Ppal99 Dissecting The Usmle 1,2,3 Ekg And Arrythmias Chapter

Front 1

Depolarize

Back 1

to become positive from baseline

Front 2

describe how the sodium channels work.

Back 2

m gate opens => Na+ leaks in=> slow upstroke "slow channels"
• hit threshold potential => m/ h gates open => Na + rushes in => inc. resting potential 'fast Na channels"
• can't reach +65 b/c the higher you go=> dec. Na+ driving force, inc.K+ driving force
• m gate closes => can't start another action potential = absolute refractory period

Front 3

Repolarize:

Back 3

become negatitve from a positive potential

Front 4

how can K+ reach its potential?

Back 4

K+ can actually reach its potential of -96 (unlike Na+) b/c of K+ leak channels

Front 5

Hyperpolarize

Back 5

become more negative than baseline

Front 6

how do you get hyperpolarization?
Net positive => Na+ /Ca2+ pump
Net negative=> Na+ /K+ pump

Back 6

>>3 Na +in, 1 Ca2+ out channels reset the electrical membrane potential (1:1 in rvs direction)
>>3 Na+ out, 2 K+ in ATPase resets the concentration gradient (max activity at -96)

Front 7

Automaticity

Back 7

resetting the membrane potential

Front 8

Charge movement:

Back 8

All pumps that don't have an ATPase can be reversed ...
• Na/K pump: 3 Na + out, 2 K+ in
=> net negative charge
• Ca/Na pump: 3Na+ in + 1Ca2+ out
=> net positive charge
• Reverse Ca/Na pump: 1 Na + out, 1 Ca2+
=> net posititve charge

Front 9

Current

Back 9

change in membrane potential caused by movement of ions

Front 10

Action potential

Back 10

"all or none"=> reach threshold, then fires (any extra = "overshoot")

Front 11

what ion is responsible for the resting membrane potential:

Back 11

K channels are responsible for this

Front 12

what ion has a higher conductance and permeability

Back 12

K+: higher conductance/permeability

Front 13

which ion has a greater driving force?

Back 13

Na+: greater driving force

Front 14

what ion is responsible to depolarize, repolarize and automaticity?

Back 14

Depolarize (Na) => Repolarize (K) => Automaticity (Na)

Front 15

what ion does the SA/AV node uses to depolarize?

Back 15

SA/ AV nodes (use Ca2+ to depolarize)

Front 16

where is the ion that is responsible for atrial depolarization and contractility?

Back 16

Extracellular Ca2+ => atrial depolarization
Intracellular Ca2+ => contractility

Front 17

Cardiac Action Potentials: what ions go in/out in each phase?
Phase 0:
Phase 1:
Phase 2:
Phase 3:
Phase 4:

Back 17

Phase 0: Na + or Ca2+ in (depolarization)
Phase 1: K+ out (initial repolarization)
Phase 2: Ca2+ in "plateau phase" (conduction to AV node) => contractility
Phase 3: K+ out (repolarization)
Phase 4: Na +in (automaticity = hyperpolarization)- who can reset fastest => inc. slope

Front 18

Absolute refractory period

Back 18

all depolarization, some repolarization

Front 19

Relative refractory period

Back 19

rest of repolarization = >need bigger stimulus to fire

Front 20

where are the following located?
SA node:
AV node:
Purkinje:

Back 20

SA node: RA wall (near SVC)
AV node: interatrial septum
Purkinje: IV septum

Front 21

where are the ff located?
RA/RV
LA

Back 21

RA/RV- more anterior "Right behind chest"
LA - compresses esophagus

Front 22

what artery supplies the SA node?

Back 22

The dominant artery:
the artery that supplies the SA node
(usually the right coronary)

Front 23

if a patient lose 40% coronary blood supply, what does that lead to?

Back 23

lose 40% coronary blood supply=> heart failure

Front 24

describe the blood supply from the aorta 85% of the blood

Back 24

85% of heart:
Aorta => Left main coronary a. => L circumflex artery (LA) => marginal artery (LV)
=> LAD (ant. wall, septum, inf. wall, lower 1/3 post. wall)

Front 25

15% of the blood goes through where?

