Case 4 - Aortic Stenosis Flashcards

1
Q

What are the classic symptoms of AS and why do they occur?

A

Symptoms: Angina, syncope, CHF

1) Angina

  • inc o2 consumption 2/2 LVH
  • decrease CPP
    • inc LVEDP
    • dec diastolic time 2/2 prolong isovolumic relaxation phase - > dec coronary perf time
    • decrease forward flow - > dec aortic diastolic pressure

2) syncope
* dec forward flow, dec CO, dec perfusion to brain
3) CHF

  • eventually heart has exceeded its capacity to compensate for pressure work with LVH.
  • will dilate -> lead to systolic dysfunction -> back flow of blood
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2
Q

what is the pathophys behind AS and LV function?

A

In order

  • AS - > increase LV pressure required to generate forward flow
  • concentric LVH w/o dilation
    • laplace law. increase wall thickness to offset increase intraventricular pressure
  • hypertrophied myocardium
    • inc O2 consumption
    • diastolic dysfunction - > LVEDP is increased
      • decrease CPP
      • decreased cardiac filling (dec size of chamber)
  • isovolumic phase of relaxation prolonged
    • shortens period of disatole
    • diminishes time for coronary perfusion
  • Systolic Dysfunction at the end
    • cannot maintain forward flow, heart dilates
      • left sided CHF
      • decrease aortic diastolic pressure
        • dec CPP
      • decrease CO (dec SV)
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3
Q

etiology of AS

A

contenital bicuspid valve

senile calification of trileaflet aortic valve

rhemuatic AS

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4
Q

what is normal AVA, what is considered severe AS?

A

Normal AVA = 2.5 - 3.5 cm2

Severe AS

  • AVA < 1.0 cm2
  • mean transvalvular gradient > 40 mm Hg
  • peak pressure gradient > 80 mm Hg
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5
Q

why is it important to maintain sinus rhythm?

A
  • Atrial systole contributes 25% of total SV in normal pts
  • Atrial “kick” contributres 40-50% in AS patients
    • AS associated with diastolic dysfunction 2/2 LVH
    • means impaired cardiac filling
      • due to dec chamber size due to hypertrophy
      • prolong isovolemic relaxation
        • decreases disatolic time and early ventricular filling

** In nonsinus arrythmius, you LOSE the atrial kick**

  • result = dec LV filling - > dec SV -> dec CO -> hypotension
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6
Q

How would you tx an AS who experiences SVT, ventric arrythmia intra-op?

A

1) STABLE OR UNSTABLE SVT

  • Unstable = cardioversion

2) Stable, narrow complex, reg rhythm

  • vagal maneuver
  • adenosine
  • esmolol
  • amio
    • use amio if EF < 40% (CHF)

3) stable narrow complex + wide rhythm or wide complex + normal rhythm

  • esmolol
  • amio - if EF < 40% (CHF) or ventric tachy cannot be ruled out
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7
Q

how would you treat bradyarrhytnmias intraop

A

bradyarrhythmias

  • atropine
  • epi or dopa infusions
  • transcutaenous / transvenous pacing
    • HR 70 - 80
    • allows for adequate diastolic filling
    • provides suficent CO in a heart with a relatively fixed SV
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8
Q

what are your hemodyamic goals for AS patients?

A

Goals: HR, preload, afterload, contractility

1) HR - Normal to slow sinus rythm
* Indicated - return sinus rhythm asap, BB to lower HR
2) Preload - normal to high

  • indicated - IVF
    • SV is fixed as long as preload is maintained (dec cardiac filling)
  • avoid NTG, propofol, thiopental (decrease venous return)

3) Afterload - High

  • indicated - phenylephrine
    • need to maintain CPP (aortic diast pressure)
    • heart not battling afterload, battling outflow obstruction of stenotic valve
  • avoid - SNP

4) contractility - elevated

  • indicated - EPI (watch for HR), Norepi
  • avoid high dose BB, high dose volatile anes
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9
Q

patient all of a sudden becomes hypotensive and has AS, what will you do immedietly?

