Aortic Stenosis: Changing Disease Concepts

Abstract

Aortic stenosis (AS) occurs in almost 10% of adults over age 80 years with a mortality about 50% at 2 years unless outflow obstruction is relieved by aortic valve replacement (AVR). Development of AS is associated with anatomic, clinical and genetic risk factors including a bicuspid valve in 50%; clinical factors that include older age, hypertension, smoking, diabetes and elevated serum lipoprotein(a) [Lp(a)] levels; and genetic factors such as a polymorphism in the Lp(a) locus. Early stages of AS are characterized by focal areas of leaflet thickening and calcification. The rate of hemodynamic progression is variable but eventual severe AS is inevitable once even mild valve obstruction is present. There is no specific medical therapy to prevent leaflet calcification. Basic principles of medical therapy for asymptomatic AS are patient education, periodic echocardiographic and clinical monitoring, standard cardiac risk factor evaluation and modification and treatment of hypertension or other comorbid conditions. When severe AS is present, a careful evaluation for symptoms is needed, often with an exercise test to document symptom status and cardiac reserve. In symptomatic patients with severe AS, AVR improves survival and relieves symptoms. In asymptomatic patients with severe AS, AVR also is appropriate if ejection fraction is < 50%, disease progression is rapid or AS is very severe (aortic velocity > 5 m/s). The choice of surgical or transcatheter AVR depends on the estimated surgical risk plus other factors such as frailty, other organ system disease and procedural specific impediments.

Keywords: Aortic stenosis; Echocardiography; Valve replacement.

Fig. 1. Evaluation and management of the patient with low-flow low-gradient aortic stenosis. The AHA/ACC class recommendation (I, IIa, or IIb) is shown in parentheses corresponding to Table 3. AHA/ACC: 2014 American Heart Association and American College of Cardiology Guidelines, AS: aortic stenosis, AVA: aortic valve area, AVR: aortic valve replacement which may be either surgical or transcatheter, DSE: dobutamine stress echocardiography (low dose), EF: ejection fraction, SVI: stroke volume indexed to body size, V_max: maximum aortic velocity.

Fig. 2. Timing of aortic valve replacement in adults with asymptomatic aortic stenosis. The AHA/ACC class recommendation (I, IIa, or IIb) is shown in parentheses corresponding to Table 3. AHA/ACC: 2014 American Heart Association and American College of Cardiology Guidelines, AS: aortic stenosis, AVR: aortic valve replacement which may be either surgical or transcatheter, BP: blood pressure, EF: ejection fraction, ETT: exercise treadmill test, ex: exercise, V_max: maximum aortic velocity.