Two-dimensional color Doppler estimation of the severity of atrioventricular valve regurgitation: important effects of instrument gain setting, pulse repetition frequency, and carrier frequency.

Literature reports of good correlation between two-dimensional color Doppler and ventriculography for estimation of the severity of atrioventricular valve regurgitation have appeared. Local experience has been variable. The purpose of this study was to evaluate three factors for their effect on two-dimensional color Doppler display of the apparent area of regurgitant flow. The factors studied were instrument gain setting, pulse repetition frequency (PRF), and carrier frequency. Sixteen regurgitant valves were examined with high quality commercial instrumentation from two manufacturers. Electrocardiographic-triggered image gating was used for recording and planimetry of maximal imaged flow area (IFA). Examinations were performed at two gain settings with constant carrier frequency and PRF, at three carrier frequencies (2.5, 3.5, and 5 MHz) at constant gain, and at differing PRF (3.0 to 12 kHz). Reduction in gain setting made little difference in asthetic quality of regurgitant jets, but their areas decreased by 29%. Carrier frequency was found to greatly affect IFA, with each higher carrier frequency giving significantly smaller IFAs. PRF also affected IFA consistently, with progressively smaller IFAs at each higher PRF. There was no useful correlation between IFA of a single jet evaluated on the two instruments at generally similar settings. It is concluded that instrument gain setting, PRF, and carrier frequency each significantly affects the size of IFA within a single instrument and between different instruments. Given the variety of instruments and settings employed within the cardiology community, it is unlikely that even moderately accurate grading of severity of regurgitation based on IFA can be done unless instrument settings are specified and standardized. There is a clear need for annotation of instrument settings during color Doppler examinations and a need for concensus regarding "optimal" settings. Finally, the consistency of reduction in IFA with increasing carrier frequency and PRF within each of the instruments tested suggests investigation of "normalization" of IFA displays.