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Biomedical subjects

D C MacGregor

Publications and source records attributed to D C MacGregor.

At least 55 records · Page 3Linked to original sources
PubMed1966

Mitral valve replacement in a 14-month-old child.

In a 14-month-old child with severe congenital mitral insufficiency, the mitral valve was replaced with a Starr-Edwards valve. This resulted in dramatic improvement and the child continues to thrive one year after surgery. The authors conclude that valve replacement should be considered in a child of any age if other methods of valve repair cannot be relied upon to produce a good result.

Female↗
PubMedDate not supplied

Kinetics and quantitation of In-111 labeled platelet deposition on control and heparin-bonded polyurethane angio catheters in a dog model.

The dynamics of platelet deposition on control polyurethane catheters (CPC) and heparin-bonded polyurethane catheters (HBPC) were evaluated with In-111 labeled platelets (In-PLT) using a computerized gamma camera (CGC). Ten nonheparinized dogs (18-25 kg) had both femoral arteries catherized with 10 cm of CPC and HBPC (5 Fr.) 24 hr postinjection of 300-420 microcuries of In-PLT, and imaged for 3 hr with a gamma camera. Regional platelet deposition on three segments of catheters and the puncture site was determined. Catheters were harvested and radioactivity on the catheter segments (proximal: PROX, middle: MID, distal: DIST and puncture site: PS) of both was determined. From the platelet count in blood, and radioactivity in blood and segments of catheters, adjacent artery, and area of artery and catheter, the platelet-density [X10(3) (mean +/- S.D.)] on catheter and artery was calculated and tabulated. Proximal values were cath (CPC), 1289 +/- 1125; artery, 1355 +/- 587; cath (HBPC), 125 +/- 113; artery, 1149 +/- 1620. The middle values were cath (CPC), 1102 +/- 1109; artery, 1512 +/- 625; cath (HBPC), 132 +/- 108; artery, 1011 +/- 942. Distal values were cath (CPC), 780 +/- 584; artery, 132 +/- 108; cath (HBPC), 227 +/- 194; artery, 1457 +/- 1309. The puncture site values were cath (CPC), 106 +/- 382; artery, 1011 +/- 942; cath (HBPC), 164 +/- 135; artery, 1498 +/- 1240. The large standard deviation in retained platelets is due to embolization. The platelet-density and regional counts on catheter segments were lower with HBPC than CPC, as was the rate of platelet-deposition.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMedDate not supplied

A self-expanding bifurcated endovascular graft for abdominal aortic aneurysm repair. An initial study in a canine model.

Approximately 50,000 abdominal aortic aneurysms (AAAs) are surgically repaired annually in the United States. Endovascular grafts (EVGs) combine a stent and a vascular graft offering great potential for reduced morbidity, mortality, and hospital stay because of minimally invasive endoluminal placement through catheters. Because most AAAs extend into one or both iliac arteries, a bifurcated EVG (bEVG) was developed, consisting of a proximal aortic trunk divided into two distinct lumens or sockets to receive two smaller diameter leg (iliac) components. All components were composed of Didcott self-expanding braided wire stents integrally attached to porous spun polycarbonate urethane liners. Successful placement of the bEVGs (trunks 10-12 mm and legs 5-6 mm diameter) by a 10 Fr introducer through the femoral arteries into the infrarenal aorta and external iliac arteries of 9 of 11 dogs was achieved. Subsequently, 11 of 12 bEVGs were successfully placed to exclude a saccular aneurysm exceeding three aortic diameters created by a fascia lata pouch extending from the aorta into the left external iliac artery, of which 7 were patent at 1 to 4 months. These findings establish design feasibility of the bEVG as well as the utility of the canine experimental model.

Animals↗
PubMedDate not supplied

The measurement of myocardial tissue gas tensions by mass spectrometry.

