Mathematical Model analysis of Wallstent and Aneurx: dynamic responses of bare-metal endoprosthesis compared with those of stent-graft

We performed this study in order to analyze the mechanical properties of bare-metal Wallstent endoprostheses and of AneuRx stent-grafts and to compare their responses to hemodynamic forces. Mathematical modeling, numerical simulations, and experimental measurements were used to study the 2 structurally different types of endoprostheses. Our findings revealed that a single bare-metal Wallstent endoprosthesis is 10 times more flexible (elastic) than is the wall of the aneurysmal abdominal aorta. Graphs showing the changes in the diameter and length of the stent when exposed to a range of internal and external pressures were obtained. If the aorta is axially stiff and resists length change, a force as large as 1 kg can act in the axial direction on the aortic wall. If the stent is not firmly anchored, it will migrate. In contrast, a fabric-covered, fully supported, stent-graft such as the AneuRx is significantly less compliant than the aorta or the bare-metal stent. During each cardiac cycle, the stent frame tends to move due to its higher elasticity, while the fabric resists movement, which might break the sutures that join the fabric to the frame. Elevated local transmural pressure, detected along the prosthesis graft, can contribute to material fatigue.

Thirty-five years of mechanical circulatory support at the Texas Heart Institute: an updated overview

Since the 1960s, the Texas Heart Institute has been intimately involved in the development of mechanical circulatory support devices (for example, ventricular assist devices, aortic counterpulsation pumps, and total artificial hearts) for both short- and long-term use. Here, we review the varied clinical experience with these technologies at the Texas Heart Institute over the last 35 years.

Development of a rat model of graded contusive spinal cord injury using a pneumatic impact device

An animal model of spinal cord trauma is essential for understanding the injury mechanisms, cord regeneration, and to aid the development of new therapeutic modalities. This study focused on the development of a graded experimental contusion model for spinal cord injury (SCI) using a pneumatic impact device made in Korea. A contusive injury was made to the dorsal aspect of the cord. Three trauma groups were defined according to the impact velocity (IV). A control group (n=6), received laminectomy only. Group 1 (n=10), 2 (n=10), and 3 (n=10) had IVs of 1.5 m/sec, 2.0 m/sec, and 3.5 m/sec respectively. Functional assessments were made up to the 14th day after injury. The cord was removed at the 14th postinjury day and prepared for histopathologic examination. Significant behavioral and histopathological abnormalities were found in control and each trauma group. All trauma groups showed severe functional impairment immediately after injury but following different rates of functional recovery (Fig. 5). As the impact velocity and impulse increased, the depth of contusive lesion revealed to be profound the results show that the rat model reproduces spinal cord lesions consistently, has a distinctive value in assessing the effects of impact energy.

First clinical use of the redesigned HeartMate II left ventricular assist system in the United States: a case report

Axial flow ventricular assist devices show great promise as a potential treatment for patients with end-stage heart failure. The HeartMate II system, redesigned on the basis of initial clinical experiences in Europe, is now in clinical trials in the United States. We report on the 1st use of the newly redesigned HeartMate II in the United States. The system has unique features, which include an accurate flow estimator and the ability to automatically detect and correct excessive left ventricular unloading. The new design also incorporates changes in the texturing of the blood-contacting surfaces to prevent thrombosis. The implantation technique and configuration are similar to those of the HeartMate XVE LVAS and require a median sternotomy for access. The 1st patient to receive the device in the United States has had an uncomplicated perioperative course and now awaits transplantation.

High power transcranial beam steering for ultrasonic brain therapy

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5 cm2 and works at 0.9 MHz central frequency with a maximum 20 W cm(-2) intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducer distributions on a spherical surface are simulated: hexagonal, annular and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/- 15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system.

High power transcranial beam steering for ultrasonic brain therapy

A sparse phased array is specially designed for non-invasive ultrasound transskull brain therapy. The array is made of 200 single elements corresponding to a new generation of high power transducers developed in collaboration with Imasonic (Besançon, France). Each element has a surface of 0.5 cm2 and works at 0.9 MHz central frequency with a maximum 20 W cm(-2) intensity on the transducer surface. In order to optimize the steering capabilities of the array, several transducer distributions on a spherical surface are simulated: hexagonal, annular and quasi-random distributions. Using a quasi-random distribution significantly reduces the grating lobes. Furthermore, the simulations show the capability of the quasi-random array to electronically move the focal spot in the vicinity of the geometrical focus (up to +/- 15 mm). Based on the simulation study, the array is constructed and tested. The skull aberrations are corrected by using a time reversal mirror with amplitude correction achieved thanks to an implantable hydrophone, and a sharp focus is obtained through a human skull. Several lesions are induced in fresh liver and brain samples through human skulls, demonstrating the accuracy and the steering capabilities of the system.

