Trends for First-Time Hospitalization for AMI
Trends for First-Time Hospitalization for AMI
This was a population-based cohort study of all patients with a first episode of acute ST-segment (STEMI)/non–ST-segment elevation myocardial infarction (n-STEMI) hospitalized in all hospitals of the Emilia-Romagna region of Italy (approximately 4.5 million inhabitants) during the period January 1, 2002, to December 31, 2009. Patients in the Emilia-Romagna Region have universal access to hospital care, physicians' services, and prescription drug coverage. Furthermore, in 2003, the Health Care Agency of the Emilia-Romagna region promoted the development of a territorial network for the treatment of STEMI. The regional project (PRIMA-RER) had to be gradually implemented at a provincial level (9 provinces) through the definition of new diagnostic and therapeutic pathways. The realization of the project was delegated to provincial committees of experts composed of cardiologists and emergency medical system operators and was led by the Regional Cardiology Committee that was a task force composed of cardiologists and health administrators.
During the period January 2002 to December 2009, we identified hospitalizations with a primary or secondary discharge diagnosis of AMI based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM, 2002), codes 410.x1 from a regional database that provides medical records for all patients discharged from both public and private hospitals. Codes 410.71 and 410.91 classified patients with n-STEMI, whereas the remaining codes (410.11–410.61 and 410.81) classified patients with STEMI.
From a total cohort of 74,067 patients with AMI hospitalized during the study period, we excluded from the analysis (1) patients resident outside the Emilia-Romagna region during the AMI episode or migrated during follow-up (4,958), (2) patients with a prior admission for AMI or HF in the last 3 years (7,701), and (3) patients discharged within 1 day of hospital admission (735). The remaining 60,673 (81.9%) patients who fully satisfied the eligibility criteria represented the study population.
The Emilia-Romagna Regional Health Agency, which has direct access to the Emilia-Romagna Public Drug database, examined computerized prescription records that contain comprehensive data of prescription medications dispensed to Emilia-Romagna residents after hospital discharge (territorial pharmacies). Prescriptions filled for acetylsalicylic acid [anatomical therapeutic chemical classification system (ATC) code B01AC06], vitamin K antagonists (ATC class B01AA), β-blockers (ATC class C07), statins (ATC class C10AA), agents acting on the renin-angiotensin system (ATC class C09), and diuretics (ATC class C03) were evaluated at any time in the first 12 months after hospital discharge.
Cardiovascular mortality was defined as mortality due to cardiac (ICD-9-CM codes: 410–414, 425–429; ICD-10-CM codes: I20-I25, I39-I52), cerebrovascular (ICD-9-CM codes: 430–438; ICD-10-CM codes: I60-I69), or unknown disease (ICD-9-CM codes: 798.1, 798.2, 798.9; ICD-10-CM codes: R96-R99). In-hospital HF was defined as the development of HF during the hospitalization of the AMI index. One-year postdischarge HF was defined as a further hospitalization for HF in patients that survived the AMI index without HF. Episodes of HF were identified using HF codes (ICD-9-CM: 428.xx, 785.51). We defined 1-year postdischarge re-AMI hospitalization as rehospitalization for n-STEMI or STEMI in patients who survived the AMI index episode. We identified such hospital readmissions using AMI ICD-9-CM codes (primary diagnosis). In-hospital and postdischarge bleedings were identified using the most frequently adopted ICD-9-CM bleeding codes (primary or secondary diagnosis) for (1) gastrointestinal bleeding and retroperitoneal bleeding, (2) intracranial bleeding, (3) urinary tract bleeding, (4) airway bleeding, (5) intraocular bleeding, (6) intraarticular bleeding, (7) blood transfusion, (8) arterial or venous surgical vascular suture, and (9) hemopericardium.
Postdischarge bleeding was defined as a further hospitalization for bleeding in patients that survived the AMI index without bleeding.
