Search PubMed⌕ Search

Biomedical subjects

W F Bernhard

Publications and source records attributed to W F Bernhard.

At least 19 recordsLinked to original sources
PubMed1991

Hemodynamic evaluation of a chronically implanted, electrically powered left ventricular assist system: responses to acute circulatory stress.

Hemodynamic stress testing was performed in four calves with a chronically implanted left ventricular assist device consisting of a double-valved pump interposed between the left ventricular apex and the descending thoracic aorta. The device was powered either pneumatically (n = 1) or with a transcutaneous energy transmission system (n = 3). Hemodynamic evaluation (cardiac output and right and left ventricular and pulmonary and carotid artery pressures) was carried out at baseline and during all hemodynamically stressed states. Atrial pacing and ventricular pacing to a heart rate of 140 beats/min resulted in no significant change in right or left heart filling pressures or cardiac output. Preload reduction with nitroprusside or transient inferior vena cava balloon occlusion resulted in a marked decrease in left ventricular pressure with preservation of mean arterial pressure. Phenylephrine administration resulted in a marked rise in mean arterial pressure with no change in cardiac output or filling pressure. Induction of ventricular fibrillation resulted in a decrease of mean left ventricular pressure to 11 +/- 8 mm Hg, but mean arterial pressure was maintained at greater than or equal to 50 mm Hg. It is concluded that a multicomponent, implantable, electrically powered assist system is capable of maintaining a normal cardiac output under a wide range of loading conditions and chronotropic states. Although this device is clearly preload dependent, it is capable of maintaining normal systemic pressures during conditions of severe left ventricular dysfunction and circulatory collapse.

Animals↗
PubMed1986

Long-term follow-up of valvotomy before 1968 for congenital aortic stenosis.

The clinical course of 59 patients who underwent valvotomy for aortic stenosis before 1968 was reviewed. All were older than 1 year at the time of operation. Mean follow-up period was 17.7 years. Forty-six patients are alive; 26 (57%) are 30 to 40 years and 6 (13%) are older. Actuarial analysis indicated that the probability of survival was 94% at 5 years and 77% at 22 years. Thirteen patients died, 7 suddenly. Among the latter, significant obstruction or regurgitation was present in the 4 who underwent catheterization 0.9 to 7.2 years before death, 2 of whom were symptomatic and 2 with progression of a strain pattern on electrocardiogram. Surgery was recommended but declined by the latter 2 patients. Reoperation was carried out in 21 patients (36%), 3 (12%) of whom died. Actuarial analysis revealed the probability of reoperation to increase from 2% at 5 years to 44% at 22 years. Bacterial endocarditis occurred on 4 occasions in 3 patients, 1 of whom died suddenly during treatment. The incidence of endocarditis was 3.8 episodes/1,000 patient-years. Actuarial analysis of serious events, defined as death, reoperation and endocarditis, with the most serious of these and each patient being represented only once, indicated the probability of being free of such an episode to be 92% at 5 years, decreasing to 39% at 22 years. These data emphasize the palliative nature of valvotomy and the meticulous follow-up so necessary in these patients.

Actuarial Analysis↗
PubMed1986

Clinical temporary ventricular assist. Pathologic findings and their implications in a multi-institutional study of 41 patients.

Forty-one patients, distributed among four centers, had left (33 patients), right (five), or bilateral (three) temporary ventricular assistance with textured (24) or smooth (17) surfaced diaphragm pumps, during an evaluation supported by the National Institutes of Health. Cardiac failure had occurred in 39 postoperative patients (after aorta-coronary bypass [23], valve replacement [four], both [nine], or other [three]), with total cardiopulmonary bypass time mean 306 minutes (range 69 to 600). Two patients had cardiomyopathy. Death of 35 nonsurvivors was due to myocardial necrosis (14), hemorrhage (nine), cerebrovascular accidents (three), infection (three), and other (six). Mean duration of support in all patients was 62 hours. In 16 patients (40%) whose condition improved, cardiac assist duration was mean 127 hours (range 48 to 264), compared with mean 19 hours (range 1 to 120) in 25 who did not. Of 17 patients in whom duration of support exceeded 72 hours, 15 (88%) improved, 11 were weaned, and six survived long term. Tissue examination (in 33 patients) by biopsy at pump implantation or autopsy revealed coagulation or contraction band myocyte necrosis, with or without hemorrhage, in 26 patients; of these, 10 improved and six were long-term survivors. Pump-related complications (two) included pulmonary embolism, most likely related to a cannulation site thrombus, and an aortic cannulation site infection in one patient each. This study suggests that mechanical cardiac assist may be accomplished with a low complication rate; should not necessarily be denied to patients with existing necrosis, because myocardial necrosis does not preclude improvement or survival; and frequently leads to functional myocardial recovery if patients survive early noncardiac complications, often the result of long duration of cardiopulmonary bypass.

