Echocardiographic assessment of left ventricular twisting and untwisting rate in normal subjects by tissue doppler and velocity vector imaging: Comparison of two methods

I have read "Echocardiographic Assessment of Left Ventricular Twisting and Untwisting Rate in Normal Subjects by Tissue Doppler and Velocity Vector Imaging: Comparison of Two Methods" with great interest and congratulate the authors on their comprehensive and very balanced overview of recent studies on the left ventricular (LV) deformation analysis (1). However, there are three incorrect aspects that in my opinion needs clarification. Frist, the authors calculated the LV rotation by integrating the rotational velocity, determined from the DTI velocities of the septal and lateral regions, and correcting [R (t)] for the LV radius over time. R (t) is incorrect in Equation 1; it should be improved to: