Tricuspid regurgitation refers to a systolic leak of blood between the right ventricle and right atrium, across the tricuspid valve. Doppler echocardiographic examination of large numbers of normal individuals has shown that trivial tricuspid regurgitation is extremely common. Measurement of the peak velocity of the regurgitant frequency spectrum on Doppler echocardiography is of considerable clinical importance since it may be used to calculate peak right ventricular and, consequently, peak pulmonary systolic pressure. Doppler recording of the frequency spectrum of a tricuspid regurgitation jet optimally shows a smooth, parabolic, sharply demarcated envelope. In many individuals with trivial tricuspid regurgitation, however, this frequency spectrum is incomplete and its envelope is poorly demarcated. Such inadequate signals do not allow measurement of the spectrum's peak velocity. Like other contrast agents, air-filled microspheres composed of sonicated human serum albumin enhance reflection of Doppler ultrasound and thus have the potential to enhance incomplete tricuspid regurgitation spectra. Furthermore, since sonicated albumin microspheres can cross the pulmonary circulation intact, they have the potential to enhance mitral regurgitation spectra. The purpose of our study was to investigate whether injection of sonicated albumin microspheres enhances incomplete tricuspid and mitral regurgitation frequency spectra to a diagnostic quality. Sonicated albumin microsphere injection enhanced tricuspid regurgitation spectra to optimal quality in 11 of 15 patients (73%). Microsphere injection caused a minor degree of enhancement of the mitral regurgitant spectrum in 1 patient, but did not optimize the spectra in any of 10 patients tested. Saline contrast injection optimally enhanced tricuspid regurgitation spectra in all 8 patients in whom it was used.(ABSTRACT TRUNCATED AT 250 WORDS)