Cardiovascular Anatomy And Physiology

Question 1

What is the primary determinant of resting membrane potential (RMP)?

Answer 1

Serum potassium (K+)

Question 2

What is the primary determinant of threshold potential?

Answer 2

Calcium

Question 3

How does hypokalemia affect RMP?

Answer 3

Decreased serum K+ ~ potassium leaves the cell for the serum, RMP becomes more negative

Cells become more resistant to depolarization

Question 4

How does hyperkalemia affect the RMP?

Answer 4

Increased serum K+ ~ less K+ leaves the cell ~ RMP is increased

More likely to depolarize

Question 5

How does hypocalcemia affect the threshold potential? (TP)

Answer 5

Less calcium ~ TP becomes more negative ~ also unable to stabilize sodium channels

The cells depolarize more easily

Question 6

How does hypercalcemia affect threshold potential?

Answer 6

Increased Ca ~ threshold potential becomes more positive ~ Ca stabilizes the sodium channels more ~ the cells become more resistant to depolarization

Increases the gap between RMP and TP

Question 7

What is the rest membrane potential for a cardiac myocyte?

Answer 7

-90

Question 8

What happens in phase 0 of the cardiac action potential?

Answer 8

Threshold of -70 is reached, depolarization ~ activation of fast voltage gated Na+ channels

Question 9

What happens in phase 1 of the cardiac action potential?

Answer 9

Initial Repolarization: Inactivation of Na+ channels ~ cell becomes more negative (less positive)

Cl- into cell
K+ out of cell

Question 10

What happens in phase 2 of the cardiac action potential?

Answer 10

Plateau: activation of slow voltage gated Ca channels counter loss of K+ conductance ~ delays repolarization ~ maintains fast Na+ channels in inactivated state ~ prolongs absolute refractory period

This sustained contraction is necessary for the hearts pump

Question 11

What is phase 3 of the cardiac action potential?

Answer 11

Final Repolarization: K+ channels open ~ K+ leaves the cell faster than Ca enters —> Repolarization

Restores membrane potential = -90 mV

Question 12

What is phase 4 of the cardiac action potential?

Answer 12

Resting phase: K+ leak channel opens ~ maintain RMP

Na/K-ATPase pump removes 3 Na and gets 2 K

Question 13

What is the path of conduction in cardiac cells?

Answer 13

SA node > internodal tracts > AV node > bundle of His > Left and Right bundle branches > Purkinje Fibers

Question 14

What is phase 4 of the cardiac nodal cell action potential?

Answer 14

Funny channel leakage (membrane is leaky towards Na+) ~ cell becomes more positive ~ at -50 mV, calcium channels (T-type) open to further depolarize cell

Question 15

What is phase 0 of the cardiac nodal action potential?

Answer 15

Depolarization: Ca enters via voltage gated Ca channels (now L-type) ~ depolarization ~ Na and Ca (Type t channels) close

Question 16

What is phase 3 of the cardiac nodal action potential?

Answer 16

Repolarization: K+ channels open ~ K+ exits cell ~ more negative ~ Repolarizes to repeat Phase 4

Question 17

What is the equation to oxygen delivery?

Answer 17

DO2 = CO x (CaO2) x 10

Question 18

What is a normal oxygen extraction ratio?

Answer 18

25%

Question 19

What is the normal oxygen consumption?

Answer 19

250 mL/min or 3.5 mL/kg/min

Question 20

What is the normal venous content?

Answer 20

CvO2= (Hgb x SvO2 x 1.34) + (PvO2 x 0.003) = 15 mL/dL

Question 21

What is the equation for MAP?

Answer 21

MAP = CO x SVR / 80 + CVP

Question 22

What is Poiseuille’s law?

Answer 22

Q = pie-r4-(pressuregradient)/8nL

Question 23

What does Reynolds number < 2000 predict?

Answer 23

Laminar flow

Question 24

What does Reynolds > 4000 predict?

Answer 24

Turbulent flow

Question 25

What does Reynolds number 2000-4000 predict? LMA

Answer 25

Transitional flow

Question 26

What is the equation for CO? What a normal value?

Answer 26

CO = HR x SV N: 5-6 L/min

Question 27

What is the equation for cardiac index? And what is a normal value?

Answer 27

CO/BSA N: 2.8-4.2 L/min per m2

Question 28

What is the equation for SV? What is a normal value?

Answer 28

SV = EDV-ESV or CO x 1000/HR N: 50-110 mL/beat

Question 29

What is the equation for stroke volume index? What is a normal value?

Answer 29

SV/BSA N: 30-65 mL/beat per m2

Question 30

What is the equation to determine EF? What is a normal value?

Answer 30

EDV - ESV / EDV x 100 N: 60-70%

Question 31

What is a normal MAP?

