1 Introduction
Echocardiography is the essential tool for assessing the severity of aortic stenosis (AS).1-5 Peak transaortic valve jet velocity (Vmax), mean transaortic valve pressure gradient (mPG), and aortic valve area (AVA) are the main indexes of AS severity.3,4 However, one or two indexes of them may sometimes discord with each other, and require another solution. One of the possible situations may be seen in case of depressed left ventricular (LV) function. In case of AS with depressed LV function, Vmax, mean PG, and stenotic AVA are underestimated because of reduced stroke volume (SV) known as low-flow low-gradient (LFLG) AS.6 In such cases, dobutamine stress echocardiography is recommended for correct diagnosis of the severity of AS.3,4,7
Ratio of acceleration time (AT) to ejection time (ET) of transaortic flow, i.e. AT/ET, is reported as a reliable index of severity of AS.8–12 AT/ET is positively correlated with Vmax, mean PG, and negatively correlated with AVA or indexed AVA (AVAi). Also, AT/ET is proposed as an alternative to detect prosthetic valve malfunction caused by stenosis.13
To obtain the appropriate Vmax and mPG in patients with AS, approaching by multiple acoustic windows are recommended by ASE guideline.4 However, the acoustic window dependency on the measurement of AT/ET have not been well studied yet, therefore, we investigated the effect of different approach on AT/ET in patients with AS.