Aortic stenosis by epifani d. Armedilla

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

• Obstruction of blood flow across the aortic valve during left ventricular systole

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.