Oren K. Steinmetz

Carotid artery duplex scanning in preoperative assessment for coronary artery revascularization: The association between peripheral vascular disease, carotid artery stenosis, and stroke

PURPOSE The purpose of this study was to identify high-risk populations for severe carotid artery disease (SCD) and neurologic events (NE) after nonemergency isolated coronary artery bypass graft procedures (CABG). METHODS Between February 1989 and July 1992, 387 patients underwent preoperative carotid artery duplex scanning as part of a preoperative assessment for nonemergency cardiac procedures. Of these patients, 376 had isolated CABG, and 11 had combined carotid endarterectomy (CEA) and CABG. Patient demographics, risk factors, and preoperative neurologic symptoms were recorded and analyzed. Severe carotid artery disease was defined as a 80% or greater stenosis of either internal carotid artery by carotid artery duplex scanning. Patients were evaluated for neurologic events (cerebrovascular accident, transient ischemic attack, amaurosis fugax, or reversible ischemic neurologic deficits) during the in-hospital postoperative period. RESULTS The prevalence of SCD was 8.5% (33 patients). The 33 patients with SCD were significantly older (65.6 +/- 6.5 years vs 62.5 +/- 10.4 years, p = 0.02), had previous CEA (27.3% vs 2.0%, p = 0.00001), had preoperative neurologic symptoms (21.2% vs 5.9%, p = 0.002), and had peripheral vascular disease (PVD) (63.6% vs 16.9%, p = 0.00001). The sensitivity of PVD for SCD is 63.6% (n = 21/33) (specificity 83.1%, positive predictive value 25.9%, negative predictive value 96.1%). In patients undergoing CABG alone, those who had postoperative NE were older (69.6 +/- 6.7 years vs 62.5 +/- 10.3 years, p = 0.036) and more likely to have PVD (50% vs 19.7%, p = 0.034), SCD (40% vs 4.9%, p = 0.001) and previous CEA (40% vs 2.7%, p = 0.0002). The incidence of postoperative NE in patients with SCD was 18.2% vs 1.7% in patients without SCD (p = 0.001). The sensitivity of SCD for NE was 40% (n = 4/10) (specificity 95.1%, positive predictive value 18.2%, negative predictive value 98.3%). CONCLUSIONS PVD may be helpful to identify patients at high risk for severe carotid artery stenosis. Postoperative NE in patients with CABG are associated with increasing age, carotid artery stenosis greater than 80%, previous CEA, and PVD.

Protein secretion in yeast: Two chromosomal mutants that oversecrete killer toxin in Saccharomyces cerevisiae.

SummaryTwo chromosomal mutations in yeast that result in oversecretion of the K1 killer toxin protein were examined. A recessive mutation in gene ski5 appears to lead to toxin oversecretion through a defect in a cell surface, PMSF-inhibited protease. A wild type killer strain degraded toxin following synthesis, and degradation could be partially prevented by addition of PMSF to the growth medium. The ski5 mutation caused an approximate ten fold oversecretion of toxin, similar to that seen in a PMSF-treated wild type culture, and no increased oversecretion in the presence of PMSF. The ski5 mutation caused oversecretion of other low molecular weight secreted proteins and appeared to oversecrete the α-factor pheromone, as judged by activity tests. The ski5 mutation was complemented by mutations in ski genes 1–4, and the mutant was not supersensitive to mating pheromones or K2 killer toxin.We also examined killer strains with a mutation in the nuclear gene krel which results in a defective (1→6)-β-D-glucan cell wall receptor for killer toxin. Such strains oversecrete toxin into the growth medium, but also, unexpectedly, oversecrete most other secreted proteins. The defect in (1→6)-β-D-glucan in these mutants appears to perturb the partitioning of secreted proteins between the cell wall and the medium.

Paraplegia prevention branches: A new adjunct for preventing or treating spinal cord injury after endovascular repair of thoracoabdominal aneurysms

In this report, we describe a technique that could potentially be used for both prevention and treatment of spinal cord ischemia (SCI) in endovascular repair of thoracoabdominal aneurysms. This technique involves using a specially designed endograft with side branches (paraplegia prevention branches [PPBs]), which are left patent to perfuse the aneurysmal sac and any associated lumbar or intercostal arteries in the early postoperative period. The use of PPBs with this technique is feasible and allows for a temporary controlled endoleak that may be useful for preventing or reversing spinal cord injury. This technique may be considered as an adjunct to the more standard perioperative physiological manipulations such as permissive hypertension and spinal fluid drainage.

