Carotid Plaque Characteristics Predict Recurrent Ischemic Stroke and TIA: The PARISK (Plaque At RISK) Study.

BACKGROUND: Patients with symptomatic carotid stenosis are at high risk for recurrent stroke. The decision for carotid endarterectomy currently mainly relies on degree of stenosis (cutoff value >50% or 70%). Nevertheless, also, patients with mild-to-moderate stenosis still have a considerable recurrent stroke risk. Increasing evidence suggests that carotid plaque composition rather than degree of stenosis determines plaque vulnerability; however, it remains unclear whether this also provides additional information to improve clinical decision making. OBJECTIVES: The PARISK (Plaque At RISK) study aimed to improve the identification of patients at increased risk of recurrent ischemic stroke using multimodality carotid imaging. METHODS: The authors included 244 patients (71% men; mean age, 68 years) with a recent symptomatic mild-to-moderate carotid stenosis in a prospective multicenter cohort study. Magnetic resonance imaging (carotid and brain) and computed tomography angiography (carotid) were performed at baseline and after 2 years. The clinical endpoint was a recurrent ipsilateral ischemic stroke or transient ischemic attack (TIA). Cox proportional hazards models were used to assess whether intraplaque hemorrhage (IPH), ulceration, proportion of calcifications, and total plaque volume in ipsilateral carotid plaques were associated with the endpoint. Next, the authors investigated the predictive performance of these imaging biomarkers by adding these markers (separately and simultaneously) to the ECST (European Carotid Surgery Trial) risk score. RESULTS: During 5.1 years follow-up, 37 patients reached the clinical endpoint. IPH presence and total plaque volume were associated with recurrent ipsilateral ischemic stroke or TIA (HR: 2.12 [95% CI: 1.02-4.44] for IPH; HR: 1.07 [95% CI: 1.00-1.15] for total plaque volume per 100 µL increase). Ulcerations and proportion of calcifications were not statistically significant determinants. Addition of IPH and total plaque volume to the ECST risk score improved the model performance (C-statistics increased from 0.67 to 0.75-0.78). CONCLUSIONS: IPH and total plaque volume are independent risk factors for recurrent ipsilateral ischemic stroke or TIA in patients with mild-to-moderate carotid stenosis. These plaque characteristics improve current decision making. Validation studies to implement plaque characteristics in clinical scoring tools are needed. (PARISK: Validation of Imaging Techniques [PARISK]; NCT01208025).

Cardiometabolic risk factors as determinants of peripheral nerve function: the Maastricht Study.

AIMS/HYPOTHESIS: We aimed to examine associations of cardiometabolic risk factors, and (pre)diabetes, with (sensorimotor) peripheral nerve function. METHODS: In 2401 adults (aged 40-75 years) we previously determined fasting glucose, HbA1c, triacylglycerol, HDL- and LDL-cholesterol, inflammation, waist circumference, blood pressure, smoking, glucose metabolism status (by OGTT) and medication use. Using nerve conduction tests, we measured compound muscle action potential, sensory nerve action potential amplitudes and nerve conduction velocities (NCVs) of the peroneal, tibial and sural nerves. In addition, we measured vibration perception threshold (VPT) of the hallux and assessed neuropathic pain using the DN4 interview. We assessed cross-sectional associations of risk factors with nerve function (using linear regression) and neuropathic pain (using logistic regression). Associations were adjusted for potential confounders and for each other risk factor. Associations from linear regression were presented as standardised regression coefficients (ß) and 95% CIs in order to compare the magnitudes of observed associations between all risk factors and outcomes. RESULTS: Hyperglycaemia (fasting glucose or HbA1c) was associated with worse sensorimotor nerve function for all six outcome measures, with associations of strongest magnitude for motor peroneal and tibial NCV, ßfasting glucose = -0.17 SD (-0.21, -0.13) and ßfasting glucose = -0.18 SD (-0.23, -0.14), respectively. Hyperglycaemia was also associated with higher VPT and neuropathic pain. Larger waist circumference was associated with worse sural nerve function and higher VPT. Triacylglycerol, HDL- and LDL-cholesterol, and blood pressure were not associated with worse nerve function; however, antihypertensive medication usage (suggestive of history of exposure to hypertension) was associated with worse peroneal compound muscle action potential amplitude and NCV. Smoking was associated with worse nerve function, higher VPT and higher risk for neuropathic pain. Inflammation was associated with worse nerve function and higher VPT, but only in those with type 2 diabetes. Type 2 diabetes and, to a lesser extent, prediabetes (impaired fasting glucose and/or impaired glucose tolerance) were associated with worse nerve function, higher VPT and neuropathic pain (p for trend <0.01 for all outcomes). CONCLUSIONS/INTERPRETATION: Hyperglycaemia (including the non-diabetic range) was most consistently associated with early-stage nerve damage. Nonetheless, larger waist circumference, inflammation, history of hypertension and smoking may also independently contribute to worse nerve function.

