P. Diane Galbraith

Cardiac Rehabilitation Attendance and Outcomes in Coronary Artery Disease Patients

Background— Cardiac rehabilitation (CR) is an efficacious yet underused treatment for patients with coronary artery disease. The objective of this study was to determine the association between CR completion and mortality and resource use. Methods and Results— We conducted a prospective cohort study of 5886 subjects (20.8% female; mean age, 60.6 years) who had undergone angiography and were referred for CR in Calgary, AB, Canada, between 1996 and 2009. Outcomes of interest included freedom from emergency room visits, hospitalization, and survival in CR completers versus noncompleters, adjusted for clinical covariates, treatment strategy, and coronary anatomy. Hazard ratios for events for CR completers versus noncompleters were also constructed. A propensity model was used to match completers to noncompleters on baseline characteristics, and each outcome was compared between propensity-matched groups. Of the subjects referred for CR, 2900 (49.3%) completed the program, and an additional 554 subjects started but did not complete CR. CR completion was associated with a lower risk of death, with an adjusted hazard ratio of 0.59 (95% confidence interval, 0.49–0.70). CR completion was also associated with a decreased risk of all-cause hospitalization (adjusted hazard ratio, 0.77; 95% confidence interval, 0.71–0.84) and cardiac hospitalization (adjusted hazard ratio, 0.68; 95% confidence interval, 0.55–0.83) but not with emergency room visits. Propensity-matched analysis demonstrated a persistent association between CR completion and reduced mortality. Conclusions— Among those coronary artery disease patients referred, CR completion is associated with improved survival and decreased hospitalization. There is a need to explore reasons for nonattendance and to test interventions to improve attendance after referral.

Sex Differences in Access to Coronary Revascularization after Cardiac Catheterization: Importance of Detailed Clinical Data

Context Women are less likely to be offered therapeutic cardiac procedures than men; however, the reasongender bias or clinical factorsis unknown. Contribution This study of coronary revascularization procedures during the year after catheterization compared men and women with the same extent of coronary artery disease and ejection fraction. The rate of coronary revascularization was the same in men and women. Implications The sex differences in cardiac procedure rates after catheterization appear to reflect appropriate decisions rather than gender bias. However, sex-based differences in catheterization rates remain unexplained. The Editors Reports of sex differences in the likelihood of undergoing cardiac procedures have led to suggestions of gender bias in cardiac care decision making (1-14). Other proposed explanations for the variation in use of cardiac procedures between sexes include differing patient preferences or differing clinical characteristics (for example, smaller coronary vessels in women). Earlier studies did not unanimously find sex differences in cardiac procedure rates; some studies reported equivalent procedure rates for men and women (15-21). The inconsistency across studies may be related to differences in geographic regions and health systems. However, another possible explanation is that many earlier studies evaluated highly selected patient samples that may not reflect processes of care at a population level. Yet another possible explanation is that the published studies on this issue have used various data sources, ranging from highly detailed data from clinical trials to sparsely detailed administrative data. The Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) is a population-based registry that captures detailed clinical information on all adult patients undergoing cardiac catheterization in the province of Alberta, Canada (22). The clinically detailed data generated by APPROACH provide a unique opportunity to study sex differences in access to revascularization after cardiac catheterization without the limitations of a nonrepresentative study sample or insufficiently detailed clinical data. Furthermore, the detailed APPROACH data allow us to assess whether comorbid conditions, extent of coronary disease, and ejection fraction account for or explain any observed sex differences in access to revascularization procedurespercutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) surgery. Using a two-step process, we statistically adjusted crude (unadjusted) rates of cardiac revascularization for men and women in the year following cardiac catheterization. The first (partial) adjustment was based on baseline clinical variables that are routinely available in most databases, including administrative databases. The second (full) adjustment also controlled for extent of coro nary disease and ejection fraction, variables that are uniquely available for a large unselected patient population in APPROACH data. Methods Data Source and Variables The APPROACH database is an inception cohort database that captures clinical information on all patients undergoing cardiac catheterization in Alberta, Canada (22). This province has a population of approximately 2.8 million persons, of whom 10% identify themselves as ethnic minorities (3.5% are of Chinese ethnicity, 2% are of South Asian ethnicity, 1% are black, and 4.5% are aboriginal inhabitants). In 1996, median individual income levels for postal codedefined regions ranged from

Multiple imputation versus data enhancement for dealing with missing data in observational health care outcome analyses

12 000 to

Development and validation of a surname list to define Chinese ethnicity.

