Although medical co-morbidities commonly affect clinical outcomes after acute myocardial infarction (AMI), current performance measures of AMI quality focus exclusively on the management of the AMI itself. However, patients with AMIs frequently present with other co-morbidities, such as diabetes mellitus (DM), that also warrant assessment and management. To date, the quality of DM evaluation in patients presenting with AMIs has not been described. From January 2003 to June 2004, the Prospective Registry Evaluating Myocardial Infarction Patients: Events and Recovery–Quality Improvement (PREMIER-QI) enrolled 3,953 patients with AMIs at 19 centers in the United States. The frequency of glycosylated hemoglobin (HbA 1c ) assessment, either during the hospitalization or documented in the chart from the preceding 3 months, was prospectively evaluated. Among 1,168 patients with AMIs with preexisting DM, only 47% had recent HbA 1c levels available, with marked variability in HbA 1c assessment among hospitals (range 7% to 81%). Among those with available HbA 1c levels, 39% had good control (HbA 1c <7%), 36% had suboptimal control (HbA 1c 7% to 9%), and 25% had poor control (HbA 1c >9%). Patients with suboptimal and poor control were more likely to have their DM treatment intensified than those without HbA 1c assessment (for HbA 1c 7% to 9%, rate ratio 1.38, 95% confidence interval 1.03 to 1.85; for HbA 1c >9%, rate ratio 2.20, 95% confidence interval 1.68 to 2.88). Similarly, patients with DM who had HbA 1c measured were more likely to receive instructions on DM disease management before discharge. In conclusion, the assessment of chronic glycemic control is highly variable among patients with AMIs and DM. Because much of this variability occurs at the hospital level, the evaluation of DM control could represent an additional quality indicator and an opportunity to advance patient-centered AMI care.
Although the prognostic and therapeutic implications of diabetes mellitus (DM) at the time of acute myocardial infarction (AMI) have been well recognized, the assessment of DM control at the time of AMI has generated little attention. Furthermore, although aggressive inpatient treatment of hyperglycemia during AMI hospitalization continues to be controversial, the benefits of chronic glycemic control on the microvascular complications of DM are well established. Given the increasing focus on managing multiple coexisting illnesses affecting cardiovascular patients, the assessment of glycosylated hemoglobin (HbA 1c ) in patients with AMIs with DM could be an important opportunity to improve care for this important subset of patients. In addition, the relation between HbA 1c assessment and medication titration in patients with inadequate DM control remains unclear. To address these issues, we used a multicenter registry to (1) examine the frequency of HbA 1c assessment in patients with AMIs with DM, (2) describe patterns of glycemic control in these patients, and (3) assess the clinical response to elevated HbA 1c levels.
Methods
The Prospective Registry Evaluating Myocardial Infarction Patients: Events and Recovery–Quality Improvement (PREMIER-QI) is an observational registry of consecutive patients hospitalized for AMIs from which detailed clinical data were abstracted on 3,953 patients from January 1, 2003, to June 28, 2004, at 19 centers in the United States. Criteria for inclusion were age ≥18 years, prolonged (>20 minutes) signs or symptoms of myocardial ischemia or ischemic electrocardiographic changes, and biochemical evidence of myocardial necrosis. Patients transferred from other institutions were included only if they were transferred within 24 hours of symptom onset, and patients who developed elevated cardiac enzymes as a complication of elective coronary revascularization were not included. No identifying patient information was collected for this registry. Institutional research board approval was obtained at each participating center.
For the purposes of the present study, only patients with established diagnoses of DM at hospital admission were included. Type 1 and type 2 DM were included because the recommendations for regular monitoring of HbA 1c are the same for the 2 conditions. To avoid confounding associated with small sample sizes, centers with <10 patients with DM were excluded from the analyses. The primary outcomes were HbA 1c assessment and the introduction or intensification of DM therapy by hospital discharge.