Assessment of Neurone-Specific Enolase, Glial Fibrillary Acidic Protein and S100 B as Spinal Cord Ischemia Biomarkers in Patients Undergoing Open and Endovascular Complex Aortic Surgery: A Single-Center Experience.

BACKGROUND: Despite all efforts, spinal cord ischemia (SCI) is a relevant and feared complication after open and endovascular thoracoabdominal aortic aneurysm (TAAA) repair. Besides the established correlation of motor evoked potentials (MEPs) and SCI, the usage of biomarkers for early detection of SCI intraoperatively and postoperatively after TAAA surgery is scarcely described in literature. METHODS: The methods include retrospective assessment of 33 patients (48.48% male) undergoing open and endovascular TAAA repair between January 2017 and January 2018. Levels of the biomarkers neurone-specific enolase (NSE), glial fibrillary acidic protein (GFAP), and S100 B were correlated with a decrease of the amplitude of the MEPs of more than 50%, indicating SCI. Linear mixed models were applied to test for differences in the biomarker levels between open and endovascular surgery and between different times of measurement. Post hoc analyses were performed using Tukey's multiple comparisons test. Logistic regression models were used to investigate the association between GFAP, NSE, and S100 B levels at different times and a significant decrease in MEP or in-hospital mortality. RESULTS: Altogether, 19 patients were treated by endovascular repair; 14 patients were treated by open repair; 5 patients were treated because of a type I TAAA; 7 received treatment because of a type II TAAA; 7, 10, and 4 patients received type III, IV, or V TAAA repair, respectively. In-hospital mortality was 18.18% (n = 6); 5 of these patients were treated because of symptomatic TAAA. MEP decrease could be observed in 18 cases (54.5%), with 16 (48.4%) recovering during the intervention. SCI could be observed in 9.09% (n = 3), 2 endovascular repairs leading to paraplegia and one open repair leading to paraparesis. All biomarkers showed increasing levels over time, with no statistically significant difference between open and endovascular repair. The difference in NSE and S100 B levels between the different times of measurements was statistically significant (P < 0.0001, P = 0.0017, respectively). In a univariable logistic regression analysis, no correlation with the end points "significant decrease in MEP" or "in-hospital mortality" was observed for any of the assessed biomarkers. CONCLUSIONS: SCI-related biomarkers, namely NSE and S100 B, show a relevant increase directly after open and endovascular TAAA surgery, while no clear association between these biomarker levels and an intraoperatively measurable indicator for SCI could be observed.

Recovery of lost motor evoked potentials in open thoracoabdominal aortic aneurysm repair using intercostal artery bypass.

Ischemia of the spinal cord remains a disastrous complication in thoracoabdominal aortic aneurysm (TAAA) surgery. We report a case of open type I TAAA repair during which no motor evoked potentials were detectable for >1 hour after aortic cross-clamping. The creation of three intercostal artery bypasses restored spinal cord perfusion. As the patient showed only moderate clinical signs of spinal cord ischemia afterward, we underline the role of neuromonitoring to guide intercostal artery bypass implantation during TAAA surgery as the combined use of neuromonitoring and intercostal artery bypass implantation may prevent paraplegia in specific TAAA cases.

High Spatial Inhomogeneity in the Intima-Media Thickness of the Common Carotid Artery is Associated with a Larger Degree of Stenosis in the Internal Carotid Artery: The PARISK Study.

