The design, development, and evaluation of a prototypic, prosthetic venous valve

<p>Abstract</p> <p>Background</p> <p>Chronic venous insufficiency is a serious disease for which there is no clearly successful surgical treatment. Availability of a proven prosthetic vein valve could provide such an option by reducing venous reflux while permitting normal antegrade flow.</p> <p>Methods</p> <p>A new prosthetic vein valve design has been developed which mimics the function of a natural valve by ensuring complete closure of the leaflets with minimal obstruction for antegrade flow. A 2:1 mock-up of the device was tested to evaluate its ability to prevent regurgitation and several key modifications were made. A subsequently re-designed 1:1 prototype was then built in 4 slightly different size configurations and then each tested under physiologic conditions of pulsatile flow in both supine and standing positions.</p> <p>Results</p> <p>Each of the configurations showed acceptable amounts of antegrade resistance and effective orifice area and showed low values of regurgitation and % reflux with two of the prototype configurations (flange lengths of 2.5 mm and 3.75 mm) having corresponding values of <2.5 mmHg-min/L, >97%, 11 mL, and 36%, respectively. These values are particularly striking when compared to the corresponding regurgitation and % reflux values of 60 mL and 205%, respectively, when no device is present.</p> <p>Conclusion</p> <p>The results of this study show that this prototype vein valve design is capable of providing significant relief of reflux under realistic conditions without inducing any increase in antegrade flow resistance and warrants further testing with <it>in vivo </it>models.</p

Physiologically-based testing system for the mechanical characterization of prosthetic vein valves

Due to the relatively limited amount of work done to date on developing prosthetic vein (as opposed to cardiac) valves, advances in this topic require progress in three distinct areas: 1) improved device design, 2) relevant device testing conditions, and, 3) appropriate parameters for evaluation of results. It is the purpose of this paper to address two of these issues (#2 and #3) by: 1) performing a study of normal volunteers to quantify the anatomy and hemodynamic features of healthy venous valves, 2) construction of a 2-step, in vitro testing procedure, which simulates both physiologic and postural conditions seen in the lower extremity venous system, and, 3) defining several modified and new parameters which quantify dynamic valve characteristics

Algorithm for Mobile Platform-Based Real-Time QRS Detection

Recent advancements in smart, wearable technologies have allowed the detection of various medical conditions. In particular, continuous collection and real-time analysis of electrocardiogram data have enabled the early identification of pathologic cardiac rhythms. Various algorithms to assess cardiac rhythms have been developed, but these utilize excessive computational power. Therefore, adoption to mobile platforms requires more computationally efficient algorithms that do not sacrifice correctness. This study presents a modified QRS detection algorithm, the AccYouRate Modified Pan–Tompkins (AMPT), which is a simplified version of the well-established Pan–Tompkins algorithm. Using archived ECG data from a variety of publicly available datasets, relative to the Pan–Tompkins, the AMPT algorithm demonstrated improved computational efficiency by 5–20×, while also universally enhancing correctness, both of which favor translation to a mobile platform for continuous, real-time QRS detection

Lower mitochondrial energy production of the thigh muscles in patients with low-normal ankle-brachial index

Background--Lower muscle mitochondrial energy production may contribute to impaired walking endurance in patients with peripheral arterial disease. A borderline ankle-brachial index (ABI) of 0.91 to 1.10 is associated with poorer walking endurance compared with higher ABI. We hypothesized that in the absence of peripheral arterial disease, lower ABI is associated with lower mitochondrial energy production. Methods and Results--We examined 363 men and women participating in the Baltimore Longitudinal Study of Aging with an ABI between 0.90 and 1.40. Muscle mitochondrial energy production was assessed by post-exercise phosphocreatine recovery rate constant (kPCr) measured by phosphorus magnetic resonance spectroscopy of the left thigh. A lower post-exercise phosphocreatine recovery rate constant reflects decreased mitochondria energy production.The mean age of the participants was 71\uc2\ub112 years. A total of 18.4% had diabetes mellitus and 4% were current and 40% were former smokers. Compared with participants with an ABI of 1.11 to 1.40, those with an ABI of 0.90 to 1.10 had significantly lower post-exercise phosphocreatine recovery rate constant (19.3 versus 20.8 ms-1, P=0.015). This difference remained significant after adjusting for age, sex, race, smoking status, diabetes mellitus, body mass index, and cholesterol levels (P=0.028). Similarly, post-exercise phosphocreatine recovery rate constant was linearly associated with ABI as a continuous variable, both in the ABI ranges of 0.90 to 1.40 (standardized coefficient=0.15, P=0.003) and 1.1 to 1.4 (standardized coefficient=0.12, P=0.0405). Conclusions--An ABI of 0.90 to 1.10 is associated with lower mitochondrial energy production compared with an ABI of 1.11 to 1.40. These data demonstrate adverse associations of lower ABI values with impaired mitochondrial activity even within the range of a clinically accepted definition of a normal ABI. Further study is needed to determine whether interventions in persons with ABIs of 0.90 to 1.10 can prevent subsequent functional decline

Algorithm for Mobile Platform-Based Real-Time QRS Detection

Recent advancements in smart, wearable technologies have allowed the detection of various medical conditions. In particular, continuous collection and real-time analysis of electrocardiogram data have enabled the early identification of pathologic cardiac rhythms. Various algorithms to assess cardiac rhythms have been developed, but these utilize excessive computational power. Therefore, adoption to mobile platforms requires more computationally efficient algorithms that do not sacrifice correctness. This study presents a modified QRS detection algorithm, the AccYouRate Modified Pan&ndash;Tompkins (AMPT), which is a simplified version of the well-established Pan&ndash;Tompkins algorithm. Using archived ECG data from a variety of publicly available datasets, relative to the Pan&ndash;Tompkins, the AMPT algorithm demonstrated improved computational efficiency by 5&ndash;20&times;, while also universally enhancing correctness, both of which favor translation to a mobile platform for continuous, real-time QRS detection