key facts for PJC atrial depolarization and P waves
- P wave represents atrial depolarization NOT SA node depolarization
- Impulses arising in the AV junction will create atrial depolarization
- P waves associated with junctional rhythms (like PJC’s) can occur in different shapes or may be hidden in other parts of the ECG waveform
The P wave of a PJC can appear in three ways:
- inverted - from junction, if wave goes to the atria first and then to vents, you will see inverted P wave preceding QRS (inverted d/t atrial depolarization occurring in retrograde manner)
- Buried in QRS complex - if depolarization goes into the vents and the atria at the same time, then the P wave is usually buried in the QRS complex.
- Occur after the QRS complex - if the vents are depolarized before the atria, then P wave usually occurs after QRS
What happens to the PR interval in a PJC?
- the location of the P wave impacts the PR interval bc if the impulse originates at the AV junction the distance to travel to atria is less than normal (0.12 sec) and would precede the QRS
PJC’s can occur as?:
single isolated beats or as clusters/groups
what is JER?
Junctional Escape Rhythm
- when a secondary site in the junctional tissue takes over role of impulse formation: usually occurs when the primary pacemaker site in the SA node fails
what is a normal rate for JER? what if it is greater than normal?
Normal 40-60 BPM
If greater than Accelerated Junctional Rhythm
explain the P wave in a JER:
- similar to PJC, the impulse at the junctional tissue will depolarize in a retrograde manner
- the P wave will be inverted, buried or after a QRS
what does the QRS look like in JER?
It appears normal
bc the wave of depolarization follows the normal pathway after it leaves the junction
what does the interval and rhythm look like in JER?
the R-R is constant and rhythm is regular
JER
conduction prob:
- prob with the SA node
- is the rate sufficient to meet the PTs needs.
- it is similar to sinus brady
- assess PT to determine their response
JER
cause
whatever caused the SA node to fail
JER
implication to O2 supply and demand
The impact the rhythm has on CO
- Slow HR
- Loss atrial kick
JER
intervention
assess PT
IF CO compromised by rhythm then atropine
if no response then temporary transvenous pacemaker
JER
Rate Rhythm P wave PR interval QRS complex
rate: 40-60
rhythm: reg
P wave: before, during or after QRS (if visible, may be inverted)
PR: if present 0.12 sec or less
QRS: 0.10 sec or less
what is the difference between Junctional Tachycardia and Junctional Escape rhythm and Accelerated Junctional Rhythm?
The rate of firing of junctional focus
JT = > 100 / min
JER = 40-60
AJR = 60-100
which rhythms depolarize in retrograde fashion?
JER, PJC and JT
then conduction through the vents are normal
Junctional Tachy
conduction problem
junctional tissue around AV node
Junctional Tachy
Cause
whatever caused SA node to fail allowing junctional tissue to take over
dig. tox, MI, HF…
Junctional Tachy
Intervention
assess PT
If CO compromised by rhythm, treat cause
amiodarone, BB, CCB, ablation
What is SVT and which dysrhythmias are in the category?
Dysrhythmias with fast rate whose site of impulse formation is above the vents.
- Atrial fibrillation
- Atrial flutter
- Atrial Tachycardia
- Junctional Tachycardia
sinus tachy, multifocal atrial tachy
SVT criteria
- No defined P wave
- vent rate > 150 (meaning impulse not originates from SA node
- QRS complex is normal ( 0.10 sec or less) means that normal pathway from AV node, so not originating from vents. So atria or junctional
When are ventricular rhythms fast?
When irritable focus or multiple foci ‘take over’ from pacemaker site ‘higher up’ in the conduction system (ex. override pacemaker sites in SA node or junctional tissue)
When are ventricular rhythms slow?
When SA node or AV junction pacemaker sites fail (or completely blocked), and pacemaker site in the conduction system below the AV junction assumes the pacemaker role
unifocal and multifocal PVC?
same and more than one abnormal focus.
ventricular bigeminy
every second beat is a PVC
vent trigeminy
every third beat is a PVC
Couplet
2 PVC’s together
Triplet
3 PVC’s together
Run
more than 3 PVC’s together
post cardiac arrest management: induced therapeutic hypothermia is for?
