O53	TCD Monitoring During Invasive Cardiovascular Examinations and Surgery D. Russell, University of Oslo, Norway Transcranial Doppler is a very good method for monitoring cerebral hemodynamics during invasive cardiovascular examinations and operations. It is safe, non-invasive and provides immediate beat-to-beat information regarding cerebral embolization and changes in blood flow velocities in the major intracranial arteries. Cerebral microemboli are frequently detected using TCD during cerebral and coronary intra-arterial angiographies. They often occur during flushing and contrast injection when it is assumed that they are gas bubbles. However, they may also be due to loosening of atheromatous material from the arterial wall or thrombus formation on the tip of the catheter. There is evidence which suggests that asymptomatic cerebral lesions due to embolization may be relatively common. Diffusion MRI examinations have shown signs of an embolic pattern of ischemic lesions in the distal vascular territory of small cortical, subcortical or perforating vessels in over 20% of patients following intra-arterial angiographies of the cerebral vessels. During carotid endarterectomy hemodynamic information obtained using TCD monitoring has been shown to result in a decreased risk for both clinical and MRI signs of cerebral injury. TCD monitoring has shown frequent cerebral microembolization during cardiopulmonary by-pass surgery. Their numbers are higher during valve replacement when effective heart ejection is regained and in coronary artery by-pass patients during manipulation of the aorta. There is some evidence which suggests that microembolization to the brain may be a main cause of post-operative cognitive impairment which is found in up to 50% of patients 6 weeks post-operatively. TCD studies carried out during "off-pump" coronary artery by-pass surgery have shown that there are considerably less cerebral microembolization to the brain when operating on the beating heart compared to cardiopulmonary by-pass. However, the risk of cardiac arrhythmias and cerebral perfusion pressure changes may be more frequent during "off-pump" surgery where there is more mechanical manipulation of the heart.
O54	Prevention of stroke by TCD in carotid surgery and stenting. R.G.A. Ackerstaff, on behalf of the Antonius Carotid Endarterectomy, Angioplasty and Stenting Study Group Background: Carotid angioplasty and stenting (CAS) is being assessed as an alternative procedure to CEA. The advantages of CAS over CEA include a shorter hospital stay, avoidance of general anaesthesia and an incision in the neck, and an ability to dilate surgically inaccessible lesions such as high internal carotid artery stenoses. On the contrary, CAS has been criticised on the grounds that the risk of cerebral embolism during the procedure may be similar to or even greater than the risk with CEA. However, the incidence of asymptomatic embolisation may be higher than in CEA. No prospective studies have been published so far on the risks of both clinically symptomatic and asymptomatic cerebral embolism during CAS. At present, two studies are in preparation and, hopefully, will be published soon. Material, Methods and Results: Here we only give a brief review of the clinical outcome, the TCD detected cerebral embolic load, and the impact of these emboli on brain function and architecture assessed by MRI. The primary end-points for these studies were the occurrence of any ipsilateral or contralateral stroke and periprocedure death. There were a number of secondary end-points, including transient cerebral and retinal deficits, number of TCD detected emboli, number of new lesions on brain MRI, and patency of the treated artery. So far, 297 patients with a mean age of 70 years were enrolled. During all procedures the patient was clinically monitored by a neurologist in the X-ray room. Moreover, the neurological integrity of the patients was also evaluated after the procedure. TCD monitoring of the MCA blood flow velocities on the side of stenting was technically possible in 89% of the patients, and in 72 patients a MRI of the brain was done before and after the intervention. The combined minor and major stroke and death rate was 3.7%. Regarding clinically relevant cerebral embolism, the most critical stage was postdilatation after stent deployment. Particulate macroembolism and massive air embolism also showed a significant association with adverse outcome. With respect to brain structure, in 61 patients the MRI did not show any change. In the remaining 11 patients (15%) of the MRI part of the study, 19 new lesions were noticed. In 6 patients, these new lesions were clinically silent. Conclusion: If made audible in the operating theatre the sensitivity of TCD ultrasonography for the detection of cerebral microemboli during CEA in real-time provides unique information to the surgeon. Our preliminary results suggest that CAS of the carotid bifurcation is a feasible alternative to CEA. Nevertheless, it results in a significant higher cerebral embolic load. The most obvious risks are embolic stroke from plaque disruption during postdilatation after stent deployment and particulate macroembolism. Further devices (protection balloons, filters, and traps) are being developed to be placed in the distal internal carotid artery or proximally in the external and common carotid arteries before angioplasty and stent placement. Our study suggests that the pore size of such filters should be designed not only to prevent macroembolism but also microembolism that is related both to the risk of stroke and small, clinically silent lesions of the brain.
