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Biomedical subjects

W E Pae

Publications and source records attributed to W E Pae.

At least 55 records · Page 3Linked to original sources
PubMed1989

The mature and immature heart: response to normothermic ischemia.

Low cardiac output after heart surgery occurs more frequently in infants than in adults. This study was designed to determine whether this finding could be explained by a greater susceptibility of the immature heart to ischemia. An isolated working heart model was used to compare myocardial recovery in sets of hearts from six immature (2 weeks, 500 g) and six mature (20 weeks, 2 kg) rabbits after 10, 20, and 30 min of ischemia at 37 degrees C. Mean aortic pressure (MAP), aortic flow (AF), heart rate (HR), left atrial pressure (LAP), and ATP and glycogen levels were measured before and after ischemia. Hemodynamic results are expressed as the percentage recovery of preischemic values. ATP and glycogen are reported as micrograms per gram dry weight. After each period of ischemia, the immature hearts had superior recovery of AF (95 +/- 7.0, 72 +/- 8.8, 70 +/- 7.5 vs 58 +/- 7.1, 34 +/- 15.5, 13 +/- 9.1, P less than 0.05). After 10 min of ischemia, recovery of MAP was not different (97 +/- 1.5 vs 100 +/- 3.5), but after 20 and 30 min of ischemia, the immature hearts had better recovery of MAP (108 +/- 10.8, 98 +/- 5.4 vs 64 +/- 10.8, 48 +/- 6.0, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1989

Cardiovascular evaluation before circulatory arrest for removal of vena caval extension of renal carcinoma.

The use of cardiopulmonary bypass, deep hypothermia and circulatory arrest has decreased the risks of hemorrhage, tumor embolization, incomplete thrombus resection, and warm hepatic and renal ischemia associated with resection of renal cell carcinoma extending into the inferior vena cava above the hepatic veins. Patients about to undergo this operation frequently have significant coronary artery and carotid artery disease, and are at risk for perioperative myocardial infarction and stroke. Preoperative evaluation of the coronary artery and carotid artery circulation by coronary angiography, duplex carotid artery scan and digital subtraction carotid angiography is recommended. Depending upon the severity and location of the cardiovascular disease a sequential or simultaneous operation may be performed. This surgical approach can be used in selected patients to facilitate complete tumor thrombectomy with a low operative risk.

Aged↗
PubMed1989

Diltiazem withdrawal before coronary artery bypass surgery.

The authors studied the effects of withdrawing oral diltiazem therapy on the subsequent course of coronary artery bypass graft surgery. Patients with severe coronary artery disease were divided into three groups using a prospective, controlled, randomized protocol. In group D (diltiazem-continuation) patients, diltiazem was administered 2.1 +/- 0.1 hours (mean +/- SEM) before anesthetic induction (n = 10). Group DW (diltiazem-withdrawal) patients received their final diltiazem dose 17.3 +/- 2.9 hours before anesthesia (n = 10). Group R was a reference group of patients not receiving diltiazem (n = 11; not randomized). Anesthesia was induced and maintained with fentanyl and pancuronium without use of halogenated anesthetics. No clinically important differences were detected in measured hemodynamics or drug requirements. Group D patients did not have a lower systemic vascular resistance (SVR) index (P greater than 0.31) or mean arterial pressure (P greater than 0.08) compared with group DW. Also, no evidence for a diltiazem withdrawal response was found, because group DW did not have either a higher SVR index (P = 0.99) or a higher pulmonary vascular resistance index (P = 0.99) compared with group R, and no severe myocardial ischemia, coronary artery spasm, or postoperative heart block were seen. Plasma diltiazem concentrations decreased significantly during CPB (P less than 0.0001), but showed overlap between groups D and DW. Plasma diltiazem concentration did not correlate significantly with simultaneous SVR. These data show the benign effects of both diltiazem administration and its acute withdrawal before coronary artery bypass surgery with high-dose fentanyl anesthesia.

Administration, Oral↗
PubMed1989

Toward an implantable artificial heart. Experimental and clinical experience at The Pennsylvania State University.

