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Biomedical subjects

G J Wilson

Publications and source records attributed to G J Wilson.

At least 145 records · Page 8Linked to original sources
PubMed1986

Synthetic patch angioplasty for repair of coarctation of the aorta: experience with aneurysm formation.

Patch graft angioplasty is an accepted technique for the repair of some forms of coarctation and for recoarctation. Since 1970, 63 patients at our institution underwent 65 operations for repair of coarctation (ages 3 days to 32 years); in 27 it was the initial operation and 38 needed surgery for recoarctation. Average follow-up was 3.5 years (range 3 months to 14 years). There was one death, 20 patients with persistent hypertension, and eight patients with a persistent arm/leg pressure gradient (14 to 30 mm Hg at rest). Five patients required reoperation, two for recoarctation and three for aneurysm formation. The aneurysms were found on routine chest x-rays 3, 3.7, and 13.5 years after surgery. All aneurysms were repaired with left heart bypass in which a Dacron tube graft was used without complications. Synthetic patch angioplasty to repair coarctation was effective; however, aneurysm formation was a late complication in 5% of our patients. All patients undergoing patch repair should be followed on a yearly basis to allow early detection of aneurysms.

Adolescent↗
PubMed1985

Fatal pulmonary hypertension following renal transplantation.

We present a case of fatal pulmonary hypertension occurring in a child several years following renal transplantation for membranoproliferative glomerulonephritis. Premortem investigations failed to reveal a cause for the pulmonary hypertension. Histological features in the lung at autopsy were consistent with a diagnosis of PVOD. The possible common pathogenesis of these seemingly unrelated disorders is discussed.

Adolescent↗
PubMed1985

The role of cardioplegic solution buffering in myocardial protection. A biochemical and histopathological assessment.

The advantages of buffering cardioplegic solutions to improve adenosine triphosphate preservation and postarrest hemodynamic function have been previously promoted. We evaluated the benefit of histidine buffering (195 mmol/L) in a low sodium (27 mEq/L) cardioplegic solution (Roe's) in a canine model of multidose cardioplegic arrest. Four solutions, two unbuffered (K+ = 10 mEq/L and K+ = 30 mEq/L) and two buffered (K+ = 10 mEq/L and K+ = 30 mEq/L), were tested in four groups of dogs for a 4 1/2 hour arrest period followed by 1 hour of reperfusion. Use of the unbuffered solution resulted in a drop in myocardial adenosine triphosphate from 29 +/- 1 mmol/kg (mean +/- standard error of the mean) (K+ = 30 mEq/L) and 28 +/- 2 mmol/kg (K+ = 10 mEq/L) to 8 +/- 2 mmol/kg and 7 +/- 2 mmol/kg, respectively, during the arrest period. In both buffered groups, adenosine triphosphate remained at preischemic levels during the entire arrest period. Myocardial glycogen followed the same pattern as adenosine triphosphate in the buffered groups. Lactate production was markedly elevated in all groups during ischemia. Postarrest hemodynamic function, as assessed by intraventricular isovolumic developed pressure measurements, was better (p less than 0.05) in the buffered low-potassium group than in the other three groups. The extent of myocardial necrosis, measured by triphenyl tetrazolium staining and confirmed by electron microscopy, was minimal (2% +/- 1% of biventricular mass) in the buffered low-potassium group, significantly greater (7% +/- 2% and 10% +/- 2%) in the unbuffered high-potassium and low-potassium groups, respectively, and highest (35% +/- 9%) in the buffered high-potassium group. These findings indicate that significant buffering capacity (similar to that of blood) in a crystalloid cardioplegic solution can be effective in preserving myocardial adenosine triphosphate stores, improving postarrest contractile function, and minimizing myocardial necrosis, provided the combination of high extracellular potassium and high pH levels is avoided.

Adenosine Triphosphate↗
PubMed1984

Influence of fixative osmolality on the morphometric determination of extracellular space in normal and reperfused ischaemic myocardium.

Morphometric determination of extracellular space in control and post-ischaemic reperfused rabbit myocardium was evaluated using two fixatives differing in their composition and total osmolality. Measurement of control extracellular space in an isotonic fixative (294 mOsm/kg water) was 20.8% and in a hypertonic fixative (1816 mOsm/kg water) was 22.2%. These values were not statistically different. Ischaemic durations of 15, 30, 60 and 90 min, followed by an equivalent period of reperfusion, created significant increases in extracellular space. The size of the extracellular space determined by both fixatives was found to be the same. Total fixative osmolality does not appear to influence morphometric evaluation of the extracellular space in control tissue or in tissue damaged by ischaemia and reperfusion.

