Search PubMed⌕ Search

Biomedical subjects

W S Pierce

Publications and source records attributed to W S Pierce.

At least 109 records · Page 6Linked to original sources
PubMed1981

Fusion of prosthetic valve during left heart bypass.

We recently utilized a left ventricular assist device in a patient who could not be separated from cardiopulmonary bypass after aortic and mitral valve replacement. The nonfunctioning pericardial aortic valve became completely occluded owing to a fibrinous fusion of the valve leaflets during the 8-day period of assist pumping. A second operation was required to open the fused valve leaflets. This experience suggests that special care should be taken in selecting an aortic valve prosthesis in a patient who may require the left ventricular assist device in order to be separated from cardiopulmonary bypass.

Aortic Valve Insufficiency↗
PubMed1981

Approaches to the artificial heart. Invited speaker.

Over the last two decades, the implantable artificial heart has evolved from an idea to a device capable of completely supporting the circulation for periods now exceeding 5 months. Although initial animal studies were limited by thromboembolism and device breakage, the usual causes of death in experimental animals are now infection, atrioventricular valve obstruction, elastomer bladder calcification, or inadequate cardiac output because of the relatively rapid growth of the young calves. As a result of the bulky nature of the energy converter and the substantial risk of infection with large diameter percutaneous tubes, clinical use of their air-powered artificial hearts will be limited to patients who are awaiting or being prepared for heart transplantation. Artificial hearts with implanted energy converters are being developed for permanent heart replacement. These devices require well-designed, durable mechanical components and sophisticated control systems. Although initial designs centered around thermal engines powered by a completely implantable nuclear energy source, the excessive cost and potential dangers have shifted the focus away from the nuclear system. Several electrically driven artificial hearts, based on samarium-cobalt magnet brushless direct-current motors, are now undergoing bench testing and will be ready for long-term animal studies within 2 years. This research will culminate with the availability of an "off-the-shelf" electrically powered artificial heart for use in patients with a wide range of nonrepairable forms of end-stage heart disease.

Animals↗
PubMed1981

Cardiogenic shock due to ventricular rupture. A surgical approach.

Following a posterolateral myocardial infarction, a 57-year-old man developed severe shock which did not respond to catecholamine infusion and intra-aortic balloon counterpulsation. Implantation of a left ventricular assist pump was planned, but at sternotomy free ventricular rupture was identified and repaired. Repair of free-wall ventricular rupture is uncommon because of infrequent antemortem diagnosis. A more aggressive surgical approach of instituting left ventricular assist pumping in those patients with cardiogenic shock refractory to medical therapy and intra-aortic balloon pumping should yield the additional benefit of repair of the rather common but rarely recognized lesion of ventricular rupture.

Heart Rupture↗
PubMed1980

Calcification inside artificial hearts: inhibition by warfarin-sodium.

Intracavitary calcium phosphate deposits were observed in smooth, elastomeric blood pump sacs implanted in male calves for periods of 115 to 166 days. These deposits occurred predominantly on the flexing surface of the sacs. In contrast, similar pump sacs remained generally free of mineral deposits for up to 150 days in calves treated with the anticoagulant warfarin-sodium. These results implicate a vitamin K-dependent process in calcium phosphate deposition on elastomeric sacs.

Animals↗
PubMed1980

Pathogenesis of paradoxical hypertension after coarctation repair.

A recent review of 25 patients who had repair of coarctation of the aorta at the Milton S. Hershey Medical Center revealed a 56% incidence of paradoxical hypertension in the immediate postoperative period. Analysis of results from recent animal experiments helped us to formulate a logical explanation of the pathogenesis of this hypertension. Stimulation of sympathetic nerve fibers located between the media and adventitia of the aortic isthmus has two effects, both of which result in hypertension. The first effect is release of norepinephrine and consequential rise in systemic blood pressure. Second, this spinal reflex directly stimulates the juxtaglomerular cells to release renin and cause additional hypertension. An additional effect of this increased renin production might be the shunting of blood from mesenteric arteries, thus causing the abdominal symptoms of so-called post-coarctectomy syndrome. The inability of some patients to adapt to this spinal reflex may be related to the age of the patient when the coarctation was repaired. This probably explains the high incidence of persistent hypertension in patients who undergo coarctation repair after adolescence.

Adolescent↗
PubMed1980

Mechanical circulatory assistance for postoperative cardiogenic shock: a three year experience.

Retrospective analysis of 14 patients undergoing circulatory support for postcardiotomy cardiogenic shock during the past 3 yrs has demonstrated the ability of the profoundly depressed myocardium to recover. Four patients were totally weaned from circulatory support and 2 are long-term survivors. Our results suggest that improved survival is dependent on the absence of certain peri-operative complications. To improve future clinical results we suggest that prompt application of assist pumping is necessary to eliminate prolonged cardiopulmonary bypass times and subsequent massive bleeding; those circulatory support systems requiring systemic anticoagulation are of no value in the treatment of postcardiotomy cardiogenic shock; the use of atrial cannulation may be advantageous in certain patients to eliminate critical inflow obstruction, further prolongation of cardiopulmonary bypass, and additional myocardial damage; and that the high incidence of right ventricular failure that is refractory to medical therapy makes the ability to support both ventricles mandatory.

Adult↗
PubMed1980

Pulsatile prosthetic valve flows.

The laser Doppler system has been established as a useful tool for eliciting the properties of simulated cardiovascular flows, and thus for comparative studies of flow properties of prosthetic valves. Significant differences among valve types and between models of one type have been documented. The complex variations of velocity profiles with time show that comparisons must be made for unsteady pulsatile rather than steady flow, despite the volume and complexity of the data required. Future studies will include methods of compacting the data presentation and improving the details of the experimental stimulation.