PTs who have been resuscitated from cardiac arrest associated with vent fib and pulseless vent tachy but DO NOT gain some level of consciousness post-defib
what is induced therapeutic hypothermia?
deliberately cooled to goal core temp of 32-34C
target being reached in 4 hours of return of spontaneous circulation (ROSC) ex. a perfusing rhythm
why induced therapeutic hypothermia?
> out of hosp cardiac arrest survivors have high incidence of significant, permanent neurological deficit from cerebral edema and other neurological damage resulting from hypoxia and brain anoxia
> ischemia result in loss of cell membrane integrity and increased permeability, electrolyte shifts and metabolic acidosis = temp or permanent change in neurological function
what is the goal of induced therapeutic hypothermia?
focus on blocking or minimizing the destructive processes that arise from cellular anoxia (complete absence of O2; severe hypoxia)
process of induced therapeutic hypothermia
hypothermia blankets or ice packs. NS cold lavage may be used
- PT kept cool for 12-24 hours before controlled warming
- rewarming goals = increasing temp by 0.2C to 0.5C/hour is important to avoid negating the therapeutic effects gained by hypothermia period
specific criteria for induced therapeutic hypothermia:
- primary dysrhythmia: Vent fib or V. tach
- time from collapse to ACLS (advance cardiac life support) < 15 min
- Time from collapse to ROSC (return of spontaneous circulation) < 60 min (pulse and BP present)
- adult > 18
- persistent GCS < 10
these things will exclude PTs from induced therapeutic hypothermia:
- pregnant
- Hx of terminal illness
- improving neurological status (making purposeful movements)
- coma/arrest secondary to non-cardiac factors
- persistent hypoxia (SaO2 < 85% for > 15 min)
- significant coagulopathy
- hemodynamic instability despite vasopressors: MAP < 60mmHg for > 30min
clinical significance of AV block depends on: 3
- degree (severity ) of block
- rate of secondary pacemaker
- PTs response to the ventricular rate
If there is a pacemaker spike on the ECG strip not followed by a contraction complex what are you seeing? Failure to
Capture
The 3 letters in the pacemaker code stand for what in the appropriate order?
a. Chamber paced, sensed, how to respond to a sensed event
what is failure to pace?
failure to fire- complete lack of pacemaker activity. no spike.
spike/response - spike/response - no spike/no response - spike response
could be battery, circulatory, leads, disconnect…
what is failure to capture?
when electrical impulse is emitted from the generator but fails to depolarize the myocardium.
Spike but no response**
you see a pacemaker spike on ECG that is NOT followed by appropriate ECG waveform (atrial or vent response)
caused: anything that makes it more diff for the electrical impulse from the pulse generator to cause depolarization of cells (transvenous/electrode wires out of position**, voltage too low, metabolic acidosis, electrolyte imbalance, myocardial ischemia).
check connections and strength of electrical discharge: reposition PT**, increase output setting, review for PT related issues, contact MD
what is failure to sense?
** pacemaker spikes that fall where they shouldn’t. Anywhere in the cycle**
- oversensing–> when pacemaker senses extraneous (non-cardia) electrical signals. (muscle tremors) that lead to pacemaker being inappropriate inhibited or triggered
- undersensing–> if the sensitivity setting is such that a larger electrical activity needs to be generated in order for the pacemaker to recognize it, then good possibility that PTs intrinsic activity will not be recognized or sensed. can be life threatening
- If Pacemaker doesnt know that there is intrinsic activity, it will continue to fire, emitting electrical activity to PTs heart. can cause life-threatening dysrhythmia
- recognize- spike may occur in the middle of QRS
For arrhythmias would you need a pacemaker? 5
- sinus brady
- sinus arrest/block
- JER
- VER
- AV blocks
what is the diff btwn atrial and junctional tachy?
Atrial might not have any P waves because they might be hidden in the QRS.
Junctional will have inverted or weird P waves
Chamber paced:
Where it creates impulse
0= none A = atrium V = vents D = Dual
Chanmber sensed:
senses intrinsic electrical activity
0= none A = atrium V = vents D = Dual
Response to sensing:
denotes what the pacemaker will do
0 = none T = triggered I = inhibited D = dual (applies to permeant)
Most common mode of vent pacing?