Comorbidities were ascertained by means of ICD-9-CM codes from codiagnosis at discharge and from in-hospital admissions within 3 years before the AMI episode.
We obtained information on all-cause and cardiovascular mortality, rehospitalizations for HF, rehospitalizations for bleeding, and rehospitalizations for AMI up to the end of 2009 from the Emilia-Romagna Regional Health Agency through access to municipal registries and hospital discharge records. This warranted a complete follow-up for all patients resident in the region, including all out-of-hospital deaths.
Data were collected from January 1, 2002, through December 31, 2009. Data were summarized as frequencies and percentages for categorical variables. Continuous variables were reported as medians and 25th to 75th percentiles. The period of patient enrolment was divided into 8 periods of 12 months each. The double-sided Cochran-Armitage test for trend was used to evaluate time trends. Adjusted hazard ratio (HR) and 95% CI of the primary and secondary outcomes of the different periods were measured by adjusting for differences in baseline characteristics using multivariate weighted Cox regression analysis. Variables in the models were age, gender, type of AMI, hypertension, diabetes, dyslipidemia, atrial fibrillation, valvular heart disease, neoplasm, chronic obstructive pulmonary disease, chronic renal disease, chronic liver disease, peripheral arterial disease, and cerebrovascular disease.
To evaluate temporal changes in outcome measures, crude and adjusted HR and 95% CI of the primary and secondary outcome measures of the years 2003, 2004, 2005, 2006, 2007, 2008, and 2009 were compared with those of the 2002 period (first period of enrolment).
All statistical tests were 2-sided (P < .05 was considered to be significant). All analyses were performed with SAS 9.1 system (SAS Institute, Cary, NC) and R Statistical Software, version 2.10.0,(Copyright 2009, The R Foundation for Statistical Computing, Wien, Austria).
No extramural funding was used to support this work. The authors are solely responsible for the design and execution of this study, all study analyses, and the drafting and editing of the paper and its final contents.
Methods
Settings and Study Population
This was a population-based cohort study of all patients with a first episode of acute ST-segment (STEMI)/non–ST-segment elevation myocardial infarction (n-STEMI) hospitalized in all hospitals of the Emilia-Romagna region of Italy (approximately 4.5 million inhabitants) during the period January 1, 2002, to December 31, 2009. Patients in the Emilia-Romagna Region have universal access to hospital care, physicians' services, and prescription drug coverage. Furthermore, in 2003, the Health Care Agency of the Emilia-Romagna region promoted the development of a territorial network for the treatment of STEMI. The regional project (PRIMA-RER) had to be gradually implemented at a provincial level (9 provinces) through the definition of new diagnostic and therapeutic pathways. The realization of the project was delegated to provincial committees of experts composed of cardiologists and emergency medical system operators and was led by the Regional Cardiology Committee that was a task force composed of cardiologists and health administrators.
During the period January 2002 to December 2009, we identified hospitalizations with a primary or secondary discharge diagnosis of AMI based on the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM, 2002), codes 410.x1 from a regional database that provides medical records for all patients discharged from both public and private hospitals. Codes 410.71 and 410.91 classified patients with n-STEMI, whereas the remaining codes (410.11–410.61 and 410.81) classified patients with STEMI.
From a total cohort of 74,067 patients with AMI hospitalized during the study period, we excluded from the analysis (1) patients resident outside the Emilia-Romagna region during the AMI episode or migrated during follow-up (4,958), (2) patients with a prior admission for AMI or HF in the last 3 years (7,701), and (3) patients discharged within 1 day of hospital admission (735). The remaining 60,673 (81.9%) patients who fully satisfied the eligibility criteria represented the study population.
