Much of our knowledge about the characteristics, clinical management, and postdischarge outcomes of acute myocardial infarction (AMI) is derived from clinical studies in middle-aged and older subjects with little contemporary information available about the descriptive epidemiology of AMI in relatively young men and women. The objectives of our population-based study were to describe >3-decade-long trends in the clinical features, treatment practices, and long-term outcomes of young adults aged 35 to 54 years discharged from the hospital after AMI. The study population consisted of 2,142 residents of the Worcester (Massachusetts) metropolitan area who were hospitalized with AMI at all central Massachusetts medical centers during 16 annual periods from 1975 to 2007. Our primarily male study population had an average age of 47 years. Patients hospitalized during the most recent decade (1997 to 2007) under study were more likely to have a history of hypertension and heart failure than those hospitalized during earlier study years. Patients were less likely to have developed heart failure or stroke during their hospitalization in the most recent compared with the initial decade under study (heart failure 13.7% and stroke 0.7% vs 20.9% and 2.0%, respectively). One- and 2-year postdischarge death rates also decreased significantly between 1975 to 1986 (6.2% and 9.0%, respectively) and 1988 to 1995 (2.6% and 4.9%). These trends were concomitant with the increasing use of effective cardiac therapies and coronary interventions during hospitalization. The present results provide insights into the changing characteristics, management, and improving long-term outcomes of relatively young patients hospitalized with AMI.
The objectives of our multihospital observational study in residents of central Massachusetts were to describe multidecade-long trends (1975 to 2007) in patient characteristics, treatment practices, and long-term outcomes in adults aged 35 to 54 years discharged from the hospital after acute myocardial infarction (AMI) at all medical centers in central Massachusetts. Data from the Worcester Heart Attack Study were used for purposes of analysis.
Methods
The study population consisted of greater Worcester residents aged 35 to 54 years who were hospitalized with a discharge diagnosis of AMI at all medical centers in the Worcester (Massachusetts) metropolitan area during 16 annual study periods from 1975 to 2007. Sixteen hospitals were originally included in this investigation, but fewer hospitals (n = 11) have been included during recent years because of hospital closures or conversion to long-term care or rehabilitation facilities. We restricted the present sample to adults aged 35 to 54 years who were hospitalized with an independently validated AMI because we were interested in describing the clinical epidemiology of AMI in a comparatively young patient population.
The details of this study have been extensively described. In brief, potentially eligible patients were identified through a review of computerized hospital databases of patients with discharge diagnoses consistent with possible AMI. The medical records of residents of the Worcester metropolitan area (2000 census = 478,000) were reviewed in a standardized manner and the diagnosis of AMI was confirmed according to preestablished criteria.
Trained study clinicians abstracted information from hospital medical records with regards to patient’s demographic characteristics, presenting symptoms, medical history, clinical and laboratory findings, receipt of cardiac treatments and revascularization procedures, length of hospital stay, duration of prehospital delay in seeking acute medical care, and postdischarge survival status. The development of heart failure, cardiogenic shock, atrial fibrillation, and stroke during the patient’s index hospitalization was ascertained through the review of information contained in hospital charts and defined according to preestablished criteria. The approaches used to ascertain survival status after hospital discharge included a review of records for additional hospitalizations and a statewide and national search of death certificates for residents of the Worcester metropolitan area; follow-up was continued through 2009.
Chi-square tests for categorical variables and analysis of variance for continuous variables were used to examine potentially changing trends in various patient demographic and clinical factors. Long-term survival after hospital discharge was examined by calculating all-cause case fatality rates; trends in postdischarge survival were examined through the use of chi-square tests for trends. Logistic regression modeling was used to assess trends in long-term postdischarge death rates while controlling for several potentially confounding demographic, medical history, and clinical characteristics of prognostic importance. Given the nonrandomized observational nature of this investigation, the use of various hospital cardiac treatment approaches was not controlled for in our regression models examining the long-term prognosis of discharged patients. For ease of analysis and interpretation, we aggregated the individual study years into selected approximate decade-long groupings (1975 to 1986, earliest; 1988 to 1995, middle; and 1997 to 2007, most recent) for purposes of examining changing trends in our principal study outcomes. The Committee for the Protection of Human Subjects in Research at the University of Massachusetts Medical School approved this study.
