Multicenter Postmarket Analysis of the Neuroform Atlas Stent for Stent-Assisted Coil Embolization of Intracranial Aneurysms

BACKGROUND AND PURPOSE

The Neuroform Atlas is a new microstent to assist coil embolization of intracranial aneurysms that recently gained FDA approval. We present a postmarket multicenter analysis of the Neuroform Atlas stent.

MATERIALS AND METHODS

On the basis of retrospective chart review from 11 academic centers, we analyzed patients treated with the Neuroform Atlas after FDA exemption from January 2018 to June 2019. Clinical and radiologic parameters included patient demographics, aneurysm characteristics, stent parameters, complications, and outcomes at discharge and last follow-up.

RESULTS

Overall, 128 aneurysms in 128 patients (median age, 62 years) were treated with 138 stents. Risk factors included smoking (59.4%), multiple aneurysms (27.3%), and family history of aneurysms (16.4%). Most patients were treated electively (93.7%), and 8 (6.3%) underwent treatment within 2 weeks of subarachnoid hemorrhage. Previous aneurysm treatment failure was present in 21% of cases. Wide-neck aneurysms (80.5%), small aneurysm size (<7 mm, 76.6%), and bifurcation aneurysm location (basilar apex, 28.9%; anterior communicating artery, 27.3%; and middle cerebral artery bifurcation, 12.5%) were common. A single stent was used in 92.2% of cases, and a single catheter for both stent placement and coiling was used in 59.4% of cases. Technical complications during stent deployment occurred in 4.7% of cases; symptomatic thromboembolic stroke, in 2.3%; and symptomatic hemorrhage, in 0.8%. Favorable Raymond grades (Raymond-Roy occlusion classification) I and II were achieved in 82.9% at discharge and 89.5% at last follow-up. mRS ≤2 was determined in 96.9% of patients at last follow-up. The immediate Raymond-Roy occlusion classification grade correlated with aneurysm location (P < .0001) and rupture status during treatment (P = .03).

CONCLUSIONS

This multicenter analysis provides a real-world safety and efficacy profile for the treatment of intracranial aneurysms with the Neuroform Atlas stent.

Computational Modeling of Venous Sinus Stenosis in Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE

Idiopathic intracranial hypertension has been associated with dural venous sinus stenosis in some patients, but the hemodynamic environment of the dural venous sinuses has not been quantitatively described. Here, we present the first such computational fluid dynamics model by using patient-specific blood pressure measurements.

MATERIALS AND METHODS

Six patients with idiopathic intracranial hypertension and at least 1 stenosis or atresia at the transverse/sigmoid sinus junction underwent MR venography followed by cerebral venography and manometry throughout the dural venous sinuses. Patient-specific computational fluid dynamics models were created by using MR venography anatomy, with venous pressure measurements as boundary conditions. Blood flow and wall shear stress were calculated for each patient.

RESULTS

Computational models of the dural venous sinuses were successfully reconstructed in all 6 patients with patient-specific boundary conditions. Three patients demonstrated a pathologic pressure gradient (≥8 mm Hg) across 4 dural venous sinus stenoses. Small sample size precludes statistical comparisons, but average overall flow throughout the dural venous sinuses of patients with pathologic pressure gradients was higher than in those without them (1041.00 ± 506.52 mL/min versus 358.00 ± 190.95 mL/min). Wall shear stress was also higher across stenoses in patients with pathologic pressure gradients (37.66 ± 48.39 Pa versus 7.02 ± 13.60 Pa).

CONCLUSIONS

The hemodynamic environment of the dural venous sinuses can be computationally modeled by using patient-specific anatomy and physiologic measurements in patients with idiopathic intracranial hypertension. There was substantially higher blood flow and wall shear stress in patients with pathologic pressure gradients.

In vitro validation of endovascular Doppler-derived flow rates in models of the cerebral circulation

This study presents validation of endovascular Doppler velocimetry-based volumetric flow rate measurements conducted in a pulsatile flow loop simulating conditions in both the internal carotid and basilar artery. In vitro models of cerebral vessels, each containing an aneurysm, were fabricated from patient anatomies extracted from 3D rotational angiography. Flow velocity measurements were collected with three different experimental techniques: an endovascular Doppler wire, Particle Image Velocimetry, and a time-resolved ultrasonic flow meter. Womersley's theory of pulsatile flow in a cylindrical vessel was used to compute time-resolved volumetric flow rates from the endovascular Doppler velocity. The volumetric flow rates computed from the Doppler measurements were compared to those from the Particle Image Velocimetry profile measurements, and the direct measurements from the ultrasonic flow meter. The study establishes confidence intervals for any systematic or random errors associated with the wire-derived flow rates as benchmarked to the other two modalities. There is an approximately 10% random error in the Doppler-derived peak and time-averaged flow rates. There is a measurable uniform bias, about 15% too low, in the time-averaged Doppler-derived flow rates. There is also a small proportional bias in the peak systolic Doppler-derived flow rates. Potential sources of error are also discussed.

Seizures after decompressive hemicraniectomy for ischaemic stroke

OBJECTIVE

The risk of seizures after malignant middle cerebral artery (MCA) infarction with decompressive hemicraniectomy (DHC) is uncertain. Also unknown is how this complication influences survivors' recovery and quality of life.

METHODS

We retrospectively reviewed medical charts of all patients admitted to Harborview Medical Center between 1 January 2002 and 31 June 2011 for space-occupying MCA ischaemic stroke and who underwent DHC. Survivors and their surrogates were invited to participate in a telephone or in-person interview.

RESULTS

Fifty-five patients were followed for a median of 311 days (IQR 134-727). Twenty-seven patients (49%) had seizures, 25 (45%) developed epilepsy and 21 (38%) achieved moderate disability or better (modified Rankin Scale score ≤3) by 1 year after stroke onset. The only factor significantly associated with seizure occurrence was male gender. Median time from stroke to first seizure was 222 days, with a cluster of first seizures within weeks after cranioplasty; only two of the first seizures occurred right around the time of stroke onset. Follow-up time was significantly longer for patients with seizures (605 days, IQR 297-882) than for those without (221 days, IQR 104-335). Of the 20 patients interviewed, 12 achieved moderate disability or better, 15 experienced a seizure with 6 indicating the seizure was a major drawback. Regardless, all 20 would have chosen DHC again.

