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Introduction & Definition

What is …?

Epidemiology, Clinical Course & Prognosis

How common is …?

  • ..

Aetiology & Risk Factors

What are the causes of …?

Pathophysiology

What are the underlying pathophysiological mechanisms in …?

Presentation

What are the symptoms & signs of …?

Complications

What are the complications of …?

Work-Up Summary

How do you work-up the patient with aortic stenosis?

To Determine Diagnosis
  • Focused history and clinical examination
  • Transthoracic echocardiography
To Determine Severity / Prognosis
  • Transthoracic echocardiography
  • Additional tests depending upon clinical features
    • Exercise testing (in asymptomatic patients)
    • CT calcium scoring
    • Exercise stress echo
    • Dobutamine stress echo
    • Cardiac catheterization and determination of transvalvular gradient (also give information about any concurrent coronary artery disease)
To Assess for Complications
  • ECG: LVH, LV strain
  • CXR: cardiomegaly, signs of LV failure
  • FBC: haemolytic anaemia

Clinical Investigations

Imaging Investigations

Management Summary

How do you work-up the patient with aortic stenosis?

To Determine Diagnosis
  • Focused history and clinical examination
  • Transthoracic echocardiography
To Determine Severity / Prognosis
  • Transthoracic echocardiography
  • Additional tests depending upon clinical features
    • Exercise testing (in asymptomatic patients)
    • CT calcium scoring
    • Exercise stress echo
    • Dobutamine stress echo
    • Cardiac catheterization and determination of transvalvular gradient (also give information about any concurrent coronary artery disease)
To Assess for Complications
  • ECG: LVH, LV strain
  • CXR: cardiomegaly, signs of LV failure
  • FBC: haemolytic anaemia

Supportive Management

Specific Management

How can … be treated?

Anaesthetic Management Summary

Risks
  • Significant risk of MI and death
    • Compensatory mechanisms for fixed output state disrupted by anaesthesia
    • Anaesthesia induces a reduction in SVR
    • Fixed obstruction in AS impedes compensatory increase in cardiac output
    • Resulting hypotension can lead to reduced myocardial perfusion and ischaemia
    • Induces a downward spiral of reduced contractility, further hypotension and ischaemia
  • Risk of arrhythmias
    • General anaesthesia can reduce sinus node automaticity
    • Can lead to nodal rhythms or other arrhythmias (AF or atrial tachycardias)
  • Risk of infective endocarditis
Preload:
  • LV hypertrophied and compliance is poor
  • Optimize preload to enable adequate filling of the LV (guided by cardiac output monitoring)
  • Vasodilators (particularly venodilators such as GTN) should be avoided
 
Rate:
  • Avoid tachycardia (Aim 50-70)
    • Reduces diastolic filling time
    • Reduces the time for coronary perfusion, therefore worsening ischaemia
    • Increases oxygen demand
  • Avoid excessive bradycardia
    • This results in a reduced cardiac output as the stiff ventricle cannot increase the stroke volume to compensate.
    • The increase in ventricular filling due to longer diastole also increases ventricular wall tension further reducing coronary perfusion.
 
Rhythm: Sinus
  • Maintain sinus rhythm – vital
    • Atrial contraction is important for LV filling
    • Up to 40 % of filling in diastole is due to atrial contraction (normally only 15–20 %)
    • AF and nodal rhythms are therefore poorly tolerated in these patients
  • Arrhythmias need aggressive treatment
 
Contractility: Maintain
  • Maintain myocardial contractility:
    • Avoid B-blockers or myocardial ischaemia
  • Increasing myocardial drive does not improve cardiac output and can precipitate ischaemia through increased oxygen consumption
 
