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R J Chisholm

Publications and source records attributed to R J Chisholm.

At least 19 recordsLinked to original sources
PubMed2000

Gallstone prevalence in Christchurch: risk factors and clinical significance.

AIMS: To determine the frequency, risk factors and clinical significance of gallstones in a New Zealand population. METHODS: One thousand names were randomly selected from the Christchurch electoral rolls to recruit controls for a study on the prevalence of gallstones in diabetics. Three hundred and eighteen subjects (169 females, 149 males) were recruited and in this study we analyse this control group for gallstone disease. All subjects completed a questionnaire, provided a fasting blood sample and underwent an ultrasound examination of their gallbladder unless they had previously undergone a cholecystectomy. RESULTS: Overall gallstone disease, defined as previous cholecystectomy or a positive scan for gallstones was seen in 20.75% of the 318 subjects recruited. Gallstone disease was more frequent in females (23.1%) compared to males (18.1%) but this difference was not statistically significant. For both genders there was a significant increase in gallstones with age. On univariate analysis, risk factors for gallstone disease included age, increased body mass index, family history of gallstones and decreased alcohol intake in females. However, only age and family history were significant on multiple logistic regression. There was no difference in the frequency of dyspeptic symptoms or abdominal pain between those with or without gallstones confirmed on scanning. The ratio of cholecystectomy to silent gallstones was higher in females (46.2%) than in males (22.2%). CONCLUSION: Gallstones are prevalent in the New Zealand Community (20.8% overall). Risk factors are increasing age and family history. Gallstones detected on scanning were not associated with an increased incidence of dyspeptic symptoms or abdominal pain.

Age Distribution↗
PubMed2000

Homocysteine, lipoprotein(a), and restenosis after percutaneous transluminal coronary angioplasty: a prospective study.

BACKGROUND: Restenosis complicates 30% to 40% of angioplasty procedures and may be unrelated to traditional coronary risk factors. Homocysteine, lipoprotein(a), and methylenetetrahydrofolate reductase (MTHFR 677T) (a genetic determinant of plasma homocysteine concentrations) are novel risk factors for coronary artery disease. Their roles in restenosis are unclear, and the potential synergism between homocysteine and lipoprotein(a) has not previously been studied. The objective of this study was to determine the relations among homocysteine, lipoprotein (a), MTHFR 677T, and restenosis after percutaneous transluminal coronary angioplasty. METHODS: This prospective study enrolled patients with successful elective percutaneous transluminal coronary angioplasty or stenting of a single, de novo, native coronary lesion. Fasting blood was drawn the morning of the procedure for homocysteine, lipoprotein(a), and MTHFR 677T. Follow-up angiography was performed 6 months after the procedure or earlier if clinically indicated. All cineangiograms were analyzed quantitatively. RESULTS: A total of 144 (92%) of 156 eligible patients underwent follow-up coronary angiography. The overall angiographic restenosis rate (residual stenosis >50%) was 31%. Mean homocysteine concentration was 10.1 +/- 3.7 micromol/L. Plasma homocysteine concentrations were not significantly different in patients with or without angiographic restenosis (9.6 +/- 3.3 vs 10.3 +/- 3.8 micromol/L; P =.31). Mean lipoprotein(a) concentration was 21.2 +/- 20.1 mg/dL. Plasma lipoprotein(a) concentrations were not significantly different in patients with or without restenosis (21.9 +/- 21.8 vs 20.9 +/- 19.5 mg/dL). Homozygosity for MTHFR 677T was present in 6.5% and was not associated with increased restenosis. No interaction between homocysteine and lipoprotein(a) was detected. CONCLUSIONS: Homocysteine, lipoprotein(a), and MTHFR 677T are not associated with restenosis after percutaneous transluminal coronary angioplasty.

Adult↗
PubMed1999

Plasma urokinase antigen and plasminogen activator inhibitor-1 antigen levels predict angiographic coronary restenosis.

