Mechanism of Arrhythmia

Question 1

Two types of triggered activity

Answer 1

Early After Depol

Delay after depol

Question 1

sign and underlying pathology of WPW

Answer 1

detla waves

extra connection between atria and ventricles, muscle bridge allowing for reentry

Question 2

DADs

Answer 2

oscillation after completion of rull repol (phase 4)

promoted by high Ca, catecholamines

Question 3

clinical mechanism category of Torsades de pointes VT

Answer 3

EAD

Question 4

because of gap junctions, automaticity will be ___- in pacemaker cells coupled to adjacent working myocardium

Answer 4

decreased

Question 4

escape rhythm arrsing in AV node (=_____)
QRS -
P wave -
Rate -

Answer 4

junctional escape rhthm
narrow QRS

no P wave

rate 50-60

Question 4

mechanism category of Iodpathic VT in normal heart, Digitalis Toxicity

Answer 4

DAD

Question 5

EADs

Answer 5

oscillations within plateu (phase 2) or repol (phase 3)

promoted by prolonged AP (QT elongation)

related to inward Ca current (phase 2) or reactivation of Fast Na current (phase 3)

Question 7

Over drive suppression

Answer 7

faster sites transiently suprress rate of subsidiary pacemakers (I-f smaller in subsidary cells, leading to slow recover after ovredrive of pacemaker cells)

Question 8

all disordered rhythms originate from (2)

Answer 8

alterations in impulse formation

alteration in impulse conduct - propagation

Question 9

slow inward sodium current only active at negative potentials below -50, primary current determining normal automaticity

Answer 9

Pacemaker current (I_f)

Question 11

relatively high resting potential of ___ and ___ cells keeps most fast na channels in the inactivated stight riquireing dependence on the slower Ca current to mediate depolarization and a slower AP upstroke

Answer 11

AV noded and sinus node

Question 12

sympathetic effects on automaticity

Answer 12

SN rate increased by sympathetic tone

decreases open probability of I-f channel

makes threshold potential more negative, makng triggering easier

Question 13

parasympathetic effects on automaticity

Answer 13

SN rate depressed by parasymp

decreases open probabilty of I-f pacemaker channel

makes threshold less negative,

also increases I-KAch channels to be open leading to more negative diastolic potential

Question 14

normal gradient of automaticity

Answer 14

sinus node - 60-100

AV node 50 - 60

HIs purkinje system - 30-40

Question 15

requirements for reentry

Answer 15

two distinct paths

area of slowed conduction

functional or permanet unidirectional block

Question 16

3 factors determity normal automaticity

Answer 16

rate of diastoic depol (I-f)

maximum negative diastolic potential

threshold potential (more neg = faster rate)

Question 17

degrees of AV or His bundle block

Answer 17

1 - delay without failure of conduction

2. some but not all beats fail to conduct

3 no propogation from atrium to ventricle (complete heart block)

Question 18

escape rhytm arising in franodal tissue =

QRS -

Answer 18

ventricular escape rhythm

wide QRS

Question 19

parasympathetic or sympathetic tone dominates at rest

Answer 19

parasympathetic