High-intensity Transient Signals Research Articles

Cerebral Embolization During Transcatheter Aortic Valve Implantation

The recent success of transcatheter aortic valve implantation (TAVI) has been associated with a heightened awareness of the potential risks, particularly stroke. Recent meta-analyses report 30-day stroke rates of 3% to 4%,1,2 and diffusion-weighted MRI studies have revealed new, clinically silent, cerebral lesions in 68% to 84% of patients undergoing TAVI.3–5 Although the majority of patients undergoing TAVI benefit greatly in terms of quality of life and functional status, concerns about neurological disability remain. Transcranial Doppler (TCD) has been extremely helpful in clarifying the central role of cerebral embolism as the major cause of intraprocedural stroke. As Kahlert et al4 report, cerebral microembolism occurs in essentially all patients undergoing TAVI. High-intensity transient signals, largely reflecting particulate emboli, are routinely detected during many invasive cardiac procedures. Nevertheless, it has been difficult to demonstrate that high-intensity transient signals correlate directly with stroke, and attempts to correlate high-intensity transient signals with biomarkers of neuronal injury have been inconsistent.3,6 Importantly, TCD has provided considerable information about the relative contributions of the various elements of the TAVI procedure to the risk of cerebral embolization. 1. Initial passage of wires and catheters into the ascending aorta. This seems relatively benign in the great majority of patients. 2. Crossing of the diseased native valve with a wire and diagnostic catheter carries a significant but modest risk of microembolic TCD signals and new MRI lesions.7 Unless necessary, crossing a diseased native valve should be avoided, and when necessary, crossing should be accomplished with as much care and skill as possible.4,7 3. Balloon valvuloplasty disrupts both the endothelial covering and underlying friable calcific material within the diseased valve. Disruption of the valve is progressive; least with balloon dilation, greater yet with repeated …

Cerebral Embolization During Transcatheter Aortic Valve Implantation

Background— Transcatheter aortic valve implantation (TAVI) is associated with a higher risk of neurological events for both the transfemoral and transapical approach than surgical valve replacement. Cerebral magnetic resonance imaging has revealed more new, albeit clinically silent lesions from procedural embolization, yet the main source and predominant procedural step of emboli remain unclear. Methods and Results— Eighty-three patients underwent transfemoral (Medtronic CoreValve [MCV TF ], n=32; Edwards Sapien [ES TF ], n=26) and transapical (ES TA : n=25) TAVI. Serial transcranial Doppler examinations before, during, and 3 months after TAVI were used to identify high-intensity transient signals (HITS) as a surrogate for microembolization. Procedural HITS were detected in all patients, predominantly during manipulation of the calcified aortic valve while stent valves were being positioned and implanted. The balloon-expandable ES prosthesis caused significantly more HITS (mean [95% CI]) during positioning (ES TF , 259.9 [184.8–334.9]; ES TA , 206.1[162.5–249.7]; MCV TF , 78.5 [25.3–131.6]; P <0.001) and the self-expandable MCV prosthesis during implantation (MCV TF , 397.1 [302.1–492.2]; ES TF , 88.2 [70.2–106.3]; ES TA , 110.7 [82.0–139.3]; P <0.001). Overall, there were no significant differences between transfemoral and transapical TAVI or between the MCV and ES prostheses. No HITS were detected at baseline or 3-month follow-up. There was 1 major procedural stroke that resulted in death and 1 minor procedural stroke with full recovery at 3-month follow-up in the MCV group. Conclusions— Procedural HITS were detected by transcranial Doppler in all patients. Although no difference was observed between the transfemoral and the transapical approach with the balloon-expandable ES stent valve, transfemoral TAVI with the self-expandable MCV prosthesis resulted in the greatest number of HITS, predominantly during implantation.

