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Biomedical subjects

R W Frater

Publications and source records attributed to R W Frater.

At least 37 records · Page 2Linked to original sources
PubMed1995

Time-dependent effect of glutaraldehyde on the tendency to calcify of both autografts and xenografts.

To determine mechanisms responsible for the reduced calcification in short-term glutaraldehyde (Glu)-treated autologous pericardial bioprostheses, we studied the time effect of Glu on subsequent calcification and differences in calcification of autograft and xenograft implants in a rat subcutaneous implantation model. In experiment 1, four groups of bovine pericardial pieces (1 cm2) were prepared: (A) fresh bovine pericardium without Glu, (B) with 15-minute Glu, (C) with 60-minute Glu, and (D) with 120-minute Glu. Seven young male Sprague-Dawley rats were used; each received four bovine pericardial pieces from group A, B, C, or D for subcutaneous implantation. Calcium content of the implants (microgram/mg dry weight) 45 days later was 4.8 +/- 2.9, 29.8 +/- 13.6, 106.3 +/- 13.7, and 176.3 +/- 85.5 in groups A, B, C, and D, respectively (p < 0.05 between any two groups). Experiment 2 used 8 young male Sprague-Dawley rats from different mothers. Each received five subcutaneous skin implants. The five skin implants were prepared as follows: (1) fresh self skin, (2) self skin with 30-minute Glu, (3) self skin with 48-hour Glu, (4) fresh skin of others, and (5) skin of others with 48-hour Glu. After 45 days of implantation, the calcium content of the implants was 1.4 +/- 1.1, 57.9 +/- 35.4, 142.7 +/- 61.4, 1.5 +/- 1.1, and 94.9 +/- 24.1 micrograms/mg dry weight in groups 1, 2, 3, 4, and 5, respectively (p < 0.05 for 1 versus 2, 3, or 5; 2 versus 3, 4, or 5; 3 versus 4; and 4 versus 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Continuous normothermic retrograde cardioplegia for valve surgery.

We have studied warm heart surgery, deemed as continuous warm blood cardioplegia and normothermic cardiopulmonary bypass (CPB), as an alternative to the technique of intermittent cold cardioplegia for valvular surgery. Between August 1990 and January 1994, 137 consecutive patients underwent valve repair or replacement using normothermic CPB. Eighty-six of these patients received continuous normothermic retrograde blood cardioplegia via the coronary sinus (CNRC). Fifty-one patients received intermittent cold blood cardioplegia (ICBC). All procedures were performed by the same surgeon (RWMF). The two groups were matched for age, sex, NYHA class, preoperative ejection fraction, diagnosis, procedure and activated clotting time. Warm blood cardioplegia was delivered continuously via the coronary sinus after antegrade arrest (oxygenated blood 1:4 to 1:3, 37 degrees C, 250-300 ml/min, maintaining coronary sinus pressures of 40-60 mmHg. Perioperative myocardial infarction was significantly less prevalent (4.6 vs. 8.0%; p < 0.05) in the warm cardioplegia group. Cardiac output immediately after bypass was significantly higher than before bypass only in the CNRC group (4.1 +/- 0.8 to 5.2 +/- 0.9 L/min; p < 0.01). CNRC patients had significantly higher incidence of spontaneous resumption of sinus rhythm at cross-clamp removal (80 of 86, 93%) compared to the hypothermic patients (14 of 51, 27%, p < 0.001). The time from removal of the aortic cross-clamp to discontinuation of CPB (reperfusion time) was significantly shorter in the warm cardioplegia group (43 +/- 7.4 versus 75 +/- 10.2 min; p < 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Left-to-right ventricular interaction with a noncontracting right ventricle.

