DESCRIPTION

Obstruction to LV outflow

EPIDEMIOLOGY

• AS presents clinically at ages 70–80 yr in patients with trileaflet valves and at 50–60 yr in those with bicuspid valves.
• Rheumatic AS presents at an earlier age and is associated with aortic regurgitation and mitral disease.

Incidence

• Affects 5 in 10,000 people
• 80% of adults with symptomatic AS are men.

Prevalence

• Calcific aortic stenosis affects ~2% of persons >65.
• In adults undergoing surgery for AS, calcific AS accounts for 51% of cases, bicuspid AS 36%, and rheumatic disease 9%.

RISK FACTORS

• Advanced age
• Congenitally bicuspid aortic valve, coarctation, Turner syndrome
• Atherosclerotic risk factors: Dyslipidemia, inflammation, diabetes, HTN, smoking
• Male gender

GENERAL PREVENTION

A large prospective randomized clinical trial, Simvastatin and Ezetimide in Aortic Stenosis (SEAS), failed to demonstrate overall benefit or prevention of stenosis progression in patients with mild to moderate aortic stenosis treated with intensive lipid-lowering therapy. Although atherosclerotic risk factors are associated with aortic valve calcification, further study is needed before pharmacologic therapy can be recommended.

PATHOPHYSIOLOGY

• Calcium accumulation and decreasing mobility of the valve leaflets cause progressive increase in outflow obstruction over several years.
• Severe AS increases LV afterload and LV wall stress. Compensatory concentric LV hypertrophy (LVH) helps to normalize wall stress and maintain normal cavity size. LVH increases myocardial oxygen demand, leading to ischemia and fibrosis.
• LVH and fibrosis cause diastolic dysfunction/stiffness, which leads to elevated LV end diastolic pressure and increased pulmonary venous pressure.
• As obstruction becomes severe, cardiac output fails to increase with exertion.
• Development of atrial fibrillation with shortened diastolic filling time and loss of atrial kick leads to fall in cardiac output and pulmonary congestion.
• Systemic HTN adds the burden of vascular stiffness (increased LV afterload.)

ETIOLOGY

• Trileaflet valve with calcific (degenerative) change, the most common cause of valvular stenosis
• Congenitally bicuspid aortic valve with calcific change
• Rheumatic, in association with some degree of aortic insufficiency and mitral disease.

COMMONLY ASSOCIATED CONDITIONS

• Bicuspid aortic valve is associated with dilation of the ascending aorta; 50% of patients with coarctation have a bicuspid aortic valve
• Mitral annular calcium

Outline

• Description
• Epidemiology
  • Incidence
  • Prevalence
• Risk Factors
• General Prevention
• Pathophysiology
• Etiology
• Commonly Associated Conditions

History

• Patients may present with a history of a murmur or complaints of shortness of breath, chest pain, or syncopal episodes. 10% of bicuspid valve patients have a positive family history.
• Dyspnea. The most common initial symptom is exertional dyspnea.
• Angina is a common symptom, however 1/2 of AS patients with exertional angina have coexisting obstructive coronary artery disease.
• CHF symptoms may be due to severe outflow obstruction, diastolic function, or true systolic muscle failure.
• In severe AS, presyncope or syncope may be precipitated by inadequate preload as in exercise induced vasodilation or with volume depletion or diuretic therapy. Syncope usually occurs only with severe obstruction.
• Sudden death usually occurs only in previously symptomatic patients with severe AS.

Physical Exam

• Carotid pulse: With severe AS, the peak occurs later in systole (pulsus tardus) and pulse amplitude is decreased (pulsus parvus). A delayed upstroke is specific but not very sensitive. Elderly patients with stiff arteries will have normal carotid upstrokes. Therefore the presence of a normal carotid pulse contour in an older patient does not exclude AS.
• Murmur: Characteristically, a crescendo-decrescendo over the right 2nd intercostal space. Murmur duration correlates with severity. A late-peaking murmur represents more severe AS. Murmur intensity alone does not indicate severity. Patients with severe AS may only have a grade II murmur.
• The murmur radiates to the carotids and often to the apex and is diminished with Valsalva and other maneuvers that decrease cardiac output.
• An aortic ejection sound is heard in younger patients with congenitally abnormal mobile valves.
• The aortic component of the 2nd heart sound (S₂) is diminished or absent in severe AS because the immobile valve cannot produce the rapid deceleration needed to generate A₂. Delayed LV contraction may cause paradoxic splitting of S2.
• An S₄ is common and reflects increased atrial contribution to LV filling.