Blood Flow Velocity↗
PubMed1979

Laser Doppler anemometer studies in unsteady ventricular flows.

The laser Doppler technique was employed to obtain intraventricular velocity distributions on the basis of in vivo confirmation of previous in vitro flow visualization predictions. The quasi-steady assumption required for quantification of flow visualization results is unsatisfactory in regions of high acceleration and fluctuating velocities are unavailable via such techniques. Mean and fluctuating velocity profiles were obtained in a pneumatically driven prosthetic ventricle with the laser Doppler anemometer and stress levels estimated. The preliminary data presented here illustrates that the technique can be applied to such flows. The measurement and data reduction schemes are applicable to a wide range of simulated cardiovascular flows. The particular application to prosthetic ventricle design should minimize the number of in vivo experiments required to develop a satisfactory blood pump and aid in tailoring pump actuation protocols for minimum thromboembolic complications.

Blood Flow Velocity↗
PubMed1979

Total artificial heart implantation in calves with pump on an angled port design.

The APP was employed in our 21st TAH calf and has now been implanted in a total of 11 animals. The APP has a dynamic stroke volume of 105 ml, an ejection fraction of 75%, and a peak flow of 14 L/min. The TAH features 2 APPs which have polysulfone cases and contain smooth, seam-free polyurethane sacs. Concavoconvex Bjork-Shiley valves are used. The pumps are pneumatically driven but may be easily converted to pusher-plate drive. A pneumatic drive console and an automatic control unit complete the system. The automatic control unit permits independent control of the right and left hearts as a function of left atrial and aortic pressure respectively. The average survival of the APP TAH calves has been 65 days. Hematologic study has revealed basically normal results with minimal elevation of serum hemoglobin and lactic acid dehydrogenase (LDH), indicative of a low level of hemolysis. Elelvation of central venous pressure (CVP) and total blood volume continue to be a problem with some TAH calves but not all. The APP has led to a dramatic increase in duration of survival and decrease in thromboembolism.

Animals↗
PubMed1979

Recurrent pulmonary emboli secondary to right atrial thrombus around a permanent pacing catheter: a case report and review of the literature.

This report describes the management of a woman with multiple pulmonary emboli secondary to a large right atrial clot which had formed around her permanent transvenous pacemaker. She continued to have pulmonary emboli despite adequate anticoagulation. Removal of the catheter and pacing required right atriotomy under cover of cardiopulmonary bypass. Additionally, eight English language case reports of symptomatic pericatheter thromboses are reviewed. In these cases, pericatheter clot resulted either in right-sided inlet obstruction or pulmonary emboli. The mortality rate was 75%. Although the cause for our patent's thromboembolic events is uncertain, congestive heart failure was a predisposing factor in 75% of the other reported cases. We suggest that pacemaker patients in congestive heart failure might benefit greatly from chronic anticoagulation.

Aged↗
PubMed1979

Reduction of myocardial infarct size: comparison between left atrial and left ventricular bypass.

A controlled study was undertaken to quantitate and compare the effect of left ventricular bypass (LVB) and left atrial bypass (LAB on left ventricular infarct volume (LVIV). After baseline studies, the left anterior descending coronary artery in each of 30 mongrel dogs was ligated 1-1.5 cm from its origin. After baseline ischemic studies, control dogs (group 1--10 dogs), LAB dogs (group 2--10 dogs), and LVB dogs (group 3--10 dogs) were monitored for four hours. Final infarct size was determined by the nitroblue tetrazolium staining technique. Heart rate, mean arterial pressure, and total systemic flow (TSF) showed no significant difference between control and left heart bypass groups. In group 1, the LVIV was 27.7 +/- 6.5 g/100 g left ventricle (LV). In group 2, left heart bypass (LHB) flow was 90 +/- 4% of TSF. The pressure time index (PTI) was 2845 +/- 52 mm Hg-sec/min. The PTI demonstrated no significant difference from cntrols. In group 2, LVIV was 22.5 +/- 6.0 g/100 g LV. LVIV was reduced 18.8% from controls (p less than 0.08). In group 2, LHB was complete. Left ventricular decompression (group 3) resulted in a PTI of 328 +/- 76 mm Hg-sec/min. The PTI was significantly different (p less than 0.001) from groups 1 and 2. The LVIV was 12.6 +/- 5.1 g/100 g LV. LVIV was reduced 54.5% from controls (p less than 0.001) and 44.0% from group 2 (p less than 0.001). These results suggest that LVB may be useful, not only in supporting the circulation in the patient with myocardial infarct and cardiogenic shock, but also in limiting infarct size.

Animals↗
PubMed1979

Modified Shumacker repair of transposition of the great arteries.

Seven infants weighing from 6.4 to 10.3 kg underwent correction of transposition of the great arteries by the venous transposition operation as described by Shumacker. In this operation, a new atrial septum is constructed using a bipedicled right atrial flap, and the lateral atrial wall is constructed using a viable pericardial flap. Three of the patients had an associated ventricular septal defect. Six of the seven patients survived and have had an excellent clinical result. Although atrial arrhythmias were common in the early postoperative period, all patients are now in sinus rhythm. Two patients have had postoperative cardiac catheterization and cineangiography, which showed excellent hemodynamic results. The modified Shumacker operation preserves two of the three internodal pathways, provides a compliant, viable atrial septum, and permits fabrication of a generous-size physiological left atrium. This appears to offer advantages not present in the Mustard procedure.

Angiocardiography↗