Afterload:
  • Avoiding hypotension is critical – maintain a high-normal diastolic
    • Diastolic pressure must be maintained ensure filling of coronary arteries – require larger than usual due to hypertrophied LV
    • Any hypotension needs to be treated early to avoid spiral of further reductions in coronary perfusion, causing myocardial depression and potentially leading to cardiac arrest
    • CPR is generally ineffective in these patients unless internal massage can be performed
  • Afterload essentially fixed below a certain limit due to valvular obstruction:
    • Reducing SVR has no impact on ejection of blood from the LV, as the obstruction to flow is due to the stenosed valve leading to a fixed cardiac output
History & Examination
  • Full anaesthetic history
  • Specific areas of focus:
    • Associated symptoms
    • Last echo and it’s findings
    • Cardiology interventions and follow-up
  • Examination of cardiovascular and respiratory system

 

Investigations
  • Echo – strongly desirable, consider delaying non-essential surgery until performed:
    • Severity of stenosis
    • LV function
  • Bloods:
    • FBC to exclude anaemia
    • Coagulation studies – particularly if on warfarin
    • U&E and renal function – may be disturbed if on diuretics
    • BNP
  • ECG:
    • LVH / LV strain
    • Arrhythmias
  • Chest Xray

 

Risk Assessment & Optimisation
  • Referral to cardiologist – assistance with decisions regarding:
    • Appropriateness of surgery
    • Need for pre-operative intervention:
      • Aortic valve replacement
      • TAVI
      • Balloon valvuloplasty
  • Lee index or ‘revised cardiac risk’ index tool
    • Use information to consent appropriately with risks involved

 

Premedication
  • Consider using anxiolytics to prevent tachycardia
Choice
  • Spinal anaesthesia is traditionally avoided:
    • Potential for hypotension and vasodilation caused by the rapid onset of sympathetic blockade
    • Decreased preload and decrease in cardiac output
    • Decrease in afterload and coronary filling
  • Cases of carefully titrated anaesthesia using spinal or epidural catheter reported
  • Limb blocks may be beneficial, either alone or as an adjunct to general anaesthesia.
 
Induction & Maintenance
  • Extreme care needs to be taken with induction of anaesthesia to avoid hypotension:
    • Titrate all anaesthetic drugs very carefully
    • Options include high dose opioids and etomidate or inhalational induction
  • Use vasopressors to maintain pre-induction blood pressure-levels:
    • Ensure vasopressor drugs (phenylephrine or metaraminol) at hand
    • Infusions running peripheral vasopressor during induction facilitate maintenance of pressure
Monitoring & Acess
  • Arterial cannula for invasive blood pressure monitoring:
    • Should be routine except for short procedures
    • Consider prior to induction
  • Central venous line may be useful for vasopressor therapy
  • PA catheters relatively contraindicated due to risk of arrhythmias 
 
Conduct
  • See ‘Haemodynamic goals’
  • Consider use of endocarditis prophylaxis:
    • Antibiotic prophylaxis not routinely advised (NICE Guidance)
    • Should be considered in high risk individuals
  • Monitor plasma potassium regularly given risk of arrhythmias

     

    Analgesia

    • Avoid NASIDs – high risk renal dysfunction
    • Ensure optimum analgesia to avoid tachycardia
      Location & Review
      • HDU / ICU for ongoing BP monitoring:
        • NCEPOD recommends admission for valve area <1cm2
        • Should be strongly considered if reduced systolic function
       
      Monitoring & Investigations
      • Monitor for renal dysfunction
       
      Analgesia
      • Avoid NSAIDS – high risk of renal dysfunction
      • Ensure optimum analgesia to avoid tachycardia
      • Regional anaesthesia may be beneficial
       
      Supportive Care
      • Continue haemodynamic aims
      • May require vasopressor infusions and ongoing invasive arterial BP monitoring to maintain haemodynamic stability
      • Ensure meticulous attention to appropriate intravascular filling

      Preoperative Management

      Intraoperative Management

      Postoperative Management

      Author

      The Guidewire
      Trainee in ICM & Anaesthesia

      Reviewer

      The Guidewire
      Trainee in ICM & Anaesthesia