Browsing by Subject "Prosthesis Design"

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Open Access
Chronic in vivo testing of the Penn State infant ventricular assist device.
(ASAIO journal (American Society for Artificial Internal Organs : 1992), 2012-01) Weiss, William J; Carney, Elizabeth L; Clark, J Brian; Peterson, Rebecca; Cooper, Timothy K; Nifong, Thomas P; Siedlecki, Christopher A; Hicks, Dennis; Doxtater, Bradley; Lukic, Branka; Yeager, Eric; Reibson, John; Cysyk, Joshua; Rosenberg, Gerson; Pierce, William S
The Penn State Infant Ventricular Assist Device (VAD) is a 12-14 ml stroke volume pneumatically actuated pump, with custom Björk-Shiley monostrut valves, developed under the National Heart, Lung, and Blood Institute Pediatric Circulatory Support program. In this report, we describe the seven most recent chronic animal studies of the Infant VAD in the juvenile ovine model, with a mean body weight of 23.5 ± 4.1 kg. The goal of 4-6 weeks survival was achieved in five of seven studies, with support duration ranging from 5 to 41 days; mean 26.1 days. Anticoagulation was accomplished using unfractionated heparin, and study animals were divided into two protocol groups: the first based on a target activated partial thromboplastin time of 1.5-2 times normal, and a second group using a target thromboelastography R-time of two times normal. The second group required significantly less heparin, which was verified by barely detectable heparin activity (anti-Xa). In both groups, there was no evidence of thromboembolism except in one animal with a chronic infection and fever. Device thrombi were minimal and were further reduced by introduction of the custom valve. These results are consistent with results of adult VAD testing in animals and are encouraging given the extremely low levels of anticoagulation in the second group.
Open Access
Embolization of patent foramen ovale closure devices: incidence, role of imaging in identification, potential causes, and management.
(Tex Heart Inst J, 2013) Goel, Sachin S; Aksoy, Olcay; Tuzcu, E Murat; Krasuski, Richard A; Kapadia, Samir R
Transcatheter patent foramen ovale (PFO) closure is an alternative to antiplatelet or anticoagulative therapy in patients with cryptogenic stroke, and it is associated with a small incidence of periprocedural sequelae. Because embolization of PFO closure devices is a very rare procedural complication, data on its frequency, causes, and management are sparse. We sought to review the medical literature and the cases of PFO closure-device embolization at our institution with the aim of identifying likely problems and reporting potential solutions. Out of 310 adult patients who underwent transcatheter PFO closure from June 2002 through April 2011, there were 2 cases (0.6%) of PFO closure-device embolization. In both patients, hypermobile septum primum and thick septum secundum were present. In one patient, failure to use a sizing balloon might have resulted in an underestimation of the PFO's size. In both patients, device embolization was identified in a timely fashion, the embolized device was safely retrieved, and the PFO was percutaneously closed with success. The incidence of PFO closure-device embolization is very low. The cases described here underscore the importance of imaging in the identification of morphologic predispositions to closure-device malpositioning, in the recognition of impending embolization, and in the timely management of embolization.
Open Access
More Versus Better: Learning From the Medtronic Valiant Navion Recall.
(Circulation. Cardiovascular interventions, 2022-07) Weissler, E Hope; Roe, Matthew; Hammill, Bradley G; Hughes, G Chad
Open Access
Outcomes of metallic stents for malignant ureteral obstruction.
(J Urol, 2012-09) Goldsmith, Zachariah G; Wang, Agnes J; Bañez, Lionel L; Lipkin, Michael E; Ferrandino, Michael N; Preminger, Glenn M; Inman, Brant A
PURPOSE: Malignant ureteral obstruction often necessitates chronic urinary diversion and is associated with high rates of failure with traditional ureteral stents. We evaluated the outcomes of a metallic stent placed for malignant ureteral obstruction and determined the impact of risk factors previously associated with increased failure rates of traditional stents. MATERIALS AND METHODS: Patients undergoing placement of the metallic Resonance® stent for malignant ureteral obstruction at an academic referral center were identified retrospectively. Stent failure was defined as unplanned stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction (recurrent hydroureteronephrosis or increasing creatinine). Predictors of time to stent failure were assessed using Cox regression. RESULTS: A total of 37 stents were placed in 25 patients with malignant ureteral obstruction. Of these stents 12 (35%) were identified to fail. Progressive hydroureteronephrosis and increasing creatinine were the most common signs of stent failure. Three failed stents had migrated distally and no stents required removal for recurrent infection. Patients with evidence of prostate cancer invading the bladder at stent placement were found to have a significantly increased risk of failure (HR 6.50, 95% CI 1.45-29.20, p = 0.015). Notably symptomatic subcapsular hematomas were identified in 3 patients after metallic stent placement. CONCLUSIONS: Failure rates with a metallic stent are similar to those historically observed with traditional polyurethane based stents in malignant ureteral obstruction. The invasion of prostate cancer in the bladder significantly increases the risk of failure. Patients should be counseled and observed for subcapsular hematoma formation with this device.
Open Access
Provoked exercise desaturation in patent foramen ovale and impact of percutaneous closure.
