Determinants of Micro-embolic Signals in Patients with Atherosclerotic Plaques of the Internal Carotid Artery

The Vulnerability of Vessels Involved in the Role of Embolism and Hypoperfusion in the Mechanisms of Ischemic Cerebrovascular Diseases

Accurate definition and better understanding of the mechanisms of stroke are crucial as this will guide the effective care and therapy. In this paper, we review the previous basic and clinical researches on the causes or mechanisms of ischemic cerebrovascular diseases (ICVD) and interpret the correlation between embolism and hypoperfusion based on vascular stenosis and arterial intimal lesions. It was suggested that if there is no embolus (dynamic or in situ emboli), there might be no cerebral infarction. Three kinds of different clinical outcomes of TIA were theoretically interpreted based on its mechanisms. We suppose that there is a correlation between embolism and hypoperfusion, and which mechanisms (hypoperfusion or hypoperfusion induced microemboli) playing the dominant role in each type of ICVD depends on the unique background of arterial intimal lesions (the vulnerability of vessels). That is to say, the vulnerability of vessels is involved in the role of embolism and hypoperfusion in the mechanisms of ischemic cerebrovascular diseases. This inference might enrich and provide better understandings for the underlying etiologies of ischemic cerebrovascular events.

Improving atherosclerosis risk assessment: looking beyond plaque accumulation to imaging of embolization and healing

Cerebrovascular and cardiovascular diseases constitute the most substantial disease burden worldwide and are only increasing in importance. Understanding how individuals with atherosclerosis may be better assessed for risk of stroke and myocardial infarction will have immense importance in deciding on therapeutic options. Carotid atherosclerosis is frequently portrayed as an orderly progression from asymptomatic plaque formation that enlarges with aging and culminates in either stable, calcified plaque or vulnerable, ruptured and inflamed plaque. New evidence suggests that atherosclerosis is better described as an equilibrium between synthetic and degradative processes. Putatively, plaques heal and decrease in size through processes such as efferocytosis in individuals unlikely to experience symptoms, whereas individuals who experience symptoms lack reparative mechanisms. Present clinically employed imaging strategies overlook plaque healing mechanisms. Other approaches that examine the downstream effects of plaque, rather than static plaque measurement, such as ultrasound emboli signal detection may address the gap between plaque that is vulnerable in appearance and that which is actually likely to cause symptoms. To ascertain the clinical risk of atherosclerosis optimally, both sides of the equation must be examined instead of relying on a unidirectional accumulative approach to atherosclerosis.

Silent cerebral events in asymptomatic carotid stenosis

BACKGROUND

Approximately 20% of strokes are attributable to carotid stenosis. However, the number of asymptomatic patients needed to prevent one stroke or death with endarterectomy is high at 17 to 32. There is a clear need to identify asymptomatic individuals at high risk of developing future ischemic events to improve the cost-effectiveness of surgery. Our aim was to examine the evidence for subclinical microembolization and silent brain infarction in the prediction of stroke in asymptomatic carotid stenosis using transcranial Doppler (TCD), computed tomography (CT), and magnetic resonance imaging (MRI).

METHODS

The review was conducted according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Articles regarding humans between 1966 and 2010 were identified through systematic searches of Pubmed, MEDLINE, and EMBASE electronic databases using a predetermined search algorithm.

RESULTS

Fifty-eight full text articles met the inclusion criteria. A median of 28% of microemboli positive patients experienced a stroke or transient ischemic attack during follow-up compared with 2% of microemboli negative patients (P = .001). The same was true for the end point of stroke alone with a median of 10% of microemboli positive patients experiencing a stroke vs 1% of microemboli negative patients (P = .004). A specific pattern of silent CT infarctions was related to future stroke risk (odds ratio [OR] = 4.6; confidence interval [CI] = 3.0-7.2; P < .0001). There are no prospective MRI studies linking silent infarction and stroke risk.

CONCLUSIONS

There is level 1 evidence for the use of TCD to detect microembolization as a risk stratification tool. However, this technique requires further investigation as a stroke prevention tool and would be complemented by improvements in carotid plaque imaging.

Comparison between transcranial Doppler and Coulter counter for detection of lipid micro embolization from mediastinal shed blood reinfusion during cardiac surgery

INTRODUCTION

Lipid micro embolization (LME) from re-transfused shed blood has been postulated to be a potential reason for short- and long-term cognitive dysfunction after cardiac surgery. The purpose of this investigation was to evaluate if transcranial Doppler (TCD) has the capacity to detect LME.

METHODS

Thirteen patients undergoing cardiopulmonary bypass surgery were investigated. Each patient's cerebral circulation was monitored with transcranial Doppler during the first two minutes after re-transfusion of shed blood and blood was simultaneously sampled and characterised by a Coulter counter.

RESULTS

Strong correlation was found between embolic loads, as measured by transcranial Doppler and Coulter counter (r=0.79, P<0.005).

CONCLUSIONS

This pilot study shows that non-invasive monitoring by transcranial Doppler could be a potential tool to monitor LME during cardiopulmonary bypass surgery.