Transcranial Doppler application for risk assessment of stroke in patients with mechanical mitral valve

Introduction: Observing microembolic signals in brain vessels by transcranial Doppler technology is a very common finding in patients with mechanical heart valve. These signals are almost always clinically asymptomatic. The aim of this study was assessment of transcranial Doppler in detecting probability of stroke in patients with mechanical heart valve. Methods: This descriptive study was carried out on 22 patients with St Jude prosthetic mitral valve, in 2005. Prevalence and frequency of microembolic signals were assessed during one hour and prothrombine time (PT) and International Normalized Ratio (INR) of patients were evaluated during middle cerebral artery monitoring. Correlation of cardioembolic stroke, severity of anticoagulant therapy and atrial fibrillation was considered with Mean Frequency Scale of Microembolic Signals (MFSMS). Data analysis was preformed by Mann-Whitny test and P<0.05 was considered statistically significant. Results: Microembolic signals were detected on vessel monitoring in 77% of cases. MFSMS in patients history of stroke was 14.25 after mitral valve replacement and was 11.23 in other patients which is not a meaningful difference. In cases with PT less than 22 seconds and INR more than 2.5, MFSMS of 6 and 16 patients were 12.92 and 10.97, respectively, which is not a significant difference. MFSMS in 13 patients with atrial fibrillation and 9 patients without atrial fibrillation were 11.88 and 10.94, which has no meaningful difference. Conclusion: The recorded microembolic signals in brain vessels of patients with mechanical heart valve are not fibrinous and the frequency of these signals does not indicate the risk of stroke in these patients. So, transcranial Doppler is of no clinical benefit in these patients and can not be a clue for severity of anticoagulant therapy