Measuring outcomes: one month survival after acute myocardial infarction in Scotland

30-Day Survival Probabilities as a Quality Indicator for Norwegian Hospitals: Data Management and Analysis

Background

The Norwegian Knowledge Centre for the Health Services (NOKC) reports 30-day survival as a quality indicator for Norwegian hospitals. The indicators have been published annually since 2011 on the website of the Norwegian Directorate of Health (www.helsenorge.no), as part of the Norwegian Quality Indicator System authorized by the Ministry of Health. Openness regarding calculation of quality indicators is important, as it provides the opportunity to critically review and discuss the method. The purpose of this article is to describe the data collection, data pre-processing, and data analyses, as carried out by NOKC, for the calculation of 30-day risk-adjusted survival probability as a quality indicator.

Methods and Findings

Three diagnosis-specific 30-day survival indicators (first time acute myocardial infarction (AMI), stroke and hip fracture) are estimated based on all-cause deaths, occurring in-hospital or out-of-hospital, within 30 days counting from the first day of hospitalization. Furthermore, a hospital-wide (i.e. overall) 30-day survival indicator is calculated. Patient administrative data from all Norwegian hospitals and information from the Norwegian Population Register are retrieved annually, and linked to datasets for previous years. The outcome (alive/death within 30 days) is attributed to every hospital by the fraction of time spent in each hospital. A logistic regression followed by a hierarchical Bayesian analysis is used for the estimation of risk-adjusted survival probabilities. A multiple testing procedure with a false discovery rate of 5% is used to identify hospitals, hospital trusts and regional health authorities with significantly higher/lower survival than the reference. In addition, estimated risk-adjusted survival probabilities are published per hospital, hospital trust and regional health authority. The variation in risk-adjusted survival probabilities across hospitals for AMI shows a decreasing trend over time: estimated survival probabilities for AMI in 2011 varied from 80.6% (in the hospital with lowest estimated survival) to 91.7% (in the hospital with highest estimated survival), whereas it ranged from 83.8% to 91.2% in 2013.

Conclusions

Since 2011, several hospitals and hospital trusts have initiated quality improvement projects, and some of the hospitals have improved the survival over these years. Public reporting of survival/mortality indicators are increasingly being used as quality measures of health care systems. Openness regarding the methods used to calculate the indicators are important, as it provides the opportunity of critically reviewing and discussing the methods in the literature. In this way, the methods employed for establishing the indicators may be improved.

Acute Case-Fatality Rates of Stroke and Acute Myocardial Infarction in a Japanese Population: Takashima Stroke and AMI Registry, 1989–2005

Background

Few comprehensive stroke and acute myocardial infarction registries of long duration exist in Japan to illustrate trends in acute case-fatality of stroke and acute myocardial infarction with greater precision. We examined 17-year case-fatality rates of stroke and acute myocardial infarction using an entire community-monitoring registration system to investigate trends in these rates over time in a Japanese population.

Methods

Data were obtained from the Takashima Stroke and AMI Registry covering a stable population of approximately 55 000 residents of Takashima County in central Japan. We divided the total observation period of 17 years into four periods, 1989–1992, 1993–1996, 1997–2000, and 2001–2005. We calculated gender, age-specific and age-adjusted acute case-fatality rates (%) of stroke and acute myocardial infarction across these four periods.

Results

During the study period of 1989–2005, there were 341 fatal cases within 28 days of onset among 2239 first-ever stroke events and 163 fatal cases among 433 first-ever acute myocardial infarction events. The age-adjusted acute case-fatality rate of stroke was 14·9% in men and 15·7% in women. The age-adjusted acute case-fatality rate of acute myocardial infarction was 34·3% in men and 43·3% in women. The age-adjusted acute case-fatality rates of stroke and acute myocardial infarction showed insignificant differences across the four time periods. The average annual change in the acute case-fatality rate of stroke (–0·2%; 95% CI: −2·4–2·1) and acute myocardial infarction (2·7%; 95% CI: −0·7–6·1) did not change significantly across the study years.

Conclusions

The acute case-fatality rates of stroke and acute myocardial infarction have remained stable from 1989 to 2005 in a rural and semi-urban Japanese population.

