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Biomedical subjects

J D Hill

Publications and source records attributed to J D Hill.

At least 19 recordsLinked to original sources
PubMed1991

Effects of acute right ventricular ischemia on ventricular interactions during prosthetic left ventricular support.

Systolic ventricular interactions may be partially responsible for right ventricular failure that sometimes occurs during clinical use of prosthetic left ventricular assist devices. In this hypothesis, it is proposed that the left ventricular assist device reduces left ventricular pressure and its contribution to right ventricular performance, thus impairing right ventricular output. On the other hand, these effects may be small compared with other causes of right ventricular failure such as ischemia. To test the systolic interaction hypothesis in the normal and ischemic right ventricle, we used a left ventricular assist device to pressure unload the left ventricle of anesthetized pigs, and we compared its effect on right heart function before and after 2 minutes of acute right coronary artery occlusion as a model of right heart failure. Pigs were instrumented for measurements of septal to left ventricular and right ventricular free wall dimensions with ultrasonic crystals, ventricular chamber pressures, and cardiac output with a pulmonary artery blood flow probe. Without right ventricular ischemia, the left ventricular assist device produced an 80% +/- 6% reduction in left ventricular pressure-time integral while maintaining aortic pressure. This resulted in a leftward septal shift with an 11.6% +/- 1.8% decrease in left ventricular septal-to-free wall dimension and a 12.5% +/- 2.4% increase in right ventricular septal-to-free wall dimension, with no changes in right ventricular cardiac output or stroke work. In contrast, right coronary artery occlusion alone produced right heart failure, with a 50% +/- 6% reduction in right ventricular global stroke work and 26% +/- 6% and 27% +/- 3% reductions in cardiac output and right ventricular peak systolic pressure, respectively. This right heart failure persisted during left ventricular unloading with the left ventricular assist device, which resulted in further leftward septal shifting and unchanged but still depressed stroke work and flow output. These findings support the hypothesis that a preexisting pathologic condition is the dominant factor in determining right ventricular function during prosthetic left ventricular support and that direct anatomic interactions play a minor role.

Animals↗
PubMed1990

Optimal cardioplegia and 24-hour heart storage with simplified UW solution containing polyethylene glycol.

Recent work has shown that UW may be better than standard cardioplegic solutions for short-term heart preservation. In this study we have used a rabbit heart model to evaluate a simplified UW solution in which penicillin, dexamethasone, insulin, allopurinol, and adenosine were omitted and 5% polyethylene glycol (PEG20M) was substituted for hydroxyethyl starch. The test systems consisted of 4-hr cardioplegic storage at 15 degrees C with repeated flushing every 30 min for 2 hr and 24-hr hypoxic low-flow microperfusion (3 ml/g/24 hr) at 0 degrees C. Control groups were arrested with a 15-25 ml flush in iced saline and immediately tested. Cardiac output (CO)* after preservation was measured in a working heart model using an acellular perfusate at 37 degrees C at an aortic pressure of 100 cm H2O. The CO (ml/g heart wt/min) were as follows--Controls: St. Thomas II 20.5 +/- 8.3 (5), UW 34.7 +/- 11.7 (16), PEG20M 41.8 +/- 4.4 (14); 4-hr cardioplegia: St. Thomas II 17.4 +/- 0.9 (4), Bretschneider HTK 14.9 +/- 7.0 (4), UW 25.2 +/- 11.5 (9), PEG20M 41.1 +/- 7.8 (8); 24-hr microperfusion: UW 25.4 +/- 11.1 (18), PEG20M 37.1 +/- 8.2 (18). Following cardioplegic or microperfusion preservation, PEG20M hearts functioned at control levels (P greater than 0.05) and were significantly superior to all other solutions, with approximately double the CO (P less than 0.05, all other groups). We conclude that for heart preservation, 5 components can be eliminated from UW and substitution of PEG20M for HES appears to have improved its performance.

Animals↗
PubMed1990

Enhancing the self-esteem of inpatient alcoholics.

