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Aortic Stenosis

Aortic stenosis is a narrowing of the normal tricuspid aortic valve or a congenital bicuspid valve which leads to restricted blood flow and eventually compromised heart function.

 

AVS is the most common valvular heart disease in the developed world Common condition which increases with age- an important public health problem A study in Norway has shown prevalence of AVS
- 0.2 % in the 50-59 age gr
- 1.3 % in the 60-69 age gr
- 3.9 % in 70-79 age gr and 9.8 % in the 80-89 % Studies in US have shown an increase in hospitalization of patients over 65 for aortic valve surgery Experience has shown that AVS is progressive and after the onset of symptoms untreated patients have a poor prognosis ( once symptoms start average survival is 50 % at 2 yrs and 20 % at 5 yrs ) Overall prevalence is estimate to be between 3 % and 23 % A meta-analysis and modeling study by Rubel LJ et al has show that the pooled prevalence of all AVS in the elderly was 12.4 % and the prevalence of severe AVS was 3.4 % Every year about 67,500 surgical aortic valve replacements ( SAVR ) are done in the US Morbidity and mortality from AVS is expected to increase with an aging population The Euro-Heart survey revealed that the patients with valve disease were older , more likely females and with co-morbidities like diabetes , CKD , more likely to have had a prior CHF and LVF dysfunction , cardiac ischaemic event or revascularization.

 

Types degenerative calcific , rheumatic , congenital ( bicuspid , unicuspid )

 

Other rare causes include familial hypercholesterolaemia hyperuricemia hyperparathyroidism Paget’s disease Fabry disease Lupus erythematosus Drug- induced.

 

What happens – Degenerative AVS is no longer regarded as a passive wear and tear phenomena It is considered an active multistage process in which several factors play a role as
- inflammatory tissue milieu
- atherosclerotic like lesions
- lipoprotein deposition
-renin angiotensin system activation
- osteoblastic transformations –> valve mineralisation
- calcification process.

 

Progressive chronic disease- Mild fibrocalcific leaflet changes- More severe calcification leaflet thickening , stiffening- Significant obstruction to ejection of left ventricle

 

Epidemiological studies have shown an association between conventional CV risk factors as hypertension , diabetes and dyslipidemia , smoking , male gender and aortic sclerosis or stenosis Literature quotes that AVS and atherosclerosis share similar risk factors with initiating factors and mechanisms of progression that are broadly similar to those of atherosclerosis in coronary other arteries AVS patients often suffer with coronary artery disease

 

Presentation – Reduced valve orifice causes 
an impairment of left 
ventricular emptying- Aortic valve is subjected to a high pressure gradient during ejection leading to a rise in peak systolic pressure within the ventricles- increased afterload
( ventricular wall stress ) decreased stroke volume increased end systolic volume increased end diastolic volume – Ventricles try to overcome this
 by increasing the force of contraction. Compensatory mechanisms happen as
 left ventricular hypertrophy- causes a large increase in end diastolic pressure Myocardial ischaemia cardiac and systemic responses as systemic vasoconstriction ,increased blood flow volume , incd HR and inotropy – In moderate and severe stenosis the compensatory mechanisms would be overwhelmed -> the stroke volume falls and this can lead to a reduction in arterial pressure ( LV dysfunction and failure )Inability to maintain cardiac output.

 

Often an incidental finding
 systolic murmur during a clinical examination echocardiogram for some other reason.

 

Symptoms typically insidious in onset with first complains often of decreased exercise tolerance or dyspnoea on exertion age of presentation may vary.

 

Once symptoms develop the life expectancy is shortened to about 3 yrs unless the reduced left ventricular outflow is not corrected by aortic valve replacement. This is the most important point to learn about aortic stenosis – as demonstrated by this famous curve from Ross and Braunwald in 1968. This shows that the patients with AVS have a long symptomatic latent period but once symptoms develop the survival decreases rapidly. Symptoms may often be attributed to other illnesses or misinterpreted.

 

Auscultation and examination delayed or diminished carotid upstroke a systolic ejection murmur – heard loudest at the right upper sternal border which radiates to the carotids single S2 BP would be normal ( unless HTN or aortic regurgitation ) weak and small amplitude pulse Reduced pulse pressure ( advanced AVS ) Severe aortic stenosis angina syncope dyspnoea heart failure systolic/ diastolic dysfunction. Non cardiac presentation includes gastrointestinal bleeding and cerebral emboli.

 

Echo with Doppler- allows assessment of valve anatomy , leaflet motion , AV area , ventricular dimensions and function Doppler allows estimation of velocity and pressure gradients across valve area AVS is classified into 3 categories based on echo by AHA.

 

ECG- advanced AVS almost 80 % of patients will have LV hypertrophy with or without repolarization abnormalities left atrial enlargement left axis deviation LBBB AF – in late stages and may indicate co-existing mitral valve disease or CAD.

