Aortic stenosis by epifani d. Armedilla



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AORTIC STENOSIS

  • BY

  • EPIFANI D. ARMEDILLA


OBJECTIVES

  • Review the anatomy and physiology of the cardiovascular system

  • Describe the pathophysiology of aortic stenosis

  • Identify the causes of aortic stenosis

  • Recognize the signs and symptoms of aortic stenosis

  • Discuss the imaging studies used in detecting the severity of aortic stenosis

  • Review the treatment for aortic stenosis



The Cardiovascular System



AORTIC STENOSIS



AORTIC STENOSIS



Causes of Aortic Stenosis

  • Congenital

  • Rheumatic fever

  • Degenerative calcification of the aortic cusps – most common

  • Obstructive infective vegetations

  • Paget’s disease of the bone

  • Systemic lupus erythematous

  • Rheumatoid disease

  • Irradiation



Congenital AS



Calcified AS



Senile or degenerative AS



Aortic Stenosis



Clinical Findings in Aortic Stenosis

  • Typical murmur and thrill for slightly narrowed, thickened, or roughened valves

  • Systolic ejection murmur at the aortic area transmitted to the neck and apex for mild or moderate cases

  • Palpable left ventricular heave or thrill, a weak to absent aortic second sound, or reversed splitting of the second sound are present in severe cases of AS because of prolonged ejection time

  • S4 is common and reflects increased atrial contribution to ventricular filling



Symptoms of Aortic Stenosis

  • AS is asymptomatic until the valve orifice has narrowed to approximately 0.5 cm²/m² body surface area of adults

  • Patients remain asymptomatic for a long period of time

  • The condition is first diagnosed based on detection of a systolic murmur on auscultation that can be explained by the gradual process of obstruction



Three Cardinal Symptoms of AS

  • Exertional dyspnea

  • Exertional angina

  • Exertional syncope



Exertional Dyspnea

  • Is a result of elevation of the pulmonary capillary pressure secondary to reduced compliance and/or LV dilatation



Exertional Angina

  • Usually develops later and reflects an imbalance between the augmented myocardial oxygen requirements and reduced oxygen availability



Exertional Syncope

  • Caused by arrhythmias (usually ventricular tachycardia and bradycardias), hypotension, or decreased cerebral perfusion resulting from increased blood flow to exercising muscles without compensatory increase in cardiac output



Imaging Studies

  • ECG

  • Chest radiography

  • Echocardiography

  • Dobutamine echocardiography

  • Cardiac catheterization



ECG

  • LV hypertrophy – classic finding

  • Other nonspecific changes are left atrial enlargement, left axis deviation, and left bundle-branch block

  • Not a reliable test because of the wide variations seen in AS and other cardiac conditions



ECG – LV Hypertrophy

  • Large S wave in V1

  • Large R wave in V5



Chest Radiograph

  • Normal or enlarged cardiac silhouette

  • Calcification of aortic valve

  • Dilatation and calcification of ascending aorta



Echocardiography

  • Useful in assessing the severity of AS, the degree of coexisting aortic regurgitation, LV size and function

  • Helpful in estimating pulmonary systolic pressure and in identifying other cardiac abnormalities

  • TEE – displays the obstructive orifice extremely well



Dobutamine Echocardiography

  • Indicated in patients with moderate aortic stenosis and LV dysfunction to predict the reversibility of LV dysfunction after AVR

  • Pts. With AS, LV dysfunction, and relatively low gradients have better outcome when management decisions are based on the results of dobutamine echocardiogram (Schwammenthal, et al, 2001)



Cardiac Catheterization

  • Indicated for hemodynamic evaluation whenever there is discrepancy between the clinical picture and echocardiography

  • Indicated for young, asymptomatic patients with noncalcific congenital AS, to define the severity of obstruction to LV outflow

  • Indicated for patients in whom it is suspected that the obstruction to LV outflow may not be at the aortic valve but rather in the sub or supra-valvular regions

  • Also indicated to evaluate the coronaries in AS patients at risk for coronary artery disease



Grading of Aortic Stenosis

  • The aortic valve area must be reduced to one-fourth of its normal size before significant changes in the circulation occur

  • AS is graded based on the aortic valve area

    • Mild - >1.5 cm²
    • Moderate – 1.1 to 1.5 cm²
    • Severe - <0.75 to 1 cm²


Management of Aortic Stenosis



Pharmacological Management

  • Medical treatment has no role in preventing the progression of the disease process

  • But with the onset of LV systolic dysfunction, the use of inotropic agent may be advocated



Surgical Management

  • AVR is indicated for symptomatic patients

  • AVR improves survival in patients with depressed as well as normal LV function

  • The risks of surgery and prosthetic valve complications outweigh the benefits of preventing sudden cardiac death and prolonged survival in asymptomatic patient



Types of Valves

  • Bioprosthesis (Porcine)

  • Mechanical (St. Jude)

  • Homograft



Bioprosthesis vs. Mechanical Valves

  • Bioprosthesis valves are less durable than mechanical valves and begin to deteriorate after 5-6 years; usually do not require long-term coagulation

  • Mechanical valves are durable but require lifelong anticoagulation to control thromboembolism

  • Mechanical valve was associated with significantly lower 15 year mortality compared with bioprosthesis valve (66% vs. 79%) (Hammermeister, et al, 2000).

  • Mechanical valves are less obstructive than stented bioprosthesis valves of the same size (Bech-Hanssen, et al, 1999).

  • Despite a better survival rate with mechanical valve, the choice of valve should be tailored to the patient’s needs.



References

      • Alpert, J. T. (Ed.). (2001). The AHA Clinical Cardiac Consult. Philadelphia: Lippincott Williams & Wilkens.
      • Bech- Hassen, O., Caidahl, K., Wall, B., Myken, P., Lason, S., & Wallentin, I. (1999). Influence of aortic valve replacement, prosthesis type, and size of functional outcome and ventricular mass in patients with aortic stenosis. Journal of Thoracic Cardiovascular Surgery. 118(1):57-65.
      • Braunwald, E., Fauci, A. S., Kasper, D. L., Hauser, S. L., Longo, D. L., & Jameson, J. L. (2001). Harrison’s 15th Edition Principles of Internal Medicine. New York: McGraw-Hill.
      • Hammersmeister, K., Sethi, G. K., Henderson, W. G., Grover, F. L., Oprian, C., & Rahimtoola, S. H. (2000). Outcome 15 years after valve replacement with a mechanical versus a bioprosthetic valve: Final report of the Veterans Affairs Ramdomized trials. Journal of American Cardiology. 36:1152-1158.
      • Martin, L. & Coulden, R. (1999). Cardiac radiology: valvular heart disease. Clinics of North America. 37(2):319-338.
      • Munt, B. (1999). Physical examination in valvular aortic stenosis: correlation with stenosis severity and prediction of clinical outcome. American Heart Journal. 137(2):298-306.
      • Nowrangi, S. K., Connolly, H. M., Freeman, W. K., & Click, R. L. (2001). Impact of intraoperative transesophageal echocardiography among patients undergoing aortic valve replacement for aortic stenosis. Journal of American Society of Echocardiography. 14(9):863-6.
      • Otto, C. M. (1999). Valvular Heart Disease. Philadelphia: W. B. Saunders Company.
      • Tierney, Jr., L. M., McPhee, S. J., & Papadakis, M. A. (2002). Current Medical Diagnosis & Treatment: 2002. (41st Ed.). New York: Lange Medical Books/McGraw-Hill.




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