UNLABELLED: Left ventricular systole is known to contribute to generation of right ventricular pressure and stroke volume. To study the interactions in a dilated noncontractile right ventricle after cardiopulmonary bypass we created a variable volume, neo-right ventricle by excision and replacement of the right ventricular free wall with a xenograft pericardial patch. We investigated the interactions in eight dogs with neo-right ventricle, instrumented to measure cardiac pressures and cardiac output in control conditions (n = 69) and during partial pulmonary artery occlusion (n = 50). RESULTS: The size of the neo-right ventricle was increased from original right ventricular volume V0 to V1 (V1 = V0 + 54 +/- 23 ml), V2 (V2 = V0 + 124 +/- 85 ml), and V3 (V3 = V0 + 223 +/- 162 ml). Cardiac output increased with increasing left ventricular end-diastolic pressure, indicating that the Frank-Starling mechanism was operating in the left ventricle. However, cardiac output decreased with increasing neo-right ventricular size (p < 0.001) and during pulmonary artery occlusion (p < 0.001). Maximal neo-right ventricular pressure was a linear function of the maximal left ventricular pressure at each neo-right ventricular size and decreased with the increase in neo-right ventricular size (p < 0.001), both in control conditions and during pulmonary artery occlusion (p < 0.004). Stroke work of the neo-right ventricle and left ventricle decreased with increasing neo-right ventricular size (p < 0.002). The relationship between neo-right ventricular stroke work and left ventricular stroke work at different neo-right ventricular sizes was linear both in control conditions and during pulmonary artery occlusion: in control Y = 0.24X (r = 0.968, n = 69); in pulmonary artery occlusion Y = 0.35X (r = 0.986, n = 50). In both conditions the intercept of the linear relationship was not significantly different from zero (p < 0.974 in control; p < 0.614 in pulmonary artery occlusion). The slope was significantly increased in pulmonary artery occlusion (p < 0.001). CONCLUSION: Left ventricular contraction contributes 24% of left ventricular stroke work to the generation of right ventricular stroke work via the septum in the absence of a contracting right ventricle; this increases to 35% in the face of increased pulmonary afterload. This mechanism can maintain adequate global cardiac function in the case of a noncontracting right ventricle while right ventricular volume is kept small and afterload is not increased. The interventricular interaction of the ventricles must be considered when patients with postbypass right ventricular failure are treated.

Animals↗
PubMed1993

Spontaneous host endothelial growth on bioprosthetic valves and its relation to calcification.

We studied host endothelial growth and calcification of bovine pericardial valve prostheses treated with: (A) 0.625% glutaraldehyde + 4% formaldehyde, (B) 99.5% glycerol or (C) 99.5% glycerol + 4% formaldehyde. Twenty-three stentless chordally supported bileaflet pericardial mitral valves with treatments A (n = 6), B (n = 6) or C (n = 11) were implanted in juvenile sheep for 125-273 days. After sacrifice, the anterior cusp from the annulus to papillary muscle of each valve was examined by scanning electron microscopy for the presence of endothelial cells, and the intrinsic calcification of each valve was determined by measuring calcium (micrograms/mg dry weight) from another 1 cm2 piece of grossly normal cusp. Sixty pieces of 1 cm2 pericardium with treatment A, B or C (n = 20 in each group) were implanted in 30 rats for 70 days. Calcium analysis and histology study of the implants were performed. In sheep, within a similar range of implantation periods, the endothelial growth rate of the valves was the highest in group B, 100% (6/6); group C was 45.5% (5/11) and A 16.7% (1/6). There were no significant differences in calcium among groups A, B and C. In rat implants, the calcium of group B was much lower than that of A or C (B = 6.92 +/- 4.46 vs A = 144.52 +/- 27.66 or C = 240.54 +/- 13.47, P < 0.05) although its histology showed more severe degeneration and inflammatory changes. Pericardial mitral valves treated with glycerol show satisfactory biocompatibility with regard to host endothelial growth and prevention of calcification; however, these tissues show evidence of rapid degeneration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Bioprosthetic cardiac valve degeneration: role of inflammatory and immune reactions.

Inflammatory and immune reactions are thought to mediate both calcification and biodegradation of bioprosthetic cardiac valve implants. To investigate the mechanisms of implant degeneration, we evaluated the role of inflammatory and immune reactions and the effects of tissue preservative treatment in three series of experiments. In the first experiment, three kinds of implants, i.e. glutaraldehyde-treated autograft Sprague-Dawley (SD) rat skin, xenograft Swiss-Webster (SW) mouse skin, and saline-treated autograft (control) were subcutaneously implanted in ten weanling SD rats, and retrieved after 70 days. There was no significant difference in the level of calcification in the autograft (113.13 +/- 27.09 micrograms/mg dry weight) and xenograft (78.27 +/- 31.53 micrograms/mg dry weight) (p > 0.05), but both differed significantly from the control specimens (1.55 +/- 0.87 micrograms/mg dry weight). In the second experiment, the immunological response to glutaraldehyde-treated bovine pericardium (glut tBP) and glycerol treated bovine pericardium (glyc tBP) implants were tested in vivo and in vitro. A Gore-Tex implant was used as a control. Sections of these materials were implanted to the abdominal muscle wall of Lewis rats, with each group composed of twelve animals. Lymphocytes and sera from the animals were isolated, and histological examination was performed at two or four weeks post-implantation. Collagen type 1 (calf skin) was used as antigen. Tritiated thymidine incorporation was used to measure lymphocyte response to antigen collagen type 1 (calf skin), and an Enzyme Linked Immunosorbent Assay (ELISA) was used to test antibodies. The results showed that lymphocytes from both the glut tBP and the glyc tBP groups responded to collagen type 1. The ELISA results showed that the glyc tBP group produced more antibodies than did the glut tBP group, with the difference being significant at a level of p < 0.02. Histology revealed that the glyc tBP had greater inflammatory changes and collagen degeneration than did the glut tBP. In the third experiment, sections of glut tBP and glyc tBP were implanted subcutaneously in two groups of ten weanling SD rats, and retrieved after 70 days. The results showed that glut tBP caused more calcification (197.04 +/- 83.56 micrograms/mg dry weight) than did the glyc tBP (6.74 +/- 0.55 microgram/mg dry weight), with the difference being significant at a level of p < 0.05. From these investigations it is concluded that tissue treatment prior to implantation was very important in determining the tendency of tissue to calcify, and that there was no obvious relationship between bioprosthetic calcification and immunogenicity.