Direct transapical aortic valve implantation: a modified transcatheter approach avoiding balloon predilatation

Transcatheter aortic valve implantation (T-AVI) is an accepted alternative treatment option for patients with aortic stenosis seen inoperable or high risk for aortic valve (AV) replacement. However, a significant risk of stroke and cerebrovascular complications raises concern. Cerebral embolizations during T-AVI are frequent and recent data demonstrates that balloon aortic valvuloplasty during transcatheter procedures causes nearly as many high-intensity transient signals and microembolic signals as the deployment of the transcatheter heart valve itself. Omitting predilatation, therefore, may reduce the incidence of microembolizations and a possible stroke. We have developed a novel technique of 'Direct Transapical Aortic Valve Implantation', which enables surgeons to avoid predilatation of the native AV. So far, a total of six consecutive patients were treated using the Edwards SAPIEN XT™ transcatheter heart valve (Edwards Lifesciences, Irvine, CA, USA). Compared with conventional transapical implantations using the same device, procedure time was shorter, less contrast used and duration of fluoroscopy reduced. Procedural success was achieved in all patients, and all were discharged home without greater than or equal to moderate paravalvular leakage observed. Direct transapical implantation is technically safe and effective, with shorter radiation/procedure times. It is the next logical step in the direction of a full percutaneous transapical approach and potentially can result in reduced microembolizations.

Detection of coronary microembolization by Doppler ultrasound in patients with stable angina pectoris during percutaneous coronary interventions under an adjunctive antithrombotic therapy with abciximab: design and rationale of the High Intensity Transient Signals ReoPro (HITS-RP) study

BackgroundEmbolization of atherosclerotic debris from the rupture of a vulnerable atherosclerotic plaque occurs iatrogenically during percutaneous coronary interventions (PCI) and can induce myocardial necrosis. These microembolizations are detected as high intensity transient signals (HITS) using intracoronary Doppler technology.Presentation of the hypothesisIn the presented study we will test if abciximab (ReoPro®) infusion reduces high intensity transient signals in patients with stable angina pectoris undergoing PCI in comparison to standard therapy alone.Testing the hypothesisThe High Intensity Transient Signals ReoPro® (HITS-RP) study will enroll 60 patients. It is a prospective, single center, randomized, double-blinded, controlled trial. The study is designed to compare the efficacy of intravenous abciximab administration for reduction of microembolization during elective PCI. Patients will be randomized in a 1:1 fashion to abciximab or placebo infusion. The primary end point of the HITS-RP-Study is the number of HITS during PCI measured by intracoronary Doppler wire. Secondary endpoints are bleeding complications, elevation of cardiac biomarkers or ECG changes after percutaneous coronary interventions, changes in coronary flow velocity reserve, hs-CRP elevation, any major adverse cardio-vascular event during one month follow-up.Implications of the hypothesisThe HITS-RP-Study addresses important questions regarding the efficacy of intravenous abciximab administration in reducing microembolization and periprocedural complications in stable angina pectoris patients undergoing PCI.Trial registrationThe trial is registered under http://www.drks-neu.uniklinik-freiburg.de/drks_web/:DRKS00000603.

Effect of Embolic Particles During Coronary Interventional Procedures on Regional Wall Motion in Patients With Stable Angina Pectoris

Microembolization during percutaneous coronary intervention (PCI) causes minor myocardial injury, and a Doppler guidewire can detect embolic particles as high-intensity transient signals (HITS). The present study investigated the effect of microembolization during PCI on regional wall motion using a Doppler guidewire and myocardial strain analysis. We performed PCI to the left anterior descending coronary artery in 25 patients (18 men and 7 women, 68 ± 8 years old) with stable angina pectoris. Coronary flow spectrums were obtained with a Doppler guidewire to count the total number of HITS throughout the PCI procedures. On the days before and after PCI, we recorded echocardiography and measured the longitudinal peak systolic strain, peak strain rate, and early diastolic strain rate in the left anterior descending territory using a 2-dimensional speckle tracking method. PCI was successfully performed, and 10 ± 6 HITS (range 0 to 22, median 9) were recognized during PCI. The echocardiographic study showed no visible wall motion abnormalities in the left anterior descending territory either after or before PCI. In cases in which the total number of HITS was ≥10, the peak systolic strain, peak strain rate, and early diastolic strain rate worsened on the day after PCI compared with those on the day before PCI (p <0.01). The rates of change in peak systolic strain and early diastolic strain rate, defined as the ratios of those parameters after PCI to those before PCI, had modest to strong inverse correlations with the total number of HITS (R(2) = 0.35 and R(2) = 0.46, respectively). In conclusion, periprocedural microembolization during PCI reduces subclinical cardiac function in patients with stable angina pectoris.