The mass spectrometer is a well established tool for the measurement of the partial pressures of gases in respiratory gas mixtures and in flowing blood. Only recently has mass spectrometry been applied to the measurement of gas tensions in tissue. Both blood and tissue gas tension measurements by mass spectrometry were made possible by the development of a special sampling catheter surrounded at its tip by a gas--but not liquid--permeable membrane. The partial pressure of each gas at the external surface of the membrane determines the flow of that gas across the membrane which, in turn, is measured by the mass spectrometer. The use of a Teflon membrane permits tissue measurements because its low permeability to gases reduces the sampling rate of gas molecules with the result that the depletion of gas molecules in the tissue surrounding the membrane is minimal. Mass spectrometry is the only technique whereby it is possible to measure regional tissue pO2 and pCO2 and other gas tensions simultaneously and continuously. One application of mass spectrometric tissue gas tension measurements is the monitoring of myocardial ischemia through measurements of myocardial tissue pO2 and pCO2. We have reviewed the work of others and ourselves in this field.

Adenosine Triphosphate↗
PubMedDate not supplied

The composite Corethane/Dacron vascular prosthesis. Canine in vivo evaluation of 4 mm diameter grafts with 1 year follow-up.

Polyurethane vascular prostheses offer the potential of superior thromboresistance and reduced anastomotic hyperplasia compared to existing Dacron and ePTFE alternatives, but have suffered from susceptibility to biodegradation, with resulting mechanical failure. To address this problem, the authors have developed and evaluated a composite prosthesis comprised of: 1) an inner blood interfacing elastomeric porous membrane made from Corethane, a proprietary Shore 80A polyurethane like material substantially devoid of ether/ester linkages, with superior biostability over conventional polyether urethanes, spun into a nonwoven structure with fiber diameters 10-15 microns and pore sizes 30-60 microns filled with gelatin +/- heparin; and 2) an outer soft, tissue interfacing, warp knitted Dacron mesh bonded to the inner layer to assure long-term dimensional stability. Twenty 4 mm ID x 5 cm L composite prostheses, half with heparinized gelatin (the remainder nonheparinized) were implanted as femoral interposition grafts in 10 dogs. Four of the 10 nonheparinized grafts occluded. All 10 with heparin remained widely patent, with two explanted at 6 months showing vascularized connective tissue growth through the graft, in contrast to the giant cell inflammatory response to the Dacron mesh, with a substantially endothelialized neointima and no Corethane biodegradation. Of the 10 patent grafts at 1 year follow-up, none showed aneurysm formation. This vascular prosthesis provides compliance superior to ePTFE and Dacron alternatives, with excellent suture retention and good kink resistance, while combining the superior thromboresistance and tissue ingrowth properties of polyurethanes with the proven biostability of Dacron.

Animals↗
PubMedDate not supplied

The dynamics of platelet thrombus formation rate, thrombus retention time, and rate of embolization on a control and heparin bonded polyurethane angio-catheter.

The dynamics of platelet deposition and embolization from control and heparin bonded polyurethane catheters (CPC and HBPC) was evaluated with In-111 labeled autologous platelets (IN-PLT) and a computerized gamma camera (CGC). Ten non-heparinized dogs (18-25 kg) were catheterized in both femoral arteries with 10 cm of CPC and HBPC (5 Fr., Cordis) 24 hr after injection of 300-420 microCi of In-PLT, and imaged for 3 hr with the computerized gamma camera. The regional platelet deposition curves (RPDC) indicated multiple peaks and valleys; the curves were analyzed for early rate of thrombus formation (upswing), thrombus retention time (full width at half maxima of the RPDC-peak), and rate of embolization (downswing) on both catheters. The four parameters (mean +/- SD) of thrombosis on catheters and integral of the radioactivity time curve for the 3 hr duration of imaging were calculated from normalized counts/sec. The rate of thrombus formation and rate of embolization are higher for the control than HBPC, suggesting that heparin-bonding decreases the early rate of thrombosis and embolization. The thrombus adhesivity and retention time appear shorter for the control catheter, indicating that the control thrombogenic catheter forms multiple thrombi and emboli than HBPC. The integral appears larger for the control catheter than HBPC. In vivo (dynamic) studies, in vitro studies, and critical analyses of the radioactivity time curve were essential for complete evaluation of thrombogenicity of catheters and other cardiovascular prostheses.

Animals↗