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Hemodynamics Flashcards

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USMLE® Step 1 flashcards
1
Q

What is the formula for Fick CO?

A

CO = O2 consumption (mL/min) / VO2 difference (mL/100mL blood) x10

  • O2 consumption estimated using 3 mL O2/kg or 125 mL/min/m2
  • VO2 difference = difference (0.95 - 0.65) x 1.36 x Hgb x 10

**** Larger difference between A and V O2 content –> lower CO

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2
Q

What is the formula for cardiac index (CI)?

A

CI = CO (L/min) / BSA (m2)

  • normal = 2.5 - 4 L/min/m2
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3
Q

When is Fick (CO) most accurate?

A
  • low output states (valvular heart disease)
    • TR
    • multivalvular heart disease
  • steady state
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4
Q

What is the problem with Fick (CO)?

A

estimate of O2 consumption

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5
Q

What PA sat correlates with low CO (on Fick)?

A

< 65%

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6
Q

What are quick estimates of Fick (CO) utilizing PA sats?

A
  • PA sat 70-80% –> Normal CO
  • PA sat < 65% –> Low CO
  • PA sat > 80% –> High CO (or L-R shunt)
    • AV graft for HD
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7
Q

When is TD (CO) more accurate?

Least accurate?

A
  • Most accurate –> High Output States
  • Inaccurate –> TR or AF
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8
Q

What is the formula for PVR (pulmonary vascular resistance, Woods units)?

A

PVR = mPAP - mPCWP / CO

**Normal range = 80-130 dynes

***Woods units x 80 = dynes

**** TPR = mPAP / CO

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9
Q

What is the formula for SVR (systemic vascular resistance)?

What is normal range?

A

SVR = mean systemic arterial pressure - mRAP x 80 / CO

  • Normal range = 700-1600 dynes-sec/cm5
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10
Q

Describe the finding

A

Severe TR

  • monophasic “CV” wave
    • CV wave lifted completely off the baseline
    • monophasic event in systole, occurring within the RA
  • ventricularization of RA waveform
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11
Q

What constitutes a pathologic or abnormal “v” wave in PCWP tracings?

What are causes?

A
  • “v” wave more than 10 mmHg than PCWP
  • PCWP “v” waves
    • MR
    • VSD
    • Noncompliant LA
      • previous A-fib ablation procedures
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12
Q

Describe the findings

A

Pericardial Tamponade

  • Rapid x only
  • Blunted ‘y’ descent (no early diastolic RV filling)
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13
Q

Describe the findings

A

Pericardial constriction

  • Rapid x and y descents
    • y = early rapid diastolic RV filling
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14
Q

Describe when step-up O2 saturations are significant?

What does this imply?

A

Intra or Extra cardiac shunt may be present

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17
Q

Describe the findings

A
  • a = atrial systole
  • x = atrial relaxation, decrease of pressure
  • c = closure of the TV
  • v = ventricular systole, atrial diastole
  • y = passive filling of the RV
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21
Q

Describe the findings

A

HOCM - Brockenbrough sign

  • PVC –> ventricular contraction will be more forceful, and the pressure generated in the LV will be higher
    • reduction in pulse pressure in a post-PVC beat
      *
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22
Q

How can you differentiate AS and HOCM on intracardiac pressure tracings?

A

Post-PVC

  • Pulse Pressure
    • HOCM –> decrease
    • AS –> increase

Valsalva

  • Gradient
    • ​HOCM –> increase
    • AS –> decrease
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23
Q

Describe the findings

A

AS

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24
Q

Describe the findings

A

HOCM: L heart pullback

25
Q

Describe the findings

A

Provocable Gradient: Valsalva Maneuver

26
Q

Describe locations for mixed venous O2 sats in shunt calculations:

  • No L-R shunt
  • L-R shunt present
  • ASD
  • No R-L shunt
A
  • No L-R shunt
    • Mixed venous = PA sat
  • L-R shunt present
    • Mixed venous = O2 sat in chamber proximal to shunt
  • ASD
    • Mixed venous = Caval O2 sat = (3 x SVC) + (1 x IVC) / 4
  • No R-L shunt
    • Mixed venous = PV O2 sat = FA O2 sat
27
Q

What is a normal BP response to exercise?

