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Biomedical subjects

O H Frazier

Publications and source records attributed to O H Frazier.

At least 217 records · Page 12Linked to original sources
PubMed1994

Current methods for circulatory support.

Although the concept of artificial circulatory support has existed for almost 200 years, it has only been within the last 4 decades that engineers and physicians have developed mechanical devices that can 1) temporarily support the circulation in a patient until the heart recovers or a new heart can be transplanted, or 2) permanently replace a failed heart. In this paper, we briefly describe the devices and techniques that are in current clinical use and speculate on the use of such devices in the future.

Counterpulsation↗
PubMed1994

Progress in cardiac transplantation.

This article summarizes general practices in cardiac transplantation, including the selection of recipients and pretransplant management, selection of donors, surgical technique, management of perioperative complications, and induction and maintenance protocols for immunosuppression. Advancements in the management of rejection and infection also are included. Coronary artery disease is the most frequent cause of late death in spite of improved immunosuppressive regimens, antiplatelet agents, and lipid-controlling drugs. Still, long-term survival has improved markedly. A brief description of the Texas Heart Institute experience with 532 cardiac transplants is provided.

Cause of Death↗
PubMed1994

The development of an implantable, portable, electrically powered left ventricular assist device.

The development of the portable, electrically powered LVAD was a complex process that began in the early 1970s with the left ventricular assist project sponsored by the National Institutes of Health. The problems that DeBakey outlined in 1971 that challenged widespread clinical use of a ventricular assist device have today largely been solved by the TCI portable, electrically powered LVAD. The cost of LVAD implantation and maintenance, although still considerable, is less than the cost of caring for a patient in an intensive care unit for 75 days (the median waiting time in 1992 for a UNOS Status I candidate [UNOS, personal communication, 1994]) and comparable with the cost of other devices in use, such as the internal defibrillator. Although the implantation of the LVAD still requires a major operation, it is now a commonly performed procedure in transplant centers that use LVADs, and the level of operative risk is considered acceptable. The operation to implant an LVAD is usually performed in patients for whom death is imminent, and the potential benefit to such patients is high in relation to the risk of the surgical procedure. DeBakey feared that textured blood-contacting surfaces might not be suitable over long periods, but this has not been the case.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Artificial circulatory support with textured interior surfaces. A counterintuitive approach to minimizing thromboembolism.

BACKGROUND: Although numerous left ventricular assist devices (LVADs) have been used clinically, frequent thromboembolic complications have been reported despite the smooth interior LVAD surfaces and systemic anticoagulant medication. In contrast, the Thermo Cardiosystems HeartMate 1000 IP LVAD has textured interior surfaces that are promptly covered by a densely adherent neointima. We hypothesize that elimination of a direct interface between prosthetic material and blood elements reduces the risk of peripheral embolization and minimizes the necessity for systemic anticoagulant medication. This report defines the thromboembolic risk of this type of LVAD and characterizes the nature and effectiveness of the various anticoagulation regimens that were tested during the initial clinical trial with this device. METHODS AND RESULTS: All values are reported as mean +/- SD. Fifty-four males and three females with an average age of 47 +/- 11 years were supported with the HeartMate 1000 IP LVAD for an average of 62 +/- 76 days at 11 clinical centers in the United States. Patients were prospectively evaluated for thromboembolic complications. Five different anticoagulation regimens were used during the first 4 postoperative weeks: no anticoagulants, low-molecular-weight dextran, heparin, dipyridamole plus aspirin, or miscellaneous agents. After the first 4 weeks, the patients were treated with aspirin plus dipyridamole or miscellaneous agents. Prothrombin time (PT), partial thromboplastin time (PTT), and fibrinogen values for the patients were measured at 0.1, 1, 2, 4, 8, 12, 16, 20, 24, 32, and 46 weeks during support. Two patients (3.5%) suffered thromboembolic cerebrovascular complications, an incidence of 0.2 episodes per patient-year of observation. One episode was due to fungal vegetation developing on the device and the other was due to embolization from a previously placed native mechanical aortic valve prosthesis. In the absence of infection, there were no device-related thromboembolic complications. Mean prothrombin time for all groups was 13.3 +/- 0.5 seconds with no significant intergroup differences. Mean partial thromboplastin time during the first 4 weeks for the heparin-treated group was 53.3 +/- 6.6 seconds, which was significantly longer than for all other groups, but fell to control values after heparin was discontinued at 4 weeks. Mean fibrinogen level for all groups was 370 +/- 48 mg/dL, with no intergroup differences. CONCLUSIONS: The HeartMate 1000 IP LVAD provides adequate circulatory support with a low risk of thromboembolism despite minimal systemic anticoagulation. The use of textured surfaces may be an important factor contributing to the low observed risk of thromboembolic complications.