CONCLUSIONS

In this case series, patients were at high risk of developing seizures after malignant MCA stroke with DHC, especially after cranioplasty. Assuming these findings are replicated, means should be sought to reduce the occurrence of this complication.

Cerebral aneurysms treated with flow-diverting stents: computational models with intravascular blood flow measurements

BACKGROUND AND PURPOSE

Computational fluid dynamics modeling is useful in the study of the hemodynamic environment of cerebral aneurysms, but patient-specific measurements of boundary conditions, such as blood flow velocity and pressure, have not been previously applied to the study of flow-diverting stents. We integrated patient-specific intravascular blood flow velocity and pressure measurements into computational models of aneurysms before and after treatment with flow-diverting stents to determine stent effects on aneurysm hemodynamics.

MATERIALS AND METHODS

Blood flow velocity and pressure were measured in peri-aneurysmal locations by use of an intravascular dual-sensor pressure and Doppler velocity guidewire before and after flow-diverting stent treatment of 4 unruptured cerebral aneurysms. These measurements defined inflow and outflow boundary conditions for computational models. Intra-aneurysmal flow rates, wall shear stress, and wall shear stress gradient were calculated.

RESULTS

Measurements of inflow velocity and outflow pressure were successful in all 4 patients. Computational models incorporating these measurements demonstrated significant reductions in intra-aneurysmal wall shear stress and wall shear stress gradient and a trend in reduced intra-aneurysmal blood flow.

CONCLUSIONS

Integration of intravascular dual-sensor guidewire measurements of blood flow velocity and blood pressure provided patient-specific computational models of cerebral aneurysms. Aneurysm treatment with flow-diverting stents reduces blood flow and hemodynamic shear stress in the aneurysm dome.

Incidence of microemboli and correlation with platelet inhibition in aneurysmal flow diversion

Flow-diverting stents have been associated with embolic and hemorrhagic complications, but the rate of procedure-related microemboli is unknown. Using transcranial Doppler sonography, we measured the rate of microemboli in 23 patients treated with flow-diverting stents. Patients received preprocedural dual antiplatelet medications and intraprocedural heparinization. Point-of-care platelet reactivity testing was performed before the procedure, and nonresponders (>213 P2Y12/ADP receptor reactivity units) received additional thienopyridine. Transcranial Doppler sonography was performed within 12-24 hours. Microemboli were detected in 3 patients (13%), 2 of whom were initially nonresponders. There was no association between the presence of microemboli and procedural or neurologic complications, aneurysm size, number of stents, or procedure time. Eight procedures (34.8%) required additional thienopyridine for inadequate platelet inhibition, and 3 required further treatment for persistent nonresponse to point-of-care platelet reactivity testing. There were 6 technical and 2 postoperative complications; none were associated with inadequate platelet inhibition or microemboli. The combination of routine point-of-care platelet reactivity testing and postprocedural microembolic monitoring may help identify patients at risk for thromboembolic complications after flow-diverting stents.

The role of metabolic syndrome, adiposity, and inflammation in physical performance in the Health ABC Study

BACKGROUND

Metabolic syndrome (MetS) and functional limitation have been linked, but whether and how specific components of MetS and associated factors, such as inflammation, drive this relationship is unknown.

METHODS

Data are from 2,822 men and women, aged 70-79 years, participating in the Health, Aging, and Body Composition (Health ABC) study and followed for 5 years. Presence of MetS at baseline was defined according to the National Cholesterol Education Program Adult Treatment Panel III guidelines. Interleukin-6, C-reactive protein, and body fat mass were measured at baseline. Measures of physical performance, including 400-m walk time, 20-m walking speed, and the Health ABC physical performance battery (PPB) were obtained at baseline and examination years 2, 4, and 6.

RESULTS

A total of 1,036 (37%) individuals met criteria for MetS. MetS was associated with poorer physical performance at baseline. Effect estimates between MetS and gait speed, and components of the Health ABC PPB (standing balance and repeated sit-to-stand performance) were modestly attenuated after adjustment for inflammation. All associations were attenuated to nonsignificance after adding total body fat mass to the model. Longitudinal analyses yielded similar results. Individual MetS component analysis revealed that abdominal obesity explained the largest fraction of the variation in physical performance.

CONCLUSIONS

Although inflammatory biomarkers partially accounted for the relationship between MetS and aspects of physical performance, overall findings implicate adiposity as the primary factor explaining poorer physical performance in older adults with MetS.

Endovascular management of cerebral bypass graft problems: an analysis of technique and results

BACKGROUND AND PURPOSE

Cerebral bypass grafts may develop generalized graft narrowing or focal stenosis during the perioperative period or later. Endovascular techniques such as PTA and stent placement of graft vessels are potential treatment options. Our objective was to review the safety, indications, technique, and results of endovascular management of graft problems.

MATERIALS AND METHODS

All patients with cerebral bypass procedures by using graft vessels from 2005 to 2009 were identified from a prospective registry and were studied retrospectively. Patient characteristics, bypass procedures, indications for endovascular interventions, graft patency, and clinical outcomes were reviewed from medical charts and imaging records.

RESULTS

A total of 79 patients underwent bypass procedures by using graft vessels. Seven patients of this group underwent endovascular interventions for the treatment of graft narrowing. Four of the 7 patients were treated for graft narrowing in the perioperative period (<1 month) with PTA; and 3 of the 7 patients, for late stenosis, 2 with PTA alone and 1 with PTA followed by stent placement. All procedures were immediately successful in improving flow through the graft. In late stenosis, PTA alone provided temporary improvement followed by recurrence, whereas PTA with a stent procedure was effective in the 1 patient long term.

CONCLUSIONS

PTA is safe and effective in the management of graft spasm in the perioperative period. For late graft stenosis, PTA alone provides only temporary respite, while PTA with stent placement may be an effective solution.

