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Biomedical subjects

R G Masters

Publications and source records attributed to R G Masters.

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

Are temperatures attained by donor hearts during transport too cold?

Excessive myocardial cooling may have detrimental effects on donor heart integrity. This study assessed the standard technique for donor myocardial preservation using hearts from seven mongrel dogs (mean weight 192.7 gm), which were arrested, excised, and placed in a cooler containing saline and ice. Temperature probes placed in both the left and right ventricular free walls and the septum revealed that, after cardioplegia, temperatures fell to 10.3 degrees, 7.5 degrees, and 7.6 degrees C, respectively. Temperature decreased to below 1 degree C after 75, 75, and 60 minutes for the left ventricle, right ventricle, and septum, respectively, independent of the size of the heart (range = 104 to 322 gm). After 4 hours of cooling, temperature was below 0 degrees C throughout the myocardium. Examination with an electron microscope showed similar serial changes over 4 hours in all hearts, including moderate-to-severe cytoplasmic and nuclear swelling and mitochondrial calcium deposits. Cell membranes remained intact, which suggests that the damage was not irreversible. We conclude that current donor heart preservation techniques may result in unacceptably low myocardial temperatures that cause reversible myocardial injury.

Animals↗
PubMed1988

Extrinsic obstruction of the Medtronic-Hall disk valve in the mitral position.

Three cases of acute extrinsic obstruction of the Medtronic-Hall prosthesis in the mitral position are described. In 2 cases papillary muscle and in 1 case suture overhang caused sticking of the tilting disk against the valve rim. The mechanisms of extrinsic obstruction of the tilting disk valve, its recognition, and its prevention are discussed with a review of the literature.

Adult↗
PubMed1988

Coronary endarterectomy. An adjunct to coronary artery bypass grafting.

There is a wide variation in the reported results of endarterectomy in conjunction with coronary artery bypass grafting. Operative mortality ranges from 0 to 10 per cent, perioperative infarction ranges from 5 to 30 per cent, and patency rates range from 38 to 100 per cent, with 74 to 95 per cent being asymptomatic or improved. This wide discrepancy in clinical outcome occurs for a number of reasons. First, there is nonhomogeneity of patient populations resulting from a lack of standardized patient selection criteria. Second, the operative experience of most published reports spans a decade throughout which major advances in cardiac surgery have occurred. Finally, endarterectomy is a technically challenging procedure with its own learning curve. Differences in technique and expertise almost certainly contribute to the variability of results. Patients with diffuse coronary artery disease pose a challenge to the cardiac surgeon. Endarterectomy entails the risks of increased morbidity and mortality and therefore should be done only if conventional bypass grafting is precluded. However, the risks of these complications must always be weighed against the possible benefits. At the present time carefully selected patients can benefit from this procedure. Unfortunately, until such time as controlled randomized studies are carried out on a prospective basis, statistical support for this procedure will not be available. Given that such a study is questionable from an ethical point of view, clinical decisions for this select group of patients must be done on a case-by-case basis. The best that can currently be done is to carefully follow these patients and scrutinize existing data to ensure optimal clinical management.

Coronary Artery Bypass↗
PubMed1988

Ongoing role of pulmonary embolectomy.

Pulmonary embolism remains a frequent and often fatal disorder. For the majority of patients, anticoagulation with heparin followed by warfarin represents the primary mode of treatment. Thrombolytic therapy is recommended for the patient with massive pulmonary embolism that has produced hypotension. Embolectomy is reserved for the patient with post embolic systemic hypotension who has an absolute contraindication to thrombolysis or who deteriorates despite thrombolytic therapy. Following successful embolectomy the surgeon must treat the complications of the surgery and prevent recurrence. Complications include cerebral infarction, pulmonary infarction and endobronchial hemorrhage, right ventricular failure, local or systemic bleeding and venous stasis. A case of successful pulmonary embolectomy with a complicated postoperative course is presented and the pathophysiology and treatment of the complications are discussed.

Adrenal Gland Diseases↗
PubMed1986

Nosocomial gram-negative parotitis.

Nosocomial parotitis is an uncommon postoperative complication, usually affecting elderly, debilitated, dehydrated patients. The preponderance of gram-positive pathogens has been emphasized. The authors present two cases of gram-negative parotitis and review the literature on this condition. Because the organisms producing nosocomial infection in patients receiving intensive care are commonly gram-negative bacilli, treatment should be based on the findings of Gram's staining of the pus obtained from Stensen's duct, altered when necessary by the final culture results.

