Aortic Stenosis

1. Etiology
   1. Congenital Bicuspid Valve (Most common)
      1. Twice as common in men
      2. Slow increase in stenosis (progressive sclerosis)
         1. Childhood: mild stenosis and asymptomatic
         2. Ages 20-40: moderate stenosis develops
         3. Over age 40: severe stenosis develops
   2. Atherosclerosis
      1. Normal tricuspid valve becomes rigid with age
      2. Develops over age 70
      3. Rarely severe
   3. Rheumatic Fever
      1. Slowly progressive stenosis
   4. Subacute Bacterial Endocarditis
2. Pathophysiology: Course
   1. Initial: Long asymptomatic latent period
   2. Changes related to greater left ventricular outflow obstruction and increased LV pressures
      1. Next: Left Ventricular Hypertrophy
      2. Next: Diastolic Dysfunction
      3. Next: Congestive Heart Failure
      4. Next: Increased myocardial oxygen demand and secondary Angina
      5. Next: Hypotension and Syncope in response to Exercise
3. Symptoms
   1. Mild to Moderate stenosis
      1. Asymptomatic
   2. Severe Obstruction
      1. Syncope
      2. Exercise induced Angina
      3. Dyspnea on exertion to Dyspnea at rest
      4. Congestive Heart Failure
4. Signs
   1. Classic Murmur
      1. Harsh crescendo-decrescendo Systolic Murmur
      2. Medium pitch
      3. Heard best at right upper Sternum
      4. May also be heard at apex
   2. Mild Aortic Stenosis
      1. Loud ejection click (best heard at apex)
      2. Short, early Systolic Murmur
      3. Loud A2 heart sound (best heard at aortic area)
   3. Moderate Aortic Stenosis
      1. Ejection click (best heard at apex)
      2. Early Systolic Murmur (loudest at aortic area)
         1. Transmitted to Supraclavicular, Carotids, Apex
         2. Harsh
         3. Ends well before A2 heart sound
      3. Arterial Pulse altered
         1. Upstroke of the pulse has shudder, and is prolonged
      4. Apex impulse may be abnormal, accentuated
         1. Slightly sustained
         2. Presystolic Shoulder ("a wave")
            1. Precedes major systolic impulse
      5. Systolic thrill may be palpated at base
   4. Severe Aortic Stenosis
      1. Ejection click NO longer present
      2. A2 heart sound is markedly diminished
      3. Systolic Murmur
         1. Variable loudness (may be quiet despite severity)
         2. Long, nearly holosystolic
         3. Harsh (especially at aortic area)
      4. Carotid pulse very abnormal
         1. Very slow and long upstroke
         2. Overall small quality to pulse
      5. Apical impulse abnormal
         1. Strong and sustained for all of systole
5. Signs: Most significant findings
   1. High Positive Likelihood Ratio (rule-in diagnosis)
      1. Tardus (slow rate of rise to carotid or brachial pulse - nudge instead of a strong tap)
      2. Parvus (low pulse volume)
   2. Low Negative Likelihood Ratio (most likely to rule-out diagnosis)
      1. Absence of late peaking murmur (early peaking murmur is typically benign)
      2. Lack of radiation to right carotid or clavicle
6. Classification: Aortic Stenosis Severity
   1. Aortic jet velocity
      1. Normal: <2.5 m/sec
      2. Mild: 2.5-2.9 m/sec
      3. Moderate: 3-4 m/sec
      4. Severe: >4 m/sec
   2. Mean gradient
      1. Mild: <25 mmHg
      2. Moderate: 25-40 mmHg
      3. Severe: >40 mmHg
      4. Critical: >50 mmHg
   3. Aortic valve area
      1. Normal: 3 to 4 cm2
      2. Mild: 1.5 to 2 cm2
      3. Moderate: 1 to 1.5 cm2
      4. Severe: <1 cm2
      5. Critical: <0.8 cm2
7. Associated conditions
   1. AV Node Block (often concurrent with Aortic Stenosis)
   2. Aortic Coarctation
   3. Aortic Dissection
8. Diagnosis
   1. Electrocardiogram (only abnormal in severe stenosis)
      1. Left Ventricular Hypertrophy
      2. T Wave reduction in leads I, avL, V5, V6
      3. Left Anterior Hemiblock or Left Bundle Branch Block
      4. Complete AV Block
   2. Chest XRay
      1. Apical Contour abnormal suggests large left ventricle
      2. Prominent ascending aorta
      3. Aortic valve calcification
   3. Echocardiogram
