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Otto et al 2020 ACC/AHA Guideline for the Management of Valvular Heart Disease

February 2, 2021 Circulation. 2021;143:e72–e227. DOI: 10.1161/CIR.0000000000000923 e92

CLINICAL STATEMENTS AND GUIDELINES mismatch must be distinguished from primary myocardial dysfunction with only moderate AS. Dobutamine stress echocardiography may be useful with measurement of aortic velocity (or mean pressure gradient) and valve area at baseline and at higher flow rates (maximum dose dobutamine 20 mcg/kg per minute) under appropriate clinical and hemodynamic monitoring. Severe AS is characterized by a fixed valve area, resulting in an increase in transaortic velocity to ≥4 m/s (mean gradient ≥40 mm Hg) at any flow rate, but with valve area remaining ≤1.0 cm2. In contrast, in patients with moderate AS and primary LV dysfunction, there is an increase in valve area as volume flow rate increases, resulting in only a modest increase in transaortic velocity or gradient. Some patients fail to show an increase in stroke volume ≥20% with dobutamine, referred to as “lack of contractile reserve” or “lack of flow reserve.”8,9,19,28–32

4.	 The key measurements for clinical decision-making in patients with AS are the maximum aortic velocity, mean pressure gradient (calculated with the Bernoulli equation), and valve area (calculated with the continuity equation). An additional measurement that may be useful when there are discrepancies in these measures or in other clinical or imaging data is the ratio of the velocity in the LV outflow tract proximal to the aortic valve and the velocity in the narrowed aortic orifice. The outflow tract–to–aortic velocity ratio is independent of body size and eliminates potential errors in calculated valve area related to measurement of LV outflow tract diameter or area. A normal ratio is close to 1.0, whereas a ratio of ≤0.25 corresponds to a valve area 25% of normal for that patient, which is consistent with severe AS and is a predictor of symptom onset and adverse outcomes.12,13,21,22,23 5.	 The degree of aortic valve calcification is a strong predictor of clinical outcome, even when evaluated qualitatively by echocardiography.33 Quantitation of aortic valve calcium by CT imaging is especially useful in patients with low-flow, low-gradient AS of unclear severity with either a normal or reduced LVEF. Sex-specific Agaston unit thresholds for diagnosis of severe AS are 1300 in women and 2000 in men. These different thresholds reflect the contribution of leaflet fibrosis, in addition to calcification, to increased leaflet stiffness in women. CT imaging also is used for procedural planning in patients undergoing TAVI, for measurement of annulus area, leaflet length, and the annular–to–coronary ostial distance.14–18

3.2.1.2. Diagnostic Testing: Changing Signs or Symptoms In patients with known valvular AS, repeat TTE is prudent when physical examination shows an increase in the loudness of the murmur, the murmur peaks later in systole, the A2 component of the second heart sound is diminished or absent, or symptoms occur that might be attributable to AS. Repeat TTE is also appropriate in patients with AS who are exposed to increased hemodynamic demands, either electively, such as with noncardiac surgery or pregnancy, or acutely, such as with a systemic infection, anemia, or gastrointestinal bleeding. In these clinical settings, knowledge of the severity of valve obstruction and LV function is critical for optimizing loading conditions and maintaining a normal cardiac output. 3.2.1.3. Diagnostic Testing: Routine Follow-Up Timing of periodic clinical evaluation of asymptomatic patients with severe AS depends on comorbidities and patient-specific factors, as well as AS severity (Table 4). When severe AS is present (aortic velocity ≥4.0 m/s), the rate of progression to symptoms is high, with an event-free survival rate of only 30% to 50% at 2 years. In patients with asymptomatic severe AS, periodic monitoring is needed because symptom onset is insidious and may not be recognized by the patient. With moderate AS (aortic velocity 3.0–3.9 m/s), the average annual rate of progression is an increase in velocity of 0.3 m/s, increase in mean pressure gradient of 7 mm Hg, and decrease in valve area of 0.1 cm2. There is marked individual variability, with more rapid progression in older patients and in patients with more severe leaflet calcification. In patients with aortic sclerosis, defined as focal areas of valve calcification and leaflet thickening with an aortic velocity <2.0 m/s, progression to severe AS occurs in about 10% of patients within 5 years. Patients with BAV disease are also at risk of progressive valve stenosis, with AS being the most common reason for intervention in patients with a BAV (Section 5.1.1).1–13 3.2.1.4. Diagnostic Testing: Cardiac Catheterization Diagnostic TTE and Doppler data can be obtained in nearly all patients, but severity of AS may be underestimated if image quality is poor or if a parallel intercept angle is not obtained between the ultrasound beam and aortic jet. When data from noninvasive testing are nondiagnostic or if there is a discrepancy between clinical and echocardiographic evaluation, cardiac catheterization for determination of severity of AS can be helpful. Transaortic pressure gradient recordings allow measurement of the mean transaortic gradient via simultaneous LV and aortic pressure measurements. Aortic valve area

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