A total of 8,898 residents of the Worcester metropolitan area were hospitalized with an initial AMI during the period under study. Overall, the average age of study patients was approximately 71 years, 48% were women, and 95% were Caucasian.
Incidence Rates of Initial MI
The age-adjusted hospital incidence rates (per 100,000 population) of initial MI’s in greater Worcester residents increased from 277 in 1975 to a peak of 320 in 1981 (). There was a gradual increase in the incidence rates of AMI between 1988 and 2001 after which time these incidence rates declined to 209 in our most recent study year of 2005 (P=0.42 for overall trends) ().
Trends in the incidence rates of initial acute myocardial infarction
Patient Characteristics Associated with Initial AMI
Patients who were admitted to greater Worcester hospitals with an initial AMI during recent, as compared to earlier, study years were significantly older (mean age = 63.5 years in 1975; mean age = 70.8 years in 2005), more likely to be women, to be obese, and to have a prior history of diabetes, hypertension, stroke, or heart failure (). The average hospital stay has declined markedly over time from an average of 17 days in the mid-1970’s to approximately 5 days in 2005. Duration of prehospital delay after the onset of acute coronary symptoms to the seeking of medical care remained essentially unchanged over time ().
Characteristics of Patients With Initial Acute Myocardial Infarction According to Time Period of Hospitalization
During the most recent years under study, hospitalized patients had a higher heart rate and serum creatinine levels at the time of hospital admission compared with earlier study years. Patients hospitalized during the 2000’s had lower initial total serum cholesterol levels than patients hospitalized during earlier study years.
The proportion of patients with a Q-wave MI declined from approximately 70% in 1975 to less than 25% in 2005 (). In 1997, we began collecting information on whether the patient’s ECG showed ST segment elevation changes or otherwise. In 1997, 49.2% of patients were diagnosed with an ST segment elevation AMI; this percentage was 40.0% in 2001 and 36.1% in 2005.
Use of Cardiac Medications and Coronary Interventional Procedures
Marked increases in the use of aspirin, angiotensin converting enzyme inhibitors, beta blockers, and lipid lowering medications were observed during the years under study (). On the other hand, use of thrombolytic therapy has declined markedly during recent years, such that only 1.2% of patients hospitalized in 2005 received thrombolytic therapy. Hospital use of calcium antagonist agents also declined. Use of cardiac catheterization and percutaneous coronary interventions (PCI) has increased markedly over time whereas the use of CABG surgery during hospitalization has increased during the 1990’s and declined in the 2000’s (). Cardiac catheterization, PCI, and CABG surgery were respectively utilized in 68.5%, 53.9%, and 3.7% of patients hospitalized with an initial AMI during 2005 (). (double check)
Use of cardiac medications according to time period of hospitalization
Use of cardiac procedures and coronary reperfusion strategies according to time period of hospitalization
Frequency and Death Rates of Acute Clinical Complications
Patients hospitalized with AMI during the most recent study years were more likely to develop atrial fibrillation compared with patients hospitalized in the early study years (). Patients hospitalized during recent study years were slightly less likely to develop cardiogenic shock with inconsistent trends noted in the occurrence of heart failure. Encouragingly, the hospital CFR’s associated with each of these important clinical complications have declined appreciably over time despite the advanced age and greater prevalence of comorbidities in patients hospitalized with AMI during our most recent study years ().
Risk of Developing Selected Hospital Complications and Hospital Case-Fatality Rates (CFR) in Patients Hospitalized With Initial Acute Myocardial Infarction According to Time Period of Hospitalization
We carried out a series of multivariable adjusted regression analyses for purposes of examining changing trends in the risk of, and mortality associated with, these hospital outcomes while controlling for several demographic and clinical factors of prognostic importance (). The results of these analyses showed inconsistent trends in the risk of developing atrial fibrillation, heart failure, and cardiogenic shock over the period under study. Declines over time in the hospital death rates associated with each of these clinical complications were observed.
Declines in hospital death rates occurred over the period under study. In 1975, the hospital CFR was 19.1% compared to 9.5% in 2005 (). Since the average stay for patients hospitalized with AMI has declined markedly over time, we also examined changing trends in 30 day CFR’s from the time of hospital admission during the years under study. The results of this analysis confirmed previously observed declines in hospital death rates associated with AMI. In 1975/78, the 30 day death rates after hospital admission were 17.6% while these death rates were 11.9% in 2003/05.