Aortic Stenosis

Introduction Etiology/Classification Etiology/Classification Pathophysiology Pathophysiology Clinical Manifestations Clinical Manifestations Evaluation Evaluation Management Management

Obstruction to left ventricular outflow Valvular Valvular Calcific/DegenerativeCalcific/Degenerative BiscuspidBiscuspid RheumaticRheumatic CongenitalCongenital Supravalvular Supravalvular Uncommon. Occurs as part of a congenital syndrome or from lipid deposits in severe familial hyperlipidemiasUncommon. Occurs as part of a congenital syndrome or from lipid deposits in severe familial hyperlipidemias Subvalvular Subvalvular CongenitalCongenital Fibromuscular membrane present in the LVOTFibromuscular membrane present in the LVOT Pathogenesis not completely understoodPathogenesis not completely understood Hypertrophic Cardiomyopathy Hypertrophic Cardiomyopathy

Valvular Aortic Stenosis Calcific/Degenerative Calcific/Degenerative Most commonMost common Normal trileaflet valve develops “age-related” calcificationNormal trileaflet valve develops “age-related” calcification Presents later in life (age 70-85)Presents later in life (age 70-85) Bicuspid valve Bicuspid valve Present in 1-2% of the populationPresent in 1-2% of the population More prevalent in men (70-80% of cases)More prevalent in men (70-80% of cases) Usually presents at a younger age (45-65)Usually presents at a younger age (45-65) Rheumatic Rheumatic Preferentially involves the mitral valve, so Rheumatic AS diagnosed when occurs concurrently with mitral valve diseasePreferentially involves the mitral valve, so Rheumatic AS diagnosed when occurs concurrently with mitral valve disease Congenital Congenital Typically unicuspid valve with single eccentric orificeTypically unicuspid valve with single eccentric orifice Ochronosis with alkaptonuria Ochronosis with alkaptonuria Anyone?Anyone?

Calcific/Degenerative AS Active disease process Active disease process “Rather than representing a degenerative and unmodifiable process, valvular aortic stenosis is an active process initiated at least in part by mechanical injury, mediated by lipid infiltration and a chronic inflammatory reaction, and further characterized by accumulation of extracellular matrix secreted primarily by resident valve fibroblasts as a response to inflammatory injury.” (Circulation 1994;90:844-53) Evidence that hemodynamic stress plays a role, as calcium deposition occurs on the aortic side of the valve where turbulence and shear stress are high.

Relation to atherosclerosis? Some commonality in risk factors for CAD and AS Some commonality in risk factors for CAD and AS Statins may have a role in slowing the progression of AS Statins may have a role in slowing the progression of AS Increased temperature variability in valves of patients with AS (similar to previous studies looking at thermal examination of CAD plaques) Increased temperature variability in valves of patients with AS (similar to previous studies looking at thermal examination of CAD plaques)

Normal Normal anatomy: three thin cusps with unrestricted systolic opening Normal anatomy: three thin cusps with unrestricted systolic opening Normal area 3-4 cm² Normal area 3-4 cm² Normal opening produces 2cm leaflet separation Normal opening produces 2cm leaflet separation Normal velocity: approx 1 m/s Normal velocity: approx 1 m/s

Pathophysiology Aortic sclerosis produces thickening of the valves, but no obstruction to outflow Aortic sclerosis produces thickening of the valves, but no obstruction to outflow When stenosis develops, the functional area of the valve decreases and causes a measurable obstruction of outflow When stenosis develops, the functional area of the valve decreases and causes a measurable obstruction of outflow Concentric LVH develops with normal chamber size Concentric LVH develops with normal chamber size Diastolic dysfunction due to increased myocardial cell mass and interstitial fibrosis Diastolic dysfunction due to increased myocardial cell mass and interstitial fibrosis Atrial contraction plays an important role in filling of the left ventricle in AS Atrial contraction plays an important role in filling of the left ventricle in AS Loss of appropriately timed atrial contraction could cause clinical deterioration Loss of appropriately timed atrial contraction could cause clinical deterioration

Pathophysiology NEJM, (9): 677

Pathophysiology

Symptoms Asymptomatic (long latency period) Asymptomatic (long latency period) Decrease in exercise tolerance Decrease in exercise tolerance Fatigue Fatigue Dyspnea Dyspnea Angina Angina Syncope Syncope Heart Failure Heart Failure

