There are limited population-based data available describing trends in the long-term prognosis of patients discharged from the hospital after an initial acute myocardial infarction (AMI). Our objectives were to describe multidecade trends in post-discharge mortality and their association with hospital management practices in patients discharged from all medical centers in Central Massachusetts after a first AMI. Residents of the Worcester, Massachusetts, metropolitan area discharged from all hospitals in Central Massachusetts after a first AMI from 1975 to 2009 comprised the study population (n = 8,728). Multivariable-adjusted logistic regression analyses were used to examine the association between year of hospitalization and 1-year post-discharge mortality. The average age of this population was 66 years, and 40% were women. Patients hospitalized in 1999 to 2009, compared with those discharged in 1975 to 1984, were older, more likely to be women, and have multiple previously diagnosed co-morbidities. Hospital use of invasive cardiac interventions and medications increased markedly over time. Unadjusted 1-year mortality rates were 12.9%, 12.5%, and 15.8% for patients discharged during 1975 to 1984, 1986 to 1997, and 1999 to 2009, respectively. After adjusting for several demographic characteristics, clinical factors, and inhospital complications, there were no significant differences in the odds of dying at 1-year post-discharge during the years under study. After further adjustment for hospital treatment practices, the odds of dying at 1 year post-discharge was 2.43 (95% confidence interval = 1.83 to 3.23) times higher in patients hospitalized in 1999 to 2009 than in 1975 to 1984. In conclusion, the increased use of invasive cardiac interventions and pharmacotherapies was associated with enhanced long-term survival in patients hospitalized for a first AMI.
The primary objective of our large community-based study was to examine changing trends in long-term prognosis in residents of the Worcester, Massachusetts, metropolitan area discharged from all medical centers in Central Massachusetts after a first acute myocardial infarction (AMI) over an approximate 35-year period (1975 to 2009). A secondary study goal was to understand whether, and to what extent, increases in the use of effective cardiac treatment approaches during the patient’s index hospitalization were associated with changes in long-term mortality. Data from the population-based Worcester Heart Attack Study were used for purposes of this investigation.
Methods
Described elsewhere in detail, the Worcester Heart Attack Study is an ongoing population-based investigation describing long-term trends in the epidemiology of AMI in residents of the Worcester, Massachusetts, metropolitan area (2000 census = 478,000) hospitalized at all 16 medical centers in Central Massachusetts on an approximate biennial basis during 1975, 1978, 1981, 1984, 1986, 1988, 1990, 1991, 1993, 1995, 1997, 1999, 2001, 2003, 2005, 2007, and 2009. In 2000, the median age of residents of the Worcester metropolitan area was 37 years, 49% were men, 89% were white, and approximately 25% had a bachelor’s degree or higher. Because of hospital closures, mergers, or conversion to long-term care or rehabilitation facilities, fewer hospitals (n = 11) have been providing care to greater Worcester residents during the most recent years of this community-wide investigation.
Computerized printouts of patients discharged from all greater Worcester hospitals with possible AMI ( International Classification of Disease 9 codes: 410 to 414 and 786.5) were identified. Cases of possible AMI were independently validated using predefined criteria for AMI ; these criteria included a suggestive clinical history, increases in several serum biomarkers (e.g., creatine kinase, creatine kinase-MB, and troponin values), and serial electrocardiographic findings during hospitalization consistent with the presence of AMI. Patients who satisfied at least 2 of these 3 criteria, and were residents of the Worcester metropolitan area, were included.
For purposes of the present study, we restricted our sample to adult residents of the Worcester metropolitan area who survived their index hospitalization for a first AMI from 1975 to 2009. Patients with an initial AMI were identified by either mention in the review of hospital charts that this was the patient’s first admission for an AMI or through the review of previous hospital records and electrocardiograms that failed to indicate the occurrence of a previous AMI. This study was approved by the Institutional Review Board at the University of Massachusetts Medical School.
Trained nurses and physicians abstracted information on patients’ demographic characteristics, medical history, clinical data, and treatment practices through the review of hospital medical records. These factors included patient’s sociodemographic characteristics (age, gender, race, and marital status), year of hospitalization, hospital length of stay, history of previously diagnosed co-morbidities (e.g., stroke, diabetes, and heart failure), AMI type (Q wave vs non-Q wave; ST-segment elevation myocardial infarction [STEMI] vs non-STEMI), and the development of important inhospital complications including atrial fibrillation, cardiogenic shock, heart failure, and stroke.
Data on the receipt of thrombolytic therapy and 3 coronary diagnostic and interventional procedures (cardiac catheterization, percutaneous coronary intervention [PCI], and coronary artery bypass grafting [CABG] surgery) during hospitalization and pharmacotherapies at the time of hospital discharge, including the prescribing of 6 effective cardiac medications (angiotensin-converting inhibitors [ACE-I] or angiotensin receptor blockers [ARBs], anticoagulants, aspirin, β blockers, calcium channel blockers, and lipid-lowering agents), were obtained. Although we collected follow-up information on all study patients through 2012, we examined trends in 1-year post-hospital discharge all-cause mortality rates. This time point was chosen because a number of previous investigations have shown this follow-up point to be a particularly high-risk period for dying in patients discharged from the hospital after an AMI. The approaches used to ascertain survival status after hospital discharge included a review of medical records for additional hospitalizations and a statewide and national search of death certificates for residents of the Worcester metropolitan area.