Purpose Inhomogeneity of arterial wall thickness may be indicative of distal plaques. This study investigates the intra-subject association between relative spatial intima-media thickness (IMT) inhomogeneity of the common carotid artery (CCA) and the degree of stenosis of plaques in the internal carotid artery (ICA). Materials and Methods We included 240 patients with a recent ischemic stroke or transient ischemic attack and mild-to-moderate stenosis in the ipsilateral ICA. IMT inhomogeneity was extracted from B-mode ultrasound recordings. The degree of ICA stenosis was assessed on CT angiography according to the European Carotid Surgery Trial method. Patients were divided into groups with a low (≤ 2 %) and a high (> 2 %) IMT inhomogeneity scaled with respect to the local end-diastolic diameter. Results 182 patients had suitable CT and ultrasound measurements. Relative CCA-IMT inhomogeneity was similar for the symptomatic and asymptomatic side (difference: 0.02 %, p = 0.85). High relative IMT inhomogeneity was associated with a larger IMT (difference: 235 µm, p < 0.001) and larger degree of ICA stenosis (difference: 5 %, p = 0.023) which remained significant (p = 0.016) after adjustment for common risk factors. Conclusion Regardless of common risk factors, high relative CCA-IMT inhomogeneity is associated with a greater degree of ICA stenosis and is therefore indicative of atherosclerotic disease. The predictive value of CCA-IMT inhomogeneity for plaque progression and recurrence of cerebrovascular symptoms will be determined in the follow-up phase of PARISK.

Assessment of dynamic cerebral autoregulation and cerebral carbon dioxide reactivity during normothermic cardiopulmonary bypass.

Despite increased risk of neurological complications after cardiac surgery, monitoring of cerebral hemodynamics during cardiopulmonary bypass (CPB) is still not a common practice. Therefore, a technique to evaluate dynamic cerebral autoregulation and cerebral carbon dioxide reactivity (CO2R) during normothermic nonpulsatile CPB is presented. The technique uses continuous recording of invasive arterial blood pressure, middle cerebral artery blood flow velocity, absolute cerebral tissue oxygenation, in-line arterial carbon dioxide levels, and pump flow measurement in 37 adult male patients undergoing elective CPB. Cerebral autoregulation is estimated by transfer function analysis and the autoregulation index, based on the response to blood pressure variation induced by cyclic 6/min changes of indexed pump flow from 2.0 to 2.4 up to 2.8 L/min/m(2). CO2R was calculated from recordings of both cerebral blood flow velocity and cerebral tissue oxygenation. Cerebral autoregulation and CO2R were estimated at hypocapnia, normocapnia, and hypercapnia. CO2R was preserved during CPB, but significantly lower for hypocapnia compared with hypercapnia (p < 0.01). Conversely, cerebral autoregulation parameters such as gain, phase, and autoregulation index were significantly higher (p < 0.01) during hypocapnia compared with both normocapnia and hypercapnia. Assessing cerebral autoregulation and CO2R during CPB, by cyclic alteration of pump flow, showed an impaired cerebral autoregulation during hypercapnia.

Cyber medicine enables remote neuromonitoring during aortic surgery.