Coronary heart disease mortality among young adults in Scotland in relation to social inequalities: time trend study

OBJECTIVE

To examine recent trends and social inequalities in age specific coronary heart disease mortality.

DESIGN

Time trend analysis using joinpoint regression.

SETTING

Scotland, 1986-2006.

PARTICIPANTS

Men and women aged 35 years and over.

MAIN OUTCOME MEASURES

Age adjusted and age, sex, and deprivation specific coronary heart disease mortality.

RESULTS

Persistent sixfold social differentials in coronary heart disease mortality were seen between the most deprived and the most affluent groups aged 35-44 years. These differentials diminished with increasing age but equalised only above 85 years. Between 1986 and 2006, overall, age adjusted coronary heart disease mortality decreased by 61% in men and by 56% in women. Among middle aged and older adults, mortality continued to decrease fairly steadily throughout the period. However, coronary heart disease mortality levelled from 1994 onwards among young men and women aged 35-44 years. Rates in men and women aged 45-54 showed similar flattening from about 2003. Rates in women aged 55-64 may also now be flattening. The flattening of coronary heart disease mortality in younger men and women was confined to the two most deprived fifths.

CONCLUSIONS

Premature death from coronary heart disease remains a major contributor to social inequalities. Furthermore, the flattening of the decline in mortality for coronary heart disease among younger adults may represent an early warning sign. The observed trends were confined to the most deprived groups. Marked deterioration in medical management of coronary heart disease seems implausible. Unfavourable trends in the major risk factors for coronary heart disease (smoking and poor diet) thus provide the most likely explanation for these inequalities.

Increasing socioeconomic inequalities in first acute myocardial infarction in Scotland, 1990-92 and 2000-02

Background

Despite substantial declines, Ischaemic Heart Disease (IHD) remains the largest cause of death in Scotland and mortality rates are among the worst in Europe. There is evidence of strong, persisting regional and socioeconomic inequalities in IHD mortality, with the majority of such deaths being due to Acute Myocardial Infarction (AMI). We examine the changes in socioeconomic and geographic inequalities in first AMI events in Scotland and their interactions with age and gender.

Methods

We used linked hospital discharge and death records covering the Scottish Population (5.1 million). Risk ratios (RR) of AMI incidence by area deprivation and age for men and women were estimated using multilevel Poisson modelling. Directly standardised rates were presented within these stratifications.

Results

During 1990–92 74,213 people had a first AMI event and 56,995 in 2000–02. Adjusting for area deprivation accounted for 59% of the geographic variability in AMI incidence rates in 1990–92 and 33% in 2000–02. Geographic inequalities in male incidence reduced; RR for smaller areas (comparing area on 97.5th centile to 2.5th) reduced from 1.42 to 1.19. This was not true for women; RR increased from 1.45 to 1.59. The socioeconomic gradient in AMI incidence increased over time (p-value < 0.001) but this varied by age and gender. The gradient across deprivation categories for male incidence in 1990–92 was most pronounced at younger ages; RR of AMI in the most deprived areas compared to the least was 2.6 (95% CI: 1.6–4.3) for those aged 45–59 years and 1.6 (1.1–2.5) at 60–74 years. This association was also evident in women with even stronger socioeconomic gradients; RRs for these age groups were 4.4 (3.4–5.5), and 1.9 (1.7–2.2). Inequalities increased by 2000–02 for both sexes; RR for men aged 45–59 years was 3.3 (3.0–3.6) and for women was 5.6 (4.1–7.7)

Conclusion

Relative socioeconomic inequalities in AMI incidence have increased and gradients are steepest in young women. The geographical patterning of AMI incidence cannot be fully explained by socioeconomic deprivation. The reduction of inequalities in AMI incidence is key to reducing overall inequalities in mortality and must be a priority if Scotland is to achieve its health potential.

Hospital Variation in Mortality After First Acute Myocardial Infarction in Denmark From 1995 to 2002

BACKGROUND

This study used linked data from the National Hospital Registry to determine the factors that contribute to differences between hospitals in all-cause mortality after first acute myocardial infarction (AMI) between 1995 and 2002.