Genetic variation near IRS1 associates with reduced adiposity and an impaired metabolic profile

Genome-wide association studies have identified 32 loci influencing body mass index, but this measure does not distinguish lean from fat mass. To identify adiposity loci, we meta-analyzed associations between ∼2.5 million SNPs and body fat percentage from 36,626 individuals and followed up the 14 most significant (P < 10(-6)) independent loci in 39,576 individuals. We confirmed a previously established adiposity locus in FTO (P = 3 × 10(-26)) and identified two new loci associated with body fat percentage, one near IRS1 (P = 4 × 10(-11)) and one near SPRY2 (P = 3 × 10(-8)). Both loci contain genes with potential links to adipocyte physiology. Notably, the body-fat-decreasing allele near IRS1 is associated with decreased IRS1 expression and with an impaired metabolic profile, including an increased visceral to subcutaneous fat ratio, insulin resistance, dyslipidemia, risk of diabetes and coronary artery disease and decreased adiponectin levels. Our findings provide new insights into adiposity and insulin resistance.

Associations of visceral and liver fat with the metabolic syndrome across the spectrum of obesity: the AGES-Reykjavik study

Visceral adipose tissue (VAT) is a key pathogenic fat depot in the metabolic syndrome (MetS), but liver fat (LF) may also play an important role. We evaluated associations of VAT and LF with MetS in normal weight, overweight, and obese men and women (BMI <25, 25-29.9, and ≥30 kg/m2, respectively). This analysis included 2,495 participants from the Age, Gene/Environment Susceptibility (AGES)-Reykjavik study with computed tomography measurements for VAT and LF. MetS was defined by ≥3 of the following: larger abdominal circumference, hypertension, elevated triglyceride (TG), low high-density lipoprotein (HDL), impaired fasting glucose (IFG), and microalbuminuria. We estimated the odds of MetS per 1-s.d. increase in VAT and LF, adjusting for key covariates. VAT was associated with an increased odds of MetS in normal weight, overweight, and obese women (odds ratios (OR) = 2.78, 1.63, and 1.43, respectively; all P < 0.01) that diminished in magnitude with increasing BMI (VAT × BMI class interaction P < 0.001). In men, VAT was related to MetS only among the overweight (OR = 1.69, P < 0.01). LF was associated with MetS in the overweight and obese groups in women (OR = 1.38 and 1.45; both P < 0.001) and in men (OR = 1.38, P = 0.01; and OR = 1.27, P = 0.10), but not in the normal weight groups. These BMI-specific relationships persisted when both fat depots were included in the model. VAT and LF were associated with MetS independently of each other, and these relationships were modified by BMI class such that, VAT was the more important depot at lower levels of obesity and LF at higher levels. Importantly, fatty liver may be a novel metabolic risk factor in overweight and obese individuals.

Body fat distribution and inflammation among obese older adults with and without metabolic syndrome

The protective mechanisms by which some obese individuals escape the detrimental metabolic consequences of obesity are not understood. This study examined differences in body fat distribution and adipocytokines in obese older persons with and without metabolic syndrome. Additionally, we examined whether adipocytokines mediate the association between body fat distribution and metabolic syndrome. Data were from 729 obese men and women (BMI ≥ 30 kg/m(2)), aged 70-79 participating in the Health, Aging and Body Composition (Health ABC) study. Thirty-one percent of these obese men and women did not have metabolic syndrome. Obese persons with metabolic syndrome had significantly more abdominal visceral fat (men: P = 0.04; women: P < 0.01) and less thigh subcutaneous fat (men: P = 0.09; women: P < 0.01) than those without metabolic syndrome. Additionally, those with metabolic syndrome had significantly higher levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and plasminogen activator inhibitor-1 (PAI-1) than individuals without metabolic syndrome. Per standard deviation higher in visceral fat, the likelihood of metabolic syndrome significantly increased in women (odds ratio (OR): 2.16, 95% confidence interval (CI): 1.59-2.94). In contrast, the likelihood of metabolic syndrome decreased in both men (OR: 0.56, 95% CI: 0.39-0.80) and women (OR: 0.49, 95% CI: 0.34-0.69) with each standard deviation higher in thigh subcutaneous fat. These associations were partly mediated by adipocytokines; the association between thigh subcutaneous fat and metabolic syndrome was no longer significant in men. In summary, metabolically healthy obese older persons had a more favorable fat distribution, characterized by lower visceral fat and greater thigh subcutaneous fat and a more favorable inflammatory profile compared to their metabolically unhealthy obese counterparts.

Factors related to the selection of surgical versus percutaneous revascularization in diabetic patients with multivessel coronary artery disease in the BARI 2D (Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes) trial

OBJECTIVES

We evaluated demographic, clinical, and angiographic factors influencing the selection of coronary artery bypass graft (CABG) surgery versus percutaneous coronary intervention (PCI) in diabetic patients with multivessel coronary artery disease (CAD) in the BARI 2D (Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes) trial.

BACKGROUND

Factors guiding selection of mode of revascularization for patients with diabetes mellitus and multivessel CAD are not clearly defined.

METHODS

In the BARI 2D trial, the selected revascularization strategy, CABG or PCI, was based on physician discretion, declared independent of randomization to either immediate or deferred revascularization if clinically warranted. We analyzed factors favoring selection of CABG versus PCI in 1,593 diabetic patients with multivessel CAD enrolled between 2001 and 2005.

RESULTS

Selection of CABG over PCI was declared in 44% of patients and was driven by angiographic factors including triple vessel disease (odds ratio [OR]: 4.43), left anterior descending stenosis >or=70% (OR: 2.86), proximal left anterior descending stenosis >or=50% (OR: 1.78), total occlusion (OR: 2.35), and multiple class C lesions (OR: 2.06) (all p < 0.005). Nonangiographic predictors of CABG included age >or=65 years (OR: 1.43, p = 0.011) and non-U.S. region (OR: 2.89, p = 0.017). Absence of prior PCI (OR: 0.45, p < 0.001) and the availability of drug-eluting stents conferred a lower probability of choosing CABG (OR: 0.60, p = 0.003).

CONCLUSIONS

The majority of diabetic patients with multivessel disease were selected for PCI rather than CABG. Preference for CABG over PCI was largely based on angiographic features related to the extent, location, and nature of CAD, as well as geographic, demographic, and clinical factors. (Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes [BARI 2D]; NCT00006305).

Transcranial access using fluoroscopic flat panel detector CT navigation

FPCT and navigation software on contemporary fluoroscopic units perform imaging of a quality comparable with conventional CT. They can accurately guide percutaneous procedures, providing live instrument visualization and the capability to re-image without patient transfer. FPCT navigation was used in the placement of a ventricular drain in a 62-year-old woman for subarachnoid-related hydrocephalus by using an otherwise standard bedside technique. Ventriculostomy catheter placement was technically successful without complication with a catheter at the foramen of Monro.