DIAGNOSTIC TESTS & INTERPRETATION

Lab

• ECG: LVH; ST-T changes of ischemia are common with severe AS. (LV strain); nonspecific changes include left atrial enlargement, left axis deviation, and left bundle-branch block. Exercise may bring out ischemic changes.
• Exercise testing: Useful to clarify patients’ true functional capacity.

Imaging

• CXR:
  • The cardiac silhouette is often normal. The ascending aorta may be dilated, especially with bicuspid valves.
• Echo:
  • Test of choice for diagnosing AS and quantifying its severity
  • Aortic gradients and aortic valve area are the key factors in determining severity.
  • Valve morphology is determined.
  • Measurement of LV size and function. The presence of regional wall motion abnormalities suggests the presence of coronary artery disease. Aortic root and ascending aortic diameter should also be measured.
  • AS severity is based on aortic valve area: mild (>1.5 cm²), moderate (1.0–1.5 cm²), severe (<1 cm²), and very severe (critical) (<0.75 cm²). Better is the aortic valve index, correcting for body surface area, <0.6 cm²/m² = severe aortic stenosis.
  • Other indicators of severe stenosis are mean gradient >40 mm Hg, peak velocity >4 m/sec.
• Dobutamine echo:
  • May be performed to determine contractile reserve and determine if AS is truly severe in a patient with low gradient.
• Cardiac catheterization:
  • Indicated for hemodynamic evaluation whenever there is discrepancy between the clinical picture and echo, but primarily to determine the presence of coronary artery disease.

DIFFERENTIAL DIAGNOSIS

• Supravalvular AS
• Hypertrophic cardiomyopathy
• Subaortic membrane
• Mild aortic stenosis with hypertensive heart disease and/or coronary disease

Outline

• History
• Physical Exam
• Diagnostic Tests & Interpretation
  • Lab
  • Imaging
• Differential Diagnosis

• AS is a primarily a mechanical problem, and medical treatment has little role in the treatment.
• With acute decompensation due to LV dysfunction, IV inotropic agents or IV nitroprusside may be used.
• Cardioversion of atrial fibrillation may allow return to relative symptom-free status, and attempts should be made to restore and maintain sinus rhythm.
• In nonoperative candidates, diuretics to treat pulmonary congestion often control symptoms.
• Cautions/relative contraindications:
  • Although vasodilators and diuretics are relatively contraindicated for the treatment of severe AS (reducing preload may cause a drop in cardiac output), many AS patients have systemic HTN that may be contributing to clinical symptoms and that needs treatment. So, too, patients with pulmonary congestion/edema may require immediate treatment with diuretics. In these circumstances, diuretics and/or vasodilators should be used with caution and with gradual titration of doses and with an understanding of the pathophysiology.
  • In very elderly patients who refuse or with contraindications to surgery, careful titration of these agents, may allow stabilization for several years.

ADDITIONAL TREATMENT

General Measures

• Under current guidelines endocarditis prophylaxis in no longer recommended for native valve disease unless there is a history of prior endocarditis.
• Patients with severe AS should avoid strenuous exercise.

Referral

Patients should be referred to a cardiologist for initial assessment when AS is diagnosed as moderate to severe, or if associated symptoms are present.

SURGERY

• Indications for aortic valve replacement:
  • Asymptomatic patients:
    • The risks of surgery and prosthetic valve complications outweigh the benefits of preventing sudden cardiac death and prolonging survival in truly asymptomatic patients (see "Exercise Testing").
  • Symptomatic patients:
    • AVR improves survival in patients with depressed as well as normal LV function.
    • Outcomes in the very elderly, >80 yr, are acceptable and age alone should not preclude surgery.
• AVR should be performed in patients with moderate to severe AS undergoing coronary artery bypass or other cardiac surgery.
• Mechanical versus bioprosthetic valve:
  • Current practice, in general, favors the use of mechanical valves in patients <65
  • Bioprostheses are usually used in patients >65 who have no other indication for chronic anticoagulant therapy
• Aortic balloon valvotomy and transcatheter valve replacement:
  • Percutaneous balloon dilatation offers little benefit for adults with calcific AS.
  • Early experience with percutaneous or minimally invasive transapical transcatheter aortic valve replacement shows promising results. Clinical study to date, however, is limited. The procedure can be considered for patients with serious severe comorbidities who are not candidates for surgical AVR.