Deep Echo Attenuation without Calcification Increases the Risk of Periprocedural Myonecrosis after Elective Percutaneous Coronary Intervention in Patients with Coronary Artery Disease

To investigate the clinical factors, including intravascular ultrasound (IVUS) findings, associated with percutaneous coronary intervention (PCI)-related periprocedural myonecrosis (PM) in patients with stable coronary artery disease (CAD). The study included 46 patients (mean age 65±2 y, 37 men) with stable CAD who underwent elective PCI using IVUS and a Doppler flow guidewire. In addition to routine IVUS measurements, the presence of deep echo attenuation (DEA) without calcification was assessed. The sum of all high-intensity transient signals (HITS) after a balloon deflation procedure was calculated using a Doppler flow guidewire. PM was defined as an elevation in troponin T to >0.03 ng/mL 24-hour after PCI. Patients were divided into 2 groups on the basis of the presence or absence of PM. PM was identified in 17 patients (37%). Estimated glomerular filtration ratio was lower in the PM group (p=0.021). Target vessel distribution was different between the groups (p=0.004). Positive remodeling and DEA, as observed on IVUS, were more common in the PM group (p=0.03 and p<0.0001, respectively). The total number of HITS was higher in the PM group (p=0.003). Logistic regression analysis demonstrated that the presence of DEA (p=0.003) was the sole factor associated with the occurrence of PM. These results demonstrated that DEA is an important factor associated with PM in patients who underwent an elective PCI. Therefore, IVUS to determine the presence of DEA should be performed before PCI.

Transcranial Doppler-detected cerebral embolic load during transcatheter aortic valve implantation

Transcatheter aortic valve implantation (TAVI) is an alternative to surgery for high-risk patients with severe aortic valve stenosis. Periprocedural stroke is reported at an incidence up to 10%. Magnetic resonance imaging studies have identified new onset of clinically silent ischaemic cerebral lesions more frequently (68-84%). So far, few data are available about cerebral embolism during TAVI. The aim of this study was to determine the frequency of high-intensity transient signals (HITS) and to explore differences in the HITS pattern between transfemoral and transapical access and between self-expanding (SE) and balloon-expandable (BE) deployment technique. Transcranial Doppler (TCD) ultrasound recordings of 44 patients undergoing TAVI (age 78 ± 6 years; logistic EuroSCORE 28 ± 15%; transfemoral access, n = 32; transapical access, n = 12; SE, n = 27; BE, n = 17) were analysed for HITS during the following intervals: (i) instrumentation prior to valvuloplasty, (ii) balloon valvuloplasty, (iii) prosthesis deployment (DP) and (iv) post-implantation (PI) including any re-dilatation episodes. The total procedural load of HITS and HITS frequency in procedural intervals were compared between different access routes and DP techniques. Periprocedural neurocognitive impairment was assessed clinically and by the confusion assessment method (CAM) prior to TAVI and on post-procedural days 1 and 4-6. TCD recordings demonstrated the occurrence of HITS in all patients. DP was associated with the highest load of HITS. Access route did not significantly influence the total burden of periprocedural HITS. During procedures using the SE type, a slightly larger total load of HITS was observed than with the BE type (P = 0.024). This was mainly due to more HITS during the DP (P = 0.027) and the PI interval (P = 0.002). No incidence of delirium was detected by CAM ratings. Two patients suffered a new onset of stroke within the 2 weeks following the procedure. In-hospital death and 30-day mortality were 0/44. HITS are observed during all procedural intervals in TAVI. The embolic events appear to peak during DP. In our series, the overall cerebral embolic load did not differ between the transfemoral and the transapical access route. TCD monitoring in TAVI is useful to identify periods and manipulations associated with an increased cerebral embolic load and may help to further enhance the safety of this procedure.

