Background: Detection of microemboli signals (MES) in patients with artificial heart valves has been extensively described, but the underlying material remains unclear. We assumed that the detection of MES in the jugular vein of patients with prosthetic valves would clearly argue for gaseous embolic material, since formed emboli are unable to cross through the capillaries.
Methods and results: Twenty-five patients with artificial heart valves, 15 patients with asymptomatic carotid artery disease, and 25 normal controls were examined. Monitoring was performed simultaneously over the dominant jugular vein and the ipsilateral middle cerebral artery for 30 min per subject, using 2-MHz transducers of a color duplex scanner for the jugular vein and a pulsed-wave Doppler for the middle cerebral artery. Data were harvested in an eight-channel digital recorder and MES counts evaluated by two separate observers. MES prevalence in the middle cerebral artery was 100, 13 and 0% in patients with artificial heart valves, asymptomatic carotid artery disease, and normal controls, respectively. No MES were detected in the jugular veins of patients with carotid artery disease or in normal controls, while their prevalence was 68% in patients with artificial heart valves. The interobserver agreement was satisfactory.
Conclusion: Our results suggest that the embolic material of at least a part of MES in patients with artificial heart valves is gaseous.