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Transcranial Doppler detection of microemboli in prosthetic heart valve patients: dependency upon valve type
1Department of Medicine and Therapeutics, Western Infirmary, Glasgow, UK.
Insights
Prosthetic heart valve type influences the number of microemboli detected by transcranial Doppler ultrasound. The Björk-Shiley monostrut valve showed significantly higher microemboli prevalence and quantity compared to other types.
Area of Science:
- Neurology
- Cardiovascular Medicine
- Biomedical Engineering
Background:
- Asymptomatic patients with prosthetic heart valves can have cerebrovascular microemboli.
- Transcranial Doppler ultrasound (TCD) is a non-invasive tool for detecting these microemboli.
Purpose of the Study:
- To investigate the relationship between prosthetic heart valve type and the presence/number of microemboli signals.
- To compare microemboli detection across six different prosthetic heart valve types.
Main Methods:
- Utilized transcranial Doppler ultrasound over 30 minutes on the right middle cerebral artery in patients with six prosthetic valve types.
- Identified microemboli signals using audiovisual characteristics and spectral analysis.
- Collected data on neurologic complications via a standard questionnaire.
Main Results:
- Microemboli prevalence ranged from 49% (Medtronic-Hall) to 97% (Björk-Shiley monostrut).
- Microemboli numbers varied significantly, with Björk-Shiley monostrut valves showing the highest median count (187/hour).
- No significant differences in neurologic complications or emboli numbers between symptomatic and asymptomatic patients were found.
Conclusions:
- The prevalence and quantity of microemboli detected by TCD in prosthetic heart valve patients depend significantly on the specific valve type.
- Further research is needed to determine the clinical significance of these microemboli signals.
Abstract:
Transcranial Doppler ultrasound has revealed the existence of cerebrovascular microemboli in asymptomatic patients with prosthetic heart valves. We investigated the relation between the presence and number of emboli signals and valve type. Patients with six types of prosthetic valves (Björk-Shiley monostrut, Medtronic-Hall, Carbomedics, ATS, Carpentier-Edwards standard, Carpentier-Edwards supraannular) were examined using transcranial Doppler ultrasound in two centers. The monitoring time was 30 min over the right middle cerebral artery. All patients were stabilized on warfarin at the time of study. Microemboli signals were identified by their characteristic audiovisual signal and on subsequent spectral analysis, based on accepted criteria. A standard neurologic questionnaire was completed by all patients. The prevalence of microemboli signals varied between 49% (Medtronic Hall) and 97% (Björk-Shiley monostrut), while their number varied between 1 [0-3] (Carpentier-Edwards standard) and 187 [136-240] (Björk-Shiley monostrut) per hour (median and 95% CI). Both parameters were significantly higher in patients with Björk-Shiley monostrut valves compared to the other patient groups. There were no significant differences in the prevalence of neurologic complications among the groups examined (overall 16%), or in emboli numbers between symptomatic and asymptomatic patients. The prevalence and quantity of microemboli signals in patients with prosthetic heart valves, as detected by transcranial Doppler, is dependent upon valve type. The clinical significance of these microemboli signals remains to be further evaluated.