Case 4 - Aortic Stenosis Flashcards
What are the classic symptoms of AS and why do they occur?
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
what is the pathophys behind AS and LV function?
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)
-
cannot maintain forward flow, heart dilates
etiology of AS
contenital bicuspid valve
senile calification of trileaflet aortic valve
rhemuatic AS
what is normal AVA, what is considered severe AS?
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
why is it important to maintain sinus rhythm?
- 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
How would you tx an AS who experiences SVT, ventric arrythmia intra-op?
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
how would you treat bradyarrhytnmias intraop
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
what are your hemodyamic goals for AS patients?
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
patient all of a sudden becomes hypotensive and has AS, what will you do immedietly?
Restore CO ASAP:
- Afterload - preserve BP and CPP with phenylephrine
- HR - restore sinus rhythm, normal/slow HR
- preload - IV fluid to maintain preload
- contracility - maintain contractility
phenylephrine
- alpha agonist, inc afterload, maintain CPP, no reflex tachy, tx of choice
would you premedicate a patient with AS?
- 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)
what monitors would you use in AS patients?
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
How would you induce this patient?
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
what is your mainteance for AS patients?
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
what is TAVI?
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
anes considerations for TAVI?
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
