Aortic Stenosis

Aka: Aortic Stenosis, Valvular Aortic Stenosis

II. Epidemiology

Prevalence: 3% of those over age 65 years old in U.S.
Most significant cardiac valve disorder in the developed world

III. Etiology

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
Atherosclerosis
1. Normal aortic tricuspid valve becomes calcified and rigid with age
2. Gradually develops, typically presenting over age 70 years
3. Rarely severe
Rheumatic Fever
1. Slowly progressive stenosis
Subacute Bacterial Endocarditis

IV. Pathophysiology: Course

Initial: Long asymptomatic latent period
Course
1. Increased left ventricular outflow obstruction and flow restriction
  1. Increased left ventricular pressures
2. Next: Left Ventricular Hypertrophy (left ventricular wall thickening with preserved LV volume)
3. Next: Diastolic Dysfunction (resistance to LV filling with preserved systolic function)
4. Next: Systolic Dysfunction and Congestive Heart Failure
5. Next: Increased myocardial oxygen demand, Coronary Artery compression and secondary Angina
6. Next: Hypotension and Syncope in response to Exercise

V. Symptoms

Mild to Moderate stenosis
1. Asymptomatic
Severe Obstruction
1. Dyspnea (most common presenting symptom)
  1. Dyspnea on exertion progresses to Dyspnea at rest
2. Other presenting symptoms
  1. Syncope
  2. Exercise induced Angina
  3. Congestive Heart Failure

VI. Signs

Classic Murmur
1. Harsh, late-peaking, crescendo-decrescendo Systolic Murmur
2. Medium pitch
3. Heard best at right upper Sternum (second intercostal space)
4. May also be heard at apex (esp. elderly)
5. May radiate into Carotid Artery region
Mild Aortic Stenosis
1. Loud ejection click (best heard at apex)
2. Short, early Systolic Murmur (at right second intercostal space)
3. Loud A2 heart sound (best heard at aortic area)
Moderate Aortic Stenosis
1. Ejection click (best heard at apex)
2. Early Systolic Murmur (loudest at right second intercostal space)
  1. Transmitted to Supraclavicular, Carotids, Apex
  2. Harsh
  3. Systolic ejection murmur that peaks later in systole
  4. Ends well before A2 heart sound
3. Arterial Pulse altered
  1. Upstroke of the pulse has shudder
  2. Delayed, prolonged, low-volume carotid pulsation (Pulsus parvus et tardus)
    1. Test Sensitivity 70% and Test Specificity 98% in Aortic Stenosis
    2. Roldan (1996) Am J Cardiol 77(15): 1327-31 [PubMed]
4. Apex impulse may be abnormal, accentuated
  1. Slightly sustained
  2. Presystolic Shoulder (“a wave”) precedes major systolic impulse
5. Systolic thrill may be palpated at base
6. S4 Gallup Rhythm
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 (Pulsus parvus et tardus)
  2. Overall very weak pulse
5. Brachioradial delay
  1. Right brachial pulse and right radial pulse are simultaneously palpated
  2. Radial pulse is felt after the brachial pulse in severe Aortic Stenosis (also in MR with severe CHF)
    1. Leach (1990) Lancet 335(8699):1199-201 [PubMed]
6. Apical impulse abnormal
  1. Strong and sustained for all of systole

VII. Signs: Most significant findings

Precautions
1. Pulse changes may be masked by atherosclerosis or Hypertension
2. Murmur may be less prominent with reduced LV function
3. Murmur may radiate to apex but not carotids in elderly
High Positive Likelihood Ratio (rule-in diagnosis)
1. Pulsus parvus et tardus (low pulse volume and slow rate of rise of carotid or brachial pulse)
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
3. Normally split Second Heart Sound (S2)

VIII. Classification: Aortic Stenosis Severity

Aortic jet velocity (transaortic velocity)
1. Normal: <2.0 m/sec
2. Mild: 2.0 to 2.9 m/sec
3. Moderate: 3.0 to 3.9 m/sec
4. Severe: >4.0 m/sec
Mean pressure gradient
1. Normal: <10 mmHg
2. Mild: 10-20 mmHg
3. Moderate: 20-40 mmHg
4. Severe: >40 mmHg
5. Critical: >50 mmHg
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