BACKGROUND: The fibrinolytic system is intimately involved in several processes that contribute to restenosis, including clot dissolution, cell migration, and tissue remodeling. However, the role of the individual activators (urokinase [uPA] and tissue plasminogen [tPA] activators) and inhibitors (plasminogen activator inhibitor [PAI-1]) of the fibrinolytic system in maintaining patency after coronary artery angioplasty and stenting is unclear. METHODS AND RESULTS: We prospectively studied 159 patients with stable angina who underwent successful elective angioplasty (n=110) or stenting (n=49) of de novo native coronary artery lesions. Plasma samples were drawn at baseline (before angioplasty) and serially after angioplasty (immediately afterward and 6 hours, 24 hours, 3 days, 7 days, 1 month, 3 months, and 6 months afterward). Antigen and activity assays were performed for uPA, tPA, and PAI-1. Follow-up quantitative coronary angiography was performed in 92% of eligible patients. The overall angiographic restenosis rate (diameter stenosis >50%) was 31% (37% in PTCA patients, 17% in stented patients). At all time periods, including baseline, uPA antigen levels were significantly higher and PAI-1 antigen levels were significantly lower in patients with restenosis. Restenosis rates for patients in the upper tertile of baseline uPA antigen levels were 2-fold higher than for those in the lower 2 tertiles (46% versus 24% and 22%, respectively; P<0.004). In a stepwise regression multivariate analysis, obstruction diameter after the procedure and uPA antigen were significant predictors of follow-up diameter stenosis. CONCLUSIONS: Plasma uPA antigen levels and PAI-1 antigen levels identify patients at increased risk for restenosis after percutaneous coronary revascularization.

Aged↗
PubMed1998

Gallbladder volume: comparison of diabetics and controls.

Diabetics are known to have an increased prevalence of gallstones. The aim of this study was to investigate whether diabetics have increased gallbladder volumes that would predispose to stasis, nucleation of cholesterol crystals, and gallstone formation. The gallbladder volume of 271 diabetic subjects and 277 controls was determined by ultrasound using the ellipse formula. Gallbladder volume was also determined by the sum of the cylinders method in 143 cases with a strong correlation (r = 0.89) between the two methods. Using analysis of variance, gallbladder volume was influenced by both diabetic type (NIDDM = 33.68 cm3, IDDM = 26.84 cm3, controls = 29.05 cm3; P = 0.018) and the presence of gallstones (gallstones = 32.04 cm3, no gallstones = 27.58 cm3; P = 0.018). The variation in gallbladder volume between NIDDM, IDDM, and control subjects was influenced by the presence of gallstones (P = 0.024, interaction term from ANOVA). Significant differences (P < 0.001) were only found between NIDDM vs IDDM and NIDDM vs control in the nongallstone group (NIDDM = 34.33 cm3, IDDM = 25.08 cm3, control = 25.17 cm3). Males had significantly larger gallbladder volumes than females: 31.98 cm3 vs 27.74 cm3 (P = 0.023). After the inclusion of BMI, HDL cholesterol, triglyceride, and age in a statistical model with gender and diabetic type in those without gallstones, significant differences were still found between NIDDM and IDDM (P = 0.013) and NIDDM and controls (P = 0.005), demonstrating that NIDDM is an independent predictor for increased gallbladder volume.

Adult↗
PubMed1998

Dissolution of gallstones with simvastatin, an HMG CoA reductase inhibitor.

The aim of this study was to determine whether 12 months of therapy with Simvastatin, an HMG CoA reductase inhibitor, would dissolve gallstones. Twenty-seven subjects entered the study, all had a fasting oral cholecystogram, ultrasound examination, and fasting serum lipids prior to therapy. In addition, 22 subjects had their gallbladder ejection fraction, after CCK, determined by radionucleotide scanning. Eleven subjects had the cholesterol saturation index (CSI) of bile calculated before and at the end of 12 months of therapy. Of the 27 subjects, 26 completed 12 months of treatment with Simvastatin 20 mg daily. There was a significant fall in the total serum cholesterol (27%, P < 0.0001), LDL cholesterol (31%, P < 0.0001), triglyceride (34%, P < 0.0001) but no change in HDL after 12 months of therapy. Simvastatin treatment resulted in a 28% fall in the CSI of bile at the end of therapy (P < 0.01). The concentrations of individual bile acids did not change with therapy, and apart from a slight but significant increase in arachidonate, there were no other significant changes in the fatty acid composition of the biliary phospholipids. After 12 months of Simvastatin therapy there was a small decrease in the gallstone diameter but complete dissolution of gallstones was not achieved in any subjects. In conclusion 12 months of therapy with Simvastatin was effective in lowering the serum lipids and the CSI of bile but was not effective in dissolving gallstones.

