Microemboli in Cerebral Circulation and Alteration of Cognitive Abilities in Patients With Mechanical Prosthetic Heart Valves

Abstract

Background and Purpose-It has been shown previously that cerebral microemboli may occur frequently in patients with a normal mechanical heart valve (MHV) without prior history of stroke. Some arguments strongly suggest that these microemboli have a gaseous origin. In other circumstances such as extracorporeal circulation or decompression in divers, it has been demonstrated that cerebral microbubbles could lead to some deterioration in cognitive functions. Therefore, we have studied attention and memory, which are among the most impaired cognitive functions as demonstrated in previous studies, in patients with an MHV. Methods-Three groups of 12 volunteers each were composed of patients with an MHV and embolic signals in the cerebral circulation (group 1), patients with biological prostheses (group 2), and healthy subjects (group 3). Groups were carefully matched for age and verbal intellectual abilities. For each group, a transcranial Doppler examination was performed and a set of cognitive tests assessing sustained and selective attention and episodic and working memory was administered. Results-The mean embolic rate was 29 per hour in patients with an MHV. No embolus was detected in the other 2 groups.Episodic memory was significantly modified in both groups 1 and 2 compared with the control group for tasks that required high-processing resources. Working memory performance was significantly decreased in MHV patients. No between-groups differences were observed for the other parameters. Conclusions-Alteration of episodic memory can be attributed to a long-term effect of the surgical procedure.Deterioration of working memory can be related to the presence of cerebral microemboli in MHV patients. (Stroke. 1998;29:1821-1826.)

Microbubble moving in blood flow in microchannels: effect on the cell-free layer and cell local concentration

“…Bubbles from exogenous origin include bubbles resulting from medical proceedings such as surgeries (Borger et al 2001, Abu-Omar et al 2004, hemodialysis (Bischel et al 1975) and gas embolotherapy (Samuel et al 2012). Bubbles from endogenous origin comprise the formation of bubbles by cavitation in heart valves (Deklunder et al 1998, Milo et al 2003 and when pressure decreases abruptly in scuba diving (Papadopoulou et al 2013), astronaut extra vehicular activities (Karlsson et al 2009) or in high altitude flight (Foster and Butler 2009).…”

Absence of Circulating Microemboli in Patients with Atrial Fibrillation Undergoing Electric Cardioversion

“…During recent years, it has been recognized that circulating microemboli (ME) are noninvasively detectable as high-intensity transient signals by transcranial Doppler (TCD) sonography [19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36]. ME have been reported in various patient groups suffering from or at high risk of embolic stroke [19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29].…”

“…ME have been reported in various patient groups suffering from or at high risk of embolic stroke [19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]. Experimental studies using flow phantoms have validated that these high-intensity TCD signals reflect cerebral circulating ME too small to themselves illicit clinical symptoms [30, 31, 32].…”

Occurrence and Clinical Impact of Microembolic Signals During or After Cardiosurgical Procedures

“…5 In other studies, impaired working memory could be demonstrated in patients having received MHVs, presumably caused by continuous "showers" of cerebral microembolism. 27,28 Also, increased levels of platelet-derived microparticles, an increased procoagulant activity, and an increased rate of MESs were found in MHV carriers symptomatic with cerebrovascular events. 29 In 30 patients with bileaflet valves, a reduction of MESs by 16% to 41% after administration of acetylsalicylic acid of 81 to 531 MESs/h was demonstrated.…”