Adolescent↗
PubMed1985

Long-term follow-up of postcardiotomy patients with profound cardiogenic shock treated with ventricular assist devices.

Success of ventricular assist devices in patients with postcardiotomy shock has provided enough survivors to allow evaluation of the length and quality of life. Fifteen survivors from 28 to 68 years (mean 53) old from four centers were followed for 6 to 77 months (mean 35) after discharge from the hospital. Four patients suffered perioperative myocardial infarctions. In three patients, ventricular function was normal before surgery and remained so afterward. Of 12 patients with moderate or severely impaired ventricular function, five improved, five were unchanged, and two were worse. One patient died 6 months after surgery of cardiomyopathy. Seven patients are employed full-time and one works part-time. Five patients are retired but active and one is moderately disabled. NYHA functional class improved in the patients as a group: 13 were in classes III and IV before surgery and 13 were in classes I and II after surgery. Two patients had noncardiac partial disability. Survivors of ventricular assist device support for postcardiotomy shock have an excellent chance for high-quality life and the risk of crippling cardiac disability is small.

Adult↗
PubMed1985

Onset and progression of experimental bioprosthetic heart valve calcification.

Calcification, the major cause of bioprosthetic heart valve failures, is a serious clinical problem with uncertain pathogenesis. The objectives of the present study were to define the progressive chemical and morphologic sequence of mineralization in glutaraldehyde-treated porcine aortic valve cusps implanted subcutaneously in rats and to compare the pathology and pathophysiology of calcification in subcutaneous implants with that of orthotopic valve replacements in calves. Cusps were implanted subcutaneously in 3-week-old rats for 24 hours to 18 weeks. Cuspal calcium was 114 +/- 18 micrograms/mg of dry weight (mean +/- SEM) at day 21 and 218 +/- 6 at day 56 of implantation and unchanged thereafter. The earliest mineral deposits, noted at 48 hours, were associated with devitalized porcine connective tissue cells, but by 7 days, mineral deposits also involved collagen bundles. Scanning electron microscopy with energy-dispersive x-ray analysis demonstrated predominant accumulation in the spongiosa with a spongiosa to fibrosa energy-dispersive x-ray analysis count ratio of calcium of 15 at 21 days. In stent-mounted glutaraldehyde-preserved porcine valves implanted in five calves as mitral replacements for 69 to 142 days, cuspal calcium was 86 micrograms/mg (mean) (range 47 to 128). Calf implants also had cell oriented and collagen calcification predominating in the valvar spongiosa. In both rat subcutaneous and calf mitral valve models, early diffuse calcific microcrystals evolved into confluent nodules that disrupted tissue architecture. It is concluded that calcification of glutaraldehyde-preserved porcine aortic valves implanted subcutaneously in rats begins within 48 hours, earliest deposits are localized to residual porcine connective tissue cells, but latter deposits also involve collagen fibrils, mineralization is most prominent in the spongiosa, the pathology of calcification in rat subcutaneous implants and calf mitral replacements is comparable, suggesting a common pathophysiology, and calcific nodule formation most likely initiates clinical features.

Animals↗
PubMed1984

Investigations with an implantable, electrically actuated ventricular assist device.

A permanent, implantable, circulatory support system for patients with irreversible cardiomyopathy is gradually becoming a reality. Progress has been achieved toward formation of a stable, nonthrombogenic, blood-prosthesis interface, and an electrically actuated ventricular assist device has reached an advanced stage of fabrication. The two most important components of the system, an electromechanical energy converter and a contiguous, pusher-plate, blood pump (stroke volume 85 ml) were employed in these studies. The energy converter consisted of a 50 volt, low-speed, brushless, torque motor and a mechanism to convert rotary motion into a pulsatile output. An electronic controller and variable-volume compliance chamber were not evaluated. Left ventricular bypass experiments were conducted in 13 calves for periods of 30 to 149 days. Preoperatively, four devices were inoculated with bovine, fetal fibroblasts to accelerate formation of a collagenous lining, and nine nonseeded pumps served as controls. The collagen-lined devices functioned for longer periods of time with unrestricted blood flow and no thromboembolic complications when compared to the control devices. Additional studies are contemplated employing a complete VAD system prior to undertaking preclinical trials.

