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Diploma in Anaesthesia > Valve lesions and anaesthetics > Flashcards

Valve lesions and anaesthetics Flashcards

1
Q

What percentage of people over 65 have aortic stenosis

A

65%

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2
Q

What is the prevalence and relevance of a congenital bicuspid aortic valve

A

2% prevalence –> earlier development of aortic stenosis

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3
Q

Classify severity of aortic stenosis based on peak gradient and valve area

A

Mild:
<20 mmHg and > 1.5cm^2

Moderate:
20 - 50 mmHg and 0.8 to 1.5 cm^2

Severe:
>50 mmHg and < 0.8 cm^2

Thereafter LVF ensues and the pressure gradient gets less indicating LVF

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4
Q

What is the normal valve area of the aortic valve

A

2.6 to 3.5 cm^2

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5
Q

When do patients present with symptoms in AS

A

When the stenosis is severe –> if the valve is not replaced the life expectancy is 2 to 5 years

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6
Q

What are the symptoms of aortic stenosis

A

Forward - Backward - outward

Forward - Fixed CO state and low LV compliance due to concentric hypertrophy. During exercise CO can not be increased to compensate for peripheral vasodilation –> SYNCOPE

Backward - Concentric hypertrophy leads to increased LVEDP required to maintain cardiac output –> LVEDP is transmitted backwards into the pulmonary circulation –> pulmonary congestion. Development of dyspnoea indicates that the LV is decompensating and starting to dilate –> DYSPNOEA

Outward - LV hypertrophy –> greater muscle mass –> greater O2 demand. Neovascularization is not as fast as hypertrophy and O2 supply is compromised. Calcification and distortion of coronary ostia may also contribute to impaired blood and hence O2 supply –> ANGINA

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7
Q

What is the nature of the murmur auscultated in aortic stenosis

A

Ejection systolic murmur that often radiates to the carotids

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8
Q

Describe the findings related to the apex beat in AS

A

Heaving apex, undisplaced (concentric hypertrophy)

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9
Q

Describe the pulse in AS

A

Slow rising

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10
Q

When should a patient with AS be referred to cardiology

A

Type of surgery
Patient symptomatic
Severity of AS

Consideration by cardiology for cardiac catheterization ± valve replacement

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11
Q

AS vs normal patients - what is the % of ventricular filling done by atrial contraction

A

Normal patients 20% of filling

AS patients 40% of filling

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12
Q

Why should tachycardia be avoided in aortic stenosis

A

Reduces time for diastolic filling time and therefore coronary perfusion time –> worsens ischaemia

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13
Q

Why should bradycardia be avoided in aortic stenosis

A

Stiff LV cannot increase SV to compensate

Increase LV filling time –> longer diastole –> increase ventricular wall tension and reduction of coronary perfusion

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14
Q

What is the effect of reduced SVR in AS

A

Reduced coronary perfusion (fixed output state) coronary perfusion relies on systemic BP

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15
Q

Considering the dramatic effect of propofol on the BP during induction in patients with AS, how should this be treated?

A

Noradrenalin or phenylephrine –> vasopressors is first line to increase SVR without causing tachycardia

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16
Q

Is spinal anaesthesia commonly practice in AS

A

NO. High potential for hypotension and vasodilation caused by rapid onset of SNS blockade

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17
Q

What is a good approach to a patient for emergency surgery with an ejection systolic murmur on initial examination

A

? ECG abnormal with LVH
? Syncope
If yes to both assume severe AS
If no then unlikely that they have significant AS

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18
Q

Describe the pathophysiology of AS

A 
Stenosed valve obstructs blood from LV
Increased LV wall tension
Concentric LV hypertrophy
Poor LV compliance requires higher LVEDP
LV dilatation
19
Q 
During a preoperative assessment of a 75-year-old gentleman for an anterior resection you find an ejection systolic murmur on examination. Which of the following investigations would you like to carry out?
A.	ECG
B.	Exercise tolerance test	
C.	Echocardiography
D.	Chest x-ray	
E.	Cardiac catheterization
A

A. Correct. There may be evidence of LV hypertrophy.

B. Incorrect. AS is a contraindication to performing an exercise tolerance test.

C. Correct. An echo will define the murmur in terms of type of lesion and severity.

D. Correct. A chest x-ray may show the calcified valve, aortic root dilatation, LA enlargement and/or interstitial oedema.

E. Correct. This gives a more accurate indication of the severity of the AS. However this will be requested by a cardiologist not an anaesthetist.

