A new method describing cross-sectional blood flow velocity profiles in the left ventricular outflow tract of patients with atrial fibrillation with the use of high-frame rate 2-dimensional color flow imaging

A new Doppler method was developed to evaluate the instantaneous cross-sect ional velocity profile variability in the left ventricular outlet tract in patients with atrial fibrillation. Blood flow velocities acquired at a high frame rate (>90 frames/s) from a single heart cycle were used to display t he velocity profile. In 9 patients, 2 heart cycles with different R-R inter val lengths were recorded in color flow mode in a transthoracic apical 5-ch amber and long-axis view. Raw digital ultrasound data were analyzed with an external personal computer. The data indicated a variable skew in the prof iles with the highest velocities and velocity-time integral (VTI) most ofte n located in the center and toward the septum. The maximum VTI overestimate d the mean VTI by approximately 40%. No significant difference existed betw een the two heartbeats. Thus the VTI can be averaged from heartbeats of dif ferent R-R lengths in atrial fibrillation.