Oliver Wolf

Differences in number, size and location of intracranial microembolic lesions after surgical versus endovascular treatment without protection device of carotid artery stenosis.

Abstract.Background and purpose:The benefit of carotid endarterectomy in symptomatic high-grade stenosis has long been proven. The role of angioplasty as an alternative is still a matter of debate. We compared the occurrence of intraprocedural microembolic signals and ischemic lesions between carotid endarterectomy (CEA) and carotid angioplasty with stent placement (CAS) without a protection device.Methods:88 patients who underwent a CEA and 41 patients who underwent CAS were prospectively investigated. One day before and after the intervention diffusion weighted MRI-studies were obtained. In 21 CEA and 18 CAS patients transcranial Doppler (TCD) monitoring was performed during the procedure to detect microembolic signals (MES).Results:DWI-lesions could be detected after intervention in 17% of the CEA patients compared with 54% of the CAS patients (p<0.005). The median lesion volume was 0.08cm3 in the CEA group and 0.02cm3 in the CAS group (p<0.001). Ischemic complications consisted of 2 strokes (2.3%) with symptoms lasting more than seven days in the CEA group and 1 stroke (2.4 %) in the CAS group. The median number of MES in the CEA group was 17 versus 61 in the CAS group (p<0.001). No significant correlation was found between the total number of MES and ischemic lesions in either group.Conclusion:A larger number of emboligenic particles with smaller volume is detached during CAS. Additionally DWI lesions were observed in different territories after CAS but not after CEA. Conventional TCD emboli detection is not useful to compare interventional therapies of the carotid arteries.

Microembolic Signals Detected by Transcranial Doppler Sonography During Carotid Endarterectomy and Correlation With Serial Diffusion-Weighted Imaging

Background and Purpose— Embolic events are a major cause for procedure-related strokes after carotid endarterectomy (CEA). Transcranial Doppler sonography can reveal embolic events as microembolic signals (MES) during CEA. MES during declamping and shunting are frequently detected. MES during shunting are rare and known to be correlated with the neurological outcome of the patient. In the present study, we analyzed the occurrence of MES within different stages of CEA and whether MES within those stages were correlated with cerebral ischemia, as detected by diffusion-weighted imaging (DWI), and brain infarction, as detected by contrast-enhanced MRI. Methods— Thirty-three patients were monitored intraoperatively for MES using transcranial Doppler sonography. DWI was performed within 24 hours before and after surgery. Positive postoperative DWI led to reexamination with contrast-enhanced T1-MRI 7 to 10 days after CEA for detection of cerebral infarction. Results— MES were detected in 32 of 33 patients. The highest number of MES was found during shunting and declamping. A significant correlation was found between MES and DWI-lesions during dissection. A significant correlation was found between MES during dissection and shunting, and nonsignificant correlation was found between MES and the occurrence of cerebral infarction. Conclusion— MES could be regularly detected during CEA. Dissection and shunting seem to be the most vulnerable stages of the procedure.

Embolic Signals in Unselected Stroke Patients Prevalence and Diagnostic Benefit

Background and Purpose— The present study investigated the prevalence of cerebral microemboli detected by transcranial Doppler sonography in unselected stroke and transient ischemic attack (TIA) patients under standard clinical conditions. We aimed to evaluate the feasibility and the value of the method for clinical use. Methods— The records of 937 consecutive patients who were investigated between October 1995 and August 2004 at our institution were reviewed. Stroke or TIA were subtyped using the TOAST classification criteria. Results— Two hundred and eighty-four subjects were excluded because there was an interval of >14 days between onset of symptoms and examination, no definite diagnosis of stroke or TIA at discharge, or an artificial heart valve. Embolic signals (ES) were detected in 37 (5.7%) of the remaining 653 patients. In subjects with positive ES detection the mean interval between symptom onset and ES detection was 4.9 (SD 4.0) days compared with 5.4 (SD 3.5) days in the remaining patients (P=0.01). ES were more common in patients with large-artery atherosclerosis compared with other subtype groups (P<0.001). The proportion of detected signals was influenced by the antihemostatic treatment: ES were found more often in anticoagulated patients than in patients receiving antiplatelet medication (P<0.001). Conclusions— The study shows a high clinical significance of ES in patients with recent stroke attributable to arterio-arterial embolism or of cardiac embolic origin and the high specificity of the technique. Given the low sensitivity shown, ES detection cannot generally be recommended for routine diagnostics in stroke patients.