This study examined the effect of pairing inpatient alcoholics with nursing home residents (NHRs) on the alcoholics' self-esteem. In this PALS program, the alcoholic inpatients assumed a helping-companion relationship with the NHRs for 2 hr per day during their last 2 weeks of treatment. Fifty alcoholic inpatients were randomly assigned to the PALS program (n = 25) or to the library for free reading time (n = 25). The Tennessee Self-Concept Scale (TSCS) was administered to all subjects in both groups before and after the interventions. Of the nine TSCS scales, the improvement on the Moral-Ethical scale was significantly greater in the PALS group. Because the alcoholic inpatients in the PALS group engaged in altruistic (moral) behavior, this study provides a logical link between the intervention and the outcome, which has been a prevalent weakness in previous studies of self-esteem in alcoholics.

Alcoholism↗
PubMed1990

Neurologic complications of cardiac transplantation.

Between 1984 and 1989, orthotopic cardiac transplantations were done in 90 patients from 10 to 65 years of age for end-stage, refractory congestive cardiomyopathy. Two patients had had ischemic strokes 5 months and 18 years, respectively, before transplantation. Six patients (7%) suffered acute neurologic events perioperatively. Three patients suffered cerebral infarctions. In 1 case this occurred 10 days before transplantation--probably as a result of systemic hypoperfusion--with the placement of ventricular assist devices. Two others suffered infarctions 5 and 21 days, respectively, after transplantation, each of probable embolic origin. Two patients had an acute intracerebral hemorrhage 21 and 36 days, respectively, after transplantation; both were located within the basal ganglia and subcortical regions. Both patients had moderate to severe hypertension, and in 1, renal failure and a coagulopathy developed before hemorrhage. Tremor, seizures, and an altered level of consciousness developed in 1 patient as an apparent toxic reaction to cyclosporine treatment. Only 1 patient died as a result of the neurologic complication--of an acute intracerebral hemorrhage. Three patients recovered fully, 2 partially. Only the case of drug toxicity could be directly attributed to the transplantation procedure itself. We conclude that the risk of an acute neurologic insult with orthotopic cardiac transplantation is low but may result from drug toxicity, cerebral ischemia, or hemorrhagic mechanisms.

Adolescent↗
PubMed1979

Extracorporeal membrane oxygenation in severe acute respiratory failure. A randomized prospective study.

Nine medical centers collaborated in a prospective randomized study to evaluate prolonged extracorporeal membrane oxygenation (ECMO) as a therapy for severe acute respiratory failure (ARF). Ninety adult patients were selected by common criteria of arterial hypoxemia and treated with either conventional mechanical ventilation (48 patients) or mechanical ventilation supplemented with partial venoarterial bypass (42 patients). Four patients in each group survived. The majority of patients suffered acute bacterial or viral pneumonia (57%). All nine patients with pulmonary embolism and six patients with posttraumatic acute respiratory failure died. The majority of patients died of progressive reduction of transpulmonary gas exchange and decreased compliance due to diffuse pulmonary inflammation, necrosis, and fibrosis. We conclude that ECMO can support respiratory gas exchange but did not increase the probability of long-term survival in patients with severe ARF.

Acute Disease↗
PubMed1979

Aortic stenosis complicated by severe calcification of the wall of the ascending and transverse aorta: management by use of left ventricular to aortic composite conduit. Report of two cases.

The use of left ventricular aortic composite conduits in 2 patients with severe intramural calcification of both the ascending and the transverse aorta is reported. This method is felt to be superior to conventional aortic valve replacement, when the texture of the aortic wall does not allow cross clamping or secure closure.

Aged↗
PubMed1979

Management of ascending suture line sepsis by excision on the ascending aorta and insertion of a left ventricular apex to aorta conduit.

A new technique used in the management of infection of an aortic suture line following aortic valve replacement and subsequent episodes of severe hemorrhage resulting from suture line disruption is described. In a planned, staged procedure, a left-ventricular-apex-to-aorta conduit was inserted followed by excision of the supracoronary aortic root and ascending aorta, incorporating all infected tissue. This technique demonstrates that near total excision of the ascending aorta is possible and coronary artery flow can be maintained with only a minimal supravalvular aortic chamber.

Aorta, Thoracic↗
PubMed1979

Platelet turnover studies associated with left ventricular assist device (LVAD) implantation.

Calves given LVADs have been studied to determine changes in platelet turnover induced by the device and modified by time and anticoagulants. Passivation with time occurs but is surprisingly incomplete even one month later and despite coumadin, aspirin and dipyridamole. Without these drugs, enhanced platelet turnover and local thrombus formation on the device is exaggerated. Sequential platelet turnover studies may be useful to quantitate, monitor and/or predict thromboembolic events.

