Transcranial Doppler "High Intensity Transient Signals" in the acute phase and long-term follow-up of mechanical heart valve implantation

Patients have a significant risk for suffering from stroke caused by cardiac emboli following prosthetic valve implantation. It is known that cerebral emboli present with "high intensity transient signals" (HITS) in transcranial Doppler (TCD) spectral curves. The purpose of this research was to look for possible HITS in the acute phase and long-term follow-up of mechanical heart valve implantation with TCD to correlate the number of HITS with clinical symptoms and to find parameters associated with an increase or decrease in HITS in patients with prosthetic heart valves. We examined the frequency of HITS after mechanical valve replacement with TCD in the left middle cerebral artery (MCA) for a period of 15 min. A total of 179 patients were investigated. One-hundred patients were examined at intervals between 1 and 33 days (Group 1) and 79 patients between 10 and 13 months (Group 2) after valve replacement. These data were correlated with neurological deficits and hematological parameters. In Group 1, at least one HITS could be detected by TCD in 65 patients (65%). There were no differences between sexes or in valve location, heart rhythm, and thromboplastin time between patients with and without HITS. The prevalence of HITS in valve types other than St. Jude and Medtronic Hall was significantly higher (p = 0.004). Ninety-three of the patients in Group 1 were neurologically asymptomatic; seven patients suffered from a hemispheric deficit after valve implantation. The neurologically symptomatic patients presented with a significantly higher HITS rate (10.9 ± 8.3; mean ± SD) than the neurologically asymptomatic patients (4.4 ± 12.3). One year after surgery (Group 2), the prevalence of HITS was 77%. The number of HITS in Group 2 was significantly higher than in Group 1 (p = 0.003). Following valve replacement, patients present with a high frequency of HITS. Symptomatic patients have a significantly higher rate of HITS than asymptomatic patients in the acute postoperative period. Thus, TCD examination may be used as an additional method to evaluate the individual risk for cerebral ischemia in the acute phase of heart valve implantation.