Back 25

15% of heart:
Aorta => Right coronary a. => (SA/AV, septum, top 2/3 post wall)=> R marginal (RV)
=> Posterior IV

Front 26

increase Ca2+ =>

decrease Ca2+ =>

Back 26

increase Ca2+Arrhythmia
decrease Ca2+: Heart Block

Front 27

describe atrial depolarization
phases
fires/resets

Back 27

Phases 0,3,4 only
Fires slow, but resets fast

Front 28

why do we need to shock the heart when its arrythmic

Back 28

Ex: Shock the heart to pause it so SA node (no phase 2) can take over

Front 29

how does lidocaine work in arrythmias?

Back 29

Lidocaine attacks ischemic tissue only=> silences ectopic site=> SA node rules

Front 30

what do the ff give you: Ventricle Effects:
inc. Na+:
dec. Na +:

Back 30

Ventricle Effects:
inc. Na+: Arrhvthmia
dec. Na +:Arrhythmia
(due to Na/ Ca channel)

Front 31

why tetany (low Ca2+) does not affect your ventricle?

Back 31

the ventricular cells has Phase 1,2:
which lengthens absolute refractory period

Front 32

why do purkinjie fibers do not have control?

Back 32

Fastest firing (Purkinjie fibers), resets slow=> no control

Front 33

which wall of the heart holds on to contraction the longest and why?

Back 33

Anterior wall holds on to contraction longest=> longest phase 2

Front 34

EKG wave: P wave: atrium and phase

Back 34

P wave = Atrial depolarization (Phase 0)

Front 35

EKG wave: PR interval: heart mechanics and phase

Back 35

PR = Conduction from SA to AV node (Phase 2)

Front 36

EKG Waves:Q wave

Back 36

Q wave= Ventricle septum depolarization

Front 37

EKG Waves: R wave

Back 37

R wave =Ventricle anterior wall depolarization

Front 38

EKG Waves: S wave

Back 38

S wave = Ventricle posterior wall depolarization

Front 39

EKG Waves: QRS
phase

Back 39

QRS =Total ventricular depolarization (Phase 0)

Front 40

EKG Waves: QT
what happens if its too long?

Back 40

QT = Ventricular depolarization/ repolarization
(if too long, ectopic sites take over)

Front 41

EKG Waves: ST segment
define
phase

Back 41

ST segment= Ventricle "plateau phase" (Phase 2)

Front 42

EKG Waves: T wave
phase
define

Back 42

T wave =Ventricle repolarization (Phase 3)

Front 43

EKG Waves: U wave
define
phase

Back 43

U wave = Ventricle automaticity (Phase 4)

Front 44

what does the height of the EKG mean? tall? short?

Back 44

Height= voltage:
Tall => enlarged ventricle
Short => small or compressed ventricle (or inflammation)

Front 45

what does the width of the EKG mean? narrow and wide?

Back 45

Width = duration:
Narrow = > hypertrophy
Wide => dilated

Front 46

where are these leads located?
V1-2:
V3-4:
V5-6:
I/ AVL:
II/III/ AVF:

Back 46

V1-2: Septal
V3-4: Anterior
V5-6: Low lateral
I/AVL: High lateral
II/III/ AVF: Inferior

Front 47

how does depolariation happend?

Back 47

SA node => AV node and LA => pause => IV septum => to RV
=> around apex to post side of heart

Front 48

what fibers are responsible to make the atrium beat together?

Back 48

bachman fibers

Front 49

how does repolarization occur?

Back 49

starts on the posterior side of heart, opposite of depolarization

Front 50

where are the following bipolar leads located and what part of the heart does it sees?
Lead 1:
Lead 2:
Lead 3:
AVR:
A VL:
A VF:

Back 50

Lead 1: right arm to left arm, looking at heart from + electrode on L arm (sees left side)
Lead 2: right arm to left leg (sees RV)
Lead 3: left arm to left foot (sees LV)
AVR: on right arm (sees RA)
A VL: on left arm (sees LA)
A VF: left foot (sees apex)

Front 51

what are the precordial leads for?

