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Biomedical subjects

J V Tu

Publications and source records attributed to J V Tu.

At least 55 records · Page 3Linked to original sources
PubMed1998

The improving outcomes of coronary artery bypass graft surgery in Ontario, 1981 to 1995.

BACKGROUND: There is continuing uncertainty over the relative contribution of outcomes monitoring to changes in surgical outcomes over time. The authors studied temporal trends in the clinical characteristics and short-term outcomes of patients who underwent coronary artery bypass grafting (CABG) in Ontario before and after the implementation, in 1993, of a province-wide program to provide feedback on cardiac surgery outcomes. METHODS: The authors analysed data from hospital discharge abstracts on the clinical characteristics and in-hospital death rates of all 67,784 patients who underwent isolated CABG in Ontario between Apr. 1, 1981, and Mar. 31, 1996. RESULTS: Death rates were relatively stable during the first half of the 1980s, then declined gradually in the second half of the decade; this decline continued into the first half of the 1990s. In the 1990s patients were older than those in the 1980s, and a higher proportion had coexisting diseases. Between 1986/87 and 1995/96 the unadjusted death rate decreased by 52% (5.0% v. 2.4%) (p < 0.001). The annual relative rate of decline was approximately 6% (95% confidence interval 5% to 7%) in the period before the outcomes feedback program was implemented and about 9% (95% confidence interval 7% to 11%) in the period after implementation. INTERPRETATION: Rates of death after CABG have been declining steadily in Ontario since the mid-1980s. Outcomes-based quality improvement interventions may facilitate; but are not a prerequisite for, improvements in the quality of surgical care.

Adult↗
PubMed1998

Determinants of outcome after carotid endarterectomy.

BACKGROUND: The efficacy of carotid endarterectomy for selected patients has been evaluated with randomized controlled clinical trials. The generalizability of these studies to average surgical practice remains an important public health concern. OBJECTIVE: The objective of the study was to determine the predictors of outcome after carotid endarterectomy on a regional basis. PATIENTS AND METHODS: The study was designed as a retrospective cohort study and included all consecutive patients presented for carotid endarterectomy at the 8 University of Toronto-affiliated hospitals in the period from January 1, 1994, to December 31, 1996. The main outcome measure was 30-day postoperative stroke or death rate. RESULTS: During the study interval, 1280 primary carotid endarterectomies were performed. The overall combined stroke and death rate was 6.3% for all patients who underwent endarterectomy (4.0% for patients who were asymptomatic). The significant predictors of poor outcome were the following: presenting symptoms (odds ratio, 1.74; 95% confidence interval [CI], 0.96, 3.12), low surgeon volume (<6 cases per year; odds ratio, 3.98; 95% CI, 1.65, 9.58), and left-sided surgery (odds ratio, 1.72; 95% CI, 1.07, 2.76). CONCLUSION: These data suggest that adoption of the recommendations of the symptomatic carotid endarterectomy trials is appropriate. However, endarterectomy for asymptomatic lesions remains of uncertain benefit on a regional basis and must be individualized to the experience of the specific surgeon. The surgeon volume/outcome relationship that is identified in this study suggests a need for a minimum volume threshold for this procedure.

Adult↗
PubMed1997

Assessing the outcomes of coronary artery bypass graft surgery: how many risk factors are enough? Steering Committee of the Cardiac Care Network of Ontario.

OBJECTIVES: We sought to determine whether more comprehensive risk-adjustment models have a significant impact on hospital risk-adjusted mortality rates after coronary artery bypass graft surgery (CABG) in Ontario, Canada. BACKGROUND: The Working Group Panel on the Collaborative CABG Database Project has categorized 44 clinical variables into 7 core, 13 level 1 and 24 level 2 variables, to reflect their relative importance in determining short-term mortality after CABG. METHODS: Using clinical data for all 5,517 patients undergoing isolated CABG in Ontario in 1993, we developed 12 increasingly comprehensive risk-adjustment models using logistic regression analysis of 6 of the Panel's core variables and 6 of the Panel's level 1 variables. We studied how the risk-adjusted mortality rates of the nine cardiac surgery hospitals in Ontario changed as more variables were included in these models. RESULTS: Incorporating six of the core variables in a risk-adjustment model led to a model with an area under the receiver operating characteristic (ROC) curve of 0.77. The ROC curve area slightly improved to 0.79 with the inclusion of six additional level 1 variables (p = 0.063). Hospital risk-adjusted mortality rates and relative rankings stabilized after adjusting for six core variables. Adding an additional six level 1 variables to a risk-adjustment model had minimal impact on overall results. CONCLUSIONS: A small number of core variables appear to be sufficient for fairly comparing risk-adjusted mortality rates after CABG across hospitals in Ontario. For efficient interprovider comparisons, risk-adjustment models for CABG could be simplified so that only essential variables are included in these models.