O55	A LOGARITHMIC SCALE FOR GRADING RIGHT-TO-LEFT CONDUCTANCE OF CARDIOPULMONARY SHUNTS (RLS) USING TRANSCRANIAL POWER M-MODE DOPPLER (PMD) Merrill P. Spencer, Spencer Vascular, Seattle, WA USA Background: An expanded grading scale for patent foramen ovale (PFO), which includes both size and shunt flow, is needed to determine the probability of paradoxical embolism and to evaluate PFO closure. Methods: Using embolic tracks (ET) produced on PMD displays, we designed a 6 level log scale of ET counts. Bilateral transtemporal insonation included the MCAs, ACAs and other arteries along the beam pathways. Following I.V. injection of saline/bubbles ET counts were categorized as 0, 1-10, 11-30. 31-100, 101-300, and >300 designated conductance grades 0, 1, 2, 3, 4, and 5 indicating the relative capability of a RLS to conduct emboli from the venous to the cerebral circulations. Conductance was determined during normal respiration and following a 10-second respiratory strain calibrated by blowing against a pressure gauge to 40mm Hg (simulated Valsalva). Results: Among 119 consecutive patients successfully tested for RLS the resting conductance was distributed as follows: 0- 61%, 1– 18%, 2– 9%, 3- 7.6%, 4– 4.2%, and 5– 0.08%. The straining conductance distribution was: 0- 41%, 1- 16%, 2- 8.6%, 3- 9.5%, 4- 15%, and 5- 11%. Among 11 patients, tested before and 23 to 44 days after percutaneous closure 4 were completely closed, 5 were reduced by 1 to 4 grades (avg. 2.8), and 2 persisted with the same grades 2 and 4. Conclusions: A 6-grade log scale for cardiopullmonary shunt conductance of emboli provides greater resolution, and improves evaluation of closure results. Power m-mode improves recognition of emboli by means of the definitve embolic tracks.
O56	CONTRAST TCD FOR CEREBRAL ISCHEMIA OF UNKNOWN ETIOLOGY: PRELIMINARY RESULTS A.Y. Razumovsky, A. E. Hillis, E. M. Aldrich, M. L. Torbey, W. C. Ziai, R. J. Wityk The Johns Hopkins Medical Institutions, Baltimore, MD, USA Background. Contrast transcranial Doppler ultrasonography (c-TCD) has been proposed as an alternative method for the detection of PFO. However, data regarding quantitative characteristics of emboli during c-TCD are sparse. This retrospective study was undertaken to compare the diagnostic yield of c-TEE with that of c-TCD in the detection of a PFO as a cardiac source of embolism and to define emboli patterns in patients undergoing c-TCD. Material and Methods. Over a 3-year period, c-TCD was requested for 114 patients (53 female, mean age 48.9 + 15.3 years). All patients underwent an extensive stroke work up, including c-TEE. A four-level classification was accepted according to emboli appearance: Class I: No emboli, Class II: 1-10 emboli, Class III: >10 emboli, Class IV: shower of emboli [1]. No patients had complications associated with c-TCD test. For c-TCD we used unilateral monitoring of the right middle cerebral artery with 2-MHz probe (Intraview, RIMED, Israel). Results. 62 (54%) patients had emboli on TCD and TEE (Group 1). 19 patients (17%) had emboli in TCD study but no PFO on TEE (Group 2). 31 (27%) patients had no PFO on TEE and did not show emboli with TCD. Two patients (2%) had a PFO on TEE but failed to have emboli during c-TCD study. At rest majority of patients in Group 1 (n=32) and group 2 (n=9) had Class II emboli. There was no statistical difference for number of emboli in Class II between Group 1 and 2 at rest (4.2 +2.8 vs. 2.3 + 1.6) and with Valsalva maneuver (VM) (4.6 +3.1 vs. 3.6 + 3.5). 14 patients in Group 1 and 3 patients in Group 2 had Class III emboli at rest. Few patients in Class III had more than 20 emboli at rest or with VM. Group 1 had significantly higher number of patients (25 vs. 4) who had Class IV emboli at rest (7 vs. 1) or with VM (24 vs. 3). Conclusions. Based on our results, c-TEE may miss as many as 17% of positive cases. It may be cost effective to perform c-TCD as a routine diagnostic procedure in patients presenting with cerebral ischemic events of unknown etiology. The majority of patients had Class II emboli. Further study and clinical correlation are warranted. 1. Jauss et al. Cerebrovasc Dis 2000;10:490-495
O57	DETECTION OF CEREBRAL EMBOLIZATION AFTER ANGIOPLASTY PLUS STENTING S. Horner, E.Klein, G.Bone, D.Svetina, G.Pichler, T.Schober, K.Niederkorn. Karl Franzens University Graz, Austria Background: Cerebral embolization has been implicated in the possible etiology of neurological deficits after percutaneous transluminal angioplasty and stenting (Stent-PTA). In order to show any association, we prospectively obtained TCD monitoring and diffusion-weighted MRI (DWI) of the ipsilateral cerebral hemisphere before and after Stent-PTA of the extracranial brain arteries. Methods: 58 Stent-PTA`s were performed in 50 patients (mean age 68 ys). Neurological assessment, ipsilateral DWI and TCD monitoring (1 hour per vessel) were performed in 37 extracranial carotid-(n= 35) or vertebral (n=2) arteries one day before and after stenting. Results: Postprocedural neurological deficits were all reversible and occurred in 3 of these 37 (8.1%) Stent-PTA`s. Postprocedural embolic signals on TCD and/or new hyperintensities on DWI were visible in 12/37 (32.4%) patients (TCD only: 4, DWI only : 4, TCD+DWI: 4). Signs of cerebral embolism was present in all patients with neurological deficits (3/3, 100%) and in 9/34 (26.5%) asymptomatic patients. Conclusions: Although the occurrence of neurological deficits after Stent-PTA was highly associated with the presence of embolic lesions, the majority of patients with cerebral embolization was clinically asymptomatic. The presence of embolic signals was not a factor that predisposed a patient to neurological complications.