Transoesophageal ultrasound applicator for sector-based thermal ablation: first in vivo experiments

New curative and palliative treatments must be proposed to respond to the bad long-term prognosis of oesophageal cancers. It has been demonstrated that high intensity ultrasound (US) can induce rapid, complete and well-defined coagulation necrosis. For the treatment of this cancer, we designed an applicator that uses an intraductal approach. The active part is an air-backed plane transducer. It has an external water-cooling system and operates at 10 MHz. Ex vivo experiments conducted on pig liver demonstrated the ability of this applicator to generate, by rotating the transducer, circular or sector-based coagulation necroses at predetermined depths up to 13 mm, with an excellent angular precision. The treatment of sector-based oesophageal tumours may be critical, where both malignant and healthy tissues are covered by the US beam. Thus, in vivo trials were conducted on five healthy pig oesophaguses to determine the maximal thermal dose that will not induce a perforation of the oesophagus or surrounding tissues. From the results of previous studies, this dose is high enough to treat pathological tissues. These promising results indicate that this US system represents a safe and effective tool for the clinical treatment of oesophageal tumours.

Cardiology's 10 greatest discoveries of the 20th century

We present a brief summary of the 10 greatest cardiologic developments and discoveries of the 20th century Described are electrocardiography; preventive cardiology and the Framingham Study; "lipid hypotheses" and atherosclerosis; coronary care units; echocardiography; thrombolytic therapy; cardiac catheterization and coronary angiography; open-heart surgery; automatic implantable cardiac defibrillators; and coronary angioplasty. These topics are the personal choices of the authors.

Management of patients supported on the Hemopump cardiac assist system

The Hemopump Cardiac Assist System is a relatively new intraarterial, axial-flow circulatory assist device that offers temporary left ventricular support to patients in refractory cardiogenic shock, without requiring major surgery for insertion. Use of the Hemopump is associated with a low complication rate. Device-related morbidity is extremely rare. Because the Hemopump is safe for use in community hospitals, the number of patients supported by this device is expected to increase. In this report, we present general guidelines for the care of patients supported by the Hemopump. We describe techniques for the management of afterload reduction, supravalvular dislodgement, device malfunction, ventricular ectopy, intracardiac shunting, and inflow cannula obstruction.

Intraoperative transesophageal echocardiography for congenital heart disease

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The probe, a balloon-on-the-wire: clinical experience with a new low-profile, fixed-wire balloon catheter system

We reviewed the clinical records of the 1st 144 consecutive patients in whom the Probe trade mark, a balloon-on-the-wire, was used for percutaneous transluminal coronary angioplasty at the Texas Heart Institute. The goal of our retrospective study was to establish the efficacy and safety of this new balloon catheter. The Probe was used in 227 lesions, most of which were considered severe and difficult to pass. The Probe was the 1st catheter used in 160 lesions (70%), and in 67 lesions (30%) the Probe was used after other balloon catheters. In 70.9% (161/227) of lesions treated, the Probe reduced the stenosis to less than 50% of the luminal diameter. Of 144 patients treated, 116 (81%) had a successful result: 98 of these had adequate recanalization of all vessels treated, while 17 had adequate recanalization of the most significant vessels. A relatively high number of lesions (17 lesions, 7.5%) became totally occluded during the procedure. Eight patients (6%) required emergency surgery because of impending infarction. No hospital deaths occurred, and there were only 2 patients who suffered transmural myocardial infarction. Of the 160 Probe devices used, 23 (14%) malfunctioned: the balloon ruptured in 11 procedures; the balloon twisted, causing "balloon volvulus," in 5; the balloon failed to deflate in 4; and the tip detached in 3. The Probe has significant advantages over other balloon systems for treating severe coronary lesions because of its low profile, but it is also less reliable and safe. Our results show that the Probe should be used with great care, and only in treating lesions not amenable to treatment with removable-guidewire catheters.

'Out of this nettle...'

The importance of standardisation of all types of apparatus used by the anaesthetist for the safety of the patient-a matter of particular concern to Joseph Thomas Clover-is emphasized. The various organisations national and international, undertaking the production of standards are detailed and their mode of operation and the difficulties encountered in their work are described. Some of their achievements in the field of anaesthetics are listed.