OBJECTIVE: This study assessed the feasibility and effectiveness of remote neuromonitoring as an adjunct to spinal cord protection during surgical repair of descending thoracic aortic aneurysms and thoracoabdominal aortic aneurysms. METHODS: Four aortic centers in three European countries participated in this prospective observational study. A similar surgical protocol was used in all centers, including assessment of spinal cord function by means of monitoring motor-evoked potentials (MEPs). MEP information was evaluated at one central neurophysiologic department in Maastricht, The Netherlands. Transfer of MEP data from all operating rooms to Maastricht was arranged by Internet connections. In all patients, the protective and surgical strategies to prevent paraplegia were based on MEPs. The on-site surgeons reacted in real time to the interpretation and feedback of the neurophysiologist. RESULTS: Between March 2009 and May 2011, 130 patients (85 men) were treated by open surgical repair. Extent of aneurysms was equally distributed among the centers. Neuromonitoring was technically stabile and successful in all patients. The transfer of data from the operating room in the different vascular centers was undisturbed and without any technical problems. By maintaining a mean distal aortic pressure of 60 mm Hg, MEPs were undisturbed in 65 patients (50%). In another 65 patients (50%), significant changes in MEPs prompted the surgical teams to initiate additional protective and surgical strategies to restore spinal cord perfusion. These measures were not effective in five patients (3.8%), and acute paraplegia resulted. Delayed paraplegia occurred in 10 patients (7.7%) but improved in three and recovered completely in another three. No false-negative or false-positive MEP recordings were experienced. CONCLUSIONS: Remote neuromonitoring of spinal cord function during open repair of descending thoracic aortic aneurysms and thoracoabdominal aortic aneurysms as a telemedicine technique is feasible and effective. It allows centralization of expertise and saves individual centers from investing in complex technology. The value of monitoring MEPs was confirmed in different aortic centers, resulting in adequate neurologic outcome after extensive aortic surgical procedures.

Multimodality imaging of carotid artery plaques: 18F-fluoro-2-deoxyglucose positron emission tomography, computed tomography, and magnetic resonance imaging.

BACKGROUND AND PURPOSE: This study's objective was to compare (18)F-fluoro-2-deoxyglucose positron emission tomography ((18)F-FDG PET), CT, and MRI of carotid plaque assessment. MATERIALS AND METHODS: Fifty patients with symptomatic carotid atherosclerosis underwent (18)F-FDG PET/CT and MRI. Correlations and agreement between imaging findings were assessed by Spearman and Pearson rank correlation tests, t tests, and Bland-Altman plots. RESULTS: Spearman rho between plaque (18)F-FDG standard uptake values and CT/MRI findings varied from -0.088 to 0.385. Maximum standard uptake value was significantly larger in plaques with intraplaque hemorrhage (1.56 vs 1.47; P=0.032). Standard uptake values did not significantly differ between plaques with an intact and thick fibrous cap and plaques with a thin or ruptured fibrous cap on MRI. (1.21 vs 1.23; P=0.323; and 1.45 vs 1.54; P=0.727). Pearson rho between CT and MRI measurements varied from 0.554 to 0.794 (P<0.001). For lipid-rich necrotic core volume, the CT-MRI correlation was stronger in mildly (10%) calcified plaques (Pearson rho 0.730 vs 0.475). Mean difference in measurement +/-95% limits of agreement between CT and MRI for minimum lumen area, volumes of vessel wall, lipid-rich necrotic core, calcifications, and fibrous tissue were 0.4+/-18.1 mm(2) (P=0.744), -41.9 +/-761.7 mm(3) (P=0.450), 78.4+/-305.0 mm(3) (P<0.001), 180.5+/-625.7 mm(3) (P=0.001), and -296.0+/-415.8 mm(3) (P<0.001), respectively. CONCLUSIONS: Overall, correlations between (18)F-FDG PET and CT/MRI findings are weak. Correlations between CT and MRI measurements are moderate to strong, but there is considerable variation in absolute differences.

Increased number of cerebral emboli during percutaneous endocardial pulmonary vein isolation versus a thoracoscopic epicardial approach.

OBJECTIVE: Pulmonary vein isolation (PVI) using ablation energy appears an effective treatment for atrial fibrillation (AF) with a success rate of approximately 80%. However, post-procedural neurological complications still occur in 0.5-10% of all patients undergoing PVI, presumably due to embolism. Therefore, we investigated the occurrence of cerebral micro-embolic signals (MES) as a surrogate marker for the risk of neurological impairment of two different PVI methods: (1) percutaneous endocardial radio-frequency (RF) ablation and (2) thoracoscopic epicardial ablation using RF energy. METHODS: Ten patients (eight persistent AF and two paroxysmal AF) underwent a minimally invasive thoracoscopic epicardial (EPI) RF ablation and 10 patients (one persistent AF and nine paroxysmal AF) underwent a percutaneous endocardial (ENDO) isolation. Transcranial Doppler (TCD) was used to detect an MES in the middle cerebral arteries. RESULTS: An average of 5 (+/-6) MES were detected during epicardial PVI procedure versus 3908 (+/-2816) MES during percutaneous endocardial PVI procedure. During the ablation application period, respectively, 1 (+/-1) and 2566 (+/-2296) cerebral MES were detected. CONCLUSIONS: Cerebral micro-emboli during epicardial ablation are almost absent when compared to the thousands of emboli measured during percutaneous endocardial ablation.

