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Biomedical subjects

Lisa Kuramoto

Publications and source records attributed to Lisa Kuramoto.

16 recordsLinked to original sources
PubMed2006

Cumulative incidence for wait-list death in relation to length of queue for coronary-artery bypass grafting: a cohort study.

BACKGROUND: In deciding where to undergo coronary-artery bypass grafting, the length of surgical wait lists is often the only information available to cardiologists and their patients. Our objective was to compare the cumulative incidence for death on the wait list according to the length of wait lists at the time of registration for the operation. METHODS: The study cohort included 8966 patients who registered to undergo isolated coronary-artery bypass grafting (82.4% men; 71.9% semi-urgent; 22.4% non-urgent). The patients were categorized according to wait-list clearance time at registration: either "1 month or less" or "more than 1 month". Cumulative incidence for wait-list death was compared between the groups, and the significance of difference was tested by means of regression models. RESULTS: Urgent patients never registered on a wait list with a clearance time of more than 1 month. Semi-urgent patients registered on shorter wait lists more often than non-urgent patients (79.1% vs. 44.7%). In semi-urgent and non-urgent patients, the observed proportion of wait-list deaths by 52 weeks was lower in category "1 month or less" than in category "more than 1 month" (0.8% [49 deaths] vs. 1.6% [39 deaths], P < 0.005). After adjustment, the odds of death before surgery were 64% higher in patients on longer lists, odds ratio [OR] = 1.64 (95% confidence interval [CI] 1.02-2.63). The observed death rate was higher in category "more than 1 month" than in category "1 month or less", 0.79 (95%CI 0.54-1.04) vs. 0.58 (95% CI 0.42-0.74) per 1000 patient-weeks, the adjusted OR = 1.60 (95%CI 1.01-2.53). Longer wait times (log-rank test = 266.4, P < 0.001) and higher death rates contributed to a higher cumulative incidence for death on the wait list with a clearance time of more than 1 month. CONCLUSION: Long wait lists for coronary-artery bypass grafting are associated with increased probability that a patient dies before surgery. Physicians who advise patients where to undergo cardiac revascularization should consider the risk of pre-surgical death that is associated with the length of a surgical wait list.

Aged↗
PubMed2006

The risk of death associated with delayed coronary artery bypass surgery.

BACKGROUND: The detrimental effect of delaying surgical revascularization has been estimated in randomized trials and observational studies. It has been argued that the Kaplan-Meier method used in quantifying the hazard of delayed treatment is not appropriate for summarizing the probability of competing outcomes. Therefore, we sought to improve the estimates of the risk of death associated with delayed surgical treatment of coronary artery disease. METHODS: Population-based prospective study of 8,325 patients registered to undergo first time isolated coronary artery bypass grafting (CABG) in any of the four tertiary hospitals that provide cardiac care to adult residents of British Columbia, Canada. The cumulative incidence of pre-operative death, the cumulative incidence of surgery, and the probability that a patient, who may die or undergo surgery, dies if not operated by certain times over the 52-week period after the decision for CABG were estimated. The risks were quantified separately in two groups: high-severity at presentation were patients with either persistent unstable angina or stable angina and extensive coronary artery disease, and low-severity at presentation were stable symptomatic patients with limited disease. RESULTS: The median waiting time for surgery was 10 weeks (interquartile range [IQR] 15 weeks) in the high-severity group and 21 weeks (IQR 30 weeks) in the low-severity group. One percent of patients died before surgery: 54 in the high-severity and 26 in the low-severity group. For 58 (72.5%) patients, death was related to CVD (acute coronary syndrome, 33; chronic CVD, 16; other CVD, 4; and sudden deaths, 5). The overall death rate from all causes was 0.61 (95% CI 0.48-0.74) per 1,000 patient-weeks, varying from 0.62 (95% CI 0.45-0.78) in the high-severity group to 0.59 (95% CI 0.37-0.82) in the low-severity group. After adjustment for age, sex, and comorbidity, the all-cause death rate in the low-severity group was similar to the high-severity group (OR = 1.02, 95% CI 0.64-1.62). The conditional probability of death was greater in the high-severity group than in the low-severity group both for all-cause mortality (p = 0.002) and cardiovascular deaths (p <0.001). CONCLUSION: The probability of death conditional on not having undergone a required CABG increases with time spent on wait lists.