Concomitant Medical Therapy
The Emilia-Romagna Regional Health Agency, which has direct access to the Emilia-Romagna Public Drug database, examined computerized prescription records that contain comprehensive data of prescription medications dispensed to Emilia-Romagna residents after hospital discharge (territorial pharmacies). Prescriptions filled for acetylsalicylic acid [anatomical therapeutic chemical classification system (ATC) code B01AC06], vitamin K antagonists (ATC class B01AA), β-blockers (ATC class C07), statins (ATC class C10AA), agents acting on the renin-angiotensin system (ATC class C09), and diuretics (ATC class C03) were evaluated at any time in the first 12 months after hospital discharge.
Definitions
Cardiovascular mortality was defined as mortality due to cardiac (ICD-9-CM codes: 410–414, 425–429; ICD-10-CM codes: I20-I25, I39-I52), cerebrovascular (ICD-9-CM codes: 430–438; ICD-10-CM codes: I60-I69), or unknown disease (ICD-9-CM codes: 798.1, 798.2, 798.9; ICD-10-CM codes: R96-R99). In-hospital HF was defined as the development of HF during the hospitalization of the AMI index. One-year postdischarge HF was defined as a further hospitalization for HF in patients that survived the AMI index without HF. Episodes of HF were identified using HF codes (ICD-9-CM: 428.xx, 785.51). We defined 1-year postdischarge re-AMI hospitalization as rehospitalization for n-STEMI or STEMI in patients who survived the AMI index episode. We identified such hospital readmissions using AMI ICD-9-CM codes (primary diagnosis). In-hospital and postdischarge bleedings were identified using the most frequently adopted ICD-9-CM bleeding codes (primary or secondary diagnosis) for (1) gastrointestinal bleeding and retroperitoneal bleeding, (2) intracranial bleeding, (3) urinary tract bleeding, (4) airway bleeding, (5) intraocular bleeding, (6) intraarticular bleeding, (7) blood transfusion, (8) arterial or venous surgical vascular suture, and (9) hemopericardium.
Postdischarge bleeding was defined as a further hospitalization for bleeding in patients that survived the AMI index without bleeding.
Comorbidities were ascertained by means of ICD-9-CM codes from codiagnosis at discharge and from in-hospital admissions within 3 years before the AMI episode.
Clinical Outcome Data
We obtained information on all-cause and cardiovascular mortality, rehospitalizations for HF, rehospitalizations for bleeding, and rehospitalizations for AMI up to the end of 2009 from the Emilia-Romagna Regional Health Agency through access to municipal registries and hospital discharge records. This warranted a complete follow-up for all patients resident in the region, including all out-of-hospital deaths.
Statistical Analysis
Data were collected from January 1, 2002, through December 31, 2009. Data were summarized as frequencies and percentages for categorical variables. Continuous variables were reported as medians and 25th to 75th percentiles. The period of patient enrolment was divided into 8 periods of 12 months each. The double-sided Cochran-Armitage test for trend was used to evaluate time trends. Adjusted hazard ratio (HR) and 95% CI of the primary and secondary outcomes of the different periods were measured by adjusting for differences in baseline characteristics using multivariate weighted Cox regression analysis. Variables in the models were age, gender, type of AMI, hypertension, diabetes, dyslipidemia, atrial fibrillation, valvular heart disease, neoplasm, chronic obstructive pulmonary disease, chronic renal disease, chronic liver disease, peripheral arterial disease, and cerebrovascular disease.
To evaluate temporal changes in outcome measures, crude and adjusted HR and 95% CI of the primary and secondary outcome measures of the years 2003, 2004, 2005, 2006, 2007, 2008, and 2009 were compared with those of the 2002 period (first period of enrolment).
All statistical tests were 2-sided (P < .05 was considered to be significant). All analyses were performed with SAS 9.1 system (SAS Institute, Cary, NC) and R Statistical Software, version 2.10.0,(Copyright 2009, The R Foundation for Statistical Computing, Wien, Austria).
No extramural funding was used to support this work. The authors are solely responsible for the design and execution of this study, all study analyses, and the drafting and editing of the paper and its final contents.
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