Reproducibility of fibrous cap status assessment of carotid artery plaques by contrast-enhanced MRI.

BACKGROUND AND PURPOSE: Reproducibility in identifying the fibrous cap (FC) of carotid artery plaques by noncontrast-enhanced MRI has been shown to be poor. The objective of this study was to assess the reproducibility of multisequence MRI, including contrast-enhanced images, in assessing FC status. METHODS: Forty-five symptomatic patients with 30% to 69% carotid artery stenosis underwent a multisequence MRI protocol, which included contrast-enhanced images. FC status (ie, discrimination between fibrotic and/or calcified plaques, plaques with a lipid-rich necrotic core and an intact and thick FC, and plaques with a lipid-rich necrotic core and a thin and/or ruptured FC) was independently assessed by 3 observers of which one also scored all images on a different occasion. Linear weighted kappa coefficients (kappa) were calculated as indicators of inter- and intraobserver agreement. RESULTS: On a per-slice basis, interobserver agreement was good (kappa=0.60, 0.64, and 0.71), whereas intraobserver agreement was very good (kappa=0.86). On a per-plaque basis, interobserver agreement was good (kappa=0.64, 0.69, and 0.78), whereas intraobserver agreement was very good (kappa=0.96). CONCLUSIONS: This study found good interobserver and very good intraobserver agreement in assessing FC status of carotid artery plaques. Future studies are warranted to determine the predictive value of FC status assessment by multisequence MRI, including contrast-enhanced images, on the occurrence of (recurrent) cerebral ischemic events.

The EmBlocker: efficiency of a new ultrasonic embolic protection device adjunctive to heart valve surgery.

PURPOSE: Perioperative cerebral microemboli in cardiac surgery are associated with postoperative neurologic complications. The EmBlocker (Neurosonix Ltd, Rehovot, Israel), a newly developed device should be positioned against the ascending aorta, and it produces an ultrasonic force expected to divert microemboli away from the cerebral vasculature and reduce cerebral emboli. DESCRIPTION: Twenty-one consecutive patients, undergoing a valve procedure, were enrolled into this nonrandomized pilot study. The EmBlocker (Neurosonix Ltd) was positioned in 11 consecutive patients and activated for 1 minute (1.5 W/cm(2)) during seven selected aortic manipulations and for 10 minutes (0.5 W/cm(2)) intermittently after cross-clamp removal. Transcranial Doppler-based quantification of microembolic signals was performed in all patients. EVALUATION: The use of the EmBlocker showed a significant overall reduction of the cerebral microembolic signals of 53%. CONCLUSIONS: The use of the EmBlocker during valve surgeries is associated with a reduction of perioperative cerebral microembolic signals. This new technology holds the potential to lower the risk of postoperative neurologic complications.

Transcranial measurement of cerebral microembolic signals during endocardial pulmonary vein isolation: comparison of three different ablation techniques.

INTRODUCTION: Isolation of the pulmonary veins (PVI) using high ablation energy is an effective treatment for atrial fibrillation (AF) with a success rate of 50-95%; however, postoperative neurological complications still occur in 0.5-10%. In this study the incidence of cerebral microembolic signals (MES) as a risk factor for neurological complications is examined during 3 percutaneous endocardial ablation procedure strategies: segmental PVI using a conventional radiofrequency (RF) ablation catheter, segmental PVI using an irrigated RF tip catheter, and circumferential PVI with a cryoballoon catheter (CB). METHODS AND RESULTS: Thirty patients underwent percutaneous endocardial PVI. Ostial isolation was performed in 10 patients with a conventional 4-mm RF catheter (CRF) and in 10 patients with a 4-mm irrigated RF catheter (IRF). A circumferential PVI was performed in 10 patients with a CB. Transcranial Doppler (TCD) monitoring was used to detect MES in the middle cerebral arteries. The total number of cerebral MES differs significantly among the 3 PVI groups; 3,908 cerebral MES were measured with use of the CRF catheter, 1,404 cerebral MES with use of the IRF catheter, and 935 cerebral MES with use of the CB catheter. CONCLUSION: This study demonstrates a significant difference in cerebral MES during PVI with 3 different ablation procedures. The use of an irrigated RF and a cryoballoon produces significantly fewer cerebral MES than the use of conventional RF for a PVI procedure, suggesting a higher risk for neurologic complications using conventional RF energy during a percutaneous PVI procedure.

