Case 5 - Mitral Stenosis

Question 1

What is the pathophysiology of mitral stenosis?

Answer 1

valve area

• normal = 4 - 6 cm2
• MS occurs at < 2 cm 2
• critical MS at < 1 cm2

pathophysiology (in order)

• Mitral stenosis
• gradient between LA and LV increases
  
  • to maintain adequate flow and filling of LV
• LA dilates and pressure rises
• inc LA pressure transmitted backward to pulm circulation
• Pulmonary venous congestion - > Pulm Edema
• increase PVR -> pulm HTN

Question 2

is it possible to get LV failure in MS?

Answer 2

• believed that LV is “protected” form pressure or volume overload since less blood is entering cavity 2/2 obstructive MS
• Pulm HTN -> RVH -> RV pressure overload –> bowing of intraventricular septum into LV cavity -> LV diastolic dysfunction

Question 3

what are the hemodynamic goals for patients with MS?

Answer 3

Goals:

1) HR - Slow

• flow from LA to LV via mitral valve occurs during diastole
• slow HR allows for diastolic filling time
• tachy = diminished filling time -> impairs LA emptying - > inc backflow of blood into pulm -> decompensation
• Indicated - BB, digoxin, CCB
• avoid - dopa, dobuta, ketam, panc

2) Preload - High

• high LA pressure required to maintain filling of LV (preload).
• high gradient between LV and LA = forward flow
• indicated - IVF
• avoid - NTG, thiopenta, propofol

3) Afterload - High

• maintain CPP in face of relatively low and fixed CO
• indicate - phenylephrine
• avoid - Ace-I (except in RV failure)

4) contractility - normal to increased

• helps preserve SV
• indicate - Norepi
• avoid - high dose volatile, high dose BB

Question 4

It is possible that MS patients can have RV failure as well. Is this going to change your hemodynamic goals?

Answer 4

Goals for MS + RVF:

1) HR -

• MS alone - Slow - diastolic filling of LA to LV
• MS + RVF - normal to mild elevation
  
  • CO in RV becomes rate-dependent

2) preload

• MS alone - High -> inc LA pressure to maintain high gradient between LA and LV = forward flow
• MS + RVF - consider normal
  
  • high preload can be associated with exacerbastion of pulm congestion

3) Afterload - high

4) contractility - normal to increased

Question 5

how would you optimize an MS condition pre-operatively?

Answer 5

Goals -

• HR control
• promote LV filling
• reduce pulm congestion

1) HR control - Slow

• helps promote ventricular filling (inc diastolic time)
• BB, CCB
• digoxin for Left or RV dysfunction
  
  • digoxin inc contractile force of cardiac muscle due to cardiac glycoside effect

2) pulm congestion

• salt restriction, diuretics
• if taking diuretics, check electrolytes (avoid dig toxicity 2/2 diuretic induced hypokalemia)

3) A-fib 2/2 LA dilation

• patient on anticoagulation?
• patient rate controlled?

Question 6

What monitors would you place on this patient with MS?

Answer 6

1) ASA standard monitors
2) pre-induction arterial line

• follow BP closely during induction
• tachy during intubation or hypotension due to induction = catastrophic

3) PAC

• LA filling pressure, Pulmonary Artery pressure
• CO
• SVo2
• SVR, PVR calculations
• in presence of RV dysfunction, monitoring pulm art presure allows to follow trend when treating to decrease RV afterload

4) TEE

• biventricular function
• LA dimensions
• valve function
• preload

Question 7

How would you induce a patient with MS?

Answer 7

HD goals:

• HR - slow
• preload - high
• afterload - high
• contractility - normal to increased

Induction

Goal: Avoid Tachy, hypotension, dec preload, dec aferload, dec contracility

• bzd - amnesia, lower dose of induction meds
• opioid - blunt symp stim (tachy) from laryngoscopy
  
  • also increases vagal tone to slow HR
• lido - blunt airway reflexes (symp stim with coughing)
• etomidate - cardiovascular stable drug
  
  • avoid propfol - venodilation, myocardial depressant, dec SVR
  • avoid ketamine - tachy
• Sux vs Roc
  
  • do not give panc - casues tachy

Question 8

what is your anes mainteance for MS patients?

Answer 8

HD goals:

• HR - slow
• preload - high
• afterload - high
• contractility - normal to increased

Mainteance

Goal: Avoid Tachy, hypotension, dec preload, dec aferload, dec contracility

• balanced anesthesia
  
  • low volatile anesthetic conc 1 MAC or less
    
    • high dose assoc with myocardial depress
  • opioid for pain and reduce volatile anes conc
  • muscle relaxants as needed

Question 9

MS patient becomes hypotensive intra-op, what will you to tx the patient? Would you consier epi or dobutamine?

Answer 9

Hypotension

• Phenylephrine or Vasopressin
  
  • preserves vtal organ perfusion in face of fixed low cardiac output
  • maintain CPP
  • increase BP with dec HR 2/2 baroreceptor reflex
  • vasopressin - better option in pts with pulm HTN (does not caues pulm vasoconstrict)

B adrenergic agnoists

• not preferred medications (epi if there is a code only)
• cause tachycardia and vasodilation = undesirable

Question 10

patient with MS undergoes mitral valve replacement. You are trying to wean off caridopulm bypass, but this is complicated by pulm HTN and RV failure. how will you treat this?

Answer 10

Goals:

• reduce RV afterload
• optimize RV preload
• maintain RV coronary perfusion
• support RV contractility

1) avoid increases in PVR:

• hypoexmia, hypercabia, hypothermia, symp stimulation, acidosis

2) Tx with pulmonary vasodilators:

• inhaled NO
• milrinone
  
  • inodilator; PDE III inhibitor
  • can cause systemic hypotension
• prostaglandin E1
  
  • can cause systemic hypo
• inhaled prostacyclin (iloprost)

3) tx hypotension

• EPI
  
  • preferred for pts with pulm HTN + RV failure (2/2 dec RV contractility)
• vaso or NE - for systemic hypotension