Prospective Evaluation of Frequency and Nature of Transcranial High-Intensity Doppler Signals in Prosthetic Valve Recipients Aldo Milano MD, Alessandro D'Alfonso MD, Riccardo Codecasa MD, Marco De Carlo MD, Carmela Nardi MD, Giovanni Orlandi MD, Lucilla Landucci MD, Uberto Bortolotti MD High-intensity transient signals (HITS) are observed with transcranial Doppler in asymptomatic patients with prosthetic heart valves. Correlation of the incidence and number of HITS with type of prosthesis, clinical status and other risk factors for thromboembolism was analyzed in 83 patients. A higher incidence of HITS was found in mechanical valve recipients when compared with patients receiving bioprostheses or undergoing mitral valve repair. Oxygen inhalation caused a significant decrease in the number of HITS per hour, supporting the proposed gaseous nature of the signals, and the validity of this test in helping to differentiate gaseous from solid microemboli.

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