METHODS

The study included 64,321 patients with their first admission for AMI between 1995 and 2002 and surviving the day of admission. Multilevel logistic regression was used to determine the relationships between regional and hospital characteristics and 28-day and 365-day mortality after adjusting for individual characteristics, period, and medical history.

RESULTS

Tertiary cardiac care centers (odds ratio [OR], 0.80; 95% confidence interval [CI], 0.67-0.96) and main regional hospitals (OR, 0.90; 95% CI, 0.80-0.99) had improved 28-day mortality compared with local hospitals. A 2-fold increase in annual total MI volume decreased 28-day mortality (OR, 0.91; 95% CI, 0.87-0.94) and 365-day mortality (OR, 0.95; 95% CI, 0.91-0.98). Differences between hospitals were more substantial for short-term mortality, such that patients were about twice as likely to die within 28 days in hospitals with the worst performance versus those with the best performance. Higher regional AMI incidence was associated with lower mortality before 2000; this disappeared after 2000. Other regional contextual characteristics had very modest effects on mortality.

CONCLUSIONS

Type of hospital, and especially total MI volume at the hospital level, were significantly associated with mortality after AMI. Individual hospitals varied substantially in both short- and long-term mortality.

Reduced between-hospital variation in short term survival after acute myocardial infarction: the result of improved cardiac care?

OBJECTIVES

To re-examine interhospital variation in 30 day survival after acute myocardial infarction (AMI) 10 years on to see whether the appointment of new cardiologists and their involvement in emergency care has improved outcome after AMI.

DESIGN

Retrospective cohort study.

SETTING

Acute hospitals in Scotland.

PARTICIPANTS

61,484 patients with a first AMI over two time periods: 1988-1991; and 1998-2001.

MAIN OUTCOME MEASURES

30 day survival.

RESULTS

Between 1988 and 1991, median 30 day survival was 79.2% (interhospital range 72.1-85.1%). The difference between highest and lowest was 13.0 percentage points (age and sex adjusted, 12.1 percentage points). Between 1998 and 2001, median survival rose to 81.6% (and range decreased to 78.0-85.6%) with a difference of 7.6 (adjusted 8.8) percentage points. Admission hospital was an independent predictor of outcome at 30 days during the two time periods (p < 0.001). Over the period 1988-1991, the odds ratio for death ranged, between hospitals, from 0.71 (95% confidence interval (CI) 0.58 to 0.88) to 1.50 (95% CI 1.19 to 1.89) and for the period 1998-2001 from 0.82 (95% CI 0.60 to 1.13) to 1.46 (95% CI 1.07 to 1.99). The adjusted risk of death was significantly higher than average in nine of 26 hospitals between 1988 and 1991 but in only two hospitals between 1998 and 2001.

CONCLUSIONS

The average 30 day case fatality rate after admission with an AMI has fallen substantially over the past 10 years in Scotland. Between-hospital variation is also considerably less notable because of better survival in the previously poorly performing hospitals. This suggests that the greater involvement of cardiologists in the management of AMI has paid dividends.

Case-fatality rates for myocardial infarction declined in Denmark and Sweden during 1987-1999

OBJECTIVE

To evaluate trends in prognosis after acute myocardial infarction (AMI) between Denmark and Sweden using routinely collected data and different case-fatality measures.

STUDY DESIGN AND SETTING

We compared three case-fatality measures during 1987-1999 using national registries in Denmark and Sweden, and extended these measures with underlying deaths of ischemic heart disease and sudden deaths of unknown cause.

RESULTS

Changed coding practice distorted trends of case fatality rates during the day of the event. In general, Denmark had higher case-fatality rates, but trends in hospital-based rates were very similar, except for men 35-64 years old; Denmark declined more steeply. Short- and long-term prognosis improved considerably: the odds ratios for case fatality during days 1-28 for 1999 vs. 1987 were 0.48 among men in Denmark (women 0.58) and 0.53 among men in Sweden (women 0.55) and the odds ratios for case fatality during days 29-365 for 1999 vs. 1987 were 0.56 among men in Denmark (women 0.65) and 0.66 among men in Sweden (women 0.67).