Intraoperative angiography for hunterian ligation of a recurrent basilar aneurysm

Cerebral aneurysms often recur after selective endovascular treatment with detachable coils and are usually treated by recoiling. Sometimes, however, surgical treatment is required, and application of the clip can be difficult. Evacuation of embolic material risks injuring eloquent structures or perforators, especially in the posterior circulation. In such cases parent vessel occlusion for reversal of flow might be an option. If collateral flow is adequate, an additional bypass is not required. When using this technique, known as Hunterian ligation, intraoperative monitoring such as electrophysiological monitoring and intraoperative angiography can be of great help and are advisable. We describe this procedure and related intraoperative considerations in one case report.

Effects of heart failure and diabetes mellitus on long-term mortality after coronary revascularization (from the BARI Trial)

This study evaluated the effect of heart failure (HF) and ejection fraction (EF) at baseline on long-term cardiac mortality in patients undergoing coronary revascularization and investigated the effect of diabetes mellitus (DM) on mortality. We evaluated long-term outcomes of patients without HF, HF and a preserved EF, and HF and a decreased EF who underwent revascularization with percutaneous transluminal coronary angioplasty or coronary artery bypass graft surgery after enrollment in the Bypass Angioplasty Revascularization Investigation (BARI) trial. Ten years after initial revascularization, cumulative rates of freedom from cardiac death were 90% in patients without HF, 75% in patients with HF and a preserved EF, and 59% in patients with HF and a decreased EF (p <0.001, 3-way comparison). In diabetic patients with HF and a preserved EF, there was a significant increase in cardiac mortality compared with patients without HF (p <0.001); however, this relation was not seen in patients without DM. In conclusion, patients with HF and a preserved EF have increased mortality over 10 years compared with those without HF. Only in patients with DM did HF with preserved EF confer additional risk.

The effect of coronary artery bypass grafting on specific causes of long-term mortality in the Bypass Angioplasty Revascularization Investigation

OBJECTIVES

We sought to examine the effect of revascularization with coronary artery bypass grafting on specific causes of death in the Bypass Angioplasty Revascularization Investigation cohort. Although the effect of coronary revascularization on long-term mortality has been previously described, there are limited data describing its effect on specific causes of death in patients with coronary artery disease. Evaluation of cause of death might help elucidate disease mechanisms and be useful for developing treatment strategies.

METHODS

In the Bypass Angioplasty Revascularization Investigation randomized trial and registry, 3610 patients underwent initial revascularization with coronary artery bypass grafting or balloon angioplasty and were followed for an average of 7.7 years. Causes of all deaths were classified by an independent committee.

RESULTS

Among 3610 revascularized patients, 2239 underwent coronary artery bypass grafting as an initial or subsequent procedure. Over 7.7 years of follow-up, 3% of all patients died of sudden cardiac death, 3% died of myocardial infarction-related death, 2% died of congestive heart failure and other cardiac causes, and 9% died of noncardiac causes. Coronary artery bypass grafting (vs no coronary artery bypass grafting) was associated with a significantly lower risk of sudden cardiac death (relative risk, 0.60; P = .01) but was not significantly associated with any other causes of long-term mortality.

CONCLUSIONS

In the Bypass Angioplasty Revascularization Investigation coronary artery bypass grafting significantly decreased the risk of sudden cardiac death but not any other cause of long-term mortality. Because major risk factors for sudden cardiac death have historically favored a revascularization strategy of coronary artery bypass grafting over angioplasty, evaluation of the current practice of extending angioplasty as an alternative to coronary artery bypass grafting in similar high-risk subgroups is paramount.

Spontaneous ventriculostomy in a patient with obstructive hydrocephalus

BACKGROUND

Spontaneous ventriculostomy related to progressive obstructive hydrocephalus is rare. Radiologic demonstration of such a phenomenon can be delineated with magnetic resonance imaging (MRI) and cine MRI.

CASE PRESENTATION

A 59-year-old woman with a known tectal glioma and symptoms of chronic hydrocephalus developed progressively worsening headaches. During follow-up, she noted spontaneous relief of her headaches. Follow-up cine MRI demonstrated a spontaneous ventriculostomy via the floor of the third ventricle.

INTERPRETATION

Clinicians should be aware of spontaneous ventriculostomy demonstrable on cine MRI because it may obviate the need for a CSF diversion procedure.

Sensitivity of routine intensive care unit surveillance for detecting myocardial ischemia*

OBJECTIVE

To assess the effectiveness of routine intensive care unit surveillance compared with frequent 12-lead electrocardiogram monitoring for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia in vascular surgery patients.

DESIGN

Prospective cohort trial.

SETTING

Intensive care unit.

PARTICIPANTS

We studied 149 patients undergoing elective infrainguinal or aortic vascular surgery who were admitted to the intensive care unit postoperatively.

INTERVENTIONS

Patients were simultaneously monitored with a 10-electrode/12-lead electrocardiogram obtained every 2 mins (criterion standard) and routine intensive care unit surveillance that included standard monitoring (five-electrode/two-lead electrocardiogram with ST segment trends and routine 12-lead electrocardiogram) and clinical assessment for detecting myocardial ischemia. The results of the criterion standard were not available to the caregivers.

MEASUREMENTS AND MAIN RESULTS

We measured the ability of routine intensive care unit surveillance to detect the first 20 mins of electrocardiogram evidence suggestive of myocardial ischemia, defined as ST segment depression or elevation of >/=1 mm in two consecutive leads, during the first postoperative day. Seventeen patients (11%) had electrocardiogram evidence suggestive of prolonged myocardial ischemia, the majority of which occurred in leads V2-V4. The sensitivity of routine intensive care unit surveillance for detecting the first episode of electrocardiogram evidence suggestive of prolonged myocardial ischemia in a patient was 12% (95% confidence interval, 7-17%), and the specificity was 98% (95% confidence interval, 95-100%) with a positive predictive value of 40% (95% confidence interval, 32-48%), a negative predictive value of 90% (95% confidence interval, 85-94%), a positive likelihood ratio of 6, and a negative likelihood ratio of 1. The sensitivity of routine intensive care unit surveillance for detecting all episodes was 3% (95% confidence interval, 2-3%) and the specificity 99% (95% confidence interval, 99-100%) per 20-min monitoring interval, with a positive predictive value of 17% (95% confidence interval, 16-18%), negative predictive value of 95% (95% confidence interval, 95-96%), positive likelihood ratio of 3, and negative likelihood ratio of 1.