Adult↗
PubMed2006

Do longer delays for coronary artery bypass surgery contribute to preoperative mortality in less urgent patients?

BACKGROUND: Priority wait lists are common for managing access to cardiac surgery in publicly funded health systems. We evaluated whether longer delays contribute to the probability of death before surgery among patients prioritized into the less urgent category. METHODS: We studied records of 9233 patients registered for isolated coronary artery bypass graft (CABG) in British Columbia, Canada. The primary outcome was death before surgery. We estimated the probability that a patient, who could be removed from the list as a result of surgery, death, or other competing events, dies on or before a certain wait-list week. RESULTS: Despite similar death rates in semiurgent and nonurgent groups, 0.63 (95% confidence interval, 0.46-0.80) versus 0.58 (0.36-0.80) per 1000 patient-weeks, nonurgent patients were remaining on the list longer, which contributed to higher cumulative incidence of all-cause death than in semiurgent group (adjusted odds ratio = 1.66; 1.03-2.68). By 52 weeks on the wait list, 0.9% (0.6-1.1) and 1.3% (0.8-1.8) of patients died in semiurgent and nonurgent groups, respectively (P < 0.01). Similar proportions of deaths related to cardiovascular disease estimated over wait-list time in both groups (P = 0.40) were the result of shorter delays in the semiurgent group despite a higher rate of death resulting from cardiovascular disease (0.50 [0.36-0.65] vs. 0.34 [0.17-0.51] per 1000 patient-weeks). CONCLUSION: Queuing according to urgency of treatment contributed to a higher proportion of CABG candidates dying before surgery from all causes in the nonurgent compared with the semiurgent group despite similar weekly death rates observed in both groups. However, similar probabilities of death resulting from cardiovascular disease observed in both groups over wait-list time were the result of shorter delays in the semiurgent group despite a higher rate of cardiovascular death.

Aged↗
PubMed2006

Does wait-list size at registration influence time to surgery? Analysis of a population-based cardiac surgery registry.

OBJECTIVE: To determine whether the probability of undergoing coronary bypass surgery within a certain time was related to the number of patients on the wait list at registration for the operation in a publicly funded health system. METHODS: A prospective cohort study comparing waiting times among patients registered on wait lists at the hospitals delivering adult cardiac surgery. For each calendar week, the list size, the number of new registrations, and the number of direct admissions immediately after angiography characterized the demand for surgery. RESULTS: The length of delay in undergoing treatment was associated with list size at registration, with shorter times for shorter lists (log-rank test 1,198.3, p<.0001). When the list size at registration required clearance time over 1 week patients had 42 percent lower odds of undergoing surgery compared with lists with clearance time less than 1 week (odds ratio [OR] 0.58 percent, 95 percent, confidence interval [CI] 0.53-0.63), after adjustment for age, sex, comorbidity, period, and hospital. The weekly number of new registrations exceeding weekly service capacity had an independent effect toward longer service delays when the list size at registration required clearance time less than 1 week (OR 0.56 percent, 95 percent CI 0.45-0.71), but not for longer lists. Every time the operation was performed for a patient requiring surgery without registration on wait lists, the odds of surgery for listed patients were reduced by 6 percent (OR 0.94, CI 0.93-0.95). CONCLUSION: For wait-listed patients, time to surgery depends on the list size at registration, the number of new registrations, as well as on the weekly number of patients who move immediately from angiography to coronary bypass surgery without being registered on a wait list. Hospital managers may use these findings to improve resource planning and to reduce uncertainty when providing advice on expected treatment delays.

Aged↗
PubMed2006

Unplanned emergency surgery in relation to length of wait lists at registration.