IX. Associated Conditions

AV Node Block (often concurrent with Aortic Stenosis)
Aortic Coarctation
Aortic Dissection

X. Diagnotics: Electrocardiogram

Precautions
1. Electrocardiogram may only be abnormal in moderate to severe Aortic Stenosis
Common findings
1. Left Ventricular Hypertrophy
  1. Peak systolic gradient (PSG) has been correlated to the QRS amplitude (LVH criteria)
  2. Kishore (1990) Indian Heart J 42(1): 62-5 [PubMed]
Other findings
1. T Wave reduction in leads I, avL, V5, V6
2. Left Anterior Hemiblock or Left Bundle Branch Block
3. Complete AV Block

XI. Imaging

Chest XRay
1. Precautions
  1. Chest XRay is a low yield test in Aortic Stenosis diagnosis
  2. Chest XRay is primarily used to evaluate presenting symptoms (Dyspnea, Syncope, Chest Pain)
2. Findings (unreliable)
  1. Apical Contour abnormal suggests large left ventricle
  2. Prominent ascending aorta
  3. Aortic valve calcification
Echocardiogram
1. Most important study in the evaluation of suspected Aortic Stenosis
2. Frequency
  1. Initial presentation
  2. Once Aortic Stenosis is diagnosed, repeat echo per monitoring schedule based on severity (see below)
3. Indications
  1. Loud (grade 3), unexplained Systolic Murmur (esp. holosystolic, late systolic)
  2. Single Second Heart Sound
  3. History of bicuspid aortic valve
  4. Symptoms suggestive of Aortic Stenosis
  5. New murmur associated with new symptom presentation (Dyspnea, Syncope, Angina)
4. Findings
  1. Aortic Stenosis diagnosis
    1. Aortic Stenosis grading with aortic valve gradient, orifice size, jet velocity
    2. Aortic Stenosis complications (LV hypertrophy, Diastolic Dysfunction, Systolic Dysfunction)
  2. Other aortic valve disorders
    1. Bicuspid valve
    2. Mildly obstructed valve
    3. Thickened, sclerotic valve
  3. Other valve disorders presenting similarly to Aortic Stenosis (Dyspnea, Syncope, Angina)
    1. Acute Mitral Regurgitation (especially due to Myocardial Infarction with papillary muscle rupture)
    2. Prosthetic valve disorders (e.g. valvular regurgitation or obstruction)
Cardiac Catheterization (Angiogram)
1. Can directly measure left ventricular pressure gradient

XII. Differential Diagnosis

Supravalvular Aortic Stenosis
Membranous supravalvular Aortic Stenosis
Hypertrophic Cardiomyopathy (IHSS)
Mitral Regurgitation

XIII. Management: General Measures

Asymptomatic Aortic Stenosis progression is not prevented by any specific measures
SBE Prophylaxis is no longer recommended (until aortic Valve Replacement, or history of prior endocarditis)
Manage comorbid conditions
Avoid strenuous Exercise or activity in moderate to severe Aortic Stenosis
1. Limit activity in high Dynamic Sports and high Static Sports
2. No restriction needed for mild Aortic Stenosis
Reduce cardiovascular risk
1. See Cardiac Risk Management
2. Tobacco Cessation
3. Consider Aspirin prophylaxis
4. Consider Statin for lipid lowering
5. Control Hypertension (40% of patients)
  1. ACE Inhibitors
  2. Amlodipine (Norvasc)
  3. Diuretics (slowly titrate from low dose)
  4. Avoid peripheral alpha blockers (risk of Syncope)
Manage comorbid Atrial Fibrillation (5% of patients) 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

