Arrhythmia Mechanisms

Question 1

Normal Automaticity

Answer 1

Spontaneous phase 4 depolarization from normal resting levels

Question 2

If

Answer 2

Inward Na current that starts at maximum diastolic polarization (MDP) to generate normal automaticity

Question 3

Enhanced (Accelerated) Normal Automaticity

Answer 3

Some other pacemaker region like His-Purkinje tissue has much faster stimulation and usurps pacemaker function from the SA node

Question 4

Sinus Bradycardia w/ Accelerated Subordinate Focus (what it is and possible cause)

Answer 4

Sinus goes slower than some other pacemaker region, so other region usurps function again. MI can cause

Question 5

Abnormal Automaticity

Answer 5

Resting potential not at full repol level when activated, so you get Ca channels instead of Na channels mediating AP, so slower upstroke and conduction potential

Question 6

2 Conditions Necessary for Re-Entry Impulse

Answer 6

Unidirectional block and slow conduction

Question 7

2 Things Necessary to Maintain to get Re-Entry Tachycardia (repetitive circuit/loop)

Answer 7

Conduction velocity and refraction

Question 8

3 Structural and Functional Barrier Types that can Cause Re-Entry

Answer 8

Scar
Normal Anatomical Barrier (opening around IVC)
Heterogenous Physiological Properties (like His)

Question 9

Dual AV Nodal Pathways (explanation, pathological relevance, and clinical sign)

Answer 9

Some people have fast and slow. Usually fast comes around and reaches His, then reflects and blocks slow pathway. But faster pathways have longer refractory period. So if premature atrial beat occurs, fast is still in refractory, slow isn’t, so it will propagate down slow and then block fast. Can lead to re-entry problems and longer PR interval

Question 10

Afterdepolarizations and Triggered Activity

Answer 10

Premature beats create slight depol oscillations of membrane. The more premature the larger. Eventually long enough to reach threshold and cause “Triggered Activity”

Question 11

DADs vs. EADs

Answer 11

Delayed, after complete repol have Ca mediated oscillation generating Na-induced AP at threshold vs. before repol and everything Ca mediated

Question 12

EAD Mech

Answer 12

If you have Ca current that lasts awhile and maybe weak K current to repol, they’ll conflict and repol will take awhile. Ca RP is energy/time dependent, so they might finish RP before potential drops below threshold and thus open again and cause another AP