OBJECTIVE: To compare the cumulative incidence of emergency surgery between two groups of patients classified according to the length of wait lists at the time of their registration for coronary artery bypass grafting (CABG) and to test for significant differences in the risk of emergency surgery resulting from registration on a longer wait list. METHODS: A prospective study of all adult British Columbia residents who registered to undergo isolated CABG. We compared the time-dependent cumulative incidence for undergoing planned surgery through unplanned emergency admission before or during a certain wait-list week between two categories of wait-list size. The list size was a simple count of patients with higher or equal urgency to undergo CABG who were on a wait list at the time of registration of a new patient. RESULTS: Wait lists with one month or less of clearance time were observed in all urgent patients and were more prevalent in semi-urgent than non-urgent patients (79.1% vs 44.7%, respectively). The patients registered on a list with a clearance time of more than one month had a rate of unplanned emergency admission similar to those on a list with a clearance time of one month or less, OR = 1.07 (95% CI, 0.78-1.47) after adjustment for age, sex, comorbidity, calendar period, urgency and week on the list. During fifty-two weeks of the wait-list follow-up, an equal proportion of patients underwent unplanned emergency surgery after registration on lists in both clearance-time categories, OR = 1.03 (95% CI, 0.78-1.37) after adjustment. The number of patients who underwent CABG without having been registered on a wait list in the same hospital exerted no independent effect. CONCLUSIONS: The length of a wait list at registration had no effect on the probability that a semi-urgent or non-urgent patient would undergo CABG through unplanned emergency admission before or during a certain wait-list week.

Adult↗
PubMed2005

Chances of late surgery in relation to length of wait lists.

BACKGROUND: The proportion of patients who undergo surgery within a clinically safe time is an important performance indicator in health systems that use wait lists to manage access to care. However, little is known about chances of on-time surgery according to variations in existing demand. We sought to determine what proportion of patients have had late coronary bypass surgery after registration on wait lists of different size in a network of hospitals with uniform standards for timing of surgery. METHODS: Using records from a population-based registry, we studied wait-list times prospectively collected in a cohort of patients registered on wait lists for coronary artery bypass grafting procedures. We compared the number of weeks from registration to surgery against target access times established for three urgency groups. The chances of undergoing surgery within target time have been evaluated in relation to wait-list size at registration and the number of surgeries performed without registration on a wait list. RESULTS: In 1991-2001, two in three patients were at risk of late surgery when registered on wait lists for isolated coronary bypass procedures in British Columbia, Canada. Although urgent patients had never seen a wait list with clearance time exceeding one week, the odds of on-time surgery were reduced by 25%, odds ratio [OR] = 0.75 (95% confidence interval [CI] 0.65-0.87) for every additional operation performed without registration on a list. When the wait list at registration required a clearance time of over one month, semi-urgent patients had 51% lower odds of on-time surgery as compared to lists with clearance time less than one week, OR = 0.49 (95%CI 0.41-0.60), after adjustment for age, sex, comorbidity, calendar period, hospital and week on the list. In the non-urgent group, the odds were 69% lower, OR = 0.31 (95%CI 0.20-0.47). Every time an operation in the same hospital was performed without registration on a wait list, the odds of on-time surgery for listed patients were reduced by 7%, OR = 0.93 (95%CI 0.91-0.95) in the semi-urgent group, and by 10%, OR = 0.90 (95%CI 0.87-0.94), in the non-urgent group. CONCLUSION: Chances of late surgery increase with the wait-list size for semi-urgent and non-urgent patients needing coronary bypass surgery. The weekly number of patients who move immediately from angiography to the operation without registration on a wait list reduced chances of surgery within target time in all urgency groups of listed patients. When advising patients who will be placed on the wait list about the expected time to treatment, hospital managers should take into account the current list size as well as the weekly number of patients who require CABG immediately after undergoing coronary angiography.

Aged↗
PubMed2005

Classifying health-related quality of life outcomes of total hip arthroplasty.

BACKGROUND: Primary total hip arthroplasty (THA) is an effective treatment for hip osteoarthritis, assessed by whatever distribution-based measures of responsiveness. Yet, the group level evaluation has provided very little evidence contributes to our understanding of the large variation of treatment outcome. The objective is to develop criteria that classify individual treatment health related quality of life (HRQOL) outcome after primary THA, adjusted by preoperative scores. METHODS: We prospectively measured 147 patients' disease specific HRQOL on the date of consultation and 12 months post operation by Western Ontario McMaster Universities Osteoarthritis Index (WOMAC). Regression models were used to determine the "expected" outcome for a certain individual baseline score. The ceiling effect of WOMAC measurement is addressed by implementing a left-censoring method. RESULTS: The classification criteria are chosen to be the lower boundary of the 95% confidence interval (CI) of the estimated median from the regression. The robustness of the classification criteria was demonstrated using the Monte-Carlo simulation. CONCLUSION: The classification criteria are robust and can be applied in general orthopaedic research when the sample size is reasonable large (over 500).

