Aortic stenosis overview
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Aortic Stenosis Microchapters |
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Diagnosis |
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Treatment |
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Percutaneous Aortic Balloon Valvotomy (PABV) or Aortic Valvuloplasty |
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Transcatheter Aortic Valve Replacement (TAVR) |
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Case Studies |
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Aortic stenosis overview On the Web |
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American Roentgen Ray Society Images of Aortic stenosis overview |
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Risk calculators and risk factors for Aortic stenosis overview |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Mohammed A. Sbeih, M.D. [2]; Lakshmi Gopalakrishnan, M.B.B.S. [3] Assistant Editor-In-Chief: Kristin Feeney, B.S. [4]
Overview
The aortic valve assures that blood moves forward the from the left ventricle into the aorta and that it does not leak backward during diastole. When functioning appropriately, the aortic valve does not impede the flow of blood between these two spaces and it does not leak. Under some circumstances, the aortic valve becomes narrower than normal, impeding the flow of blood. This is known as aortic valve stenosis, or aortic stenosis, often abbreviated as AS.
Classification
Aortic stenosis can be classified broadly in two main categories: acquired and congenital. Further classification can be applied based on the origin of the stenosis such as acquired rheumatic, congenital bicuspid, congenital subaortic, congenital subvalvular, and congenital supravalvular.
Pathophysiology
The impedance to antegrade blood flow as a result of aortic stenosis results in chronic pressure overload of the left ventricle. The most common complication of aortic stenosis is left ventricular hypertrophy. The obstruction of flow in aortic stenosis can obviously occur at the level of the aortic valve itself, but can also occur at the subvalvular (below the aortic valve) or supravalvular (above the aortic valve) level as well.
Epidemiology and Demographics
Aortic stenosis is a major health problem primarily affecting older adults and majority is due to calcific degeneration. Aortic stenosis tends to affect approximately 2% of patients over the age of 65, 3% the age of 75, and 4% over the age 85.[1]
Risk Factors
The most common risk factor for the subsequent development of aortic stenosis arises is a congenital bicuspid aortic valve.
Causes
Aortic stenosis can be categorized under two methods of causation: acquired and congenital. Research regarding the influence of preventative therapies on causation is mixed. More research is needed specifically looking at cholesterol lowering interventions and their role on disease onset.
Differential Diagnosis
Aortic stenosis must be differentiated from other cardiac or pulmonary causes of dyspnea, weakness, and dizziness. Furthermore, if there is left ventricular outflow tract obstruction, it is critical to identify if the obstruction is subvalvular, valvular or supravalvular or due to Hypertrophic Cardiomyopathy (HOCM).
Natural History, Complications & Prognosis
Left untreated, aortic valve stenosis can lead to angina, syncope, congestive heart failure, atrial fibrillation, endocarditis, and sudden cardiac death.
Complications
Surgical treatment of aortic stenosis also carries risks and potential complications including vascular complications and mitral valve injury.
Prognosis
30% reduction in gradient is expected as the immediate result of surgical intervention. Patient survival after treatment is higher than that of untreated patients.
Diagnosis
History and Symptoms
The main symptoms of aortic stenosis include angina, syncope and congestive heart failure. Left untreated, the average survival is 5 years after the onset of angina, 3 years after the onset of syncope, and 1 year after the onset of congestive heart failure [2][3][4]. Other symptoms include dyspnea on exertion, orthopnea and paroxysmal nocturnal dyspnea.
Physical Examination
Aortic stenosis is most often diagnosed when it is asymptomatic and can sometimes be detected during routine examination of the heart and circulatory system. The major signs include pulsus parvus et tardus (a slow-rising, small volume carotid pulse), a lag time between apical and carotid impulses, and a distinct systolic ejection murmur.
Electrocardiogram
The electrocardiogram in the patient with moderate to severe aortic stenosis may reveal left ventricular hypertrophy and heart block.
Chest X-ray
Chest x ray may be used as a diagnostic tool in the evaluation of aortic stenosis. Findings associated with aortic stenosis include left ventricular hypertrophy and calcification of the aortic valve.
MRI
Magnetic resonance imaging is rarely used in the diagnosis of aortic stenosis, except in rare cases where the echocardiographic findings are inconclusive. There is a signal void where the high velocity jet exits the aortic valve.
CT
Computed tomography can be helpful as a diagnostic tool in conditions where the echocardiographic findings are inconclusive.
Echocardiography
Echocardiography is the best non-invasive test to evaluate the aortic valve anatomy and function. Echocardiography can be used to estimate the gradient across the aortic valve using the modified Bernoulli equation (gradient = 4 X velocity2). The flow must be constant, so as the velocity increases, the valve area decreases proportionally. Echocardiography can also be used to assess the severity of left ventricular hypertrophy.
Cardiac Catheterization
Left and right heart catheterization as well as angiography may be useful in the assessment of the patient prior to aortic valve replacement surgery.
Aortic Valve Area
The aortic valve area is the size of the orifice for blood to flow from the left ventricle to the aorta. The aortic valve area is reduced in aortic stenosis, and the aortic valve area is the metric that is used to gauge the need for aortic valve replacement surgery. The pressure gradient across a narrowed aortic valve cannot be used to gauge the need for valve replacement as the gradient may be low in patients with impaired left ventricular function.
Aortic Valve Area Calculation
Aortic valve area calculation is an indirect method of determining the area of the aortic valve. The calculated aortic valve orifice area is currently one of the measures for evaluating the severity of aortic stenosis. A valve area of less than 0.8 cm² is considered to be severe aortic stenosis.[5][6]
There are many ways to calculate the valve area of aortic stenosis. The most commonly used methods involve measurements taken during echocardiography. For interpretation of these values, the area is generally divided by the body surface area, to arrive at the patient's optimal aortic valve orifice area.