Answer 31

70-105 mmHg

Question 32

What is the equation for pulse pressure? What is a normal value?

Answer 32

SBP - DBP N: 40 mmHg

Question 33

What is the equation to determine SVR? What is a normal value?

Answer 33

SVR = MAP - CVP / CO x 80 N: 800 - 1500 dynes

Question 34

What is the Equation to determine SVR index? What is normal?

Answer 34

MAP - CVP/ CI x 80 N: 1500-2400 dynes per m2

Question 35

What is the equation to determine PVR? What is a normal value?

Answer 35

MPAP - PAOP / CO x 80 N: 150 - 250 dynes

Question 36

What is the equation to determine PVR index?

Answer 36

MPAP - PAOP/ CI x 80 N: 250 - 400

Question 37

What is preload?

Answer 37

Ventricular wall tension at the end of diastole (just before contraction)

Question 38

What factors increase contractility?

Answer 38

Hypercalcemia SNS stimulation Catecholamines Calcium Digitalis Phosphodiesterase inhibitors

Question 39

What factors decrease contractility?

Answer 39

Myocardial ischemia Severe acidosis Hypercapnia Hypocalcemia Hypoxia Hyperkalemia (doesn’t allow Na channels to repolarize) Volatile anesthetics Propofol Beta-blockers Calcium channel blockers

Question 40

How does Beta 1 stimulation work increase contractility?

Answer 40

Beta 1 ~ activates enzyme adenylate cyclase ~ convert ATP to cAMP ~ cAMP activates PKA ~ PKA does 3 things 1. Activates more L-type ca channels 2. Stimulates the ryanodine receptor to release more Ca from SR 3. Increase SERCA2 receptor activity (increase Ca reuptake, thus increase supply for Ca release)

Question 41

What is the equation to myocardial wall stress?

Answer 41

Wall stress = intraventricular pressure x Radius / ventricular thickness

Question 42

What factors are proportional to an increase in myocardial walk stress?

Answer 42

Radius, intraventricular pressure

Question 43

What factor is inversely proportional to wall stress?

Answer 43

Ventricular Wall thickness

Question 44

When considering the wiggers diagram, what are the two factors included in systole?

Answer 44

Isometric ventricular contraction Ventricular ejection

Question 45

What are key events during isometric ventricular contraction?

Answer 45

LV pressure > LA pressure —> mitral valve closes (1st heart sound) LV pressure builds LV volume constant (usually both valves are closed during isometric contraction)

Question 46

What are the key events during Ventricular systole?

Answer 46

LV pressure > Aortic pressure —> aortic valve opens Stroke volume is ejected into the aorta (Most is ejected during first 1/3 of systole)

Question 47

When considering the Wiggers diagram, what components make up diastole?

Answer 47

Isometric relaxation Rapid LV filling Reduced LV filling Atrial Systole

Question 48

What are the key events during isometric ventricular relaxation?

Answer 48

Aortic pressure > LV pressure —> AV valve closes (2nd heart sound) LV pressure decreases LV volume remains constant ( both valves are usually closed at this point)

Question 49

What are the key events during rapid ventricular filling?

Answer 49

LA pressure > LV pressure —> mitral valve opens LV pressure remains constant LV volume changes 80% of filling happens during this period

Question 50

What are the key events in reduced ventricular filling? (Diastasis)

Answer 50

LV filling continues but at a slower rate

Question 51

What are the key events during atrial systole?

Answer 51

LA contraction —> atrial kick contributes 20% of LV filling The end of atrial systole correlates with end-diastolic volume

Question 52

Where is DBP measured?

Answer 52

Where the aortic valve opens

Question 53

Where is SBP measured?

Answer 53

Peak of the ejection curve

Question 54

What is considered a normal EF?

Answer 54

> 50%

Question 55

What EF % is considered mild dysfunction?

Answer 55

41-49%

Question 56

What EF % is considered moderate dysfunction?

Answer 56

26-40%

Question 57

What EF % is considered severe dysfunction?

Answer 57

< 25%

Question 58

How can we estimate the LV’s external work (EW)? When considering pressure-volume loops

Answer 58

Multiplying SV (width) by the mean aortic pressure (height)

Question 59

What is the key point when considering increased preload in a pressure-volume loop?

Answer 59

Loop gets wider, BUT returns to the original end-systolic volume (Fluid bolus)

Question 60

What is the key point when considering decreased preload in a pressure-volume loop?

Answer 60

Loops gets narrow, BUT returns to the original end-systolic volume (Lasix)

Question 61

What is the key point of increased contractility when considering pressure-volume loops?

