ABSTRACT
AIM: To validate the functionality of an implantable pudendal nerve stimulator under development for Food and Drug Administration approval to restore bladder function after spinal cord injury. METHODS: In nine cats under anesthesia, two tripolar cuff electrodes were implanted bilaterally on the pudendal nerves and one bipolar cuff electrode was implanted on the right pudendal nerve central to the tripolar cuff electrode. The pudendal nerve stimulator was implanted subcutaneously on the left lower back along the lumbosacral spine and connected to the cuff electrodes. In five cats, a double lumen catheter was inserted into the bladder through the urethra to infuse saline and measure bladder pressure and another catheter was inserted into the distal urethra to perfuse and measure the back pressure caused by urethral contraction. In four cats, a bladder catheter was inserted into the bladder dome and the urethra was left open so that voiding could occur without urethral outlet obstruction. RESULTS: The implantable pudendal nerve stimulator was controlled wirelessly and successfully provided the required stimulation waveforms to different cuff electrodes. Pudendal nerve stimulation (PNS) at 5 Hz increased bladder capacity to about 200% of control capacity. PNS at 20 to 30 Hz induced large (80-100 cmH2 O) bladder contractions under isovolumetric conditions. When combined with ipsilateral or bilateral pudendal nerve block induced by 6 to 10 kHz stimulation, PNS at 20 to 30 Hz elicited low pressure (<40 cmH 2 O) efficient (70%) voiding. CONCLUSIONS: The implantable stimulator generated the required stimulation waveforms and successfully induced low pressure efficient voiding in anesthetized cats.
Subject(s)
Implantable Neurostimulators , Pudendal Nerve , Urination , Animals , Cats , Electric Stimulation , Electrodes, Implanted , Muscle Contraction , Urethra/physiology , Urinary Bladder/physiologyABSTRACT
The very limited options available to treat ventricular failure in children with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device at the University of Pittsburgh (UoP) and University of Pittsburgh Medical Center (UPMC). Our effort involves a consortium consisting of UoP, Children's Hospital of Pittsburgh (CHP), Carnegie Mellon University, World Heart Corporation, and LaunchPoint Technologies, Inc. The overall aim of our program is to develop a highly reliable, biocompatible ventricular assist device (VAD) for chronic support (6 months) of the unique and high-risk population of children between 3 and 15 kg (patients from birth to 2 years of age). The innovative pediatric ventricular assist device we are developing is based on a miniature mixed flow turbodynamic pump featuring magnetic levitation, to assure minimal blood trauma and risk of thrombosis. This review article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.
Subject(s)
Heart-Assist Devices , Biocompatible Materials , Child , Extracorporeal Membrane Oxygenation , HumansABSTRACT
Improvements in implantable ventricular assist device (VAD) performance will be required to obtain patient outcomes that are comparable with those of heart transplantation. The HeartQuest VAD (WorldHeart, Oakland, CA, U.S.A.) is an advanced device, with full magnetic suspension of the rotor, designed to address specific clinical shortcomings in existing devices and to maximize margins of safety and performance for an implantable assist device. The device dimensions are 35 x 75 mm, with a total weight of 440 g. The system was designed using extensive computer modeling of device function; a total of two iterations of device prototypes were built before building the clinical version. Animal study results have been very promising, with over 30 calf studies completed. Plasma-free hemoglobin levels returned to preoperative levels, and other hematology results were in the normal ranges. Highlights include clean surfaces seen in a 116-day experiment with no anticoagulation after day 43. Feasibility clinical trials are planned to start in 2006.
Subject(s)
Heart, Artificial , Animals , Cardiac Surgical Procedures/instrumentation , Cattle , Heart, Artificial/adverse effects , Heart, Artificial/classification , Hemoglobins/metabolism , Hemorheology , Male , Prosthesis Design , TitaniumABSTRACT
The very limited options available to treat ventricular failure in patients with congenital and acquired heart diseases have motivated the development of a pediatric ventricular assist device (VAD). Our effort involves a consortium consisting of the University of Pittsburgh, Carnegie Mellon University, Children's Hospital of Pittsburgh, World Heart Corporation, and LaunchPoint Technologies, LLC. The overall aim of our program is to develop a highly reliable, biocompatible VAD for chronic support (6 months) of the unique and high-risk population of children between 3 kg and 15 kg (patients from birth to 2 years of age). The innovative pediatric VAD we are developing (PediaFlow) is based on a miniature mixed-flow turbodynamic pump featuring magnetic levitation, with the design goal being to assure minimal blood trauma and risk of thrombosis. This article discusses the limitations of current pediatric cardiac assist treatment options and the work to date by our consortium toward the development of a pediatric VAD.
Subject(s)
Heart Failure/surgery , Heart-Assist Devices , Biocompatible Materials/therapeutic use , Child, Preschool , Computer Simulation , Equipment Design , Heart Defects, Congenital/complications , Heart Diseases/complications , Heart Failure/etiology , Humans , Infant , Models, CardiovascularABSTRACT
Clinically available blood pumps and those under development suffer from poor mechanical reliability and poor biocompatibility related to anatomic fit, hemolysis, and thrombosis. To alleviate these problems concurrently in a long-term device is a substantial challenge. Based on testing the performance of a prototype, and on our judgment of desired characteristics, we have configured an innovative ventricular assist device, the CF-VAD4, for long-term use. The design process and its outcome, the CFVAD4 system configuration, is described. To provide unprecedented reliability and biocompatibility, magnetic bearings completely suspend the rotating pump impeller. The CFVAD4 uses a combination of passive (permanent) and active (electric) magnetic bearings, a mixed flow impeller, and a slotless 3-phase brushless DC motor. These components are shaped, oriented, and integrated to provide a compact, implantable, pancake-shaped unit for placement in the left upper abdominal quadrant of adult humans.
