Electrophysiology Flashcards
What is syncytium?
A functional unit of contraction
Why does current conduct easily though originating syncytium?
Tight intracellular junctions
What is between the atrial syncyctium and the ventricular syncyctium?
A fibrous non-conductive layer
What predicts/shows automaticity?
Phase 4
-spontaneous upward drift
Why is there a delay at the AV node?
Allows atria to empty before ventricular contraction
What is the connective tissue that allows the signal to pass the fibrous non-conductive layer?
Atrioventricular bundle
AKA Bundle of His
What is absolute refractory period?
When no stimulus, no matter the size will excite muscle
What time does absolute refractory correspond with?
Depolarization
What is relative refractory?
Time when muscle does not respond to normal stimulus, but will to a strong stimulus
What causes refractory times?
Conformation changes in the Na+ channel to inactivated state
Which electrical therapy has less joules, cardioversion or defibrillation?
Cardioversion
When does cardioversion deliver shock?
During QRS
What rhythms respond to cardioversion?
Afib
A flutter
V tach
Why is cardioversion delivered on QRS?
Less chance of inducing more lethal dysrhythmia
With what other treatment does cardioversion carry an increase risk of producing worse dysrhythmia?
Digoxin toxicity
What risk does cardioversion of atrial fibrillation carry?
Embolization of atrial thrombi
What is usually done to prevent atrial thrombi embolization for cardioversion of Afib?
Heparinization
When is heparinzation for cardioversion of Afib not needed?
New onset
What medication(s) are usually used for cardioversion?
Methohexital
Propofol
What rhythms is defibrillation used for?
V fib
Pulseless V tach
First degree HB treatment?
Rarely needs treatment
Second degree type I HB treatment?
Usually transient, rarely needs treatment
Second degree type II HB treatment?
Greater risk of progression to completely HB
-consider prophylaxis pacemaker
What is the output of a pacemaker, and it’s units?
The strength coming from the device
Measured in mili-amps (MA)
What is the sensitivity of a pacemaker?
The sensing of intrinsic (patient’s) activity
What rhythms is a permanent pacemaker used for?
Bradycardia
Heart block
Sick Sinus Syndrome
What does a magnet do to a permanent pacemaker?
Converts pacemaker to an asynchronous pace
-paces at a set pace no matter what
What is a (minor) concern with Succinylcholine and a pacemaker?
Muscle fasiculations may be sensed as cardiac activity
What is done to help minimize interference with electrocautery and pacemakers?
Grounding pad placed far from heart
Use low setting and short bursts
Bipolar bovie is preferred
What is the pacemaker code?
Chamber paced
Chamber sensed
Response of device
What is asynchronous mode?
Devices paces at set rate no matter what
VOO
What is demand mode?
Devices senses intrinsic activity and responds appropriately
VVI
What is AV sequential pacing?
Dual chamber pacing
What is meant by output on pacemaker?
MA
Causes the spike
What is meant by output failure? Fix?
No pacing spike seen
Turn up MA
Reposition lead
What is meant by sensitivity with pacemaker?
The ability to detect patient’s intrinsic cardiac activity
What is meant by capture with a pacemaker?
Capture is the appropriate waveform after a pacing spike?
What is meant by failure to capture? Fix?
Pacing spike seen, but no waveform follows (MA is less than threshold)
Turn up MA
Reposition lead
What is meant by failure to sense? Fix?
Pacemaker fires when it should not
-not detecting intrinsic activity when it occurs
Need to increase sensitivity
How is sensitivity increased on a pacemaker?
Setting changed to a lower number (this increases sensitivity)
What is an AICD?
Automatic implantable cardiac device
-defibrillator
Who is an AICD used on?
Patients with repeated ventricular dysrhythmia that is unresponsive to drug therapy
What does an AICD do?
Diagnoses rhythm and delivers shock if/when needed
What are the precautions with an AICD?
Same as pacemaker
During implantation of an AICD, what should anesthesia avoid giving to the patient?
Meds that will inhibit induction of lethal dysrhythmias to test AICD function
-lidocaine
What is done during surgery when patient has an AICD?
Rep will/can turn off device
Magnets don’t deactivate them all
What is sick sinus syndrome?
Aging and wearing out of the SA node
What s/sx are often seen with SSS?
Bradycardia is common Tachycardia is possible Syncope Palpitations Can be asymptomatic
What is the treatment for SSS?
Permanent pacemaker
May need SVT suppression meds as well
What is pre-excitation syndrome?
An abnormal accessory pathway that bypasses the AV node
What occurs do to this bypass of the AV node?
Signal arrives to the ventricle without delay
Refractory times occur in different areas
Dysrhythmias in the ventricle
What is the most common pre-excitation syndrome?
Wolf Parkinson White
What is the name of the accessory pathway in Wolf Parkinson White?
Kent’s bundle
What kind of symptoms with patient’s with Wolf Parkinson White have?
Paroxysmal supraventricular tachycardia
-sudden on set of high HR
Sudden death
What is the treatment for Wolf Parkinson White?
Cardioversion
Procainamide
Surgical ablation
What should NOT be given to patients with Wolf Parkinson White? Why?
Verapamil
Digoxin
Dysrhythmia made worse
What is the goal with patients with pre-excitation syndrome?
Avoid dysrhythmia Reduce SNS stimulation -SNS stimulation increases conduction -adequate depth -avoid ketamine -CV stable NMB use
It is okay to use anticholinergics to reverse NMB when patient has pre-excitation syndrome?
Yes in appropriate dose
What is maintained with AV sequential pacing?
Atrial kick