CONCLUSION

Short- and long-term prognosis improved considerably during 1987-1999 in Denmark and Sweden. Case fatality during the day of the event is epidemiologically important, but less certain than case-fatality measures defined after the day of the event when comparing countries.

Do regulations limiting residents' work hours affect patient mortality?

OBJECTIVE

To conduct a statewide analysis of the effect of New York's regulations, limiting internal medicine and family practice residents' work hours, on patient mortality.

DESIGN

Retrospective study of inpatient discharge files for 1988 (before the regulations) and 1991 (after the regulations).

SETTING AND PATIENTS

Adult patients discharged from New York teaching hospitals (170214) and nonteaching hospitals (143,455) with a principal diagnosis of congestive heart failure, acute myocardial infarction, or pneumonia, for the years 1988 and 1991 (periods before and after Code 405 regulations went into law). Patients from nonteaching hospitals served as controls.

MEASUREMENT

In-hospital mortality.

RESULTS

Combined unadjusted mortality for congestive heart failure, acute myocardial infarction, and pneumonia patients declined between 1988 and 1991 in both teaching (14.1% to 13.0%; P =.0001) and nonteaching hospitals (14.0% to 12.5%; P =.0001). Adjusted mortality also declined between 1988 and 1991 in both teaching (odds ratio [OR], death 1991/1988, 0.868; 95% confidence interval [CI], 0.843 to 0.894; P =.0001) and nonteaching hospitals (OR, death 1991/1988, 0.853; 95% CI, 0.826 to 0.881; P =.0001). This beneficial trend toward lower mortality over time was nearly identical between teaching and nonteaching hospitals (P =.4348).

CONCLUSION

New York's mandated limitations on residents' work hours do not appear to have positively or negatively affected in-hospital mortality from congestive heart failure, acute myocardial infarction, or pneumonia in teaching hospitals.

Trends in incidence and case fatality rates of acute myocardial infarction in Denmark and Sweden

OBJECTIVE

To compare the incidence and case fatality of acute myocardial infarction in Denmark and Sweden.

DESIGN

A cohort study, linking the national registries of hospital admissions and causes of death in the two countries.

PATIENTS

All admissions and deaths with acute myocardial infarction as primary or secondary diagnosis were extracted (Denmark, 1978 to 1998; Sweden, 1987 to 1999).

MAIN OUTCOME MEASURES

The incidence was estimated using the first acute myocardial infarct for each patient. Case fatality was estimated in the first 28 days after acute myocardial infarction, including prehospital deaths. All rates were adjusted for age.

RESULTS

The incidence of myocardial infarction and the case fatality declined significantly among all subgroups of patients. Case fatality was higher in Denmark early in the study period (1987-1990) than in Sweden. The odds ratios (OR) ranged from 1.28 to 1.50 in the four age groups. In 1994-1999, the prognosis of patients younger than 75 years did not differ. Patients aged 75-94 years still fared worse in Denmark (OR 1.21, 95% confidence interval 1.17 to 1.27). Women aged 30-54 years had a worse prognosis than men in both Denmark and Sweden (OR associated with male sex 0.85 and 0.90, respectively). In contrast, for patients older than 65 years, women had a better prognosis than men. This difference in the effect of sex with age was significant (p < 0.0001) and did not change over time.

CONCLUSIONS

Case fatality after acute myocardial infarction was notably higher in Denmark than in Sweden in 1987-1991, but in the later periods the prognosis was comparable in the two countries.

Age, sex, and social trends in out-of-hospital cardiac deaths in Scotland 1986-95: a retrospective cohort study

BACKGROUND

Most deaths from coronary heart disease occur out of hospital. Hospital patients face social, age, and sex inequalities. Our aim was to examine inequalities and trends in out-of-hospital cardiac deaths.

METHODS

We used the Scottish record linked database to identify all deaths from acute myocardial infarction that occurred in Scotland (population 5.1 million), in 1986-95. We have compared population-based death rates for men and women across age and social groups.