Aged↗
PubMed2005

Policy analysis using patient flow simulations: conceptual framework and study design.

How do we know that innovations in healthcare delivery would work? In this paper, we discuss the idea of applying the methodology of group-randomized intervention studies to evaluation of surgical care policies using data from simulation experiments. We argue that a new interdisciplinary framework, which links health services research, operations research, and computer sciences, is required. Specifically, the methodological rigor of evaluative studies should be applied to the analysis of simulation experiments. In turn, the evaluation of policy initiatives should include the simulation of health-system operations. We introduce the framework and study design to evaluate methods for improving the peri-operative process with the use of patient flow simulations.

Adult↗
PubMed2004

Genotype-phenotype correlations for nervous system tumors in neurofibromatosis 2: a population-based study.

Neurofibromatosis 2 (NF2) is an autosomal dominant disease that is characterized by tumors on the vestibular branch of the VIII cranial nerve, but other types of nervous system tumors usually occur as well. Genotype-phenotype correlations are well documented for overall NF2 disease severity but have not been definitively evaluated for specific types of non-VIII nerve tumors. We evaluated genotype-phenotype correlations for various types of non-VIII nerve tumors in 406 patients from the population-based United Kingdom NF2 registry, using regression models with the additional covariates of current age and type of treatment center (specialty or nonspecialty). The models also permitted consideration of intrafamilial correlation. We found statistically significant genotype-phenotype correlations for intracranial meningiomas, spinal tumors, and peripheral nerve tumors. People with constitutional NF2 missense mutations, splice-site mutations, large deletions, or somatic mosaicism had significantly fewer tumors than did people with constitutional nonsense or frameshift NF2 mutations. In addition, there were significant intrafamilial correlations for intracranial meningiomas and spinal tumors, after adjustment for the type of constitutional NF2 mutation. The type of constitutional NF2 mutation is an important determinant of the number of NF2-associated intracranial meningiomas, spinal tumors, and peripheral nerve tumors.

Age of Onset↗
PubMed2004

Lack of regional selectivity during the progression of Parkinson disease: implications for pathogenesis.

BACKGROUND: Dopamine terminal loss in the putamen of patients with Parkinson disease (PD) shows a regional heterogeneity, reflecting selective vulnerability of degenerating neurons to mechanisms of cell death. HYPOTHESIS: If the same pathogenic mechanisms are responsible for the onset and progression of PD, the regional selectivity of dopamine cell loss will be the same throughout the course of the disorder. OBJECTIVE: To investigate the regional selectivity of dopamine terminal loss during the progression of PD. PARTICIPANTS: We studied 67 patients with PD and 20 healthy subjects using positron emission tomography with [(11)C](+/-)dihydrotetrabenazine (DTBZ). RESULTS: Regional values of DTBZ binding potential (calculated as maximum specific binding [B(max)] divided by the equilibrium dissociation constant K(d)) against disease duration in the putamen of PD patients were best described by a multivariate exponential model with distinct parallel asymptotic values that were significantly (P<.001) different across 4 regions of the putamen. The extent of loss of DTBZ binding potential with disease progression during the clinical stage of PD (early vs late PD) was similar between the anterior (-33%, using early PD as the baseline) and posterior (-29%) putamen. In contrast, the extent of loss of DTBZ binding potential in early PD, which reflects the cumulated loss of DTBZ binding potential from the onset of the disorder (in healthy subjects vs those with early PD), was significantly (P<.001) lower in the posterior (-58%, using healthy subjects as the baseline) than the anterior (-42%) putamen. CONCLUSION: To the extent that DTBZ positron emission tomography provides an accurate estimate of loss of dopamine neurons, our findings suggest that the mechanisms responsible for the progression of PD may not be the same as those responsible for its onset.

Aged↗
PubMed2004

Waiting time in relation to wait-list size at registration: statistical analysis of a waiting-list registry.

