5 Phases of Cardiac Action Potential - ANSWER: *Phase 0: influx of Na+
(depolarization - conduction velocity)
*Phase 1: transient efflux of K+ (how quickly the cell can be depolarized again)
*Phase 2: influx of Ca 2+ & Na+ (")
*Phase 3: efflux of K+ > influx of Ca2+ & Na+ (")
*Phase 4: Na+ -K+ pump (resting phase, ion leakage determines when next
spontaneous depolarization will happen)
Excitable Periods of Cardiac Action Potential - ANSWER: Phase 0, Phase 1, Phase 2
Refractory Periods of Cardiac Action Potential - ANSWER: Phase 3 & Phase 4
Drugs That Decrease Thresholds - ANSWER: Atropine, Catecholamines,
Glucocoticoids
Drugs That Have No Proven Effect on Thresholds - ANSWER: Amiodarone, Anesthetic
Drugs
Name of Class 1 Antiarrhythmic Drugs - ANSWER: * 1a: disopyramide, procainamide,
quinidine
*1b: lidocaine, mexiletine
*1c: flecainide, propafenone
Class 1 Antiarrhythmic Drugs - ANSWER: Sodium Channel Blockers
, Name of Class II Antiarrhythmic Drugs - ANSWER: metoprolol, atenolol
Class II Antiarrhythmic Drugs - ANSWER: Beta-blockers
Name of Class III Antiarrhythmic Drugs - ANSWER: amiodarone, sotalol, ibutilide,
dofetilide, dronedarone
Class II Antiarrhythmic Drugs - ANSWER: Potassium Channel Blockers
Name of Class IV Antiarrhythmic Drugs - ANSWER: verapamil, diltiazem
Drugs Affect on Each Phase of Action Potential - ANSWER: *Phase 0: Class I - Na+
Channel Blocker
*Phase 2: Class IV - Ca+ Channel Blocker
*Phase 3: Class III - K+ Channel Blocker
*Phase 4: Class II - Beta Blocker
Laser Lead Extraction - ANSWER: 1. Locking stylet introduced down lead lumen &
advanced to tip
2. Traction force directed to tip of lead and to aid in support
3. External outer sheath with beveled edge can be used over laser catheter for more
direct passage of adhesion into laser
Limitations to Laser Lead Extraction - ANSWER: - Fractured lead may prevent stylet
passage
- Stylet dislocation with high force
- Adherent calcification cannot vaporize
- Insulation damage or externalized conductors can hinder tracking the laser over
catheter over
- Risk of myocardial injury/perforation
Mechanical Lead Extraction - ANSWER: - Mechanical dilator sheath over the lead
- Uses rotational and reciprocating motion of internal cutting tool to chew fibrous
adhesion
- Lead pulled thru distal end of sheath w/manual traction
Limitations for Mechanical Lead Extraction - ANSWER: - Works better for fewer
adhesions
- Most of the fibrous tissue still insitu and can obstruct further advancement of
sheath
- Calcifications
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