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

Abstract

Background and Purpose-Microembolic signals (MESs) are detectable within the transcranial Doppler frequency spectrum downstream from vascular atherothrombotic or cardiothrombotic lesions. A frequent occurrence of MESs has also been shown during bypass surgery or after mechanical valve implantation. We sought to compile the knowledge on MES prevalence, the clinical impact of these cardiogenic MESs, and microemboli composition. Summary of Review-We performed a systematic MEDLINE search and summarized the currently available literature about MESs during or after cardiosurgical procedures for this state-of-the-art report. Conclusions-The nature of cardiogenic MESs is heterogeneous, and their prevalence is highly variable, reflecting their different origin from a broad spectrum of cardiosurgical conditions. The occurrence and number of MESs during cardiac catheterization and percutaneous coronary angioplasty seem to have a clinical impact but need to be explored further.In patients with prosthetic heart valves, in those with left ventricular assist devices, and during cardiac surgery, the occurrence of MESs has an important clinical impact, and MES monitoring has proven its reliability.

Cerebral Embolism Following Transcatheter Aortic Valve Implantation

“…These results provide important novel insight into the mechanisms of CE associated with TAVI and support the need for further research to both reduce the incidence of CE during these procedures and better determine their clinical relevance. (J Am Coll Cardiol 2011;57: [18][19][20][21][22][23][24][25][26][27][28] …”

Microembolic signals in systemic lupus erythematosus and other cerebral small vessel diseases

“…We used the terms, ''microemboli'', ''microembolic signals'', ''cerebral microemboli'', ''High Intensity Transient Signals''; those manuscripts with extensive bibliographic information were selected to look for further papers related to the topic. We focused on papers reporting MES in non-cardiovascular diseases after exclusion of aortic, carotid, and cerebral atheromatous disease, dissection and endarterectomy; cardiac diseases and procedures, including patent foramen ovale, prosthetic heart valves, ventricular assist devices, cardiopulmonary bypass, coronary angiography or stent placement, for which comprehensive reviews have been published recently [14,36]. In this review, for each pathological condition, we give a brief introduction supporting the argument to look for MES, we state the postulated role of MES in the pathogenesis of each disorder and possible developments in the research field.…”

Cerebral Emboli Detected by Transcranial Doppler During Cardiopulmonary Bypass Are Not Correlated With Postoperative Cognitive Deficits

“…5,8,9,13 Some studies have found that patients undergoing CABG with higher HITS counts were more likely to experience cognitive deficits 1,2,5,6 or higher rates of frontal lobe dysfunction, 16 but others have found that there is no correlation between HITS counts and neurological symptoms or cognitive deficits. 6,8,17 Several methodological issues may account for the variability among these studies, including small sample sizes, 1,6 differences in intensity thresholds used to detect HITS, 13 artery location (carotid versus middle cerebral artery), 1,8,12 unilateral or bilateral recordings, 2,8,12 type of ultrasound device, 13,18 quality of TCD recordings, 18 inconsistency of signal reviewing techniques (automatic versus manual), 13,18 and the effects of several confounding variables such as the duration of CPB and core body temperature. 2 We sought to overcome these limitations by studying a large number of low-risk patients undergoing †HITS were recorded unilaterally in the left common carotid artery.…”

“…5 This technology detects cerebral emboli by the ultrasonic characteristics of the embolus-blood interface in the form of high-intensity transient signals (HITS). 5,6 Although a large number of HITS occur during CPB, there are no large studies confirming that these embolic signals are correlated with POCD.…”

“…[2][3][4] Solid emboli in particular are more likely associated with adverse neurological events such as stroke 7 and perhaps cognitive deficits. 2,4,8 Some studies 2,3,5,6 have suggested that during CPB, solid emboli are more frequently released during certain surgical maneuvers. If solid emboli represented by HITS are in fact associated with POCD, then this association would be best detected during such maneuvers.…”