Flow velocities after carotid artery stenting: impact of stent design. A fluid dynamics study in a carotid artery model with laser Doppler anemometry.

Purpose To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model.MethodsThree different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 μm. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles.ResultsThe flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume.ConclusionsStent placement across the carotid artery bifurcation induces alterations of the physiologic flow behavior. Depending on the stent design the flow alterations are located in different regions. All the stents tested were suitable for the carotid bifurcation. The MembraX prototype has shown promising hemodynamic properties ex vivo.

Detection of unstable carotid artery stenosis using MRI

Background and purposeCarotid artery stenosis can be classified by magnetic resonance imaging (MRI) as lesion types I–VIII according to a modified histological scheme based on American Heart Association (AHA) guidelines. Lesion types IV–V and VI are regarded as high-risk plaques.We aimed to evaluate the clinical relevance of this classification for identifying unstable plaques.MethodsEighty-five patients (29 female) with severe carotid artery stenosis (diagnosed by Doppler and duplex ultrasonography) were imaged using a 1.5 T scanner with bilateral phased-array carotid coils. T1-, T2-, time-offlight (TOF) and proton-density (PD)-weighted studies were obtained. The carotid plaques were classified as lesion types III–VIII according to the MRI-modified AHA criteria.ResultsThirty-five patients presented with a recently symptomatic stenosis; 50 patients were asymptomatic. Lesion types IV–V (51.4 % vs. 22 %) and VI (20 % vs. 4%; P < 0.0001) were found significantly more often in symptomatic patients compared to those without a history of cerebral ischemia.ConclusionsThe distribution of lesion types differs significantly between symptomatic and asymptomatic carotid artery stenosis. High-risk lesion types IV–V and VI were overrepresented in recently symptomatic patients. MRI according to the modified AHA-criteria may be a suitable tool for detection of unstable carotid lesions.

Combined Open and Endovascular Treatment of Thoracoabdominal Aneurysms and Secondary Expanding Aortic Dissections: Early and Mid-Term Results From a Single-Center Series

BACKGROUND We present a review of our experience with combined surgical therapy with endovascular stent repair and conventional revascularization of the supraaortic and/or visceral/renal arteries (hybrid procedure) in the treatment of thoracoabdominal aortic aneurysms and dissections. METHODS We followed 20 patients (7 women, median age 58.3 years, age range 37-68 years) prospectively. Severe comorbidity was present in 7 patients, 13 patients had previous aortic surgery. The median diameter of the thoracoabdominal aneurysm was 74.4 mm (Crawford I, 1 patient; II, 11; III, 7; V, 1), and 13 patients had previous aortic surgery. After visceral and renal revascularization, three stent grafts were implanted on average. Follow-up examination was every 6 months. The median follow-up was 174.5 days (15-375 days). RESULTS The 30-day mortality was 10% and the neurological complication rate was 10% with incomplete paraparesis in 2 patients. Computed tomography scanning revealed six endoleaks in 5 patients (Type Ia, 3 patients; Ib, 1; II, 1; III, 1) and four visceral graft occlusions in 4 patients (right renal artery, 2 patients; left renal artery, 2). Endoleaks (Ia, Ib, and III) were surgically revised. During follow-up, 3 patients died. The remaining patients recovered to full activity. A significant aneurysm shrinkage was found in 5 patients. Two patients developed secondary endoleaks. CONCLUSION Our results show that hybrid procedure might be an alternative to conventional thoracoabdominal repair of the aorta, especially in high-risk patients.

Chronic Mesenteric Ischemia – Surgical and Interventional Options in Therapy

Chronic mesenteric ischemia (CMI) is an unusual but important cause of abdominal pain accounting for 5-8% of all intestinal ischemic events. Most commonly it is caused by atherosclerotic occlusions or severe stenosis. Symptoms occur when at least two of the three main splanchnic vessels are affected. The course is frequently asymptomatic, resulting from an extensive collateralization. Intestinal angina combined with weight loss and sitophobia are typical clinical features. Therapeutic options are conventional surgical therapy with thrombendarterectomy or bypass as well as percutaneous angioplasty with or without stenting. In symptomatic disease immediate therapy is essential because the natural course is life-threatening. Invasive treatment of asymptomatic but significant CMI has to be seriously considered as it developed into symptomatic disease with a high possibility.

