dysrhythmias Flashcards
2 ways to change the refractory period
- change the AP duration
2. blockade of Na channels to recover from inactivation
what does the Na/Ca exchanger rely on
concentrations
what does active Arrhythmogenesis rely on?
automaticity
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?
- reduced K current
- incr Ca
- incr Na-Ca exchanger activity
- 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?
Wolff-Parkinson-White 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
what is the refractory period dependent on?
Na channels