Treatment
Once a patient becomes symptomatic with aortic stenosis, aortic valve replacement should be performed. Medical therapy reduces symptoms but does not prolong life. If a patient has extensive co-morbidities, transcatheter aortic valve implantation can be considered. Aortic valvuloplasty can be considered in those patients who are too sick for surgery or transcatheter aortic valve implantation.
- Aortic stenosis surgery via aortic valve replacement
- Transcatheter aortic valve implantation
- Percutaneous aortic balloon valvotomy (PABV) or aortic valvuloplasty
Medical Therapy
While medical therapy may improve the symptoms of patients with aortic stenosis, medical therapy does not prolong life expectancy. Aortic valve replacement remains the definitive treatment of symptomatic aortic stenosis and it improves both the symptoms and life expectancy of patients with aortic stenosis. When pharmacological therapies are used, extreme caution must be exercised in the administration of vasodilators as excess vasodilation may lead to hypotension, a reduction in perfusion pressure to the heart, a further decline in cardiac output and further hypotension. This downward spiral can be fatal and must be avoided at all costs.
Percutaneous Aortic Balloon Valvotomy (PABV) or Aortic Valvuloplasty
Although surgical aortic valve replacement is the mainstay of treatment of aortic stenosis as it improves both symptoms and life expectancy, some patients may not be surgical candidates due to comorbidities, and minimally invasive treatment such as percutaneous aortic balloon valvotomy (PABV) maybe an alternative to surgery as a palliative strategy. PABV is a procedure in which 1 or more balloons are placed across a stenotic valve and inflated to decrease the severity of aortic stenosis. This is to be distinguished from transcatheter aortic valve implantation (TAVI) which is a different method that involves replacement of the valve percutaneously.
Transcatheter aortic valve implantation
Untill recently, aortic valve replacement (AVR) was the only effective treatment for severe symptomatic aortic stenosis. However, over the past decade percutaneous treatment of aortic valve disease with implantation of a stent-based valve prosthesis has been introduced as a new treatment in patients considered inoperable because of severe co-morbidities.[7] In Transcatheter Aortic Valve Implantation (TAVI) also known as Percutaneous Aortic Valve Replacement (PAVR), a synthetic valve is advanced to the heart through a small hole made in groin. This procedure is similar in its mechanism to the insertion of a stent, or performing balloon angioplasty albeit with much larger equipment. Traditional aortic valve replacement is an invasive surgical procedure, with considerable mortality and morbidity, especially in more fragile patients. In the newly developed TAVI procedure, the dysfunctional aortic valve is replaced percutaneously, which obviates the need for open heart surgery.
Surgery
Aortic stenosis requires aortic valve replacement if medical management does not successfully control symptoms.
Prevention
Aortic stenosis associated with rheumatic heart disease can be minimized with antibiotic therapy in patients with documented streptococcal pharyngitis (strep throat). Bicuspid aortic valve disease is a congenital variant and cannot be prevented. Calcific degeneration of the valve can potentially be minimized by rosouvistatin and other measures targeting atherosclerosis prevention.
Precautions and Prophylaxis
People with aortic stenosis of any etiology are at risk for the development of infection of their stenosed valve, i.e. infective endocarditis and antibiotic prophylaxis should be considered.
References
- ↑ Stewart BF, Siscovick D, Lind BK, Gardin JM, Gottdiener JS, Smith VE, Kitzman DW, Otto CM (1997). "Clinical factors associated with calcific aortic valve disease. Cardiovascular Health Study". Journal of the American College of Cardiology. 29 (3): 630–4. PMID 9060903. Retrieved 2012-04-11. Unknown parameter
|month=ignored (help) - ↑ Ross J, Braunwald E (1968). "Aortic stenosis". Circulation. 38 (1 Suppl): 61–7. PMID 4894151.
- ↑ Kelly TA, Rothbart RM, Cooper CM, Kaiser DL, Smucker ML, Gibson RS (1988). "Comparison of outcome of asymptomatic to symptomatic patients older than 20 years of age with valvular aortic stenosis". Am J Cardiol. 61 (1): 123–30. PMID 3337000.
- ↑ Iivanainen AM, Lindroos M, Tilvis R, Heikkilä J, Kupari M (1996). "Natural history of aortic valve stenosis of varying severity in the elderly". Am J Cardiol. 78 (1): 97–101. PMID 8712130.
- ↑ Charlson E, Legedza A, Hamel M (2006). "Decision-making and outcomes in severe symptomatic aortic stenosis". J Heart Valve Dis. 15 (3): 312–21. PMID 16784066.
- ↑ "Survival in elderly patients with severe aortic stenosis is dramatically improved by aortic valve replacement: results from a cohort of 277 patients aged >/=80 years". Eur J Cardiothorac Surg. PMID 16950629.
- ↑ Grube E, Laborde JC, Gerckens U, Felderhoff T, Sauren B, Buellesfeld L, Mueller R, Menichelli M, Schmidt T, Zickmann B, Iversen S, Stone GW (2006). "Percutaneous implantation of the CoreValve self-expanding valve prosthesis in high-risk patients with aortic valve disease: the Siegburg first-in-man study". Circulation. 114 (15): 1616–24. doi:10.1161/CIRCULATIONAHA.106.639450. PMID 17015786. Retrieved 2011-03-17. Unknown parameter
|month=ignored (help)