Aged↗
PubMed1997

Use of cardiac procedures and outcomes in elderly patients with myocardial infarction in the United States and Canada.

BACKGROUND: Acute myocardial infarction is a leading cause of morbidity and mortality in the United States and Canada. We performed a population-based study to compare the use of cardiac procedures and outcomes after acute myocardial infarction in elderly patients in the two countries. METHODS: We compared the use of invasive cardiac procedures and the mortality rates among 224,258 elderly Medicare beneficiaries in the United States and 9444 elderly patients in Ontario, Canada, each of whom had a new acute myocardial infarction in 1991. RESULTS: The U.S. patients were significantly more likely than the Canadian patients to undergo coronary angiography (34.9 percent vs. 6.7 percent, P< 0.001), percutaneous transluminal coronary angioplasty (11.7 percent vs. 1.5 percent, P<0.001), and coronary-artery bypass surgery (10.6 percent vs. 1.4 percent, P<0.001) during the first 30 days after the index infarction. These differences in the use of cardiac procedures narrowed but persisted through 180 days of follow-up. The 30-day mortality rates were slightly but significantly lower for the U.S. patients than for the Canadian patients (21.4 percent vs. 22.3 percent, P=0.03). However, the one-year mortality rates were virtually identical (34.3 percent in the United States vs. 34.4 percent in Ontario, P= 0.94). CONCLUSIONS: Short-term mortality after an acute myocardial infarction was slightly lower in the United States than in Ontario, but these differences did not persist through one year of follow-up. The strikingly higher rates of use of cardiac procedures in the United States, as compared with Canada, do not appear to result in better long-term survival rates for elderly U.S. patients with acute myocardial infarction.

Aged↗
PubMed1997

Coronary artery bypass graft surgery in Ontario and New York State: which rate is right? Steering Committee of the Cardiac Care Network of Ontario.

BACKGROUND: Previous studies have shown that the rate of coronary artery bypass graft (CABG) surgery is much higher in New York State than in Ontario. OBJECTIVE: To compare the service context and clinical characteristics of patients having CABG surgery in New York and Ontario. DESIGN: Retrospective analysis of data from cardiac surgery registries in New York and Ontario. PATIENTS: All 16,690 patients in New York and 5517 patients in Ontario who had isolated CABG surgery in 1993. MEASUREMENTS: Clinical characteristics of patients having CABG surgery and rates of CABG surgery by coronary anatomy. RESULTS: The overall age-adjusted rate of isolated CABG surgery was 1.79 times (95% CI, 1.74 to 1.85) greater in New York than in Ontario. Patients who had CABG surgery in New York were more likely to be elderly and female and to have recently had myocardial infarction (P < 0.001), whereas patients who had CABG surgery in Ontario were more likely to have had left ventricular dysfunction and severe coronary artery disease (two-vessel disease with proximal left anterior descending disease, three-vessel disease, or left main disease) (P < 0.001). The relative rate of CABG surgery for left main disease was 2.53 times (CI, 2.35 to 2.73) greater in New York than in Ontario but was 8.97 times (CI, 8.01 to 10.06) greater for patients with limited coronary artery disease (one-vessel or two-vessel disease without proximal left anterior descending disease). CONCLUSIONS: The higher rates of CABG surgery in New York are associated with higher rates of CABG surgery among the elderly, women, and patients who recently had myocardial infarction. Potential underservicing in Ontario is suggested by a lower rate of CABG surgery for left main disease; however, the higher rate of CABG surgery in New York is also associated with a strikingly higher rate of surgery in patients with limited coronary disease. Such trade-offs highlight the difficulty of defining an optimal rate of CABG surgery.

Adult↗
PubMed1996

Coronary artery bypass mortality rates in Ontario. A Canadian approach to quality assurance in cardiac surgery. Steering Committee of the Provincial Adult Cardiac Care Network of Ontario.

BACKGROUND: This study was conducted to assess the overall mortality rate and the amount of interhospital variation in risk-adjusted mortality rates after coronary artery bypass graft (CABG) surgery in Ontario, Canada. CABG outcomes data are not publicly disseminated in Ontario. METHODS AND RESULTS: Clinical risk factors and surgical outcomes were collected on 15,608 patients undergoing isolated CABG surgery between April 1, 1991, and March 31, 1994, at the nine hospitals performing adult cardiac surgery in Ontario. The data were analyzed on the basis of a fiscal year. The overall mortality rate was 3.01%, and the risk-adjusted mortality rate declined from 3.17% in 1991 to 2.93% in 1993. In 1991, one of the nine hospitals had a risk-adjusted mortality rate significantly lower than the provincial average. Otherwise, the hospitals all had risk-adjusted mortality rates within the expected range during the time period of the study. All hospitals performed > 300 CABG procedures in 1992 and 1993, and only 2 of 42 cardiac surgeons performed < 50 CABG procedures in 1993. CONCLUSIONS: The in-hospital mortality rate after CABG surgery in Ontario is low, and the amount of interhospital variation in risk-adjusted mortality rates is no greater than that expected by chance alone. These outcomes are probably attributable to regionalization of CABG surgery and a very low prevalence of low-volume cardiac surgeons in Ontario.