Answer 61

The loop gets wider, taller, and shifts to the left. (Increased SV ~ decreased ESV) Beta 1 stimulation

Question 62

What is the key point of decreased contractility when considering pressure-volume loops?

Answer 62

The loop gets narrower, short, and shifts to the right (Heart failure)

Question 63

What is the key point of increased afterload when considering pressure-volume loops?

Answer 63

The loop gets narrower, taller, and shifts the ESV to the right (Acute hypertension)

Question 64

What is the key point of decreased afterload when considering pressure-volume loops?

Answer 64

The loop gets wider, shorter, and shifts the ESV to the left. (Vasodilators)

Question 65

Where does the SA node receive its blood supply?

Answer 65

Usually the RCA

Question 66

Where does the AV node receive its blood supply?

Answer 66

Usually the RCA

Question 67

Where does the Bundle of His receive its blood supply?

Answer 67

LCA

Question 68

Where do the rt and lt. bundle branches receive their blood supply?

Answer 68

LCA

Question 69

What are the three main coronary veins and what artery do they run alongside?

Answer 69

Great cardiac vein (LAD) Middle cardiac vein (PDA) Anterior cardiac vein (RCA)

Question 70

Which leads related to the lateral aspect of the heart? Aka affect the circumflex artery

Answer 70

1, aVL, V5, V6

Question 71

Which leads relate to the inferior side of the heart? Aka affect the RCA?

Answer 71

II, III, aVF

Question 72

Which leads related to the septal aspect of the heart? Aka affect a portion of the LAD?

Answer 72

V1, V2

Question 73

Which leads relate to the anterior side of the heart? Affect a portion of the LAD?

Answer 73

V3, V4

Question 74

In regards to TEE, which view is best for diagnosing LV ischemia?

Answer 74

Midpapillary muscle level in short axis Second best is apical segment…also in short axis

Question 75

At rest, how much oxygen does the myocardium consume?

Answer 75

8-10 mL/min/100g

Question 76

What is the extraction ratio of the myocardium when it is at rest?

Answer 76

70%

Question 77

What is the equation for coronary blood flow?

Answer 77

Coronary blood flow = coronary perfusion pressure / coronary vascular resistance

Question 78

What is the equation for coronary perfusion pressure?

Answer 78

Coronary perfusion pressure = Aortic DBP - LVEDP

Question 79

What is the normal range the coronary blood flow autoregulates to?

Answer 79

60-140 mmHg

Question 80

What is Adenosine?

Answer 80

Byproduct of ATP metabolism and is a potent coronary vasodilator

Question 81

What are some causes of coronary artery dilation?

Answer 81

Beta-2 agonist (increase cAMP ~ decrease MLCK sensitivity to Ca) Histamine 2 ( increase cAMP ~ decrease MLCK sensitivity to ca) Muscarinic ~ increase nitric oxide

Question 82

What are some causes of coronary constriction?

Answer 82

Alpha stimulation (increase intracellular Ca) Histamine 1 ( increase intracellular Ca)

Question 83

What are some factors that decrease oxygen delivery? Think cardiac

Answer 83

Tachycardia (decrease diastole/filling time) Decrease in aortic pressure Decrease in vessel diameter (spasm or hypocapnia) Increase in LV end-diastolic pressure Decreased CaO2 (hypoxemia, anemia) Decrease O2 extraction (left shift ~ decrease in P50) Decreased capillary density

Question 84

What are some factors that increase oxygen demand?

Answer 84

Tachycardia Hypertension SNS stimulation Increased wall tension Increased LV end diastolic volume Increased afterload Increased contractility

Question 85

When do most postoperative MIs occur?

Answer 85

24-48 hours

Question 86

What is the basic sequence in a G-protein response?

Answer 86

First messenger —> g-protein coupled receptor —> effector —> second messenger —> cellular response

Question 87

In terms of vascular smooth muscle, what is the G-protein cAMP pathway lead to?

Answer 87

Vasodilation

Question 88

In terms of vascular smooth muscle, what does the Nitric Oxide cGMP pathway produce?

Answer 88

Vasodilation

Question 89

In terms of vascular smooth muscle, what does the Phosholipase C pathway produce?

Answer 89

Vasoconstriction!!!

Question 90

What is the nitric oxide pathway ~ simplified

Answer 90

Nitric oxide synthetase is an enzyme that catalyzes the conversion of L-ravine to nitric oxide —> this diffuses from endothelium to smooth muscle —> activates guanylate cyclase —> guanylate cyclase converts GTP to GMP. Increased GMP reduced intracellular Ca

Question 91

What is the Phospholipase c pathway for vascular smooth muscle vasoconstriction?

Answer 91

Angiotensin II —> ATII receptor —> Gq G-protein —> phospholipase C —> IP3 and DAG —> increased Ca —> vasoconstriction