Animals↗
PubMed1979

A volume sensor for a pneumatically driven LVAD.

The volume sensor has proven to be a valuable tool in the operation and characterization of our pneumatically driven LVAD. It compensates for the decoupling between driver and LVAD that occurs in pneumatically actuated LVADs due to gas compressibility. Uses to which we have put the volume sensor represent only a small fraction of the potential applications. Additional uses contemplated include: Use as an alternate or backup for the R-wave detection network currently used to achieve synchronization with the natural heart. This could be done by starting the LVAD ejection phase when the filling flow rate drops below a given threshold, indicating that the left ventricle has finished filling the LVAD. Use for feedback for closed loop control of plate motion. Such control could reduce actuation delays without overdriving the LVAD. Use as a diagnostic tool to aid in the study of the LVAD and its interaction with the cardiovascular system. When used in conjunction with information on left ventricular, aortic, and drive pressures, it is possible to determine the resistance, inertia and compliant characteristics of the major elements of the LVAD and the vascular system to which it is joined.

Assisted Circulation↗
PubMed1978

A randomised trial of home-versus-hospital management for patients with suspected myocardial infarction.

Home and hospital management of patients with suspected myocardial infarction were compared in a randomised trial in which a hospital-based team responded to calls from general practitioners. 500 calls were received, and 349 patients (70%) were suspected of having myocardial infarction. Of these, 24% were excluded from the trial on predetermined medical and social grounds; for the remainder (76%) there was no significant difference in the 6-week mortality between the home group (13%) and the hospital group (11%). For the majority of patients to whom a general practitioner is called because of suspected infarction, hospital admission confers no clear advantage.

Adult↗
PubMed1978

Immune mechanisms in patients with proven vascular disease.

Lymphocyte transformation and serum levels of immunoglobulins and complement were measured in groups of patients with old myocardial infarction, with peripheral vascular disease and in age- and sex-matched controls. There were no significant differences between the groups in phytohaemagglutinin (PHA) induced lymphocyte transformation, in IgA or in serum complement levels. The levels of IgG and IgM were significantly raised in patients with old proven infarcts while the level of IgM was raised in patients with peripheral vascular disease.

Complement System Proteins↗
PubMed1978

Thrombosis and degeneration of Hancock valves: clinical and pathological findings.

Of 415 Hancock valves implanted in 370 patients, 26 valve specimens were recovered at postmortem examination and 8 at reoperation. In 9 of these 34, thrombosis had formed without apparent alteration of the heterograft tissue (Group A). All were mitral prostheses, and the thrombi were attached to the sewing ring. Six of the patients died in the early postoperative period following prolonged low cardiac output syndrome and coagulation disturbances. Three patients had late valve thrombosis 12 to 26 months after operation and were in chronic atrial fibrillation with a very large left atrium. Four valve specimens (Group B) demonstrated degenerative changes of the heterograft leaflets such as shrinkage, perforation, and calcification. The clinical courses and possible pathogenesis are discussed.

Aged↗
PubMed1978

Chest physical therapy procedures in open heart surgery.

Chest physical therapy is now widely used after open heart surgery to prevent secondary pathology in the lungs and to improve the phhysical condition of the patient. A brief overview of cardiac surgery is presented. Factors occurring before, during, and after surgery that contribute to postoperative respiratory insufficiency are outlined, and a comprehensive three-phase treatment program is described. Also, treatment guidelines, precautions, and contraindications are discussed.

Cardiac Surgical Procedures↗
PubMed1978

Surgery of tumors of the subdiaphragmatic inferior vena cava. Report of two cases and review of the literature.

Two cases of obstruction of the hepatic inferior vena cava (IVC) are presented. In Case 1, the obstruction was due to a calcified thrombus which presumably developed after lower limb trauma 19 months previously. Complete surgical correction was achieved with the aid of deep hypothermia and circulatory arrest. In Case 2, a right atrial tumor was mimicked by a propagating malignant hepatoma. Palliative removal of the tumor cleared the IVC passage. The etiology of tumors of the IVC and their surgical management are discussed.

Aged↗