Aged↗
PubMed1996

Can clinicians predict ICU length of stay following cardiac surgery?

PURPOSE: To determine whether a group of experienced clinicians can predict intensive care unit (ICU) length of stay (LOS) following cardiac surgery. METHODS: A cohort of 265 adult patients undergoing cardiac surgery at St. Michael's Hospital, Toronto, Ontario, between January 2, 1992, and June 26, 1992, were seen preoperatively by the clinicians participating in the study and ICU length of stay was predicted based on the clinicians' preoperative assessment and/or information recorded in the patient's chart. RESULTS: Five hundred and ten ICU length of stay predictions were obtained from a group of eight experienced clinicians (anaesthetists/intensivists, cardiologists, nurses). The clinicians predicted the exact ICU length of stay (in days) correctly 51.2% of the time and were within +/- 1 day 84.5% of the time. The clinicians correctly predicted short ICU stays (< or = 2 days) for 87.6% of the patients who had short ICU stays but only predicted long ICU stays (> 2 days) in 39.4% of the patients who had long ICU stays. CONCLUSIONS: Experienced clinicians can predict preoperatively with a considerable degree of accuracy patients who will have short ICU lengths of stay following cardiac surgery. However, many patients who had long ICU stays were not correctly identified preoperatively. Unidentified preoperative risk factors or unanticipated intraoperative/postoperative events may be causing these patients to have longer than expected ICU stays.

Adult↗
PubMed1996

Advantages and disadvantages of using artificial neural networks versus logistic regression for predicting medical outcomes.

Artificial neural networks are algorithms that can be used to perform nonlinear statistical modeling and provide a new alternative to logistic regression, the most commonly used method for developing predictive models for dichotomous outcomes in medicine. Neural networks offer a number of advantages, including requiring less formal statistical training, ability to implicitly detect complex nonlinear relationships between dependent and independent variables, ability to detect all possible interactions between predictor variables, and the availability of multiple training algorithms. Disadvantages include its "black box" nature, greater computational burden, proneness to overfitting, and the empirical nature of model development. An overview of the features of neural networks and logistic regression is presented, and the advantages and disadvantages of using this modeling technique are discussed.

Algorithms↗
PubMed1995

Multicenter validation of a risk index for mortality, intensive care unit stay, and overall hospital length of stay after cardiac surgery. Steering Committee of the Provincial Adult Cardiac Care Network of Ontario.

BACKGROUND: A multicenter population-based study was conducted to develop and validate a risk index for mortality, intensive care unit (ICU) length of stay, and postoperative length of stay after cardiac surgery. METHODS AND RESULTS: Data were collected from 13,098 patients undergoing cardiac surgery between April 1, 1991, and March 31, 1993, at all nine adult cardiac surgery institutions in Ontario, Canada. A six-variable risk index (age, sex, left ventricular function, type of surgery, urgency of surgery, and repeat operation) was developed using logistic regression analysis to predict in-hospital mortality, ICU stay in days, and postoperative stay in days after cardiac surgery in a derivation set of 6213 patients who had cardiac surgery during fiscal year 1991 (April 1, 1991, to March 31, 1992). The index predicted mortality, prolonged ICU stay (> or = 6 days), and prolonged postoperative length of stay (> or = 17 days) after cardiac surgery with areas under the receiver-operating characteristic (ROC) curve of 0.75, 0.66, and 0.69, respectively, in an independent validation set of 6885 patients who had cardiac surgery during fiscal year 1992 (April 1, 1992, to March 31, 1993). Increasing risk scores were associated with greater mortality rates and longer ICU and postoperative stays at all nine institutions. CONCLUSIONS: Mortality, ICU length of stay, and postoperative length of stay after cardiac surgery can be predicted using a simple six-variable risk index. The index has potential application as a risk stratification tool for comparing patient outcomes and resource use among different hospitals and surgeons.

Adult↗
PubMed1995

Higher in-hospital mortality in female patients following coronary artery bypass surgery: a population-based study. Provincial Adult Cardiac Care Network of Ontario.

