Electricity

Question 1

sym vs para stim effects on AP?

Answer 1

SYM: inc If
inc Ica,L

PARA: inc IK,Ach
dec If
dec ICa,L

Question 2

automaticity in SA, AV, his

Answer 2

SA (120bpm) > AV (80-100) > His-Purkinje (30-50)

Question 3

3 primary factors that affect AP conduction velocity

Answer 3

1. cell diameter (inc w/ inc)
2. intensity of depolarizing current (inc w/ inc)
3. cell to cell coupling (more coupled -> faster)

Question 4

anisotropic

Answer 4

conduction is fastest in long axis of myocytes/heart

Question 5

conditions that shift site of fastest automaticity in heart

Answer 5

1. suppress SA node automaticity
2. enhance automaticity of latent pacemaker cells
3. block conduction between SA node and lower heart (e.g. AV block –> vents beat but at slower rate)

Question 6

diffuse ST elevation is a sign of?

Answer 6

pericarditis

Question 7

via what do the coronary veins return decoy blood to R atrium?

Answer 7

coronary sinus

Question 8

T wave inversion could be (6)

Answer 8

1. *ischemia
2. hypertrophy
3. metabolic changes
4. drugs
5. drinking ice water
6. norma variant (III, V1, V2)

Question 9

persistant ST elevation in leads over an infarct site may mean:

Answer 9

LV aneurysm has developed

–> ST elev should inc w/ tacky

Question 10

common factors that increase automaticity (7)

Answer 10

1. catecholamines
2. sympathomimetics
3. hypoxia (reflex)
4. hyperthermia
5. acidosis
6. drugs (e.g. digoxin)
7. myocardial stretch (due to chamber hypertrophy)

Question 11

common factors that decrease automaticity (4)

Answer 11

1. increased vagal tone
2. B blockade
3. CCB
4. hypothermia

Question 12

classic reentry circuit requires: (3)

Answer 12

1. closed loop path w/ differing conduction velocities down each limb
2. differing refectory periods (can transiently generate localized unidirectional block)
3. conduction time around pathway must exceed duration of longest refractory period w/in circuit to maintain an excitable gap

**normally cause no arrhythmias

Question 13

a fib can lead to: (3)

Answer 13

1. hemodynamic compromise
2. systemic embolization **L atrial appendage
3. symptoms

Question 14

factors that can depress intrinsic automaticity –> brady

Answer 14

1. aging
2. disease that affects atrium (ischemic heart disease, cardiomyopathy)
3. meds (anti-arrhythmias, B blockers, CCB)
4. metabolic (hypothyroidism)
5. athletes
6. vasovagal syncope (transient period of high vagal tone)

Question 15

ventricular bigeminy

Answer 15

VPC when every other beat is a VPC

Question 16

a flutter is associated w/ risk of?

Answer 16

atrial thromboembolism

Question 17

supraventricular tacky w/ aberrant ventricular conduction

Answer 17

SVT arrhythmia
wide QRS
usually seen in pts that develop SVT in presence of underlying conduction abnormalities (BBB)

Question 18

vagal maneuvers

Answer 18

act parasym stim of heart –> slows AV node conduction –> affects arrhythmias involving AV node (AVRT, AVNRT)

• carotid sinus massage (unilateral)
• valsalva maneuver
• face in cold water
• pressure on eyeballs
• slows sinus rate
• prolongs PR

Question 19

indications for pacemaker

Answer 19

brady arrhythmias

• sinus arrest
• symptomatic brady
• 2* type II or 3* AV block

Question 20

when is catheter ablation used?

Answer 20

tachy-arrhythmias not controlled by meds

Question 21

anti-thrombatic tx

Answer 21

anti-coag for stroke reduction
-warfarin
-dabigatran, rivaroxaban, apixaban, endoxaban
L atrial appendage exclusion/plug
anti coag required for 3 wks before and 4 wks after cardioversion