Predictive factors for limb occlusions after endovascular aneurysm repair

OBJECTIVE Greater flexibility and smaller sizes for introducer sheaths in the newest stent grafts increase the feasibility of endovascular aneurysm repair but raise concerns about long-term limb patency. The aim of the study was to determine the incidence of and predictive factors for limb occlusion after use of the Endurant stent graft (Medtronic Inc, Minneapolis, Minn) for abdominal aortic aneurysm. METHODS The Endurant Stent Graft Natural Selection Global Postmarket Registry (ENGAGE) prospectively included 1143 patients treated with bifurcated devices who were observed for up to 2 years. Limb occlusions were evidenced by computed tomography, angiography, or ultrasound. To predict stent graft limb occlusion, a two-step model-building technique was applied. We first identified predictors from a total of 47 covariates obtained at baseline and in the periprocedural period. Subsequently, we reduced the set of potential predictors to key factors that are clinically meaningful. To handle large numbers of covariates, we used the Classification And Regression Tree (CART) method. RESULTS Forty-two stent graft limbs occluded in 39 patients (3.4% of the patients). At 2 years, the rate of freedom from stent graft limb occlusion calculated by Kaplan-Meier plot was 97.9% (standard error [SE], 0.33%). Of the 42 occlusions, 13 (31%) were observed within 30 days and 30 (71%) within 6 months. The strongest independent predictors were distal landing zone on the external iliac artery, external iliac artery diameter ≤10 mm, and kinking. High-risk vs low-risk patients were identified according to a decision tree based on the strongest predictors. Freedom from stent graft limb occlusion was 96.1% (SE, 0.64%) in high-risk patients vs 99.6% (SE, 0.19%) in low-risk patients. CONCLUSIONS After Endurant stent grafting, the incidence of limb occlusion was low. Classifying patients as high risk vs low risk according to the algorithm used in this study may help define specific strategies to prevent limb occlusion and improve the overall results of endovascular aneurysm repair using the latest generation of stent grafts.

Intraoperative duplex scanning for carotid endarterectomy

OBJECTIVES To evaluate the results of intraoperative duplex scans during carotid endarterectomy. DESIGN Retrospective case review. MATERIALS One-hundred consecutive intraoperative carotid duplex scans performed during carotid endarterectomy between July 1993 and December 1995 at a university teaching hospital. METHODS Abnormalities of the B-mode image and/or the Doppler flow analysis were classified. The result of intraoperative carotid duplex scans (ICDS) were related to the events of the intraoperative course, perioperative neurologic morbidity and mortality, and to residual carotid stenosis. RESULTS Abnormalities of the ICDS were demonstrated in 13 cases (13%). Abnormalities were classified into four types: I, internal carotid artery spasm (n = 9); II, high distal resistance flow (n = 2); III, high grade residual stenosis (n = 1); IV, intraluminal thrombosis (n = 1). Immediate intraoperative exploration and revision of the endarterectomy was performed based on the ICDS in two cases (type III and IV) and the findings of ICDS were confirmed. The other 11 cases with abnormal ICDS (types I, II) were not revised and duplex scans done 1 month postoperatively (available in 10 cases) showed normal carotid artery flow. Intraoperative angiography was performed selectively in five cases and confirmed the results of ICDS. Reversible abnormalities of the ICDS were not associated wit perioperative morbidity or residual carotid stenosis. CONCLUSIONS Intraoperative carotid duplex scanning can be used to assess the immediate technical adequacy of carotid endarterectomy. B-mode image and Doppler flow abnormalities which are reversible can be distinguished from those which require immediate revision.

Association of Ultrasonic Texture and Echodensity Features Between Sides in Patients with Bilateral Carotid Atherosclerosis

OBJECTIVES Our objective was to estimate the correlation of echodensity and textural features, using ultrasound and digital image analysis, between plaques in patients with bilateral carotid stenosis. DESIGN Cross-sectional observational study. METHODS Patients undergoing carotid endarterectomy were recruited from Vascular Surgery at the Royal Victoria and Jewish General hospitals in Montreal, Canada. Bilateral pre-operative carotid ultrasound and digital image analysis was performed to extract echodensity and textural features using a commercially available Plaque Texture Analysis software (LifeQMedical Ltd). Principal component analysis (PCA) was performed. Partial correlation coefficients for PCA and individual imaging variables between surgical and contralateral plaques were calculated with adjustment for age, sex, contralateral stenosis, and statin use. RESULTS In the whole group (n = 104), the six identified PCA variables and 42/50 individual imaging variables were moderately correlated (r = .211-.641). Correlations between sides were increased in patients with ≥50% contralateral stenosis and symptomatic patients. CONCLUSION Textural and echodensity features of carotid plaques were similar between two sides in patients with bilateral stenosis, supporting the notion that plaque instability is determined by systemic factors. Patients with unstable features of one plaque should perhaps be monitored more closely or treated more aggressively for their contralateral stenosis, particularly if this is hemodynamically significant.

Videoendoscopic thoracic aorta-to-femoral artery bypassA feasibility study in a canine model

