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Biomedical subjects

Laman A Gray

Publications and source records attributed to Laman A Gray.

10 recordsLinked to original sources
PubMed2006

Simple mechanical aortic valve closure in ventricular assist device recipients.

Patients with mechanical aortic valves that develop refractory heart failure may require left ventricular assist devices. These patients have an increased risk of postoperative thromboembolic events due to intermittent valve opening. Previously described techniques to address this problem can result in a significantly increased ischemic time. We describe a simple but novel technique to close the mechanical aortic prosthesis in an expeditious manner.

Aortic Valve↗
PubMed2005

Impending paradoxical embolism across a patent foramen ovale: case report.

We describe a case of impending paradoxical embolism in a 43-year-old male patient with pulmonary embolism. Transesophageal echocardiography revealed a thromboembolus straddling a patent foramen ovale. The patient underwent emergency removal of the intracardiac clot with closure of the patent foramen ovale. A postoperative work-up for a hypercoagulable state revealed a protein-S deficiency and bilateral lower extremity deep vein thromboses. A Greenfield inferior vena cava filter was inserted, anticoagulation was performed, and warfarin treatment was continued after the patient was discharged home.

Adult↗
PubMed2004

Initial experience with the AbioCor implantable replacement heart system.

OBJECTIVE: We sought to evaluate the safety and efficacy of the first available totally implantable replacement heart (AbioCor Implantable Replacement Heart System) in the treatment of severe, irreversible biventricular heart failure in human patients. METHODS: Seven male adult patients with severe, irreversible biventricular failure (>70% thirty-day predicted mortality) who were not candidates for transplantation met all institutional review board study criteria and had placement of the AbioCor Implantable Replacement Heart. All were in cardiogenic shock despite maximal medical therapy, including inotropes and intra-aortic balloon pumps. Mean age was 66.7 +/- 10.4 years (range, 51-79 years). Four of 7 patients had prior operations. Six had ischemic and one had idiopathic cardiomyopathy. All had 3-dimensional computer-simulated implantation of the thoracic unit that predicted adequate fit. At the time of the operation, the internal transcutaneous energy transfer coil, battery, and controller were placed. Biventriculectomy was then performed, and the thoracic unit was placed in an orthotopic position and attached to the atrial cuffs and outflow conduits with quick-connects. The flow was adjusted to 4 to 8 L/min. Central venous and left atrial pressures were maintained at 5 to 15 mm Hg. The device is powered through transcutaneous energy transfer. An atrial flow-balancing chamber is used to adjust left/right balance. The balance chamber and transcutaneous energy transfer eliminate the need for percutaneous lines. RESULTS: There was one intraoperative death caused by coagulopathic bleeding and one early death caused by an aprotinin reaction. There have been multiple morbidities primarily related to preexisting illness severity: 5 patients had prolonged intubation, 2 had hepatic failure (resolved in 1), 4 had renal failure (resolved in 3), and 1 each had recurrent gastrointestinal bleeding, acute cholecystitis requiring laparotomy, respiratory failure that resolved after 3 days of extracorporeal membrane oxygenation, and malignant hyperthermia (resolved). There were 3 late deaths: one caused by multiple systems organ failure (postoperative day 56), one caused by a cerebrovascular accident (postoperative day 142), and one caused by retroperitoneal bleeding and resultant multiple systems organ failure (postoperative day 151). This latter patient was not able to tolerate anticoagulation (no anticoagulation or antiplatelet therapy alone for 80% of the first 60 days) and had a transient ischemic attack on postoperative day 61 and a cerebrovascular accident on postoperative day 130. At autopsy, blood pumps were clean. The 2 patients who had large cerebrovascular accidents had thrombus on the atrial cage struts. These struts have been removed for future implants. There has been no significant hemolysis or device-related infections. The balance chamber has allowed for left/right balance in all patients (left atrial pressure within 5 mm Hg of right atrial pressure). Three patients have taken multiple (>50) trips out of the hospital, and 2 have been discharged from the hospital. Total days on support with the AbioCor are 759. CONCLUSION: The initial clinical experience suggests that the AbioCor might be effective therapy in patients with advanced biventricular failure. There have been no significant device malfunctions. Two of these patients have been discharged from the hospital.

Aged↗
PubMed2004

The total artificial heart: where we stand.