Signs (Physical Exam) Loud, late-peaking systolic murmur Loud, late-peaking systolic murmur Radiation to the carotids Radiation to the carotids Single or paradoxically split S2 Single or paradoxically split S2 Delayed and Diminished carotid upstroke (Pulsus parvus et tardus) Delayed and Diminished carotid upstroke (Pulsus parvus et tardus) Low output states may affect intensity of the murmur and carotid upstroke Low output states may affect intensity of the murmur and carotid upstroke Associated increase in GI bleeding from angiodysplasia Associated increase in GI bleeding from angiodysplasia

EKG and CXR Left ventricular hypertrophy (85 percent of patients) Left ventricular hypertrophy (85 percent of patients) Left atrial abnormality (80 percent) Left atrial abnormality (80 percent) Rounding of the left ventricular border with dilatation of the ascending aorta Rounding of the left ventricular border with dilatation of the ascending aorta

Echocardiography Qualitative Qualitative 2D imaging of valve anatomy (number of leaflets)2D imaging of valve anatomy (number of leaflets) Calcification/thickening, valve openingCalcification/thickening, valve opening Left ventricular functionLeft ventricular function Chamber size, wall thicknessChamber size, wall thickness Quantitative Quantitative Peak aortic valve velocityPeak aortic valve velocity Mean and maximum pressure gradientsMean and maximum pressure gradients Aortic valve area (continuity equation)Aortic valve area (continuity equation) Ratio of outflow tract to aortic jet velocityRatio of outflow tract to aortic jet velocity

Quantitative Doppler Assessment Dedicated non-imaging transducer Dedicated non-imaging transducer Maximum pressure gradient using the simplified Bernoulli equation Maximum pressure gradient using the simplified Bernoulli equation ∆Pmax = 4(Vmax)² Mean pressure gradient obtained from planimetry of the Doppler envelope; computer integrates velocity data to provide mean value Mean pressure gradient obtained from planimetry of the Doppler envelope; computer integrates velocity data to provide mean value Mean pressure gradient can also be estimated from published regression equations (for native valve AS): Mean pressure gradient can also be estimated from published regression equations (for native valve AS): ∆Pmean = (∆Pmax/1.45) + 2mmHg

Quantitative Assessment Pressure gradients are dependent on volume flow rates in addition to valve narrowing Pressure gradients are dependent on volume flow rates in addition to valve narrowing Differences in stroke volume can lead to inaccurate assessment of stenosis severity Differences in stroke volume can lead to inaccurate assessment of stenosis severity Coexisting AI will have a high transaortic pressure gradient Coexisting AI will have a high transaortic pressure gradient Patients with LV systolic dysfunction or coexisting MR may have low transaortic pressure gradient Patients with LV systolic dysfunction or coexisting MR may have low transaortic pressure gradient

Quantitative Assessment

Quality Control Angle θ should be as close to zero degrees as possible, significant errors in measurement when greater than 20 degrees Angle θ should be as close to zero degrees as possible, significant errors in measurement when greater than 20 degrees Mistaken identity (MR jet) Mistaken identity (MR jet) Locating highest velocity signals Locating highest velocity signals Recognize differences in reported data (peak instantaneous gradient vs peak-to- peak gradient) Recognize differences in reported data (peak instantaneous gradient vs peak-to- peak gradient)

Continuity Equation Valve Area Use principle of continuity of flow to calculate valve area; not affected by changes in SV (as when increased in AI and decreased SV with LV dysfunction) Use principle of continuity of flow to calculate valve area; not affected by changes in SV (as when increased in AI and decreased SV with LV dysfunction) LV outflow tract diameter LV outflow tract diameter Measured on 2D PSLA midsystolic imageMeasured on 2D PSLA midsystolic image Presume a circular shapePresume a circular shape Measure diameter (D), one-half of measured is radius (r)Measure diameter (D), one-half of measured is radius (r) Area = лr²Area = лr² LVOT VTI LVOT VTI Pulsed Doppler from apical approach, position sample just proximal to the stenotic valvePulsed Doppler from apical approach, position sample just proximal to the stenotic valve Aortic jet VTI Aortic jet VTI Continuous-wave Doppler from the window that yields the highest signalContinuous-wave Doppler from the window that yields the highest signal For clinical use, may simplify by substituting maximum velocities for velocity-time integrals (Otto) For clinical use, may simplify by substituting maximum velocities for velocity-time integrals (Otto)