Brain and spinal cord protection during simultaneous aortic arch and thoracoabdominal aneurysm repair.

OBJECTIVE: We assessed the surgical and neurological outcome of patients undergoing simultaneous repair of aortic arch and descending thoracic aortic aneurysms (DTAA) or thoracoabdominal aortic aneurysms (TAAA) via left thoracotomy or thoracolaparotomy. METHODS: During a 6-year period, we performed 32 procedures in 23 male and 9 female patients with DTAA or TAAA with concomitant aortic arch aneurysms. The mean age of the patients was 50.9 years (range, 18-75 years). Twenty-two patients suffered from DTAA, 4 had type-I TAAA, and 6 had type-II TAAA. The entire aortic arch was involved in 12 patients and the distal hemi-arch in 20 patients. The mean diameter of the aneurysms was 6 cm (range, 4.9-7.6 cm). All patients were operated on according to the protocol with cerebrospinal fluid drainage, distal aortic and selective organ perfusion, as well as antegrade brain perfusion. Neuromonitoring was performed by means of motor evoked potentials (MEPs), transcranial Doppler (TCD), and electroencephalography (EEG). RESULTS: All patients survived the surgical procedure and 30-day mortality did not occur. At the end of the procedure, all patients had adequate MEPs, TCD, and EEG. One patient died 47 days after operation due to gastrointestinal bleeding and therapy-resistant coagulopathy. Major postoperative complications like paraplegia or paraparesis, renal failure, and myocardial infarction were not encountered. One patient had a stroke but neurological deficits were irrelevant. Mean preoperative creatinine level was 125 mmol/L, which peaked to a mean maximal level of 130 and returned to 92 mmol/L at discharge. Other complications included bleeding requiring surgical intervention (n = 4), arrhythmia (n = 1), pneumonia (n = 5), and respiratory distress syndrome (n = 2). At a median follow-up of 38 months, all but 1 patient was alive and free of re-intervention. CONCLUSION: Single-stage repair of aortic arch and concomitant thoracic and thoracoabdominal aortic aneurysms via left-sided thoracotomy or thoraco-laparotomy yields excellent short- and midterm outcomes. Monitoring of cerebral and spinal cord function contributes to improved neurologic outcome.

Magnetic resonance angiography of collateral blood supply to spinal cord in thoracic and thoracoabdominal aortic aneurysm patients.

OBJECTIVE: Preservation of spinal cord blood supply during descending thoracic (TAA) and thoracoabdominal aortic aneurysm (TAAA) surgery is mandatory to prevent neurologic complications. Although collateral arteries have been identified occasionally and are considered crucial for maintaining spinal cord function in the individual patient, their critical functionality is poorly understood and very little experience exists with visualization. This study investigated whether the preoperative and postoperative presence or absence of collateral arteries detected by magnetic resonance angiography (MRA) is related to spinal cord function during the intraoperative exclusion of the segmental supply to the Adamkiewicz artery. METHODS: Spinal cord MRA was used to localize the Adamkiewicz artery and its segmental supplier in 85 patients scheduled for open elective surgery for TAA or TAAA. The segmental artery to the Adamkiewicz artery was inside the cross-clamped aortic area in 55 patients, and spinal cord supply was consequently dependent on collateral supply. In these 55 patients the presence of collaterals originating from arteries outside the cross-clamped aortic segment was related to changes in the intraoperative motor-evoked potentials (MEPs) that occurred before corrective measures. Twenty-one patients returned for postoperative MRA. RESULTS: A highly significant (P < .0015) relation was found between the presence of collaterals and intraoperative spinal cord function. In 30 of 31 patients (97%) in whom collaterals were identified, MEPs remained stable. The collaterals in most patients originated caudally to the distal clamp (eg, from the pelvic arteries), which were perfused by means of extracorporeal circulation during cross-clamping. The MEPs declined in 9 of 24 patients (38%) in whom no collaterals were preoperatively visualized. Postoperatively, the 21 patients who had MRA, including 10 in whom preoperatively no collaterals were found, displayed a well-developed collateral network. CONCLUSION: Collateral arteries supplying the spinal cord can be systematically visualized using MRA. Spinal cord blood supply during open aortic surgery may crucially depend on collateral arteries. Preoperatively identified collateral supply was 97% predictive for stable intraoperative spinal cord function. Patients in whom no collaterals can be depicted preoperatively are at increased risk for spinal cord dysfunction.