(JACC Cardiovasc Interv, 2012-04) Devendra, Ganesh P; Rane, Ajinkya A; Krasuski, Richard A
OBJECTIVES: This study was designed to assess the prevalence of provoked exercise desaturation (PED) in patients with patent foramen ovale (PFO) referred for cardiovascular evaluation and to evaluate the impact of PFO closure. BACKGROUND: Platypnea orthodeoxia syndrome is a rare, mechanistically obscure consequence of PFO that results in oxygen desaturation during postural changes. In our clinical experience, however, it is far less common than desaturation during exercise. METHODS: This was a single-center prospective study of 50 patients with newly diagnosed PFO. Each patient underwent standardized assessment for arterial oxygen saturation with pulse oximetry during postural changes and stair climbing exercise. Provoked exercise desaturation was defined as a desaturation of at least 8% from baseline to <90%. All patients who underwent closure were reevaluated 3 months after the procedure. Those with baseline PED were similarly reassessed for desaturation at follow-up. RESULTS: Mean age of the cohort was 46 ± 17 years, 74% were female, 30% had migraines, and 48% had experienced a cerebrovascular event. Seventeen patients (34%) demonstrated PED. Provoked exercise desaturation patients seemed demographically similar to non-PED patients. Ten PED patients underwent PFO closure (2 surgical, and 8 percutaneous). Drop in oxygen saturation was improved by an average of 10.1 ± 4.2% after closure (p < 0.001), and New York Heart Association functional class improved by a median of 1.5 classes (interquartile range: 0.75 to 2.00, p = 0.008). CONCLUSIONS: One-third of patients referred for assessment of PFO experience oxygen desaturation during stair exercise. Closure of PFO seems to ameliorate this phenomenon and improve functional status.
Open Access
Stream segregation on a single electrode as a function of pulse rate in cochlear implant listeners.
(2010) Duran, Sara I
While cochlear implants usually provide a high level of speech recognition in quiet, speech recognition in noise and music appreciation remain challenging. In response to these issues, several studies have proposed increasing the number of channels of information through multiple pulse rate strategies. For the selection of pulse rates, studies of multi-rate strategies have considered implementation issues such as harmonics, pitch saturation, and tonotopic order but have not considered the fundamental perceptual question of whether two pulse rates can provide independent channels of information on a single electrode. This study measures stream segregation as an indicator of whether different pulse rates on the same electrode can be perceived independently. This approach differs from that of previous stream segregation studies which focused on stimulation of alternating electrodes, with the motivation of determining a relationship between electrode stream segregation and speech perception in challenging noisy environments. Stream segregation in this study was measured using two stimulus sequences following an A-B-A-B structure where A and B were different pulse rates stimulatingthe same electrode. The timing between A and B was controlled to provide either aregular or irregular gap between the two pulse trains. The threshold at which subjects could distinguish a regular rhythm from an irregular rhythm was used as an estimate of stream segregation since detecting an irregular rhythm is an easier task when the streams are fused. Stream segregation in cochlear implant users, as with normal hearing listeners, was hypothesized to be influenced by factors such as frequency and the relative timing between tones. To attempt to assess the relationship between these and stream segregation, subjects’ rate discrimination and gap detection abilities were also measured. The results of this study indicate that stream segregation can occur for two pulse rates on a single electrode; thus, it may be possible to use pulse rates to create additional channels of information. Further, the stream segregation results were not strongly correlated with the gap detection or rate discrimination results. The lack of correlation with the gap detection results suggests that the task was measuring a separate perceptual phenomenon rather than providing another measure of gap detection. The lack of correlation with the rate discrimination results suggests that discriminability may not be a limiting factor in selecting rates for segregation. These results may have implications for the future design of multi-rate speech processing strategies.
Open Access
Using a Regent Aortic Valve in a Small Annulus Mitral Position Is a Viable Option.
(The Annals of thoracic surgery, 2018-04) Barac, Yaron D; Zwischenberger, Brittany; Schroder, Jacob N; Daneshmand, Mani A; Haney, John C; Gaca, Jeffrey G; Wang, Andrew; Milano, Carmelo A; Glower, Donald D
BACKGROUND:Outcome of mitral valve replacement in extreme scenarios of small mitral annulus with the use of the Regent mechanical aortic valve is not well documented. METHODS:Records were examined in 31 consecutive patients who underwent mitral valve replacement with the use of the aortic Regent valve because of a small mitral annulus. RESULTS:Mean age was 60 ± 14 years. Mitral stenosis or mitral annulus calcification was present in 30 of 31 patients (97%). Concurrent procedures were performed in 17 of 31 patients (55%). Median valve size was 23 mm. Mean mitral gradient coming out of the operating room was 4.2 ± 1.5 mm Hg and at follow-up echocardiogram performed at a median of 32 months after the procedure was 5.8 ± 2.4 mm Hg. CONCLUSIONS:A Regent aortic mechanical valve can be a viable option with a larger orifice area than the regular mechanical mitral valve in a problematic situation of a small mitral valve annulus. Moreover, the pressure gradients over the valve are acceptable intraoperatively and over time.