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Biomedical subjects

C McKay

Publications and source records attributed to C McKay.

At least 19 recordsLinked to original sources
PubMed1991

Subtotal cholecystectomy.

Subtotal cholecystectomy has been carried out on 11 patients during a 5-year period, constituting 3.8 per cent of cholecystectomies performed during this time. The indications were severe inflammation/fibrosis in six patients, portal hypertension in three and the Mirizzi syndrome in two patients. There were no deaths and only minor in-hospital morbidity. One patient developed a common bile duct stone 21 months after the operation. None of the remaining patients has to date developed postcholecystectomy sequelae (mean follow-up period 29 (range 1-62) months). Subtotal cholecystectomy is a safe, straightforward and definitive operation in patients for whom standard cholecystectomy could be dangerous, and is a more attractive proposition than cholecystostomy.

Acute Disease↗
PubMed1991

Catheter balloon valvuloplasty of stenotic porcine bioprosthetic valves: Part I: Anatomic considerations.

During the last several years, dilating balloons have been applied in the treatment of stenotic cardiac valves. This interest has recently been extended to stenotic porcine bioprosthetic valves. Part I of this review discusses the pathologic processes responsible for degeneration of porcine prostheses: intrinsic calcification (mineralization), cuspal tears and perforations, and cuspal thrombosis (non-infective). These changes form the basis of applied balloon valvuloplasty techniques.

Bioprosthesis↗
PubMed1991

Catheter balloon valvuloplasty of stenotic porcine bioprosthetic valves: Part II: Mechanisms, complications, and recommendations for clinical use.

During the last several years dilating balloons have been applied in the treatment of stenotic cardiac valves. This interest has been extended to stenotic porcine bioprosthetic valves. Part I of this review discusses the pathologic changes producing stenotic porcine prosthetic valves. Part II of this review describes an in vitro study of porcine prosthetic valve valvuloplasty defining the mechanisms, complications, and clinical applications. Results of this study indicate a limited and cautious role in balloon dilation of stenotic bioprosthetic valves.

Adult↗
PubMed1991

Catheter balloon valvuloplasty of stenotic aortic valves. Part I: Anatomic basis and mechanisms of balloon dilation.

Catheter balloon valvuloplasty of stenotic aortic valves has met with generally poor short- and long-term clinical results. Part of this problem resides with the lack of recognition of various etiologies of aortic stenosis. Part I of this review discusses the various etiologies of aortic stenosis and provides an anatomic basis for successful valve dilation. Results of an in vitro study indicate stenotic aortic valves are dilated by various mechanisms (cracking, stretching) based in part upon the etiology of the aortic valve stenosis.

Adult↗
PubMed1991

Catheter balloon valvuloplasty of stenotic aortic valves--Part II: Balloon valvuloplasty during life subsequent tissue examination.

This review describes 23 patients with aortic valve stenosis who underwent balloon valvuloplasty during life and had subsequent valve tissue examined at the time of aortic valve replacement or at necropsy. Of 23 stenotic aortic valves, 17 were examined within 30 days (early) after balloon dilation. Of these 94% had nonrheumatic (nonfused commissures) etiologies for the aortic stenosis. Of the 6 valves examined after 30 days (late) (restenosis), mechanisms of restenosis involve refusion of split commissures and probable elastic recoil. Clinical prediction of the aortic stenosis etiology prior to balloon valvuloplasty may help predict short- and long-term success of the dilation procedure.

Adult↗
PubMed1990

Anatomic basis for and morphologic results from catheter balloon valvuloplasty of stenotic mitral valves.

This report provides the anatomic basis for catheter balloon valvuloplasty procedures. The morphologic hallmark of mitral stenosis is commissural fusion and the major mechanism of successful balloon valvuloplasty is commissural splitting. Single and double dilating balloons are used to increase the cross-sectional orifice area of stenotic mitral valves. Double balloons appear to improve the luminal diameter and cross-sectional area compared with single balloons. This report also illustrates the anatomic basis for single and double balloon catheter placement and position using the transseptal approach.

Catheterization↗
PubMed1990

Process issues in consultancy.

A piece of short term consultancy work in a school for the Mentally Handicapped is described from the perspective of both the consultants and the consultees with particular reference to the process issues involved. Reasons for the high levels of stress, experienced in the exercise are explored by an examination of the contributory factors within the school and the consultancy process itself. As well as a theoretical discussion questions of practical management are considered.

Adolescent↗
PubMed1990

Circumferential quantitative analysis of planar 201T1 myocardial scintigraphy in the diagnosis of coronary artery disease.