Cross Infection↗
PubMed1985

Gallstone ileus in the absence of the gallbladder: case report and review of the literature.

Although small-bowel obstruction due to gallstone ileus is uncommon, it assumes increasing importance with advancing age. The obstructing gallstone enters the bowel through an internal fistula between gallbladder and duodenum. The authors describe the case of a patient who had undergone cholecystectomy and in whom gallstone ileus occurred secondary to a stone that entered the bowel through a choledochoduodenal fistula. Treatment was traditional with removal of the obstructing stone, but the fistula was left undisturbed. The authors believe that further biliary tract symptoms are unlikely. The patient was well 8 weeks after operation and roentgenograms indicated that the internal biliary fistula was patent.

Aged↗
PubMedDate not supplied

A transcutaneous energy and information transfer system for implanted medical devices.

During the last four decades there has been a rapid increase in the development and usage of medical devices. Currently, there are more than 500,000 devices on the market and 25,000 new devices enter the market each year. Many medical devices are now designed to be implantable (pacemakers, defibrillators, circulatory assist devices, artificial hearts, cochlear implants, neuromuscular stimulators, biosensors, etc.). Almost all of the active devices (those that perform work) and many of the passive devices (those that do not perform work) require a source of power. In addition, these devices need to be monitored and controlled, which can be accomplished by utilizing remote communication methods. A transcutaneous energy transfer system combined with a remote communications system has been developed and evaluated in vitro and in vivo (bovine, porcine, and human cadaver experiments). The energy transfer system can deliver up to 60 W with power transfer efficiencies between 60 and 83%. An automatically tuned, resonant frequency tracking method is used to obtain optimum power transfer over a range of operating conditions. The remote communications system can transfer digital data bidirectionally through intact skin at rates up to 9600 baud. The system transmits information by frequency modulating an 890 nm infrared carrier signal. The system has demonstrated satisfactory performance during multicenter evaluation with ventricular assist and total artificial heart devices. Design improvements have been identified, which will be implemented to produce an optimized system for energy transfer to and remote communications with various implantable medical devices.

Animals↗
PubMedDate not supplied

Evolution of an electrohydraulic ventricular assist device through in vivo testing. The EVAD Team.

A totally implantable intrathoracic electrohydraulic ventricular assist device has been developed at the University of Ottawa Heart Institute. In vivo testing has been instrumental in its progressive development. A total of 15 experiments (4 acute, 11 performance) have been performed using male calves (62-117 kg). Data from the acute experiments, human fit trials, fluid dynamic studies, and hydraulic/energy efficiency analyses formed the basis for the development of a compact, single piece ventricular assist device called the Unified System in which the volume displacement chamber, motor, and blood chamber are housed within a compact 600 cc, 740 g unit. The performance experiments indicated that the unified system could support calves for periods up to 96 hr. The mean postoperative cardiac output was 7.1 +/- 0.7 L/ min (range = 4.9-11), mean blood pressure was 99.7 +/- 5.8 mmHg, and mean pulmonary artery pressure was 32.1 +/- 1.2 mmHg. The operative technique for intrathoracic implantation has been developed. The major problems encountered were of respiratory failure, improved by device repositioning in the calf; decreased blood inflow to the device that was improved by cannula redesign; circuit board fracture corrected by design modification; and a power supply problem that was limited to a single unit. The preliminary experiments have helped in the design modifications of the Unified System. The improved version of the system will undergo formal performance, reliability, and chronic in vivo testing before human implantation.

Animals↗
PubMedDate not supplied

In vivo evaluation of an intrathoracic ventricular assist device.

In this series of experiments, the Unified System components of the HeartSaver Ventricular Assist Device (VAD) version 5.0 were isolated from the controller and power supply for independent assessment. Five systems with external controller/power supply via a percutaneous lead configuration were tested in 13 male calves (101.8+/-4.3 kg). Two studies were ended acutely because of improper filling and air embolism, respectively. Duration of support was from 2.2 hours to 30 days (mean, 99+/-62 hours). The 30 day survivor was euthanized electively. Study termination was related to postoperative complications in five calves: two with bleeding/tamponade, one with thromboembolism caused by inadequate anticoagulation, and two with respiratory insufficiency. Other causes of termination were: one caused by main building power failure, two from errors in communication between the device and controller, and two caused by hydraulic fluid loss related to housing defects. From these experiments, an intrathoracic position for the calf has been defined, the procedure for implantation without cardiopulmonary bypass has been developed, refinements to the controller have been made, and inflow and outflow cannulae have been reinforced. Hydraulic fluid losses will be solved by proceeding with use of a titanium housing instead of polyurethane. In conclusion, the development of the HeartSaver VAD is progressing, in part because of these experimental and informative animal studies. Further in vivo evaluation of the final version will be conducted before clinical trials.