Adult↗
PubMed1998

Gallbladder polyps: prospective study.

The aim of this study was to describe the natural history of gallbladder polyps. Thirty-eight subjects who had been previously identified as having gallbladder polyps in an epidemiologic study of gallstone prevalence in 627 diabetic subjects and matched controls were followed longitudinally. Follow-up sonograms were obtained on 33 and 22 of the 38 subjects at 2 and 5 years, respectively. Prevalence for gallbladder polyps in this population was 6.7%, with a marked male predominance (odds ratio 2.3). No statistical difference in prevalence was found between diabetic subjects and nondiabetic controls. Ninety percent of the polyps were less than 10 mm in diameter, with no polyp being larger than 12 mm. During the follow-up period no changes suggestive of malignant transformation were observed. In conclusion, we found that gallbladder polyps were relatively common and that few significant changes occurred over a 5 year period. In asymptomatic subjects in whom gallbladder polyps less than 10 mm in diameter are found incidentally, the likelihood of malignant transformation is low.

Adult↗
PubMed1998

The role of glycoprotein IIb/IIIa platelet inhibition in percutaneous coronary intervention in the stent era.

In autumn 1996, shortly after the platelet glycoprotein (GP) IIb/IIIa inhibitor abciximab was approved for clinical use by the Health Protection Branch of Health Canada, seven interventional cardiologists met in a roundtable forum to review the use of abciximab in percutaneous transluminal coronary angioplasty (PTCA). While a compelling body of data was presented that argued strongly for adjunctive abciximab in conventional balloon angioplasty, the participants found in difficult to extrapolate the findings to contemporary interventional practice dominated by stent implantation. This uncertainty stemmed from the lack of clinical trials of abciximab during the stent era. Concerns were also raised that the unrestricted use of two expensive therapeutic modalities (stent implantation and GP IIb/IIIa inhibition) would place severe strains on catheterization laboratory budgets. The general consensus was that, pending the availability of further data, abciximab should probably be reserved for selected at-risk patients. This article summarized the roundtable discussions to provide cardiologists' perspectives on the use of abciximab in interventional practice. An overview of platelet physiology and the rationale for GP IIb/IIIa receptor inhibition; a summary of the results of recent randomized clinical trials that assessed the efficacy of abciximab in PTCA; an account of how stents became the most prevalent technique used in coronary intervention; a summary of the available data evaluating abciximab in conjunction with stent implantation; and a synopsis of the conference discussions are included.

Abciximab↗
PubMed1997

Radiation safety in the cardiac catheterization laboratory.

Over the years, permissible radiation exposure of operators working with x-ray equipment has become progressively reduced. The number of cardiac catheterizations and related interventional procedures has increased and the procedures have become more prolonged. The patient receives relatively infrequent primary radiation while the operator receives frequent but mainly secondary radiation. The operator uses protective barriers, correct positioning of the patient and careful techniques to reduce radiation exposure. The effects of radiation are cumulative and permanent. They may be stochastic or nonstochastic, and somatic and/or genetic, and onset may be delayed for many years. To minimize exposure of patient and operator, cardiologists need a better understanding of radiation physics and of cardiac x-ray equipment. Technical breakthroughs such as digital imaging, pulse fluoroscopy, reduction of frame rates from 60 or 30 frames/s to 15 frames/s, and progression to the filmless laboratory will substantially reduce radiation. This review discusses current cardiac x-ray equipment, possible future developments, radiation, and techniques for reducing radiation and improving safety in the cardiac catheterization laboratory.

Cardiac Catheterization↗
PubMed1996

Excimer laser angioplasty vs. balloon angioplasty in saphenous vein bypass grafts: quantitative angiographic comparison of matched lesions.

