cardiac arrhythmias

Question 1

What is supraventricular tachycardia?

Answer 1

abnormal tachycardia which requires participation of either atrial or AV node tissue

Question 2

What is ventricular tachycardia?

Answer 2

abnormal tachy originating in ventricle or his-Purkinje system; by definition doesnt requrie involvment of either atrium or av node

Question 3

What is the normal impulse formation occur?

Answer 3

intrinsic automaticity; pacemaker cells

Question 4

What is the rate normally for the different pacemaker cells?

Answer 4

sinus (60-100)
AV node (50-60)
Hiis-purkinje system(30-40)

Question 5

What is the static resting membrane potential of normal myocytes?

Answer 5

-90 mV

Question 6

What is the membrane potential for SV and AV node?

Answer 6

-60 mV

Question 7

What is the pacemaker current?

Answer 7

If, a slow inward sodium current active only below -50 mV

Question 8

How does overdrive suppression occur?

Answer 8

If is much smaller than the depolarization from above and leading to net hyperpolarization

Question 9

What do different threshold portential result in?

Answer 9

more negative the threshold potential the faster the resulting depolarization

Question 10

what does sympathetic rate do to autonomic regulation?

Answer 10

beta stim leads to increasing the open probablility of pacemeaaker current
secondarily makes the threshold potential more negative

Question 11

What does parasympathetic autmoaticity of heart rate?

Answer 11

decreases open probability of pacemaker current channel
secondarily makes threshold potential less negative
negative making it easier to trigger

Question 12

What does parasympathetic tone dominates when?

Answer 12

at rest; therefore wihtout it the SN is about 85-105

Question 13

How are adjacen myocytes coupled by?

Answer 13

low resistance gap junction

Question 14

What can lead to cell decoupling?

Answer 14

pathologic fibrosis in the heart; may result in automatcity of pacemaker

Question 15

What is an escape rythm?

Answer 15

failure of sinus node can result in emergency of normallly suppressed AV node; aka junctional escape in av node
escape rythm in infranodal tissue is a ventricular escape

Question 16

Junctional escape has what type of QRS?

Answer 16

narrow QRS

Question 17

A ventricular escape has what type of QRS?

Answer 17

wide qrs

Question 18

What is an early after depolarization

Answer 18

triggered activity, promoted by conditions whichprolong action potential and membrane osscilation

related to inward Ca2+ current or reactivation of fast Na current

Question 19

What is the clinical mechanism of torsades de pointes VT precipitated by qt prolonging drugs?

Answer 19

early afterdepolarizations

Question 20

What are delayed aferdepolarizations?

Answer 20

membrane oscillations after completion of full repolarization
promoted by conditions which lead to high intracellular calcium

Question 21

What are the different types of av block?

Answer 21

1st degree delay without failure of conduction
2nd degree: some beats fail to conduct
3rd degree no propogation from atruim to ventricle

Question 22

What is reentry in unidcirectional block?

Answer 22

abnormal endless loop myocardial progpagation;

Question 23

What are the requirements for reentry?

Answer 23

two distinct paths for propogation
slowed conduction in one path
unidirectional block; tissue capable of conduction in one but not the opposite direction; often functional

Question 24

What on EKG is a sign of WPW?

Answer 24

delta waves

Question 25

What are the signs of first degree AV block?

Answer 25

PR prolongation; PR>200 ms
1:1 AV relationship
benign and asymptomatic

Question 26

What are the causes of first degree AV block?

Answer 26

reversible” autonomic, transient AV nodal ischemia, drugs

irreversible: MI, chronic degenerative disease

Question 27

What is mobitz 1?

Answer 27

2nd degree AV blcok;
PR gradually increases until impulse is blocked
conduction is imparired in AV node
usually benign and asymptomatic

Question 28

What are the causes of MObitz I?

Answer 28

causes include autonomic tone, acute MI, due to increased vagal tone or ischemia AVN

Question 29

What is Mobitz II?

Answer 29

suddent intermittent loss of AV conduction without preceding gradual PR length
may progress to 3rd degree without warning
results from scar, myocardial infarct, chornic degenerative disease

Question 30

What ist he treatment for Mobitz II?

Answer 30

pacemaker

Question 31

What is atrial flutter?

Answer 31

rapid regular atrial activation
circiut is a atrial tissue along tricuspid valve annulus;
EKG saw tooth pattern

Question 32

What are causes of atrial flutter?

Answer 32

prior heart surgery, cardiomyopathy, coronary disease

Question 33

What are treatments for atrial flutter?

Answer 33

rate control and rythm control;

cardiac ablation of tricuspid caval isthmus is 95% curative

rate control by I and III

Question 34

What are the a fib predisposers?

Answer 34

cardiothoracic surgery, ETOH, CHF, valvular disease, enlarged atria, pulmonary disease, HTN hyperthyroidism

Question 35

What is the common cause of paroxymal SVT?

Answer 35

accessory pathway, crossing AV groove, reentry, conduct antegrae or regtrograde, WPW is one version of this

Question 36

What is the treatment for WPW?

Answer 36

nothing that may shorten refactory period of accessory pathway;

IV amiodarone or procainamide
cardioversion
catheter ablation definitve therapy

Question 37

What are ventricular premature beats or contractions?

Answer 37

common and often bening
produced by ectopic ventricular focus
primary therapy is obs and possible bta blockers