Animals↗
PubMed1983

Fixed subaortic stenosis in the young: medical and surgical course in 83 patients.

Eighty-three patients aged 11 months to 25 years were followed up a median of 6.1 years (range 8 days to 24 years) after diagnosis of fixed subaortic stenosis (SAS). Fourteen (17%) had significant noncardiac defects and 47 (57%) had additional cardiac malformations. The left ventricular (LV) outflow gradient increased in 25 of 26 patients catheterized more than once before surgery. Of 15 patients less than 12 years old with gradients less than or equal to 40 mm Hg, 10 ultimately underwent operation after developing severe obstruction; another has progressed to a gradient of 45 mm Hg at 6 years of age. Before surgery (at a median age of 12 years), 55% had aortic regurgitation (AR), which was usually mild. Infective endocarditis occurred in 12% of the group, with a frequency of 14.3 cases per 1,000 patient-years. Seventy-four patients were operated on, with 6 early (8%) and 7 late (9%) deaths. Twelve underwent reoperation to relieve residual obstruction. Surgery reduced gradients in patients with discrete SAS from 83 +/- 33 to 29 +/- 30 mm Hg, but in 6 patients with tunnel SAS the reduction was less satisfactory. AR was absent or mild in most patients postoperatively. When the gradient was reduced to less than 80 mm Hg, infective endocarditis did not occur unless there were other residual lesions. These data suggest that it is reasonable to resect discrete SAS in children less than 10 to 12 years old with LV outflow gradients greater than or equal to 30 mm Hg.

Adolescent↗
PubMed1983

Repeat aortic valvotomy in children.

The outcome in 13 children with congenital valvar aortic stenosis who underwent a repeat valvotomy for significant residual obstruction was reviewed. There was no hospital mortality (confidence limits 0% to 32%), while one late death (8%) occurred (confidence limits 1% to 57%) following the repeat procedure. Cardiac catheterization was performed in 10 patients (77%) following the second valvotomy (2 years, 7 months mean follow-up): (1) three children, all infants at initial valvotomy, had a peak systolic ejection gradient less than or equal to 40 mm Hg and only mild, at most, aortic regurgitation after the repeat operation; (2) the other seven had a peak systolic ejection gradient greater than 40 mm Hg or at least moderate aortic regurgitation, of whom two were infants at first valvotomy while the others ranged in age from 1 to 12 years at initial surgery. These results suggest that repeat aortic valvotomy may not significantly improve the hemodynamic status of those who did not require initial valvotomy early in life.

Adolescent↗
PubMed1983

Porcine bioprosthetic valve calcification in bovine left ventricle-aorta shunts: studies of the deposition of vitamin K-dependent proteins.

Calcification of glutaraldehyde-preserved bioprosthetic cardiac valves represents a serious clinical problem. Previous work from this laboratory has established the presence in clinical bioprosthetic valve calcifications of vitamin K-dependent calcium-binding proteins, which contain the calcium-binding amino acid gamma-carboxyglutamic acid; no proteins containing gamma-carboxyglutamic acid are present in nonmineralized valves. The purpose of the present study was to examine a series of bovine circulatory bioprosthetic valve explants for calcification and proteins containing gamma-carboxyglutamic acid. Biochemical analyses of explanted bioprosthetic valves from calves demonstrated proteins with gamma-carboxyglutamic acid accumulating in calcified valves during both the onset and progression of valve calcification; calcium levels in the explanted calf bioprostheses were in the same range as those noted in clinical material. Accumulation of calcium and protein with gamma-carboxyglutamic acid occurred simultaneously and progressively, beginning 2 months after implantation. Small amounts of osteocalcin, the bone-derived protein containing gamma-carboxyglutamic acid, were present in both human and bovine bioprosthetic valve calcifications at comparable levels. No osteocalcin was detectable in non-mineralized valve tissue. Warfarin anticoagulant therapy did not prevent calcification or accumulation of protein with gamma-carboxyglutamic acid. It is concluded that proteins containing gamma-carboxyglutamic acid are involved in both the onset and progression of bioprosthetic valve calcification, and that conventional means of vitamin K antagonism do not alter this association or the course of bioprosthetic valve mineralization.

1-Carboxyglutamic Acid↗
PubMed1982

Pathologic findings in postcardiotomy patients managed with a temporary left ventricular assist pump.

