Microelectronic bioinstrumentation systems

The possibility of using RF fields to power biologically implanted transmitters used in biomedical experiments was investigated. This approach would be especially useful when animal subjects are strapped in chairs or confined in cages. A telemetry system using an external source of energy has the additional advantage of not being limited in operation by battery lifetime and can therefore operate for virtually infinite lengths of time. A description of a system based on this principle is given. Progress in the development of battery-driven transmitters is also reported, including an ingestible temperature telemetry system and a resistance-to-pulse frequency convertor for implantable temperature telemetry systems

Counting atoms in a deep optical microtrap

We demonstrate a method to count small numbers of atoms held in a deep, microscopic optical dipole trap by collecting fluorescence from atoms exposed to a standing wave of light that is blue detuned from resonance. While scattering photons, the atoms are also cooled by a Sisyphus mechanism that results from the spatial variation in light intensity. The use of a small blue detuning limits the losses due to light assisted collisions, thereby making the method suitable for counting several atoms in a microscopic volume

Evaluation of pressure transmission and intra-aneurysmal contents after endovascular repair using the Trivascular Enovus expanded polytetrafluoroethylene stent graft in a canine model of abdominal aortic aneurysm

ObjectiveEndotension has been defined as persistently increased pressure within the excluded sac of an abdominal aortic aneurysm (AAA) resulting in increasing aneurysm size after endovascular repair in the absence of endoleak. Devices that use expanded polytetrafluoroethylene (ePTFE) have been associated with the development of endotension and continued AAA enlargement. In this study, intra-aneurysmal pressure and aneurysm content were evaluated after endovascular repair with the Enovus ePTFE stent graft in a canine model.MethodsProsthetic ePTFE aneurysms, each containing a solid-state, strain-gauge pressure transducer, were implanted in the infrarenal aorta of 13 mongrel dogs (25-35 kg). A second pressure transducer was inserted into the native aorta for systemic arterial pressure measurement. The stent graft was then deployed to exclude the aneurysm via distal aortic access. Comparison was made among three distinct stent grafts: the Trivascular Enovus (nonporous ePTFE; four animals), the original Gore Excluder (porous ePTFE; five animals), and the Medtronic AneuRx (Dacron; four animals). Daily systemic and intra-AAA pressures were measured for 4 weeks. Intra-aneurysmal pressures were indexed to simultaneously measured systemic pressures. After 4 weeks, the aorta, the prosthetic aneurysm, and its contents were harvested, photographed, and processed for histologic investigation with hematoxylin and eosin and Masson trichrome staining.ResultsWithin 24 hours after exclusion, the mean arterial pressure and pulse pressure within the AAA sac tapered to less than 20% of systemic pressure for all three stent graft types. Throughout the postoperative period, significantly lower indexed intra-aneurysmal pressures were present in the Enovus- and AneuRx-treated aneurysms as compared with those treated with the original Excluder stent graft (0.05 ± 0.04, 0.16 ± 0.06, and 0.06 ± 0.03 for the Enovus, Excluder, and AneuRx, respectively). Histologic analysis of the Enovus-treated aneurysms demonstrated intraluminal content characterized almost entirely by erythrocytes and infrequent white blood cells without the fibrin organization—characteristics of acute or chronic thrombus. This contrasted with the content of the Excluder-treated aneurysms, which contained poorly organized fibrin deposition suggestive of acute thrombus, and of the AneuRx-treated aneurysms, which demonstrated mature, well-organized collagenous connective tissue.ConclusionsExclusion of the AAA with the Enovus stent graft resulted in nearly complete elimination of intra-aneurysmal pressure in this model. Histologic analysis of the aneurysm content further suggested complete exclusion, including elimination of circulating clotting factors and fibroblasts responsible for thrombus formation and reorganization. Ultimately, clinical evaluation will be necessary to demonstrate the effectiveness of this stent graft in preventing the development of endotension.Clinical RelevanceEndovascular aneurysm repair is an effective method for the treatment of abdominal aortic aneurysm (AAA) subjected to the unique complications of endoleak and endotension, the indirect pressurization of a sac in the absence of endoleak. In our model, AAA exclusion with the Enovus stent graft results in inhibition of fluid and serum transudation into the AAA sac, a corresponding prompt pressure decay profile, and near-complete elimination of intra-aneurysmal pressure. With the advent of implantable wireless pressure transducers, this research can be readily translated to the clinical setting. Future intraoperative and postoperative studies may help elucidate the clinical significance of pressure decay profiles in identifying successful AAA exclusion and monitoring for the development of endotension and its clinical sequelae

Periprocedural complication rates are equivalent between symptomatic and asymptomatic patients undergoing carotid angioplasty and stenting

Patients with neurologic symptoms who undergo carotid endarterectomy (CEA) have a higher incidence of stroke and death in the perioperative period than those with asymptomatic carotid disease. This study examines the outcomes of symptomatic and asymptomatic patients undergoing carotid stenting (CAS). From 2002 to 2006, 201 CAS procedures were performed in 193 patients (117 men, mean age 73 +/- 10 years), of whom 142 were for asymptomatic (AS) and 59 for symptomatic (S) disease. Preoperative neurologic symptoms included recent ipsilateral cerebrovascular accident (CVA, 29%), transient ischemic attack (50%), and amaurosis fugax (22%). There were 201 carotid stents placed (107 Acculink, 43 Wallstent, 23 Precise, 21 NexStent, 3 Exponent, 3 Xact, 1 Herculink) and 198 protection devices used (79 Accunet, 53 EPI Filterwire, 43 PercuSurge, 20 Angiogard, 3 EmboShield). Mean follow-up was 41 weeks. The groups were matched in terms of demographics and comorbidities (carotid artery disease, hypertension, hyperlipidemia, diabetes mellitus, peripheral vascular disease, smoking, and chronic obstructive pulmonary disease; p = nonsignificant [NS]). There was no significant difference in anatomic risk factors (neck irradiation, S 3%, AS 6%; prior CEA, S 14%, AS 14%; bovine arch, S 22%, AS 16%; p = NS), and the types of embolic protection devices and stents used were similar between groups. The mean percentages of preintervention carotid stenosis were equal (S 88%, AS 88%), and the technical success rate was 99%. Incidence rates of CVA (S 3.4%, AS 1.4%), myocardial infarction (S 1.7%, AS 1.4%), and death (S 0, AS 0.7%) were equivalent between groups (p = NS). CAS with cerebral protection can be performed safely in both symptomatic and asymptomatic patients. The presence of preoperative neurologic symptoms does not significantly increase the risk of adverse events in the perioperative period in this study