CONCLUSIONS

Routine intensive care unit surveillance has low sensitivity for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia compared with frequent 12-lead electrocardiograms. Because detecting electrocardiogram evidence suggestive of prolonged postoperative myocardial ischemia is important, physicians should consider alternative strategies to detect myocardial ischemia.

Cardiac troponin I predicts short-term mortality in vascular surgery patients

BACKGROUND

Cardiac troponin I (cTnI) is a highly sensitive and specific marker for myocardial injury that predicts outcomes in patients with acute coronary syndromes. Cardiovascular complications are the leading cause of morbidity and mortality in patients who have undergone vascular surgery. However, postoperative surveillance with cardiac enzymes is not routinely performed in these patients. We evaluated the association between postoperative cTnI levels and 6-month mortality and perioperative myocardial infarction (MI) after vascular surgery.

METHODS AND RESULTS

Two hundred twenty-nine patients having aortic or infrainguinal vascular surgery or lower extremity amputation were included in this study. Blood samples were analyzed for cTnI immediately after surgery and the mornings of postoperative days 1, 2, and 3. An elevated cTnI was defined as serum concentrations >1.5 ng/mL in any of the 4 samples. Twenty-eight patients (12%) had postoperative cTnI >1.5 ng/mL, which was associated with a 6-fold increased risk of 6-month mortality (adjusted OR, 5.9; 95% CI, 1.6 to 22.4) and a 27-fold increased risk of MI (OR, 27.1; 95% CI, 5.2 to 142.7). Furthermore, we observed a dose-response relation between cTnI concentration and mortality. Patients with cTnI >3.0 ng/mL had a significantly greater risk of death compared with patients with levels < or =0.35 ng/mL (OR, 4.9; 95% CI, 1.3 to 19.0).

CONCLUSIONS

Routine postoperative surveillance for cTnI is useful for identifying patients who have undergone vascular surgery who have an increased risk for short-term mortality and perioperative MI. Further research is needed to determine whether intervention in these patients can improve outcome.

Dehydroascorbic acid, a blood-brain barrier transportable form of vitamin C, mediates potent cerebroprotection in experimental stroke

Neuronal injury in ischemic stroke is partly mediated by cytotoxic reactive oxygen species. Although the antioxidant ascorbic acid (AA) or vitamin C does not penetrate the blood-brain barrier (BBB), its oxidized form, dehydroascorbic acid (DHA), enters the brain by means of facilitative transport. We hypothesized that i.v. DHA would improve outcome after stroke because of its ability to cross the BBB and augment brain antioxidant levels. Reversible or permanent focal cerebral ischemia was created by intraluminal middle cerebral artery occlusion in mice treated with vehicle, AA, or DHA (40, 250, or 500 mg/kg), either before or after ischemia. Given before ischemia, DHA caused dose-dependent increases in postreperfusion cerebral blood flow, with reductions in neurological deficit and mortality. In reperfused cerebral ischemia, mean infarct volume was reduced from 53% and 59% in vehicle- and AA-treated animals, respectively, to 15% in 250 mg/kg DHA-treated animals (P < 0.05). Similar significant reductions occurred in nonreperfused cerebral ischemia. Delayed postischemic DHA administration after 15 min or 3 h also mediated improved outcomes. DHA (250 mg/kg or 500 mg/kg) administered at 3 h postischemia reduced infarct volume by 6- to 9-fold, to only 5% with the highest DHA dose (P < 0.05). In contrast, AA had no effect on infarct volumes, mortality, or neurological deficits. No differences in the incidence of intracerebral hemorrhage occurred. Unlike exogenous AA, DHA confers in vivo, dose-dependent neuroprotection in reperfused and nonreperfused cerebral ischemia at clinically relevant times. As a naturally occurring interconvertible form of AA with BBB permeability, DHA represents a promising pharmacological therapy for stroke based on its effects in this model of cerebral ischemia.

Human Taf(II)130 is a coactivator for NFATp

NFATp is one member of a family of transcriptional activators that regulate the expression of cytokine genes. To study mechanisms of NFATp transcriptional activation, we established a reconstituted transcription system consisting of human components that is responsive to activation by full-length NFATp. The TATA-associated factor (TAF(II)) subunits of the TFIID complex were required for NFATp-mediated activation in this transcription system, since TATA-binding protein (TBP) alone was insufficient in supporting activated transcription. In vitro interaction assays revealed that human TAF(II)130 (hTAF(II)130) and its Drosophila melanogaster homolog dTAF(II)110 bound specifically and reproducibly to immobilized NFATp. Sequences contained in the C-terminal domain of NFATp (amino acids 688 to 921) were necessary and sufficient for hTAF(II)130 binding. A partial TFIID complex assembled from recombinant hTBP, hTAF(II)250, and hTAF(II)130 supported NFATp-activated transcription, demonstrating the ability of hTAF(II)130 to serve as a coactivator for NFATp in vitro. Overexpression of hTAF(II)130 in Cos-1 cells inhibited NFATp activation of a luciferase reporter. These studies demonstrate that hTAF(II)130 is a coactivator for NFATp and represent the first biochemical characterization of the mechanism of transcriptional activation by the NFAT family of activators.

Postischemic cerebrovascular E-selectin expression mediates tissue injury in murine stroke

BACKGROUND AND PURPOSE

Although the deleterious role of several proinflammatory mediators, including P-selectin, in reperfused stroke is well established, the role of E-selectin has not been fully characterized.

METHODS

E-selectin mRNA expression was studied at 4, 10, and 24 hours after reperfusion with reverse transcription and polymerase chain reaction in mice (n=18) subjected to transient intraluminal middle cerebral artery occlusion (MCAO). Mice received intravenous injection with anti-E-selectin monoclonal antibody (10, 35, or 50 microg), nonimmune IgG, or vehicle immediately before MCAO and 90 minutes later (n=85). Others received anti-E-selectin antibody 3 or 6 hours after MCAO (n=32). Myeloperoxidase activity was measured in sham-operated mice and after 10 hours of reperfusion in saline-, nonimmune IgG-, or anti-E-selectin IgG-treated cohorts (n=17). Serial cerebral blood flow was measured with laser-Doppler flowmetry, and outcomes were assessed by neurological deficits and infarct volumes with the use of planimetric analysis of triphenyltetrazolium chloride-stained sections.