Anticoagulants↗
PubMed1994

Transmyocardial laser revascularization. Anatomic evidence of long-term channel patency.

Transmyocardial laser revascularization, a new surgical technique, is being tested in patients with chronic obstructive coronary artery disease that is refractory to conventional revascularization techniques and to maximal medical therapy. During the operation, which is performed on the beating heart through a left thoracotomy, a high-energy CO2 laser is used to bore transmural channels (1 mm in diameter) into the left ventricle. Each high-energy laser pulse is delivered during end diastole and transects the heart within 10 to 60 msec. The operation is based on the theory that blood will flow directly from the left ventricle into the channels and then into the myocardial vascular plexus. Restoring perfusion should alleviate ischemia in potentially viable myocardium and improve ventricular function. Recently, one of our patients died 3 months after transmyocardial laser revascularization of causes unrelated to the operation. Histologic analysis enabled us to obtain, for the 1st time, anatomic evidence of patent laser channels. Routine staining of cardiac tissue with hematoxylin and eosin revealed multiple patent channels, running perpendicular to and interconnecting with the native vasculature. Although reactive fibrous scar tissue had caused narrowing of the original laser tract, the channels had endothelialized and they contained red blood cells. These findings suggest that the laser channels were functional. We report this interesting case and briefly discuss the anatomic and physiologic phenomena involved in establishing camerosinusoidal blood flow by use of transmyocardial laser revascularization.

Coronary Disease↗
PubMed1993

A model to predict survival at time of postcardiotomy intraaortic balloon pump insertion.

To facilitate timely application of new forms of cardiac support to patients at highest risk after cardiotomy despite conventional support with the intraaortic balloon pump, an accurate prediction of survival must be available at the time of weaning from cardiopulmonary bypass. We, therefore, acquired 240 demographic, disease, and perioperative characteristics of 322 patients (mortality rate, 48.4%) who required IABP support to separate from bypass. Four variables available before or within 10 minutes of the first attempt at weaning from bypass significantly predicted mortality by stepwise logistic regression: complete heart block as demonstrated by need for temporary pacing at weaning (p < 0.001), advanced age (p < 0.002), preoperative blood urea nitrogen concentration (p = 0.036), and female sex (p = 0.048). An equation generated by the logistic model predicted a 72.2% survival rate in the 25% of patients at least risk (actual survival rate, 71.6%); in the 25% at greatest risk, death was predicted in 73.0%, and the actual mortality rate was 74.1%. The equation was then prospectively applied to 330 intraaortic balloon pump-supported patients managed at another institution. The overall mortality rate there was 41.2%; in the 25% at least risk, predicted survival rate was 70.5% (actual survival rate, 77.1%), and in the 25% at greatest risk, predicted mortality rate was 75.7% (actual mortality rate, 62.7%). Thus, retrospectively at one institution and prospectively at another, the equation generated by this model based only on data available at the time of weaning from bypass was able to define one subgroup of patients 2.6 to 2.7 times as likely to die as another subgroup from within similar cohorts.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Improved multiorgan function after prolonged univentricular support.

Eleven cardiac transplant candidates (all male; mean age, 43.3 years) with multiorgan (hepatic, pulmonary, and/or renal) dysfunction were sustained for prolonged periods (> 30 days) with the HeartMate (Thermo Cardiosystems, Inc, Woburn, MA) left ventricular assist device. We evaluated the effect of extended support on end-organ recovery and on the ultimate outcome of cardiac transplantation. In addition to cardiac failure, 9 patients had hepatic dysfunction, 8 had pulmonary dysfunction, and 6 had renal dysfunction (4 of whom required hemodialysis before left ventricular assist device support). Mean duration of support was 115 days (range, 31 to 233 days). All patients underwent successful transplantation; 10 of these patients survived a mean of 24 months. One patient, who had required hemodialysis and ventilatory support during and after support, experienced progressive multiorgan failure and died 7 weeks after transplantation. Two late deaths after transplantation were unrelated to the device. Overall, patients experienced improvement in cardiac functional class status, and most participated in cardiac rehabilitation programs before transplantation. During left ventricular assist device support, hepatic function returned to normal in 8 patients, pulmonary function recovered in 7, and renal function returned to normal in 4. One patient who required hemodialysis underwent renal transplantation after cardiac transplantation and had complete recovery of renal function. In the current era of donor shortages, gravely ill patients can benefit from a strategy of prolonged left ventricular assist device support. This strategy has proved safe, has allowed for reversal of multiorgan dysfunction, and has produced healthier transplant candidates.

Adult↗
PubMed1993

Chronic left ventricular support with a vented electric assist device.