The number of patients who would be candidates for replacement of their failing native heart with an artificial device increases every year. A multidisciplinary group at The Pennsylvania State University is working toward the development of a reliable, totally implantable artificial heart. Initial work resulted in a pneumatic total artificial heart that has performed well in animal implants and has been used clinically in three patients as a temporary bridge to cardiac transplantation. Although pneumatic total artificial hearts have demonstrated utility as temporary mechanical circulatory support devices, attempts at permanent implantation by other groups have been fraught with complications. Because of the suboptimal performance of the pneumatic devices used for permanent implantation, the authors' groups at Penn State is developing n electric motor-driven total artificial heart with encouraging results in calf implants. This artificial heart of the future will use a transcutaneous energy transmission system that will obviate the need for percutaneous lines. Thus, the patient will be provided with as near a normal life-style as possible. At present the technology is at hand to implant an electric blood pump system that should provide a reasonable life-style and function reliably with minimal care. Ongoing cooperative experimental efforts will help to provide the answers necessary to make this system ready for clinical use.

Animals↗
PubMed1988

Heterotopic prosthetic ventricles as a bridge to cardiac transplantation. A multicenter study in 29 patients.

Heterotopic prosthetic ventricles were used to support the circulation in 29 candidates for heart transplantation who were expected to die before procurement of a donor heart. Twenty-one of these patients (average age, 36 years) underwent successful transplantation after 8 hours to 31 days of circulatory support. The other eight patients died because their condition could not be stabilized for transplantation, despite restoration of blood flow. Fourteen patients received biventricular support; 15 received only left ventricular support, with pharmacologic assistance of right heart function. Before transplantation, blood flow from the left prosthetic ventricle averaged 2.8 +/- 0.4 liters per minute per square meter of body-surface area, and from the right prosthesis 2.4 +/- 0.4 liters, as compared with an average flow of 1.6 +/- 0.5 liters per minute per square meter before implantation. Of the 21 patients who received heart transplants, 20 were discharged from the hospital after a median of 31 days. Nineteen patients were alive at 7 to 39 months, and 11 of the first 12 were alive at one year. We conclude that heterotopic placement of prosthetic ventricles as a bridge to transplantation provides an effective method of temporarily supporting cardiac function in critically ill patients without removing the natural heart. The early survival rate after transplantation is similar to that with elective cardiac transplantation.

Adolescent↗
PubMed1988

Staged cardiac transplantation. Total artificial heart or ventricular-assist pump?

Because of donor organ unavailability, staged cardiac transplantation has been performed in eight patients with The Pennsylvania State University pneumatic total artificial heart (two patients) or with the Pierce-Donachy ventricular-assist pump (six patients). Of the six patients who received the ventricular-assist pump, four received cardiac allografts after 3, 11, 21, and 31 days of pump support, respectively. Two patients died before transplantation; the causes of death were non-device-related complications. One additional patient died of Pseudomonas sepsis after staged cardiac transplantation. The remaining three patients are alive and have been followed up for as long as 2 years after staged cardiac transplantation. Of the two patients who were supported with the total artificial heart, one underwent staged cardiac transplantation after 11 days of support. Unfortunately, this patient succumbed to fungal sepsis 17 days later. The remaining patient, who received the total artificial heart after rejection of a transplanted heart, expired 379 days later before a suitable donor organ could be located. These experiences indicate that 1) the ventricular-assist pump and total artificial heart can provide reasonably safe effective circulatory support until a patient's overall physiological status is optimal, until a donor organ can be located for transplantation, or both; 2) there is a need for short-, intermediate-, and long-term support system capabilities; and 3) regardless of the patients' underlying pathology (ischemic versus nonischemic cardiomyopathy), in most instances, the simpler external ventricular-assist pump is capable of satisfactory hemodynamic circulatory assistance.

Acute Kidney Injury↗
PubMed1988

The immature and the mature myocardium. Responses to multidose crystalloid cardioplegia.

