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Biomedical subjects

A Kantrowitz

Publications and source records attributed to A Kantrowitz.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

A new, all silicone rubber small vessel prosthesis.

A new small vessel prosthesis composed entirely of silicone rubber was developed. The new prosthesis has a trilaminar wall structure consisting of: 1) a porous blood contacting layer designed to promote the deposition of a pseudoneointima (PNI) from blood flowing over the surface; 2) a solid middle layer the thickness of which is adjusted to provide approximately the same radial compliance as the host artery; and 3) a porous outer layer that promotes connective tissue attachment to the exterior of the prosthesis to limit tissue capsule formation around the implant and preserve its compliance after healing of the perigraft tissues. The new graft also has excellent suture retention in addition to its other desirable physical characteristics. The mechanical integrity of the textured surfaces was first evaluated in vitro with cyclic flexure testing at a 20-30% strain. Grafts of 4 mm inside diameter by 5 cm length were then implanted in the left carotid artery of adult dogs for an 8 week period. Seven animals were studied. Platelet inhibitors were administered postoperatively. The patency rate was 86% (six of seven); all grafts except the first remained widely patent. After the animals were killed, the grafts were surgically exposed, and compliance was measured directly. The PNI from the grafts was then studied with light and scanning electron microscopy, and morphometric measurements were made of PNI thickness over the length of the graft. Overall, the grafts retained 80% of their preimplant compliance (n = 5); however, in the absence of any postoperative complications such as hematoma or infection, the grafts remained essentially isocompliant with the host artery during the duration of this study.

Animals↗
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Initial clinical trial of a closed loop, fully automatic intra-aortic balloon pump.

A new generation, closed loop, fully automatic intraaortic balloon pump (CL-IABP) system continuously optimizes diastolic augmentation by adjusting balloon pump parameters beat by beat without operator intervention. In dogs in sinus rhythm and with experimentally induced arrhythmias, the new CL-IABP system provided safe, effective augmentation. To investigate the system's suitability for clinical use, 10 patients meeting standard indications for IABP were studied. The patients were pumped by the fully automatic IABP system for an average of 20 hr (range, 1-48 hr). At start-up, the system optimized pumping parameters within 7-20 sec. Evaluation of 186 recordings made at hourly intervals showed that inflation began within 20 msec of the dicrotic notch 99% of the time. In 100% of the recordings, deflation straddled the first half of ventricular ejection. Peak pressure across the balloon membrane averaged 55 mmHg and, in no case, exceeded 100 mmHg. Examination of the data showed that as soon as the system was actuated it provided consistently beneficial diastolic augmentation without any further operator intervention. Eight patients improved and two died (one of irreversible cardiogenic shock and one of ischemic cardiomyopathy). No complications were attributable to the investigational aspects of the system. A fully automated IABP is feasible in the clinical setting, and it may have advantages relative to current generation IABP systems.

Adult↗
PubMedDate not supplied

Updated feasibility trial experience with the Viaderm percutaneous access device.

The percutaneous access device (PAD) is used to connect an external drive unit to the Kantrowitz CardioVad (KCV), a cardiac assist device for the treatment of chronic heart failure. The PAD conveys pneumatic power from a drive unit to the implanted blood pump and an electrocardiogram signal from the myocardium to the drive unit. The device-tissue interface of the PAD is precoated with autologous fibroblasts cultured from a skin sample of the intended recipient. This preparation demonstrated long-term stability in animals and was adopted for use in patients receiving the KCV. The KCV is activated intermittently, and the drive unit may be connected and disconnected by the patient, which subjects the PAD to frequent manipulation. To date, the PAD has been implanted in nine patients ranging in age from 41 to 74 years. Implant times ranged from 2 to 458 days, for a total of 1082 days, of which 557 days were in an outpatient setting. Two patients experienced episodes of infection that did not originate from the PAD-tissue interface. This feasibility study demonstrated that (1) the PAD is stable and infection resistant in long-term ambulatory patients, (2) the PAD withstood the challenge of daily manipulation (the KCV is turned on and off electively), and (3) PADs can be replaced, if necessary.

