BEAT AVERAGING ALTERNATIVES FOR TRANSMITRAL DOPPLER FLOW VELOCITY IMAGES

To characterize diastolic function from transmitral Doppler data, the image's maximum velocity envelope (MVE) is fit by a model for flow vel ocity, To reduce the physiologic beat-to-beat variability of best-fit determined model parameters, averaging of multiple cardiac cycles is i ndicated. To assess variability mathematically, we modeled physiologic noise as a random (normally-distributed) process and evaluated three methods of averaging (1, averaging model parameters from single images ; 2, averaging images; and 3, averaging MVEs) using clinical datasets (50 continuous beats from 5 subjects). Method 2 generates a positive b ias because low-velocity beats will not contribute to the composite MV E, The difference between Methods 3 and 1 is less than 2.0 E-5 (m/s)(2 ) for uncorrelated model parameters. Input having 10% beat-to-beat var iation yields a bias of <4% for model parameter mean. Hence, Method 1 was, in general, more robust than Method 3. (C) 1998 World Federation for Ultrasound in Medicine & Biology.