Mechanisms of some fatal cardiac arrhythmias

Question 1

fatal cardiac arrhythmias can be caused by (broad)…

Answer 1

abnormal automaticity OR
triggered activity OR
mechanism of abnormal conduction (REENTRY)

Question 2

Automaticity

Answer 2

cell’s ability to depolarize itself to threshold generating spontaneous action potential

(cardiac myocytes can acquire pathologically, esp. when injured and thus leaky)

Question 3

triggered activity

Answer 3

abnormal ion fluxes that interrupt repolarization…

cause afterdepolarizations

Question 4

afterdepolarizations

Answer 4

occuring in phase 2 or 3…“early”

ocurring in phasse 4…“delayed”

Question 5

early afterdepolarization during plateau phase 2 is associated w/…

Answer 5

increased calcium inflow (possibly due to defective calcium channels)

Question 6

Early afterdepolarization during phase 3

Answer 6

abnormal sodium inflow due to defective Na channels

Question 7

Delayed afterdepolarization during phase 4

Answer 7

high intracellular levels of calcium

which can be due to marked catecholamine stimulation

Question 8

whether early or delayed, afterdepolarizations can generate…

Answer 8

spontaneous action potentials…which can be self-perpetuating and lead to tachyarrhythmias

Question 9

Abnormal conduction (Reentry)

Answer 9

Re-Read Section!! (marked in blue)