Based on the success of the pneumatically powered HeartMate (Thermo Cardiosystems Inc, Woburn, MA) left ventricular assist device, researchers at the Texas Heart Institute have begun conducting clinical studies of the vented electric model in bridge-to-transplantation procedures. Like the pneumatic device, the electric device is implanted intraperitoneally, but the blood pump is powered through a percutaneous lead that is connected to two rechargeable batteries. The batteries are worn in a shoulder holster; thus, patients are not tethered to a control console and are fully mobile. Two patients are currently undergoing left ventricular support with the vented electric HeartMate (duration of support, 315 days and 112 days) as they await cardiac transplantation, and they seem to be medically fit for outpatient care and follow-up. This technology may eventually allow selected patients to receive long-term support as a substitute for cardiac transplantation.

Electric Power Supplies↗
PubMed1993

Postcardiotomy LVAD support and transesophageal echocardiography in a child.

A case of postcardiotomy cardiogenic shock after repair of a congenital ventricular septal defect in a 5-year-old boy is reported. Mechanical circulatory support, instituted with a centrifugal left ventricular assist device, adequately supported the patient for 50 hours until recovery of native left ventricular function occurred. Transesophageal echocardiography proved to be useful in assessment of left ventricular function, allowing for timely institution and withdrawal of mechanical circulatory support.

Child, Preschool↗
PubMed1993

Why referred potential heart donors aren't used.

Heart donor demand far exceeds supply. We evaluated donor referrals to 1 organ procurement agency in an attempt to determine why many potential cardiac donors are not used. Of 430 referrals between September 1989 and August 1991, 169 hearts (39%) were harvested. In potential donors ultimately not yielding a heart, 38.7% were unavailable because the family refused to consent to organ donation, 36% were medically unsuitable, and 16.1% did not meet standard brain death criteria. Of the 94 donors not used for medical reasons, 43.6% had cardiac arrest, 17% had hypotension, 12.8% were drug abusers, 6.4% had sepsis, 5.3% had hepatitis, 5.3% had an acute myocardial infarction, 3.2% had low ejection fraction levels, and 2.1% tested positive for human immunodeficiency virus or syphilis (4.3% were not specified). A significant difference (p = 0.001) in racial distribution surfaced; Blacks and Hispanics constituted 27.2% of the donor group but 46.3% of the non-donor group. These data confirm that strategies must be created to continue educating the public and physicians in order to increase consent rates, optimize donor selection, and improve physician awareness of brain death criteria.

Adult↗
PubMed1993

Peripheral organ perfusion augmentation during left ventricular failure. A controlled bovine comparison between the intraaortic balloon pump and the Hemopump.

Despite the use of inotropic therapy and the intraaortic balloon pump (IABP), inadequate peripheral organ perfusion and subsequent multiorgan failure from left ventricular dysfunction is a major cause of death following cardiac surgery. To compare the end-organ perfusion provided by the IABP with that of the recently developed Hemopump Cardiac Assist System, blood flow from visceral organs was measured by ultrasonic flow probes during separate periods of support with each of these pumps. Ten calves underwent coronary artery ligations with beta-receptor blockade; hemodynamic parameters were recorded before the induction of failure, during unsupported cardiac failure, and during Hemopump and IABP support. Improvement in mean cardiac output, mixed venous oxygen saturation, and pulmonary artery wedge pressure was significantly greater (p < 0.05) during Hemopump support than during IABP support. Renal artery flow was significantly greater during Hemopump support (276 +/- 74.2 cc/min) than during IABP support (164 +/- 79.6 cc/min). Hepatic artery flow was significantly greater during Hemopump support (34.7 +/- 25.7 cc/min) than during IABP support (24.4 +/- 18.9 cc/min), and portal vein flow was significantly greater during Hemopump support (1588 +/- 315 cc/min) than IABP support (1259 +/- 310 cc/min). There were no significant differences, however, between carotid artery flow during Hemopump support (292 +/- 171 cc/min) and that during IABP support (317 +/- 204 cc/min). We conclude that renal, hepatic, and mesenteric perfusion provided by the nonpulsatile Hemopump is superior to that of the IABP in this bovine model of left ventricular failure. Therefore, the Hemopump may be more effective in preventing multiorgan failure during recovery of ventricular function.

Animals↗
PubMed1993

The lining of textured surfaces in implantable left ventricular assist devices. An immunocytochemical and electronmicroscopic study.

OBJECTIVE: The aim was to examine and identify some components of biological linings developed upon the textured surfaces of a circulatory assist device. The development of biological linings upon a textured surface circulatory assist device was evaluated in patients implanted for periods ranging from 84 to 132 days. METHODS: Explanted devices were examined macroscopically. Light microscopy, transmission electron microscopy and immunocytochemistry techniques were employed to evaluate the histogenesis of the tissue deposits upon the device surfaces. Visible material was essentially limited to focal areas upon the static housing and the periphery of the pusher-plate diaphragm (Biomer). RESULTS: Microscopy of the linings showed fibrin-rich areas with platelets, monocytes and few spindle-shaped surface cells. Central areas were composed of multiple layers of spindle-shaped cells separated, mainly, by collagen. Giant-cell foreign-body reaction to Biomer fibrils was seen. CONCLUSION: Transmission electron microscopy and immunocytochemistry indicated the presence of at least two cell populations: fibroblasts and smooth muscle-like cells, or 'myofibroblasts'. There was no evidence of endothelial cell presence.

