Aortic Stenosis

 

• Causes and epidemiology

  Commonest valve disease, affecting 4% of elderly.

  Causes:

  • Calcification
  • Congenital: bicuspid valve
  • Rheumatic valve disease

• Signs and symptoms

  Classic triad of symptoms, SAD:

  • Syncope, which may occur on exertion.
  • Angina
  • Dyspnoea on exertion.

  Signs:

  • Ejection systolic murmur: best heard in aortic and left sternal area, radiating to carotids.
  • Quiet A2 and later (but rarely) reversed splitting (A2 before P2 during expiration).
  • Slow rising pulse: delayed and slow through stiff valve.
  • Narrow pulse pressure: reduced gap between systole/diastole due to ↓ejection volume.
  • Non-displaced but sustained/heaving apex, lasting >50% of systole.
  • Aortic thrill.

• DDx: Systolic murmur

  • Aortic stenosis: loud on expiration.
  • Pulmonary stenosis: pulmonary area, loud on inspiration.
  • Pan-systolic: mitral regurgitation, tricuspid regurgitation, VSD.
  • Late systolic: mitral vale prolapse.
  • HCM: increases on standing.
  • Aortic sclerosis. Distinguished from aortic stenosis by lack of other signs/symptoms.

• Investigations

  Initial tests:

  • Echo with doppler: confirms diagnosis and assesses degree of calcification, LV function, aortic velocity, pressure gradient, and valve area. These factors help classify severity.
  • ECG: LVH, P-mitrale, LBBB, AV block, poor R wave progression.
  • CXR is usually normal, otherwise: LVH, calcified valve, dilated ascending aorta.

  Further:

  • Cardiac MRI, stress testing, angiography, or catheterisation, if indicated.
  • Multi-slice CT can help evaluate severity, and is useful when considering TAVI.
  • BNP may provide prognostic information.

• Management

  Medical

  • Modify cardiovascular risk factors, as AS is itself a risk factor.
  • Treat any secondary heart failure.
  • 6-monthly echo if severe.

  Surgical

  Indications:

  • {Severe (<1 cm2 opening)} + {symptoms or LVSD}.
  • If severe but asymptomatic, need to weigh risks vs. benefits. If undergoing CABG, might as well be done.

  Surgical aortic valve replacement (SAVR):

  • Historically the treatment of choice in those well enough.
  • Risks: periprocedural stroke, major bleeding.
  • Mechanical valves require long-term anticoagulation, while bioprostheses only need 3 months aspirin.
  • Mechanical valves are more suitable for younger patients, as they are more durable.

  Transcatheter aortic valve implantation (TAVI):

  • Initially only for higher risk patients unfit for SAVR, but increasingly used even in low risk individuals.
  • Procedure: entry can be transluminal, through the femoral (common) or subclavian artery, or transapical, which involves a minithoracotomy through the left ventricle. Balloon dilates the prosthetic valve, pushing the existing valve out of the way. Though sometimes called 'replacement' (TAVR), the old valve is not removed. Can be under local or general anaesthetic.
  • Risks vs. SAVR: similar mortality, more aortic regurgitation, less periprocedural stroke, less major bleeding.
  • Post-op antiplatelets: lifelong aspirin plus 3-6 months clopidogrel.

  Outcome:

  • Both improve functional status and roughly halve mortality vs. medical treatment.

  Balloon valvuloplasty:

  • Can provide temporary relief (6-12 months).
  • Only really used as a bridge to TAVI in unstable patients.

• Complications and prognosis

  Complications:

  • LVF or CHF.
  • Aortic root dilatation due to haemodynamic changes around valve.
  • Infective endocarditis.
  • Sudden cardiac death.

  Prognosis:

  • Asymptomatic: 1 year mortality 1%.
  • Symptomatic: 1 year mortality 25%, or 50% if 'high-risk' (i.e. unsuitable for SAVR).
  • Poor prognostic factors: age, IHD, ↑BNP