New ultrasonic radiation reduces cerebral emboli during extracorporeal circulation.

OBJECTIVE: Cardiac surgery is associated with intraoperative cerebral emboli, which can result in postoperative neurological complications. A new ultrasonic transducer (EmBlocker) can be positioned on the ascending aorta and activation of the EmBlocker is expected to divert emboli to the descending aorta, thereby decreasing emboli in the cerebral arteries. In this preliminary animal study, safety and efficiency of this technology were examined. METHODS: In 14 pigs (+/-70 kg), a median sternotomy was performed and the EmBlocker was positioned on the aorta ascendens at the level of the bifurcation of the aorta and the innominate artery. In one animal temperature measurements were performed. During these measurements, the EmBlocker was activated for four periods of 120 s of high power (1.5 W/cm(2)) and for four periods of 600 s of low power (0.5 W/cm(2)). In the safety study (n=6), the EmBlocker was activated twice the expected clinical duration (eight periods of 120 s of high power and, subsequently, one period of 20 min of low power). Tissue samples (control and sonicated) were collected after 1 week for histopathological evaluation (aorta, trachea, esophagus, vagus nerves). In the efficiency study (n=7), extracorporeal circulation was installed. Emboli (air and solid (1200, size 500 microm-750 microm)) were introduced in the proximal ascending aorta and the EmBlocker was alternately activated with high power for solid emboli injections and low power for air emboli injections. Transcranial Doppler (TCD) was used to analyse middle cerebral artery blood flow for occurrence of embolic signals, which were manually counted offline. RESULTS: Histopathology revealed no difference between control and sonicated tissue. There is a rise in temperature during EmBlocker activation, but in all measured tissues it was within limits; less then 42 degrees C for 2 min in the aorta wall directly under the EmBlocker. Use of the EmBlocker significantly reduced emboli in the cerebral arteries in an animal model; air emboli with 65% (left) and 69% (right) and solid emboli with 49% (left) and 50% (right). CONCLUSIONS: The new ultrasound technology can safely be applied and is capable of reducing emboli in the cerebral arteries during extracorporeal circulation. Use of the EmBlocker in cardiac surgery bears the potential to lower the risk of postoperative neurological complications. Clinical feasibility studies are in progress.

The role of evoked potential monitoring in operative management of type I and type II thoracoabdominal aortic aneurysms.

Spinal cord ischemia with subsequent paraplegia remains the most dreaded and impressive complication following thoracoabdominal aortic aneurysm repair. Protective measures, such as cerebrospinal fluid drainage, distal aortic perfusion, and epidural cooling, have significantly reduced paraplegia rate. A major impediment is the inability to assess the efficacy of reattaching intercostal arteries or the contributing value of the adjunctive procedures during the operation. Monitoring motor-evoked potentials is a reliable technique to assess spinal cord integrity, dictating surgical strategies to restore and maintain blood supply to the gray matter. Based on motor-evoked potentials, hemodynamic and operative maneuvers during thoracoabdominal aortic aneurysm repair resulted, in our experience, in prevention of neurologic deficit in 98% of patients.

Assessment of spinal cord integrity during thoracoabdominal aortic aneurysm repair.