The AbioCor total artificial heart (TAH) is undergoing clinical feasibility testing as destination therapy in patients with end-stage congestive heart failure. So far, the device has been implanted in 11 of a projected 15 patients. The TAH has performed reliably, providing adequate circulatory support while extending survival and improving quality of life in most recipients. Thromboembolism remains a problem but is being addressed by optimizing device and patient management and refining the anticoagulation protocol. Because the device is totally implantable and requires no penetration of the skin, infection has been minimized. All recipients so far have been men. The device is large and this limits its use in smaller patients (i.e. women, small men and children). A smaller version is being developed. Although it has yet to receive Food and Drug Administration approval, the early clinical results suggest that the AbioCor TAH may become an accepted alternative to heart transplantation for selected patients with end-stage congestive heart failure. Further investigation with regard to its primary clinical applicability, i.e. as a rescue device for sudden catastrophic heart failure, is warranted.

Aged↗
PubMed2003

The AbioCor implantable replacement heart.

The AbioCor implantable replacement heart (IRH) is the first available totally implantable artificial heart. We recently initiated a multicenter trial of this device in patients with severe, irreversible biventricular failure. Patients who were not candidates for other therapies, including transplantation, were evaluated. All candidates were adults with inotrope-dependent biventricular failure, whose 30-day predicted mortality was higher than 70%. A three-dimensional computerized fit study predicted fit of the AbioCor thoracic unit in all recipients. At operation, the internal battery controller and transcutaneous energy transfer unit were placed. The AbioCor thoracic unit was placed in an orthotopic position after incision of the ventricals. There were 2 intraoperative deaths (due to intraoperative bleeding or aprotinin reaction). Four late deaths were recorded, 1 from multisystem organ failure and 3 cerebrovascular accidents. Autopsy revealed thrombus on the atrial struts of the 3 patients with cerebrovascular accident. Blood pumps and valves were clean on all patients. Significant morbidity was observed, primarily related to preexisting severity of illness. However, 3 patients recovered to the point of being able to take multiple trips outside of the hospital. Two patients were discharged from the hospital, with 1 patient being discharged home for more than 7 months. No significant device malfunctions or multi-system organ failure device-related infections were noted. The AbioCor IRH may be effective therapy for patients with end-stage heart failure. Many milestones have been achieved in the initial trial in humans, including the successful discharge of a patient to home and no significant device malfunctions. The occurrence of stroke is likely related to the presence of thrombus on the atrial struts and may be decreased as these atrial struts have been removed for future clinical implants.

Aged↗
PubMed2002

A pilot study to determine the feasibility of continuous cefazolin infusion.

BACKGROUND: Animal studies have shown that continuous infusion of beta-lactam antibiotics is more effective than intermittent dosing. We studied several dosing regimens of cefazolin in humans to determine safety and whether or not adequate serum and tissue antibiotic concentrations could be achieved in patients undergoing cardiac bypass. METHODS: A prospective, randomized pilot study was conducted at a university-affiliated teaching hospital over a 2-year period in patients undergoing first-time coronary artery bypass grafting. One hundred and thirty-seven patients were randomized to one of three groups. Group 1 (n = 64) received 1 g of cefazolin intravenously before operation and 1 g intravenously at the end of cardiopulmonary bypass. Group 2 (n = 35) received 2 g of cefazolin intravenously before operation, followed by a continuous intravenous infusion of cefazolin at 20 mg/min throughout surgery. Group 3 (n = 38) received 3 g of cefazolin intravenously before operation, followed by a continuous intravenous infusion of cefazolin at 15 mg/min throughout surgery. Venous blood and subcutaneous fat samples were obtained from the sternal wound in a subset of 34 patients at incision, 0.25 h, 0.5 h, and 1 h; at the end of cardiopulmonary bypass; and at wound closure. Venous blood was sampled in the recovery room and on postoperative day 1. Cefazolin concentrations in the samples were determined by reverse-phase high-performance liquid chromatography using a C18 column. RESULTS: Serum cefazolin concentrations were higher for group 3 when compared with group 1 at all six intraoperative intervals (p < 0.02) and for group 2 when compared with group 1 at four of six intraoperative intervals (p < 0.04). When compared with group 1, tissue cefazolin concentrations were higher for group 3 at all intraoperative intervals (p < 0.02). No related toxicity or adverse events were observed. CONCLUSION: Cefazolin administered as a large preoperative bolus with continuous intraoperative infusion resulted in higher serum and tissue concentrations when compared with conventional intermittent dosing. Pharmacodynamically, continuous infusion of beta-lactam antibiotics may be superior to intermittent dosing when used for perioperative prophylaxis against wound infection, especially for cases in which the antibiotic is not redosed intraoperatively.

