Cardiac monitors and rhythm Flashcards
What pathway depolarizes the left atrium?
Bachmann bundle
What is the electrical pathway through the heart?
SA node
Internodal Tracts
AV node
Bundle of His
Bundle Branches
Purkinje fibers
What has the slowest conduction through the heart?
SA and AV nodes .02-.1
What has intermediate conduction through the heart?
Myocardial muscle cells
.3-1
What has the fastest conduction through the heart?
Bundle of His, Bundle branches, Purkinje fibers
1-4
What is conduction velocity a function of?
- RMP
- Amplitude of action potential
- Rate of change in membrane potential during phase 0
What affects conduction velocity?
ANS tone
Hyperkalemia
Ischemia
Acidosis
Antiarrhythmic drugs
What are accessory pathways?
Connective tissue that isolates the atria
Prevents atria from prematurely exciting ventricular tissue
***AV node plays big real
What does the James fiber connect?
Atrium to AV node
What does Atrio-hisian fiber connect?
Atrium to Bundle of His
What does Kents bundle connect?
Atrium to ventricle
What does Mahaims bundle connect?
Av node to ventricle
When does the atria repolarize?
During the QRS
When does ventricular depolarization begin? end?
Beings during QRS
Ends - ST segment
When does ventricular repolarization begin? end?
Beings- T wave
Ends - After T wave
Can a stimulus depolarize the myocyte during absolute refractory period?
No
Can a stimulus depolarize the myocyte during relative refractory period?
Yes but need a larger stimulus
What ion is leaking out to start the depolarization of the myocyte? What phase?
Phase 4
Potassium (K funny channels)
What phase does depolarization occur in? What is the ion movement?
Phase 0
-Na in
What phase does initial repolarization occur in? What is the ion movement?
Phase 1
Cl In
K out
What phase does plateau occur in? What is the ion movement?
Phase 2
Ca In
K out
What phase does final repolarization occur in? What is the ion movement?
3
K out
What ion moves out of the cell in 4 out of 5 phases of the ventricular action potential?
Potassium
What disease causes PR interval depression?
Pericarditis
What disease causes a U wave?
Hypokalemia
What disease causes a peaked T wave?
Intracranial hemorrhage
What disease causes a Delta wave?
Wolff-Parkinson White
Where is ST elevation or depression measured?
The J point
looking for a change of at least 1.0
What segment of the ECG is considered isoelectric?
PR interval
What do leads 2, 3, and aVF monitor?
Inferior wall - RCA
What do leads 1, aVL, V5, and V6 monitor?
Lateral
Circumflex
What do leads V1 and V2 monitor?
Septum
LAD
What do leads V3 and V4 monitor?
Anterior wall
LAD
What is the mean electrical vector?
The average current flow of all action potentials at one time
What are the three bipolar leads?
I
II
III
What are the three limb leads?
aVR
aVL
aVF
Where does the mean electrical current tend to point to?
Away from ischemia
Toward Hypertrophy
What is the deflection for a normal axis?
+ Lead 1
+ Lead aVF
Both hands up (YAY)
What is the deflection for a left axis deviation?
+ Lead 1
- Lead aVF
Left hand up, right down (shake left hand)
What is the deflection for a right axis deviation?
- Lead 1
+ Lead aVF
Right hand up, left down (shake right hand)
What two leads are monitored for axis deviations?
Lead 1
Lead aVF
What is the deflection for extreme right deviation ?
- Lead 1
- Lead aVF
Left hand down, right down (both down, boo)
What is a normal axis degree?
-30 to +90
What degree is left axis?
< -30
What degree is right axis
> +90 degrees
What causes L axis deviation?
Problems with the L heart
HTN
LBBB
aortic stenosis and regurg
Mitral regurg
What causes R axis deviation?
Problems with the R heart (lungs)
Pulmonary HTN
PE
Cor pulmonale
Bronchospasm
COPD
Can adenosine be used for an effective treatment of afib?
NO
How to determine 1st degree heart block?
> .20 PR
AV node or Bundle of His issue
How to determine 2nd degree type 1 heart block?
Longer Longer Longer - Drop
Wenckebach
Av node issue
symptomatic - give atropine
How to determine 2nd degree type 2 heart block?
Random dropped qrs - mobitz 2
Problem with bundle branches
Treatment - Pacemaker
*****High risk for type 3
How to determine 3rd degree heart block?
Ps and Qs don’t agree
Degeneration of atrial conduction system (Lenegre’s disease)
Can lead to CHF
What drugs are class 1? How do they work?
Na channel blockers
1A - Prolong phase 3
1B - Shorten phase 3
1C- Strong depression of phase 0
What drugs are class 2? How do they work?
Beta Blockers
Slows phase 4
What drugs are class 3? How do they work?
K channel blockers
Prolongs phase 3
What drugs are class 4? How do they work?
Ca channel blockers
Slows conduction velocity
How does adenosine work?
Endogenous nucleoside that slows AV node conduction through adenosine 1 receptor
Can cause bronchospasm
What class is quinidine, procainamide, and disopyramide?
1A Na channel blockers
Prolong phase 3
What class is lidocaine, phenytoin?
1B Na channel blockers
Shorten phase 3
What class is flecainide, propafenone ?
1C Na channel blocker
Shorten phase 0
What class are beta blockers?
2
Slows phase 4
What class is amiodarone, bretyium?
K channel blockers
Class 3
Prolongs phase 3
What class is verapamil, diltiazem
Ca channel blockers
Class 4
Slows conduction through AV node
What disease is associated with atrial-ventricular reentry?
Wolff Parkinson white
Through the Kents Bundle
What EKG findings are consistent with Wolff Parkison white?
Delta wave
Short PR
Wide QRS
Possible t wave inversion
What is a Delta wave?
Slowed, curve upstroke of QRS
What are the two ways to disrupt the reentry circuit?
1, Slow the conduction velocity
2. Increase the refractory period
What is the most common cause of tachyarrhythmias?
The reentry pathway
How can mitral stenosis cause a reentry pathway?
Conduction must occur a longer distance
How can ischemia cause a reentry pathway?
Conduction velocity through the damaged tissue is slowed
How can epi cause a reentry pathway?
Shortens the duration of the refractory period
What is the definitive treatment for WPW?
Ablation
**Risk is thermal injury so monitor esophageal temperatures
What are other treatments for WPW?
Procainamide
Cardioversion
What is the most common tachydysrhythmias associated with WPW?
Orthodromic AV nodal reentry
90%
Is orthodromic or antidromic more dangerous?
Antidromic
ANTI - Av node is bypassed
Leads to CHF and Vfib