EFFECT OF OXYGEN INHALATION ON MICROEMBOLIC SIGNALS IN PATIENTS WITH MECHANICAL AORTIC VALVE

Microembolic signals (mes) are frequently observed in transcranial doppler (tcd) recordings of patients with mechanical heart valve (mhv). if gaseous bubbles are the underlying cause, number of mes produced by mhv could be reduced with oxygen inhalation. from september 2003 to september 2004, a consecutive series of 14 patients with st jude aortic valve visited in the cardiology clinic were referred to neurosonology unit, valie asr hospital, khorasan. tcd monitoring of mes was performed with an ultrasound device 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 reservoir bag (6 liter o2 per minute). the criteria of mes detection were characteristic chirping 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. twelve patients (8 females and 4 males) were investigated. oxygen ventilation caused a significant decrease of mes counts in the patients in comparison to breathing room air (p = 0.001). it seems that mes in patients with mhv are mainly gaseous bubbles caused by blood agitation with mhv. the quantity of mes in patients with mhv is not related to the risk of thromboembolic complications in these patients.