      1. Frequency: See Monitoring below
      2. Can distinguish normal aortic valve from:
         1. Bicuspid valve
         2. Mildly obstructed valve
         3. Thickened, sclerotic valve
   4. Cardiac Catheterization (Angiogram)
      1. Can directly measure left ventricular pressure gradient
9. Differential Diagnosis
   1. Supravalvular Aortic Stenosis
   2. Membranous supravalvular Aortic Stenosis
   3. Hypertrophic Cardiomyopathy (IHSS)
   4. Mitral Regurgitation
10. Management: Symptomatic and severe stenosis (>40 mmHg across valve)
    1. General
       1. SBE Prophylaxis is no longer recommended (until aortic valve replacement)
       2. Avoid strenuous Exercise or activity
       3. See Cardiac Risk Management
       4. Manage comorbid Atrial Fibrillation with rate control
          1. See Atrial Fibrillation Rate Control
          2. Use with caution Beta Blockers and Calcium Channel Blockers
             1. Risk of exacerbating left ventricular Systolic Dysfunction
    2. Preferred agents
       1. ACE Inhibitors
       2. Amlodipine (Norvasc)
    3. Agents to use with caution
       1. Diuretics
          1. Indicated for Congestive Heart Failure
          2. Use with caution (lowers LV filling pressure)
       2. Use Nitroglycerin only with caution
          1. Monitor Blood Pressure carefully
          2. Volume expansion may be required
       3. Use Beta Blockers with caution
          1. Risk of Congestive Heart Failure
    4. Agents to avoid
       1. Peripheral Alpha Adrenergic Antagonists
11. Management: Aortic Valve Replacement Indications
    1. Synopsis
       1. Aortic valve area <1 cm2 is criteria for stenosis unless completely normal cardiovascular testing
    2. Criteria 1: Severe Aortic Stenosis (see classification above) and
       1. Aortic jet velocity: >4 m/sec
       2. Mean gradient: >40 mmHg
       3. Aortic valve area: <1 cm2
    3. Criteria 2: One of criteria below
       1. Symptomatic Aortic Stenosis
       2. Possible symptomatic Aortic Stenosis with abnormal stress test (symptoms, Hypotension)
       3. Heart Surgery (e.g. CABG) is already planned
       4. Left ventricular ejection fraction <50%
       5. Severe aortic valve calcification or rapid progression
       6. Asymptomatic but near critical Aortic Stenosis
          1. Aortic valve gradient >60 mmHg
          2. Aortic valve orifice <0.6 cm2
          3. Nishimura (2005) Mayo Reviews Lecture, Rochester
12. Precautions: Surgical evaluation should be prompt for severe Aortic Stenosis
    1. Risk of sudden death
    2. Valve replacement may be indicated even if ejection fraction low
    3. Valve replacement is not effective if low ejection fraction and low valve gradient
    4. Carabello (2002) N Engl J Med 346:677-82
13. Complications
    1. Left Ventricular Hypertrophy
    2. Congestive Heart Failure
    3. Exacerbation of Coronary Artery Disease
    4. Sudden Death
14. Monitoring: Echocardiogram Frequency
    1. Mild Aortic Stenosis: Every 3-5 years
    2. Moderate Aortic Stenosis: Every 2 years
    3. Severe Aortic Stenosis: Every year
15. Prognosis: Prior to Valve Replacement
    1. Mild Aortic Stenosis: Good (slow progression)
       1. Anticipate active and asymptomatic for 10-50 years
    2. Asymptomatic severe Aortic Stenosis
       1. At 5 years, 72% will die or have symptoms
       2. Recent data suggests sudden death rate is high
       3. Pellikka (2005) Circulation 111:3290-5
    3. Symptomatic severe Aortic Stenosis: Poor prognosis
       1. Most patients will have symptom progression
       2. Anticipate death within 3 years in most patients
16. References
    1. Kondos (1998) CMEA Medicine Review Lecture, San Diego
    2. Assi (1998) Postgrad Med 104(6):99-110
    3. Bonow (1998) Circulation 98:1949-84
    4. Bonow (2006) Circulation 114(5): e84-e231
    5. Carabello (1997) N Engl J Med 337(1):32-41
    6. Grimard (2008) Am Fam Physician 78(6): 717-25
    7. Lester (1998) Chest 113:1109-14
    8. Otto (2006) J Am Coll Cardiol 47(11): 2141-51
    9. Shipton (2001) Am Fam Physician 63(11):2201-8