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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↗
PubMed1989

Bridging to cardiac transplantation.

Unilateral or bilateral prosthetic ventricles and artificial hearts have been used in bridging to transplantation for 4 years. Candidates for bridging to transplantation comprise patients who otherwise would be elective cardiac transplantation candidates who deteriorate rapidly before a donor heart can be found, or persons with sudden cardiac decompensation (eg, massive myocardial infarction with cardiogenic shock). In selecting patients for bridging to cardiac transplantation it is crucial that people are chosen who are good candidates for heart transplantation despite their rapidly deteriorating condition. This article compares the results of the devices available for use in this application, which include: the centrifugal pump; the Jarvik-7 orthotopic prosthetic ventricle; and the Thoratec, Novacor, and Thermedics heterotopic prosthetic ventricles.

Adolescent↗
PubMed1989

Acute ischemic ventricular septal defect.

Thirty-one published reports (366 patients) and 48 consecutive patients treated for postinfarction ventricular septal defect at four institutions in northern California were reviewed. Overall hospital mortality was 43% in the reviewed group and was not affected by age, concomitant myocardial revascularization, date of operation, presence of cardiogenic shock, or location of the defect. Mortality for the 48 consecutive patients, all of whom had surgery within 30 days of acute infarction, was 67%. Although there were no survivors over 65 years of age, mortality was not affected by age, location of the ventricular septal defect, or concomitant myocardial revascularization.

Heart Rupture↗
PubMed1989

Successful biventricular circulatory support as a bridge to cardiac transplantation during prolonged ventricular fibrillation and asystole.

The indications for biventricular versus left ventricular mechanical circulatory support as a bridge to cardiac transplantation are not well established. In this study, 27 potential heart transplant candidates who were in imminent risk of dying before donor heart procurement were implanted with Thoratec prosthetic ventricles (21 biventricular and six left ventricular) at three medical centers. A total of 21 patients (16 biventricular and five left ventricular) underwent successful cardiac transplantation after 1-65 days of circulatory support, and 19 were discharged from the hospital. Seven of the patients (all biventricular; diagnoses: four cardiomyopathy, two acute myocardial infarction, one end-stage coronary artery disease plus acute myocardial infarction) had prolonged arrhythmias that normally would have been lethal (six cases of ventricular fibrillation from 2 to 22 days, one asystole for 3 hours), but complete support of the systemic and pulmonary circulations was maintained in all seven patients with biventricular devices. Mean systemic blood flow during this period (4.6 +/- 0.6 l/min) was unchanged compared with that during sinus rhythm. Six of these patients survived to receive heart transplants. The use of right plus left prosthetic ventricles does not prevent the occurrence of arrhythmias but removes the threat and simplifies patient management. We conclude that biventricular support is indicated in bridge-to-transplant patients with potentially lethal arrhythmias.

Adult↗
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↗