Velocity Ratio Define “normal” valve area for the individual as the cross-sectional area of the outflow tract Define “normal” valve area for the individual as the cross-sectional area of the outflow tract The increase in velocity from outflow tract to aortic jet reflects stenosis severity regardless of size The increase in velocity from outflow tract to aortic jet reflects stenosis severity regardless of size Actual AVA / “normal” AVA ≈ (V lvot / V Ao) Actual AVA / “normal” AVA ≈ (V lvot / V Ao) Ratio of 1 indicates little obstruction, 0.5 half normal and 0.25 one-fourth normal value. Ratio of 1 indicates little obstruction, 0.5 half normal and 0.25 one-fourth normal value.

Low gradient with LV dysfunction At very low flow rates, valve opening may be inhibited leading to an underestimation of aortic valve area At very low flow rates, valve opening may be inhibited leading to an underestimation of aortic valve area May be difficult to distinguish severe AS with low-pressure gradient due to low SV from mild-moderate stenosis with reduced Ao valve opening due to low flow. May be difficult to distinguish severe AS with low-pressure gradient due to low SV from mild-moderate stenosis with reduced Ao valve opening due to low flow. Dobutamine echocardiography can help distinguish Dobutamine echocardiography can help distinguish Infuse 5mcg/kg/min in 5 mcg increments every 3 minutes until LVOT velocity or TVI reaches a normal value (usually at mcg/kg/min)Infuse 5mcg/kg/min in 5 mcg increments every 3 minutes until LVOT velocity or TVI reaches a normal value (usually at mcg/kg/min) True severe AS will have a fixed valve area True severe AS will have a fixed valve area Consider severe if valve area 30mmHG gradient with dobutamine Consider severe if valve area 30mmHG gradient with dobutamine Also used to assess inotropic reserve (increase in SV > 20% with dobutamine infusion) Also used to assess inotropic reserve (increase in SV > 20% with dobutamine infusion) Class IIa (B) Class IIa (B)

Natural History of Progression Aortic jet velocity: 0.3 m per second per year Aortic jet velocity: 0.3 m per second per year Increase in mean gradient pressure of 7mmHg per year Increase in mean gradient pressure of 7mmHg per year Decrease in valve area of 0.1cm² per year Decrease in valve area of 0.1cm² per year (JACC Vol 48 (3): e1-148.)

Management Presence of absence of symptoms Presence of absence of symptoms Severity of stenosis Severity of stenosis Status of the left ventricle Status of the left ventricle Presence of comorbidities Presence of comorbidities

Follow-up Exams An optimal schedule for repeated medical examinations has not been defined. An annual history and physical examination on patients with asymptomatic AS of any degree is reasonable. Annual echocardiogram for severe AS (Class I, LOE: B) An essential component of each visit is patient education about the expected disease course and symptoms. Because the rate of progression varies considerably, clinicians often perform an annual echocardiogram every year which may be appropriate. In patients with moderate AS, serial studies performed every 1 to 2 years are satisfactory. Mild AS, serial studies can be performed every 3 to 5 years (Class I, LOE: B). Echocardiograms should be performed more frequently if there is a change in signs or symptoms.

Cardiac Catheterization Class I 1. Coronary angiography is recommended before AVR in patients with AS at risk for CAD (Level of Evidence: B) 2. Cardiac catheterization for hemodynamic measurements is recommended for assessment of severity of AS in symptomatic patients when noninvasive tests are inconclusive or when there is a discrepancy between noninvasive tests and clinical findings regarding severity of AS. (Level of Evidence: C) 3. Coronary angiography is recommended before AVR in patients with AS for whom a pulmonary autograft (Ross procedure) is contemplated and if the origin of the coronary arteries was not identified by noninvasive technique. (Level of Evidence: C)

Aortic Valve Replacement

Aortic Balloon Valvotomy