RESULTS

Upregulated E-selectin expression occurred in the ischemic cerebral vasculature within 4 hours of reperfusion and persisted for 24 hours. Anti-E-selectin antibody increased ischemic cortical cerebral blood flow up to 2.6-fold (P:<0.05). In addition to dose-dependent reductions in neurological deficits (P:<0.05), mortality, and infarct volumes (P:<0.01 for 35 and 50 microg), anti-E-selectin treatment reduced cerebral neutrophil accumulation (P:<0.05) and was neuroprotective even if delayed until 3 hours after ischemia (P:<0. 05).

CONCLUSIONS

These findings establish a functional role for E-selectin in the pathogenesis of tissue injury after cerebral ischemia and reperfusion and suggest that E-selectin blockade may be clinically useful in the treatment of reperfused stroke.

Lumbar sympathetic block for sympathetically maintained pain: changes in cutaneous temperatures and pain perception

Lumbar sympathetic block (LSB) is used in the management of sympathetically maintained pain states. We characterized cutaneous temperature changes over the lower extremities after LSB. Additionally, we examined the effects of iohexol, a radio-opaque contrast medium, on temperature changes and pain relief. After institutional review board approval and written, informed consent, 28 LSBs were studied in 17 patients. Iohexol or normal saline was injected in a randomized, double-blinded fashion before bupivacaine. Lower extremity cutaneous temperatures were measured. Pain, allodynia, interference with daily function, and perceived pain relief were reported in a subset of 15 LSBs for 1 wk after the block. The distal lower extremity ipsilateral to the LSB had the greatest magnitude (8.7 degrees +/- 0.8 degrees C) and rate (1.1 degrees +/- 0.2 degrees C/min) of temperature change. The great toe temperature was within 3 degrees C of core temperature within 35 min after LSB. There were no differences in temperature change between the groups. The iohexol group had greater relief of pain until the morning of the first postblock day (P = 0.002) and longer perceived relief of pain (P = 0.01). The maximum temperature of the great toe correlated with allodynia relief (P = 0.0007). Thus clinicians should expect ipsilateral toe temperatures to increase to within approximately 3 degrees C of core temperature. Iohexol does not alter the efficacy of LSB and may improve relief of symptoms. The magnitude of temperature change may predict relief of allodynia.

IMPLICATIONS

Cutaneous toe temperatures approaching core temperature provide a useful monitor of lumbar sympathetic block and may predict relief of sympathetically maintained pain. Iohexol will not compromise temperature changes or pain relief.

The accuracy and precision of body temperature monitoring methods during regional and general anesthesia

We tested the hypotheses that accuracy and precision of available temperature monitoring methods are different between spinal anesthesia (SA) and general anesthesia (GA), and that patients receiving SA are at equal risk for hypothermia as those receiving GA. Patients scheduled for radical retropubic prostatectomy were enrolled. Either GA (n = 16) or SA (n = 16) was given according to patient and clinician preference. Temperatures were monitored with thermocouple probes at the tympanic membrane, axilla, rectum, and forehead skin surface. Tympanic temperatures were also measured with an infrared device, and forehead skin temperatures were monitored with two brands of liquid crystal thermometer strips. Accuracy and precision of these monitoring methods were determined by using tympanic membrane temperature, measured by thermocouple, as the reference core temperature (T(c)). At the end of surgery, T(c) was similar between SA (35.0 +/- 0.1 degrees C) and GA (35.2 +/- 0.1 degrees C) (P = 0.44). Accuracy and precision of each temperature monitoring method were similar between SA and GA. Rectal temperature monitoring offered the greatest combination of accuracy and precision. All other methods underestimated T(c). These findings suggest that patients receiving SA or GA are at equal and significant risk for hypothermia, and should have their temperatures carefully monitored, recognizing that most monitoring methods underestimate T(c).

IMPLICATIONS

Body temperature should be monitored during spinal anesthesia because patients are at significant risk for hypothermia. Rectal temperature is a valid method of measuring core temperature, whereas other methods tend to underestimate true core temperature.

Safety and efficacy of fixed-dose heparin in carotid endarterectomy

OBJECTIVE

Although fixed dosage of heparin is frequently used during vascular surgery, there are very few studies that document the appropriateness of this type of dosing. We have undertaken a prospective study to determine the physiological response to a fixed dose of heparin, using a conventional measure of anticoagulation, and have correlated this measure with complications.

METHODS

We studied 140 consecutive patients undergoing elective carotid endarterectomy. Serial activated clotting times (ACT values) were obtained in duplicate before administration of heparin, 15 minutes after application of a carotid artery cross-clamp, and 1 hour after administration of 5000 U of heparin by intravenous bolus. Postoperatively, patients were assessed for new neurological deficits (transient ischemic attack and stroke) and neck hematomas. A battery of neuropsychometric tests was performed in 49 patients at baseline and on the day after carotid endarterectomy to identify subtle new neurological deficits.

RESULTS

ACT values were found to be highly reproducible, with less than a 1.5% difference between duplicate baseline samples. Although all patients received 5000 U of heparin, the dose received per kilogram of body weight varied considerably (44-116 U/kg), as did ACT values at both 15 minutes (178-423 s) and 1 hour (173-390 s). Nevertheless, there was a significant correlation between heparin dose per kilogram and ACT values at 15 minutes (r = 0.45) and at 1 hour (r = 0.38) postinfusion, as well as ACT ratios (final ACT/initial ACT) at 15 minutes (r = 0.43) and at 1 hour (r = 0.34) after heparin bolus. Eight patients (5.7%) developed postoperative wound hematomas, one of which (0.7%) required reoperation. No patient had a stroke, but one patient had a transient ischemic attack, and 19 (39%) of 49 patients demonstrated significant early postoperative neuropsychometric deficits. Although the incidence of neck hematoma was not influenced by the heparin dose (P = 0.23), the ACT value at 15 minutes (P = 0.71) or 1 hour (P = 0.61), or the ACT ratio (P = 0.68), the only severe hematoma requiring reoperation occurred when the maximal ACT value was more than 400 seconds. Although performance on neuropsychometric tests did not appear to be statistically influenced by heparin dosing, the ACT value, or the degree of ACT elevation, there was a trend for deficits to be associated with lower heparin doses.

