Cardiac rhythm monitors & equipment 3 Flashcards
With 1st degree heart block, the PR interval is
> 0.20 sec.
1st degree heart block is usually
asymptomatic (no treatment required)
2nd degree heart block consists of
Mobitz type 1 & 2
Mobitz type 1 is characterized by the
PR interval becomes progressively longer with each cycle, but the last P wave does not conduct to the ventricles
Mobitz type 1 is usally
asymptomatic; if symptomatic treat with atropine
Mobitz type 2 is characterized by
some P’s conduct to the ventricles while others don’t (there is usually a set ratio of 2:1 or 3:1)
With Mobitz type 2, patients are
symptomatic
Treatment for Mobitz type 2 is
pacing
3rd degree heart block is characterized by
the atria & ventricles have their own rates (AV dissociation)
Treatment for 3rd degree heart block is
a pacemaker or isoproterenol
What is the saying for 1st degree heart block?
if r is far from p then you have a first degree
The etiology of 1st degree heart block is
age related degenerative changes
CAD
digoxin
amiodarone
The saying for 2nd degree heart block type 1 is
“longer, longer, longer, drop, then you have a Wenckebach”
Etiology for 2nd degree heart block type 1 is
structural conduction defect
myocardial injury/infarction
beta-blockers
CCBs
digoxin
sympatholytic agents
The saying for Mobitz type 2 is
if some “p”s don’t get through, then you have a Mobitz II
Etiology for Mobitz type 2 is
a structural conduction defect or infarction
___________ has a high risk for progressing to complete heart block
Mobitz type 2
The saying for 3rd degree heart block is
If “P”s and “Q”s don’t agree then you have a 3rd degree
3rd degree heart block can often lead to
CHF due to decreased HR & CO
Stokes-Adams attack= decreased CO–> decreased cerebral perfusion–> syncope
Antiarrhythmic medications can be divided into
4 classes
Class 1 drugs
inhibit fast sodium channels
Examples of class 1 drugs include
lidocaine, procainamide, & phenytoin
Class 2 drugs
decrease the rate of phase 4 depolarization
Examples of class 2 drugs include
beta-blockers
Class 3 drugs
inhibit potassium ion channels (prolongs phase 3 repolarization)
Examples of class 3 drugs include
amiodarone & bretylium
Class 4 drugs
inhibit slow calcium channels and slow the conduction velocity through the AV node
Examples of class 4 drugs include
verapamil & diltiazem
Adenosine works by
slowing conduction through the AV node
The dose range of adenosine is
3 mg-12 mg
peripheral: 6 mg, then 12 mg
central: 3 mg, then 6 mg
Adenosine is useful for
supraventricular tachycardia
WPW with a narrow QRS
_______________ can cause bronchospasm in asthmatic patients
Adenosine
The Class 1 of antiarrhythmic medications is further divided into
1A- moderate depression of phase 0
1B- weak depression of phase 0
1C-strong depression of phase 0
Lidocaine & phenytoin are considered
Class 1B antiarrhythmics
Flecainide & Propafenone are considered
Class 1C antiarrhythmics
Quinidine, procainamide, & disopyramide are considered to be
Class 1A antiarrhythmics
Wolff-Parkinson-White syndrome is associated with:
a. atrial reentry
b. SA nodal reentry
c. atrial-ventricular reentry
d. ventricular reentry
c. atrial-ventricular reentry
The most common cause of tachyarrhytmias are
reentry pathways
In the normal conduction pathway, the cardiac impulse moves
in one direction: SA node–> AV node–> His bundle–> bundle branches–> purkinje fibers
The cardiac impulse cannot move
backward, b/c all of the tissues behind the impulse remain in the absolute refractory period
When a reentry pathway develops, a single cardiac impulse can
move backward and excite the same part of the myocardium over and over creating a reentry tachyarrhythmia
The reentry circuit can be broken by
slowing the conduction velocity through the circuit or increasing the refractory period of the cells at the location of the unidirectional block
Conditions that increase the risk of reentry tachyarrhythmias include
left atrial dilation
ischemia
hyperkalemia
epinephrine
How can mitral stenosis cause a reentry pathway?
conduction must occur over a longer distance
How can ischemia cause a reentry pathway?
conduction velocity through the affected region is too slow
How can epinephrine cause a reentry pathway?
it shortens the duration of the refractory period