OBJECTIVE: To examine the relationship between the length of a waiting list for elective vascular surgery and the delay before undergoing the operation. METHODS: We undertook a prospective cohort study of patients registered on the waiting list for elective vascular surgery at an acute care hospital in Ontario. Regression analysis of wait times to express the admission rate in one group relative to another, with the ratio of rates being a measure of the difference between groups. RESULTS: List length at registration was associated with length of wait (log-rank test 596.4, p < 0.0001). Patients who were registered when the list length exceeded the weekly service capacity had 70% lower conditional probability of undergoing surgery than those on a list with fewer patients (rate ratio 0.30, 95% confidence interval [CI] 0.26-0.36) after adjustment for sex, age, procedure and period. Registering more than 5 patients when the list was short had an independent effect (rate ratio 0.61, CI 0.45-0.82). CONCLUSIONS: The number of registrants on a surgical wait list has an effect on the length of delay in providing necessary treatment. Our results suggest that a regulated list-length policy may contribute to reducing waiting times. Hospital managers may also use the findings to reduce uncertainty in reporting expected waits given the current list size, thereby improving resource planning.

Cohort Studies↗
PubMed2003

The prognostic importance of endothelial dysfunction and carotid atheroma burden in patients with coronary artery disease.

OBJECTIVES: The goal of this study was to determine the relative prognostic importance of noninvasive measures of endothelial function and atheroma burden in patients with coronary artery disease (CAD). BACKGROUND: Direct measurement of atherosclerosis by carotid ultrasound and endothelial function assessment by brachial artery flow-mediated dilation (FMD) have both been shown to predict vascular events. The combined prognostic utility of carotid ultrasound and FMD relative to traditional risk markers and cardiovascular fitness has not been evaluated. METHODS: A total of 152 patients with CAD underwent metabolic testing, exercise stress tests, carotid ultrasound, and endothelial function measurements. RESULTS: Patients were followed for 34 +/- 10 months during which 22 vascular events occurred. Peak FMD (p = 0.012) and FMD/nitroglycerin-mediated dilation (NMD) ratio (p = 0.008) were lower in subjects with events. Univariate analysis with Cox proportional hazards modeling identified plaque area (p = 0.0047), total area (p = 0.0085), peak FMD (p = 0.01), FMD/NMD ratio (p = 0.008), stress test workload (p = 0.027), long-acting nitroglycerin (NTG) (p = 0.0071), and calcium blockers (p = 0.0057) as predictors of adverse events. Multivariate analysis showed that FMD/NMD ratio (p < 0.0001), carotid plaque area (p = 0.06), and NTG (p = 0.005) were independent predictors. Based on median values, subjects were divided into high and low "plaque burden" groups and into high and low FMD/NMD subgroups. Patients with high FMD/NMD had low event rates irrespective of the degree of carotid atheroma. Patients with low FMD/NMD and high "plaque burden" had the highest event rate (p < 0.05). CONCLUSIONS: The structural and functional status of the vasculature are independent predictors of coronary events as shown by noninvasive measurement of endothelial function and carotid atheroma burden in patients with CAD. Preserved endothelial function attenuates the risk of future events associated with a high plaque burden.

Carotid Artery Diseases↗
PubMedDate not supplied

Dietary measures and exercise training contribute to improvement of endothelial function and atherosclerosis even in patients given intensive pharmacologic therapy.

PURPOSE: Atherosclerosis contributes to cardiovascular mortality and morbidity even with aggressive lipid management. Our objective is to determine whether a combined pharmacological and lifestyle intervention can improve atherosclerosis. METHODS: We conducted a 2-year observational study at a specialized clinic in a tertiary care hospital. One hundred fifty-six subjects with coronary disease were enrolled in an intensive pharmacological management and lifestyle measures (including counseling and exercise training) program designed to reach specific targets. The main outcome measures were carotid intima media thickness and plaque area; brachial artery flow-mediated dilation; nitroglycerin-mediated dilation; flow-mediated dilation-nitroglycerin-mediated dilation ratio; laboratory parameters including lipids, glucose, creatinine, and homocysteine; and physical fitness. RESULTS: At completion, there were improvements in lipids and physical fitness. There were no overall changes in flow-mediated dilation, nitroglycerin-mediated dilation, or carotid intima media thickness in the entire cohort. However, multivariate logistic regression showed that dietary and exercise variables, such as increasing fiber intake and reducing body weight and body fat percentage, were independent predictors of improvements in endothelial function and carotid plaque burden. CONCLUSIONS: Even in the setting of intensive pharmacological therapy, lifestyle interventions, including exercise training and dietary changes, are important determinants of improved endothelial function and atherosclerosis.

Analysis of Variance↗