FINDINGS

Between 1986 and 1995, 83365 people died from acute myocardial infarction, out of hospital and without previous hospital admission (44655 men, 38710 women); and 117749 were admitted with a first acute myocardial infarction, of whom 37020 died within 1 year. Thus, out-of-hospital deaths accounted for 69.2% (95% CI 69.0-69.5) of all 120385 deaths. Out-of-hospital deaths, measured as a proportion of all acute myocardial infarction events (deaths plus first hospital admissions), increased with age, from 20.1% (19.2-21.0) in people younger than 55 years, to 62.1% (61.3-62.9) in those older than 85 years. Population-based out-of-hospital mortality rates fell by a third in men and by a quarter in women. Mean yearly falls were larger in people aged 55-64 years (5.6% per year in men, 3.7% in women), than in those older than 85 years (2.5% in men and women). Mortality rates were substantially higher in deprived socioeconomic groups than in affluent groups, especially in people younger than 65 years.

INTERPRETATION

These inequalities in age, sex, and socioeconomic class should be actively addressed by prevention strategies for coronary heart disease.

Causes and consequences of comorbidity: a review

A literature search was carried out to identify and summarize the existing information on causes and consequences of comorbidity of chronic somatic diseases. A selection of 82 articles met our inclusion criteria. Very little work has been done on the causes of comorbidity. On the other hand, much work has been done on consequences of comorbidity, although comorbidity is seldom the main subject of study. We found comorbidity in general to be associated with mortality, quality of life, and health care. The consequences of specific disease combinations, however, depended on many factors. We recommend more etiological studies on shared risk factors, especially for those comorbidities that occur at a higher rate than expected. New insights in this field can lead to better prevention strategies. Health care workers need to take comorbid diseases into account in monitoring and treating patients. Future studies on consequences of comorbidity should investigate specific disease combinations.

Socioeconomic differentials in recurrent ischaemia and mortality after acute myocardial infarction

OBJECTIVE

To examine the influence of socioeconomic deprivation on case fatality following acute myocardial infarction.

DESIGN

Prospective cohort observational study.

SETTING

General hospital.

PATIENTS

1417 white and south Asian patients admitted with acute myocardial infarction between January 1988 and December 1996, and classified by the Carstairs socioeconomic deprivation score of the enumeration district of residence.

MAIN OUTCOME MEASURES

30 day and one year survival.

RESULTS

There was little variation across deprivation groups in age, sex, or smoking status, though a higher proportion of patients from more deprived enumeration districts were diabetic and of south Asian origin, and a higher proportion of them developed Q wave infarction and left ventricular failure. There was no appreciable variation in clinical treatment with deprivation. Patients from more deprived enumeration districts had a higher risk of recurrent ischaemic events (death, recurrent myocardial infarction, or unstable angina) over the first 30 days: event free survival (95% confidence interval (CI)) of the most deprived quartile was 0.79 (95% CI 0.74 to 0.83) compared with 0.85 (95% CI 0.80 to 0.88) in the least deprived quartile. The unadjusted hazard ratio corresponding to an increase from the 5th to 95th centile of the deprivation distribution was 1.54 (95% CI 1.02 to 2.32), and 1.59 (95% CI 1.03 to 2.44) after adjustment for age, sex, racial group, diabetes, acute treatment with thrombolysis and aspirin, and left ventricular failure. Survival from 30 days to one year, however, did not show a socioeconomic gradient (hazard ratio adjusted for the same variables was 1.07 (95% CI 0.68 to 1.70)).

CONCLUSIONS

In patients hospitalised with acute myocardial infarction, there is a strong association between early recurrent ischaemic events and socioeconomic deprivation that is not accounted for by clinical presentation or treatment. This association appears to be attenuated over time.

Evidence of improving prognosis in heart failure: trends in case fatality in 66 547 patients hospitalized between 1986 and 1995

BACKGROUND

Contemporary survival in unselected patients with heart failure and the population impact of newer therapies have not been widely studied. Therefore, we have documented case-fatality rates (CFRs) over a recent 10-year period.