Predictability of Cerebral Embolization from Aortic Arch Manipulations During Thoracic Endovascular Repair

There is no sensitive tool to monitor embolic events and predict patients at a risk for strokes during thoracic endovascular aortic repair. We examined the relationship between the number of high intensity transient signals (HITS) by transcranial doppler ultrasound and the extent of atherosclerotic plaques in aortic arch. Thirteen patients were treated as a part of a single center United States Food and Drug Administration-approved investigational device exemption for various thoracic aortic pathologies. Bilateral transcranial doppler ultrasound transducers recorded the number of HITS. CT angiography and intravascular ultrasound were used to measure the thickness of mural thrombi and determine their arch location. All 13 patients had detectable HITS, and one patient sustained a stroke. Eleven patients had quantifiable mural thrombi. The highest HITS were observed in patients with thrombi in zones 2 to 3. All three patients with bovine arch had more HITS in the right middle cerebral artery whereas the patients with normal arch anatomy had more HITS in the left middle cerebral artery. The presence of mural thrombi in zones 2 and 3, irrespective of their thickness, was associated with increased HITS during thoracic endovascular aortic repair. This is the first study to characterize the significance of mural thrombi in aortic arch and their relationship to embolic events during aortic arch manipulations.

Cerebral Embolic Exposure During Transfemoral and Transapical Transcatheter Aortic Valve Replacement

To characterize the cerebral embolic exposure during transfemoral (TF) and transapical (TA) TAVR. To detect cerebral embolic events during TAVR, intraoperative neuromonitoring using transcranial Doppler (TCD) was utilized in 28 patients (Edwards SAPIEN valve TF n = 18, TA n = 10). High intensity transient signals (HITS) reflective of embolic events were recorded. The mean age was 83.4 ± 7.4 years. The Society of Thoracic Surgeons predicted risk of mortality score was 11.7 ± 2.9. The total number of HITS during TAVR was not significantly different between the TF and the TA groups, respectively (375 ± 301, 440 ± 283, p = 0.58). The highest number of HITS occurred during wire manipulation in the arch and valve insertion (TF, 80 ± 110, 107 ± 81; TA, 120 ± 80, 92 ± 80). In the TF group only, severe arch calcification was associated with significantly higher number of HITS both in total number of HITS (Grade I/II, 278 ± 71; Grade III/IV, 568 ± 479, p = 0.05) and during wire manipulation in the arch and valve insertion (Grade I/II, 140 ± 46, Grade III/IV 294 ± 239, p = 0.04). Highest cerebral embolic exposure occurred during wire manipulation in the arch and valve insertion in both the TF and TA groups. Arch calcification appears to be associated with increased embolic risk, specifically in the TF approach. Understanding of the mechanism of cerebral embolism is needed for future strategies of cerebral protection during TAVR.

Microemboli at the different stages of percutaneous transluminal carotid angioplasty and stenting in patients with post–carotid endarterectomy restenosis compared to primary stenosis