For ease of analysis and interpretation, we aggregated the 17 individual study years into approximate 3 decade–long time periods (1975 to 1984, earliest; 1986 to 1997, middle; and 1999 to 2009, most recent) for purposes of examining changing trends in 1-year post-discharge mortality rates. These time period categorizations reflect major changes in the management of patients hospitalized with AMI that have occurred over time from the use of mainstay therapies, such as aspirin and β blockers during the earliest years under study, to the use of thrombolytic therapy in the mid-1980s and to the use of more aggressive and invasive interventions including PCI and lipid-lowering therapy during the most recent decade under study. Differences in the distribution of various patient demographic and clinical characteristics, development of inhospital clinical complications, and hospital treatment practices between the 3 time periods were examined using the analysis of variance test for continuous variables and the chi-square test for categorical variables. The Cochran-Armitage tests and linear regression models were used to test for linear trends over time among categorical variables and continuous variables, respectively.
Long-term mortality after hospital discharge was examined by calculating 1-year all-cause mortality rates as we did not collect information on cause-specific mortality. Multivariable-adjusted logistic regression analyses were performed to examine the association between the main explanatory variable of time period of hospitalization (1975 to 1984, earliest; 1986 to 1997, middle; and 1999 to 2009, most recent) and the outcome of 1-year post-discharge all-cause mortality (dead vs alive) while adjusting for several potentially confounding variables of prognostic importance. Because the 3 time periods reflect changes in the management of patients hospitalized with AMI and a linear relation with the outcome of total mortality was not assumed, we dummy coded this variable with the earliest period (1975 to 1984) serving as the reference group. Several covariates associated with long-term mortality in patients discharged from the hospital after AMI in previous studies were examined sequentially in 4 blocks. The first block included age, gender, race, marital status, and previously diagnosed co-morbid conditions (i.e., angina, diabetes, heart failure, hypertension, and stroke). The second block included AMI type (Q wave vs non-Q wave), inhospital clinical complications (i.e., atrial fibrillation, heart failure, cardiogenic shock), and hospital length of stay. The third block included inhospital management practices as represented by the receipt of thrombolytic therapy and 3 coronary diagnostic and interventional procedures (i.e., cardiac catheterization, PCI, and CABG). The fourth block included the prescribing of 4 guideline-recommended cardiac medications (i.e., ACE-I or ARBs, aspirin, β blockers, and lipid-lowering agents) at the time of hospital discharge. Based on their clinical relevance and preliminary univariate associations, all potential covariates were retained and fitted into multivariable logistic regression models by adding the blocks of variables sequentially.
We also repeated our multivariable-adjusted logistic regression analyses restricted to patients hospitalized during the most recent decade under study (1999 to 2009) for purposes of providing a relatively contemporary perspective into the association between year of hospitalization and 1-year all-cause mortality. For this analysis, we also adjusted for type of AMI (STEMI and non-STEMI) because information about whether the patient’s electrocardiogram showed changes in ST-segment elevation or otherwise was only obtained from 1999 on. Our results were presented as multivariable-adjusted odds ratios and accompanying 95% confidence intervals, which were calculated based on standard errors clustered at the hospital level to account for potential within-hospital correlation with variance adjustment.
Results
The study population consisted of 8,728 adult residents of the Worcester metropolitan area who survived their hospitalization for an independently confirmed first AMI at all medical centers in Central Massachusetts from 1975 to 2009. Overall, the average age of this patient population was 66.4 years, 60.0% were men, 95.4% were white, and 61.0% were married. Patients discharged from all greater Worcester hospitals after a first AMI during recent, compared with earlier study years were significantly older, were more likely to be women, and were less likely to be married. The proportion of patients with a Q-wave myocardial infarction, and the average hospital stay, decreased markedly over time ( Table 1 ).
