Valvular Heart Disease: Overview, Stenosis, Pathology

Question 1

What kind of load does a stenosis put on the heart?

Answer 1

pressure

Question 2

What kind of load does regurgitation put on the heart?

Answer 2

volume

Question 3

What does stenosis do to pressure load?

Answer 3

increases the pressure gradient across the valve –> requires increased pressure from upstream chamber, impairs ability to increase CO

*chronic disorder and the heart’s ability to cope is determined by the upstream chamber’s ability to increase pressure to compensate

Question 4

What does regurgitation do to volume load?

Answer 4

backward flow of blood into upstream chamber –> increases volume load on both chambers, reduce ability to increase CO (but not as much as stenosis)

*acute/chronic and heart’s ability to cope is determined by volume capabilities of both affected chambers

Question 5

What’s the difference between aortic and mitral regurg?

Answer 5

aortic increases wall stress during diastole and systole whereas mitral regurgitation increases diastolic wall stress only

Question 6

What is the consequence of reduced orifice size in valve stenosis?

Answer 6

need to achieve higher flow velocity to achieve physiologic flow rate –> requires higher pressure gradient –> higher pressure load on upstream chamber

Question 7

How is the pressure gradient related to the velocity through a valve?

Answer 7

Bernoulli –> pressure is proportional to velocity^2

Question 8

How does the flow rate change as x-sectional area decreases?

Answer 8

it doesn’t –> fluid is incompressible –> flow rate is constant, flow velocity changes AKA same amount of fluid crosses over a smaller orifice but it has to go faster to ensure same volume/time is passing

Question 9

How does the flow velocity change as x-sectional area decreases?

Answer 9

it increases linearly as per continuity of flow equation

Question 10

How is flow rate related to CO and time available for flow?

Answer 10

linear and inversely –> the more CO, the higher the flow rate; the less time, the higher the flow rate

Question 11

What is the implication of the Gorlin Valve Area equation?

Answer 11

x-sectional area of valve = F/sqrt (pressure difference) –> change in pressure = F^2/kA^2 –> smaller area = higher flow velocity and greater pressure gradient in stenosis

Question 12

Why do we need to measure CO when determining severity of stenosis?

Answer 12

At low flow rates, even with a small orifice area, the valve pressure gradient may be deceptively small –> need to know how velocity changes to figure out how stenotic a valve is –> challenge CO

Question 13

What is the heart’s adaptive response to aortic stenosis and how is that response limited?

Answer 13

concentric left ventricular hypertrophy

1. limits diastolic compliance/need higher filling pressure
2. coronary circulation and CAD limit hypertrophy
3. fibrosis degrades myocardial performance
4. progression of stenosis severity

Question 14

How do we get angina pectoris in AS?

Answer 14

increased wall thickness negatively affects perfusion leading to chest pain

Question 15

How do we get syncope/presyncope in AS?

Answer 15

inadequate CO response to exercise can lead to hypotension/ischemia which can provoke further arrhythmia

Question 16

How do we get CHF in AS?

Answer 16

inadequacy of LV hypertrophy to normalize systolic wall stress leads to degradation of contractile performance (systolic HF) and diastolic compliance (diastolic HF) resulting in progression of obstruction severity

Question 17

T/F if a pt is asymptomatic but has AS, their compensatory mechanisms are working

Answer 17

T –> stuff is probably working ok but has reduced exercise capacity

Question 18

If you have symptomatic AS what should you do?

Answer 18

get a valve replacement asap

Question 19

What is a “sinking aortic”?

Answer 19

someone with AS who is decompensating like heck –> progressing to cardiogenic shock (low pressure, low cardiac index, tanking pressure gradient b/c of low CO)

Question 20

What happens to flow velocity in mitral stenosis?

Answer 20

greater and more sustained diastolic flow velocity with turbulence (vs. slower and uniform flow velocity with decrease in velocity by mid diastole)

Question 21

How does the LA-LV pressure gradient in MS compare to the LV-Ao pressure gradient in AS?

