Evaluation of Cerebral Microembolic Signals in Patients with Mechanical Aortic Valves

Abstract

Background and Purpose: Microembolic Signals (MES) are frequently observed in Transcranial Doppler (TCD) recordings of patients with Mechanical Heart Valve (MHV).We hypothesized that number of MES produced by MHV could be reduced with oxygen inhalation, if gaseous bubbles are the underlying cause. Methods: All consecutive patients with St Jude aortic valves visiting the cardiology clinic were refered to the neurosonology unit, Valie Asr Hospital, Khorasan during August 2003 to August 2004. TCD monitoring of MES was performed with an ultrasound device (Vingmed 800 Oslo,Norway) and a 2 MHz probe. The MES counts were recorded during 30 minutes breathing room air and thereafter 30 minutes breathing through a facial mask with reservior bag (6 liter O2 per minute). The criteria of MES detection were characteristic chrip sound, unidirectional signal, random appearance within cardiac cycle and intensity increase 3dB above background. The MES counts in two periods of monitoring were compared with paired T test and significance was declared at P < 0.05. Results: Twelve patients (8 females and 4 males) were investigated. Oxygen ventilation caused a significant decrease of MES counts in the patients in comarison to breathing room air, P = 0.001. Thus MES in patients with MHV are mainly gaseous bubbles caused by blood agitation with MHV. Conclusion: The quantity of MES in patients with MHV is not related to the risk of thromboembolic complications in these patients.