Animals↗
PubMedDate not supplied

Hemoptysis: two unusual causes.

Hemoptysis is most commonly due to pulmonary pathology. When cardiac in origin it is usually due to mitral valve disease. The authors present two unusual causes of hemoptysis: cor triatriatum and primary cardiac liposarcoma.

Adult↗
PubMedDate not supplied

Changing factors influencing abdominal aortic aneurysm repair.

A personal series of 354 abdominal aortic aneurysmectomies has been analyzed, consisting of 67 in 1961-1969, 152 in 1970-1975 and 135 in 1976-1980. Mean age has increased to 68.1 years with 81% over 60. Aneurysm size and associated diseases have remained constant. Operative mortality for non-ruptured aneurysms has decreased from 12% to 4.1% to 1.8% and for ruptured aneurysms has been 71%, 45% and 52%. In the non-ruptured group renal, pulmonary and cardiac complications and deaths have been reduced. Early graft complications have been 1 in the last 135 and 10 in the previous 152 operations, associated with 36% aorto-bifemoral and tube repairs in the last 5 years. Pre-operative preparation to minimize associated disease symptoms, sophisticated operative monitoring and fluid replacement and improved surgical techniques combined with intensive post-operative care have evolved to produce better results in elective aneurysm repair.

Aged↗
PubMedDate not supplied

The surgical anastomoses after orthotopic heart transplantation: clinical complications and morphologic observations.

From May 1984 through June 1993, 162 patients have undergone orthotopic heart transplantation at the University of Ottawa Heart Institute. Thirty-three deaths occurred, and postmortem examinations were performed in 29 of these cases. This study evaluated the surgical anastomoses of these patients' hearts, an aspect of orthotopic heart transplantation that has not been well described in the literature. The major findings encountered were two cases of stenosis at the left atrial anastomosis, one case of aortic anastomotic tear, one case of pulmonary artery anastomotic kinking, one case of left atrial suture line mural thrombus and possible coronary embolism, and one case of extramural compression of a coronary artery by an anastomotic suture. Other findings when the suture lines were examined included residual native valve remnants, protruding tissue tags or other tissue remnants, mural thrombi, and protruding free suture ends. These findings are described, illustrated, and discussed in the context of the published literature on the subject.

Adult↗
PubMedDate not supplied

Analysis of deaths after heart transplantation: the University of Ottawa Heart Institute experience.

This study reviews the clinical outcome of the 132 orthotopic heart transplantations performed at our institute from 1984 through 1991 and focuses on the pathology of those patients who died. The study comprised 124 adults (mean age, 45.6 +/- 0.9 years) and eight children. Twenty-six adult and one pediatric deaths occurred. Operative mortality (within 30 days) was 10.6%, with 84.8% of patients surviving to discharge. Actuarial probabilities of survival at 1 and 5 years were 84% +/- 3% and 71% +/- 6%, respectively. Of the 27 deaths, six (22.2%) occurred in the operating room (from hemorrhage, graft failure, and hyperacute rejection); 14 (51.9%) occurred in-hospital after surgery (from sepsis, rejection, cytomegalovirus disease, or myocardial infarct), and seven (25.9%) occurred after discharge (from rejection and/or recurrent coronary artery disease). Two groups of patients were at higher risk: patients in cardiogenic shock requiring pretransplantation mechanical support, with in-hospital mortality of 39.1%; and patients with previous valve replacement who were taking oral anticoagulants, with intraoperative mortality of 50.0%. Pathologic examination revealed occasional instances of unsuspected coronary artery disease in the donor hearts with more than 50% stenoses of the left anterior descending coronary arteries in three of 21 (14.3%) of cases. Complications of the transplantation or related therapeutic procedures were common among those who died. The complications ranged from functionally insignificant anatomic curiosities to life-threatening problems. These complications are tabulated and shown.

Adolescent↗