37 000 Canadian per year. Sixty-seven percent of Albertans older than 20 years of age have a high school diploma, and 25% have some university-level education. Patients in APPROACH are followed longitudinally for assessment of long-term outcomes after cardiac catheterization. Clinical risk variables recorded at the time of cardiac catheterization are age, sex, diabetes mellitus, cerebrovascular disease, congestive heart failure, chronic pulmonary disease, elevated creatinine level ( 200 mmol/L [ 22.62 g/L]), dialysis status, hyperlipidemia, hypertension, liver or gastrointestinal disease, malignancy or metastatic disease, previous myocardial infarction, previous thrombolytic therapy for myocardial infarction, and peripheral vascular disease. The indication for catheterization is recorded in one of four categories: myocardial infarction within 8 weeks of catheterization, unstable angina, stable angina, or other (for example, arrhythmias without associated angina, or study protocols). The results of cardiac catheterization, including extent of coronary disease and left ventricular ejection fraction, are also recorded. We graded extent of coronary disease according to six categories: normal or near normal, one- to two-vessel disease, two-vessel disease with proximal left anterior descending artery involvement, three-vessel disease, three-vessel disease with proximal left anterior descending artery involvement, or left main disease. A diseased vessel was one that contained a lesion involving more than 50% of the vessel diameter. Left ventricular ejection fraction was graded according to five categories: greater than 50%, 30% to 50%, less than 30%, ventriculography not done (usually because of renal insufficiency or severely depressed cardiac function), and data missing. The APPROACH database accurately captures the occurrence of revascularization procedures in Alberta hospitals and the time to revascularization after cardiac catheterization. We analyzed data from patients undergoing cardiac catheterization from 1995 through 1998, with follow-up data through 1999. The Ethics Review Boards of the University of Calgary and the University of Alberta, Canada, approved the APPROACH study protocol. Statistical Analysis We performed a chi-square test and two-sample t-tests to compare the clinical characteristics of men and women undergoing catheterization. Chi-square tests and log-rank tests were used to compare the unadjusted proportions of men and women having revascularization procedures within 1 year after cardiac catheterization. We then used multivariable Cox proportional-hazards analyses to control revascularization rates for differences in clinical characteristics between men and women undergoing catheterization. For these analyses, we modeled time to 1) any revascularization procedure, 2) PCI, and 3) CABG surgery, with follow-up to 1 year. We initially calculated crude relative risks for procedures for women relative to men and then sequentially modeled two sets of variables. First, for the partially adjusted model, we used a set of clinical variables (age, indication for cardiac catheterization, cardiac history, and the comorbidity variables listed earlier) that would generally be available in most administrative databases (throughout the paper, we call this initial step partial adjustment). Second, for the fully adjusted model, we added two clinical variables, left ventricular ejection fraction and extent of coronary disease, that are uniquely available at a population level in the clinically detailed APPROACH database. The relative risk for women compared with men was the variable of interest for each of the models generated. We calculated and plotted risk-adjusted time-to-revascularization curves for men and women by applying the corrected group prognosis method to the proportional hazards models that generated fully adjusted relative risks (23). By plotting log[log S(t)] versus t and log(t) for all of the above models, we found that the proportional hazards assumption was appropriate for all variables included in the models, except the variable of indication for cardiac catheterization. Therefore, we handled cardiac catheterization as a stratification variable in our models. To assess model performance, we also plotted both martingale and deviance residuals for individual observations and found that none of the observations were widely deviant (that is, almost all deviance residuals were between 1.96 and 1.96). We examined influential observations by measuring the changes in the coefficients after dropping each observation from the data. For sex, the most influential observations changed the coefficient by less than 5% of the standard error. The software product used to perform data analyses was S-PLUS 5 for Linux, version 5.1 (Insightful Corp., Seattle, Washington). Role of the Funding Sources The funding sources had no role in the design, conduct, or reporting of this study. Results A total of 21 816 patients underwent cardiac catheterization in Alberta between 1 January 1995 and 31 December 1998. Of these patients, 15 409 (70.6%) were men and 6407 (29.4%) were women. Within 1 year after catheterization, 8488 of the 15 409 men (55.1%) had undergone a revascularization procedure (PCI or CABG surgery) compared with only 2574 of the 6407 women (40.2%) (P < 0.001). The proportion having undergone PCI at 1 year was 32.2% for men versus 26.1% for women (P < 0.001). The proportion having CABG surgery by 1 year after catheterization was 22.9% for men and only 14.0% for women (P < 0.001). In a proportional hazards analysis, the corresponding crude relative risk (that is, the likelihood) for having any revascularization procedure for women compared with men was 0.67 (95% CI, 0.65 to 0.71). For PCI and CABG surgery, the corresponding relative risks were 0.77 (CI, 0.73 to 0.82) and 0.54 (0.51 to 0.58), respectively. Thus, in relative terms, women were 33% less likely to undergo any revascularization procedure, 23% less likely to undergo PCI, and 46% less likely to undergo CABG surgery than were men. Clinical Characteristics Clinical characteristics of men and women differed (Table 1). Men tended to be younger and had fewer comorbid conditions, including a lower prevalence of chronic lung disease, cerebrovascular disease, hypertension, diabetes mellitus, liver disease, and congestive heart failure. However, men

