Energy Loss Index in Aortic Stenosis

In the American Heart Association–American College of Cardiology and European Society of Cardiology–European Association for Cardio-Thoracic Surgery guidelines, aortic valve replacement (AVR) is considered a class I indication in patients with aortic stenosis (AS) if the stenosis is severe and the patient has symptoms or left ventricular ejection fraction <50%. Hence, accurate assessment of the hemodynamic severity of the valvular stenosis is crucial for clinical decision making. The stenosis severity is generally determined by measuring the transvalvular pressure gradient or the aortic valve effective orifice area (AVA); however, these conventional parameters do not account for the extent of pressure recovery that may occur downstream of the stenosis. In an article published in 2000 in Circulation, we proposed a new Doppler echocardiographic parameter based on the energy loss concept to adjust the AVA for pressure recovery, and we postulated that this energy loss index (ELI) would improve assessment of stenosis severity and risk stratification in AS. Thirteen years later, Bahlmann and colleagues publish in this issue of Circulation the first prospective study to demonstrate that ELI provides independent and incremental prognostic information to that derived from conventional measures of AS severity. In this elegant substudy of the SEAS (Simvastatin Ezetimibe in Aortic Stenosis) trial, the authors report that a 1 cm2/m2 reduction in baseline ELI predicts a 2-fold increase in the risk of aortic valve events and of the composite of mortality and heart failure hospitalization after adjustment for peak aortic jet velocity or mean gradient.