Heart Week 1b: Rhythmns, etc.

Question 1

PSVT

Answer 1

Paroxysmal Supraventricular Tachy:

a. sudden onset and termination
b. atrial rates between 140 and 250 bpm
c. normal QRS
d. often causes by reentry

Question 2

Tachycardia

Answer 2

Heart rate > 100bpm

Question 3

Sinus Bradycardia

Answer 3

P and QRS is normal, but rate is < 60bpm

Question 4

Escape Rhythm

Answer 4

a. normal QRS but no P

b. wide QRS, maybe no P (Ventricular)

Question 5

Tell me about the three AV blocks.

Answer 5

a. 1st Degree: PR interval > 5 small boxes (0.2 secs)
b1. 2nd Degree, Mobitz: P is constant, but QRS gets closer and closer until a P happens with no QRS
b2. Mobitz II: all looks normal, then QRS drops out, sometimes the QRS is wide
c. 3rd degree: aka- complete block, QRS and P are completely independent

Question 6

What is normal sinus rhythm?

Answer 6

60-100 bpm

Question 7

What is sinus tacky?

Answer 7

100-180 bpm

Question 8

What is Reentrant SVT?

Answer 8

a. 140-250 bpm
b. P wave is hidden or retrograde
c. may abruptly terminate

Question 9

Focal Atrial Tachy

Answer 9

a. 130-250 bpm
b. P wave is not normal, but presentation may vary
c. AV block may increases, but rarely reverts

Question 10

Atrial Flutter

Answer 10

a. 180-350 bpm
b. “saw-toothed” (different from atrial fibrillation)
c. AV block may increase

Question 11

Atrial Fibrillation

Answer 11

no distinct P waves (different than atrial flutter)

Question 12

Give me the M/E (mechanism/Example) for decreased automaticity

Answer 12

M: decrease in phase 4 depolarization, eg- parasympathetic stimulation

E: sinus bradycardia

Question 13

give me the M/E for conduction block.

Answer 13

M: ischemia, anatomics or drug-induced impaired conduction

E: 1st, 2nd, and 3rd degree AV block

Question 14

Give me the M/E for sinus node enhanced automaticity.

Answer 14

M: increased phase 4 depolarization, e.g.- sympathetic stimulation.

E: sinus tachycardia

Question 15

Give me the M/E for enhanced automaticity of the AV node, ectopic focus

Answer 15

M: acquires phase 4 depolarization

E1: AV junctional tachy
E2: ectopic atrial tachy and some forms of VT

Question 16

Gimme the M/E of DAD (delayed afterdepolarization).

Answer 16

M: high intracellular Ca++ (e.g.- digitalis toxicity)

E: premature atrial/ventricular beats, idiopathic VT and digitalis

Question 17

Gimme the M/E of EAD.

Answer 17

M: prolonged AP duration

E: Torsades de Pointe

Question 18

Compare DAD and EAD.

Answer 18

DAD: has p wave very soon after QRS

EAD: has p wave while QRS is still happening, ends up with a P wave that can look like an M.

Question 19

What channels can cause the EAD?

Answer 19

a. during phase 2, it is most likely Ca++

b. during phase 3, it is most likely a recovery of some inactivated Na+ channels

Question 20

What causes a DAD?

Answer 20

high intracellular Ca++ concentration, can be caused by digitalis toxicity.

Question 21

What is the difference between ionotropic and metabotropic receptors?

Answer 21

Ionotropic: becomes a channel, ion flows right in, acts more quickly

Metabotropic: uses a second messenger like G-protein, acts slower, ion does not enter the cell.

Question 22

During what part of the EKG are the K+ channels maximally open?

Answer 22

Q-T Interval.

Most K+ channels are opened when the cell depolarizes and stay open until repolarization.

Question 23

Why is the done by the left ventricle greater than the work done by the right ventricle?

Answer 23

Work is proportional to output. Since the R/L ventricles have equal output, then you consider the resistance against which it moves, AFTERLOAD. Aortic pressure is greater than the pulmonary pressure, so the L ventricle does more work.

Question 24

What area of the heart does the LAD supply?

Answer 24

apex, ant wall of LV and ant 2/3 of septum

Question 25

What area of the hear does the LCX supply?

Answer 25

lateral wall of LV.

Question 26

What area of the heart does the RCA supply?

Answer 26

RV free wall, post 1/3 of sept, posterior wall of LV.

Question 27

How big are arterioles? What surrounds them?

Answer 27

10-60 microns with 1-5 layers of smooth muscle.

Question 28

How big are capillaries? What surrounds them?

Answer 28

5-10 microns in diameter (aout 0.5 to 1.0 mm in length). No smooth muscle.

Question 29

How big are venules? What surrounds them?

Answer 29

~10-60 microns in diameter. No smooth muscle.