VVI = ICU
asynchronous contraction of the atria and ventricles =?
loss of atrial kick with ventricular filling. = decreased CO
If the lead is placed in the atria…
you will have a spike and then P wave followed by QRS
If the lead is placed in the vent you will see
no p wave, spike and wide bizarre QRS
if you see a pacemaker spike not followed by a P wave or QRS that means?
failure to capture
difficult for the electrical impulse from the pulse generator to cause the cells to depolarize. These can be patient-related issues such as acidosis, electrolyte imbalance, and myocardial ischemia,
reposition pt so lead closer to the surface of the heart
The 4th beat is the patient’s intrinsic beat. Close after that, we can see a pacer spike
Failure to sense. doesnt sense the PTs intrinsic beat and fires after
decrease mV setting
If there is a pacemaker spike on an ECG strip not followed by a contraction complex what are you seeing?
failure to capture
What pacemaker setting most mimics the normal heart activity thereby maintaining the closest CO as a healthy heart would?
DDD - 4 morphologies
In a synchronous pacemaker, failure to sense is represented on an ECG rhythm strip by
a pacemaker spike not followed by a contraction/complex
sensed activity…
inhibits pacing
if 100% vent paced you cannot…
have the ability to assess sensed
In a synchronous pacemaker, failure to sense is represented on an ECG rhythm strip by
A spike in the presents of intrinsic activity
which rhythms need cardioversion as interventions?
- uncontrolled A.fib
- A. flutter
- vent tachy
which rhythms need pacemaker?
- JER
- Blocks
- Bradycardia
with what rhythms do you defibrillate?
anything with no pulse
- Vent fib
- pulseless vent tachy
- SVT (A. fib, A flutter, A. tach, J tach)
why does the Dr. perform and carotid massage?
to stimulate the vagus nerve to decrease the HR
decrease AV conduction rate
cardioversion timed with?
R wave. Avoid T wave timing to avoid refractory period of the cycle. The machine searches for QRS and flags it
R on T can cause? V. tach
what do you need to remember for vent tachy?
ACLS Too fast:
wide QRS
is there a pulse or no pulse?
pulseless- ABC, code, IV, intubate, defib/CPR**, EPI* (also applies for pulseless Vent Fib)
pulse- stable? = drugs (Adenosine, Amiodarone, BB, CCB)
Pulse unstable = cardioversion
what is the difference between defibrillation and cardioversion?
Defib is done with pulseless and is non-synchronized
Cardiovert- with pulse, synchronized with R waves
ACLS too slow:
: SB, Junctional escape or Brady, VER, 2AVB, 3AVB
Stable: monitor
Unstable: drugs = atropine, dopamine, Epi
: pacemaker
When you see a PVC, what is the meaning of the ST?
because they are from the vents they are abnormal so the ST is not significant
paroxysmal SVT
starts and stops abruptly. It will go away and the PT is fine
1st degree considerations:
1P:1QRS
Sinus Rhythm with PR prolonged, but constant
2nd degree type 1 considerations:
PR lengthens and then drops
When drops there is an extra P and no QRS
2nd degree type 2 considerations:
More P than QRS’s
PR prolonged but will be the same length for all complexes
3rd degree considerations:
QRS is wider > 0.12 if from vents, or narrow if from below junction. influenced by site of AV block
P-P is regular and R-R is regular
** there is no relationship between P’s and QRS’s
Does ST matter in heart blocks?
Depends where QRS is coming from.
If narrow = from junction then it matters
If wide = from ventricles/purkinji then does not matter
Any rhythm can be a PEA except…
VT, VF and asystole
which meds slow the HR?
stable PTs:
unstable PTs:
for stable PTs:
For narrow and wide QRS (A.tach, A. fib, JT…. VT)
- Amiodarone (Na, K, BB, CCB)
- Adenosine
unstable:
cardiovertion
which meds are used to speed up HR?
unstable PTs:
stable:
for unstable PTs:
(SB, junctional, VER, 2AVB, 3 AVB)
- Atropine
- Dopamine
- Epi
Stable: monitor
what can you give to no pulse, asystole, and PEA?
Epinephrine