Patients were classified as having HbA 1c assessment if HbA 1c was measured during the hospitalization or if the chart documented HbA 1c results <3 months before admission. These data were prospectively collected throughout the study. To define the treating physician’s response to a clinically available measurement of HbA 1c , admitting and discharge medications were compared, and treatment was categorized as increased, unchanged, or decreased. Patients were considered to have increased DM treatment if the doses of oral antihyperglycemic agents were intensified, if a new antihyperglycemic agent was added to the medical regimen, if long-term insulin therapy was initiated, or if the cumulative daily insulin dose was increased by ≥20%. The DM regimen was considered unchanged if no changes were made in antihyperglycemic therapy, if 1 oral medication was changed to a different oral medication, or if the insulin formulation was changed (e.g., neutral protamine Hagedorn to glargine) or the total daily units of insulin varied by <20%. DM therapy was considered decreased if oral agents remained the same but the dose was decreased, if an insulin regimen was changed to oral agents alone, if oral agents or insulin were stopped and not restarted by hospital discharge, or if the total daily insulin dose was lowered by ≥20%.
Patients with DM were dichotomized into those whose glycemic control was assessed (i.e., HbA 1c levels available) and those who did not have recent HbA 1c levels reported. We then compared patient demographics, clinical characteristics, admission glucose concentrations, cardiac treatments, and diabetic discharge instructions of patients who had HbA 1c levels assessed and those who did not. Between-group differences were assessed using chi-square tests for categorical variables and Student’s t tests for continuous variables.
Variation in HbA 1c assessment across hospitals was examined by crude rates and using estimated random effects from a hierarchical regression model. To better quantify this variation, we calculated the median rate ratio (MRR) after adjusting for patient characteristics. The MRR describes the likelihood that a single patient, if presenting to 2 random hospitals in our study, would have had an HbA 1c assessment at 1 of the hospitals compared with the other. The MRR was adjusted for individual patient demographics (age, gender, race, body mass index, and insurance status), medical history (hypertension, dyslipidemia, previous coronary disease, heart failure, previous stroke, renal failure), and clinical status at presentation (ST elevation or non–ST elevation AMI, left ventricular systolic function, and admission glucose).
To evaluate the consequences of HbA 1c assessment on subsequent DM management, we examined the change in medication regimen and the provision of discharge instructions between those who did and did not have HbA 1c assessed. Among patients who had recent assessment, HbA 1c levels were categorized as good control (<7%, the American Diabetes Association recommendation at the time of this study), suboptimal control (HbA 1c 7% to 9%), or poor control (HbA 1c >9%). Rate ratios (vs the reference group of patients without HbA 1c assessed) were estimated using modified Poisson regression models adjusting for hospital.
Missing values were present in <1% of the data; these were imputed using expectation maximization methods (which estimate conditional means for missing values given observed values of the other covariates) to allow all patients to be retained in the analysis. A p value <0.05 was considered statistically significant. All analyses were performed using SAS version 9.1 (SAS Institute Inc., Cary, North Carolina) and R version 2.7.2 (R Foundation for Statistical Computing, Vienna, Austria).
Results
Of 3,953 patients enrolled in PREMIER-QI, 1,201 (30.4%) had known DM at admission. After excluding 5 centers with low enrollment of patients with DM (n = 33 patients), the final analytic cohort consisted of 1,168 patients from 14 enrolling hospitals (range 22 to 172 from each hospital). The mean age was 64 ± 13 years, 702 (60.1%) were men, and 716 (61.7%) were Caucasian. Only 547 patients with DM (46.8%) had recent HbA 1c levels available to treating physicians during their AMI hospitalizations.
Patient characteristics, stratified by whether HbA 1c was assessed, are listed in Table 1 . Patients who underwent HbA 1c assessment were slightly younger (mean age 63 vs 65 years, p <0.001) and less likely to be Caucasian (56% vs 67%, p <0.001), but otherwise there were no significant differences in gender, health insurance status, body mass index, cardiovascular history, or clinical presentation of AMI. Patients who had HbA 1c measured had higher admission glucose levels than those who were not assessed (225 ± 126 vs 207 ± 114 mg/dl, p = 0.012). The medical therapy for AMI and multidisciplinary discharge planning are listed in Table 2 . Quality of AMI care, as assessed by the appropriate use of evidence-based medical therapies for AMI, did not differ between those patients with and without HbA 1c assessments. However, intensification of DM medication was more likely when a current HbA 1c level was available (33% vs 26%, p = 0.018). Nonpharmacologic interventions such as dietary counseling (78% vs 63%, p <0.001) and disease management instructions for DM (41% vs 29%, p <0.001) were also more likely to be provided to patients with known HbA 1c levels.