Outline

• Additional Treatment
  • General Measures
  • Referral
• Surgery

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

• Mild: Annual history and physical exam and echo every 5 yr
• Moderate: More frequent visits and echo every 2 yr
• Severe AS: Yearly echo and office visits every 6 mo.
• Echo should be performed if any change occurs in clinical findings or symptoms.

PATIENT EDUCATION

• Development of symptoms in AS patients is 1 of the cornerstones of the decision-making process. Asymptomatic patients must therefore understand the importance of reporting the onset of dyspnea, angina, or syncope.
• Activity:
  • Recommendations for physical activity are based on the severity of the stenotic lesion.
    • Asymptomatic patients with mild AS: Physical activity is not restricted and patients can participate in competitive sports.
    • Patients with moderate AS: Should avoid competitive sports that involve high dynamic and static muscular demands. Other forms of exercise can be performed after an exercise test with no ST-segment changes or sustained arrhythmias.
    • Patients with severe AS should be advised to limit their activity to relatively low levels.

PROGNOSIS

• Similar to age-matched normal adults during the asymptomatic period.
• Development of CHF is associated with a grave prognosis; 50% 1-yr mortality without surgical intervention.

COMPLICATIONS

• CHF
• Atrial fibrillation
• Sudden cardiac death
• Infective endocarditis
• GI bleeding due to intestinal arteriovenous malformation
• Prosthetic valve–related complications

Outline

• Follow-Up Recommendations
  • Patient Monitoring
• Patient Education
• Prognosis
• Complications

CODES

ICD9

424.1 Aortic valve disorders

SNOMED

60573004 aortic valve stenosis (disorder)

ADDITIONAL READING

• Bonow RO, Carabello B, de Leon AC Jr, et al. ACC/AHA 2008 Focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease): Endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation. 2008;118:e523–e661.
• Lindroos M, Kupari M, Heikkila J, et al. Prevalence of aortic valve abnormalities in the elderly: An echocardiographic study of a random population sample. J Am Coll Cardiol. 1993;21:1220–1225.
• Monin JL, Quere JP, Monchi M, et al. Low gradient aortic stenosis operative risk stratification and predictors for long-term outcome; a multicenter study using dobutamine stress hemodynamics. Circulation. 2005;108:319–324.
• Otto CM. Valvular aortic stenosis; diseases severity and timing of intervention. J Am Coll Cardiol. 2006;47:2141–2151.
• Pellikka PA, Sarano ME, Nishimura RA, et al. Outcome of 622 adults with asymptomatic hemodynamically significant aortic stenosis during prolonged follow-up. Circulation. 2005;111:3290–3295.
• Piper C, Hering D, Kleikamp G, et al. Valve replacement in octogenarians: Arguments for an earlier surgical intervention. J Heart Valve Dis. 2009:18:239–244.
• Roberts WC, Ko JM. Frequency by decades of unicuspid, bicuspid, and tricuspid aortic stenosis, with or without associated aortic regurgitation. Circulation. 2005;111:920–925.
• Rosseb AB, Pedersen TR, Brudi P, et al. Intensive lipid lowering with simvastatin and ezetimide in aortic stenosis. N Engl J Med. 2008;359:1343–1356.
• Sharma UC, Barenbrug P, Pokharel S, et al. Systematic review of the outcome of aortic valve replacement in patients with aortic stenosis. Ann Thorac Surg. 2004;78:90–95.
• Webb JG, Altwegg L, Boone RH, et al. Transcatheter aortic valve implantation: Impact on clinical and valve related outcomes. Circulation. 2009;119:3009–3016.

Linda A. Pape