Twenty-one postcardiotomy patients in cardiogenic shock, nonresponsive to pressors and intraaortic balloon, received temporary support with a pneumatically driven left ventricular assist pump, according to a strict National Institutes of Health protocol. Nine patients showed hemodynamic improvement after 91 to 190 hours; at least several of these patients had significant perioperative myocardial necrosis. Three patients remain well 39, 38 and 33 months after resuscitation. Eight of the patients died from hemorrhagic diathesis related to extended cardiopulmonary bypass times before hemodynamic improvement on left ventricular assist pump could be demonstrated. Correlation of myocardial biopsies taken at pump implantation in 15 patients and autopsy findings in nonsurvivors suggest that myocardial dysfunction has a reversible component that is related either to diminished compliance (probably due to edema) or to severe but reversible ischemic myocardial injury, or both. There was no evidence of thrombo- or biomaterials emboli or other pump-related complications.

Adult↗
PubMed1981

Infection in remnant of left ventricular assist device after successful separation from assisted circulation.

There have been two long-term and two short-term survivors among 10 patients in our hospital in whom the left ventricular assist device (LVAD) was implanted for cardiogenic shock after cardiac operations. Two of these four patients developed graft infection in the LVAD remnants left attached to the ascending aorta and left ventricle; one died of sepsis and the other required repeat operations for a chronic draining sinus and hemorrhage from a left ventricular--cutaneous fistula. This experience with infection and demonstration of the feasibility of total removal of both limbs of the LVAD without cardiopulmonary bypass lead us to recommend complete removal of the LVAD conduits in patients weaned from assisted circulation.

Aorta↗
PubMed1980

Successful use of a paracorporeal left ventricular assist device in man.

A paracorporeal left ventricular assist device (LVAD) with a capacity to pump 8 L/min of blood was employed in a clinical trial, and this report details the first survivor. A 60-year-old man could not be separated from the pump oxygenator following coronary artery bypass grafting, and, therefore, an LVAD was employed. Almost the entire left ventricular workload was assumed by the mechanical pump so that the myocardium was allowed to rest and recover. The LVAD support was continued for 105 hours. It provided satisfactory total body perfusion with maintenance of good hemodynamics--without serious deleterious effects on hematologic factors. The patient is alive and active without cardiac symptoms 16 months after his operation. The total experience with 13 LVAD implantations warrants continuation of the clinical trials in selected patients.

Angina Pectoris↗
PubMed1980

Development of a nonthrombogenic collagenous blood-prosthetic interface.

Investigations to develop an implantable assist pump for prolonged circulatory support have been impeded by accumulation of friable thrombus on the prosthetic interface, with subsequent embolization. To circumvent this problem, the textured, fibril surface of a polyurethane pump chamber (mat thickness 430 microns) was inoculated with cultured bovine fetal fibroblasts (labelled with thymidine-14C) prior to animal implantation. The pneumatically actuated device (stroke volume 75 ml), maintained a pulsatile blood flow throughout each study. In 20 calf experiments, extending up to 335 days, 30 X 10(6) fibroblasts (in 50 ml media) derived from a single Holstein fetus were distributed on the urethane surface (360 +/- 50 cells/mm2) by rotation of a sealed device for three hours (12 revolutions/hour). Following connection to the circulation, cell washout was minimal. Resultant biologic linings, examined after animal sacrifice, were densely adherent to the underlying polymer matrix, and varied in thickness from 250 micron-1.5 mm. Microscopically, fibroblasts were identified from the surface to base, accompanied by numerous collagen bundles and abundant ground substance. Amino acid analysis in 10/20 pumps implanted for 31--335 days, revealed 50 +/- 5 Hydroxyproline residues/1000 residues (50% collagen) and scant elastin. Donor fibroblasts were identified by radioautography and karyotyping. Lack of immunologic response in 12 Hereford pump recipients as confirmed by serial fibroblast cytotoxicity assays. In conclusion, an induced collagenous-blood interface permitted prolonged mechanical circulatory support in animals without thromboembolic complications.

Animals↗
PubMed1980

Sequential radionuclide imaging during paracorporeal left ventricular support.

A paracorporeal left ventricular to ascending aorta assist device (LVAD) was utilized in four patients with refractory cardiogenic shock following cardiac surgery. Hemodynamic stabilization was achieved in all four patients, two of whom were subsequently discharged from the hospital and continue to do well one year later. A technique is described for obtaining radionuclide ejection fractions (EFs) during temporary LVAD interruption. The EFs appeared to be predictive of eventual unassisted ventricular function and possibly of patient survival.

Adult↗