METHODS AND RESULTS

In Scotland, all hospitalizations and deaths are captured on a single database. We have studied case fatality in all patients admitted with a principal diagnosis of heart failure from 1986 to 1995. A total of 66 547 patients (47% male) were studied. Median age was 72 years in men and 78 years in women. Crude CFRs at 30 days and at 1, 5, and 10 years were 19.9%, 44.5%, 76.5%, and 87.6%, respectively. Median survival was 1.47 years in men and 1.39 years in women (2.47 and 2. 36 years, respectively, in those surviving 30 days). Age had a powerful effect on survival, and sex, comorbidity, and deprivation had modest effects. One-year CF was 24.2% in those aged <55 years and 58.1% in those aged >84 years. After adjustment, 30-day CFRs fell between 1986 and 1995, by 26% (95% CI 15 to 35, P<0.0001) in men and 17% (95% CI 6 to 26, P<0.0001) in women. Longer term CFRs fell by 18% (95% CI 13 to 24, P<0.0001) in men and 15% (95% CI 10 to 20, P<0.0001) in women. Median survival increased from 1.23 to 1. 64 years.

CONCLUSIONS

Heart failure CF is much higher in the general population than in clinical trials, especially in the elderly. Although survival has increased significantly over the last decade, there is still much room for improvement.

Hospital mortality of acute myocardial infarction in the thrombolytic era

OBJECTIVE

To examine the management and outcome of an unselected consecutive series of patients admitted with acute myocardial infarction to a tertiary referral centre.

DESIGN

A historical cohort study over a three year period (1992-94) of consecutive unselected admissions with acute myocardial infarction identified using the HIPE (hospital inpatient enquiry) database and validated according to MONICA criteria for definite or probable acute myocardial infarction.

SETTING

University teaching hospital and cardiac tertiary referral centre.

RESULTS

1059 patients were included. Mean age was 67 years; 60% were male and 40% female. Rates of coronary care unit (CCU) admission, thrombolysis, and predischarge angiography were 70%, 28%, and 32%, respectively. Overall in-hospital mortality was 18%. Independent predictors of hospital mortality by multivariate analysis were age, left ventricular failure, ventricular arrhythmias, cardiogenic shock, management outside CCU, and reinfarction. Hospital mortality in a small cohort from a non-tertiary referral centre was 14%, a difference largely explained by the lower mean age of these patients (64 years). Five year survival in the cohort was 50%. Only age and left ventricular failure were independent predictors of mortality at follow up.

CONCLUSIONS

In unselected consecutive patients the hospital mortality of acute myocardial infarction remains high (18%). Age and the occurrence of left ventricular failure are major determinants of short and long term mortality after acute myocardial infarction.

Cumulative risk adjusted mortality chart for detecting changes in death rate: observational study of heart surgery

OBJECTIVE

To detect changes in mortality after surgery, with allowance being made for variations in case mix.

DESIGN

Observational study of postoperative mortality from January 1992 to August 1995.

SETTING

Regional cardiothoracic unit.

SUBJECTS

3983 patients aged 16 and over who had open heart operations.

MAIN OUTCOME MEASURES

Preoperative risk factors and postoperative mortality in hospital within 30 days were recorded for all surgical heart operations. Mortality was adjusted for case mix using a preoperative estimate of risk based on additive Parsonnet factors. The number of operations required for statistical power to detect a doubling of mortality was examined, and control limits at a nominal significance level of P=0.01 for detection of an adverse trend were determined.

RESULTS

Total mortality of 7.0% was 26% below the Parsonnet predictor (P<0.0001). There was a highly significant variation in annual case mix (Parsonnet scores 8.7-10.6, P<0.0001). There was no significant variation in mortality after adjustment for case mix (odds ratio 1-1.5, P=0.18) with monitoring by calendar year. With continuous monitoring, however, nominal 99% control limits based on 16 expected deaths were crossed on two occasions.

CONCLUSIONS

Hospital league tables for mortality from heart surgery will be of limited value because year to year differences in death rate can be large (odds ratio 1.5) even when the underlying risk or case mix does not change. Statistical quality control of a single series with adjustment for case mix is the only way to take into account recent performance when informing a patient of the risk of surgery at a particular hospital. If there is an increase in the number of deaths the chances of the next patient surviving surgery can be calculated from the last 16 deaths.