Animals↗
PubMed1984

Multidose blood versus crystalloid cardioplegia. Comparison by quantitative assessment of irreversible myocardial injury.

The relative efficacy and safety of blood-based potassium cardioplegic solutions compared to crystalloid arresting solutions has been a major controversy in the field of intraoperative myocardial protection for cardiac operations. In this study multidose potassium (K+ = 30 mEq/L) blood cardioplegia was compared to multidose potassium crystalloid cardioplegia in a dog model in which hearts were arrested for periods of 4 1/2 and 6 hours. The cardioplegic solution was given as an initial bolus of 500 ml and then as 250 ml doses every 30 minutes of arrest. In the 4 1/2 hour arrest group, six animals received blood cardioplegia, six received a low-sodium crystalloid cardioplegia (modified Roe's solution), and 10 received a high sodium crystalloid cardioplegic solution of our own design. In the 6 hour arrest group, four animals received blood cardioplegia, four received the low-sodium solution, and four received the high-sodium solution. Myocardial temperature was precisely controlled at 27 degrees +/- 1 degree C in all groups. The hearts were reperfused for periods of 2 to 4 hours after the arrest periods and then examined morphologically for injury. The extent of myocardial damage was quantified in 5 mm thick transverse sections through the ventricles by using a tetrazolium enzyme-mapping technique. In the crystalloid groups the hearts arrested for 4 1/2 hours were significantly injured. The percentage (+/- SEM) of necrosis was 12.3 % +/- 5.6% in the low-sodium cardioplegic (modified Roe's) group and 9.3% +/- 3.4% in the high-sodium group. In the 6 hour arrest group the hearts were severely injured, with contracture occurring in all cases. The percentage of necrosis was 56.5% +/- 13% in the low-sodium cardioplegic group and 71.3% +/- 12% in the high-sodium group. In striking contrast all hearts protected with blood cardioplegia failed to show any evidence of tissue damage either on tetrazolium staining or on electron microscopic examination. We conclude that blood cardioplegia offers superior protection to the arrested heart at moderate hypothermia compared to crystalloid cardioplegia.

Animals↗
PubMed1983

A novel process for the manufacturing of porous grafts: process description and product evaluation.

A novel process has been developed for the manufacture of porous vascular grafts from solutions or melts of polymers. It allows the manufacture of grafts with controllable porosity, pore size, and mechanical properties. In this process, the polymer melt or polymer solution is extruded through fine orifices; the fibers are then stretched and wound on a rotating mandril. Fiber-fiber bonding takes place, resulting in the formation of stable porous tubes. The effects of the process variables on the physical properties of the resulting graft have been studied and preliminary in vivo evaluation in dogs has demonstrated graft patency with a thin, stable neointima in both small (4 mm) and large (10 mm) caliber configurations.

Animals↗
PubMed1982

Effect of pore size on the peel strength of attachment of fibrous tissue to porous-surfaced implants.

Twenty-four rectangular metal plates were fabricated with surface regions in three different pore size ranges (5-20 microns, 20-50 microns, 50-200 microns). The plates were implanted into the dorsal subcutaneous tissue of 12 adult mongrel dogs for periods of 4, 8, 12, and 16 weeks. After animal sacrifice, the fibrous tissue which adhered to the porous-surfaced regions of each plate was mechanically peeled off to give an indication of the strength of tissue attachment. The tissue was examined by both transmitted light and scanning electron microscopy. At each time period, the tissue that contacted the porous regions was found to be collagenized fibroconnective tissue. The mechanical tests indicated an increasing strength of tissue attachment with increasing implantation time and pore size range. The largest pore size range of approximately 50-200 microns produced a mean peel strength of attachment of 27.5 g/mm at the 16-week period.

Animals↗
PubMed1982

Cardioplegia for severe coronary artery disease: an improved technique using direct coronary artery infusion.

Conventional techniques of cardioplegic solution administration result in regional disparities in the level of myocardial protection in patients with severe coronary artery disease. This report describes a simple adjunct to conventional transaortic administration of cardioplegic solution, in which additional solution is introduced directly through the coronary arteriotomy used for the vein graft anastomosis. The supplemental infusate is delivered through s small-caliber flexible catheter. This technique permits effective perfusion of the coronary vascular bed distal to severely stenotic and occlusive lesions. Using an experimental model of physiologically significant coronary arterial stenosis, we compared the effectiveness of this technique with that of conventional techniques of cardioplegia.

Animals↗
PubMed1982

Intraoperative detection of spinal cord ischemia using somatosensory cortical evoked potentials during thoracic aortic occlusion.