This study was designed to determine whether multidose St. Thomas' Hospital cardioplegic solution is as effective for preservation of the immature myocardium during ischemia as it is for the mature myocardium. An isolated working heart model was used. Sets of six hearts from immature (3 to 4 weeks, 500 gm) and mature (24 weeks, 2 kg) rabbits were subjected to 60, 90, or 120 minutes of ischemia. Myocardial protection consisted of infusion of cardioplegic solution every 30 minutes at 4 degrees C in a dose of 10 ml/kg of animal weight and maintenance of hypothermia at 10 degrees C by immersion in a cold saline bath. The percent recovery of preischemic aortic flow was lower in the immature than the mature hearts after 90 minutes (60.3% +/- 7.4% versus 101.8% +/- 4.3%) and after 120 minutes (57.4% +/- 10.6% versus 91.1% +/- 13.6%) of ischemia (results expressed as mean value +/- standard error of the mean, p less than 0.05). There were no differences between the mature and the immature hearts in the recovery of heart rate, left atrial pressure, mean aortic pressure, or glycogen stores. Adenosine triphosphate levels measured at the end of the experiment were not different from control in the immature hearts subjected to 60 or 90 minutes of ischemia, but did decline after 120 minutes of ischemia (18.5 +/- 0.8, 16.9 +/- 1.3, 16.6 +/- 0.6 versus 12.3 +/- 1.8 mumol/gm dry weight, p less than 0.05). Adenosine triphosphate levels in the mature hearts were lower than control in hearts subjected to 60, 90, and 120 minutes of ischemia (18.0 +/- 1.2 versus 13.6 +/- 1.1, 12.8 +/- 0.9, 13.7 +/- 1.5 mumol/gm dry weight, p less than 0.05). Multidose St. Thomas' Hospital cardioplegia does not provide adequate preservation of hemodynamic function in the immature rabbit heart, even though myocardial high-energy stores are well preserved. Additional work is necessary to clarify the mechanism of this finding and to develop appropriate methods for protection of the immature myocardium.

Adenosine Triphosphate↗
PubMed1988

Protection of the immature myocardium. An experimental evaluation of topical cooling, single-dose, and multiple-dose administration of St. Thomas' Hospital cardioplegic solution.

Low cardiac output in infants after cardiac operations continues to be a problem, yet little experimental work has been done to evaluate the various methods of protecting the immature myocardium. In this study, we have used an isolated working heart model to test three methods of myocardial protection in 3- to 4-week-old rabbit hearts: (1) topical cooling, (2) single-dose cardioplegia plus topical cooling, and (3) multiple-dose cardioplegia plus topical cooling. Myocardial temperature was maintained at 10 degrees C during ischemia, and St. Thomas' Hospital solution was used for cardioplegia. Sets of 18 hearts were subjected to 60, 90, or 120 minutes of ischemia, and within each set six hearts were protected by all three methods. After 90 and 120 minutes of ischemia, the percent recovery of aortic flow (expressed as mean +/- standard error of the mean) was lower in hearts protected with multiple-dose cardioplegia plus topical cooling (61.5% +/- 4.8%, 50.7% +/- 14.2%) than in those protected with topical cooling (92.4% +/- 5.7%, 94.3% +/- 12.8%) or single-dose cardioplegia plus topical cooling (86.4% +/- 5.3%, 90.2 +/- 3.6%). However, adenosine triphosphate, creatine phosphate, and glycogen levels were adequately preserved in all groups. Both topical cooling and single-dose cardioplegia provide effective protection for the immature rabbit heart during ischemia, but multiple-dose cardioplegia plus topical cooling results in inadequate preservation of hemodynamic function, despite adequate preservation of myocardial high-energy phosphate stores.

Age Factors↗
PubMed1987

Aortic valve replacement and combined aortic valve replacement and coronary artery bypass grafting: predicting high risk groups.

To determine which groups of patients are at highest risk for operative or late mortality, 259 consecutive patients who underwent operation between 1978 and 1984 were studied; 170 underwent aortic valve replacement and 89 underwent aortic valve replacement combined with coronary artery bypass grafting. Multivariate analysis of risk factors selected emergency operation and patient age older than 70 years as the strongest predictors for operative death. Although patients having aortic valve replacement and coronary artery bypass grafting had a higher operative mortality rate (13.5 versus 3.5%), the combined operation had no independent predictive effect on early or late results. At a mean follow-up time of 48 months after surgery, 72% of the survivors of operation were living, 10% were lost to follow-up and 18% were dead. Seventy-seven percent of long-term survivors were in New York Heart Association functional class I or II. The incidence of thromboembolism, paravalvular leak, bacterial endocarditis and hemorrhage each occurred at a rate of less than 1% per patient-year. The factors associated with late death were preoperative age, male sex, left ventricular end-diastolic pressure, cardiac index and functional class. Despite an increase in operative mortality, patients undergoing emergency operation were not at higher risk of late death. Operative mortality is concentrated among several high risk groups. For patients undergoing elective operation, operative mortality is low, especially if the patient is less than 70 years old. Late results are good for all groups of patients undergoing operation, including those who are at greater risk of dying at operation.