Microembolization to cerebral arteries during percutaneous transluminal carotid angioplasty (PTCA) and stenting is well described, as well as different mural pathology in primary versus post–carotid endarterectomy (CEA) restenosis lesions. The purpose of this study is to investigate possible different patterns of embolization in regards to number and distribution of microembolic signals (high-intensity transient signals (HITS)) in patients with primary carotid stenosis and restenosis after CEA. We used transcranial Doppler (TCD) to monitor the ipsilateral middle cerebral artery (MCA) of 13 patients (13 procedures) with restenosis after CEA and six patients (seven procedures) with primary stenosis of the internal carotid artery (ICA) during PTCA and stenting. All the procedures were performed without protection devices. The total number of HITS recorded in all patients was 2692, including 1563 microemboli in patients with restenosis and 1129 in patients with primary stenosis. The mean number of microemboli per procedure was 120.2 ± 65 and 161.3 ± 70 (p = 0.05) respectively. The average number of microembolic signals during the various stages of PTCA and stenting in the two groups was as follows: 1. Crossing the stenotic region with the guidewire and positioning the balloon inside the stenosis 33 ± 6.9 and 73.4 ± 9.4 (restenosis patients versus primary–stenosis patients, respectively, (p = 0.011); 2. angioplasty, balloon inflation and deflation, 19.l ± 6.9 and 38.9 ± 9.4 (restenosis versus primary lesions, respectively, p = 0.09); 3. stent deployment, 39.5 ± 6.9 and 27.3 ± 9.4 (restenosis versus primary lesions, respectively, p = 0.3); and 4. Post-stent dilatation, 29 ± 6.9 and 21.7 ± 9.4 (restenosis versus primary lesions, respectively, p = 0.53). Microembolic signals are detected through all stages of PTCA and stenting in patients with primary or post-CEA-restenosis lesions. The number of HITS was significantly higher in patients with primary stenosis than with restenosis of ICA in stages prior to stenting. This probably stems from the difference in pathomorphologic structure between the lesions. There was no significant difference between groups during stent deployment and post-stent dilatation. The clinical significance of the phenomenon of microembolism during carotid stenting is still not clear, but our results suggest the importance of using protection devices to reduce the incidence of these events in both primary and post-CEA lesions.

Transcranial Doppler Sound Detection of Cerebral Microembolism during Transapical Aortic Valve Implantation

Transapical aortic valve implantation (TAVI) is a new method that might reduce the surgical risk of conventional surgical aortic valve replacement in very high-risk patients. Increased downstream microembolization is expected in transapical aortic valve implantation. However, whether it usually occurs, how often, and its clinical relevance are not known. We report the results of ultrasound microembolic signal detection in the middle cerebral artery during the procedure. Fifty patients (mean age: 80 ± 5 years; mean EuroSCORE: 36 ± 13 %) underwent transapical aortic valve implantation. Intraoperative transcranial Doppler (TCD) sound examination of both middle cerebral arteries (MCA) was used to identify high-intensity transient signals (HITS) and microembolic signals (MES) during seven phases of the procedure. Pre- and postoperative computed tomography of the brain and clinical neurological examinations were performed preoperatively and daily during the first postoperative week. During the procedure, HITS [right MCA: 435 ± 922 (range 9-5765); left MCA: 471 ± 996 (range 24-6432)] and MES [right MCA: 78 ± 172 (range 1-955); left MCA: 62 ± 190 (range 2-1553)] were detected in all patients. Most of the MES were recorded during valvuloplasty [right MCA: 3 ± 5.6 (range 0-31); left MCA: 2 ± 4.9 (range 0-30)] and positioning of the prosthetic valve in the aortic position [right MCA: 6 ± 5 (range 0-22); left MCA: 2 ± 6.9 (range 0-38)]. Postoperatively, there were no clinical signs of new cerebral embolism. Cerebral microemboli were detected by intraoperative transcranial Doppler sound examinations in all patients during transapical aortic valve implantation. Most of the signals were detected during balloon valvuloplasty and delivery of the prosthetic valve.

Antithrombin-heparin covalent complex reduces microemboli during cardiopulmonary bypass in a pig model