Back 51

Precordial leads: use V 1 and V 2 to see IV septum

Front 52

Where does each precordial lead located and what part of the heart it sees?
V1
V2
V3
V4
V5
V6

Back 52

V1 - right upper sternal border (sees RA)
V2 -left upper sternal border (sees LA)
V3 - no anatomical site, half-way between V2and V4 (sees anterior wall)
V4 - left lower sternal border (sees apex)
V 5 - mid-clavicular line (sees LV)
V6 - mid-axillary line (sees LV)

Front 53

what does a positive deflection mean on an EKG and negative deflection?

Back 53

Electrodes only detect positive charges: see a wave coming toward it = > + reflection
coming away from it=> - reflection

Front 54

what would you see on an EKG when you see the ff.
⇧K:
⇩K:
⇧Ca:
⇩Ca:

Back 54

⇧K: peaked T waves
⇩K: U wave
⇧Ca: short QT
⇩Ca: prolonged QT

Front 55

how to calculate the max heart rate

Back 55

max heart rate = 220 - age

Front 56

Atrial arrhythmias Tx

Back 56

use Ca+ to depolarize=> use Ca channel blocker, then Warfarin

Front 57

Ventricular arrhythmias Tx

Back 57

use Na+ to depolarize => use Na channel blocker

Front 58

1st Degree heart block: define, pathogenesis and Tx.

Back 58

PR >5 small squares ~> bad SA node (Tx: exercise)

Front 59

what are the 2 types of 2nd degree heart block?

Back 59

Mobitz 1
Mobitz II

Front 60

what is mobitz type 1, what node is defective and Tx

Back 60

Mobitz 1: PR lengthens "winks" until drops QRS
~> bad AV node
(Tx: Pacemaker if sx)

Front 61

what is mobitz II and tx?

Back 61

PR fixed, but some QRS are gone ~> bad His-P (Tx: Pacemaker)

Front 62

3rd Degree heart block and Tx?

Back 62

Regular P-P and R-R, but don't correspond ~> destroyed AV (rx: Pacemaker)

Front 63

what is an overdrive Pacemakers:

Back 63

use guidewire to get control away from ectopic site

Front 64

what are On-demand Pacemakers? what does each letter mean?
1 st letter
2nd letter
3rd letter

Back 64

On-demand Pacemakers:
1st letter = chamber location
2nd letter = chamber you are sensing
3rd letter = what you want pacemaker to do (I=inhibit)

Front 65

PSVT Tx:

Back 65

1) Monitored carotid massage
2) Adenosine

Front 66

Premature Ventricular Complexes (PVCs): Premature Beat:

Back 66

QRS has a pause after it

Front 67

(PVCs): Bigeminy:

Back 67

PVC every other beat

Front 68

(PVCs): Trigeminy:

Back 68

PVC every third beat

Front 69

(PVCs): Ventricular Flutter: describe and tx

Back 69

ribbon-like, "Torsade de Pointes"
• Tx: Mg, β -blocker

Front 70

(PVCs): Ventricular Tachycardia: describe and tx

Back 70

>>3+ consecutive beats with HR> 150, looks like mountains
>>Tx: Amiodarone if BP normal, otherwise tx like V Fib

Front 71

(PCV): Ventricular Fibrillation: describe and tx?

Back 71

No recognizable QRS, looks like quivers
• Tx: Alternate Shock/Drugs (200~> 300~> 360]):

Front 72

In ACLS what does Epinephrine do?

Back 72

lowers threshold for cardioversion

Front 73

In ACLS what does Vasopressin "ADH" do?

Back 73

holds H20 to ⇧BP

Front 74

In ACLS what does Amiodarone do?

Back 74

blocks K, stops all cells

Front 75

In ACLS what does Lidocaine do?

Back 75

blocks Na, stops ventricle, only acts on ischemic tissue

Front 76

In ACLS what does Procainamide do?

Back 76

blocks Na, stops ventricle

Front 77

In ACLS what does Mg do?

Back 77

makes cells less likely to depolarize'

Front 78

when do you synchronize or unsynchronize when you shock?

Back 78

(+) Pulse: synchronize when you shock
No Pulse/V Fib: unsynchronized

Front 79

what are the 3 type of atrial arrythmias?