This study examined the relationship between gender and in-hospital mortality using data from patients undergoing coronary artery bypass surgery (CABS) in the province of Ontario. All patients who underwent CABS between April 1, 1991 and March 31, 1992 at the 9 cardiac surgery institutions were included for study (n = 5,175). The unadjusted in-hospital mortality rate was 3.3% and was higher among females (5.3%) than males (2.8%). Using logistic regression analysis to adjust for several predictors of in-hospital mortality the odds ratio estimate (OR) for female sex was 1.55 and was statistically significant (95% confidence interval (CI) 1.09 to 2.20). Women experienced rates of in-hospital mortality that are 1.6 times greater than males following bypass surgery after case-mix adjustment for age, anatomical disease severity, anginal class, and comorbid conditions. Severe unstable angina had the greatest potential contribution to in-hospital mortality (OR = 7.51, 95% CI = 3.71-15.23) and was more prevalent in women, indicating that excess mortality may be due to delayed diagnosis in women.

Adult↗
PubMed1994

A predictive index for length of stay in the intensive care unit following cardiac surgery.

OBJECTIVE: To develop a predictive index for length of stay in the intensive care unit (ICU) following cardiac surgery. DESIGN: Univariate and multivariate logistic regression analysis of a cohort of 1404 patients divided into a derivation set of 713 patients and a validation set of 691 patients. SETTING: St. Michael's Hospital, Toronto, a tertiary care cardiovascular centre. PATIENTS: A consecutive sample of all patients undergoing cardiac surgery between Jan. 1 and Dec. 31, 1990 (derivation set), and Jan. 1 and Dec. 31, 1991 (validation set). MAIN OUTCOME MEASURE: A long ICU stay (more than 2 days). Other outcomes analysed were ICU stays over 4, 7 and 10 days, and death. RESULTS: In the derivation set increasing age, female sex, left ventricular function, type of surgery, and urgency of surgery were found to be independent risk factors for a long ICU stay in a multivariate logistic regression analysis. A predictive index was created by assigning risk scores based on the odds ratios of the significant variables in the logistic regression analysis. The predictive index was found to predict lengths of ICU stay greater than 2, 4, 7 and 10 days, and patient death in the validation set. CONCLUSIONS: Length of ICU stay and death following cardiac surgery can be predicted with a multivariate predictive index. The index has potential application as a means of stratifying cardiac surgical risk as well as in optimizing ICU resource planning when resources are limited.

Age Factors↗
PubMed1993

Use of a neural network as a predictive instrument for length of stay in the intensive care unit following cardiac surgery.

A patient's intensive care unit (ICU) length of stay following cardiac surgery is an important issue in Canada, where cardiovascular intensive care resources are limited and waiting lists for cardiac surgery exist. We trained a neural network with a database of 713 patients and 15 input variables to predict patients who would have a prolonged ICU length of stay, defined as a stay greater than 2 days. In an independent test set of 696 patients, the network was able to stratify patients into three risk groups for prolonged stay (low, intermediate, and high), corresponding to frequencies of prolonged stay of 16.3, 35.3, and 60.8%, respectively. The trained network could potentially be used as a predictive instrument for optimizing the scheduling of cardiac surgery patients in times of limited ICU resources. Neural networks are a new method for developing predictive instruments that offer both advantages and disadvantages when compared to other more widely used statistical techniques.

Aged↗
PubMed1993

Bronchoscopy versus empirical therapy in HIV-infected patients with presumptive Pneumocystis carinii pneumonia. A decision analysis.

The outcomes of alternative strategies for the management of pulmonary complications in patients infected with the human immunodeficiency virus (HIV) and with suspected Pneumocystis carinii pneumonia were compared using a decision analysis model. A decision tree was constructed using baseline probabilities derived from published data and expert opinion. The case scenario analyzed was that of a patient not currently receiving anti-Pneumocystis prophylaxis who presents with moderate pulmonary symptoms and fulfills the Centers for Disease Control (CDC) criteria for presumptive P. carinii pneumonia. Two strategies were compared: (1) early bronchoscopy with appropriate therapy based on the results, and (2) empiric treatment for P. carinii (trimethoprim/sulfamethoxazole or pentamidine, and steroids) with delayed bronchoscopy in those not responding to 5 days of empiric therapy. The expected 1-month survival rate (with and without quality of life adjustment) was found to be essentially the same for the two strategies using the baseline probabilities, and the decision remained a toss-up within the clinically relevant range of published probabilities for P. carinii pneumonia in patients fulfilling the CDC criteria. Because early bronchoscopy does not offer any additional survival benefits and is associated with greater costs and disutility, empiric therapy would appear to be the superior management strategy in this scenario.

AIDS-Related Opportunistic Infections↗