AbstractTranscranial Doppler-detected high-intensity transient signals (HITS) during cardiopulmonary bypass (CPB) surgery have been associated with postoperative neurocognitive dysfunction, suggesting microemboli in the brain could be a contributing factor. HITS occur despite administration of unfractionated heparin (UFH). This study was done to determine whether antithrombin-heparin covalent complex (ATH), a more potent anticoagulant than heparin, can reduce HITS during CPB. In a pig CPB model, ATH, UFH, or UFH + antithrombin (AT) was intravenously administered to female Yorkshire pigs after sternotomy. Twenty minutes later, hypothermic CPB was initiated and continued for 1.25 hours, then normothermia was re-established for 45 minutes. Protamine sulfate was given to neutralize the anticoagulants, and pigs were allowed to recover. HITS were monitored using an arterial flow probe placed over the carotid artery. Compared with UFH (300 or 1000 U/kg), ATH reduced the number of HITS during CPB in a dose-dependent manner. AT (3 mg/kg) + UFH (300 U/kg) resulted in an intermediate HITS rate between UFH and ATH (2 mg/kg in terms of AT). Examination of brain sections for emboli formation confirmed that, similar to HITS, number of thrombi decreased in direct proportion to ATH dosage. These results support the hypotheses that the majority of HITS represent thromboemboli and that ATH reduces emboli formation during CPB.

Carotid Duplex Imaging on a Patient with a Temporary Left Ventricular Assist Device

Introduction In a carotid Duplex scan, the spectral Doppler examination is used to quantify stenosis by using the peak systolic and end diastolic velocities and ratios of the systolic velocities. The carotid spectral waveform is markedly different when a patient has a temporary left ventricular assist device (LVAD) that is nonpulsatile or continuous because of the oxygenated blood being redirected from the left atrium into the femoral artery via a centrifugal pump. This continuous-flow device provides complete circulatory support, preserving organ function and allowing quick restoration of hemodynamic stability. Case Report A 23-year-old man with idiopathic dilated cardiomyopathy, end-stage congestive heart failure, and cardiogenic shock required emergent placement of a TandemHeart temporary LVAD. Carotid Duplex imaging was performed the next day as a routine examination ordered for preheart transplant evaluation. No atherosclerotic disease was noted on B-mode images; however, intermittent bubbles were visualized and appeared as high-intensity transient signals within the Doppler spectral waveform. Flow was continuous in the carotid and vertebral arteries bilaterally. Discussion Percutaneous LVAD devices are increasingly being used as a short-term “bridge to cardiac transplantation.” Vascular sonographers should be aware that peripheral arterial flow will be nonpulsatile in patients who are sustained on these continuous flow devices. If significant disease is present we will need to rely on B-mode and color images and calculation of percent area or diameter reduction instead of waveform and velocity data.

Doppler Ultrasonography-Aided Early Diagnosis of Venous Thromboembolism after Total Knee Arthroplasty

Objectives Postoperative deep venous thrombosis (DVT) is usually asymptomatic but can result in a fatal pulmonary embolism (PE). To assess the ability of transcranial Doppler (TCD) ultrasound apparatus to detect venous emboli in patients who had undergone total knee arthroplasty (TKA). Methods Forty-eight patients undergoing TKA were examined postoperatively by using compression ultrasonography, computed tomographic angiography, and TCD ultrasonography that detected high-intensity transient signals (HITS) in femoral veins. An original scoring system based on both the number of HITS and the locations of DVT was tested for its accuracy in predicting PE development. Results Twenty-three of the 48 patients had DVT postoperatively, and 8 had an asymptomatic PE. The sensitivity and specificity of the HITS assessment alone in identifying PE development were 75% and 92.5%, respectively. The scoring system, however, had a sensitivity of 100% and a specificity of 85% and the area under the receiver operating characteristic (ROC) curve (AUC) was 0.96. Conclusions Application of a scoring system based on the detection of both DVT and HITS may be an effective and efficient method of screening for PE after knee arthroplasty.