Answer 21

it is smaller in quantity but still substantial –> attenuated y descent

Question 22

What is the interaction between MS and heart rate?

Answer 22

mitral stenosis is adversely affected by heart rate –> velocity decay decreases as duration of diastole decreases –> makes pressure gradient worse –> progressive rise of left atrial pressure during short cardiac cycles

Question 23

How does the heart cope with MS?

Answer 23

it can’t

Question 24

What are the consequences of MS?

Answer 24

1. LA pressure> 30 mmhg is poorly tolerated by pulm. capillaries –> venous htn w/ secondary artery htn (SOB, arteriolar constriction leading to destruction of alveoli AKA irreversible increase in PVR) –> right ventricular afterload excess –> rv dilation, tricuspid regurg and systemic venous htn
2. dilation of LA limits contractility and reduces LV preload
3. exercise increases heart rate and worsens the atrial state by reducing diastolic filling time and thereby increasing atrial pressures (b/c of slow decay of pressure)
4. chronic atrial dilation leading to chronic atrial fibrillation –> reduces heart rate regulation
5. left atrial enlargement
6. sluggish flow –> thrombosis/emboli

Question 25

How do we deal with sluggish flow in MS?

Answer 25

warfarin once a-fib develops --> thrombus risk from slow flow

Question 26

Why do mild MS become symptomatic vs mild AS?

Answer 26

don't have adaptive mechanisms however don't deteriorate as fast as symptomatic AS (which occurs upon decompensation) --> gradual over years

Question 27

3 layers of valve leaflets

Answer 27

1. fibrosa (back/outflow surface of valve continuous with annulus fibrosis) 2. spongiosa (centrally located and comprised of loose connective tissue) 3. ventricularis (closest to inflow surface and rich in elastic fibers)

Question 28

Vascularization of a valve leaflet suggests...

Answer 28

marker of prior inflammation

Question 29

Aortic stenosis is most often due to

Answer 29

degenerative/dystrophic calcification of a normal or bicuspid valve --> wear and tear/senile

Question 30

Mitral stenosis is most often due to

Answer 30

chronic rheumatic heart disease

Question 31

Aortic regurgitation is most often due to

Answer 31

to dilation of the aortic root as a function of old age, atherosclerosis and hypertension

Question 32

Mitral regurgitation is most often due to

Answer 32

myxomatous degeneration, dilation of mitral valve ring w/ LV dilation due to LV failure

Question 33

How does dystrophic calcification of valve leaflets occur?

Answer 33

turbulent blood flow leads to wear and tear damage --> stromal cells undergo phenotypic change and deposit calcium and fibrosis during repair process *turbulence is why it affects mitral and aortic valve more

Question 34

Is dystrophic calcification a type of atherosclerosis?

Answer 34

no --> not related to lipid profile

Question 35

Calcification of the aortic valve leaflets is | most often associated with

Answer 35

aortic stenosis

Question 36

calcification of the mitral valve annulus can be associated with

Answer 36

mitral regurgitation

Question 37

Where does calcium get deposited on a leaflet and why is this important?

Answer 37

middle of leaflet protruding into sinuses of valsalva on outflow side --> limits leaflets' ability to open --> stenosis

Question 38

Is there fusion of leaflet commissures in dystrophic calcification?

Answer 38

no --> distinguishes this from rheumatic valvular disease

Question 39

When does aortic valve calcification tend to become symptomatic?

Answer 39

eighth to ninth decade

Question 40

T/F congenitally deformed aortic valves develop symptomatic calcifications earlier

Answer 40

T --> more turbulence

Question 41

When do bicupsid aortic valves (abnormal) calcifications tend to become symptomatic?

Answer 41

5th to 6th decade --> unequal w/ or w/o raphe on larger

Question 42

When do unicuspid aortic valves (abnormal) calcifications tend to become symptomatic?

