2.2 Two-Dimensional transthoracic echocardiography
Standard 2-dimensional (2D) and Doppler transthoracic echocardiography was performed at baseline and after TMVI [30 (9-35) days] using an iE33 ultrasound system (Philips Healthcare, Andover, MA, USA) equipped with a 2.5-MHz transducer. All measurements were made according to the current guideline.13The peak LVOT velocity was measured with continuous Doppler echocardiography in apical LV long-axis view, aligning the continuous Doppler beam as parallel as possible to the LVOT jet. The pressure gradient (PG) across LVOT was calculated using simplified Bernoulli equation; PG = 4 × (peak velocity)2. The change in PG across LVOT (ΔPG) was defined as follows; ΔPG = PG across LVOT after TMVI – PG across LVOT before TMVI, and ΔPG ≥10 mm Hg was defined as significant increase in LVOT gradient according to the Mitral Valve Academic Research Consortium definition.14