Improvement of microcirculation after percutaneous transluminal angioplasty in the lower limb with prostaglandin E1.

OBJECTIVE The aim of the study was to investigate prospectively the microcirculation after angioplasty and its improvement with additional Prostaglandin E1 (PGE1) therapy assessed by transcutaneous pressure of oxygen. PATIENTS AND METHODS 45 patients with intermittent claudication eligible for angioplasty were enrolled in a prospective randomised controlled clinical trial. Patients received either intra-arterial bolus of 40 microg PGE1 in addition to angioplasty or a 40 microg PGE1 intravenous infusion. Control group received no trial medication. Additional 15 patients undergoing intra-arterial angiography were also investigated. tcpO(2) values were recorded distal to the PTA region before, during the intervention, 24h, 2 and 4 weeks after intervention. Clinical endpoint was the change of tcpO(2) values 4 weeks after intervention. RESULTS During the 4 week follow-up tcpO(2) values decreased in patients treated with angioplasty. At the same time tcpO(2) increased significantly in those patients additionally treated with intra-arterial PGE1 bolus injection as well as with intravenous PGE1 infusion. CONCLUSIONS Impaired microcirculation after angioplasty can be improved with additional intravenous as well as intra-arterial PGE1 administration.

Analyse der Ursache postoperativer cerebraler Läsionen nach Carotis-Thrombendarteriektomie (CEA) mittels diffusionsgewichteter Magnetresonanztomografie und intraoperativer Mikroemboliedetektion

Die Mikroembolisation bei der Carotisendarteriektomie stellt ein Risiko fur perioperative neurologische Komplikationen dar. Inwieweit die Ergebnisse der intraoperativen Mikroemboliedetektion hinsichtlich der Auspragung der postoperativen neurologischen Schadigung relevant sind, ist bisher noch nicht hinreichend geklart. Ziel der Arbeit ist es, zu untersuchen, ob eine Korrelation zwischen intraoperativer Mikroemboliedetektion und postoperative aufgetretenen neurologischen Lasionen besteht. Ebenso soll ein Vergleich der Befunde der diffusionsgewichteten MRT hinsichtlich HITS mit den klinischen Ergebnissen erfolgen. Material und Methode: Es wird bei 100 konsekutiven Patienten mit duplexsono-grafisch und/oder angiografisch gesicherten, hamodynamisch wirksamen Carotisstenosen praoperativ eine fachneurologische Untersuchung sowie eine diffusionsgewichtete MRT-Untersuchung durchgefuhrt. Nach operativer Intervention mit Endarteriektomie der A. carotis in ITN, wobei die Mikroemboliedetektion mittels transcraniellem Doppler (TCD) erfolgt, wurde am ersten postoperativen Tag eine erneute fachneurologische Untersuchung sowie eine diffusionsgewichtete MRT-Untersuchung durchgefuhrt. Bei fokalen Diffusionsstorungen erfolgt dann ca. 1 Woche spater erneut eine komplette diffusionsgewichtete MRT-Untersuchung inklusive KM-Gabe zur Differenzierung passagerer ‚Foci’ versus ‚Ischamie mit Schrankenstorung’. Ergebnisse: Bislang wurden 66 Patienten mit 29 symptomatischen und 37 asymptomatischen Stenosen evaluiert. Keiner der eingeschlossenen Patienten wies frische cerebrale Ischamien oder Schrankenstorungen auf. Bei der ersten postoperativen Kontrolle zeigten sich bei 15 Patienten bei der diffusionsgewichteten Sequenz mehrere im Stromgebiet der a. cerebri media gelegene Lasionen. Schluβfolgerung: Die bisherigen Ergebnisse zeigen, dass die Inzidenz ischamischer Lasionen embolischer Natur gering sind. Zur Korrelation mit den klinisch-neurologischen Befunden ist noch keine differenzierte Aussage moglich. Eine weitere Ergebnisoptimierung erscheint wunschenswert, da angesichts des prophylaktischen Charakters der CEA neu auftretende neurologische Komplikation besonders schwer wiegen.