Answer 42

2nd to 4th decade

Question 43

Where does calcification take place in the mitral valve?

Answer 43

in the valve ring/annulus vs. the leaflets in Ao valve stenosis

Question 44

Who gets mitral dystrophic calcification?

Answer 44

elderly women w/chronically increased LV pressures or myxomatous degeneration --> usually asymptomatic but can cause regurg, rarely erodes into conduction system

Question 45

What is acute rheumatic fever?

Answer 45

an acute, multisystem inflammatory disease triggered by an abnormal immune reaction to pharyngitis caused by group A beta hemolytic Streptococcus --> can injure all layers of the heart and sequential episodes can become chronic rheumatic heart disease leading to injury to valves over years

Question 46

what is the pathology of chronic rheumatic heart disease CRHD?

Answer 46

fibrosis, thickening, and retraction of the valve leaflets, often with fusion of the commissures (the sites where the free edges of adjacent leaflets attach to the underlying chamber [or arterial] wall) w/also shortening, thickening and fusion of chordae tendineae

Question 47

_________is the pathologic hallmark of CRHD

Answer 47

Commissural fusion

Question 48

Which valves are affected by CRHD?

Answer 48

most often the mitral valve (65-70%), | sometimes with the aortic valve as well (25%), and less commonly the right sided valves.

Question 49

Pure MS results in

Answer 49

left atrial dilation, atrial fibrillation, atrial thrombus, and possible arterial embolization

Question 50

MS + MR results in

Answer 50

left atrial dilation, atrial fibrillation, atrial thrombus, and possible arterial embolization PLUS left ventricular hypertrophy

Question 51

What risk is associated with scarred valves

Answer 51

infection

Question 52

Most common cause of aortic regurg

Answer 52

Dilation of aortic root is by far the most common cause (old age, medial degeneration, Marfan’s) can also tear a leaflet in infectious endocarditis, retract a valve leaflet in CRHD, fixate valve leaflets in dystrophic calcification or CRHD

Question 53

What kind of hypertrophy results from aortic regurg?

Answer 53

eccentric hypertrophy of LV

Question 54

Myxomatous degeneration of the mitral valve (and less often other cardiac valves) is characterized by

Answer 54

increased deposition of extracellular matrix material (mucopolysaccharides) in the spongiosa layer and attenuation of the fibrosa layer, associated with elongation and thickening of the valve leaflets and, as well as elongation and thinning of chordae tendineae --> valve prolapse into atrium *can be due to inherited disorder of structural proteins/increased deposition of ECM/stretching of cordae

Question 55

Is myxomatous degeneration of mitral valve symptomatic?

Answer 55

not commonly 1. asymptomatic systolic click 2. thrombus formation and endocarditis 3. dysrhythmia leading to syncope/sudden death 4. mitral regurg and late systolic murmur

Question 56

What underlying hereditary connective tissue defect may be associated with myxomatous degeneration?

Answer 56

Very similar changes occur in the cardiac valves of some patients with systemic defects in connective tissue (e.g. patients with Marfan’s syndrome), suggesting that some, if not all, patients with myxomatous degeneration of valves may have an underlying hereditary connective tissue defect that predisposes to an abnormal tissue response to the hemodynamic stresses to which valves are normally subjected.

Question 57

Acute pulmonary effects of LAP increase

Answer 57

venous congestion, stiff lung, interstitial/alveolar edema resulting in SOB

Question 58

Chronic pulmonary effects of LAP increase

Answer 58

1. fibrosis of pulmonary veins and hemosiderin deposition in the lungs from leakage of red blood cells as part of chronic passive congestion 2. intimal fibroelastic hyperplasia and medial muscular hypertrophy --> fixed elevation of PVR and permanent increase in pulmonary artery pressure 3. right ventricular hypertrophy and right heart failure 4. Atherosclerotic lesions in larger pulmonary arteries

Question 59

T/F All cases of infectious endocarditis are caused by bacteria

Answer 59

F --> most but other microorganisms can also be responsible, such as fungi, rickettsiae (Q fever), chlamydia, or viruses.