Adult↗
PubMed1987

Long-term results of ventricular assist pumping in postcardiotomy cardiogenic shock.

Short-term survival of patients who require ventricular assist pumping for postcardiotomy cardiogenic shock has been encouraging and has provided enough survivors to allow evaluation of long-term results. We observed nine survivors, 39 to 69 years of age (mean = 54.6) for 10 to 53 months (mean = 31) after their discharge from the hospital. In three patients, the angiographic ejection fraction was normal before the operation, whereas in six patients it was moderately to severely impaired. All nine patients were in New York Heart Association Functional Class IV before operation. After operation, eight of the nine patients were in Functional Class I or II. In the remaining patient, the ejection fraction fell markedly and the postoperative functional class remained unchanged. Two patients were employed full-time and one, part-time. Five patients were retired but active and had no cardiac disability, although two of the five did have residual partial noncardiac disability. The remaining patient, a housewife, continued to have compensated congestive heart failure but was relieved of angina. During the follow-up period, five of the nine patients died suddenly after 12, 18, 25, 30, and 38 months from causes that included pulmonary embolus and probable arrhythmias. Survivors who have had ventricular assist pumping for postcardiotomy cardiogenic shock have a good chance of resuming active lives. The risk of being a "cardiac cripple" is small, as is the risk of significant noncardiac disability.

Adult↗
PubMed1986

Left heart and biventricular bypass.

Various forms of circulatory assist devices are currently under investigation. Clinical use of ventricular bypass devices ranging from roller-pump-driven units to pneumatically powered VADs have been in use for several years. These devices are indicated for patients in cardiogenic shock following cardiac surgery or myocardial infarction when all other forms of conventional therapy have failed. Success, though modest, is encouraging in these patients with a dismal prognosis. An increasing role for the VAD may be found in supporting patients whose condition deteriorates while awaiting cardiac transplantation.

Assisted Circulation↗
PubMed1986

Mechanical support of the circulation followed by cardiac transplantation.

Improvements in both mechanical circulatory support devices and immune therapy promise a wider use of sequential mechanical support as a bridge to orthotopic cardiac transplantation. The intra-aortic balloon pump, the left and right ventricular assist pumps, and the pneumatic artificial heart represent the range of devices capable of keeping a patient alive who is awaiting a donor organ. The major difficulty in using circulatory support devices is infection, which is caused by their required percutaneous tubes. We report here our experiences with mechanical circulatory support devices as a bridge to cardiac transplantation. In a series of 31 consecutive transplant procedures, six patients have required preoperative mechanical circulatory support. The intra-aortic balloon pump was used in two patients for 2 and 14 days, respectively, before transplantation. Both patients are well 10 and 11 months after the transplant procedure. Two patients required the left ventricular assist device for 11 and 21 days and are alive 3 weeks and 8 months, respectively, after transplantation. One patient was supported by the pneumatic artificial heart for 10 days before a donor heart became available but died of septic shock 17 days after transplantation. A second patient received a pneumatic artificial heart 7 days after transplantation when the heart transplant failed. He has been in stable condition for 45 days but is recovering from renal failure. Our early experiences indicate that either partial or total mechanical support as a bridge to transplantation is successful if overwhelming sepsis or renal failure can be avoided.

Adult↗
PubMed1982

Vascular anastomoses in growing vessels: the use of absorbable sutures.

Primary end-to-end infrarenal aortic anastomoses were performed in 36 piglets using two synthetic absorbable suture materials: polydioxanone and coated polyglactin. Animals were killed at 1, 4, and 11 weeks and 6 months following operation. Each aorta was removed, burst-tested to 300 mm Hg, radiographed, and examined histologically. All anastomoses were patent, and no burst-test failures occurred. Stenosis occurred in 14 of 17 animals at 1 and 4 weeks, respectively. One of 5 animals exhibited stenosis at 11 weeks, and none of the 14 animals had stenosis 6 months postoperatively. Histological examination revealed fibrosis replacing areas of disrupted elastica at 6 months in both suture groups. This study suggests that absorbable suture material, in particular polydioxanone, because of its excellent handling characteristics and prolonged tensile strength retention, will be useful for the repair of vascular and cardiac anomalies where growth of the suture line is required.

Absorption↗