Paraplegia remains a devastating and unpredictable complication of surgical procedures requiring temporary occlusion of the thoracic aorta, interruption of important spinal radicular vessels, or both. Intraoperative monitoring of the physiological integrity of the spinal cord should permit the early detection of spinal cord ischemia, the judicious and timely institution of corrective measures, including bypass or shunting, and the preservation of important intercostal arteries in appropriate circumstances. A model of spinal cord ischemia was created by temporary proximal and distal occlusion of the canine thoracic aorta. Serial measurement of somatosensory cortical evoked potentials (SCEP) generated by peripheral nerve stimulation, reflecting the status of long-tract neural conduction, was used to monitor alterations in spinal cord function during ischemia. Twelve animals subjected to aortic occlusion demonstrated a characteristic time-related deterioration of the SCEP with virtual extinction of the signal at a mean interval (+/- standard error of the mean) of 12.4 +/- 1.5 minutes. Six animals in which reperfusion was established immediately following the loss of the SCEP (Group 1) demonstrated complete recovery without neurological sequelae, as assessed by clinical and histological criteria. In 6 animals (Group 2), the period of aortic occlusion was extended for an additional 15 minutes following loss of the SCEP (27.3 +/- 2.3 minutes); postoperatively, 4 of 6 animals sustained major neurological lesions characterized by spastic paraplegia and histological evidence of spinal cord infarction (Group 1 versus Group 2, p less than 0.05). We conclude that distinctive alterations in the SCEP are indicative of reversible ischemic spinal cord dysfunction. On-line monitoring of spinal cord function using the technique of SCEP provides a rational basis for determining of SCEP provides a rational basis for determining operative strategy during surgical procedures on the thoracic aorta.

Animals↗
PubMed1982

Myocardial pH during regional ischemia: evaluation of a fiber-optic photometric probe.

The relationship between the decrease in intramyocardial extracellular pH and the degree of stenosis of the left anterior descending (LAD) coronary artery was studied in eight dogs pretreated with propranolol. Intramyocardial pH was measured with a miniature glass pH electrode and with a new photometric pH probe that uses fiber-optic filaments to measure the color change of an indicator substance in a small permeable chamber. The LAD was cannulated and perfused from the axillary artery. Cannula flow was measured with an electromagnetic flow probe, and regional myocardial blood flow (RMBF) was measured with radioactive microspheres before and at the end of a period of critical stenosis, 2/3 reduction of flow, or total occlusion of the LAD cannula. In the region of the glass electrode, the mean RMBF (+/-SE) decreased by 16.3 +/- 3.3, 52.7 +/- 7.3, and 84.8 +/- 6.5% during the three levels of stenosis, and the pH correspondingly decreased by 0.05 +/- 0.01, 0.29 +/- 0.10, and 0.94 +/- 0.17 units. In the region of the photometric probe, the RMBF decreased 19.1 +/- 1.3, 47.2 +/- 6.7, and 84.3 +/- 6.0%, and the pH decreased by 0.05 +/- 0.02, 0.14 +/- 0.04, and 0.76 +/- 0.18 units. There was no statistically significant difference between the two types of pH sensor.

Animals↗
PubMed1982

Effect of multidose cardioplegia and cardioplegic solution buffering on myocardial tissue acidosis.

Multidose administration of cardioplegic solution during cardiac operation is intended to maintain both electromechanical arrest of the heart and myocardial hypothermia as well as to remove accumulated metabolites of anaerobic glycolysis. This study was conducted to assess the effect of multidose infusion of three different types of cardioplegic solution on tissue acidosis during global myocardial ischemia. Three groups of five dogs each were placed on cardiopulmonary bypass and the aorta was cross-clamped for 3 hours. The hearts were maintained at a constant temperature (20 degrees C) and cardioplegic solution was infused at an initial dose of 500 ml and five supplementary doses of 250 ml administered every 30 minutes. Group 1 received a crystalloid solution weakly buffered with sodium bicarbonate, Group 2 received a blood-based solution, and Group 3 received a crystalloid solution strongly buffered with histidine (Bretschneider's solution). The buffering capacities of the solutions used in Groups 2 and 3 were 40 and 60 times, respectively, that of the solution used in Group 1. The average myocardial tissue pH at the end of 3 hours of ischemia was 6.54 +/- 0.07 in Group 1, 7.23 +/- 0.05 in Group 2, and 7.19 +/- 0.06 in Group 3 (Group 1 significantly lower than Groups 2 and 3). Multidose infusion of a cardioplegic solution with low buffering capacity was unable to prevent the progressive development of tissue acidosis during 3 hours of ischemia. However, the multidose infusion of either blood-based or crystalloid solutions with high buffering capacity completely prevented any further reduction of tissue pH after the first 30 minutes of ischemia.