Methodology for the computer analysis of 201T1 myocardial perfusion images has been developed by several laboratories. Substantial evidence of the advantage of this approach over visual inspection alone has been reported. The currently available computer analyses use different algorithms to analyze 201T1 kinetics in the myocardium. The authors evaluated and compared two widely used software programs, Medical Data System (MDS): a mean-count profile, and the Cedars Sinai (CS): a maximal-count profile, of planar 201T1 scintigraphy for their ability to detect coronary artery disease (CAD).

Adult↗
PubMed1987

Aortic ejection fraction: a new hemodynamic parameter and its relationship to aortic insufficiency.

Pulsations of the ascending aorta during fluoroscopy in patients with aortic insufficiency (AI) have been described. The authors present their observations of a similar phenomenon in patients who have AI undergoing scintiangiography. In addition, this paper describes a technique to validate and quantitate this finding. They studied 17 patients with documented AI and 14 subjects of a control group. First-pass studies were acquired in the RAO 15 degrees projection. Regions of interest were placed over the proximal aorta during systole and diastole. An aortic ejection fraction (AF) was determined. The calculated AEF data were correlated with the presence or absence of AI. The mean AEF from the 17 AI patients was 27.1 +/- 7.2%, while the mean for the non-AI group was 12.0 +/- 6.5% with p less than .001. An AEF of 18% separates the two groups with a sensitivity, specificity, and accuracy of 88%, 86%, and 87% respectively. Preliminary data demonstrate a mean reduction in AEF of 12.2 percentage points in 7 AI patients who underwent aortic valve replacement. The AEF may be a useful new parameter to evaluate hemodynamic changes associated with aortic valve replacement in patients with aortic insufficiency.

Adult↗
PubMed1986

The effect of 1,25 dihydroxycholecalciferol on parathyroid hormone secretion by monolayer cultures of bovine parathyroid cells.

Controversy exists over a direct effect of 1,25(OH)2D3 on PTH secretion. To investigate the possibility that the suppressive effect of 1,25(OH)2D3 on PTH secretion may be demonstrable in 1,25(OH)2D3-depleted tissue and/or after prolonged periods of exposure to 1,25(OH)2D3, primary monolayer cultures of bovine parathyroid cells were established in 1:1 DMEM/Ham's F-12 media supplemented with 2% calf serum but not 1,25(OH)2D3. Ionized calcium was maintained at 1.0 mM. Experiments were performed on 4-day-old culture cells. PTH concentration was measured using both a mid-region/carboxyl and an amino-terminal PTH antisera. 1,25(OH)2D3 at a concentration of 0.1 ng/ml suppressed PTH secretion by 32 +/- 7% after 48 hours. High calcium concentration (2.0 mM) suppressed PTH secretion by 37 +/- 10% and this effect was not additive over that of 1,25(OH)2D3. PTH secretion rate recovered fully 48 hours after normalization of the external calcium concentration but not after the removal of 1,25(OH)2D3. It is concluded that 1,25(OH)2D3 directly suppresses PTH secretion by monolayer culture of bovine parathyroid cells.

Animals↗
PubMed1978

Heat and mass transfer of a thermal indicator in pulsatile flow through the cardio-pulmonary system. I. Modeling.

The construction of a physico-mathematical model which describes the mechanism of indicator dispersion in the circulation and which fits the thermal dilution curves (TDC) is presented. Because of its more evident physical meaning, formulation of the problem in terms of heat and mass transfer is preferred to stochastic theory. Hypotheses necessary to simplify the general system of governing equations are clearly defined and discussed. This deductive method leads to a one-dimensional convective heat transfer model in which pulsatility and form of injection appear naturally. Simulations of TDC in constant and pulsatile flow cases are performed on a digital mini-computer which demonstrates the model's ability to represent different experimental or clinical observations. This will facilitate hemodynamic parameter identification from TD techniques and will increase the accuracy of this identification.

Aorta↗
PubMed1978

Heat and mass transfer of a thermal indicator in pulsatile flow through the cardio-pulmonary system. II. Identification of cardiac output.

Hamilton's celebrated formula for cardiac output measurement is simple but its validity is dependent on several methodologic requirements which are not generally fulfilled, particularly in thermal dilution. A quite different method, based on a physico-mathematical model of the indicator dispersion in the circulation, is proposed. It allows direct derivation of cardiac output once the model's parameters have been identified. Combined deconvolution and least squares procedures are used with truncated data for this identification. Numerical tests and application to clinical observations are presented. Both limitations and possibilities of further developments in estimation of pulsatile flow conditions from TD technique are discussed.

Blood Circulation↗