Adult↗
PubMed1993

Immunochemical identification of human endothelial cells on the lining of a ventricular assist device.

We are studying the biologic (pseudointimal) lining that forms in the HeartMate (Thermo Cardiosystems, Inc.; Woburn, Massachusetts, USA), a left ventricular assist device with a pusher-plate blood pump, housed in solid titanium with uniquely textured blood-contacting surfaces. Sintered titanium microspheres cover the rigid surface, and integrally textured polyurethane lines the flexing diaphragm. The texture of the blood-contacting surfaces is designed to encourage formation of a biologic pseudointimal lining, which greatly reduces the risk of thromboembolic complications. We performed immunochemical analyses to characterize precisely the pseudointimal lining. Samples were taken from 2 explanted pumps; 1 had supported a patient for 132 days and the other, 189 days. The samples were cultured to detect factor-VIII-related antigen (von Willebrand factor), acetyl low-density lipoprotein receptors, smooth-muscle-cell actin, and surface adhesion molecules specific for monocytes/macrophages. Macrophage cells were predominant in both pumps, but in the 2nd pump, cultures from the center of the diaphragm were positive for acetyl low-density lipoprotein receptor and von Willebrand factor, indicating the presence of endothelial cells. We believe that blood-borne endothelial cells or endothelial cell precursors were deposited on the blood-contacting surfaces, which is an important clinical finding with regard to lowering the risk of thromboembolic complications and reducing the need for systemic anticoagulation in long-term left ventricular assist device patients.

Actins↗
PubMed1993

An ex vivo model for the reperfusion of explanted human hearts.

A model of an ex vivo-reperfused human heart was developed by using a modified Langendorff coronary perfusion circuit. The technical and physiologic aspects of reestablishing myocardial contractility are described. Preliminary studies were conducted in animals. In the present study, we obtained 12 human hearts that had been arrested with cardioplegic solution and excised from cardiac transplant recipients. The perfusate contained type-specific human donor red blood cells in a lactated Ringer's solution containing 5% dextrose. Myocardial contractility was successfully reestablished in 11 hearts and sustained for an average of 98 minutes (range, 79 to 180 minutes) at a coronary perfusion pressure of 80 mmHg. Left ventricular contraction pressures reached 40 mmHg (against intraventricular balloons at an internal pressure of 50 to 75 mmHg). Partial oxygen pressure (PO2) dropped significantly across the empty beating myocardium (from 498 +/- 40 mmHg to 219 +/- 53 mmHg [mean +/- SD]), but no significant change in hemoglobin saturation was observed. Myocardial failure generally stemmed from edematous changes leading to progressive impairment of myocardial relaxation. The intracoronary insertion of over-the-wire catheters did not adversely affect myocardial function. In conclusion, an ex vivo-supported human heart model has been developed that may have a number of applications, including the preclinical evaluation of new interventional diagnostic and therapeutic techniques aimed at the coronary circulation, and the investigation of myocardial mechanics, preservation, and metabolism.

Adult↗
PubMed1992

Preliminary results of intraoperative excimer laser angioplasty: phase 1: an adjunct to coronary artery bypass surgery.

The excimer laser underwent phase I clinical trials at three centers to determine its safety for intraoperative coronary laser angioplasty as an adjunct to coronary artery bypass grafting. A 308-nm Xenon-Chloride, pulsed-wave excimer laser was used to perform angioplasty in 30 patients undergoing coronary artery bypass surgery. Forty vessels (30 patients) were treated, in which the extent of occlusion ranged from 30% to 100%, with complete occlusion in 40% of all vessels. Improvement in vessel luminal caliber was achieved in 33 (79%) vessels, with perforations occurring in 4 (12%) vessels, 2 of which required surgical repair. The lumens of the remaining 8 (19%) vessels were not enlarged, and 2 (5%) of these vessels were perforated. Luminal enlargement was most often achieved in totalled occluded vessels in which 16/17 (94%) were recanalized. No patients died within 30 days postoperatively. Five patients demonstrated biochemical and electrocardiographic evidence of myocardial injury 48 hr postoperatively, and one patient died of cardiac arrest 139 days postoperatively. On the basis of these results, we believe that excimer laser angioplasty can be performed safely to improve coronary luminal patency, even in totally occluded vessels, in an operative setting. The long-term value of this procedure remains to be elucidated.

Aged↗