20
Q

Summarize the perioperative management issues associated with AS

A 
Prevent tachycardia 
Prevent bradycardia
Maintain normotension
Maintain preload
Maintain afterload
21
Q

Classify the clinical presentation of mitral regurgitation

A

Acute (rare)

  • Rapid decompensation often requiring surgical intervention
  • MI/Ischaemia or endocarditis

Chronic (more common than acute MR)

  • Rheumatic fever
  • Degenerative disease
  • LV dilatation from any cause (HPT/IHD)
22
Q

Describe the pathophysiology of Mitral Regurgitation

A

Regurgitant mitral valve –> Increase LA volume –> LA dilation + AF –> Pulmonary venous congestion –> Increased PA pressure (Chronic HPV secondary to fluid transudation into alveoli)

23
Q

How is severity of mitral regurgitation assessed

A
  1. Size and volume of the regurgitant jet as it appears on ECHO
  2. Pulsed wave Doppler is used to look for flow reversal in the pulmonary veins - indicates severity
  3. Regurgitant fraction > 0.6
24
Q

What is regurgitant fraction and how is it calculated and interpreted

A

Regurgitant fraction =
Regurgitant SV/Systemic SV

RF < 0.3 mild

RF > 0.6 severe

25
Q

How is the regurgitant fraction reduced?

A

Reducing afterload and increase heart rate

26
Q

What increases the regurgitant fraction

A

Increased afterload

Decreased heart rate

27
Q

What type of valve lesions rely heavily on atrial contraction for adequate LV filling

A

AS and MS

28
Q

Classify the causes of aortic regurgitation

A

Acute

  • IE
  • Ascending aortic aneurysm
  • Trauma

Chronic

  • Rheumatic heart disease
  • Bicuspid aortic valve
  • Marfans
29
Q

How is the severity of aortic regurgitation classified

A

Regurgitant fraction = Regurgitant volume/Aortic valve systolic flow
Mild: < 0.3
Mod: 0.3 - 0.6
Severe: > 0.6

Regurgitant volume = Aortic valve systolic flow - Cardiac Output
Mild: < 3L/min
Mod: 3 - 6 L/min
Severe: > 6 L/min

30
Q

What worsens severity of AR

A

INCREASING AORTIC DIASTOLIC PRESSURE AND DIASTOLIC TIME

Rx (Reduce afterload + Increase HR)

31
Q

What are the examination findings in Aortic Regurgitation

A

Collapsing pulse
Corrigan’s sign (sudden distension and then collapse of the caortid arteries)
Displaced hyperdynamic apex beat
Early diastolic murmur
Inspiratory crepitations
Austin flint murmur (function MS caused by regurgital jet impeding flow through the mitral valve leaflets)

32
Q

What are the main aims when anaesthetising patients with regurgitant lesions are:

Mild tachycardia

A
  1. Mild tachycardia (reduce diastolic time available for regurg to occur)
  2. Reduce afterload (reduces regurgitant fraction)
    - balance between adequate coronary perfusion pressure and good cardiac output
  3. Maintain normal preload
  4. Endocarditis prophylaxis
33
Q

Classify the causes of Mitral stenosis

A

Common
- Rheumatic fever

Uncommon

  • RA
  • SLE
  • Amyloid

It is four times more common in woman than in men

34
Q

How is the severity of MS determined

A

Valve area and/or diastolic transmitral pressure gradient

VALVE AREA (Normal: 4 - 6 cm^2)

  • Clinically significant: 1 - 2 cm^2
  • Critical MS: < 1 cm^2

DIASTOLIC TRANSMITRAL PRESSURE GRADIENT

  • Mild: < 5 mmHg
  • Moderate: 5 - 12 mmHg
  • Severe: > 12 mmHg
35
Q

What are the aims when anaesthetising a patient with mitral stenosis?

A 
Avoid tachycardia (reduces time available for ventricular filling and impairs CO/causes pulm oedema)
Maintain sinus rhythm
Maintain afterload (causes tachycardia if SVR reduced)
Maintain preload
Endocarditis prophylaxis
36
Q

Describe the murmur in MS

A

Mid-diastolic

37
Q

What causes Triscuspid stenosis

A

Rheumatic fiver - usually associated with Mitral valve disease

38
Q

What are the effects of tricuspid stenosis

A

Reduced CO
High RAP
Same aims as in MS

39
Q

What causes TR

A

Rheumatic fever

Associated with MV disease

40
Q

What causes pulmonary valve lesions

A

RARE
Congenital
10% associated with ASD
Same aims as for AS

41
Q

Define pulmonary hypertension

A

Systolic PA pressure > 30 mmHg or mean PA pressure > 20 mmHg

42
Q

Classify the causes of pulmonary hypertension

A

Primary
- idiopathic

Secondary

  • MR, MS
  • Congenital cardiac defects
  • Pulmonary embolism
  • Chronic hypoxic lung diseases
  • Connective tissue diseases
43
Q

Compare the anaesthetic aims between regurgitant and stenotic lesions

A

Regurgitant

  • Aim for mild tachycardia
  • Avoid bradycardia
  • Reduce afterload

Stenotic

  • Avoid tachycardia
  • Avoid severe bradycardia
  • Maintain afterload
  • Maintain sinus rhythm

The anaesthetic aim for patients with valvular lesions is to encourage forward flow of blood through the heart to maintain cardiac output. In patients with stenotic lesions this means allowing sufficient time for blood to pass through the valve. For patients with regurgitant lesions, it means reducing the time available for blood to flow back through the valve.

Diploma in Anaesthesia (73 decks)

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