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

High-intensity transient signals (HITS) are the transcranial Doppler representation of both air and solid cerebral emboli. We studied the frequency of HITS associated with different surgical maneuvers during cardiopulmonary bypass for coronary artery bypass graft surgery and their association with postoperative cognitive dysfunction (POCD). We combined 356 patients undergoing coronary artery bypass graft from 2 clinical trials who had both neuropsychological testing (before, 1 week and 3 months after surgery) and transcranial Doppler during cardiopulmonary bypass. HITS were grouped into periods that included: cannulation, cardiopulmonary bypass onset, aortic crossclamp-on, aortic crossclamp-off, side clamp-on, side clamp-off, and decannulation. POCD was defined by a decreased combined Z-score of at least 2.0 or reduction in Z-scores of at least 2.0 in 20% of the individual tests. Incidence of POCD was 47.3% and 6.3% at 1 week and 3 months after surgery. There was no association between cardiopulmonary bypass counts of HITS and POCD at 1 week (P=0.617) and 3 months (P=0.110). No differences in HITS counts were identified at any of the surgical periods between patients with and without POCD. Factors affecting HITS counts were surgical period (P<0.0001), blood flow velocity (P=0.012), cardiopulmonary bypass duration (P=0.040), and clinical study (P=0.048). Although cerebral microemboli have been implicated in the pathogenesis of POCD, in this study that included low-risk patients undergoing coronary artery bypass surgery, there was no demonstrable correlation between the counts of HITS and POCD.

Discrimination of Types of Venous Emboli Using Doppler Ultrasound

Many studies have identified features of the emboli traveling in the arterial system by Doppler ultrasound, and estimated their composition and size for anticipation of cerebral infarct. Another concern is features of the emboli in the venous system for anticipation of pulmonary embolism (PE). The objective is to prove that the emboli in the venous system can be discriminated by Doppler ultrasound in animal study and to assess whether PE can be predicted by using this technique in clinical case. Animal study--lard oil, thrombus, or bone marrow was injected to the femoral veins in pigs. High intensity transient signals were transhepatically identified at the inferior vena cava using Doppler ultrasound. Intensity volume (dB) and frequency shift (Hz) of each signal were obtained. The cutoff values at which thrombi, fat emboli, and marrow emboli could be discriminated were calculated by receiver-operating characteristic curves analysis. Human study--Subjects were 47 patients who underwent total knee arthroplasty. On postoperative day 0 and 1, High intensity transient signals were identified at the affected common femoral vein using Doppler ultrasound. Contrast computed tomography was done, and the patients were divided into two groups according to the presence of PE. The two groups were distinguished by intensity volume (dB) and frequency shift (Hz) of each signal and calculated the sensitivity and specificity. The statistics analysis was done as in animal study. Animal study--Thrombus and bone marrow could be discriminated from lard oil well at frequency shift of 208 Hz and 196 Hz (with sensitivity of 86.9, 85.7%, and specificity of 82.3%, 91.8%, respectively). Human study--The sensitivity and specificity were 76.7 and 75.0% to discriminate patients with and without PE at frequency shift of 208 Hz. Our animal study results indicated that emboli could be identified and discriminated in the venous system. Clinical study informed that the frequency shift (208 Hz) of the Doppler signal was the best parameter to discriminate PE with and without PE in patients with total knee arthroplasty.

AS-11: Detection of Emboli by Doppler Guidewire Can Reveal the Efficacy of a Distal Protection Devise in Infarct Size of Acute Myocardial Infarction

We recently reported that the Doppler guidewire (DGW) can detect emboli as high-intensity transient signals (HITS), and the number of HITS during PCI was associated with poor recovery of left ventricular function in AMI. In the current study, we revealed the efficacy of FILTRAP during PCI by using DGW in AMI.