A

25-70 mmHg

28
Q

Describe the findings

A

ASD

29
Q

Describe the findings

A

AR

  • Corrigan’s pulse
  • absence of dicrotic notch
31
Q

What is the Gorlin formula?

A

Area (cm2) = value flow (mL/s) / K x C x √MVG

  • K = constant = 44.3
  • C = empiric constant
    • AV, TV, PV = 1
    • MV = 0.85

***MV flow = CO / DFP x HR

***AV flow = CO / SEP x HR

32
Q

What is the simplified Gorlin or Hakki formula?

When does this formula differ?

A

AVA = CO / √MG

  • differs by 18% +/- 13% from real formula
    • Bradycardia
    • Tachycardia
    • Low flow states –> overestimate severity of AS
      • CO < 2.5 L / min –> constants should be used
33
Q

When is the Gorlin formula inaccurate?

A
  • Regurgitation (concomitant)
    • moderate or more AI
  • Low output states
  • Tachy/Brady cardia

***Assumes steady state and fixed orifice

39
Q

What are factors that can increase the gradient in HOCM?

A
  • increased contractility
  • decreased preload
    • volume depletion
  • decreased afterload
40
Q

What are factors that can decrease the gradient in HOCM?

A
  • decreased contractility
  • increased preload
  • increased afterload
    • phenylephrine
41
Q

What is a normal LVOT VTI?

A

18-22 cm

  • important to avoid PISA / flow convergence –> leads to overestimation
42
Q

Calculate MVA?

A

MVA = 220 / PHT

  • PHT = deceleration time x 0.29
  • PHT = the time required for the velocity to drop to 1/2 the peak pressure
43
Q

What is the grading severity of mitral stenosis?

A
44
Q

What is the diagnosis?

  • 65 year old man
  • severe exertional dyspnea
A

severe AS

  • delayed aortic pressure uprise
  • PVC with compensatory pause –> increase in aortic pulse pressure
45
Q

Describe the findings and key to differentiation

A

Pulse pressure change on post-PVC beat

  • Severe AS
    • increase in PP –> increased filling and more flow across the valve
  • HOCM (“Brockenbrough-Braumwald” sign)
    • decrease in aortic pulse pressure
      • increased intracellular calcium –> contractility
      • aortic pressure runoff –> decreased afterload –> worsening obstruction
46
Q

Describe the findings

A

Post-PVC aortic pulse pressure tracings

  • severe AS
  • HOCM
47
Q

Describe the findings

A

Severe AR

48
Q

Describe the findings

A

Acute severe AR

  • diastolic equalization of pressures between LV and aorta
49
Q

Describe the findings

A

Severe AR

  • early closure of the Mitral valve
    • well before onset of systole
  • elevated LVEDP
50
Q

Describe the findings and diagnosis

A
  • Mitral inflow
    • Inspiration –> decrease in mitral inflow velocity
    • Expiration –> increase in mitral inflow velocity
51
Q

Describe the findings and diagnosis

A

Effusive constrictive pericarditis

  • Pericardial tamponade –>
  • pericardiocentesis –>
  • Constrictive pericarditis
52
Q

Describe the findings and diagnosis

A

Mitral annular velocity –> important measure for differentiation

53
Q

Describe the findings, diagnosis, treatment

A

Constrictive pericarditis –> Pericardiectomy

  • Diastolic equalization of pressures
  • Diastolic pressures elevated
  • Ventricular discordance
  • Enhanced ventricular interaction
54
Q

What are key hemodynamic criteria to differentiate RCM and CP?

A
  • LVEDP - RVEDP
    • Constriction
    • Restriction > 5
  • RVSP
    • Constriction < 50
    • Restriction > 50
  • RVEDP/RVSP
    • Constriction > 0.3
    • Restriction < 0.3
55
Q

Describe the findings, diagnosis, treatment

A

Severe MS –> PMBV –> Pericardial tamponade

  • Pericardiocentesis
56
Q

Calculate the Qp/Qs

  • High SVC 67%
  • IVC 75%
  • RA 87%
  • RV 88%
  • PA 89%
  • PCWP 99%
  • CO 5 L/min
  • Hgb 12 g/dl
A

Qp/Qs = 3.0

57
Q
A

Medical (69 decks)

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