Question 60

What is the pathogenesis of bacterial endocarditis?

Answer 60

combination of bacteremia and a preexisting deposit of fibrin on a valvular (or endocardial, endothelial or prosthetic) surface--> bacteria take refuge in the fibrin, proliferate, incite acute inflammation and progressive enlargement of the deposit--> invasion of the organism into underlying valve--> bacteria and/or their antigens are periodically shed-->immune complex formation (e.g. acute nercrotizing glomerulonephritis)--> injury at other remote sites

Question 61

What causes acute bacterial endocarditis and how does it present?

Answer 61

virulent bacteria (e.g. Staphylococcus aureus or enteric gram negative bacteria), has a cataclysmic onset with high fever, chills, aggressive clinical course (untreated leading to death within a few weeks), and can occur on previously normal cardiac valves, as well as previously damaged valves

Question 62

What causes subacute bacterial endocarditis and how does it present?

Answer 62

less virulent bacteria (e.g. Streptococcus, especially viridans) with a more subtle onset of symptoms with fever, malaise, weight loss, a clinical course leading to death in a few months if untreated, and occurring on previously damaged, rather than normal, heart valves --> can be cured w/ IV abs

Question 63

Tx of subacute bacterial endocarditis

Answer 63

iv abs --> curable

Question 64

Tx of acute bacterial endocarditis

Answer 64

surgery + antibiotics --> 50% mortality

Question 65

What is non-bacterial thrombotic endocarditis?

Answer 65

NBTE occurs in pts w/o bacterial infection but with endocardial injury due to turbulent blood flow + hypercoagulable state --> can facilitate secondary bacterial infection

Question 66

What is the pathogenesis of bacterial endocarditis?

Answer 66

combination of bacteremia and a preexisting deposit of fibrin on a valvular (or endocardial, endothelial or prosthetic) surface--> bacteria take refuge in the fibrin, proliferate, incite acute inflammation and progressive enlargement of the deposit--> invasion of the organism into underlying valve--> bacteria and/or their antigens are periodically shed-->immune complex formation --> injury at other remote sites

Question 67

What causes acute bacterial endocarditis and how does it present?

Answer 67

virulent bacteria (e.g. Staphylococcus aureus or enteric gram negative bacteria), has a cataclysmic onset with high fever, chills, aggressive clinical course (untreated leading to death within a few weeks), and can occur on previously normal cardiac valves, as well as previously damaged valves

Question 68

What causes subacute bacterial endocarditis and how does it present?

Answer 68

less virulent bacteria (e.g. Streptococcus, especially viridans) with a more subtle onset of symptoms with fever, malaise, weight loss, a clinical course leading to death in a few months if untreated, and occurring on previously damaged, rather than normal, heart valves --> can be cured w/ IV abs

Question 69

Which organisms associated with endocarditis: IV drug users

Answer 69

Right sided, especially! --> staph aureus, candida, aspergillus

Question 70

Tx of acute bacterial endocarditis

Answer 70

surgery + antibiotics --> 50% mortality

Question 71

What is non-bacterial thrombotic endocarditis?

Answer 71

NBTE occurs in pts w/o bacterial infection but with endocardial injury due to turbulent blood flow + hypercoagulable state --> can facilitate secondary bacterial infection

Question 72

Which organisms associated with endocarditis: normal valves

Answer 72

staph aureus, gram -'s

Question 73

Which organisms associated with endocarditis: abnormal valves

Answer 73

strep viridans

Question 74

Which organisms associated with endocarditis: prosthetic valves

Answer 74

staph epidermidis, staph aureus, strep

Question 75

Which organisms associated with endocarditis: IV drug users

Answer 75

staph aureus, candida, aspergillus

Question 76

Which hypercoagulable states predispose to NBTE?

Answer 76

low grade DIC, mucin producing adenocarcinomas, sepsis, burns