Transcranial Doppler detection of microemboli in prosthetic heart valve patients: dependency upon valve type

Abstract

Transcranial Doppler ultrasound has revealed the existence ofcerebrovascular microemboli in asymptomatic patients with prosthetic heartvalves. We investigated the relation between the presence and number ofemboli signals and valve type. Patients with six types of prosthetic valves(Bjork-Shiley monostrut, Medtronic-Hall, Carbomedics, ATS,Carpentier-Edwards standard, Carpentier-Edwards supraannular) were examinedusing transcranial Doppler ultrasound in two centers. The monitoring timewas 30 min over the right middle cerebral artery. All patients werestabilized on warfarin at the time of study. Microemboli signals wereidentified by their characteristic audiovisual signal and on subsequentspectral analysis, based on accepted criteria. A standard neurologicquestionnaire was completed by all patients. The prevalence of microembolisignals varied between 49% (Medtronic Hall) and 97% (Bjork-Shileymonostrut), while their number varied between 1 [0-3] (Carpentier-Edwardsstandard) and 187 [136-240] (Bjork-Shiley monostrut) per hour (median and95% CI). Both parameters were significantly higher in patients withBjork-Shiley monostrut valves compared to the other patient groups. Therewere no significant differences in the prevalence of neurologiccomplications among the groups examined (overall 16%), or in emboli numbersbetween symptomatic and asymptomatic patients. The prevalence and quantityof microemboli signals in patients with prosthetic heart valves, asdetected by transcranial Doppler, is dependent upon valve type. Theclinical significance of these microemboli signals remains to be furtherevaluated.