Technologies which ablate or debulk tissue may result in better angiographic outcomes by altering the elastic properties of the vessel wall. Accordingly, the procedural outcomes of 88 vein graft lesions treated by either excimer laser angioplasty with adjunct balloon angioplasty (PELCA + PTCA, n = 44) (Spectranetics CVX-300, 1.4-, 1.7-, or 2.0-MM catheters) or balloon angioplasty alone (PTCA, n = 44) were analyzed by quantitative angiography (Cardiac Measurement System). Lesions were individually matched for vessel position, reference diameter (RD), and minimal luminal diameter (MLD). Matching was deemed adequate as the preprocedure MLD (PELCA + PTCA, 1.14 +/- 0.48 mm; PTCA, 1.20 +/- 0.47 mm) and RD (PELCA + PTCA, 3.23 +/- 0.56 mm; PTCA, 3.25 +/- 0.57 mm) were not significantly different. There were also no significant differences between PELCA + PTCA- and PTCA-treated lesions with respect to patient age, graft age, lesion length, symmetry, and plaque area. Balloon diameter at maximal inflation was 2.77 +/- 0.55 mm (PELCA + PTCA group) and 2.84 +/- 0.59 mm (PTCA group), P = NS. Final MLD postprocedure was 2.17 +/- 0.54 mm and 2.19 +/- 0.55 mm for PELCA + PTCA- and PTCA-treated lesions (P = NS), respectively. Vessel stretch [(balloon diameter - MLD pre)/RD], elastic recoil [(balloon diameter - MLD post)/RD], and acute gain [(MLD post - MLD pre)/RD] were calculated and normalized for vessel size (RD). Vessel stretch (PELCA + PTCA, 0.60 +/- 0.22; PTCA, 0.59 +/- 0.24; P = NS), elastic recoil (PELCA + PTCA, 0.28 +/- 0.18; PTCA, 0.26 +/- 0.16), and acute gain (PELCA + PTCA, 0.34 +/- 0.24; PTCA, 0.31 +/- 0.23; P = NS) were not significantly different between the two treatment groups. In a matched population of successfully treated vein graft lesions, PELCA + PTCA did not reduce elastic recoil or improve immediate angiographic outcome, as compared with PTCA alone.

Adult↗
PubMed1996

Prevalence of gallbladder disease in diabetes mellitus.

A study was undertaken to compare the prevalence of gallstone disease (gallstones observed on ultrasound or history of cholecystectomy) in 308 diabetics and 318 controls. There was a higher prevalence of gallstone disease (GSD) in diabetics (32.7%) compared to controls (20.8%; P < 0.001 chi-squared test). However, when gender was taken into account, the difference was only significant in females (diabetics 41.8% versus controls 23.1%; P < 0.001). Analysis by type of diabetes revealed that subjects with non-insulin-dependent diabetes mellitus (NIDDM) had a higher prevalence of GSD than controls for both genders: males-controls 18.1%, NIDDM 33.3% (P < 0.05), IDDM 15.6% ns; females-controls 23.1%, NIDDM 48.6% (P < 0.001), IDDM 36.3% (P < 0.05). On univariate analysis the following risk factors were associated with gallstones (P < 0.1): increased age, body mass index (BMI), triglycerides, LDL cholesterol, decreased HDL cholesterol, alcohol intake, family history of GSD, and female parity > 3. Using stepwise multiple, logistic regression, the following variables were identified as independently predictive of gallstones for each gender/diabetic combination: Males-NIDDM (N = 54), increased age, and decreased HDL; IDDM (N = 90), age and family history; Females-NIDDM (N = 74), increased age, diabetes, increased BMI, and decreased alcohol; IDDM (N = 91), increased BMI, age, decreased alcohol and family history. The proportion of subjects who underwent cholecystectomy was higher in females (46.7%) compared to males (21.7%; P < 0.01) but there were no differences between diabetics and controls in either sex. In conclusion, there was a higher prevalence of GSD in diabetics compared to controls. However, GSD is multifactorial and only in NIDDM females was diabetes an independent risk factor. The proportion of diabetics and controls with GSD who underwent cholecystectomy was equivalent.