Adult↗
PubMedDate not supplied

Perioperative management of calves undergoing implantation of a left ventricular assist device.

OBJECTIVE: To describe perioperative management of calves that underwent left lateral thoracotomy, aortic cross-clamping, partial left heart bypass and implantation of a left ventricular assist device. SAMPLE POPULATION: A total of 43 healthy castrated male calves, weighing 121 +/- 24 kg. RESULTS: Diazepam (mean +/- SD, 0.26 +/- 0.07 mg/kg), ketamine (5.9 +/- 2.17 mg/kg) and isoflurane were used in the anesthetic management of calves undergoing implantation of a left ventricular assist device in the descending thoracic aorta. Other adjunctive agents administered were fentanyl (11 +/- 5.4 microg/kg), lidocaine (4.9 +/- 3.19 mg/kg), bupivacaine (0.75%) and butorphanol (0.49 +/- 0.13 mg/kg). None of the calves regurgitated at induction or during intubation. A tube was used to drain the rumen and prevent bloat during the procedure. Partial left heart bypass was used to perfuse the caudal half of the body during the period of aortic cross clamp and device implantation. Initial mean systemic blood pressure was 96 +/- 25 mm Hg, and pressures measured in the auricular artery increased during aortic cross-clamping and bypass. Vasoconstrictor therapy was required to treat caudal arterial hypotension during the procedure in 9 calves. Mean systemic arterial pressures returned to baseline values by the end of the anesthetic period. Initial mean pulmonary arterial pressures (PAP) were 22 +/- 3 mm Hg. A significant but transient increase in pulmonary arterial pressure occurred after both heparin and protamine administration. CONCLUSIONS: The described anesthetic protocol was effective for thoracotomy and implantation of an intra-aortic left ventricular assist device in normal calves. Partial left ventricular bypass was a useful adjunct during the period of aortic cross clamp. The doses of heparin and protamine administered were effective. Responsibility to monitor oxygenation of the cranial half of the animal continues during the bypass period as hypoxemia due to pulmonary dysfunction will not be detected by the perfusionist.

Analysis of Variance↗
PubMedDate not supplied

Autologous muscle to assist the failing heart: first experiments.

This report summarizes early work to explore the harnessing of noncardiac muscle to supplement the work of the failed left ventricle. First experiments, in 1959, investigated the possibility of using the mobilized left diaphragm around the distal portion of the thoracic aorta. A stimulus was delivered to the left phrenic nerve during diastole, causing that portion of the aorta to be collapsed by the contracting muscle and thus act as a pump. A significant rise in diastolic pressure compared with controls was obtained in all experiments. This study and later investigations with a graft sutured to the left ventricle indicated the feasibility and promise of biologic augmentation. The inherent problems of stroke volume and fatiguability of the transposed diaphragmatic muscle, at the repetitive rates required for adequate hemodynamic assistance in the dog, led us to explore other approaches to cardiac assistance.

Animals↗
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State of the art. Circulatory support.

Beginning in midlife, chronic congestive heart failure (CCHF) is a major health problem in the United States. For patients over 65, the costs incurred in treating CCHF are vast, accounting for the highest hospitalization charges among all DRG's for Medicare patients. Heart transplants are an important but insufficient solution to the problem. Consistent progress is being made in the development of left ventricular assist devices, and, along with preventive and other therapeutic approaches, left ventricular assist devices have the potential for being a significant part of the solution for CCHF.

Aged↗
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Coronary perfusion under general and selective cardiac hypothermia.

Experiments to assess left ventricular function in dogs during and after 2 hours of hypothermic cardioplegia are reported. During the experiment myocardial temperature was maintained between 15 degrees C and 18 degrees C by controlling the rate of flow of a cool cardioplegic solution into the coronary vessels. Before and after the period of hypothermia the left atrial pressure was gradually changed and the aortic flows and pressures that changed in response were recorded. The left ventricular stroke work (gm) was then calculated using the relationship: LVSM = (formula: see text) where: SV = stroke volume (ml), AP = arterial pressure (mmHg), LAP = left atrial pressure (mmHg). Comparison of the calculated values indicated that this method of maintaining cardiac hypothermia reduced cardiac function only slightly.

Animals↗