CONCLUSION

Fixed heparin dosing achieves safe and efficacious anticoagulation in the great majority of patients having carotid endarterectomy, with 5000 U expected to result in 15-minute and 1-hour ACT values of 175 to 425 seconds and 170 to 390 seconds, respectively. Although weight-based heparin dosing may reduce the incidence of subtle complications (hematoma formation or decline on neuropsychometric tests) and may result in more predictable 15-minute and 1-hour ACT values (85 U/kg; 225-375 and 200-340 s, respectively), no statistically compelling clinical advantage could be demonstrated. Therefore, either weight-based or fixed dosing is acceptable, with both obviating the need for routine pre-clamp ACT confirmation, thereby saving operative time and expense.

Titration of postischemic cerebral hypoperfusion by variation of ischemic severity in a murine model of stroke

OBJECTIVE

Murine models using intraluminal occluding sutures to establish transient focal cerebral ischemia are becoming increasingly widespread, because of advances in transgenic technology and the advent of cerebroprotective strategies to ameliorate postischemic cerebrovascular no-reflow. We hypothesize that the degree of postischemic hypoperfusion is directly related to the severity of the initial ischemic insult.

METHODS

Transient ischemia of 45-minute duration was produced using middle cerebral artery occlusion with 10-0 (n = 5), 9-0 (n = 5), 8-0 (n = 6), 7-0 (n = 8), 6-0 (n = 30), or 5-0 (n = 5) sutures. In separate experiments, transient vessel occlusion with 6-0 sutures was performed for 15 (n = 17), 30 (n = 16), or 45 (n = 30) minutes. Sequential laser Doppler measurements of relative cerebral blood flow were obtained, and stroke severity was assessed using neurological deficit scores and infarction volumes.

RESULTS

Although relative cerebral blood flow at the time of occlusion and 24 hours thereafter was diminished in parallel with increasing suture diameters, only the use of larger sutures resulted in postischemic no-reflow. As the suture diameter was increased, the resultant reflow was decreased and the stroke outcome worsened. A more than twofold increase in infarction volume (8.0 +/- 3 versus 19.7 +/- 3%, P < 0.05) resulted when ischemia duration was increased from 30 to 45 minutes.

CONCLUSION

Titration of the initial ischemic insult leads to corresponding variations in the magnitude of postischemic no-reflow and tissue damage. Therefore, critical control of the severity of the initial injury in studies using intraluminal suture occlusion is warranted.

Neuronal protection in stroke by an sLex-glycosylated complement inhibitory protein

Glycoprotein adhesion receptors such as selectins contribute to tissue injury in stroke. Ischemic neurons strongly expressed C1q, which may target them for complement-mediated attack or C1qRp-mediated clearance. A hybrid molecule was used to simultaneously inhibit both complement activation and selectin-mediated adhesion. The extracellular domain of soluble complement receptor-1 (sCR1) was sialyl Lewis x glycosylated (sCR1sLex) to inhibit complement activation and endothelial-platelet-leukocyte interactions. sCR1 and sCR1sLex colocalized to ischemic cerebral microvessels and C1q-expressing neurons, inhibited neutrophil and platelet accumulation, and reduced cerebral infarct volumes. Additional benefit was conferred by sialyl Lewis x glycosylation of the unmodified parent sCR1 molecule.

Targeted inhibition of intrinsic coagulation limits cerebral injury in stroke without increasing intracerebral hemorrhage

Agents that restore vascular patency in stroke also increase the risk of intracerebral hemorrhage (ICH). As Factor IXa is a key intermediary in the intrinsic pathway of coagulation, targeted inhibition of Factor IXa-dependent coagulation might inhibit microvascular thrombosis in stroke without impairing extrinsic hemostatic mechanisms that limit ICH. A competitive inhibitor of native Factor IXa for assembly into the intrinsic Factor X activation complex, Factor IXai, was prepared by covalent modification of the Factor IXa active site. In a modified cephalin clotting time assay, in vivo administration of Factor IXai caused a dose-dependent increase in time to clot formation (3.6-fold increase at the 300 micrograms/kg dose compared with vehicle-treated control animals, P < 0.05). Mice given Factor IXai and subjected to middle cerebral artery occlusion and reperfusion demonstrated reduced microvascular fibrin accumulation by immunoblotting and immunostaining, reduced 111In-labeled platelet deposition (42% decrease, P < 0.05), increased cerebral perfusion (2.6-fold increase in ipsilateral blood flow by laser doppler, P < 0.05), and smaller cerebral infarcts than vehicle-treated controls (70% reduction, P < 0.05) based on triphenyl tetrazolium chloride staining of serial cerebral sections. At therapeutically effective doses, Factor IXai was not associated with increased ICH, as opposed to tissue plasminogen activator (tPA) or heparin, both of which significantly increased ICH. Factor IXai was cerebroprotective even when given after the onset of stroke, indicating that microvascular thrombosis continues to evolve (and may be inhibited) even after primary occlusion of a major cerebrovascular tributary.

Cigarette smoking and the development and rupture of cerebral aneurysms in a mixed race population: implications for population screening and smoking cessation

BACKGROUND

Despite advances in the treatment of aneurysmal subarachnoid hemorhage (aSAH), major additional reductions in morbidity will require the identifications of unruptured aneurysms with a high propensity for bleeding. As screening the entire population is currently not cost-effective, risk factors for the presence of unruptured aneurysms must be identified, and if possible, these risk factors should be modified to reduce disease prevalence.

METHODS

To examine whether cigarette smoking independent of arterial hypertension is a risk factor for the development of cerebral aneurysms rather than just being associated with aSAH and to determine whether smoking cessation decreases this risk, we conducted a case-control study comparing the prevalence and degree of smoking in a consecutive series of patients undergoing surgery for ruptured or unruptured aneurysm with age-, sex-, race-, and geographically matched control subjects culled from the New York Healthy Heart Study.