Animals↗
PubMed1993

Myocardial protection in diffuse coronary artery disease. Intermittent retrograde cold-blood cardioplegia at systemic normothermia versus intermittent antegrade cold-blood cardioplegia at moderate systemic hypothermia.

In order to determine the comparative merits of antegrade cardioplegia at moderate systemic hypothermia versus retrograde cardioplegia at systemic normothermia, we performed coronary artery bypass grafting using intermittent oxygenated blood cardioplegia in 2 sets of 50 consecutive patients with triple-vessel disease (complete occlusion of 1 coronary artery and greater than 90% narrowing of the other 2, with poor distal runoff). Group 1 had antegrade cardioplegia at moderate systemic hypothermia (28 degrees C). Group 2 had retrograde cardioplegia at systemic normothermia. This resulted in no deaths and in no differences in complication rates. Group 2's postoperative need for inotropic agents or vasodilators was significantly less (epinephrine, p < 0.0009; dopamine, p < 0.002; nitroglycerin, p < 0.001). Elevations of CKMB fraction were significantly more common in Group 1: 46% had CKMB levels greater than 9%, versus 16% of Group 2 patients (p < 0.0001). Intraoperative transesophageal echocardiography was performed in 39 Group-1 patients and in 42 Group-2 patients. Development of a new wall-motion abnormality after bypass was significantly only in Group 1 (p < 0.009, by chi 2 analysis). We conclude that retrograde cardioplegia at normothermia provides myocardial protection that equals or surpasses that of antegrade delivery at moderate systemic hypothermia, while avoiding the possible deleterious side effects of hypothermia.

Adult↗
PubMed1992

Inverted Y incision for accurate tailoring of patches and vessels.

When anastomosing vessels or using a patch to close a defect, it is often difficult to trim the vessel end or patch to size once the anastomosis is underway. We describe an inverted Y technique that is easy, is completely reproducible, and provides for an even, accurate fit. A continuous suture is run from the heel along either side to the widest part of the anastomosis. A straight incision is made from the tip of the patch or toe of the vessel to a point corresponding to the apex of the defect to be filled; from this point, approximately curved cuts are made to the edges of the patch or vessel just beyond the last sutures. The patch is now accurately shaped and the suture lines are completed.

Anastomosis, Surgical↗
PubMed1992

Is use of the intraaortic balloon pump in octogenarians justified?

Increasing numbers of octogenarians are seen in the operating room or critical care unit with circumstances for which intraaortic balloon pump (IABP) assistance is appropriate, but it has been suggested that the complication rate for IABP use in octogenarians is excessive. From 1980 to 1990, 25 octogenarians needed an IABP in our institution, as an adjunct to operation in 20 patients (1 had repair of a ventricular rupture and 19 underwent coronary grafting); 5 patients did not have operation. The indications for IABP use were unstable angina, 12 (48%); cardiogenic shock, 10 (40%); and difficulty weaning off cardiopulmonary bypass, 3 (12%)--these 3 were the only ones who had insertion through a femoral cut-down. No serious insertion difficulties were noticed with the percutaneous route in the other 22 patients. Without operation, 4 of 5 patients died in the hospital (80%), and the 5th died 2 years 8 months after discharge. After operation, there were two hospital deaths (10%) and two late deaths, neither from cardiac causes. A fatal outcome occurred in 6 of 9 patients with cardiogenic shock. Intraaortic balloon pump-related complications were rare, minor, and unrelated to IABP assistance duration, which ranged from 24 to 146 hours (mean, 49.9 hours). No long-term vascular complications resulted. Hospital stay averaged 22.2 days. At follow-up from 9 to 81 months (mean, 51.8 months), of the 16 survivors, 12 (75%) were in New York Heart Association class I/II and 2 each were in classes III and IV.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