Acidosis↗
PubMed1981

Regional and transmural myocardial temperature distribution in cold chemical cardioplegia: significance of critical coronary arterial stenosis.

There is a growing recognition of discrepancies in myocardial temperatures during cold chemical cardioplegia. This study was designed to determine the extent to which coronary arterial stenosis just sufficient to abolish vasodilatory reserve in the working heart, but still compatible with myocardial viability ("critical stenosis"), limits heat transfer from the heart during cardioplegic infusion compared to complete coronary occlusion and no stenosis (control). In nine dogs, temperatures were measured from the subepicardium, midwall, and subendocardium of the left ventricle in the distributions of the circumflex (CCA) and left anterior descending (LAD) coronary arteries plus the aortic root, septum, mediastinum, and ventricular cavities. Cardiopulmonary bypass was instituted with core cooling to 28 degrees C. Three infusions of cold (4 degrees C), radioactive microsphere-labeled, potassium chloride arresting solution were periods of reperfusion. The data (mean +/- SEM) indicate that myocardial cooling was transmurally uniform under all conditions, but was significantly impaired (p less than 0.01) in the CCA region by both critical stenosis (17.4 degrees +/- 1.2 degrees C) and occlusion (23.6 degrees +/- 0.4 degrees C) compared to control (8.3 degrees +/- 0.5 degrees C), because of reduced perfusate flow to regional tissues (4 = 0.62, p less than 0.001). These findings show that coronary artery lesions, including those compatible with myocardial viability, impose a severe constraint on myocardial heat transfer and point to a need for improved cardioplegic technique.

Animals↗
PubMed1980

Intramyocardial pH during elective arrest of the heart: relative effects of hypothermia versus potassium cardioplegia on anaerobic metabolism.

Using an intramyocardial pH needle probe (21 gauge) to monitor myocardial metabolism during ischemia, we determined the effect of potassium cardioplegia at both moderate and deep hypothermia. Five groups of 5 dogs each were placed on cardiopulmonary bypass and the pH probe was inserted approximately 10 mm into the left ventricular free wall. Cardiac ischemia was achieved by cross-clamping the ascending aorta at 37 degrees C (Group 1), 27 degrees C (Group 2), or 17 degrees C (Group 3). In the remaining two groups, aortic cross-clamping was followed by the infusion of 600 to 800 ml of potassium cardioplegic solution adjusted to cardiac temperatures of 27 degrees C (Group 4) or 17 degrees C (Group 5). In each group, myocardial temperature was maintained constant, electrical and mechanical activity observed, and pH recorded until a plateau was reached or for 3 hours. Our results show a progressive and significant decrease in the metabolic rate with reduction in temperature over the 37 degrees to 17 degrees C range. By abolishing contractile activity, potassium cardioplegia markedly reduces the rate of hydrogen ion accumulation at 27 degrees C, but at 17 degrees C the additive effect of cardioplegia is much less pronounced. These observations support the principle of reducing contractile activity to a minimum during elective arrest of the heart but indicate that potassium cardioplegia does little to further reduce the rate of anaerobic metabolism, as shown by the measurement of intramyocardial pH, under conditions of deep hypothermia.

Animals↗
PubMed1980

Computer-assisted reporting system for the follow-up patients with cardiac pacemakers.

The implantation of large numbers of permanent cardiac pacemakers carries with it the responsibility for continual reassessment of all aspects of patient management. Experience with more than 4,000 pacemaker implants and replacements since 1963 has led to the development of a comprehensive computer-assisted data collection, management, and reporting system for the follow-up of patients with cardiac pacemakers. Over a seven-year period, data forms have been developed for the detailed documentation of pre-operative, intraoperative and follow-up information. These were designed in the form of checklists suitable for direct computer entry using mark-sense document readers. Special emphasis has been placed on pre-operative indications, selection of appropriate pacing systems, reliable follow-up methodology, and monitoring the performance of various pulse-generators. This system makes possible the rapid computer production of hospital records and reports to involved physicians and can be used to schedule follow-up assessments as required. The information also can be used for hospital statistics, billing, research, and pacemaker registration at the provincial, state of federal level. Experience has shown that a computer-assisted methodology is the only practical means of providing adequate follow-up for a large group of patients. In addition, direct access to relevant information helps to create an environment in which essential research can be carried out in the face of demanding clinical practice.

Computers↗