Results
A total of 2,142 greater Worcester adults aged 35 to 54 years were hospitalized with confirmed AMI during the years under study ( Table 1 ). These patients represented 6.3% of all patients hospitalized with AMI during the years under study. These patients were primarily men (80%), were, on average, 47 years old, were typically experiencing their first AMI (80%), and presented with a relatively low frequency of other medical conditions with the exception of previously diagnosed hypertension (43%) and diabetes (17%). More than 1/2 of these young patients (52.4%) were classified as smokers based on information collected during the most recent decade under study.
| Variable | Total Population, n = 2,142 (%) | Study Period | ||
|---|---|---|---|---|
| 1975–1986, n = 642 (%) | 1988–1995, n = 607 (%) | 1997–2007, n = 893 (%) | ||
| Age (yrs, mean ± SD) | 47.4 ± 5.0 | 47.7 ± 5.0 | 46.8 ± 5.0 | 47.6 ± 4.8 |
| Men | 80.4 | 82.1 | 80.2 | 79.4 |
| Angina pectoris | 15.5 | 20.9 | 16.6 | 10.8 |
| Hypertension | 42.9 | 39.4 | 39.4 | 47.8 |
| Stroke | 2.4 | 2.0 | 1.3 | 1.4 |
| Heart failure | 3.9 | 2.7 | 3.0 | 5.4 |
| Diabetes mellitus | 17.4 | 15.0 | 15.2 | 20.7 |
| Admission serum glucose (mg/dl, mean ± SD) | 157.3 ± 75.9 | N/A | 156.3 ± 7.6 | 157.4 ± 76.1 |
| Total cholesterol (mg/dl, mean ± SD) | 213.6 ± 49.8 | 237.1 ± 46.9 | 220.8 ± 44.6 | 193.0 ± 46.7 |
| Length of stay (days, median ± SD) | 6.0 ± 7.6 | 13.0 ± 7.6 | 7.0 ± 6.5 | 3.0 ± 5.2 |
| STEMI | N/A | N/A | N/A | 55.0 |
| Initial AMI | 79.5 | 79.3 | 80.2 | 79.1 |
The percentage of patients reporting previously diagnosed angina decreased from the earliest to the most recent study period, whereas the proportion of patients with a history of hypertension, diabetes, and heart failure increased over time. More than 1/2 of our population presented with an ST-segment elevation myocardial infarction during the most recent study period ( Table 1 ). There were no significant changes in duration of prehospital delay after the onset of acute coronary symptoms over time with a median prehospital delay of 1.8 hours observed during the most recent decade under study. There was a significant decrease in the median hospital stay from approximately 13 days during 1975 to 1986 to 3 days during 1997 to 2007.
Overall, relatively few young patients developed important clinical complications during their index hospitalization with the exception of heart failure (17.2%; Table 2 ). There was a slight increase in the proportion of patients who developed cardiogenic shock from the earliest to the most recent decade under study (1.9% to 2.9%). The percentage of patients experiencing heart failure or stroke decreased markedly during the years under study ( Table 2 ).
| Complication | Total Population (%) | 1975–1986 (%) | 1988–1995 (%) | 1997–2007 (%) | p Value |
|---|---|---|---|---|---|
| Atrial fibrillation | 5.0 | 4.7 | 6.3 | 4.4 | NS |
| Heart failure | 17.2 | 20.9 | 18.5 | 13.7 | <0.01 |
| Stroke | 0.5 | 2.0 | 0 | 0.7 | <0.01 |
| Cardiogenic shock | 2.7 | 1.9 | 0.9 | 2.9 | NS |
There was a marked and steady increase in the use of effective medical therapies over time ( Figure 1 ). In the earliest period, 11% of hospitalized patients were prescribed aspirin and <1% were prescribed a lipid-lowering agent. These percentages increased steadily over time, reaching 89% and 66%, respectively, during the 1997 to 2007 period. Similarly, there were significant increases in the use of combinations of effective cardiac medications (e.g., aspirin, β blockers, angiotensin-converting enzyme inhibitors, and lipid-lowering agents) during the patient’s index hospitalization. From 1975 to 1986, approximately 30% of patients received any 1 or 2 of the 4 effective cardiac medications examined, and few received ≥3. In the most recent decade under study, nearly 80% of relatively young patients were prescribed ≥3 effective cardiac medications during their acute hospitalization ( Figure 2 ). There were also marked increases over time in the proportion of patients undergoing cardiac catheterization and percutaneous coronary intervention during their acute hospitalization ( Figure 3 ).
All-cause postdischarge death rates decreased in our population over time. Overall, 3-month, 1-year, and 2-year death rates were 2.9%, 4.3%, and 5.4%, respectively. The 3-month, 1-year, and 2-year death rates decreased significantly between 1975 to 1986 (2.5%, 6.2%, and 9.0%, respectively) and 1988 to 1995 (0.8%, 2.6%, and 4.9%, respectively).
To more systematically examine trends in post–hospital discharge death rates, we carried out a series of multivariable-adjusted regression analyses controlling for several potentially confounding demographic, medical history, and clinical factors of prognostic importance ( Table 3 ). The results of these analyses were consistent with our univariate findings, showing marked decreases in 3-month, 1-year, and 2-year postdischarge death rates during the years under study. The risk of dying at 1 and 2 years after being discharged from the hospital, after adjusting for several potentially confounding prognostic factors, decreased considerably between 1975 to 1986 and 1988 to 1995. These trends, however, were no longer statistically significant during the most recent 10-year period under study.