O58	Systematic review of transcranial Doppler after carotid endarterectomy J. Horn, R.G.A Ackerstaff on behalf of the PCSEM (Post Carotid Surgery Emboli Monitoring) Collaboration Background Patients with stenosis of the carotid artery can benefit from carotid endarterectomy (CEA). However, ischaemic complications occur during and shortly after CEA and are considered to be of thromboembolic origin. These embolisms can be monitored by transcranial Doppler (TCD). A correlation between the number of microembolic signals (MES), registered after CEA, and the risk of postoperative ischaemic stroke was suggested in some relatively small studies, in which the number of ischaemic cerebral complications was limited. By performing a systematic review of all available data on emboli monitoring after CEA, we investigated the relationship between MES after CEA and the risk of ischaemic cerebral complications. Methods Research groups, monitoring emboli post CEA, were identified by searching Medline (using the search terms: TCD, carotid endarterectomy and embolism), and asked to join this collaborative research project. Data collected: method of monitoring, patient characteristics, number of post CEA emboli, ischaemic cerebral events, and functional outcome. Analysis: Relationship between MES and postoperative cerebral ischaemic events. Results Eight centres monitoring emboli post CEA were identified (5 in Europe, 2 in the USA, 1 in Australia). All decided to cooperate, until now we received data of 667 patients, of whom 611 were monitored directly after surgery. Seven patients (1.1%) suffered an ischaemic cerebral complication. These seven patients showed statistically significant more MES during 60 min. monitoring (p = 0.002). Conclusion These data show a strong relationship between the number of MES directly post CEA and the occurrence of cerebral ischaemic complications. This knowledge may allow us to prevent post CEA strokes in the future.
O59	TRANSCRANIAL DOPPLER MONITORING DURING CAROTID SURGERY IN PATIENTS OPERATED UPON WITH SHUNT O. Martinelli, B. Gossetti, F.R. Fornasin, and F. Bendetti-Valentini 2nd Chair of Vascular Surgery-"La Sapienza" University of Rome (Italy) Background: The study of intracranial vessels by Transcranial Doppler (TCD) modified the approach in the diagnosis, surgical indications, intraoperative conduct and control of patients submitted to carotid repair. Method: During the last ten years 706 patients underwent to carotid reconstructive procedures under locoregional anesthesia (LA) and were investigated by TCD intraoperatively from the completion of LA till 30 minutes after the end of the surgical procedure; mean blood velocity (MBV) in ipsilateral middle cerebral artery (MCA) was monitored. A decrease of MBV below 75% of basal value during carotid clamping test was considered critical for hemispheric cerebral perfusion. In 80 (11.3%) patients a Pruitt-Inahara shunt was used based on a loss of consciousness and/or a decrease of MBV during carotid clamping test below 75% of basal value. TCD control of shunting allows to evaluate: 1) the regain of MBV after shunt insertion (shunt efficacy); 2) the malfunction of shunt during surgical procedures (signal in MCA disappeared or severely reduced); 3) in only 61 cases, the type and the number of HITS during shunting (introduction, function and extraction); 4) the correlation between TCD data and clinical events. Results: Pruitt-Inahara shunt increased MBV in MCA over 80% of basal value in all cases. Shunt malfunction was showed in 7 cases (8.7%) and promptly corrected without haemodynamic neurological deficit. MES were detected in 54 out of 61 cases and were judged bubbles in a great number of cases. No neurological deficit for embolic complication due to shunting occurred. Conclusion: TCD monitoring is an effective method to evaluate the function of shunt during carotid surgery.