Adolescent↗
PubMed1996

In vivo collagen turnover following experimental balloon angioplasty injury and the role of matrix metalloproteinases.

Extracellular matrix formation is the major component of the restenosis lesion that develops after balloon angioplasty. Although ex vivo studies have shown that the synthesis of collagen is stimulated early after balloon angioplasty, there is a delay in accumulation in the vessel wall. The objectives of this study were to assess collagen turnover and its possible regulation by matrix metalloproteinases (MMPs) in a double-injury iliac artery rabbit model of restenosis. Rabbits were killed at four time points (immediately and at 1, 4, and 12 weeks) after balloon angioplasty. In vivo collagen synthesis and collagen degradation were measured after a 24-hour incubation with [14C]proline. Arterial extracts were also run on gelatin zymograms to determine MMP (gelatinase) activity. Collagen turnover studies were repeated in a group of 1-week postangioplasty rabbits that were treated with daily subcutaneous injections of either a nonspecific MMP inhibitor, GM6001 (100 mg/kg per day), or placebo. Collagen synthesis and degradation showed similar temporal profiles, with significant increases in the balloon-injured iliac arteries compared with control nondilated contralateral iliac arteries immediately after angioplasty and at 1 and 4 weeks. Peak collagen synthesis and degradation occurred at 1 week and were increased (approximately four and three times control values, respectively). Gelatin zymography was consistent with the biochemical data by showing an increase of a 72-kD gelatinase (MMP-2) in the balloon-injured side immediately after the second injury, peaking at 1 week, and still detectable at 4 and 12 weeks (although at lower levels). In balloon-injured arteries, the MMP inhibitor reduced both collagen synthesis and degradation. Overall, at 1 week after balloon angioplasty, GM6001 resulted in a 33% reduction in collagen content in balloon-injured arteries compared with placebo (750 +/- 143 to 500 +/- 78 micrograms hydroxyproline per segment, P < .004), which was associated with a nonsignificant 25% reduction in intimal area. Our data suggest that degradation of newly synthesized collagen is an important mechanism regulating collagen accumulation and that MMPs have an integral role in collagen turnover after balloon angioplasty.

Angioplasty, Balloon↗
PubMed1994

Reuse of balloon catheters for coronary angioplasty: a potential cost-saving strategy?

OBJECTIVES: This study was designed to determine the effectiveness, safety and costs associated with reuse of angioplasty catheters and to compare these results with those of a contemporary center that employed a single-use strategy. BACKGROUND: Coronary angioplasty is an important but expensive procedure. To overcome the financial constraints of the Canadian health care system, reuse of angioplasty catheters is routinely practiced in some institutions. METHODS: In a prospective observational study, data forms were completed after each angioplasty procedure and before patient discharge over a 10-month period. RESULTS: A total of 693 patients underwent coronary angioplasty in the two centers. Clinical and lesion characteristics were similar except for a higher incidence of unstable angina at the reuse center (p < 0.005). The angiographic success rate was identical (88%) at both centers. The reuse center utilized more balloon catheters/lesion (mean +/- SD 2.4 +/- 1.5 vs. 1.2 +/- 0.5, p < 0.00001) and had a higher incidence of initial balloon failure (10.2% vs. 3.3%, p < 0.0001). Significant prolongation of the procedure time (81 +/- 41 vs. 68 +/- 32 min, p < 0.0001) and increased volume of contrast medium (201 +/- 86 vs. 165 +/- 61 ml, p < 0.0001) were seen in the reuse center. A higher rate of adverse clinical events (7.8% vs. 3.8%, p < 0.025) was observed in the reuse center, especially in patients with unstable angina. CONCLUSIONS: The reuse strategy was associated with a higher rate of adverse events, prolonged procedure time and increased use of contrast medium, especially in lesions that were not crossed by the initial balloon and in patients with unstable angina. Whether these differences are related to the reuse strategy or to differences in patient groups cannot be ascertained by this observational study. A multicenter randomized trial is required to further assess the safety and the cost/benefit ratio of this strategy.

Aged↗
PubMed1994

Extracellular matrix remodeling after balloon angioplasty injury in a rabbit model of restenosis.