XIV. Management: Symptomatic and severe stenosis (>40 mmHg across valve or aortic jet velocity >4.0 m/s)

Admit symptomatic severe Aortic Stenosis and plan aortic Valve Replacement
Preferred agents
1. ACE Inhibitors
2. Amlodipine (Norvasc)
3. Nitroprusside
  1. Consider in critical Aortic Stenosis and ejection fraction <35%
  2. Khot (2003) N Engl J Med 348(18): 1756-63 [PubMed]
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
Agents to avoid
1. Peripheral Alpha Adrenergic Antagonists

XV. Management: Aortic Valve Replacement Indications

Synopsis
1. Aortic valve area <1 cm2 is criteria for stenosis unless completely normal cardiovascular testing
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
Criteria 2: One of criteria below
1. Symptomatic Aortic Stenosis
2. Possible symptomatic Aortic Stenosis (esp. elderly) with abnormal stress test
  1. Symptoms or Hypotension
  2. Left Ventricular ejection fraction <50%
  3. Dobutamine Stress Echo with <=1 cm valve area or aortic jet velocity >=4 m/s
3. Heart Surgery (e.g. CABG) is already planned (consider AVR even if moderate Aortic Stenosis)
4. Left ventricular ejection fraction <50%
5. Severe aortic valve calcification or rapid progression (e.g. 0.3 m/s increase per year)
6. Low-flow, low gradient severe Aortic Stenosis may initially be misdiagnosed as moderate Aortic Stenosis
  1. Most common in older women with Hypertension
7. Asymptomatic but near critical Aortic Stenosis
  1. Aortic valve gradient >60 mmHg
  2. Aortic valve orifice <0.6 cm2
  3. Aortic jet velocity >5.0 m/s
  4. Nishimura (2005) Mayo Reviews Lecture, Rochester

XVI. Precautions: Surgical evaluation should be prompt for severe Aortic Stenosis

Do not Exercise Stress Test severe Aortic Stenosis with symptoms (high risk for adverse events)
1. Consider stress test only if symptomatic status is unclear
Risk of sudden death
Valve Replacement may be indicated even if ejection fraction low
Valve Replacement is not effective if low ejection fraction and low valve gradient
Carabello (2002) N Engl J Med 346:677-82 [PubMed]

XVII. Complications

XVIII. Monitoring: Echocardiogram Frequency

Mild Aortic Stenosis: Every 3-5 years
Moderate Aortic Stenosis: Every 1-2 years
Severe Aortic Stenosis: Every 6-12 months

XIX. Prognosis: Prior to Valve Replacement

Mild Aortic Stenosis: Good (slow progression)
1. Anticipate active and asymptomatic for 10-50 years
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 [PubMed]
Symptomatic severe Aortic Stenosis: Poor prognosis
1. Most patients will have symptom progression
2. Anticipate death within 3 years in most patients
3. Even mild pre-AVR symptoms predict a 2 year mortality >50%

XX. Prognosis: After Aortic Valve Replacement

Consider transcatheter Valve Replacement in those who are at very high surgical risk
Mortality at 30 days post-AVR: 3% (up to 4.5% if CABG performed at the same time)

XXI. Resources

Late Aortic Stenosis (University of Washington School of Medicine)
1. https://depts.washington.edu/physdx/audio/lateas.mp3

XXII. References

Kondos (1998) CMEA Medicine Review Lecture, San Diego
Schauer et al. (2016) Crit Dec Emerg Med 30(9):13-9
Assi (1998) Postgrad Med 104(6):99-110 [PubMed]
Bonow (1998) Circulation 98:1949-84 [PubMed]
Bonow (2006) Circulation 114(5): e84-e231 [PubMed]
Carabello (1997) N Engl J Med 337(1):32-41 [PubMed]
Grimard (2016) Am Fam Physician 93(5): 371-8 [PubMed]
Grimard (2008) Am Fam Physician 78(6): 717-25 [PubMed]
Lester (1998) Chest 113:1109-14 [PubMed]
Otto (2006) J Am Coll Cardiol 47(11): 2141-51 [PubMed]
Shipton (2001) Am Fam Physician 63(11):2201-8 [PubMed]

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