BACKGROUND: Monitoring motor-evoked potentials (MEPs) is an accurate technique to assess spinal cord integrity during thoracoabdominal aortic aneurysm (TAAA) repair, guiding surgical strategies to prevent paraplegia. METHODS: In 210 consecutive patients with type I (n = 75), type II (n = 103), and type III (n = 32) TAAA surgical repair was performed using left heart bypass, cerebrospinal fluid drainage, and MEPs monitoring. RESULTS: Reliable MEPs were registered in all patients. The median total number of patent intercostal and lumbar arteries was five. After proximal aortic crossclamping, MEP decreased below 25% of base line in 72 patients (34%) indicating critical spinal cord ischemia, which could be corrected by increasing distal aortic pressure. By using sequential clamping it appeared that in 43% of type I and II cases spinal cord circulation was supplied between T5 and L1, and 57% between L1 and L5. In type II and III cases cord perfusion was dependent upon lower lumbar arteries in 16% and pelvic circulation in 8%, necessitating reattachment of these segmental arteries. In 9% of patients critical ischemic MEP changes occurred without visible arteries, requiring aortic endarterectomy and selective grafting. One patient suffered early paraplegia and 2 delayed, and 2 patients had temporary neurologic deficit (5 of 210; 2.4%). CONCLUSIONS: In patients with TAAA, blood supply to the spinal cord depends upon a highly variable collateral system. Monitoring MEPs is an accurate technique for detecting cord ischemia, guiding surgical tactics to reduce neurologic deficit (2.4%).

Spinal cord blood supply in patients with thoracoabdominal aortic aneurysms.

OBJECTIVE: In patients with thoracoabdominal aortic aneurysms (TAAAs), the blood supply to the spinal cord is highly variable and unpredictable because of obstructed intercostal and lumbar arteries. This study was performed for the prospective documentation of patent segmental arteries during TAAA repair and the assessment of their functional contribution to the spinal cord blood supply. METHODS: TAAA repair was performed in 184 consecutive patients (68 with type I aneurysm, 91 with type II, and 25 with type III) according to a protocol that included left heart bypass grafting, cerebrospinal fluid drainage, and the monitoring of motor-evoked potentials (MEPs). Patent intercostal and lumbar arteries were documented, and all reattached, selectively grafted, and oversewn segmental arteries were noted. MEP amplitude that decreased to less than 25% of baseline was considered an indication of critical spinal cord ischemia and prompted spinal cord revascularization. RESULTS: Adequate MEP levels were encountered in 183 of 184 patients. One patient had early paraplegia (absent MEPs), two patients had delayed paraplegia develop, and two patients had temporary paraparesis, which accounted for an overall neurologic deficit of 2.7%. The median total number of patent intercostal and lumbar arteries in type I, II, and III aneurysms was three, five, and five, respectively. In eight of 68 type I cases, no segmental arteries were seen between the fifth thoracic vertebrae (T5) and the first lumbar vertebrae (L1) and MEP levels remained adequate because of distal aortic perfusion. In 18 of 91 type II cases, the aortic segment T5 to L1 did not contain patent arteries, and in six of these patients, the segment L1 to L5 did not have lumbar arteries either. In the latter patients, MEP levels depended on the pelvic circulation provided with the left heart bypass graft. In the other 12 of 91 type II cases, the only patent arteries were the lumbar arteries between L3 and L5. The loss of MEPs could be corrected with the reattachment of these arteries. In seven of 25 type III cases, the MEP levels also depended on lumbar arteries L3 to L5 and in three of 25 cases, no segmental arteries were available and MEP levels recovered after the reperfusion of the pelvic circulation. With the combination of the findings of type II and III cases, spinal cord perfusion was directed by lower lumbar arteries in 16% of the cases (19 of 116) and pelvic circulation in 8% of the cases (nine of 116). CONCLUSION: In patients with TAAA, most intercostal and lumbar arteries are occluded and spinal cord perfusion depends on an eminent collateral network, which includes lumbar arteries and pelvic circulation. The monitoring of MEPs is a sensitive technique for the assessment of spinal cord ischemia and the identification of segmental arteries that critically contribute to spinal cord perfusion. Surgical strategies on the basis of this technique reduced the incidence rate of neurologic deficit to less than 3%.