 

CXR- aortic valve calcification may be seen in severe disease patients with bicuspid aortic valve may reveal dilatation of the ascending aorta.

 

Currently there is no medical therapy which can halt the disease progression. Treatment of aortic stenosis is Aortic valve replacement – it is effective. Conventional aortic valve replacement- SAVR. Transcatheter aortic valve replacement- TAVI

 

Currently the guidelines recommend AVR for patients with severe aortic stenosis and symptoms of LV dysfunction For patients who have asymptomatic severe AS and moderate AS with LV dysfunction -it is still not clear if they benefit with AVR TAVI has seen significant growth in recent years

Complications – high risk of sudden death heart failure pulmonary hypertension increased risk of infective endocarditis (particularly patients with bicuspid valve) increased risk of GI bleeding embolic disease

Patient information resource

American Heart Association on aortic stenosis https://www.heart.org/en/health-topics/heart-valve-problems-and-disease/heart-valve-problems-and-causes/problem-aortic-valve-stenosis

British Cardiac Patients Association – a good summary on management http://bcpa.uk/factsheets/AorticStenosis.htm

American College of Cardiology – Cardiosmart on aortic stenosis https://www.cardiosmart.org/topics/aortic-stenosis/overview

References

  1. Pujari SH, Agasthi P. Aortic Stenosis. [Updated 2020 Aug 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557628/
  2. Guillaume Marquis-Gravel, MD, MSc, Björn Redfors, MD, PhD, Martin B. Leon, MD, and Philippe Généreux, MD
  3. Aortic stenosis – pathogenesis, prediction of progression, and percutaneous intervention D Natarajan , B Prendergast J r Coll Physicians edinb 2017; 47: 172–5 | doi: 10.4997/JrCPe.2017.217 https://www.rcpe.ac.uk/sites/default/files/jrcpe_47_2_prendergast.pdf
  4. Aortic Stenosis: Guidelines and Evidence Gaps Author links open overlay panelAndrew W.HarrisMDaPhilippePibarotDVM, PhDbCatherine M.OttoMD ( Summary ) https://doi.org/10.1016/j.ccl.2019.09.003

  5. Cardiovascular Physiology Concepts Richard E Klabunde PhD Aortic Stenosis https://www.cvphysiology.com/Heart%20Disease/HD009b
  6. Nalini M. Rajamannan, Update on the pathophysiology of aortic stenosis, European Heart Journal Supplements, Volume 10, Issue suppl_E, 1 July 2008, Pages E4–E10, https://doi.org/10.1093/eurheartj/sun013
  7. BMJ Best Practice Aortic Stenosis Summary https://bestpractice.bmj.com/topics/en-gb/325
  8. Zakkar MBryan A JAngelini G DAortic stenosis: diagnosis and management 
  9. Aortic Stenosis: Pathophysiology, Diagnosis, and Therapy The American Journal of Medicine Volume 130, Issue 3, March 2017, Pages 253-263 ( Abstract )

  10. Balloon valvuloplasty for aortic valve stenosis in adults and children Interventional procedures guidance [IPG78]Published date: 

  11. Aortic Stenosis A brief summary of prevalence, guidelines, new treatment options,
    and current data https://edwardsprod.blob.core.windows.net/media/Gb/therapies/aortic-stenosis/as_brochure_eu.pdf
  12. Risk factors for aortic stenosis Vol. 18, N° 11 – 19 Feb 2020 Prof Magnus Back FESC et al https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-18/risk-factors-for-aortic-stenosis
  13. Ortlepp JRSchmitz FBozoglu T, et al
    Cardiovascular risk factors in patients with aortic stenosis predict prevalence of coronary artery disease but not of aortic stenosis: an angiographic pair matched case–control study
  14. Aortic Stenosis in the Elderly Disease Prevalence and Number of Candidates
    for Transcatheter Aortic Valve Replacement: A Meta-Analysis and Modeling Study Ruben L. J. Osnabrugge et al Journal of the American College of Cardiology Vol. 62, No. 11, 2013
    2013 by the American College of Cardiology Foundation ISSN 0735-1097/$36.00
  15. Eveborn GWSchirmer HHeggelund G, et al
    The evolving epidemiology of valvular aortic stenosis. The Tromsø Study
  16. Aortic Stenosis Helmut Baumgartner and Thomas Walther
    ESC CardioMed (3 edn)

    Edited by A. John Camm, Thomas F. Lüscher, Gerald Maurer, and Patrick W. Serruys

  17. Alec Vahanian, Catherine M. Otto, Risk stratification of patients with aortic stenosis, European Heart Journal, Volume 31, Issue 4, February 2010, Pages 416–423, https://doi.org/10.1093/eurheartj/ehp575
  18. Robert O. Bonow, MD, MS and Philip Greenland, MD

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