PURPOSE This study was undertaken to determine whether videoendoscopic thoracic aorta-to-femoral artery bypass is a technically feasible operation. METHODS An acute canine study involving five mongrel dogs was carried out. After the dogs had been given a general anesthetic, the femoral arteries were exposed in the traditional fashion. On the left side, a retroperitoneal, retrorenal tunnel was extended from the common femoral artery to the diaphragm. Under videoendoscopic control, the tunnel was opened through the posterior thoracic attachments of the diaphragm into the thoracic cavity. A Dacron graft was tunneled from the thoracic cavity on the left to the left groin. The thoracic aorta was controlled with a side-biting clamp, and an endoscopically performed end graft-to-side thoracic aortic anastomosis was created. After completion of the thoracic anastomosis, the left femoral anastomosis was created in a traditional manner. A left-to-right femoral bypass completed the lower extremity vascular procedure. An open thoracotomy was avoided. RESULTS Videoendoscopic thoracic aorta-to-femoral artery bypass was successfully performed in all five animals. All components of the thoracic procedure, including exposure, dissection, vessel control, cross-clamping, and anastomosis, were performed through the thoracic ports with conventional laparoscopic instruments. Blood loss was minimal. All animals survived the procedure before being killed. CONCLUSION Videoendoscopic thoracic aorta-to-femoral artery bypass is a technically feasible operation in a canine model. Advantages of this unique approach over the experimental laparoscopic and the traditional transperitoneal open aortofemoral bypass include ease of aortic exposure, ability to control a segment of disease-free aorta, and anastomosis in a disease-free segment of aorta. Potential advantages include decreased perioperative morbidity rates with the videoendoscopic approach. Before there is clinical consideration of this surgical approach, long-term experiments are required to demonstrate the safety of the procedure.

Midterm Results Following Endovascular Repair of Blunt Thoracic Aortic Injuries

Objective: Previous studies have focused on early outcomes of thoracic endovascular repair (TEVAR) of blunt thoracic aortic injuries (BTAIs). Late results remain ill-defined. The purpose of this study is to review the midterm results of our experience with endovascular repair of BTAIs. Methods: A retrospective analysis was performed reviewing all endovascular repairs of BTAIs from 2002 to present. Preoperative, operative, and postoperative variables were recorded. Clinical end points included aortic-related mortality, stroke and paraplegia, hospital length of stay, procedure-related complications, endoleaks, and reinterventions. Computed tomography data sets were postprocessed for assessing integrity of stent grafts and late complications. Results: A total of 24 cases of BTAIs treated with TEVAR were identified. Thoracic endovascular repair was successful in treating BTAIs in all patients and there were no instances of procedure-related death, stroke, or paraplegia. One access complication occurred, requiring an iliofemoral bypass. Actuarial survival estimates and freedom from reintervention at 5 years were 88.7% and 95.8%, respectively. No late endoleaks, stent fractures, or device migration were identified. One patient required a secondary intervention 1 year following the initial repair to treat a pseudocoarctation syndrome caused by a diaphragm at the distal half of the stented aorta. This was treated successfully with repeated endografting. Conclusions: Thoracic endovascular repair for BTAIs can be performed safely with low periprocedural mortality and morbidity. Midterm follow-up data presented in this report further support the therapeutic role of endoluminal approach for treating BTAIs in anatomically suitable patients.

Morphologic evaluation of ruptured and symptomatic abdominal aortic aneurysm by three-dimensional modeling.

OBJECTIVE To identify geometric indices of abdominal aortic aneurysms (AAAs) on computed tomography that are associated with higher risk of rupture. METHODS This retrospective case-control, institutional review board-approved study involved 63 cases with ruptured or symptomatic AAA and 94 controls with asymptomatic AAA. Three-dimensional models were generated from computed tomography segmentation and used for the calculation of 27 geometric indices. On the basis of the results of univariate analysis and multivariable sequential logistic regression analyses with a forward stepwise model selection based on likelihood ratios, a traditional model based on gender and maximal diameter (Dmax) was compared with a model that also incorporated geometric indices while adjusting for gender and Dmax. Receiver operating characteristic (ROC) curves were calculated for these two models to evaluate their classification accuracy. RESULTS Univariate analysis revealed that gender (P = .024), Dmax (P = .001), and 14 other geometric indices were associated with AAA rupture at P < .05. In the multivariable analysis, adjusting for gender and Dmax, the AAA with a higher bulge location (P = .020) and lower mean averaged area (P = .005) were associated with AAA rupture. With these two geometric indices, the area under the ROC curve showed an improvement from 0.67 (95% confidence interval, 0.58-0.77) to 0.75 (95% confidence interval, 0.67-0.83; P < .001). Our predictive model showed comparable sensitivity (64% vs 60%) and specificity (79% vs 77%) with current treatment criteria based on gender and diameter at the point optimizing the Youden index (sensitivity + specificity - 1) on the ROC curve. CONCLUSIONS Two geometric indices derived from AAA three-dimensional modeling were independently associated with AAA rupture. The addition of these indices in a predictive model based on current treatment criteria modestly improved the accuracy to detect aneurysm rupture.

Heparin-induced thrombocytopenia causing graft thrombosis and bowel ischemia postendovascular aneurysm repair

Heparin-induced thrombocytopenia (HIT) is an immune-mediated thrombocytopenia resulting from prior heparin exposure. It can be associated with limb- or life-threatening thrombotic events. Patients undergoing any vascular procedures including endovascular procedures that require heparin administration are at risk. There is very little reported in the literature with regards to thrombosis associated with HIT after endovascular aortic aneurysm repair. All reported cases of HIT thrombosis presented as acute arterial lower limb ischemia or deep vein thrombosis. In this report, we present a case of HIT complicated by stent graft thrombosis and bowel ischemia.