A

Restore CO ASAP:

  1. Afterload - preserve BP and CPP with phenylephrine
  2. HR - restore sinus rhythm, normal/slow HR
  3. preload - IV fluid to maintain preload
  4. contracility - maintain contractility

phenylephrine

  • alpha agonist, inc afterload, maintain CPP, no reflex tachy, tx of choice
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10
Q

would you premedicate a patient with AS?

A
  • administer carefully under constant monitoring
  • oversedation
    • leads to hypotension, dec CPP
  • undersedation
    • leads to tachy, anxiety, myocardial ischemia
    • (inc o2 consumption, dec disatolic filling time, dec diastolic coronary perfusion)
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11
Q

what monitors would you use in AS patients?

A

1) EKG

  • inc risk of MI
  • monitor signs of ischemia (include II and V5)
  • monitor HR and rhythms (goal is normal to low HR with sinus rhythm)

2) Arterial line

  • pre-induction
  • beat to beat bp monitoring
    • allows for precise and rapid recognition of HD instability

3) PAC

  • not indicated for solely measuring L sided filing pressure
  • advantegous for SVO2, CO, transvenous pacing
  • beneficial possibly in severe LV dysfunction/low EF

4) TEE

  • RV/LV function
  • RWMA
  • volume status/preload
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12
Q

How would you induce this patient?

A

HD GOALS:

  • preload: normal to high
  • HR: normal to low, sinus rhythm
  • afterload: high
  • contracility: normal to elevated

Induction

  • bzd, opioid, lidocaine
  • Etomidate
    • avoid ketamine for inc HR
    • avoid propofol for myocardial depression, SVR reduction
  • Sux vs Roc
    • airway difficulty / pre-op exam of airway
    • no contraindications for sux
    • avoid panc - Inc HR

MAKE SURE DEFIB IS NEARBY

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13
Q

what is your mainteance for AS patients?

A

mainteance

  • no superior method
  • goal - careful titration of meds to maintain HD stability
  • preload - IVF
    • trend CO, trend filling pressure, UOP, pulse pressure variation with A-line
  • afterload - maintain BP with phenylephrine (consider infusion)
  • HR - low to normal, sinus (antiarrythmics meds, defib)
  • contractility - balanced anesthesia - inhaled anesthetic + opioids.
    • Epi or norepi to inc contractlity
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14
Q

what is TAVI?

A

transcatheter aortic valve implantation

  • bovine bioprosthetic aortic valve inserted through a catheter superimposing th eexisting aortic valve and replacing its fucntion
  • retrograde through fem or axillary artery site to aortic valve

Procedure:

  • ballon angioplasty of native aortic valve
    • requires RV pacing at high rate to decrease CO
    • angioplasty assoc with iatrogenic aortic regurg
      • support BP with vasopressors
  • angiogram confirm position of valve
  • RV pacing at high rate reinstituted
    • to decrease CO as valve is rapidly deployed
  • valve deployed and expands
    • causes temporary obstruction to blood
    • stop pacing
    • treat BP with vasopressor
  • patient to ICU
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15
Q

anes considerations for TAVI?

A

1) Monitors

A-line

  • pre-induction
  • procedure associated with HD instability during valvuloplasty and valve expansion
    • valve expansion creates significant obstruction of flow through aorta

TEE

  • evaluate pts baseline disease
  • determine suitability of valve placement
  • monitor heart and valve during procedure
  • evaluate successful placement of new valve

CVC

  • transvenous pacing required during balloon angioplaty and valve deployment
  • vasopressor/inotropes needed during surgery
    • valvuloplasty assoc with iatrogenic Aortic regurg
    • deployment and expansion of new valve temporarily causes obstruction of flow through aorta
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16
Q
A