Remodeling of the vessel wall after balloon angioplasty injury is incompletely understood, and in particular, the role of extracellular matrix synthesis in restenosis has received little attention. The objective of the present study was to determine the sequence of changes in collagen, elastin, and proteoglycan synthesis and content after balloon injury and to relate these changes to growth of the intimal lesions and extent of cell proliferation. In a double-injury non-cholesterol-fed model, right iliac arterial lesions in 43 rabbits were treated with balloon angioplasty, and the rabbits were killed at five time points ranging from immediate to 12 weeks. Vessel wall collagen and elastin content and synthesis were measured after incubation with 14C-proline and separation with a cyanogen bromide extraction procedure. Sulfated glycosaminoglycan synthesis was measured after incubation with [35S]sulfate, papain digestion, and ethanol precipitation. Continuous in vivo infusion of bromodeoxyuridine (96 hours) was used to assess cell proliferation. The intimal area significantly increased from 0.27 +/- 0.08 to 0.73 +/- 0.11 mm2 between 0 and 12 weeks. Intimal and medial cell proliferation were modest and peaked at 1 week (labeling indexes of 4.8% and 3.0%, respectively) and then markedly declined by 2 weeks. Significant increases in collagen, elastin, and proteoglycan synthesis, up to 4 to 10 times above control nondamaged contralateral iliac arteries, were noted at 1, 2, and 4 weeks. These increases in synthesis were accompanied by significant increases in collagen and elastin content (by approximately 35%) that coincided with the temporal increase in cross-sectional area.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1993

Prognostic significance of nonvisualization of the fetal stomach by sonography.

OBJECTIVE: To establish the prognostic significance of nonvisualization of the fetal stomach, we prospectively studied the course and outcome of 31 pregnancies in which a normal fluid-filled fetal stomach could not be seen during sonographic examination after 14 weeks' gestation. SUBJECTS AND METHODS: Between April 1989 and May 1991, 7200 sonographic examinations of fetuses after 14 weeks' gestation were done at our hospital. In 31 pregnancies (0.4% of all scans), a normal fluid-filled fetal stomach could not be seen on one or more sonograms after 14 weeks' gestation (range, 14-40 weeks; mean, 22 weeks). The following data were recorded for each examination: gestational age, visualization of the stomach, other fetal abnormalities, and volume of amniotic fluid. In each pregnancy, the average number of sonograms obtained was three (range, one-five). The fetal stomach was regarded as abnormal if the stomach bubble was absent or remained very small and unchanged for at least 45 min during sonography. RESULTS: The outcome was normal in 16 cases. The 15 abnormal outcomes included spontaneous fetal or neonatal death in five, pregnancy terminations in three, and persistent postnatal disability in seven. In 15 pregnancies (48%) lack of visualization of the fetal stomach was the only significant abnormal sonographic finding, but an abnormal outcome occurred in three. In 12 pregnancies, nonvisualization of the fetal stomach was a transient finding, yet three of those pregnancies resulted in persistent postnatal disability, and one was terminated because of severe maternal preeclampsia. A normal fluid-filled stomach was seen on the next sonogram in 15 cases, but five had an abnormal outcome. Only one of the four pregnancies in which a normal stomach was not seen on any subsequent sonogram had an abnormal outcome. Six of seven pregnancies with oligohydramnios had an abnormal outcome, and all three cases with polyhydramnios had an abnormal outcome. The prevalence of abnormal outcome was 88% when additional sonographic abnormalities were observed, but 20% when no other sonographic abnormality was seen. The overall prevalence of abnormal outcome when the fetal stomach was not visualized was 48%. CONCLUSIONS: Not all fetuses with a nonvisualized stomach after 19 weeks' gestation have a poor outcome. Not all fetuses with a transiently nonvisualized stomach have a normal outcome.

Female↗
PubMed1992

Mitral balloon valvuloplasty in pregnancy: advantages of a unique balloon.

The burden of pregnancy in patients with severe mitral stenosis continues to present a therapeutic challenge. We present two such cases successfully treated with balloon valvuloplasty using the Inoue balloon. The unique features of this balloon may render it the technique of choice for selected pregnant patients with severe mitral stenosis.

Adult↗