Flashcards in dysrhythmias Deck (19)
2 ways to change the refractory period
1. change the AP duration
2. blockade of Na channels to recover from inactivation
what does the Na/Ca exchanger rely on
what does active Arrhythmogenesis rely on?
effect of Ach on phase 4 diastolic depolarization of nodal cells
increased potassium current, reduces slope of phase 4
effect of NE on phase 4 diastolic depolarization of nodal cells
increased calcium and funny current, increases slope of phase 4
effect of hypokalemia on phase 4 diastolic depolarization of nodal cells
decreased potassium current, increases slope of phase 4
effect of mild hyperkalemia on phase 4 diastolic depolarization of nodal cells
increased maximum diastolic potential, increases slope of phase 4
effect of severe hyperkalemia on phase 4 diastolic depolarization of nodal cells
significantly depolarized membrane potential, cells become inexcitable
what are delayed after depolarizaton (DAD) due to?
cytosolic and/or SR calcium overload
what are early after depolarizaton (EAD) due to?
occur earlier (towards end of phase 2/beginning of phase 3); due to altered ion flux during plateau phase
what characterizes EAD?
prolonged action potential duration
what can result in prolonged APD?
1. reduced K current
2. incr Ca
3. incr Na-Ca exchanger activity
4. incr later Na current
in comparison to EAD, DAD is only due to concentrations of what ion?
Ca (thus occurs during phase 4)
EAD are associated with ____HR, DAD are associated with _____HR
EAD are associated with low HR, DAD are associated with high HR
short PR interval characterized by signal that can reenter atria via accessory pathway and depolarize AV node - what syndrome?
passive arrhythmias are generally due to?
cardiac remodeling-->changes in gap jxns, changes in cellular structure
role of gap jxns in AV node
there are less-->signal moves slower
if there is tissue damage, the AP duration will be ________ after passing thru damaged area
if there is tissue damage, the AP duration will be shorter after passing thru damaged area