Anti-Bacterial Agents↗
PubMedDate not supplied

Treadmill exercise in calves implanted with the AbioCor replacement heart.

The aim of this study was to evaluate the function of the AbioCor artificial heart implanted in calves that underwent treadmill exercise testing and to investigate the cardiovascular and metabolic responses during exercise. Six calves were implanted with the AbioCor. One week after surgery, exercise training was undertaken and animals were put on a treadmill at a speed of 0.5-1.0 mph, with the AbioCor operating at the maximum heart rate of 150 beats per minute. During exercise, the left and right atrial pressures were significantly increased (p < 0.05). Oxygen consumption was significantly elevated (p < 0.05). Lactate levels did not significantly increase (p > 0.05). The index of metabolic adequacy remained higher than 2.0, indicating that there was no substantial transition to anaerobic metabolism during exercise. There was an increased extraction of oxygen during exercise to meet the increased energy demands. Our study demonstrated that animals implanted with the AbioCor heart were able to maintain aerobic metabolism during low levels of exercise testing.

Animals↗
PubMedDate not supplied

Left ventricular and myocardial perfusion responses to volume unloading and afterload reduction in a computer simulation.

Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. In a few cases, patients have been successfully weaned from these devices after myocardial recovery. To promote myocardial recovery and alleviate the demand for donor organs, we are developing an artificial vasculature device (AVD) that is designed to allow the heart to fill to its normal volume but eject against a lower afterload. Using this approach, the heart ejects its stroke volume (SV) into an AVD anastomosed to the aortic arch, which has been programmed to produce any desired afterload condition defined by an input impedance profile. During diastole, the AVD returns this SV to the aorta, providing counterpulsation. Dynamic computer models of each of the assist devices (AVD, continuous, and pulsatile flow pumps) were developed and coupled to a model of the cardiovascular system. Computer simulations of these assist techniques were conducted to predict physiologic responses. Hemodynamic parameters, ventricular pressure-volume loops, and vascular impedance characteristics were calculated with AVD, continuous VAD, and asynchronous pulsatile VAD support for a range of clinical cardiac conditions (normal, failing, and recovering left ventricle). These simulation results indicate that the AVD may provide better coronary perfusion, as well as lower vascular resistance and elastance seen by the native heart during ejection compared with continuous and pulsatile VAD. Our working hypothesis is that by controlling afterload using the AVD approach, ventricular cannulation can be eliminated, myocardial perfusion improved, myocardial compliance and resistance restored, and effective weaning protocols developed that promote myocardial recovery.

Compliance↗
PubMedDate not supplied

In vivo evaluation of the biocompatibility of the totally implantable ventricular assist device (HeartSaver VAD).

A series of multicenter in vivo studies have been conducted to assess the biocompatibility and device performance of the HeartSaver VAD, a totally implantable pulsatile ventricular assist device (VAD). The experiments (n = 23) were conducted in calves with a mean weight of 101 (75-152) kg. Implants took place at four centers using two different surgical procedures of implantation (one with cardiopulmonary bypass and one without). Three anticoagulation regimens were used (one with continuous intravenous heparin, one with oral warfarin, and one with oral warfarin combined with antiplatelet clopidogrel therapy). Device function and biochemistry were monitored during the study, and organs and device analysis were conducted at explant. There were six nonsurvivors because of early surgical complications (during the first week of support). The postoperative courses in the remaining 17 (74%) calves were uneventful. Hemodynamic and biocompatibility indicators were monitored throughout the study. The mean duration of device support for those cases was 48 (13-92) days. Mean device flow was 7.15 (+/- 1.68) L/min. There were no deaths caused by infection; however, two animals developed endocarditis believed to be caused by the percutaneous instrumentation lines used for the study. No severe bleeding requiring reoperation occurred during the study. The mean plasma free hemoglobin was within normal limits at 6.8 +/- 2.6 mg/dl. Renal and hepatic functions were normal with a mean creatinine of 0.6 +/- 0.1 mg/dl and a mean aspartate aminotransferase of 68.7 +/- 42.6 mg/dl. Several device related improvements were identified and have now been implemented. Additional bovine implants with an optimized device are currently underway in preparation for human trials.

Animals↗