RESULTS

Hypertension alone carries little additional risk for the development of ruptured or unruptured aneurysms. Smoking is a risk factor for not only aneurysmal subarachnoid hemorrhage (Relative Risk [RR]=2.83) but also aneurysm formation (RR=2.33). Coexistent hypertension increases the risk of smoking only minimally. Younger smokers are at threefold higher risk than middle-aged ones. Smoking cessation appears to reduce risk of aneurysmal rupture. The effect of smoking on aneurysm formation and rupture may be dose-dependent.

CONCLUSIONS

Together these data suggest that smoking, independent of hypertension, plays a critical role in aneurysm development, especially in younger patients, but that physiological mechanisms exist for repair of the damage induced by this toxic insult if cessation is possible.

Does poly-L-lysine coating of the middle cerebral artery occlusion suture improve infarct consistency in a murine model?

BACKGROUND AND PURPOSE

Rodent models of stroke that employ an intraluminal suture to cause focal cerebral ischemia are associated with some variability of resultant infarct volumes, thus requiring increased numbers of animals to determine significant differences between experimental groups. A recent modification of the occluding suture by coating with poly-L-lysine has been shown to create more uniform infarct volumes in rats.

METHODS

To evaluate the utility of this modification in murine models of both transient and permanent focal cerebral ischemia, male C57B16J mice were subjected to reversible middle cerebral artery occlusion (MCAo) for 45 minutes (n=42), or to permanent MCAo (n=25), with an intraluminal monofilament suture. Three types of sutures were used: untreated, partially coated, and completely coated with poly-L-lysine. Relative changes in regional cerebral blood flow, severity of neurological deficits, and infarct volumes were measured 24 hours after the ischemic injury.

RESULTS

Animals subjected to 45 minutes of temporary occlusion with completely coated poly-L-lysine sutures had infarct volumes of 13.8%+/-5% compared with infarct volumes of 7.2%+/-4% in those subjected to partially coated sutures and 22.4%+/-6% in the group occluded with untreated sutures (P=ns). Use of completely coated sutures resulted in significantly less reperfusion following suture removal. Control animals undergoing permanent occlusion with untreated sutures had infarct volumes of 17%+/-7% compared with 14.1%+/-5% using completely coated sutures and 6.5%+/-3% in animals with partially coated sutures (P=ns). There were no significant differences in cerebral blood flow between the experimental groups undergoing permanent MCAo.

CONCLUSIONS

Poly-L-lysine coating of intraluminal sutures does not increase the consistency of infarct volumes in a murine model of temporary/permanent MCAo. These findings are in marked contrast to findings in rats.

Inhibitors of sterol synthesis. Metabolism-based design and construction of a new analog of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one and its effects in cultured mammalian cells and in rats

3 beta-Hydroxy-5 alpha-cholest-8(14)-en-15-one (I) is a potent regulator of cholesterol metabolism. In the present study, the 7 alpha-methyl-25,26,26,26,27,27,27-heptafluoro analog (X) of I has been synthesized with the goal of blocking not only the side chain oxidation of I but also its conversion to cholesterol. X was prepared in seven steps from the known 7 alpha-methyl analog (IX) of I. Treatment of the acetate of IX with a mixture of trifluoroacetic anhydride, hydrogen peroxide, and sulfuric acid gave 3 beta-acetoxy-7 alpha-methyl-24-hydroxy-5 alpha-chol-8(14)-en-15-one (XII) in remarkably high (68%) yield. Dehydration of XII via the orthonitrophenylselenide to the 23-ene, followed by addition of (CF3)2CFI gave (23R)-3 beta-acetoxy-7 alpha-methyl-23-iodo-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one (XV). Reductive deiodination of XV with tributyltin hydride, followed by hydrolysis of the acetate gave 3 beta-hydroxy-7 alpha-methyl-25,26,26,26,27,27,27-heptafluoro-5 alpha-cholest-8(14)-en-15-one (X). The F7-7 alpha-methyl-15-ketosterol X lowered the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in CHO-K1 cells with a potency equivalent to that of I. X showed significant hypocholesterolemic action upon oral administration to rats, with a potency far in excess of the 7 alpha-methyl-15-ketosterol IX lacking the F7 substitution. In marked contrast to I, X showed little or no suppression of food consumption in rats. Upon oral administration of X to rats, low levels of X (relative to cholesterol), characterized by chromatographic and gas chromatography-mass spectrometric methodologies, were observed in serum, liver, and small intestine. No material was observed with the expected properties of F7-7-methylcholesterol (or potential intermediates in its possible formation from X). In contrast to I, X lowered serum cholesterol levels at dosages at which no effect on food consumption was observed.

Inhibitors of sterol synthesis: effects of a 7 alpha-alkyl analog of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15-one on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in cultured mammalian cells and on serum cholesterol levels and other parameters in rats

The 7 alpha-methyl analog (II) of 3 beta-hydroxy-5 alpha-cholest-8(14)-en-15- one (I) was prepared by chemical synthesis and evaluated with respect to its effects on HMG-CoA reductase activity in CHO-K1 cells and on serum cholesterol levels in rats. The 7 alpha-methyl substitution had no detectable effect on the potency of I in lowering HMG-CoA reductase activity in the cultured cells. In contrast, the 7 alpha-methyl substitution had a marked effect on the action of I in the suppression of food consumption in rats. Whereas II was less potent than I in lowering serum cholesterol levels in rats, it did so at dosage levels at which only slight or moderate effects on food consumption were observed. Full 1H and 13C-NMR assignments for II and intermediates in its synthesis have been presented. Conformational analysis, based on 1H-1H coupling constants, NMR shieldings and force-field calculations, indicated that the 7 alpha-methyl substitution had virtually no effect on the conformation of the 15-ketosterol apart from minor distortions of ring B.

Variant responses of mice to Borrelia burgdorferi depending on the site of intradermal inoculation

C3H/He mice inoculated intradermally at one of two sites with Borrelia burgdorferi responded differently to infection. Shoulder-inoculated mice developed spirochetemia, B. burgdorferi-specific antibody, and arthritis earlier than foot-inoculated mice. Lymphocyte populations derived from spleen tissue were elevated in the shoulder- but not the foot-inoculated mice, and those from lymph nodes were increased in both groups. Lymphocytes derived from blood and spleen tissue showed impaired proliferative responses to all mitogens for shoulder-inoculated mice only, whereas proliferation of lymph node cells was not affected, regardless of route. These results demonstrate that the site of initial B. burgdorferi inoculation is an important determinant in the pathogenesis of B. burgdorferi infection.