| Variable | 1975-1984 (n=1,820) | 1986-1997 (n=3,407) | 1999-2009 (n=3,501) |
|---|---|---|---|
| Mean Age (years) ∗ | 63.8 | 66.3 | 67.9 |
| Age (years) ∗ | |||
| <55 | 24.7% | 21.0% | 21.5% |
| 55-64 | 27.8% | 20.7% | 19.9% |
| 65-74 | 15.5% | 21.9% | 25.1% |
| 75-84 | 15.5% | 21.9% | 25.1% |
| ≥85 | 6.2% | 8.4% | 13.4% |
| Men ∗ | 64.3% | 59.5% | 58.2% |
| White ∗ | 97.2% | 96.1% | 93.7% |
| Married ∗ | 67.1% | 62.2% | 56.6% |
| ST-segment myocardial infarction | – | – | 40.0% |
| Q-wave ∗ | 64.7% | 51.3% | 27.6% |
| Mean hospital length of stay (days) ∗ | 16.8 | 9.5 | 5.5 |
| Angina pectoris ∗ | 18.4% | 19.0% | 12.8% |
| Heart failure ∗ | 6.5% | 7.8% | 13.8% |
| Hypertension ∗ | 44.1% | 51.7% | 65.5% |
| Stroke ∗ | 4.6% | 6.7% | 8.3% |
| Diabetes mellitus ∗ | 18.5% | 23.2% | 27.1% |
∗ P-values derived from Analysis of variance (ANOVA) tests for continuous variables and chi-square tests for categorical variables were all <0.001; p-values for trend tests derived from Cochran-Armitage tests for categorical variables and linear regression models for continuous variables were all <0.001.
During the most recent years under study, patients who survived their initial AMI were more likely to have a history of heart failure, hypertension, diabetes, or stroke than patients hospitalized during earlier study periods ( Table 1 ). The proportion of patients with multiple (≥2) co-morbidities increased from 24.2% in 1975 to 1984 to 36.6% in 1999 to 2009 (p for trend <0.001).
Overall, the likelihood of developing cardiogenic shock or a stroke during the patient’s index hospitalization remained relatively low (2.7% and 1.0%, respectively), whereas the incidence rates of inhospital heart failure and atrial fibrillation were considerably higher (30.5% and 15.2%, respectively). In general, we observed an upward trend in the proportion of patients who developed cardiogenic shock (p for trend <0.001) and atrial fibrillation (p for trend <0.001) but a downward trend in the development of acute heart failure (p for trend = 0.043) from the earliest to the most recent years under study; the development of acute stoke remained low and stable throughout the years under study (p = 0.67; Figure 1 ).
The use of cardiac catheterization and PCI has increased markedly over time, whereas the proportion of patients who underwent CABG surgery during their index hospitalization has increased but remained relatively low during the years under study (all p values for trend <0.001). The use of thrombolytic therapy increased during the 1990s but markedly decreased thereafter. Cardiac catheterization, PCI, CABG surgery, and thrombolytic therapy were used in 78.2%, 60.8%, 6.7%, and 0.2% of patients who survived a first AMI in 2009 ( Figure 2 ).
Marked increases in the prescribing of ACE-I or ARBs, aspirin, β blockers, and lipid-lowering medications at the time of hospital discharge were observed during the years under study (p for trend <0.001) ( Figure 2 ). In contrast, use of calcium channel blockers has decreased markedly during recent years (p for trend <0.001). The use of anticoagulants in patients who survived a first AMI increased through the mid-1990s, decreased in the late-1990s, and remained stable during the 2000s ( Figure 2 ). ACE-I or ARBs, aspirin, β blockers, and lipid-lowering medications were prescribed at the time of hospital discharge in 94.0%, 64.4%, 90.7%, and 90.1%, respectively, of patients who survived a first AMI in 2009.
The overall (1975 to 2009) 1-year all-cause death rates after hospital discharge for patients who survived a first AMI were 13.9%. The average 1-year all-cause mortality rates remained relatively stable from 1975 to 1984 (12.9%) to 1986 to 1997 (12.5%) but increased during 1999 to 2009 (15.8%). In examining changing trends in 1-year all-cause mortality after hospital discharge, our unadjusted analyses showed that, compared with patients surviving an initial AMI in 1975 to 1984, there were no significant differences in the odds of dying at 1-year post-discharge in patients surviving a first AMI in 1986 to 1997 and in 1999 to 2009 ( Table 2 ).
| Unadjusted | Adjusted for sociodemographics and comorbidities ∗ | Further adjusted for in-hospital factors † | Further adjusted for in-hospital management ‡ | Further adjusted for discharge medications § | |
|---|---|---|---|---|---|
| Crude OR (95% CI) | Adjusted OR (95% CI) | ||||
| 1975-1984 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| 1986-1997 | 0.96 (0.64-1.45) | 0.72 (0.53-0.97) | 0.80 (0.60-1.08) | 1.13 (0.85-1.51) | 1.30 (0.97-1.74) |
| 1999-2009 | 1.27 (0.80-2.02) | 0.73 (0.51-1.04) | 0.82 (0.59-1.15) | 1.65 (1.25-2.17) | 2.43 (1.83-3.23) |
| 1999-2001 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |
| 2003-2005 | 0.84 (0.56-1.25) | 0.69 (0.50-0.96) | 0.68 (0.48-0.97) | 0.84 (0.60-1.17) | 0.96 (0.67-1.35) |
| 2007-2009 | 0.71 (0.46-1.08 ) | 0.62 (0.44-0.86) | 0.62 (0.47-0.83) | 0.89 (0.70-1.15) | 1.13 (0.86-1.48) |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