Economic evaluation of sirolimus-eluting stents

The problem of missing data is frequently encountered in observational studies. We compared approaches to dealing with missing data. Three multiple imputation methods were compared with a method of enhancing a clinical database through merging with administrative data. The clinical database used for comparison contained information collected from 6,065 cardiac care patients in 1995 in the province of Alberta, Canada. The effectiveness of the different strategies was evaluated using measures of discrimination and goodness of fit for the 1995 data. The strategies were further evaluated by examining how well the models predicted outcomes in data collected from patients in 1996. In general, the different methods produced similar results, with one of the multiple imputation methods demonstrating a slight advantage. It is concluded that the choice of missing data strategy should be guided by statistical expertise and data resources.

Accuracy of city postal code coordinates as a proxy for location of residence

Objective:Surnames have the potential to accurately identify ancestral origins as they are passed on from generation to generation. In this study, we developed and validated a Chinese surname list to define Chinese ethnicity. Methods:We conducted a literature review, a panel review, and a telephone survey in a randomly selected sample from a Canadian city in 2003 to develop a Chinese surname list. The list was then validated to data from the Canadian Community Health Survey. Both surveys collected information on self-reported ethnicity and surname. Results:Of the 112,452 people analyzed in the Canadian Community Health Survey, 1.6% were self-reported as Chinese. This was similar to the 1.5% identified by the surname list. Compared with self-reported Chinese ethnicity (reference standard), the surname list had 77.7% sensitivity, 80.5% positive predictive value, 99.7% specificity, and 99.6% negative predictive value. When stratifying by sex and marital status, the positive predictive value was 78.9% for married women and 83.6% for never married women. Conclusions:The Chinese surname list appears to be valid in identifying Chinese ethnicity. The validity may depend on the geographic origins and Chinese dialects in given populations.

Revascularization in patients with heart failure

Background: Sirolimus-eluting stents have recently been shown to reduce the risk of restenosis among patients who undergo percutaneous coronary intervention (PCI). Given that sirolimus-eluting stents cost about 4 times as much as conventional stents, and considering the volume of PCI procedures, the decision to use sirolimus-eluting stents has large economic implications. Methods: We performed an economic evaluation comparing treatment with sirolimus-eluting and conventional stents in patients undergoing PCI and in subgroups based on age and diabetes mellitus status. The probabilities of transition between clinical states and estimates of resource use and health-related quality of life were derived from the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) database. Information on effectiveness was based on a meta-analysis of randomized controlled clinical trials (RCTs) comparing sirolimus-eluting and conventional stents. Results: Cost per quality-adjusted life year (QALY) gained in the baseline analysis was Can

Lower extremity peripheral arterial disease in individuals with coronary artery disease: Prognostic importance, care gaps, and impact of therapy

58 721. Sirolimus-eluting stents were more cost-effective in patients with diabetes and in those over 75 years of age, the costs per QALY gained being

Renal outcomes associated with invasive versus conservative management of acute coronary syndrome: propensity matched cohort study

44 135 and

Population rates of cardiac catheterization and yield of high-risk coronary artery disease

40 129, respectively. The results were sensitive to plausible variations in the cost of stents, the estimate of the effectiveness of sirolimus-eluting stents and the assumption that sirolimus-eluting stents would prevent the need for cardiac catheterizations in the subsequent year when no revascularization procedure was performed to treat restenosis. Interpretation: The use of sirolimus-eluting stents is associated with a cost per QALY that is similar to or higher than that of other accepted medical forms of therapy and is associated with a significant incremental cost. Sirolimus-eluting stents are more economically attractive for patients who are at higher risk of restenosis or at a high risk of death if a second revascularization procedure were to be required.