9: Drugs for Arrhythmias Flashcards
which areas of the heart have fast vs slow APs
- fast: atria, ventricles, purkinje fibers
2. slow: SA node, AV node
Phase 0-4 of a fast AP***
0: depol -> fast Na channels open -> Na enters cell
1: K exits cell + fast Na channels close -> some repol
2: plateau phase: K exits cells + Ca enters
3: Ca channels close + K exits more rapidly -> repol
4: resting MP gradually restored by Na/K ATPase and Na/Ca exchanger
slow AP: how are phases 0, 3, and 4 different
Phase 0: Ca influx thru slow L type channel
3: increased K efflux, inactivation of Ca channels
4: pacemaker current (funny current): poorly selective ion influx (Na, K) + slow Ca influx via T-type channels
what gradient does Na travel down when Na channels are activated
electric and concentration gradients
what is the two main roles of K in the AP?
- repol
2. regulate duration of refractory period
four thing to consider before starting anti-arrhythmic therapy
- eliminate the cause
- make a firm dx
- consider underlying conditions
- consider non-pharmacologic therapy
four non-pharmacologic approaches to treating cardiac arrythmias
- cath ablation
- implantable cardioverter/defibrillator
- pacemaker
- DCC
three reasons to use pharmacotherapy instead of non-pharm for arrhythmias
- alleviate sx like weakness, fatigue
- prevent deterioration of hemodynamics
- minimize risk of sudden death
two things that must be true for reentry to occur
- obstacle to a homogenous conduction / unidirectional block in the circuit
- conduction time around circuit must exceed effective refractory period
most common type of PSVT
AV nodal re=entrant tachycardia (AVNRT)
what does torsades de pointes look like on ECG
rapid polymorphic vtach in a ribbon pattern
examples of drug that cause long QT syndrome
groups 1A and 3 antiarrhythmics, other drugs like anti-psychotics, Abx