Back 79

Premature Atrial Contraction:
Atrial Flutter:
Atrial Fibrillation:

Front 80

what is Premature Atrial Contraction?

Back 80

has a pause after it

Front 81

what is Atrial Flutter

Back 81

sawtooth pattern

Front 82

what is Atrial Fibrillation
describe pulse and p waves

Back 82

irregularly irregular, no p waves

Front 83

Atrial Arrhythmias complete tx

Back 83

1) Slow rythym: Diltiazem/Metoprolol (for HR > 120)
2) Increase contraction: Digoxin
3) Chemical Cardioversion: Amiodraone
4) Anticoagulate (for A Fib >48hr): Warfarin, Heparin
>>>Start 3 wk before cardioversion; stop 3wk after sinus rhythm

Front 84

Electrolyte Imbalance (K+, Ca2+, Mg2+) Tx:

Back 84

• Hyperkalemia means there is more K+ in the bloodstream (not the cell)
• Ca2+ and Mg2+ get to the door first in the race with Na +
• Dilute with NS first ... If all else fails, do hemodialysis

Front 85

Low Mg: pathogenesis and mngmt

Back 85

more likely to depolarize ~> monitor DTR, outs, EKG, vitals q10min
• Give Mg sulfate

Front 86

how to calculate corrected calcium

Back 86

Corrected Ca:
0.8 (4-Albumin) + Ca2+

Front 87

what factors can causes increase Ca:

Back 87

• ⇧PTH
• ⇧VitD
• Cancer

Front 88

High Mg management

Back 88

less likely to depolarize
1) Ca Gluconate (move Mg out of the way)
2) Furosemide (pee Mg out)

Front 89

Low Ca: physiology of the cell and management

Back 89

more likely to depolarize
• Ca Gluconate

Front 90

Chovstek's sign:

Back 90

tap facial nerve => muscle spasm

Front 91

Trousseau's sign

Back 91

BP check causes carpal spasm

Front 92

High Ca: mngmtn (5 steps)

Back 92

less likely to depolarize (except atrium)
1) NS
2) Furosemide - pee Ca/Mg out
3) Calcitonin - intranasal
4) Pamidronate (bisphosphonate)- if Ca >16, takes 3 days to work
5) Mithramycin

Front 93

Low K:
depolariation
EKG and why?
mangement and how much?

Back 93

less likely to depolarize, narrow T waves/u waves (K+ leaves => negative cell)
• Give K+ (< 10mEq/hr)

Front 94

High K: management

Back 94

more likely to depolarize, peaked T waves
"Can I Beat K?"
1) Ca gluconate- save the SA node (unless pt is on digoxin)
2) Insulin/Glucose (or Albuterol IV) - pushes K and glucose into cells (Na/glucose ~> Na/K pumps)
3) Bicarb - make kidney pee K+ out
4) Kayexalate- cation exchange resin to poop K out

Front 95

Low Na: mngmnt

Back 95

more likely to depolarize (Na goes out of cell -> Ca flows in -> + cell)
• 0.9% NS (<0.5 mEq/hr to avoid central pontine myelonisis)

Front 96

very low Na (Na <120): mngmnt

Back 96

Seizures: 3% NaCl

Front 97

High Na: mngmnt

Back 97

more (early) then less (late) likely to depolarize
(Na in -> + cell ->Na leaves via Na/ K pump)
Tx: 1/2 NS

Front 98

Low PO4: mngmnt

Back 98

Give phosphate

Front 99

High PO4: mngmnt

Back 99

Refeeding Syndrome in anorexics
1) Ca Carbonate (binds P04 in gut)
2) Insulin/Glucose (rapid P04 exchange)

Front 100

what is milk Alkali Syndrome and tx?
EKG

Back 100

• Eat lots of Ca, short QT
• Tx: IVF ~> Lasix (get rid of Ca)

Front 101

what is a colloid solution?

Back 101

Colloid: Albumin

Front 102

what is a crystalloid solution?

Back 102

Crystalloid: Na

Front 103

what drug increases potassium?

Back 103

ACE-I

Front 104

what beta agonist drug decreases potassium?

Back 104

Albuterol