High-intensity transient signals during laparoscopic surgery in children

Laparoscopic interventions in children gain increasing popularity. Pneumoperitoneum as applied during laparoscopic surgery can induce gas emboli formation, but it is unclear whether this is associated with cerebral embolic events. To investigate the hypothesis that pneumoperitoneum causes cerebral emboli in children, the number and intensity of high-intensity transient signals (HITS) detected using transcranial Doppler ultrasonography were assessed before and after induction of pneumoperitoneum. Twenty children were monitored during laparoscopic surgery. General anaesthesia was performed using sevoflurane and sufentanil or alfentanil. Pressure-controlled ventilation was adapted to maintain end-tidal Pco(2) (Pe'(co(2))) between 4.7 and 6.0 kPa. Baseline measurement of HITS rate, cerebral blood flow velocity, and mean arterial pressure (MAP) were recorded during steady-state anaesthesia before skin incision and during pneumoperitoneum with intra-abdominal pressure of 1.6-2.0 kPa applied using CO(2). In 14 children (70%), HITS were detected during baseline and pneumoperitoneum. Three additional children (15%) developed HITS during pneumoperitoneum only and another three children (15%) presented no HITS during the investigation period. MAP and cerebral blood flow velocity increased with pneumoperitoneum. HITS are present in 70% of paediatric surgical patients under balanced anaesthesia before surgical interventions. Pneumoperitoneum further increased the occurrence of HITS.

Filter-Protected versus Unprotected Carotid Artery Stenting: A Randomised Trial

Background: Our aim was to determine whether filter protection reduces embolisation to the brain during carotid artery stenting (CAS). Methods: Thirty patients with symptomatic carotid artery stenosis ≧70% (North American Symptomatic Carotid Endarterectomy Trial) were randomly assigned to filter-protected or unprotected CAS. Diffusion-weighted magnetic resonance imaging (DWI) of the brain was performed before and at 3 time points after CAS. In a subset of patients, high-intensity transient signals on transcranial Doppler (TCD) were recorded with categorisation of emboli. Data were independently reviewed off-site. Results: There were no significant differences in mean age, proportion of octogenarians or presenting symptoms between the groups. On procedural DWI (1–3 and 24 h after stenting), there were 7/24 (29%) and 4/22 (18%) new lesions in protected and unprotected patients respectively (p = 0.38). At 30 days there were 9/33 (26%) and 4/33 (12%) lesions in protected and unprotected patients, respectively (p = 0.1). On TCD there were significantly more signals in total as well as particulate emboli during filter-protected CAS (426.5 and 251.3) than during unprotected CAS (165.2 and 92) – p = 0.01 and 0.03, respectively. Conclusions: Filter-protected CAS is associated with an increase in new lesions on DWI and significantly higher rates of total and particulate microembolisation on TCD than unprotected CAS. The clinical significance of these findings requires further study.

Cerebral Emboli Generation during Off-Pump Coronary Artery Bypass Grafting with a Clampless Device versus Partial Clamping of the Ascending Aorta

: It is not known whether use of a clampless facilitating device during proximal graft anastamosis decreases intraoperative cerebral emboli in patients with mild atherosclerotic ascending aorta (AAA) having off-pump coronary artery bypass. : After intraoperative epiaortic ultrasound showed no more than mild (grade I-II) atherosclerotic ascending aorta, 20 patients were randomized to receive either partial clamping (PC, n = 10) or the HEARTSTRING clampless device (HS, n = 9) for proximal graft construction on the ascending aorta. Continuous transcranial Doppler monitoring, with capability to discern gaseous from solid particulates, was used intraoperatively to monitor high-intensity transient signals (HITS) in the middle cerebral arteries. Postoperative diffusion-weighted brain magnetic resonance imaging documented old and new ischemic brain lesions. : There were no significant differences between the groups in the number of proximals (P = 0.14), distals (P = 0.4), or intraoperative cell saver transfusions (P = 0.69). The total number of HITS was not significantly different between the PC and HS groups (P = 0.2). However, the number of solid HITS was significantly lower in the HS than in the PC group (2.7 ± 2.6 versus 14.0 ± 8.1; P < 0.001). The number of gaseous emboli in the HS group was fourfold greater when a mister-blower rather than a suction device was used to clear blood away from the HS site. Postoperatively, there were no deaths, myocardial infarctions, or clinical strokes observed in either group. Diffusion-weighted cerebral magnetic resonance imaging revealed no statistical difference between groups for new infarct lesions. : Use of the HS device during off-pump coronary artery bypass was associated with significantly fewer intraoperative solid emboli in the middle cerebral artery than PC of the ascending aorta.